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nuckollsr(at)cox.net
Guest

Posted: Tue Apr 04, 2006 11:03 am Post subject: Why use starter contactor?

At 11:18 AM 1/27/2006 -0600, you wrote:



 	  Quote: 	
		  

<BigD(at)DaveMorris.com>



At 09:59 AM 1/27/2006, you wrote:

 >

 >If you

 >get in a crash and the engine is ripped off, I don't think the battery

 >cable will be you only problem. George

 >



It may not be, but it could mean the difference between walking away doused

in gasoline, and walking away on fire, hoping somebody can get to you

quickly enough to put out the flames.



This happened to a friend of mine who would have walked away from a crash

if it had not been for that one little spark.  I'm putting a starter

contactor on the firewall to absolutely shut off any possibility of the fat

wire going to the starter chafing against baffling material or anything

else in the event the engine decides to leave its normal upright, and

locked position.



What's a few bucks, guys?  My experience with this friend of mine has made

me a believer in steel braided fuel hose, Earl's fittings, Nomex clothing,

and a lot of other things that may cost a few dollars extra, but could

avoid years of skin graft surgery.


	


    The external contactor has nothing to do with crash safety.



    We recommended an external starter contactor for use with

    ALL starters having modern automotive style contactor/engagement

    solenoids. This policy was adopted by B&C from day-one in spite

    of the fact that their new light-weight offering already had

    a "useful" contactor built in. The reasoning was based on starter's

    need for a low impedance path between battery and the solenoid winding

    for energetic engagement of pinion gear and max performance closure

    of the built in contactor mechanism. The reason for this is explained

    at:



http://aeroelectric.com/articles/strtctr.pdf



    The external contactor recommended is MUCH less abusive of the starter

    switch. Failure of many starter manufacturers to recognize this stress

    is root cause of premature failures of the ACS off-l-r-both-start

    ignition switch of some years back when an AD was issued to replenish

    the start switch contacts within the switch and to add a diode across

    the switch to mitigate inductive effects for breaking the circuit.

    The original AD placed the diode in the wrong place as I've described

    in . . .



http://aeroelectric.com/articles/spikecatcher.pdf



    A later edition of the AD corrected the error and repositioned the

    diode. The diode only mitigates the switch-break-spike condition,

    not the switch-make-inrush condition. The larger than usual inrush

    is still present and is still a life limiting effect on the ACS or

    any other style switch.



    When PM starters came along, the wiring techniques recommended by

    B&C and the 'Connection were not compatible with starter motors which

    generated strong energies during wind-down and caused undesirable

    delays in pinion gear engagement.



    This is what prompted Figure Z-22 of



http://aeroelectric.com/articles/Rev11/AppZ_R11F.pdf



    where a boost relay is used to relived panel mounted starter switches

    of the stresses cited. Reasoning was that I'd much rather replace a

    $5 relay under the cowl than ANY switch on the panel, especially

    an off-l-r-both-start keyswitch.



    I'll stand by the recommendations for wiring as show in either

    Z-22 (boost relay) or any other Z-figure where and external

    contactor is shown. It's a system performance, service life

    and cost of ownership consideration.



------------------------------



    Here's an excerpt from an earlier post . . .



I am designing my electrical system very similar to Z-11 with the exception

of the essential bus and a keyed starter. My new Lycoming engine came

with an SkyTec starter so I assume I'll need to use a relay as shown in

Z-14. Does this mean I don't need a starter contactor? Does this relay

replace the contactor or is it additional to it? Thanks



Matt



     A problem arises when the starter utilizes a permanent

     magnet motor. These motors are also efficient generators

     During spin-down of the motor after the starter

     is de-energized, the motor puts out a substantial amount

     of power sufficient to KEEP the pinion gear solenoid

     ENGAGED for several seconds after you release the pushbutton.



     The technique described in our wiring diagrams was

     developed as a compromise between maintaining good

     starter solenoid/contactor performance with a variety

     of starter switches.



     Problems with the philosophy didn't arise until the

     permanent magnet motor showed up. Again, we sought

     a solution that maintained performance of the starter's

     built in solenoid/contactor system that did not

     transfer the system's unique loads to the circuitry

     that controls the starter. Hence, the "boost" relay

     described in Figure Z-22.



     One COULD choose to use the boost relay with ANY

     of the modern, lightweight starters that feature

     electro-mechanically engaged pinion gears. This

     would move the ideal alternator b-lead feedpoint

     from a contactor on the firewall down to the

     main power terminal of the starter solenoid/

     contactor assembly.



-----------------------------------------

    Bob . . .

gmcjetpilot(at)yahoo.com
Guest

Posted: Thu Apr 06, 2006 4:58 am Post subject: Why use starter contactor?

 	  Quote: 	
		  From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>

   
	


  >"The external contactor has nothing to do with 

 	  Quote: 	
		  crash safety."

   
	


  Bob, this was posted back in January. You must be bored. 

   

  First, no one said the crash safety was the ONLY  

reason for having an extra starter contactor/relay 

on the firewall. However its clearly a concern for 

many people. I know because I asked. Personally 

  I don't think its an issue but understand and respect 

  those who do think its a concern. 

   

  From the electrical design standpoint, everyone 

  understands that the possible 30 amp inrush 

current (6 amp continuous) requires a switch capable 

of this. PERIOD, END-O-STORY. Put a 30 amp 

  push button switch on. Done.

   

  A big  750 amp relay is overkill and not needed to 

  switch the starter's on board solenoid. I don't get 

  it. You make it sound as if a big secondary relay 

  is needed. Its like you are selling them or have 

  stock in the relay company or something?

   

  Its a throw back to old Bendix style starters that 

  needed this device. Its time to think out of the box. 

  Consider modern wiring to match a modern starter.

   

  Bob I know you only focus on electrical but I can 

  tell you weight is critical on a planes. You tend to 

  never say NO to a pound of weight if its part of 

  the electrical system.

  

There is a very simple solution; get a momentary 

single pole push button switch with a 30 amp or 

greater capacity as a start switch, which is easy:

   

  A few of many choices:

  http://www.reddenmarine.com/site/new-detail.cfm?id=CHRM626BP

http://www.reddenmarine.com/site/new-detail.cfm?id=CHRM490BP

http://tinyurl.com/g5r3p

  

If you want to use a small tiny (low amp rating) 

  push button and a small light 30-40 amp relay. 

  You can buy them, 5 for $10 on eBay.

http://www.chiefent.com/products/product_details.asp?id=3

  



   

  

 	  Quote: 	
		     We recommended an external starter contactor for 

   use with ALL starters having modern automotive 

   style contactor/engagement solenoids. This 

   POLICY was adopted by B&C from day-one in spite 

   of the fact that their new light-weight offering 

   already had a "useful" contactor built in. The 

   reasoning was based on starter's need for a low 

   impedance path between battery and the solenoid 

   winding for energetic engagement of pinion gear 

   and max performance closure of the built in 

   contactor mechanism. 

   
	


   

  Bob, all the conversation about impedance and key 

switches is faulty logic and clouds the issue. Instead 

of the *Non sequiturs*, get to the facts. Who cares  

  what B&C's policy is. What does that matter? You  

  say it like B&C is the center of the universe.

   

  (non sequiturs =  fallacy in logic, not necessarily wrong 

just conclusion does not follow from the premise.)

  http://en.wikipedia.org/wiki/Non_sequitur_%28logic%29

  



The starter is DESIGNED to work with a starter switch  

  or switch & (small) relay. Its a good alternative, option to  

  a BIG FAT firewall relay of the olden days.

   

  There's no other real good reason for using a 750 amp 

relay, other than you don't want a Hot Bat/Starter feed, 

  which is no big deal (according to Bob).

   

  Just install a $12.00 switch capable of 30 amps or a 

relay of 30-40 amp capacity. Use 14 awg wire. 

   

  The BIG old FAT 750 amp starter relay is an enigma 

  with today's modern starters with solenoids. Now if 

  you are uncomfortable with a hot battery cable, than 

  by all means keep the 750 amp relay and all the extra 

connections, weight, cost, but don't do it for any other 

reason than you don't like the hot Bat / Starter feed. 

  Start switches (+30 amp) are cheap and easy to find.

   

  

  Here are some wiring diagrams that show what I mean.

   

     -No Relay/Contactor wiring:

  http://img16.imageshack.us/img16/1963/norelaysalt4qo.jpg

  (optional big fuse shown. I would go the next fuse

  size up, 400 amps, since PM starters can draw over 

  300 amps. Bussmann makes fuses up to 750 amp.) 

   

   

     -Traditional, with both master and starter relay:

http://img116.imageshack.us/img116/3039/altwiring5cm.jpg 

  (Not bad, works, nothing wrong with it, but  two heavy 

  relays, (4) connections, weight and complication. Plus 

  if you ask me they relays are a big "spark" hazzard.)

  

 

  Bob, you talk abut key switches of cars and planes 

  going bad? So what. The whole system needs to be 

  designed to work with these "modern starters". Here 

  is how Toyota (and most car makers) does it:

  http://www.autoshop101.com/forms/h7.pdf

  (Note: Toyota key switch uses a small start relay)

   

   

  You point to some switch failure on a car or key 

  switch as proof of WHAT? Thats silly logic. You 

  make these verbose platitudes as evidence to 

  support your opinion. The solution is easy. 

  You make simple simple simple DC circuits 

  sound so hard. Its a switch and a coil, no biggie.

   

   

  I am ready for Bob to hurl insults at me and tell 

  me how I don't understand and uninformed I am. 

  I would respectfully say Bob's way is fine, but his 

  reasons are obtuse and not relevant. Don't be 

  alarmed at Bob's reply, I am use to it and ignore 

  it. 

   

  Bob is right; I'm wrong. I would never dream of 

  arguing with him, since he has an uncanny way 

  of always being right. I am just saying there is 

  another way to consider.

   

  I don't feel a need to argue and make large  

  stretches of logic and exaggerate to make my 

  point. Take it or leave it. I am not using big  

  separate firewall contactors/relays/solenoids. 

  One $12.00 push switch (start) and a small 

  solid state relay (master relay), replaces over 

  a pound of weight and several large connections.

   

  With the no firewall starter relay the battery cable 

goes direct to the starter, just like a car. No 

extra relays to fail, no extra connections, less 

weight, cost and better reliability. 

   

  Note:

  Bob N is what you call an Expert, so his way is  

  always the best way, of course.

   

  As far as NOT using a big firewall starter relay 

  safety its not issue (according to Bob). 

   

  >"The external contactor has nothing to do with 

 	  Quote: 	
		  crash safety."

   
	


  I agree with the Expert.

   

  Using a quality 2 awg Bat to starter cable/wire, 

  well routed, well supported and well protected, the 

  chance of sparks is small. 

   

  However each to their own. 

   

   

  BTW 

  With a HOT Bat/starter feed, the chance of it 

  causing a spark is nill. Also with the optional 

  fuse its protect it from hard dead short, but the 

  fuse is not needed, just an option.

   

  Think about the firewall relays, with all those 

  BIG  brass jump straps (un-shilded). They are 

  a spark hazard. There  is no fusing between battery 

  and structure. Many people have fuel gascolators 

  and prime lines right next to their firewall relay!  

   



Cheers George

   

   

  DISCLAIMER: All comments are my opinion and 

based on common wiring practices used in millions of 

cars. However I am not an expert, nor have I written 

a book on wiring so please feel free to ignore my advice,  

which is provided for entertainment purposes only. Any 

attempt at using this info otherwise is at your own risk. 

If you agree, disagree or just want to call me names, 

  feel free to write me direct off list. Thanks



		

---------------------------------

nuckollsr(at)cox.net
Guest

Posted: Thu Apr 06, 2006 8:21 am Post subject: Why use starter contactor?

At 05:55 AM 4/6/2006 -0700, you wrote:



 	  Quote: 	
		  



 >From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>



   >"The external contactor has nothing to do with

 >crash safety."



   Bob, this was posted back in January. You must be bored.


	


   If you're going to be a teacher, you have to expect

   and accept the task of covering the same ground

   over and over with every new class. Else why would

   we need teachers? Just hand out text books, conduct

   tests every few weeks and look at all the money

   we would save. No teachers, no classrooms, shucks

   we could get rid of whole universities. What a deal!



 	  Quote: 	
		  



   First, no one said the crash safety was the ONLY

   reason for having an extra starter contactor/relay

   on the firewall. However its clearly a concern for

   many people. I know because I asked. Personally

   I don't think its an issue but understand and respect

   those who do think its a concern.


	


   Never said that. That WAS the rationale for the extra

   contactor when the thread started. You read things

   into people's words that are not there.



 	  Quote: 	
		  

   From the electrical design standpoint, everyone

   understands that the possible 30 amp inrush

current (6 amp continuous) requires a switch capable

of this. PERIOD, END-O-STORY.


	


 	  Quote: 	
		    Put a 30 amp push button switch on. Done.


	


     But suppose the builder wants to use his key-switch?

     How about the guy who wants the starter button

     on his stick grip (that's where many helicopters

     put it)?  I guess one might consider Z-22 as an

     alternative to the extra contactor as I've written

     many times.

 	  Quote: 	
		  

   A big  750 amp relay is overkill and not needed to

   switch the starter's on board solenoid. I don't get

   it. You make it sound as if a big secondary relay

   is needed. Its like you are selling them or have

   stock in the relay company or something?



   Its a throw back to old Bendix style starters that

   needed this device. Its time to think out of the box.

   Consider modern wiring to match a modern starter.


	


    A 30A push button is 'modern'? We had one on our

    Fordson tractor when I was a kid . . . Cars have

    migrated to Z-22 like features. We airplane designers

    can do it too.



 	  Quote: 	
		  

   Bob I know you only focus on electrical but I can

   tell you weight is critical on a planes. You tend to

   never say NO to a pound of weight if its part of

   the electrical system.


	


    That's not true. I've never tossed weight out of

    the mix of ingredients for design goals. But

    consider this. 20 years ago OBAM aircraft were

    bolting pig starters, rino alternators and big-dog

    flooded batteries into their airplanes but getting

    the same fat grins on their faces the first time

    their projects broke ground.



    Now we have alternatives that have reduced empty

    weights of the same airplanes by as much as 30

    pounds with improved performance. It's all a part of design

    goals. If you worked for Burt Rutan, he might just

    have you just hang two wires out to touch together

    to get the engine started.  His empty weight had

    a 6x multiplier on it for gross weight at takeoff

    for going around the world.



    I've suggested welding cable in lieu of 22759

    as low cost and a joy to work with but at some

    sacrifice of the 30# savings cited. I've suggested

    that one might consider rotating a 15# main battery

    into an aux battery slot for a total weight of 30#

    of batteries as a low cost of ownership alterative

    to one big and one little battery. Your suggestion

    that I'm hard over about squandering that 30# savings

    is false on the face of it.



 	  Quote: 	
		  

There is a very simple solution; get a momentary

single pole push button switch with a 30 amp or

greater capacity as a start switch, which is easy:



   A few of many choices:

   http://www.reddenmarine.com/site/new-detail.cfm?id=CHRM626BP

http://www.reddenmarine.com/site/new-detail.cfm?id=CHRM490BP

http://tinyurl.com/g5r3p



If you want to use a small tiny (low amp rating)

   push button and a small light 30-40 amp relay.

   You can buy them, 5 for $10 on eBay.

http://www.chiefent.com/products/product_details.asp?id=3

 >   We recommended an external starter contactor for

 >   use with ALL starters having modern automotive

 >   style contactor/engagement solenoids. This

 >   POLICY was adopted by B&C from day-one in spite

 >   of the fact that their new light-weight offering

 >   already had a "useful" contactor built in. The

 >   reasoning was based on starter's need for a low

 >   impedance path between battery and the solenoid

 >   winding for energetic engagement of pinion gear

 >   and max performance closure of the built in

 >   contactor mechanism.

   Bob, all the conversation about impedance and key

   switches is faulty logic and clouds the issue. Instead

   of the *Non sequiturs*, get to the facts. Who cares

   what B&C's policy is. What does that matter? You

   say it like B&C is the center of the universe.


	


    I cite B&C because it's the venue under which

    I gained my earliest experiences with the OBAM

    aircraft industry. I've often cited Electromech

    too because it was my university of hard knocks

    in the certified world. George, you read far too

    much into what I say. If it distresses you so much

    to have me mention my various employers, I'll try to

    avoid the practice.



    You've acknowledged the starter control loop

    impedance issue by your own recommendation of

    a 14AWG wire . . . how was my citation of the

    concern "faulty" or an obscuration of the

    facts?



 	  Quote: 	
		  

   (non sequiturs =  fallacy in logic, not necessarily wrong

   just conclusion does not follow from the premise.)

   http://en.wikipedia.org/wiki/Non_sequitur_%28logic%29

   The starter is DESIGNED to work with a starter switch

   or switch & (small) relay. Its a good alternative, option to

   a BIG FAT firewall relay of the olden days.


	


    Yeah, that was the DESIRE of the designers but after

    a few years in the field, many of the automobiles

    that incorporated the new two-stage contactors

    were burning up starter switch contacts just as

    described in the AD against the ACS key-switch.

    The start switch wasn't going to change so they

    did exactly what's described in Z-22 and added

    the relay.



 	  Quote: 	
		  

   There's no other real good reason for using a 750 amp

   relay, other than you don't want a Hot Bat/Starter feed,

   which is no big deal (according to Bob).


	


   Is it a 'big deal'? How? The battery contactor is

   tasked with making the airplane max-cold in a pre-

   crash condition. I've never even considered making

   the starter feed a component of crash safety analysis.

   It's truly not a big deal but not because of anything

   I said about it. It's the WAY THINGS ARE in airplanes

   because they have battery master contactors.



   Some folks on the List have advocated wiring

   airplanes just like cars and dumping the battery

   master contactor idea completely . . . don't recall

   now who was championing that architecture. That

   idea WOULD raise new concerns for configuring an

   electrical system for landing on unfriendly terrain.

 	  Quote: 	
		  

   Just install a $12.00 switch capable of 30 amps or a

   relay of 30-40 amp capacity. Use 14 awg wire.



   The BIG old FAT 750 amp starter relay is an enigma

   with today's modern starters with solenoids. Now if

   you are uncomfortable with a hot battery cable, than

   by all means keep the 750 amp relay and all the extra

   connections, weight, cost, but don't do it for any other

   reason than you don't like the hot Bat / Starter feed.

   Start switches (+30 amp) are cheap and easy to find.

   Here are some wiring diagrams that show what I mean.



      -No Relay/Contactor wiring:

   http://img16.imageshack.us/img16/1963/norelaysalt4qo.jpg

   (optional big fuse shown. I would go the next fuse

   size up, 400 amps, since PM starters can draw over

   300 amps. Bussmann makes fuses up to 750 amp.)


	


    Interesting. Fusing the starter feed line is a new

    concept for light aircraft. I've never seen this done before.

    Can you elaborate on the supporting simple-ideas that

    support this feature? What new hazards have been deduced

    to suggest this ADDED WEIGHT and cost is a useful

    thing to do?

 	  Quote: 	
		  

      -Traditional, with both master and starter relay:

http://img116.imageshack.us/img116/3039/altwiring5cm.jpg

   (Not bad, works, nothing wrong with it, but  two heavy

   relays, (4) connections, weight and complication. Plus

   if you ask me they relays are a big "spark" hazzard.)


	


     Hmmm . . . explosion hazard. That's a new one. Perhaps

     we should consider flame arresters on our  exhaust

     stacks? How about the contactor built into the starter

     itself? You know those brushes in the starter really

     spark good too. Perhaps some beads of RTV around

     all the seams for DIY hermetic sealing? May we assume

     that both WEIGHT and SPARKS are now decision drivers?

 	  Quote: 	
		  



   Bob, you talk abut key switches of cars and planes

   going bad? So what. The whole system needs to be

   designed to work with these "modern starters". Here

   is how Toyota (and most car makers) does it:

   http://www.autoshop101.com/forms/h7.pdf

   (Note: Toyota key switch uses a small start relay)


	


     Where have I argued with that? George, the 'Connection

     is loaded with alternatives. You've painted my words

     as if I'm trying to drive folks toward singular

     goals. If that were true, the 'Connection could be

     replaced with a single drawing, a bill of materials

     and I could rant about how folks are not following

     MY recommendations by not using MY design. The 'Connection

     is a shopping mall of designs. As a teacher I'm obligated to

     consider every alternative that comes to light

     and explain the simple-ideas that help a builder

     choose the most attractive direction that fits

     his/her desires and mission.



 	  Quote: 	
		  



   You point to some switch failure on a car or key

   switch as proof of WHAT?


	


    Yes, we know sir. In Failure Mode Effects Analysis

    according to George, failures of parts are not proof

    of anything. You've said that puffed up batteries,

    smoked radios and burned wires are not good indicators

    of a runaway alternator - these are all 'unsubstantiated'

    stories. Stories cited only to support my wild-eyed notions

    that no piece of electronics is perfect and that some

    items hold the keys to severe consequences worthy of

    consideration in the FMEA. I must continue to beg your

    indulgence for my alternate reality.



 	  Quote: 	
		    Thats silly logic.


	


     . . . hmmmm . . . should I be insulted here?

    Was that intended to be an insult or was it

    just a considered observation? Let's see . . . what

    adjective might I use to describe your position

    on OV failures in the field that won't insult you.

    I'll have to think about it.



 	  Quote: 	
		    You make these verbose platitudes as evidence to

   support your opinion. The solution is easy.

   You make simple simple simple DC circuits

   sound so hard. Its a switch and a coil, no biggie.

   I am ready for Bob to hurl insults at me and tell

   me how I don't understand and uninformed I am.


	


    Please cite any insult I've hurled at you or

    anyone else . . .



 	  Quote: 	
		     I would respectfully say Bob's way is fine, but his

   reasons are obtuse and not relevant. Don't be

   alarmed at Bob's reply, I am use to it and ignore

   it.


	


    George, allow me to be really alarming here and suggest

    that you've accurately described an alternative design

    goal that's been illustrated and explained in my writings

    for years.



 	  Quote: 	
		  

   Bob is right; I'm wrong. I would never dream of

   arguing with him, since he has an uncanny way

   of always being right. I am just saying there is

   another way to consider.



   I don't feel a need to argue and make large

   stretches of logic and exaggerate to make my

   point. Take it or leave it. I am not using big

   separate firewall contactors/relays/solenoids.

   One $12.00 push switch (start) and a small

   solid state relay (master relay), replaces over

   a pound of weight and several large connections.



   With the no firewall starter relay the battery cable

goes direct to the starter, just like a car. No

extra relays to fail, no extra connections, less

weight, cost and better reliability.



   Note:

   Bob N is what you call an Expert, so his way is

   always the best way, of course.


	


    Are you being insulting here George? I can't tell.

    Are we being teachers here or is this a script

    for a Mythbusters show?



 	  Quote: 	
		  

   As far as NOT using a big firewall starter relay

   safety its not issue (according to Bob).



 >"The external contactor has nothing to do with

 >crash safety."



   I agree with the Expert.



   Using a quality 2 awg Bat to starter cable/wire,

   well routed, well supported and well protected, the

   chance of sparks is small.



   However each to their own.


	


    "To each their own?" I thought the thrust of

    your missive was to explain the silliness of my

    logic and that a savings of under a pound of weight

    is an overriding concern. However, you seem to suggest

    that when all is said, what anyone does is a matter of

    comfort. Help us understand your recommendations.



 	  Quote: 	
		  

   BTW With a HOT Bat/starter feed, the chance of it

   causing a spark is nill. Also with the optional

   fuse its protect it from hard dead short, but the

   fuse is not needed, just an option.


	


    Under what design considerations would you say the

    fuse is a good option? Are there other locations

    where adding some fuses is a good or better option?

    If you're going to toss that idea on the table sir,

    please be a teacher and explain when and why it makes

    sense and what hazard condition is being mitigated.



    Have you ever seen how much "sparking" can be generated

    downstream of a 300A current limiter without opening

    the limiter? I'm having trouble understanding when

    the 'option' would be deemed useful.



 	  Quote: 	
		  

   Think about the firewall relays, with all those

   BIG  brass jump straps (un-shilded). They are

   a spark hazard. There  is no fusing between battery

   and structure. Many people have fuel gascolators

   and prime lines right next to their firewall relay!


	


    Let us 'think' also that we sit between at least two tanks

    filled with gallons of fuel plumbed with dozens of fittings

    and moved with pumps that put lots of pressure on

    a flammable liquid. May I suggest these are part-n-parcel

    of systems design and integration were selection of materials

    and techniques reduce risks?



    You've accused me of being trivial with respect to starter

    switch selection. Please consider that my suggestions

    allow the design goal of using of ANY starter switch (key,

    toggle, push-button, etc.).



    I DO confess to adding between 0.2 and 0.9 pounds to the airplane

    depending on whether the builder uses Z-22 or the external

    contactor. But if you're going to add the ANL limiter for

    about 0.5 pounds more, perhaps the drive to save weight by not

    having an external contactor becomes even less significant.



    You have tossed lack of explosion proofing and new current limiters

    into the discussion. Are you suggesting these are useful points of

    consideration for our airplane building brothers?

 	  Quote: 	
		  Cheers George


	


    Cheers to you too George, and please know that no

    words I've written were intended to insult or demean.

    We're only trying to understand . . . I've explained the

    rationale behind the external contactor recommendation

    and 'fessed up to the added weight for this and MANY

    other system features we've discussed for years.



    The best understanding I have of your present missive is that

    I'm perhaps 0.4 pounds heavier than your recommendations

    when the builder opts for the ANL limiter.



    I will suggest that your design recommendation for

    a fat starter push button is restrictive compared to what

    I've suggested in the 'Connection and here on the List.

    However, if the builder is shaving ounces and buys into the

    appropriately sized, independent starter button, then your

    recommendations are spot on. But I'll have to think about those

    sparks some more.



    Hmmmm . . . for ounce shavers, keep in mind that moving an

    under-the-cowl starter contactor from firewall out to the

    starter will, on airplanes with rear mounted batteries,

    add ounces of wire for the bus feeders that used to

    tie onto the firewall starter contactor. Gee, every decision

    has so many consequences to consider! Kinda makes one's head

    feel tight.



    Bob . . .

rvbuilder(at)sausen.net
Guest

Posted: Thu Apr 06, 2006 12:35 pm Post subject: Why use starter contactor?

Outside of the usual bickering between you two, I have to say that George has added one of the most useful pieces of information I have personally seen in weeks, even if Bob did glaze over it below.  The idea of replacing the big and heavy starter relay with a very reliable Bosch style for 1/5th the price and weight is an excellent idea when going with a starter that already has a solenoid to handle the heavy lifting.



  I'm a simple guy that doesn't need a Unified Theory to understand risks and benefits.  So let's keep the rhetoric out guys, the explanations concise and straight forward, and I think everyone will benefit all the more.



Michael Sausen

-10 #352 Fuselage

Do not archive



--

rdunhamtn(at)hotmail.com
Guest

Posted: Thu Apr 06, 2006 2:34 pm Post subject: Why use starter contactor?

OK George,



It's plain to see you're slipping back into a manic phase.



Call your shrink.

Get back on the Lithium.

Take a chill pill before you get REALLY verbose.



You're OK.

Bob's OK.

We're ALL OKAY!



Cheers )



Rodney



and pleeeeease, DO NOT ARCHIVE

klehman(at)albedo.net
Guest

Posted: Thu Apr 06, 2006 2:58 pm Post subject: Why use starter contactor?

Possibly because the pros and cons of that have been discussed at length 

several times here Michael. Several folks related experiences with stuck 

on automotive starters when I've brought up the subject. Nevertheless I 

went with a 25 amp rated marine key starter switch which I believe is 

less likely to cause problems than an additional small relay. A cheap 40 

amp relay is not imune from sticking either in this kind of service. Got 

to admit though my key switch will be a bear to change out compared to a 

contactor or a small relay when/if it ever fails, and it cost more than 

either.

Ken



RV Builder (Michael Sausen) wrote:



 	  Quote: 	
		  



 Outside of the usual bickering between you two, I have to say that George has added one of the most useful pieces of information I have personally seen in weeks, even if Bob did glaze over it below.  The idea of replacing the big and heavy starter relay with a very reliable Bosch style for 1/5th the price and weight is an excellent idea when going with a starter that already has a solenoid to handle the heavy lifting.

gmcjetpilot(at)yahoo.com
Guest

Posted: Fri Apr 07, 2006 7:42 am Post subject: Why use starter contactor?

 	  Quote: 	
		  From:  Ken <klehman(at)albedo.net> 

Subject:  Re: Why use starter contactor?       

      >Possibly because the pros and cons of that have been discussed at length 

      >several times here Michael. Several folks related experiences with stuck 

      >on automotive starters when I've brought up the subject. Nevertheless I 

      >went with a 25 amp rated marine key starter switch which I believe is 

      >less likely to cause problems than an additional small relay. A cheap 40 

      >amp relay is not immune from sticking either in this kind of service. Got 

      >to admit though my key switch will be a bear to change out compared to a 

      >contactor or a small relay when/if it ever fails, and it cost more than 

      >either.

      >Ken

  Ken: 

  Thanks for the thoughtful reply. 

  My postulation is if you use a BIG FAT start button and no extra firewall relay/

solenoids/contactors, chance of starter run-on / spontaneous engagement is nil. 

Has this happened in a car you know of? To the config I suggest in a plane?

  Your comment about *several folks* who claim they had problems is great, but 

with out details its like the OV alternator thing, just rumor or irrelevant. 

  There are reasons a starter can run-on. I suspect you are either talking a 

old Bendix drive starters or OLD firewall Cessna or Piper firewall solenoids, 

which do stick when they get old. Neither apply to our conversation.

  People who switched to new starters have got run-ons because the OLD firewall 

solenoid was retained and stuck; its NOT an issue of the starter itself. 

  This supports my claim that LESS IS MORE. Get rid of that old solenoid and 

get a big 60 amp start button.

  I researched this thoroughly. I talked to SkyTec. The chance of sticking starter 

is next to nothing. I also asked about the no secondary solenoid and guess 

what? They said its made that way and will work fine. Let's say you did get 

a run-on, it would be during start, you would shut down. SkyTec shows how 

to wire a run-on light if you like. Chance of it engaging in flight? never.

  Skytec has more starters flying than anyone. I think they know what's up.

  QUOTE: 

  What about the Bendix?  Maybe it stuck?

**Since Sky-Tec starters do not use mechanical Bendix drives to actuate the 

starter, this is actually nearly impossible for a Sky-Tec starter to keep itself 

engaged with the aircraft ring gear.  Sky-Tec starters are electromechanically 

engaged therefore requiring voltage to engage the starter's drive pinion gear with 

the ring gear.  Without voltage, the pinion simply cannot remain in the flywheel.  

A spring and a helical return will both force the drive pinion back out of the ring 

gear and into the rest position.**

  Ref:  http://www.skytecair.com/Cessna_Solenoids.htm 

  Cessna (mostly) and Piper, apparently have a history of Firewall Solenoids 

sticking, so actually even a factory solenoid (relay) can stick. That is WHY 

I suggest a big OLD fat start button, like a race car. (w/ catch diode of course)

  All the $60,000-$200,000 Luxury and Sport cars are going to no key push 

button start switches.

  Here is some other good info from SkyTec:

  Troubleshooting Diagram: guide to Gen & spacific (to run on) issues:

http://www.skytecair.com/Troubleshooting.htm

  Here is two wiring diagrams from SkyTec:

http://www.skytecair.com/Wiring_diag.htm

  Here is a guide to wiring, with specifics to starters:

http://www.skytecair.com/Wiring_Experimental.pdf

To be fair to Bob, if it ain't broke don't fix it. Nothing WRONG with the 

Z diagram xyz, just suggesting if you want a lean mean electrical system

with more than adequate or even superior reliability and safety, while 

lowering weight and complexity, consider trashing the BIG fw contactor.

  The next step is get rid of the BIG master contactor. You only need a 

  30-60 amp relay if you don't run the starter load through it. 

  Cheers George

---------------------------------

altoq(at)cebridge.net
Guest

Posted: Fri Apr 07, 2006 1:51 pm Post subject: Why use starter contactor?

TWIMC (Which is probaly only me),



(1) Electrial Solenoid engaged starters,as used on Lycoming, Chevrolet,BMW, 

and Porsche, do stick.



(2) Solenoid engaged starters are disengaged by a spring and an over running 

mechanism in the starter gear.



(3) I have personally seen three out of the four named, stick .



(4) They stick and continue to crank the engine, they stick and don't crank 

the engine, and all modes of stick in between.



(5) They stick when they are new or old, clean or dirty but mostly they 

stick because they are misaligned or have not been lubricated.



(6) One of these starters that fail in the "CRANK the engine mode" with the 

+12VDC wired directly to the solenoid has a great big wire as big around as 

your index finger HOT and you can't turn it off.



(7) There are many light weight relays capable of eliminating this problem 

by attaching the +12VDC first to it and then on to the starter solenoid. No 

device that controls the starter directly through its solenoid control 

circuit can do this.



( I have had multiple experiences with these type failures. Allow me to 

pass these experiences on to you and eliminate the time and aggravation it 

would take for you to accumulate them yourself. Use the information as you 

will.



(9) DO NOT ARCHIVE



        John D.

nuckollsr(at)cox.net
Guest

Posted: Fri Apr 07, 2006 1:53 pm Post subject: Why use starter contactor?

At 08:37 AM 4/7/2006 -0700, you wrote:



 	  Quote: 	
		  



 >From:  Ken <klehman(at)albedo.net>

 >Subject:  Re: Why use starter contactor?



       >Possibly because the pros and cons of that have been discussed at 

 length

       >several times here Michael. Several folks related experiences with 

 stuck

       >on automotive starters when I've brought up the subject. 

 Nevertheless I

       >went with a 25 amp rated marine key starter switch which I believe is

       >less likely to cause problems than an additional small relay. A 

 cheap 40

       >amp relay is not immune from sticking either in this kind of 

 service. Got

       >to admit though my key switch will be a bear to change out 

 compared to a

       >contactor or a small relay when/if it ever fails, and it cost more 

 than

       >either.

       >Ken



   Ken:



   Thanks for the thoughtful reply.



  My postulation is if you use a BIG FAT start button and no extra 

 firewall relay/

solenoids/contactors, chance of starter run-on / spontaneous engagement is 

nil.



Has this happened in a car you know of? To the config I suggest in a plane?



   Your comment about *several folks* who claim they had problems is 

 great, but

with out details its like the OV alternator thing, just rumor or irrelevant.


	


    Wasn't rumor. Had many customers report the phenomenon and we demonstrated

    it on the bench . . .

 	  Quote: 	
		  



   There are reasons a starter can run-on. I suspect you are either talking a

old Bendix drive starters or OLD firewall Cessna or Piper firewall solenoids,

which do stick when they get old. Neither apply to our conversation.


	


    Nope, we were talking about modern PM starters . . .



 	  Quote: 	
		  

   People who switched to new starters have got run-ons because the OLD 

 firewall

solenoid was retained and stuck; its NOT an issue of the starter itself.



   This supports my claim that LESS IS MORE. Get rid of that old solenoid and

get a big 60 amp start button.


	


    Not so. "Run on" in the context of PM starters and airplanes had

    nothing to do with the selection of contactors.



    Unlike wound-field motors supplied on B&C (and perhaps other)

    starters, the PM offerings by Skytec (and perhaps others) are

    efficient GENERATORS of electrical power while the armatures are

    spinning down. When the pilot releases the starter button after

    the engine fires, connection between the starter motor and battery

    was being opened just fine. However, IF the starter was wired for

    external contactor, voltage being generated by the coasting armature

    was still applied to the solenoid engagement windings thus keeping

    the pinion gear engaged for some period of time (perhaps 2-5 seconds)

    after the button was released. The starter's overrun clutch prevented

    damage but it was obviously an undesirable operating quality.



    One fix was to go to Figure Z-22 such that the starter's built

    in contactor became the primary electrical switching device. The relay

    allowed any starter switch selected by the builder to stay in place.



    Adding the relay broke power to the solenoid's hold-coil and effected

    immediate release of the pinion gear in spite of the armature's

    spin-down voltage. Another option was described in October of 2004

    when this sketch was published on my website:



http://www.aeroelectric.com/articles/StarterWiring.pdf



    Figure 3 suggests using the "I" terminal of the external contactor

    to exert absolute control over the solenoid's hold coil.



    Of course, the forth options is Figure 1, a 30A push button and

    14AWG wire to replace the relay shown in Z-22 for what has been

    described as the simplest approach. This approach is also electrically

    acceptable but offers the least number of options for selection

    of start switches. The "run-on" or delayed disengagement phenomenon

    is unique to PM starters and has nothing to do with sticking contactors.



 	  Quote: 	
		  



I researched this thoroughly. I talked to SkyTec. The chance of sticking 

starter

is next to nothing.


	


    But not zero . . .

 	  Quote: 	
		    I also asked about the no secondary solenoid and guess

what? They said its made that way and will work fine. Let's say you did get

a run-on, it would be during start, you would shut down. SkyTec shows how

to wire a run-on light if you like. Chance of it engaging in flight? never.



   Skytec has more starters flying than anyone. I think they know what's up.


	


    Yup, ask them about sticking contactors and they can accurately

    report no big problems as will every other starter manufacturer.

    Ask them about delayed disengagement or run-on of their starters

    when wired like B&C starters, and they'll confirm what I've stated

    above.



    No rumors, hard repeatable experiments.

 	  Quote: 	
		  



   QUOTE:



   What about the Bendix?  Maybe it stuck?



**Since Sky-Tec starters do not use mechanical Bendix drives to actuate the

starter, this is actually nearly impossible for a Sky-Tec starter to keep 

itself

engaged with the aircraft ring gear.  Sky-Tec starters are 

electromechanically

engaged therefore requiring voltage to engage the starter's drive pinion 

gear with

the ring gear.  Without voltage, the pinion simply cannot remain in the 

flywheel.

A spring and a helical return will both force the drive pinion back out of 

the ring

gear and into the rest position.**


	


    This is true of every brand of starter using direct engagement of the

    pinion gear by a solenoid that also happens to drive a set of contacts for

    control of armature current.



 	  Quote: 	
		  

   Ref:  http://www.skytecair.com/Cessna_Solenoids.htm

   Cessna (mostly) and Piper, apparently have a history of Firewall Solenoids

sticking, so actually even a factory solenoid (relay) can stick. That is WHY

I suggest a big OLD fat start button, like a race car. (w/ catch diode of 

course)


	


    The sticking contactors on production airplanes is a well known

    phenomenon when OEM's were using the intermittent duty versions

    of the RBM/White-Rogers/Stancore contactors. These looked

    just like the battery contactor shown at:



http://www.aeroelectric.com/Pictures/Contactors/s701-1.jpg



    These contactors had large area, low pressure contacts

    like:



http://www.aeroelectric.com/Pictures/Contactors/S701-1a.jpg



http://www.aeroelectric.com/Pictures/Contactors/S701-1b.jpg



    . . . not the best way to control high inrush devices like

    starters. In later years, the car guys showed us small-area,

    high-pressure intermittent duty contactors like:



http://www.aeroelectric.com/Pictures/Contactors/s702-1l.jpg



http://www.aeroelectric.com/Pictures/Contactors/S702-1a.jpg



    Contactor sticking was virtually eliminated for systems

    where the battery was kept in good shape. The only cases

    we've seen where an owner was able to weld a small-area,

    high-pressure contactor was with a soggy battery that

    barely managed to get the contactor closed but with

    insufficient pressure to get good conduction, hence burned

    and welded contacts.



    We've seen starters wired with the big fat push button

    (or Z-22 relay) weld the built-in contacts too. If the

    battery is soggy or the engagement signal to the contactor

    is tentative,  welding risks go up markedly IRRESPECTIVE of

    who's contactor is doing what to who's starter. I've had

    several builders report this phenomenon where rapping the

    contactor housing on the side of the starter with a

    screwdriver handle would cause it to become unstuck.



 	  Quote: 	
		  



To be fair to Bob, if it ain't broke don't fix it. Nothing WRONG with the

Z diagram xyz, just suggesting if you want a lean mean electrical system

with more than adequate or even superior reliability and safety, while

lowering weight and complexity, consider trashing the BIG fw contactor.


	


    To be fair to me or anyone else, we need to be talking about

    the same problem. The run-on problem described was identified

    in a timely manner, demonstrated, explained, and fixed. It

    had nothing to do with sticking contactors and was unique to

    PM starters.



    The sticking contactors of an earlier design was tolerated for

    decades (from about 1946 through the mid 70's) because when a starter

    contactor did stick, it was backed up by the battery master contactor.

    While every airplane using the old style starter contactor suffered

    the phenomenon, it wasn't a big deal. When the automotive designers

    crafted the high-pressure design, it was welcomed by all.



 	  Quote: 	
		     The next step is get rid of the BIG master contactor. You only need a

   30-60 amp relay if you don't run the starter load through it.


	


    Anyone is completely free to get rid of any parts they wish

    and indeed many builders have done just that. The only thing

    I'll suggest is that the decisions to do so exploit

    the experience and thought processes behind 60+ years

    aircraft electrical systems. An accurate sense of history

    combined with an understanding of applicable simple-ideas helps us avoid

    potentially unhappy and unintended consequences of "the next step."



    If you're ready to hang your hat on an always hot, fat

    feeder from battery to starter mounted contactor/solenoid,

    keep in mind that the starter's built-in contactor can stick

    too. Further, you loose pilot control over making the airplane's

    electrical system max-cold. If those design goals are acceptable

    then so be it. It's your airplane and it's experimental.

    Fly in peace.

    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Fri Apr 07, 2006 2:08 pm Post subject: Why use starter contactor?

John,



     Thank you for sharing this info. It tracks with what we understand

     about the huge list of variables that affect starter and associated

     contactor performance. Bottom line is that ALL starters of ANY brand

     are subject to undesirable behavior for a host of reasons. None

     of these events needs to be more than a frustrating maintenance item

     if we leave certain "Plan-B" options in place for dealing with them

     if and when they arise.



     Bob . . .



At 04:47 PM 4/7/2006 -0500, you wrote:



 	  Quote: 	
		  



   TWIMC (Which is probaly only me),



(1) Electrial Solenoid engaged starters,as used on Lycoming, Chevrolet,BMW,

and Porsche, do stick.



(2) Solenoid engaged starters are disengaged by a spring and an over running

mechanism in the starter gear.



(3) I have personally seen three out of the four named, stick .



(4) They stick and continue to crank the engine, they stick and don't crank

the engine, and all modes of stick in between.



(5) They stick when they are new or old, clean or dirty but mostly they

stick because they are misaligned or have not been lubricated.



(6) One of these starters that fail in the "CRANK the engine mode" with the

+12VDC wired directly to the solenoid has a great big wire as big around as

your index finger HOT and you can't turn it off.



(7) There are many light weight relays capable of eliminating this problem

by attaching the +12VDC first to it and then on to the starter solenoid. No

device that controls the starter directly through its solenoid control

circuit can do this.



( I have had multiple experiences with these type failures. Allow me to

pass these experiences on to you and eliminate the time and aggravation it

would take for you to accumulate them yourself. Use the information as you

will.

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Fri Apr 07, 2006 3:02 pm Post subject: Why use starter contactor?

Robert L. Nuckolls, III wrote:



 	  Quote: 	
		       Unlike wound-field motors supplied on B&C (and perhaps other)

     starters, the PM offerings by Skytec (and perhaps others) are

     efficient GENERATORS of electrical power while the armatures are

     spinning down. When the pilot releases the starter button after

     the engine fires, connection between the starter motor and battery

     was being opened just fine. However, IF the starter was wired for

     external contactor, voltage being generated by the coasting armature

     was still applied to the solenoid engagement windings thus keeping

     the pinion gear engaged for some period of time (perhaps 2-5 seconds)

     after the button was released. The starter's overrun clutch prevented

     damage but it was obviously an undesirable operating quality.


	


I found this problem another way. After installation of one of these PM 

starters my Comanche got hard to start when warm where it hadn't been 

before. I didn't notice because at the time my father was flying it more 

than I was and had several incidents of almost running the battery down 

trying to start the engine when it was hot (carbureted engine, not fuel 

injection). This was doubly surprising as the engine was equipped with a 

shower of sparks ignition system. It would fire but then wouldn't 

'catch' and keep running when the start button was released. The engine 

would spin down and seem to 'catch' just before it quit turning. It was 

very perplexing.



(You have enough information to solve this puzzle but just for fun I 

will post the real problem and the fix in the next message so you can 

think about it for just a moment.)



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Fri Apr 07, 2006 3:41 pm Post subject: Why use starter contactor?

OK, where was I ... oh yeah, the hard starting Comanche after installing

a PM starter.



It seems that someone had wired the start lead to the shower-of-sparks

system to the starter side of the start solenoid. When the start button

was release the EMF generated by the still-turning PM starter would hold

the shower-of-sparks relay in and that would continue to disable the

right mag and keep the left mag on the retard breaker but it wouldn't

provide enough voltage to get the shower-of-sparks vibrator to really do

its thing. When cold the engine would freewheel better when the start

button was released and the shower-of-sparks start relay would drop out

before the engine lost too much RPM and it would start fine.



When trying to start after just a bit of a cool down the engine was

extra tight and would not freewheel so the engine spun down before the

starter did.



The solution? Move the start lead for the shower-of-sparks system  from

the starter side of the solenoid to the start button itself. Now the

power went away instantly when the start button was released and the

engine would catch and run just fine.



BTW, this problem drove me nuts for about 6 months until I finally

figured it out.



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

nuckollsr(at)cox.net
Guest

Posted: Fri Apr 07, 2006 7:01 pm Post subject: Why use starter contactor?

Isn't it amazing how those simple-ideas stack up sometimes?



   Bob . . .



At 04:40 PM 4/7/2006 -0700, you wrote:



 	  Quote: 	
		  



OK, where was I ... oh yeah, the hard starting Comanche after installing

a PM starter.



It seems that someone had wired the start lead to the shower-of-sparks

system to the starter side of the start solenoid. When the start button

was release the EMF generated by the still-turning PM starter would hold

the shower-of-sparks relay in and that would continue to disable the

right mag and keep the left mag on the retard breaker but it wouldn't

provide enough voltage to get the shower-of-sparks vibrator to really do

its thing. When cold the engine would freewheel better when the start

button was released and the shower-of-sparks start relay would drop out

before the engine lost too much RPM and it would start fine.



When trying to start after just a bit of a cool down the engine was

extra tight and would not freewheel so the engine spun down before the

starter did.



The solution? Move the start lead for the shower-of-sparks system  from

the starter side of the solenoid to the start button itself. Now the

power went away instantly when the start button was released and the

engine would catch and run just fine.



BTW, this problem drove me nuts for about 6 months until I finally

figured it out.

glcasey(at)adelphia.net
Guest

Posted: Sat Apr 08, 2006 6:06 am Post subject: Why use starter contactor?

Just another data point in this discussion:  Many years ago (make  

that many, many years...), when I was at GM and working with Delco- 

Remy The subject of stuck solenoids was known.  The system was  

designed so that all the components were sized appropriately and the  

battery would run down before any of the other devices, like the  

starter or wire would fail.  The idea was that the starter would  

stick so the driver would turn the key off and it would revert to  

cranking a dead engine.  If it stuck and the driver didn't know  

enough to shut the engine off then the starter would likely fail  

along with the overrunning clutch.  Not pleasant.  On my  

experiemental I used a "big fat" starter push-button switch wired  

directly to the solenoid on the B+C series-wound starter solenoid.   

the starter is powered through the master contactor.  I admit it was  

tempting to run the starter hot from the battery, but I finally  

backed off from that concept.  I would guess that if the starter  

stuck on and the engine was shut off the battery would run down  

before anything bad would happen.  If it sticks with the engine  

running I guess the only detection would be by looking at the battery  

voltage (no ammeter installed).  The good thing is that this type of  

failure occurs on the ground; the bad thing is that this stuff is  

very expensive.



And then for redundancy I simply wired two "master" relays off the  

battery - one "master" to power the big stuff, including the starter,  

and one "avionics" relay to power the radios.  I probably should have  

wired one of the radios off the master.



Gary Casey



ps:  I just fired the engine for the first time and the performance  

of the B+C starter was very impressive.  I do have a firewall-mounted  

battery, but with an IO-540 with 10:1 compression and a composite  

prop,  the starter spun the engine with AUTHORITY and there was not  

even a hint of cogging over TDC.  The starter was also very quiet,  

implying that the drive gear is well-designed and all the alignments  

were very well done.  I was impressed.

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 08, 2006 7:49 am Post subject: Why use starter contactor?

At 06:59 AM 4/8/2006 -0700, you wrote:



 	  Quote: 	
		  

Just another data point in this discussion:  Many years ago (make

that many, many years...), when I was at GM and working with Delco-

Remy The subject of stuck solenoids was known.  The system was

designed so that all the components were sized appropriately and the

battery would run down before any of the other devices, like the

starter or wire would fail.


	


   Sizing of components to enhance predictability and therefore

   push failures off toward more acceptable ends is one of

   many tools in the system designer's toolbox. The exercise

   you've cited is generally applied when rudimentary

   techniques are not applicable. For example, there's no

   fuse or circuit breaker that might be expected to bring

   a runaway starter to heel. So the FMEA drives designers

   to consider limiting the ability of a system fault to

   bring the whole to ruin. Limiting battery size such that

   sticking contactor events would come to graceful conclusion

   was a valid approach.



   In the aircraft world, we might utilize this approach with

   better assurance of success because we have regulatory

   control over the components used. Unlike cars in the pubic

   domain, we have better assurances that an airplane won't

   get fitted with a bigger battery and that airplane looses

   benefits of the original designed in limits.

 	  Quote: 	
		     The idea was that the starter would

stick so the driver would turn the key off and it would revert to

cranking a dead engine.  If it stuck and the driver didn't know

enough to shut the engine off then the starter would likely fail

along with the overrunning clutch.  Not pleasant.


	


   Suppose we had the task of mitigating this event today?

   For under $1 I can buy a microprocessor that can be

   programmed to watch start signal from the panel, compare

   with power applied to the starter, watch battery voltage

   for potentially damaging attempts to start with a soggy

   battery, and I might even filter the start signal through

   the processor so that a dirty start switch and/or tentative

   operation of the switch doesn't tease the starter contactor

   into welding. If any undesired condition is detected,

   I at least have an opportunity to annunciate it to the

   operator and in some cases terminate the start attempt

   -AND- annunciate the condition.

 	  Quote: 	
		     On my

experiemental I used a "big fat" starter push-button switch wired

directly to the solenoid on the B+C series-wound starter solenoid.

the starter is powered through the master contactor.  I admit it was

tempting to run the starter hot from the battery, but I finally

backed off from that concept.  I would guess that if the starter

stuck on and the engine was shut off the battery would run down

before anything bad would happen.


	


   Had a Glassair stick an always hot starter wire and the brand

   new RG battery was cranking merrily away long enough for

   the builder to get out, remove the cowl and disconnect

   the battery. The starter survived (although no doubt

   short on future service life). The builder subsequently

   moved his starter feed to the downstream side of the

   battery master contactor.



 	  Quote: 	
		     If it sticks with the engine

running I guess the only detection would be by looking at the battery

voltage (no ammeter installed).  The good thing is that this type of

failure occurs on the ground; the bad thing is that this stuff is

very expensive.


	


   I was at OSH one year when a story flashed around the field

   about one of the airshow performers having landed and discovering

   that his starter and ring gear were all chewed up. The off-hand

   diagnosis was that high g-loading during his performance caused

   a tentative closure and subsequent welding of his starter

   contactor. I would have given $100 to get my hands on all the

   parts and to see how they were installed.



   I would guess that it's far more likely that the starter

   stuck on initial cranking of the engine and the pilot

   was mentally concentrating on the performance task before

   him. He might have made good use of the $1 processor.

 	  Quote: 	
		  And then for redundancy I simply wired two "master" relays off the

battery - one "master" to power the big stuff, including the starter,

and one "avionics" relay to power the radios.  I probably should have

wired one of the radios off the master.


	


   . . . or supplied a normal-feed diode from main bus to

   the avionics bus and you could now call it an e-bus.

 	  Quote: 	
		  Gary Casey



ps:  I just fired the engine for the first time and the performance

of the B+C starter was very impressive.  I do have a firewall-mounted

battery, but with an IO-540 with 10:1 compression and a composite

prop,  the starter spun the engine with AUTHORITY and there was not

even a hint of cogging over TDC.  The starter was also very quiet,

implying that the drive gear is well-designed and all the alignments

were very well done.  I was impressed.


	


   That starter was in development for years before it hit the market.

   Early endurance issues were pretty much limited to high stress

   points in the castings which were identified and fixed early on.

   We were on a trip to CA to participate in Voyager support activities

   at Mojave when Bill stopped by Robinson to meet their president

   and discuss starter issues.



   I believe to this day, the B&C starter still goes out on 100% of

   Robinson products. Starters are pulled off of Robinson helicopters

   when they come back for 2,000 hour overhaul. This is one of

   VERY few instances where a manufacturer has an orchestrated

   opportunity to track a product's field performance. Many returned

   starters look like junk yard dogs having suffered the rigors

   of various duties in the field. However, when opened up wear rates

   indicate that the starters would easily run another 2,000

   hours without further attention. Continental gave up trying

   to 'kill' a B&C starter after 5,000+ starts on the test stand.



   Odds of you being a satisfied user of this starter are very good

   but I applaud your decision to run the starter downstream of

   the battery master contactor.



   Bob . . .

gmcjetpilot(at)yahoo.com
Guest

Posted: Sun Apr 09, 2006 9:02 am Post subject: Why use starter contactor?

 	  Quote: 	
		  From: "Robert L. Nuckolls, III" 

   
	


     >I was at OSH one year when a story flashed around the field

   >about one of the airshow performers having landed and discovering

   >that his starter and ring gear were all chewed up. The off-hand

   >diagnosis was that high g-loading during his performance caused

   >a tentative closure and subsequent welding of his starter

   >contactor. I would have given $100 to get my hands on all the

   >parts and to see how they were installed.

     >I would guess that it's far more likely that the starter

   >stuck on initial cranking of the engine and the pilot

   >was mentally concentrating on the performance task before

   >him. He might have made good use of the $1 processor.

   

  Bob:

   

     >I would guess that it's far more likely that the starter

   >stuck on initial cranking of the engine and the pilot

   >was mentally concentrating on the performance task before

   >him. He might have made good use of the $1 processor.

   

   

  Don't you there's a good chance the firewall solenoid was mounted 

in a manner that positive G's caused it to close. This is common on 

acro planes with firewall contactors mounted where pos G's close them. 

   

  Van's aircraft found this and than recommended the contactor be mounted 

sideways. Well that also turned out to be a bad idea. Because the solenoid 

Van's sells is not made for sideways mounting, the solenoid galled and 

failed.

   

  The ultimate solution was to mount the start solenoid so Positive G's 

would keep the contacts open, since negative G's are less critical, 

the way to mount was with the metal cap down (on typical contactor).

http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1144596827-336-39&browse=electrical&product=start-sw

  (as shown)

   

   

  Here is some more goodies from SkyTec's site:

   

  As far as unknown run-on? starter backdriving. Why not  

install a run-on light if possible (think it applies to HT model):

http://www.skytecair.com/images/warning%20lights%202.JPG

http://www.skytecair.com/images/Starter_RunOn_Doc.pdf

  (also see note below on Robinson HT skytec starter)

   

    How to wire a starter push button:

  http://www.skytecair.com/images/ST2_Wiring.pdf



   

  Interesting SkyTec standard or replacing B&C on Robinson Helicopters?

http://www.skytecair.com/images/HT%20Robinson%20Convert.pdf

   

  Also the new SkyTec NL starter NEEDS a firewall solenoid:

http://www.skytecair.com/Wiring_diag.htm

  (No choice, you must use a FW solenoid with the new NL starter)

   

  New NL starter, cool animation on reset of shear pin 

  http://www.skytecair.com/NL%20Shear%20Pin.htm 

  http://www.skytecair.com/Lycoming.htm

   

    Interesting note on shower of sparks and helicopter wiring:

http://www.skytecair.com/Helicopter_wiring.htm

  (some one commented on a problem, I think this is relative)

   



  George



  

 

   



		

---------------------------------

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Mon Apr 10, 2006 6:06 am Post subject: Re: Why use starter contactor?

A dump of what I think I know and some vaguely suspicions--



Stuck Starters--The starter motor pinion is 1.2 inch in diameter, the ring gear is about 12 inches in diameter--a 1:10 ratio. The starter (non-geared type) turns at several thousand RPM to turn the engine at several hundred RPM. When the engine is running at maybe 4000 RPM, an engaged pinion would turn the starter at 40,000 RPM. 



1) Is this even possible?

2) Since a PM starter would be a generator, what would be the effect?

3) Would not a pilot have any way to know this?



Contactors Generally--The Stancor White Rogers etc. B&C was a wimpy return spring because a beefy return spring would require too much power to hold compressed. I suspect the thing will re-close at only a few G's. Bob N. had access to a G-force test rig. Please Bob can you run some tests for us? A Kilovac EV200 would be good too. A shake table would yield good data too.



Starting Contactors Specifically--I side with Jet Pilot George. A 20A pushbutton switch is simple, reliable, lightweight...and heck if it sticks the button won't pop back out.



Consideration of contact-arcing prevention and transient voltages need to be addressed, too. There are big sparks to lasso.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

frank.hinde(at)hp.com
Guest

Posted: Mon Apr 10, 2006 6:29 am Post subject: Why use starter contactor?

My extremly limited knowledge of stuck starters comes from a friend who

flew 250 miles at night in a C172 with the starter engaged the whole

way...I was amazed...And so was the owner at the repair bill!



I do like the simple warning light idea wired to the starter side of the

contactor and will be retrofitting a 'Radio Shaft' mini 12V LED to my

panel



Frank

RV7a...Almost at paint stage.



A dump of what I think I know and some vaguely suspicions--



Stuck Starters--The starter motor pinion is 1.2 inch in diameter, the

ring gear is about 12 inches in diameter--a 1:10 ratio. The starter

(non-geared type) turns at several thousand RPM to turn the engine at

several hundred RPM. When the engine is running at maybe 4000 RPM, an

engaged pinion would turn the starter at 40,000 RPM. 



1) Is this even possible?

2) Since a PM starter would be a generator, what would be the effect?

3) Would not a pilot have any way to know this?

rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Mon Apr 10, 2006 7:00 am Post subject: Why use starter contactor?

 	  Quote: 	
		   Contactors Generally--The Stancor White Rogers etc. B&C was a wimpy

 return spring because a beefy return spring would require too much

 power to hold compressed. I suspect the thing will re-close at only a

 few G's. Bob N. had access to a G-force test rig. Please Bob can you

 run some tests for us? A Kilovac EV200 would be good too. A shake

 table would yield good data too.


	


It seems like you could energize one with a bit of wire, and

swing your arm around round and round like a propeller, like

you used to do as a kid, to generate some Gs.  My battery

contactors are laying on their side, so the only G force that

will cause them to open will be acceleration, and my engine

won't have that much power.



In any case, if this were a real problem, wouldn't all

those aerobatic guys be complaining a lot?



BTW, what's the status on your solid-state contactors?

Once those are available, the "hand grenade" contactors

will go the way of the vacuum tube.



-- 

Mickey Coggins

http://www.rv8.ch/

#82007 finishing

do not archive

_________________
Mickey Coggins
http://www.rv8.ch/

nuckollsr(at)cox.net
Guest

Posted: Mon Apr 10, 2006 8:05 am Post subject: Why use starter contactor?

At 07:06 AM 4/10/2006 -0700, you wrote:



 	  Quote: 	
		  



A dump of what I think I know and some vaguely suspicions--



Stuck Starters--The starter motor pinion is 1.2 inch in diameter, the ring 

gear is about 12 inches in diameter--a 1:10 ratio. The starter (non-geared 

type) turns at several thousand RPM to turn the engine at several hundred 

RPM. When the engine is running at maybe 4000 RPM, an engaged pinion would 

turn the starter at 40,000 RPM.



1) Is this even possible?


	


    For a short period of time . ..



 	  Quote: 	
		  2) Since a PM starter would be a generator, what would be the effect?


	


    All starters have over-run clutches to prevent the engine from driving

    the starter. While the pinion is indeed spinning fast, the starter

    is turning MUCH slower.



 	  Quote: 	
		  3) Would not a pilot have any way to know this?


	


    If it's an electrical 'stick' a light will tell you that

    it's happening. A mechanical stick generally goes unnoticed.

 	  Quote: 	
		  Contactors Generally--The Stancor White Rogers etc. B&C was a wimpy return 

spring . . .


	


    Don't understand the reference to B&C. They

    don't sell a starter contactor with a "whimpy

    return spring" . . .



 	  Quote: 	
		    . . .  because a beefy return spring would require too much power to 

 hold compressed. I suspect the thing will re-close at only a few G's. Bob 

 N. had access to a G-force test rig. Please Bob can you run some tests 

 for us? A Kilovac EV200 would be good too. A shake table would yield good 

 data too.


	


    Spring rates are selected for trade offs for pull-in voltage,

    contact opening force and contact spreading velocity. Once a contactor

    is energized, the holding force on the seated plunger is huge.

    Spring rates are not a consideration for energy required to

    KEEP the contactor closed, only voltage required to get it

    closed in the first place.



    I have tested the S-W-R contactors on the centrifuge and was able

    to close a continuous duty contactor (light spring) at about

    4-5 g's. Of course, continuous duty contactors are used only for

    battery contactors and are ALREADY closed in flight so g-loading

    is not a matter for consideration.



    An intermittent duty S-W-R contactor wasn't available to me

    for testing but one might safely assume that the springs

    are stronger and might take more g-force to close them. But

    this begs the REAL question . . . why would anyone use

    a S-W-R contactor for a starter contactor in the first place?



    The problems cited by Skytec for replacing starters on older

    airplanes focused on intermittent duty versions of the S-W-R

    contactor used on tens of thousands of older airplanes

    originally fitted with wound field starters . . . demonstrably

    gentler on a starter contactor but STILL prone to sticking.

    When the wound-field starter was replaced with a PM machine,

    inrush currents went up by as much as 2 times that of

    conditions prevailing when the S-W-R designs were fitted

    to those airplanes decades ago.



    The sad fact was a recommendation to replace the S-W-R,

    high area, low pressure contactor with a high-dollar, Eaton-CH

    6041H series contactor. These are fine, mil-spec contactors

    but completely unnecessary.



    We've discussed the advantages of the newer low-area,

    high-pressure starter contactors used in the automotive world

    for decades. This is the style of contactor that was offered

    by the B&C in their original starter installation kits

    and later by the AeroElectric Connection when we had the

    parts business. It's been used on millions of cars having

    PM starters . . . while it can STILL stick due to external

    effects of soggy battery or tentative control signals, the

    overall service life of this device has been satisfactory

    and cost of ownership is very attractive.



    This modern starter contactor will not be closed by g-loads

    any of us hope to experience and would probably pull the

    wings off before the contacts close. Further, if one installs

    the S702-1 style contactor on the firewall as recommended,

    orientation of the plunger motion is such that you would

    have to fly into a mountainside to effect an unintended

    closure of the starter contactor.



    The whole g-loading concerns for starter contactors

    thing was a tempest in a teapot from the get-go. It's easily

    analyzed, understood and DESIGNED out by judicious

    selection of modern, low cost contactors.

 	  Quote: 	
		  Starting Contactors Specifically--I side with Jet Pilot George. A 20A 

pushbutton switch is simple, reliable, lightweight...and heck if it sticks 

the button won't pop back out.



Consideration of contact-arcing prevention and transient voltages need to 

be addressed, too. There are big sparks to lasso.


	


    Yup, the S702-1 and it's close cousins have slain these

    dragons too. Contact spreading velocity is fast enough to

    keep arcing to a satisfactory level and transients were

    never a threat to contactors . . . but the S702-1 comes

    with it's spike catcher built right in.



    The Kilovac and 6041H contactors are truly fine devices

    and there are cases where their application makes good

    sense . . . but they to0 have their vulnerabilities

    and limitations. See:



http://www.aeroelectric.com/Pictures/Failures/6041_Contactor_Failure.jpg



http://www.aeroelectric.com/Pictures/Failures/Kilovolt_Contactor_Lightning_Damage.jpg



    These discussions have been long on hip-shot recommendations

    based on ill-conceived worries and short on systems integration

    analysis based on design goals for low cost of ownership,

    failure tolerant design and an understanding of all the

    ingredients in the recipe for elegant solutions.



    Bob . . .

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