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Starting the -52 in cold weatherStarting the -52 in cold we

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rmfitz(at)direcway.com
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Posted: Tue Feb 21, 2006 8:27 am Post subject: Starting the -52 in cold weatherStarting the -52 in cold we

A couple months ago I posted a question about "blubbering" after take-off.

 There were many helpful suggestions both on and off-list,  thank you.

 I did find a bad plug but the problem persisted until, out of 

curiosity, I opened the manifold drain after priming (7 strokes) and was 

shocked by how much raw gas poured out.  Apparently gas was pooling in 

the manifold  and laying there during level run-up. Once a stable climb 

angle was established, at full power, it was sucked (or blown) into the 

bottom cylinders causing the temporary roughness.  I now prime, pull 4 

blades, and drain the manifold before starting. 

This is just theory at this point since it's winter and and I've only 

made a few flights but so far the problem appears to be solved.

Now about that "eggcup" of gas it takes for a hydraulic lock;  are we 

talking parakeet or ostrich?



bob

52BN

Rob Rowe wrote:



 	  Quote: 	
		  



Russian manual recommends 2-3 minutes in summer between priming & starting, rising to 3-4 minutes in winter due to lower fuel vapourisation rate.



They also warn about over-priming as this "washes" oil off the cylinder walls & presents a hydraulic lock risk too ... it only needs an eggcup of liquid. 



If you've a manifold drain, leave it open during priming & you will be surprised as to how much fuel can pour out even with 6 or 7 cylinder primes.



Rob R.





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http://forums.matronics.com/viewtopic.php?p=13718#13718

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Rob Rowe

Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

Posted: Tue Feb 21, 2006 9:44 am Post subject: Re: Starting the -52 in cold weatherStarting the -52 in col

Bob wrote



 	  Quote: 	
		  

Now about that "eggcup" of gas it takes for a hydraulic lock; are we 

talking parakeet or ostrich?

	




Good question! 



Confess the "egg cup" is apocryphal ... however my layman calculations suggest the following (I'm sure those more knowledgable will correct me);



Engine capacity = 10.161 litres

... giving 10.161 / 9 cylinders = 1.129 litres per cylinder swept volume

... with a compression ratio of 6.3:1 (+/- 0.1)

... this allows 1.129 / 6.3 = 0.179 litres (179 ml) cylinder volume at TDC



So 179 ml of fluid produces a full hydraullic lock ... even c.80 ml would double the compression to 12.6:1 ... so maybe two (chicken!) egg cups for a full lock and one to stress a plug core / seals etc.



Bottom line ... not very much liquid!



Rob R

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