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Helis and fixed wing

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Saturday, May 7, 2016

RCGF 10cc Muffler Adaptation

In order to get the cowl on the pipe on the muffler had to be trimmed about 1-2 cm. This short stack sprays the airframe with oil... I don't think it affects performance much.

On the 30cc DLE I used rc car muffler couplers as extensions and they work awesome. I found a couple of options for the Spitfire and tried them out this morning.


This is the full car extension, comes with a short coupler and the extension. The bent pipe is soft silicone, but is about 6 mm or so ID. The muffler pipe  on the engine is 10mm ID. Thats a 40% loss in diameter, and Poiseulle adroitly predicts a significant increase in resistance to flow (1/r4). I expected some significant back pressure and figured on some rpm loss.



This lasted 3 min. The solder bead I had on the muffler melted off as I expected it might, and the engine threw the extension and coupler off. She immediately gained the almost 500-600 rpms she lost due to back pressure. So much for that one...




So I went with just the longer coupler, and she runs fine. It gives me that 1-2 cm back, but I suspect there will still be some oilage. RPM performance is maxed, around 8200 rpm at full.

I hope to maiden her out in Hudson next week. Need a good clear, calm day.



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