Q-40 Racing Discuss AMA 422 and any other variants of Quarter 40 racing

Changin engine position?

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Old 01-25-2010, 09:50 AM
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diggs_74
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Default Changin engine position?

While waiting for the supplies to get started on my AR-6 molds I decided to restore my old Polecat.. It's been thru the ringer a few times but is structurally sound.. I was looking at the engine position and wondered if it would be within the rules to rotate the engine so the muffle was at a 6 o'clock position.. This would require some mods to the front end as far as the engine cover (must be a cover because cowls aren't legal in Q40 ) but the overall shape of things wouldn't change..

Oh, the reason for doing this is to improve the relative position of the venturi to the tank..
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Old 01-25-2010, 10:13 AM
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Default RE: Changin engine position?

It is legal Lee, that is the way my new design is oriented for that reason, as well as a couple of aerodynamic reasons too! The only rule concern is the 3/4" top of the piston clear all around. The Polecat is set up so that the cheek cowl is clear when the piston is at 9 o'clock, so by rotating the engine you would still be clear (since the cheeks stick out further).
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Old 01-25-2010, 10:30 AM
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Default RE: Changin engine position?

Lee,

I built a LOKI for Dennis Cranfil this way. I made a mold of the cowl I used. I would have to dig it out but if you want one it is yours. I don't have any pictures but it was an easy modification to fit the new cowl.

As far as the whys and hows. The theory was that the tank position in the PCAT/LOKI was too low and caused issues with consistant engine runs. By over rotating the engine the fuel pick-up essentially was lowered to be more in line or lower with the tank.

Personally, I never saw an issue with this and yet to have a problem with it. But they certainly caught a bad rap because of it.

Dan
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Old 01-25-2010, 10:58 AM
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Default RE: Changin engine position?

That would be great Dan.. One of the reasons for it is the better fuel delivery but the main reason is because the nose is so beat up. Besides, it will be a little different..
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Old 01-25-2010, 11:06 AM
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Default RE: Changin engine position?

Dan, I wasn't saying anything bad about your plane!! I was referring to the way I set mine up for my own design, not as a reaction to negative comments about an existing airplane. My tank can't be up as high as yours is, therefor I rotated my engine to allow for this. Sorry if you thought I was attacking you or anyone else []
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Old 01-25-2010, 11:48 AM
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Scott, no offense taken. Those comments were not directed towards you and your design.

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