ram3500-RCU

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Can anyone tell me if the RCV 91 can be mounted inverted with a reliable idle and run? I am considering this engine for it's compact size yet ability to swing a larger prop more to scale proportions. Thanks.

mboland

Your question is a little confusing.
Do you mean the 91Sp or the 91CD?
The CD swings a standard size prop that you would use on any 4 stroke.
The SP swings the larger props but as it's mounted facing forward the inverted part of your question is not clear.

Can you give us a few more details?

ram3500-RCU

My Feedback: (221)

My bad. I meant the CD version, but it was my understanding that this version also swung larger props at slower RPMs.

Juice

ram... The RCV SP-series engines swing larger props at slower RPMs. They come in 60, 90 and 120 sizes.
The RCV CD-series engines swing typical size props at typical RPMs They come in 58, 91 and 130 sizes.
All RCV's are compact for their displacements.

I can't comments on the reliability of the CD series becuase I don't own one, but almost all users comments about them are positive.

Juice

saramos

The CD series turns a normal size prop. It is geared 1:1 and still uses a rotary valve with the cylinder sleeve spinning around the piston. With the glow plug mounted to the side of the chamber, I would think it would run fine inverted. This is deductive reasoning and not first hand knowledge. Hopefully, someone with one will comment. Here's a link to RCVs How It Works page.

http://www.rcvengines.com/how-it-works.htm

Scott

ram3500-RCU

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Thanks Scott. The CD version won't do it I guess. I'm rethinking the power for my latest P-38 project. I originally purchased two Moki 61s for it and I think the power is there (because I'm shooting for no more than 16lbs), but I can't get anywhere near the scale size prop with those engines. At 1/7 scale, I need 19 11/16" props. I turned a 20 X 10 prop with the RVC 120 SP. Maybe it will be a case of static and flying props.

mboland

I have a couple of 58CD's, both mounted inverted initially.
The RCV uses a short intake manifold which puts the spray bar further from the centre line of the motor than most modern 4 strokes. As the tank position is usually set up to be centred on the engine centre line this is the only problem you will encounter.
On the Texan I flew it for some time until I just got sick of the change in tune when flying inverted, so I changed the motor to side mount. As the Texan does not Knife Edge that well it has solved the problem.
The CMP P-40 does not give you the space or option to mount the engine anywhere but inverted. Same fuel problem, tune well for normal flight, goes lean and quits when inverted. Tune well for inverted and runs rich and sluggish in normal flight. The solution was to fit a Perry Pump.
So apart from the fuel supply issue I guess the answer to your question is that these motors run fine inverted, probably a bit better than most other 4 strokes as the plug is not exposed to the chamber except at firing time.

ram3500-RCU

My Feedback: (221)

Thanks. Good input.

alanc

all our YT/KMP display aircraft that use the CD 91 use it inverted, no problem,

The full size airplanes didnt have direct drive to swing thise props, they did it with a gearbox,

MANFRED

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If you want a scale size prop, use a static display prop.

ram3500-RCU

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Yea, that is my intension at this point.