Bill DCat

I'm building the T/F P51D 1/7th scale mustang. I'm going to be using the Super Tigre G75 engine with the Top Flite In-Cowl muffler. I'd just like to confirm that the proper way to mount this engine/muffler combination is to mount it inverted.

Has anyone done this? How did it work out / perform? Is there anything I should be cautious of?

Thanks in advance...
Bill DCat

Bax

My Feedback: (11)

The plans show an inverted mount. Any glow engine can have difficulties running inverted. Make sure the engine's well-broken-in before you put it in the P-51 for flying. You'll need to get the settings as right a possible before you fly.

Inverted engines can have difficulties at low to medium throttle settings because the glow plug acts as a sump and is affected by unburned fuel. Idle and acceleration are particularly affected.

Many times, though, once the engine's started, you have no problems, but it's getting the engine started that can be a problem...it can easily flood out. In the past, I had a model with an inverted engine that I had to stand on a wingtip to get started. It was then just fine.

Bill DCat

Bax,
You mentioned that for an inverted engine, it should be well-broken-in before putting it in the P-51 for flying. Should I perform the break-in with the engine inverted or right-side-up in a test stand? Or does it make any difference?

Thanks for all the help thus far....

Bax

My Feedback: (11)

Break in the engine right-side-up. This will allow you to get familiar with it and get the needles set close to where they'll eventually wind up. If you can fly it right-side-up, then all the better. The better the engine's broken in before it's used inverted, the better off you'll be.

Once in the new installation, only minor tweaking on the needles should be needed to dial-in the engine.

parabellum

I wonder if there is engine with reduction gear built on.

the reduction gears will be two stage to get the direction of rotation back to cc.

the reduction gears should be where the carb is.

this will lower the engine by 2-3 inches, and eliminate the need to mount the engine inverted.

prop shaft is 2-3 inches above crank shaft.

reduction gear will allow scale 3 / 4 bladed prop to be used in low rpm.

how hard can it be to make this? it should be quite easy.

Bax

My Feedback: (11)

Right now, there's nothing like what you mentioned. O.S. made geared .61-size engines in the 1970's, but they were very short-lived. The prop was off to one side, and the carburetor was in the normal place.

A reduction drive isn't easy because of the high RPM turned by the engine, the harnonics caused by the power pulses of the engine, and the vibrations of the propeller. Gears and bearings tend to wear rather quickly. Cooling becomes a problem, as well as handling the thrust loads.

It sounds easy, but it's not.

parabellum

http://www.osengines.com/history/ostimeline09.html

yes, I see they have attempted something similar.
but they seem to be just one gear reduction, and not two.
making them rotating in opposite direction of the engine.

probably hard to optain these.

Bax

My Feedback: (11)

Actually, the engine ran with reverse rotation so that standard propellers could be used. Otherwise, you'd have to get reverse-rotation, or "pusher" props, and there aren't many available in the larger sizes.

Alex-Limassol

I am about to start building my P51D 60 ARF from Top Flite and I am contemplating between a SAITO 115 GK and a Saito 125 GK.  Has anyone build this model using either one of these engines?