Diggr

When I first got started playing with glo engines back in my Ringmaster days, I seem to remember that the crazy things would seem to run just as well backwards ( ie. clockwise when viewed from in front of the prop) as the other way around. I have 2 OS 40-FX NIB available and am wondering if there is any reason I can't plan to run the pair in opposite rotations in a twin engine arrangement. From what I've seen is the engine documentation, there seems to be no "required" direction of rotation.

Thanks in advance for any information.

Rodney

Direction that it runs depends on how it is ported. There are some designs that can run in either direction but most RC model engines are designed to run counter clockwise as viewed from the front, clockwise if you are viewing from the cockpit.

JohnBuckner

My Feedback: (1)

What you are asking about actually goes in many different directions, Lets assume you manage get a combinations of engines to allow one to run backwards. That presents the problem of suddenly you now require pairs of prop sizes matched but one with reversed pitch (Pusher props). The possible avalible sizes are severely limited and this presents many road blocks to the designer and the pilot.

With the most common twin engine configuration will having Counter rotation of the engines have any benefits??? Yes it will present slightly less "P" factor during certain configurations with the critical engine out. However for our models the problems presented by the lack of practical avaliblity of certain prop combinations is a far greater problem. The above worst case scenario can be overcome by proper training and pilot action but the lack of prop combinations is a much bigger problem.

John

Rodney

One think I did not mention in my previous post is that some of the engines may have a reed valve for fuel feed. If so, they do have a tendency to run backwards and run well in either direction.

Diggr

Thanks for the input guys. It was just a thought, but I don't see enough gain here to warrant the pain of trying to get it to work. Appreciate the help.

JohnBuckner

My Feedback: (1)

Excellent Decision

Bax

My Feedback: (11)

Almost all two-stroke glow engines use crankshaft porting. They will not run in the reverse direction unless the crankshaft is ported for reverse direction. Then, the engine will run as well in the reverse direction as it would with a regular crankshaft. The problem is that reverse crankshafts are just not made any more. The demand is so low that the engine manufacturers just won't consider it.

For four-stroke engines, you need a reverse camshaft. Again, they're not available for the same reasons.

Diggr

After reading the above post, I stopped to think for a bit. [Not a bad idea, from time to time]. I'm convinced that the reverse running engine was a Cox .049 reed valve. The McCoy 35 in the Ringmaster was as far as I can tell crank ported.

I pulled up the manual for my OS Max 40FX engines and looked carefully at the exploded drawings, and there it is, crank porting! Admitting that these engines are NIB, I've never tried to start them and get them to run backwards. But, I'm convinced now that such a feat would be easier than finding a chicken with lips.

Reference the contra-rotating props, further research indicates that it may be appropriate in the case of high horsepower engines with large props, P-factor and such. But with a 1.3 HP engine swinging a 10 or 11 inch prop, who am I kidding besides myself?

Again, thanks for the attention to the question; I learned a lot.

Happy building,
Diggr

52larry52

My Feedback: (1)

Diggr, By the way, those O.S. 40FX engines are nice sweet running engines so do use them in something. The 40FX doesn't have the power of it's larger displacement brothers the 46FX and 46AX but they run just as well. Use them in something that doesn't quite need the power of the 46 size.

Gray Beard

My Feedback: (-1)

Sure didn't have that prop problem when I was looking for new props for my 40 engine at Nice Twice. Don't have a clue where they got them all but they had a huge selection of reverse props and almost none in regular rotation for the small engine. 10 and 11 inch. APC no less.

JohnBuckner

My Feedback: (1)

Not everyone has a "Twice Nice" avalible to them in their neighborhood, however the real factor in the reluctance for most RC multiengine projects to use is the unavalibillity of modern counter rotating engines as noted by Bax.

In addition to this is the very poor selection of propellors in tractor and pusher pairs. This is possibly even a greater factor as noted by me.

John

Gray Beard

My Feedback: (-1)

John, I wasn't trying to say they are easy to locate but I was having a reverse problem in finding any prop selection for my little .40 engine. I was in shock they had all those reverse props on hand at all, boxes of them. I'm in need of 10 and 11 inch props in 4 pitch and can't locate them in any of the three local shops. I found a 10 and 11X6 and that was it. Nice isn't the place it used to be after Denny sold it either. You can't get a lot of the basic building items you used to either, no SIG products at all now and glue and epoxy, forget it. I still stop at nice first but end up at Hobby People and Hobby Town. Between the three I can usually find most of what I need. Shopping on line is becoming the only way to find things without driving all over town.
Next weekend is the swap meet at Bennett so I will probably score better there.