donehead

Hello Folks !

Here is a qouestion one of you might know. I have been toying with the ide to replace my single 0.40 with twin engines. Well it's actually a 0.46 but just for the example. Now i am wondering if two 0.20 produce the same or simmilar power as a single 0.40. Any ideas ? thank's george

William Robison

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donehead:

Generally speaking, two 20 engines will not have any more power than one 40. But. What power they do develop will be applied more efficiently, because they will usually have greater propellor disc area.

All other things being equal, a pair of 20's will give about the same effective power as a 50 or 52 engine.

Bill.

donehead

Bill !

Thanks for the info this sounds very encouraging . Now the next obvious question question is : what make of 0.20 engines has ones that will runn in both directions ? I would think counter rotating props would be of advantage? george

William Robison

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DH:

There are definite advantages in having the right engine reversed in rotation.

But I don't know of any manufacturers currently supplying reverse rotation emgines in any size.

OS used to supply complete reversed engines, and crankshafts for user installation. Cox and K&B supplied the crankshafts.

Current availabitity is problematic - I've had a reverse crank on order from MECOA/K&B for over a year. They keep saying "Real soon, now."

If you are willing to go with 4-strokes, many Saito engines have available cams that will reverse their rotation. Saito twins use a "Reverse" cam on the left cylinder, you have to find the one that will fit into a single cylinder engine, then you have reversed it.

The easiest thing is using both engines with the same rotation, and realize it will fly better with the right engine out than it will with a dead left engine.

I'm sure there are many reversed engines in owner's hands, perhaps if you post you might find one, then get a matching standard engine.

Hope this helps.

Bill.

big max 1935

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Enya four strokes can be reversed with out any additional parts. They run great both directions. >>>>>>>big max 1935>>>>>>

TimC

[QUOTE]Originally posted by big max 1935
[B]Enya four strokes can be reversed with out any additional parts. They run great both directions. >>>>>>>big max 19
35>>>>>> [
I'm assuming all that has to be done is use the other hole in the cam drive?

big max 1935

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Tim: The Enya instruction sheet gives the information how to do it & has pictures , been a long time since I did one & I no longer own one. This is just some thing that I did not file in my memory circuits! MAX H

TimC

Thanks Max.

big max 1935

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This is really pushing my memory. If I remember right on older engines with the four bolt removable front end, you could turn the front so the carb is at 9 o'clock & bolt it back up , that would let it run in reverse. As far as I know the only American made engine that I have ever worked on that was made to run clockwise was a GHQ & you old timers know about that one!!
>>>>>>>>>>>>>big max 1935>>>>>>>>>>>>>>>>>>>>>

JoeyCoates

I used to have an Enya 25 plain bearing TV? engine which I did the rotateing of the front end 90 degrees on and used two of the engines on a twin engine self designed biplane. It worked great although I cannot comment as to a difference on single engine opperation as I never lost an engine.

JB Rekit

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Even if 2 .20's end up making more power than a .46, they would still weigh a lot more.

just some food for thought if weight is a concern.

pe reivers

MVVS makes reversed engines to order.

Matt Kirsch

My Feedback: (21)

Most full-scale twins do not have a reversed engine on one side. In fact, the P-38 is the only plane I can think of offhand that was like that.

There are more issues to contend with beyond reversing the engine, too. You'll need to run a reverse-pitch prop on the reversed engine. Pusher props work, but there are very few sizes of pusher props available. If you're looking for scale fidelity, the first thing everyone will notice is that the right engine is turning the wrong way...

There are advantages to having a reverse-rotating prop on one side, but most of them can be obtained through properly aligning the engines.

The old Hobbico Twinstar, for example, was a plane that had a reputation of being a good engine-out flier. Its secret was that the left engine had about 1 degree of left thrust, and the right engine had about 3 degrees of right thrust and down thrust, IIRC. If the left engine died, the offset of the right engine counteracted most of the nasty tendencies twins usually exhibit when an engine goes out. In cases where the right engine quit, the offset in the left engine did the same thing.

Then again, you can handle engine-out situations the easy way: When one engine quits, kill the other and treat it as a complete deadstick.

The offset figures are just from memory. Someone else measured them a few years ago, so you'll have to go looking for the figures just to double check.