some needs to build a reversable engine where a spare crank is needed and liner for all these new rear engine planes any ideas i see it bolting right onto the front of crank case, carb and everything just reversed am i too late bet its already been done

Would an engine like the old OS FSR's work?
The ones you could unbolt the front as well as the back.
Seems as though you could swap them and it would do what you want.
It would put the exhaust on the opposite side though.
Hope Hobbsy doesn't delete this one...

JLK

didnt know os even made 1 like that but yes ur right about the exaust being reversed too but some smart engineer could figure that prob out i bet thx jlk

Here's a pix of one I got off Google Image:
You can see what I'm talking about.
http://www.rctradingpage.com.au/pict...s/IMG_0152.JPG
JLK

yes thats the idea i was looking for and u could block off the 1 exaust with a bolt on plate good idea jlk
just as an aside it would work for twin engine planes to conteract the torque maybe?

For my twin cam Enya 4 strokes there are instructions that tell you how to arrange the cam gears to get reverse rotation.
JLK

wow didnt even think it would work for 4 strokes cool ive had my lil 049 cox engines reverse on there own before and had 1 that ran better that way lol or it seemed too thats what gave me the idea this morn but 4 strokes i thought might have too many moving parts

Pusher props work as well.

yes dunker that was my original idea was for all the new pusher planes on the market just had another idea too how does this sound 4 bolts on the bottom of crank case then just take them loose and spin it around 180 degrees? and put liner in backwards or a replacement liner

The sideport engines or the engines with reed valve are reversable engine. The Enya or other engines with front house can turn in other place and run other way.

Not 180 degree, but 90 degree when turn fronthouse from top to left.

Jens Eirik

What about a crankshaft the protrudes on both ends. Bolt a prop to either end and turn engine around to get the desired rotation.

You guys do know they make pusher props right?....Rog

yes but what about the vast amount of 2 engine arfs coming out and counteracting the torque of 2 engines? thats where a reversable engine might come in handy

All:

Many two stroke makers will supply cranks for reverse rotatioon, OS does for some models, as does K&B, Fox also has reverse timed cranks available.

In the four strokes, as stated above the Enya can have the existing cams retimed for reverse rotation, and there are reverse rotation cams for ALL Saito engines.

Just pick the right engines, and the right parts, you have counter rotation on your plane.

Bill.

You don't need counter rotating engines in the first place. The Only Full sized airplane in WWII that had counter rotating frops was the P38. Every other one rotated in the same direction. You can't reverse the front housing and back plate on the old OS FSR's. The bolt holes aren't as deep on the rear cover. Even if you could it would still rotate in the same direction. Timing is controled by the crankshaft. You can turn the front housing 90 degrees in the direction of ratation and the engine will run backwards but with a power loss. Best bet is to buy a reverse crankshaft.

I haven't looked recently for modern engines, but the reason it hasn't been done in the past is because the cylinder center line is offset so that the power stroke is straighter so there is less side thrust on the piston, thus creating less cylinder wear.

If the engine is reversed, this offset would be in the wrong direction, thus increasing the wear.

-David C.

David:

What you are describing is the deSaxe cylinder design, not common at all in model engines. Fox was one of the few who did use it at one time, but I don't think any current engines from any maker use it now.

Bill.

Fox was the only modern engine manufacturer to use deSaxe cylinder design. No other manufacturer uses it today.

Bill,

I wasn't sure about that, but I will take your words as being right. You normally are!



David C.

For a 2-cycle engine there are several ways to make it work. The easiest is to use the reverse pitch prop. For an engine with a fixed front housing a reverse rotation crankshaft would be the next choice.

For a removable front housing engine(Enya), as Jen says, rotate the front 90 degrees left (from the front). If the engine has a rear intake, that would be 90 degrees right. Just make sure the intake opens as the piston is going up.

Swapping the front and back (per OS-FSR) would merely reverse the exhaust. For that engine just rotate the intake 90 degrees.

Using a reverse pitch prop is not the best choice since all model engines (AFAIK) have the thrust bearing surface between the front surface of the crank web and the crankcase (or crankshaft housing). Using a reverse pitch prop puts the load on the BB's or the thrust washer to crankcase surface (often separated by a washer).

George

I ran a canard pushed many years ago, about 1976, with an OS .60 Gold Head. I rotated the front housing 90 degrees in the direction of prop rotation and the timing reversed. I will say that it ran OK, but not as fast as it did in the normal configuration. I ran a normal, tractor prop reversed, front-to-back.

By the way, you also have to reverse your starter.

Guess I will have to start shopping for a counter rotating chicken stick!

SP:

Just buy a chicken stick designed for left handed people. When you use it in your right hanf it's automatically reversed.

Haw.

Bill.

HP and Merco also used Desaxe desin in some of there engines. Get a copy of David Gierke's book, The Two-Stroke Glow Engine. A "reverse" pitch prop is called a PUSHER and a standard prop is called a TRACTOR.

A simpler & cheaper way for both the manufacturer & the customer would be to have a rear intake controlled with a drum or a Zimmerman disc valve. Then all you would have to do is remove the backplate and change the disc to one which is timed for reverse rotation.