Hello,

I am building an aircraft where the engine should produce thrust in the opposite direction. I can do this by inserting the propeller backwards and running the engine in the opposite direction. The engine is a 2-stroke SuperTigre 40? Should I expect the engine to run properly in this direction?

Thanks, David

The engines run counter clock wise.

Some older engines can be readily reversed. Others need a reversed crankshaft. This is rarely available any more.

It does work to turn the prop around backwards. You have to use a pusher prop and install it backwards

The Super Tiger GS 40 is not reversible.

Enjoy,

Jim

If you have an engine with a bolt on front bearing assembly, you can bolt that on at a 90 degree angle and it will be timed close enough to run backward. Sadly not many engines are made any more with bolt on front ends, the K&B .40 is the only one I can think of off had. But many older engines that can be bought off of this auction site and that other all purpose one.

K&B, Enya and some OS has fronthousing who can turn 90 degree and run reverse.. All engines with reed valve or sideport (inductiontiming controlled by piston) can run in both way.

Jens Eirik

I believe the correct orientation to determine crankshaft rotation is to be at the rear of the engine looking forward. At least this is what I was taught at A&P school and is the same in technical manuals.

That being said, to be technically correct the normal crank rotation of our little engines is clockwise. And you wish to find a way to make it run counter-clockwise.

The Enya SS series is the newer version with the removable front bearing housing. I had a Enya SS40BB for a few years. It had a removable front bearing housing.

The CX series has a one piece crankcase.

Enjoy,

Jim

Hi!
NO!
You need a different engine and a clock vise running prop. MVVS have engines with special clock vise running crankshaft (available for all MVVS engines).

Regards!
Jan K
Sweden

If you have a Ryobi weedwacker engine with electronic ignition--you just slide the timing ring over to the other side and change the prop for reverse running. Flip it the other way--it runs backwards.

Totally irrelevant to the topic, but I'm trying to up my post count. Makes me feel important.[sm=lol.gif]

I think you have been told a bunch of correct but confusing stuff. All you need to do is put a pusher prop on it. Pusher props are made to push rather than pull when running in the usual direction. Unfortunately, there are not as many sizes of pusher props as there are of tractor props. 10 x 6 pusher props are fairly common, however.

Hi!
Do you mean you want the engine to push air forward...? Or backward... if its in a pusher airplane with the engine at the rear.

Jan K

Hello, thanks for all the replies. I just passed by the hobby shop and they did have a pusher prop. It was 10x6 just as Tim said and it fits my engine perfectly. I've got one question though, why is the 10x6 pusher prop common?

Should be obvious, David. Fits the most common engine size.

Bill.

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Models and full size are two completely different animals when it comes to terminology, Kmot.

Our model engines run counterclockwise as determined by how you are looking at them when starting them.

You have to keep an eye on these full size critters, folks. They'll try to sneak in their terminology on you in a heartbeat. <G>

Although[sm=confused.gif][sm=confused.gif],,you know,,,,,,,,,I have tried starting my average engine and for some reason it will run backwards,,it especially happens when I use a chicken stick,,,,,I get so mad I wind up putting the electric starter on it ..,,,then its fine. Go figure?


TAZZZZ

Tazzz,


Nearly any two-stroke engine will run in the reverse direction, for a limited amount of time and only at low throttle setting...

Opening the throttle over 20% will either stop the engine, or will make it 'flip-over' and begin to run normally.
The crankshaft port timing allows this... High timing numbers that support high RPM power, also allow reverse running...

Four-stroke engines may do this too.

OK,,Iget it,,,your right it happens on my 4-strokes more than the others. Thanks---TAZZZZ[sm=biggrin.gif]

Running in reverse with a hand/chicken stick start is a symptom of over-priming. Just reduce the amount of prime you're giving it a little at a time until it always starts in the correct direction.

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But these are not full scale engines. That is a different field entirely. Modeling has its own customs and modelers judge the rotation of an engine from the front, which means that our engines run counter clockwise by tradition and all that is holy.

I'm picking on you Kmot. I used to tease Henry Haffke in this way many years ago. He was and is more of a modeler than I will ever be in this life time.


Ed Cregger

I don't think you can run any rotary valve (intake through the crank) backwards. A reed valve doesn't care, it will run in either direction. There are some Enyas you can rotate the front housing 90 degrees and run backwards with minimal affect on intake timing but I don't remember which model.

Bill

Frankly you model guys are driving me nuts, retailers and all. I was taught by a very knowledgeable man to always refer to engine rotation from the driver/pilot's seat.

Bill

David. I thought I would try to consolidate what everyones been saying.

First. You need two items to run a rotory valve engine in reverse.

1. a reverse crankshaft
and
2. a pusher prop that now pulls because the engine is rotating in reverse.

Second. Just turning around the front housing, not 90, but 180 does nothing as far as the rotation of the engine. The only benefit is that the engine exhausts on the opposite side.

Quote:

ORIGINAL: Ram Jet

I don't think you can run any rotary valve (intake through the crank) backwards. A reed valve doesn't care, it will run in either direction. There are some Enyas you can rotate the front housing 90 degrees and run backwards with minimal affect on intake timing but I don't remember which model.

Bill, RogueDog,


Yes, you can!

There previously were more engines that used a two-piece crankcase. Among them Webra .61 Speed/Racing (#1024/#1030F that still do), Moki, OS.61FSR and many, many others...

In those engines you could rotate the front part of the crankcase (which contains both bearings, the crankshaft and the carburettor) 90ΒΊ around the crankshaft (take note, RogueDog; not turning the cylinder around its vertical axis), which results in the carburettor 'relocation' to the right side of the front crankcase and the running rotation becomes counter-clockwise.

Also, only one thing needs to be done, unless another effect is desired...
For example; if you were to build a scale Piper PA-31-350 Navajo Chieftain, which has contra-rotating engines and props (to cancel the 'critical engine' effect), you will need to reverse the right-hand engine, by either rotating the front-crankcase, or using a contra-rotating crankshaft (with the intake port on its other side) AND to use a pusher prop, mounted as a puller, of identical size to that of the other engine's normal prop.

If you just need to reverse the engine, to have it installed as a pusher, in a Bobcat, for instance; you must only use a normal prop and it will work as a pusher prop.



Edit: Corrected after I got my directions reversed.... It is Batata-Bandura for me...

And from a modeler's perspective, full size aircraft pilots are a PITA to teach how to fly. Especially since they are absolutely convinced that they know everything and that they can fly a model airplane without instruction. They are not aware that over a century's worth of dumbing-down full size flight instruction to the point where anyone can get a license has removed all of the engineering knowledge that the early full size pilots had to learn. Or pay with their life for not learning in their primitive aircraft. Modelers are still stuck with having to learn the engineering if they design/build/fly their own aircraft. So how do you teach someone without engineering skills when they are convinced that they are superior to their lowly model instructor? I don't. Not my problem any longer.


Ed Cregger

I own and flew a Bob Cat running in reverse with an OS .45 and a Royal .46 by rotating the front housing. The intake timing changes less than 5 degrees. Standard props are used when running in reverse and pusher configuration. The purpose of running in reverse was to avoid difficult to find pusher props. Both engines preformed well.

Bill

Both engines were too small for the weight of the airplane but that is different story.

In the military it was easier. Being either a flight leader or section leader made it even easier because I could write them up to have them thrown out of flight school if they pushed me enough. A couple of bozos tried it. Rank didn't matter because they were students, and students were assumed to know hardly anything. Students never won a battle against the instructor pilots. The kiss of death for any student was to downgrade them on either aptitude or attitude.

I've been around a few of those types at the flying field. I usually say something once or twice, and then walk away from it if they don't listen when they asked for help. When it comes to the dangerous stuff, being a club officer helps.

The worst one I ran across was a student who had his license as a balloon pilot. Every single instructor was chomping at the bit to get him so they would document his demise. I took him myself, and just let him have all the rope he needed. He just kept on self destructing until it was too late. He was pretty much untrainable due to his superiority complex.