P740 engine for gyroplane

Trackwelder

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Last night they quoted me a price 0f $3950 plus shipping, they hve a smaller 4 cylinder that has dual ignition I asked about the suitability of changing the ignition to that style and hve not heard back. I hve no Idea what shipping would cost, but the price compares favorably with a rotax 582 and is supposed to bolt to the same motor mounts, I really want 4 stroke thoug.
 

thomasant

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Redirve upside down.
Could you please explain this?

This engine's belt re-drive is similar to the Don Parham re-drive used on my tandem Air Command, as well as some RAF2000 re-drives, where the larger driven gear is on top.
 

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thomasant

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Sorry, but for the fixed-wingers who have to fit this under a traditional airplane cowl, and who are probably the target market, this is right-side up.
Paul,

We are talking about this engine installation in a pusher gyroplane. Please read the first few posts in the thread.

For those that have not read this thread from the beginning, I am in the process of installing this same engine in my single place build Gyroplane and will be doing the testing soon.

Birdy made a statement in his post that the re-drive is upside down (probably based on the gyroplane pictures posted in post #1)

All that I asked is for him to explain what he meant when he posted that it is "upside down". I tried to explain in my subsequent post how my Air Command tandem has a similar configuration of the re-drive.

I will be happy to get any views from anyone regarding this.

The reason I am asking is because if there is a potential problem with the re-drive the way it is, then it is better that I know about it at this stage of my build.
 

phantom

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the redrive and /or engine will work fine with the drive up,the way you have it or down but on most gyros it is best if you can have the prop down low on the engine,this puts the engine mass closer to the rotor for better stability, however if you have a heavy rotor and a rotax 377 on the head for a pre rotator prop up high on the engine would be best.

Norm
 

Mike484

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This is going on a Dominator, with the redrive up, it is close to CLT, with it down it will become LTL.
 

birdy

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Yes, i was refern to the one in the first post.
Simply up endn the redrive would do wunders for the TL.
 

thomasant

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Thanks for the responses.

My next issue is regarding the exhaust mounting. I believe that the length of tuned exhausts is very important for proper engine performance.

In post #1 of this thread, the exhausts are facing forwards to avoid contact with the prop. This configuration is undesirable for my build. I have three options:

1) Exhausts forward like in gyro in post #1
2) Exhausts sideways under the engine
3) Exhaust rearwards with attachment of 18 inch long pipes to keep them parallel to the rear keel. If shorter, they will contact the prop.

Sorry I do not have any pictures of 2 and 3

Any insight will be appreciated greatly. Thanks.
 

PanamaPaul

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We have lots of China made Motorcycles here in Panama, and the engines are always having problems, internal parts not heat treated correctly,etc.etc., an very hard to get parts for some models, personally I would be very wary of the engine, until tested for a good long time----good luck----just my observations---
 

MadMuz

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The exhausts will be matched length for the cylinder combustion volume, so you can cut and turn segments and re weld to change direction, but you probably cant add length before the chamber.... extending the tail pipe not so much of a problem, you just cant extend it just out of the exhaust port.
 

thomasant

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Thanks Murray. That is very good info. This rules out a rearward exhaust alignment along the rear keel by lengthening the front tube to lower the chamber. We were mistakenly thinking that extending the tube in front of the chamber could be done. This would obviously mess up the tuning effect.

This leaves me with either the forward option or the side by side option under the engine, by which I can keep the lengths correct, as specified by the manufacturer. Since my gyroplane is open frame, I may be able to do the forward exhaust configuration without it looking too bad. This will keep the lengths correct.

Regarding the quality of the engine, there aren't many parts on this engine and it is a risk I will have to take initially and see how it goes. All the testing will be done overhead the airfield. Thanks again for all the insight.
 

MadMuz

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You could look at having the pipe come straight down then bend forward at about 45 degrees and exit next to the keel under the seat, or have the left bank pipe come down and across under the engine stand exiting on the right side, then the right pipe crossing under the engine exiting on the left side?

I tried to show it in the pics... forward and down towards the front depends on what suspension you have in the way. If you want to cut and turn to change angle then weld, get a piece of exhaust pip and cut and turn that, to find out the correct angle, before you cut the actual exhaust. If you don't get the angle right first time, you will end up with many cuts and welds trying to fix it, so do some experimental cut and turn segments on waste pipe first:cool:
 

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thomasant

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Excellent suggestions. Since I do not have an enclosure, I think the simplest to try first will be the forward configuration. Thanks a lot.
 

Mike484

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Tony, I like the way the first picture is shown, just cut the pipes, turn them to run under the engine, then re-weld them. I will be easier to make some sort of support so that all the weight isn't hanging from the engine.
 

MadMuz

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That's right Tony, but they will have to be bent down from 90 degreess to about 45 degrees... when he works out the angle of the slices to change the angle and does it, the outlet tips will probably be pointing in the wrong direction as well, so they will have to be cut and repositioned .... probably out to the side and down, not straight down, the exhaust blast might pick up rocks when taxying and damage the props.

A good test for finding the angle to cut, to see what the outcome is once turning the 2 segments, is to use the cardboard core of bog rolls or kitchen paper towel rolls.... once the angle is known, then cut the exhaust....
 

Vance

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Lots of options!

Lots of options!

A long time ago we built pipes for two strokes at Williams manufacturing.

We discovered on the dynamometer that we could run the outlets from the middle of the chamber without affecting performance.

I am sorry I don’t have a picture of our four cylinder Yamaha TZ750 powered road racing sidecar because it looked like a bundle of snakes that had recently enjoyed a big meal.

There are lots of options with a two stroke exhaust.

Thank you, Vance
 

thomasant

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Thanks for all the responses and great ideas, Murray and Vance. Mike, I will try the "under the engine" configuration out this Saturday. Hope Keith and Chauncey will be there
 

MadMuz

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I wonder if you could find some flex exhaust and cut the pipe and replace a section with the flex pipe? (like jap cars from manifold to pipe).... that would save cutting and segmenting and re welding, and would help with vibration and cracking of exhausts? Would be easier to mount the pipe, and let the motor and pipe be able to move separately?

Would make the job pretty easy?
 

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