Little Wing Yamaha Engine Conversion info.

[mcbirdman]

At the urging of Brad Hawly, another Lw Builder, I am opening this thread to find out if there are an more LW projects getting built & aproaching that part where powerplant decisions need to be made.

Todd has located me an engine and I have been trying to figure out how to have the engine mounted so that it is close to thrustline and not have the bulk of the engine so high that it makes the cowling look wierd.

Brad is making CAD drawings of a proposed motor mount for Todd.

It is Brad and my hope to find some other builders of LW's out there that need to get this Yamaha power plant worked out for tractors. If you have something to offer this is the place where we can share and learn so we can start making it happen and remembering the details of how we got here.

We got to start somewhere.... Okay Brad, Now we have a place to go.....:)

[HobbyCAD]

James, Brad,

Attached some pictures of what I did with my first heli installation. I used 2 horizontal tubes, centralised between the upper and lower engine mounting lugs. Here are my dimensions, (I live in a metric world):

Look at picture of engine, with sump on the wooden base, the output shaft is 175mm high. Top of engine is 530mm high. The engine mounting ears horizontal spacing are 105mm each side of vertical centreline. High side is 340mm high, low side is 160mm high. Thus, the horizontal centre of the engine mountings is 250mm high, 75mm above the output shaft, the output shaft vertical center smack in the middle, between the 2 mounting ears horizontal separation.

I ran 2 horizontal beams in the middle of the vertical seperation, ie 90mm above the low side, 90mm below the high side. My beams are 90mm wider than the mounting ears, ie my horizontal beams are 390mm apart. Mounting ears were made with holes, 127mm between hole centers, thus mounting them at 45 degrees, one side up, one side down, they mated with the mounting holes on the engine.

Maybe this is of some help to you. I am also needing a redrive for my aircraft, I'm replacing a 90hp Norton with a Yamaha 130hp 3-cyl. Mine is going to be a pusher, you guy's need a tractor. What type of redrive are you planning on using, belt or gear. If it's belt, count me in, I'll share resources. I need to get a belt redrive done for my Sentinal aircraft.

If you need a picture of the engine mounted in this old frame, shout, I'll install it, and take a picture. Maybe you can use this symmetrical horizontal mounting tube configuration to do a firewall engine mount. If I mount the tubes closer together than 390mm, the angles get too steep, and the plates touch other engine components. To counter that, or to get a narrower fit, you have to mount one horizontal tube high, the other low.

Francois

[mcbirdman]

Hi Francois,

I don't have the engine yet because I am still trying to figure out a way to make it easier for Todd to know what we need. I have blueprints showing the centerline thrust but I was trying to figure out how to make the most of Todd's engine cage, adapted into a tractor.

Todd needed to know what we had in mind and the main thing for me was how high the engine would be with the geared reduction. I just didn't like it but it was going to have to be okay. I have belts on my VW and now I think I figured it out....After shredding 2 sets of used older "test" belts I realize how critical it is for belt tension to be set right. I do not have a tensioner pully and new versions of the Valley Engineering drive does... which says something to me....

So... In order to get the installation centerline thrust and keeping the engine within the normal shape of the cowling..... Belt drive is needed.

I'll post some photos that I have found into this thread to keep the information in one place. I guess now is as good as any to start figuring this out. I do not have an engine here to put my hands on which makes it difficult to do much. I still have to pay Todd bal. on engine and to pull it. That is the easier part. Knowing what to have Todd make for the front plates portion of his cage is what we have to figure out.

I think that there are a lot of tractor installs that would benefit from the availability of such a drive configuration. I'm glad you're "in".

[mcbirdman]

I'll see what else I have that I can put into this thread/folder. I remember in another thread Todd saying that his cage pushes on a pusher against the mast and that with a tractor it would have to be modified. I like that Todd mated the engine to redrive to motor making the yamaha a reality for the LW. If the belt drive could be used instead it would be like icing on the cake. I wouldn't have a bump on the top of the cowl and with his clutch system I think the belt issues would not be an issue.

There has been two issues with the LW. One WAS an affordable, reliable higher output engine and the other is a builder who will invest much more time building. ... Someone who loves the beauty of the design and it's capabilities wouldn't really be discouraged from the build time which is less than a FW project. I look at is like yes it is a big project but I don't even have to make the wings....

Todd took a giant step forward regarding powerplant issues and now I am hoping someone more capable than I be able to figure this out. For the right person who's passion is machining it isn't that hard. I for one would help pay for the time getting it made if we had a few people interested. Or even commit to a few from Todd. I know he can't make any money in one off's so here we are... I really think that if he had one available it wouldn't be just gyro people ordering the belt drive yamaha conversion package from him.

The problem is that I am not a machinist although I can, with a little help from a friend fabricate from drawings. If there isn't enough interest in laying out the belt redrive system then at least Todd has already has another option and I will end up with the bump cowl. I would much rather have a second generation plate from Todd though...

[Racer]

Good thread James and Brad and thank you Francois for your input and pics as well.
I will be watching and taking into consideration of everyones ideas and try to come up with a solution for all tractor designs both for fixed wing and rotorcraft.
How strong are your firewalls? Could bracing be constructed behind the firewall for support? Could I modify the mast clamp to be a fifth mount instead of a clamp that would bolt to the fire wall?
Just a thought.
Todd

[HobbyCAD]

Hi there,

A question to the power transfer guy's, if I use an 8mm x 50mm Gates belt, how many teeth should be gripping around the small driven pulley? If I need say, a 3:1 reduction, with 27 and 81 toothed pulleys, I'm trying to determine how far must they be apart. The closer they come, the wider the wrap angle becomes around the smaller driven pulley, contacting less teeth. I'm trying to get at least 120hp transferred.

Does one absolutely need an additional belt tensioner? If the mechanical design is done well, with the belt pulleys running between a front and back plate, i.e. no shaft bending under load, and the tension is "perfect", once the belt is heated up, can one omit the tensioner?

You guy's flying the Yamaha's, what is the sweetspot engine RPM, that you can fly along with, all day long? What is the take-off engine RPM? I'm wanting typically max 2500 prop RPM, need to know the best reduction ratio to go for. What prop RPM are you guy's running, at what diameter?

Regarding resonances, what are the recommendations, regarding calculating the ratios. I have a 3 cylinder, running a 3 blader MTv7 prop, and wanting around a 3:1 reduction ratio. How do I stagger things, to not get all these impulses in resonance?

Francois

[Not Yet]

I do not have a tensioner pully and new versions of the Valley Engineering drive does...

The Valley Engineering drive is now using a poly-V belt (think superpintine) not a toothed belt.

In my opinion, much better for absorbing torque pulses.

[HobbyCAD]

Is the Valley Engineering addition of the belt tensioner in their latest redrives due to them switching to poly-V, rather than toothed belt?

Francois

[Not Yet]

I would guess so, but I don’t know for sure.

I would not use any kind of toothed belt for a redrive, as they were designed to be a very positive drive. No give like the rubber donut in some geared redrives.

[Jason O]

I cruise my Yamaha 120 between 6500 and 7000 RPM depending on how much of a hurry I am in.

Jason


Hi there,

A question to the power transfer guy's, if I use an 8mm x 50mm Gates belt, how many teeth should be gripping around the small driven pulley? If I need say, a 3:1 reduction, with 27 and 81 toothed pulleys, I'm trying to determine how far must they be apart. The closer they come, the wider the wrap angle becomes around the smaller driven pulley, contacting less teeth. I'm trying to get at least 120hp transferred.

Does one absolutely need an additional belt tensioner? If the mechanical design is done well, with the belt pulleys running between a front and back plate, i.e. no shaft bending under load, and the tension is "perfect", once the belt is heated up, can one omit the tensioner?

You guy's flying the Yamaha's, what is the sweetspot engine RPM, that you can fly along with, all day long? What is the take-off engine RPM? I'm wanting typically max 2500 prop RPM, need to know the best reduction ratio to go for. What prop RPM are you guy's running, at what diameter?

Regarding resonances, what are the recommendations, regarding calculating the ratios. I have a 3 cylinder, running a 3 blader MTv7 prop, and wanting around a 3:1 reduction ratio. How do I stagger things, to not get all these impulses in resonance?

Francois

[StanFoster]

James- Good luck on your Yamaha conversion. Definately an interesting project. You are a "doer" and you have chosen a most excellent person..Todd.. to have help make this happen. I will look forward to seeing it fly again at Mentone. Stan

[brett s]

Can that redrive be flipped without too much re-engineering? Seems like that would go a long way toward making it fit better.

[B Hawley]

Dear Forum members, I have not contributed much over the years, I relinquish that to others that have far more experience than me. Better to observe and learn. But now is the time to ask questions and propose solutions. Hopefully my questions are similar to others. As with any “New” aircraft and engine combination there will be different approaches to achieve the same end result. My hope is that through cooperation and the exchange of ideas all builders, thinking of configuring the Yamaha 120 or 130FI engine for use in the Little Wing 4 or 5, can produce a truly great combination.
Todd is on the forefront of developing these engines in the pusher geometry. These two engines are in the weight, size and horse power ranges to be applicable to many single and tandem tractor applications. Both will need a reduction drive unit. Todd has shown that the 120 can be interfaced with a gear reduction unit. Can we see something similar for the 130FI. Can these redrives address the higher position needed for the centerline of thrust within a pusher cowling, compared to a pusher gyro? I have found a European source that will produce a belt reduction drive unit for the 130FI.
I am asking for the calibration of builders and want to be builders, to think about and assist in the engine mount design for these two engines in a tractor configuration with redrives. What can be developed here, by this group, and be applied to both gyro and fixed wings. So I invite all willing, to submit information on use, design ideas, experience with and troughs with any suggestions. Synergy is the key to improvements and design innovations.
Attached below are four pictures, two first round designs of tractor engine mounts for the Yamaha 130FI. Both designs include forward sections of the mount specifically for the attachment of a belt reduction drive rear backing plate.
Brad Hawley
Grass Valley, Northern California

[scottessex]

How about a Raven redrive? (http://www.raven-rotor.com/html/redrive.html)

Not trying to take anything away from Todd but theses guys specialize in the belt redrive.

[GyroRon]

Can that redrive be flipped without too much re-engineering? Seems like that would go a long way toward making it fit better.

Yes it can and matter of fact, Racer prefers to mount the gearbox in the up position.... not the down position I wanted for my dominator set up. I think McBirdman is worried about something that is easily fixed by simply putting the redrive in the up position.

Also the " Cage " that Racer makes it NOT for mounting the engine to the airframe, but for supporting the gearbox and transfering the loads from the gearbox through the engine. The engine has 4 rubber isolated built in mounting points, two low ones on one side and two high ones on the other. All McBirdman and Racer need to do it to take a bed mount frame like he posted a picture of and modify it to reach up and grab those mounting points. Simple as pie.

Will it fit under the cowl? I don't know. It would not be a big concern to me, I would just want a good engine on the front and finally see the darn thing fly already!

[mcbirdman]

Thanks Todd, I am trying to get back into it - we are soo close.... It was Brad who kept at me to open this up and see what we can do. If we can work out the belt drive design it may be viable to produce and to a great many more people. Whatever this group can do now may well change the things regarding engine of choice for power, cost and reliability. Hopefully there is enough talent here and interest to make this work for you, and us. Thanks for your help to get us this far and for your valuable contribution that has sparked so much interest.

David, you picked right up on the V Belt change that I was pointing towards. I have a toothed gate belt ( no tensioner ). I believe Valley Eng. thinking was exactly that about power pulses on their 3rd generation redrive.

Brad, thanks for posting the drawings. I didn't want to assume it would be okay.

The thing that bothers me with toothed belts is that it is better to be too tight than too loose because the belt can climb up on the teeth and actually overtighten and bust the belt. Then, to keep it tight the directions are calculated to so much deflection per lbs of force and the information is just hard to apply consistantly. I figure at least with a belt that slips a little it doesn't throw all the teeth and with an idler it should help keep tension proper. I know that they use a one way idler wheel to help with the pulses. They are also turning a much lower RPM and I think the gates toothed belts are for slower RPM but I could be wrong on this.
Thanks Stan, this is getting more exciting. If I had a powerplant available a few years ago I would have spent the bulk of my time building rather than spinning wrenches/tweaking the powerplant. I am trying to keep "doing". :) I did get the redrive installed, figured out, a primer installed which makes all the difference getting an updraft carb with a big prop on a cold engine going. That is hard on the belts. I also got the left window installed and the right door. The right door has a lock, a latch and the door is dutch in that If I remove two pull pins and a clamp handle, the windshield portion comes off. Definately nice to be able to lock it up.

Anyway, I hope with all this talent here we gyro people can actually put a "positive spin" on the FW builders. :) :)

Todd, I will try to get you photos but to answer quickly there is a very strong firewall. What you see behind the sheet metal would be tubing in the shape of a square with mounting points at each corner There is other bracing involved but basically the sides of the fuselage are heated and bent towards the center of the aircraft becoming part of the square. I know it's easier to see so I will post something for you.

[mcbirdman]

Hi Ron, I did those photo sketches and could not determine if I was off much or not in the amount turning up the redrive would help. It seemed like it still had a lot of engine sticking up. You got it right though I felt that if that is what it had to be to fly - I already have it on the other one and it isn't that strange looking. I just wanted enough power to make it fly.
I am still a little afraid of belts though but see that proper design probably makes this a non issue. That cool clutch drive I think solves what I have seen to be hard on belts.

There are a lot of planes out there that probably really would benefit from belt drives. I would rather see what come out instead of jumping on a gear drive knowing it is likely not going to be the design of choice in the future. That is.... unless there is a reliability issue that can't be overcome using belts.......

[Alan_Cheatham]

How strong are your firewalls? Could bracing be constructed behind the firewall for support? Could I modify the mast clamp to be a fifth mount instead of a clamp that would bolt to the fire wall?
Just a thought.
Todd

Ron Herron has said that the maximum engine package weight on the LittleWing should not exceed 225 lbs. but I have no idea if he did any structural analysis to support that claim, it's airframe is after all based on an ultralight.

.

[WHY]

I,m not sure but I think this 225 ibs may have something to do with weight and balance as well. This is for both in the air and on the ground.

Tony

[HobbyCAD]

Hi There Brad,

You can count on my support, to combine forces for a 130FI belt redrive design. I am just about to be able to assist with manufacturing components, I've just bought a SERIOUSLY LARGE CNC Router. I'll be able to router out components, to 0.01mm precision.

I have a 130FI engine in hand, and about to receive a second one. First one is for my heli, the second for my Sentinal aircraft. I'm very keen to get this aircraft going. It was placed into storage a couple of years ago, I've now aquired it, as well as a slightly corroded spare fusealge, moved them to my personal hangar, ready to start the restoration.

Attached some pictures of the Sentinal engine mounts. One one picture, you see a larger Seeker dynafocal engine mount, attached to the airframe. The Sentinal uses the same airframe mountings, as the Seeker. Next pictures show the area where the Yamaha must install. I have enough space down low. I will have to adapt your proposed firewall mounting frame, and have them mate up with the Sentinal airframe mountings. You can clearly see the mountings on the corroded frame. Last picture is of the Sentinal cabin, nice and roomy, a SUPER all-around view. I'm very excited to get the old baby flying again.

I got the original drawings today, still on old floppy disk !! Now how am I going to get those printed out !!

Francois

[HobbyCAD]

Both designs include forward sections of the mount specifically for the attachment of a belt reduction drive rear backing plate.

Brad, as Ron said, the engine has 4 rubber isolation mounts already fitted. Looking at your proposed firewall mounting, you are mounting the engine in your cradle, via the rubber mounts. It seems you are hard mounting the reduction drive backing plate to the engine cradle. How are you going to mount the engine to the reduction drive backing plate? Should those 2 not be hard mounted together. I agree with Ron, you need to support the reduction drive backing plate to the engine, in one or other way, the 4 rubber isolation mounts are good enough to transmit the thrust load into the engine cradle.

Your comments?

Francois

[HobbyCAD]

I cruise my Yamaha 120 between 6500 and 7000 RPM depending on how much of a hurry I am in.

Thanks for the info, Jason.

Ron and Todd, you guy's have been flying your gyro's with Yammie engines installed, for a while now, would you care to share your WOT and Cruise Engine and Prop RPM's with us?

Thanks, Francois

[GyroRon]

WOT I am turning 8000 rpms loaded, and around 8300 as I get closer to 100 mph.

Crusie is about 6500-7000 solo, and possibly another 1-200 rpms more if I have a heavy passenger.

You do the math on the prop rpms, I am using a 3.47 to 1 ratio

[Alan_Cheatham]

I,m not sure but I think this 225 ibs may have something to do with weight and balance as well. This is for both in the air and on the ground.

I think the 225 lbs number comes from Herron's installation of the Rotec radial engine which he has said is the heaviest engine one would want to install. Note too that this is LW-3, the longer version of the LittleWings, if looking for an engine package weight for the shorter LW-5 I would base it's weight on the Rotax 914 install on Andy Keech's Woodstock, otherwise you may end up with C.G. issues.

.

[HobbyCAD]

Ron, Thanks for the RPM numbers !!

[mcbirdman]

Actually, the way I was told was that if the engine weighed over 200 lbs the landing gear had to be relocated about 2 inches forward from normal position to blance how heavy nose is and ground handling. Not a major problem but one that I see is that the brackets could not just be slid forward on longerons because it is just forward of that position the longerons bend upwards as they make their turn up to the square firewall box in the front. Not a big deal but lengthened brackets had to be fit and care made to not end up making your axles toe in or out too much. That's how I remember it anyway...

[GyroRon]

Well you don't have to worry about that anyway, cause the Yamaha package comes in well under 200 lbs, redrive and prop included.

[B Hawley]

Again I am just asking questions and sharing what I have heard. First of all Ron told me 240lbs max firewall forward total weight for the LW5. He mentioned that there are over 300 sets of plans out there, most likely 50 to 75 under construction and around 15 ready to fly or flying. So there should be plenty of builder / flyers out there. Maybe the ones currently building or flying would like to chime in with name and location, at least?
This has been a tough last couple of years. Having a family man means things always come up, priorities change and I’m on a budget like a lot these days. Things are not getting cheaper and my income has not improved lately.
With this project, safety has always first, but Cost is a close second.
What I and others would like to know is what type of redrive unit, how to mount the engine and how to safely combine all within a tractor cowling with proper cooling, efficiency, graceful lines at the best cost.
- Gear reduction unit:
o I understand Todd’s can be rotated 180 degrees from the pusher gyro configuration shown on this forum. That would solve most if not all of the centerline of thrust verses cowling fit profile.
o Cost, what is an estimate for a 130FI gear reduction unit?
- Belt reduction unit:
o I emailed quite a few redrive manufactures about the Yamaha 130FI engine. I even looked into airboat companies to spur some new market interest.
o I only had one company favorably respond with interest. This was a European belt reduction drive manufacturer named Aerotech Poland. Their web site is http://www.aerotech-poland.com/
o They recommended a ratio for the rpm range / hp curve of the 130FI, of 2.23:1.
o They have calculated the center to center dimensions of the crank pulley wheel to Prop pulley wheel, @ 2.23:1 ratio and gave me the following choices.
 213.25 mm (for the belt 880 mm long) 8.4” center to center
 233.85 mm (for the belt 920 mm long) 9.21” center to center
 274.77 mm (for the belt 1000 mm long) 10.82” center to center
o The CAD’s I made are from the measurements off my 130FI and my LW5 firewall. With the required thrust line location and the need for the engine to be angled downwards at 3 degrees, the top of the engine is very high above the nose cowling. The 10.82” center to center option lowers the engine into a perfect position within the LW5 firewall profile.
o The Aerotech belt system was quoted around $700 without the rear backing plate. (No idler wheel mentioned or shown)
Vibration dampening
- Engine to engine mount frame, thru the four dampeners already on the engine sides.
- Redrive system to engine mount frame, hard bolted ??
- Engine to redrive system ??
Again without experience, my first thoughts were to hard bolt the redrive backing plate directly to the engine mount, no dampening. The engine crankshaft redrive pulley wheel would only protrude thru the redrive backing plate. The only connection from engine to redrive system would be thru the redrive belt. No pull on the engine, just torque transferred from engine to engine mount. Tell me the pros and cons, if more cons prevail, we’ll consider this brain storming and look elsewhere for a better solution,

As far as the airframe goes, the engine mounts via four .25” bolts. The way the frame is configured aft of the firewall it lends itself to being modified to except a fifth and sixth .25” bolt center at the top and bottom of the frame. I came up with two engine mount designs, they may be frowned upon, but it’s a starting point for discussion and development. The more stout of the two designs use all six points and therefore more diagonal bracing, the other more minimal design engine mount only uses the original, per plans, 4 points of attachment.
So here are several pieces of the puzzle. I am hoping that as a group, with the love of flight and gyros in common, we, you all, all of us, can come up with a safe, affordable, basic solution that will provide a viable alternative to the outrageously expensive options out there.
I have attached some pics with a tape measure for scaling.
Brad H

[Jason O]

Hello all,
Here is the URL of the Yamaha 120 carbed version on my airplane. I have the gearbox turned up.

http://www.youtube.com/user/SidSlacker#p/a/u/2/RHYwVjGNZJc

With the fuel injected version, I think it would be useful to tilt the engine towards the intake side, that would put the top of the engine in the upper right corner of the cowling and the exhaust in the upper left corner of the cowl. You could compensate for the tilt by rotating the belt drive to center it in the cowl. I bet you could tilt the fuel injected version by 30 degrees and it wouldent know the difference.

[brett s]

Using a 2.23:1 reduction drive on an engine that likes to turn 8000+ rpm won't work well unless you're using a fairly small diameter prop, bad idea on something with the speed range (slow) of a gyro.

[Alan_Cheatham]

With the fuel injected version, I think it would be useful to tilt the engine towards the intake side, that would put the top of the engine in the upper right corner of the cowling and the exhaust in the upper left corner of the cowl. You could compensate for the tilt by rotating the belt drive to center it in the cowl. I bet you could tilt the fuel injected version by 30 degrees and it wouldent know the difference.

You need to be cautious about tilting any water-cooled engine as air bubbles in the cooling system must be able to purge out, otherwise you can have air pockets in the cylinder cooling jackets with detrimental results.

.

[HobbyCAD]

Alan, in it's stock snowmobile application, the engine is installed SERIOUSLY tilted, with the top of the carb horizontal. It was designed to run tilted.

Francois

[GyroRon]

I do not know why they would tell you to use that ratio..... that spins the prop WAY too fast. I went from 3 to 1 to 3.47 to 1 and it performs better with the 3.47 to 1 ratio.

[fiveboy]

I do not know why they would tell you to use that ratio..... that spins the prop WAY too fast. I went from 3 to 1 to 3.47 to 1 and it performs better with the 3.47 to 1 ratio.

Ron how does one make that conversion? Do you change things internally or just replace the whole thing with something else?

[GyroRon]

You can just replace the gears only, but it does take special tools. Better to send the gearbox off to have the gears swapped out, or make sure to order the right gears when you buy the box to start with

[mcbirdman]

Bringing in the link from Slipstream Industries. They have a belt redrive install and some info about what they are doing. Included a photograph so that it is here in this thread for future reference.

http://www.ultralightflyer.com/EAA_airventure_2005/yamaha-genesis_extreme.html

There is a video with some question answer talk. This may be old info from them but at the time, maybe still.... they are using the gates poly chain belts.
and they were testing the 3:1 ratio.

[PW_Plack]

Is that redrive up to the task of 120 HP? The smaller pulley, which if I understand correctly determines power handling capacity, looks a tad small for that much grunt.

[mcbirdman]

It may look small but the belt looks wide which has to increase the surface area to grip. Without going back to link and reading the info I think they used the Gates reccomendations and it is supposed to be good for up to 190 or so lbs h.p. The photo is months old and by now I am sure it if it works or not. I think that Ron is right that the 3:1 is still not quite enough for the rpms that are used.

What I find interesting is the metal straps that come down and engage the rubber engine mounts. They appear to hold the pully also and must have some sort of pully adjustment for tensioning the belt.

If we knew the gate pully sizes and the hardware bolt a non concentric spacer and a shelf to push off from and a slot in the faceplate we would be on our way..... Then again, if we are looking at V belts we still would a tensioner to figure out.

[GyroRon]

James, bear in mind that that engine is just mounted on the plane, there is no telling if it had even been started yet, much less flown. So until you know what they have done with it, it is just a picture of someones unproven ideas. I know the way Racer is putting the yamahas together is working, mines got over 60 hours on it so far and still going strong

[Vance]

It may look small but the belt looks wide which has to increase the surface area to grip. Without going back to link and reading the info I think they used the Gates reccomendations and it is supposed to be good for up to 190 or so lbs h.p.

Hello James,

If they used the Gates recommendation they wouldn’t be using a Gates belt on a PSRU.

Gates has long felt that their toothed belts are not well suited to driving a propeller on an aircraft.

I worked closely with the Gates engineers when I was at Indian motorcycles in Gilroy and discussed this at some length.

It is not just about liability.

Any time you have two flywheels quarreling with each other they feel that a synchronous belt is a poor choice unless there is a damper between them.

We discussed at length the many challenges with the RAF PSRU.

When Gates developed the belt primary drive for Harley Davidson motorcycles they designed a special dampener filled with special grease to replace Harley Davidson’s own compensator sprocket. This application was not successful and was discontinued after many warrantee challenges.

I feel it was cleaver of Todd to step around these challenges by using a gear PSRU.

Thank you, Vance

[raven-rotor]

Great info on the inside story behind Gates concerns with the use of cogged belts driving props. From the beginning we learned first hand the need to have a true dampening system as an integral part of all our belt redrives- particularly on the 3 cylinder engine which has a unique torsional resonance issue when driving a prop.

Don't think that gearboxes are not subject to the same loading as belt drives. A rubber donut only moves the resonant frequency up or down the operating range, it does not dampen torsionals. Only concern I have so far for all the great efforts to develop an affordable redrive conversion for the Yamaha sled engine is the use of a gearbox off the Rotax 582 as it appears in the other posts on this site. Two strokes hit twice as often and half as hard to develop the equivalent HP of a 4 stroke which makes them much easier on the drive train when hooked to a prop. Tell a Rotax engineer that you are planning on using their 582 75HP gearbox on a flying machine with a 120HP 4 stroke and they will probably have a definite opinion about long term reliability. IMO and 14 years time building redrives, take a look at the 912/912S Rotax gearbox to see what a real engineering group put together to handle a 100HP 4 stroke output and size accordingly.

Hope this helps.

Jeron Smith
Raven ReDrives Inc.

[B Hawley]

I’m very impressed with all of the input, and the experience behind it.
James and I still have some things to decide before we, or anyone wanting to use the 120 or 130FI in a tractor configuration, can continue.
- Is there a beefy enough gear redrive out there that can be used or converted?
(Not much on the front of the 120 or 130FI to attach a gear redrive to, unless
we adapt Todd’s design of mounting a gear redrive or alter for belt redrive.)
- Is anyone currently working on the above?
- What would be the projected cost?
- What do the people using belt redrives say about this?
- Could we use a V belt drive with ratcheting idler?
- What would be the Initial costs verses maintenance over a reasonable amount of time?
- Dampening
o Engine to mount provided nicely by the four rubber cushioned mounting points on the engine.
o Gear redrive to engine: Not much on the front of the 130FI to mount to.
o Belt redrive to engine: Again Not much on the front of the 130FI to mount to. Unless the belt redrive backing plate is attached to the engine mount.
 Belt redrive backing plate to engine? Again not much on the front of the 130FI to mount to. Can the belt be the only connection, between engine and belt redrive, or am I way off base?

Thanks all for the help, input and sharing information.
Brad Northern California

[RotoPlane]

This will give you an idea of how I'm setting up my belt drive. I could not find stock sheaves the size I wanted and cast-iron will not take the engines 6800 rpm or rim speed, so I've had to go with machining aluminum (for UL). For a maximum of 75 hp (short time) or 68 hp continuous, I needed to use seven 3vx Gates belts, with a 2.448 ratio. With your 120 hp, you should probably use 5L belts or possibly gear belts. You can zoom this .pdf to 800%.

[mercert]

Hi all,

I too am building a little wing, an LW5 single short and i have purchased a Yamaha 120hp to power it. I prefer to use a belt drive for weight and cost considerations. What we disire has been done before us, we just need their info to continue on our path. The guy in Norway or Finland that put a Yamaha on his Zenith zeniar CH601 has done what i desire, i have sent an email to Zenith hoping they can contact this guy and give him my info so we can hook up and i can pick his brain. Just by studying his photo i cold probably get where i want to go but his information would be nice to have.
With all the belt drives out there in use now i see the one used on CAM 100 as being the closest to what we littlewing builders are looking for. I will post if i get anything figured out or have contacted anyone who can shed light on our desires.

Tim Mercer

[B Hawley]

Has anyone out there come across any new installations of the Yamaha 120 or 130FI. The ones of us looking at a tractor configuration are still exploring the possibilities.
Any developments in
- Belt or Gear redrives?
- What are the cons of belt redrive backing plate bolted to the engine mount frame?
- What are the cons of belt redrive to engine dampening, through the belt of the belt redrive only?
- Has anyone wired up an Air-Tech dual strobe system to any of the Yamaha engines?

Brad H
Northern California

[25IDHOOKER]

I am currently going through the FEA on a tractor setup for a yamaha 130 hp engine, with a rotax gear box/auto flight gear box that is designed to be a bolt in replacement for aerovw, revmaster, GPAS vw engine, or anything that uses a deihl accessory case bolt pattern.

My mount use 4130 tube and the engine block as a stressed member of the frame to transmit thrust, gyroscopic loads due to precession, and torque to 4 mount points. My mount load ultimate strength is about 10 g vertical, 3.3 g lateral, 800 lbs of thrust, and gyroscopic moments about the yaw of 229 ft lbs, pitch moment of 574 ft lbs, and torque loads of 570 ft lbs. These loads include the safety margin in accordance with far 23 and far 33, in other words they are the max loads permitted on the frame before failure in any combination, not operational loads. I think the actual strength of my mount may actually be much higher then what I stated above.

I am currently in Iraq so all the dimension I have for the Yamaha 130fi are derived from photos, and some crude solid works models I found on the net. I believe I am within a quarter of an inch of accuracy on my model dimensions.

If anyone is interested in providing me with better measurements I would greatly appreciate it. My goal is to have all the structural analysis done before I return to the US.

[rkrisner]

Valley Engineering Belt Drive. I believe the Valley PSRU is using the poly v belts which are more flexible. This allows a couple of things, one is more wrap around the driving pulley, as the tensioner comes in on the slack side of the drive system and pushes the belt toward the centerline of the two pulleys. When the power pulse occurs and tries to drive the prop forward, some of the belt slack is 'let out' to smooth out the power pulse. I have one of these engine, and am interested in using it on an ultralight. I hear from a couple of people that they put out power like a rotax 503. The base GTH990 weighs ~100 pounds (with electric starter, without prop speed reduction unit). It puts out 64 #ft of torque at 3600 and 40 horspower at 4000 rpm (good direct drive option for a Gyrobee?? with a 60" prop?? But that is what I know about the belt drive on the GTH990 - which costs $1057, shipped to your door, or can be bought built with slightly higher compression pistons, 45 hp, for around $1800. New engine prices.

[rkrisner]

I fly fixed wing for now. I have a Hipps Superbird J3 Kitten, but really interested in a modded Gyrobee- for which I have most components, short of rotorblades

[25IDHOOKER]

engine frame that moves the yamaha 130 with rotax gearbox to the same thrust line as a direct drive vw and also uses the same deihl engine case mount points from gpas with conical rubber mounts

the frame was test load in ANSYS to 10g, 824 lbs of thrust, max p factor, torque, and a saftey facor of 3.

my estimated material cost is 200 dollars

if any one is intrested in helping me refine this design i would appreciate it, what i need is better dimensional data on the motor.

also intrested in doing a 150 yamaha just need dimensional data

[Jason O]

Hello,
I might be looking at your designs wrong, but it looks like the fire wall has the truss mounted to it and on the other end of the truss is the plate to mount the gearbox. How is the engine mounted to the truss? If you are mounting the engine to the truss using the stock yamaha rubber mounts, then I believe you should not mount the gearbox to the truss, you should mount it to the engine. The end result should be mounting the gearbox directly to the engine and then that whole assembly to the airframe using the engine mounts.

Jason

[25IDHOOKER]

you cant tell in the ansys model but I removed the stock rubber mounts and replaced them with solid bushing, vibrations are dealt with by lycoming conical rubber engine mounts at the back plate. The motor sits side ways with a modified oilpan and pickup. The gear box gets bolted to the front plate the engine is pinned into the truss by solid aluminum bushing. The engine in effect is fixed to the truss as one rigid assembly. The back plate bolts to the frame and the truss bolts to the back plate.

I have cad of all of this but I determined the spacing between the motor mounts by looking at some pictures of the engine with a tape measure infront from one of the threads on this board. I believe I am off by as much as 1/4 inch in accuracy, I would like some more accurate dimensional data for the engine if anyone can provide that information.

[25IDHOOKER]

I didn't mention this before but i priced the original material requirements from aircraft spruce to be around 200 dollars for the plate and truss

[rienk]

Alex,
I am very interested in your system, as it looks very much like what I have been considering as well. so many people have said that there is no place to mount the redrive to, but those mounts are perfect, and the give plenty of linear spacing. Your solution is elegant and simple.

That being said, I'm not sure I see where your prop centerline is going to be in relation to the top of the engine. Like some of the LW folks, I am interested in having the centerline be as close to the top as possible (necessitating a smaller top pulley?). I have modified a Generac for the "low-end" engine option for the plane we are developing (fixed wing... sorry... www.ayerscraft.com) and we built a nice redrive - but it uses a cogged belt - which we intend to change (though we may at least try it out first).
We want a larger engine option as well, thus the Yamaha.

By the way, a friend of mine designed and built a geared redrive for the Rotamax engine, but since the company is currently defunct (though they are trying to regroup), he has put the redrive on hold, right before he was getting ready to order castings (the prototype is machined billet). Though he's busy with several other projects right now, I hope to be able to talk to him about the viability of using his system with the Yamaha.

Anyway, if anyone wants to discuss this further with me on the forum or offline, I'd love to discuss it. I have someone else interested in helping with the design of a system for the Yamaha, but we are also looking at the 660 Suzuki as well (Arctic Cat).

[25IDHOOKER]

Rienk its hard to determine the centerline of the propeller from looking at the front plate, but its centered on the large hole on the front of the plate to the left if you look at my pic. A better idea of placing the centerline is to look at the conical mount points on the back plate(the cylinders that stick out of the back plate) and the intersection of all four at the center is the thrust line. I designed this mount to be a bolt in replacement for a vw aeroconversion with direct drive or crank driven propellers. I am fixed wing pilot for fun and crew and work on rotary for pay in the army. To be honest I hate rotary because of my interaction with it at work. The dumb things just shake themselves to bits and are a overly complicated, inelegant solution to flight, granted they do accomplish some remarkable things. I am just hating on rotary because I spend 12 to 14 hours a day working on them in a 140 degree weather. Secretly though I have designed my own 2 seater helicopters, but my current animosity towards rotary has prevented me from finishing the design work. I posted and joined the rwf to see if I could get some collaboration on this engine mount project while I was in Iraq. Sorry gyro guys no offense but your wings look like a bunch of scaffolding and chicken wire trying to hold themselves together in the air. I am not talking about the craftsmanship or finish quality just the overall appearance of a gyro, some of you guys have built some truly amazing machines and I applaud you for your efforts.

reink I actually have a 20 page design report on the mount and would love to be involved in some more aircraft design projects, I dont get alot of opportunity to flex my engineering degree in the army. If your interested in some more collaboration hit me up on pm.

I have a BSME with finite element analyses background and composite materials design.

[mcbirdman]

Just a note that to this point in time Little Wings using Yamaha engine have now either taken the direction of building a belt redrive like Brad Hawley or the geared reduction unit like Tim Mercer. Today I am opening a new thread to post photos from Tim regarding his installation photos sent to me. That thread will be called Little Wing Tim Mercer Yamaha Geared PRSU