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Discussion in 'GEO / Suzuki' started by skip_hill, Feb 17, 2003.
Anyone building a GeO had any luck finding parts for a PSRU, besides buying the "gold plated ones?"
For a cog belt PRSU, you might try contacting Goodyear or Gates about their products. I think they both have cog belts and pulleys. However, they may not approve or support use of their belts for aircraft power transmision.
Years ago, I built a very successful PRSU for an ultralight I still own, using a 1-1/2" wide poly-V belt, machining my own pulleys. It had a cog belt & centrifugal clutch arrangement before that which had several problems: the clutch would slip; so I eliminated the clutch, then the rubber cogs would strip out in a very short time. With a piston engine, the power pulses must be accomadated somehow or something will break, sooner or later. Presently, I am building a Jenny replica and have bought a Geo metro engine to power it with. I have designed a PRSU using a 3- inch wide poly-V belt, a rear axle spindle from a Plymouth horizon car, a 5/8" thick aluminum plate that will bolt to the bell housing bolt locations via standoffs to clear the flywheel and some aluminum pulleys that I will machine myself. I will also incorporate an outboard ball bearing to eliminate overhang loads on the crankshaft. It is essentially a scaled-up version of the one I built years ago. If you are not familiar with what a "poly-V" belt is, it is the same as a serpentine belt used on new cars, except a lot wider. It allows the system to slip a tiny bit, easing the pulse loads. On the first PRSU I built back in the eighties, I bought 2 belts, to have one as a spare, I still have the first one on the machine, the second one hasn't has been used yet. I could probably send someone the drawings if they're interested and have access to a lathe.
Regarding the cog belts from Goodyear or Gates, years ago we looked at similar applications and started calling around for technical data. We quickly learned that in our search it was of paramount importance to never mention "aircraft" in the conversation as it was a good way to get hung up on. It turns out both companies have come out with very strong statements against the use of their products on aircraft and according to the communique passed on to us, anyone knowingly selling to an aircraft application could lose the product line and could actually face legal action and fines from the manufacturer.
As far as the reduction dirve itself is concerned, my recommendation here is simply "don't be cheap". This is one of the most critical components on your aircraft and trying to cut corners now could cost you later. Furthermore, by the time you do all the work in developing your own, unless you have your own machine shop and the technical ability to do the analysis and part manufacturing, you may end up spending a lot more than if you went out and bought one of the "gold plated ones" in the first place.
Personally I am not a fan of the "V" belt configurations. Yes, they are simple and forgiving and they do work. Also, they don't really have a catastrophic failure mode. But the power losses from the "V" contact are more than I like.
The cog belts do work (and are quite efficient) and there are quite a few units out there flying sucessfully. The trick is to use the proper model of the belt, sized with the proper safety factors. The structure of the drive must also be very rigid and accurate - the two items that makes the cogs fail more than anything else is the misalignment of the rotating components and the improper selection of the belt. Under normal conditions (even aircraft application), the power impulses of the engine, even a two stroke, should not cause a cog to fail unless the wrong belt was selected and/or the drive was improperly built or set up.
I am suprised to hear of the pulses doing damage to the belts. Harley Davidson has been using belts on the primary drive, and final, too. Is there an engine that pulses more than that? They are getting 30K miles on a belt, or more!
Good point however remember that the HD has a clutch between the engine and the drive. The clutch has an internal spring system that has the capacity to absorb the worst of the impulse and spread it out over a longer period. As such, the belt on the motorcycle does not see as high a load as one would encounter in a reduction drive where the small cog is mounted directly to the crankshaft of the engine.
Furthermore, also keep in mind that even in cruise, we require aircraft engines to output 75% or more of their rated power. The motorcycle application sees this power level only rarely since in cruise and normal putting around town, the motorcycel engine generates on average only about 30% of the rated power.
On the HD primary drive, the drive pulley is directly on the crankshaft, which in turn drives the clutch, to the tranny, and the final drive. This must be why the primary drive belt is 2.5"-3" wide
That is why they are so wide... and still only gettin 25k-40k out of them. The thing to remember on a belt psru is that not only are you drivin it directly off the crank on one end, but driving a propeller on the other. The combined pulses work together, and against each other, to destroy the belt that much faster. In a HD, the belt drives a tranny, with a clutch, that both act to isolate the final drive.
I have been having pretty good luck with a cog belt. I have been using one for over 100 hours. They are so cheap I will just chang them every 200 hours or so need it or not. The trick is to get the tension right.
Oh and by the way it's on a Harley engine on my airplane.
You can see it at www.hog-air.com
I can't understand how I've overlooked this thread, I was just on the verge of posting a question about the PRSU on the market myself and ask if any DIY plans or kits were avaliable to save money. Does anyone know if anything has changed in this direction over the last four year's? The Suzuki engine is looking very good to me at this time as they are very easy to obtain while still in excellent condition. In fact I've already had an individual offer to give me one. That doesn't happen to me very often.
I have built a Redrive for a three cylinder Suzukiu engine and I have some pix on my old website--
Lou Ross ( this name may not be important to you --but it IS) developed redrives for many engines --mostly planetary gear systems --and one for the 3 cyl suzuki. I spoke with him many times at his Tucson Az facility. He recommended to me that I build a belt drive for my conversion. The 3cyl Suzuki has some power pulses and harmonics that will totally destroy a gear redrive unless a pulse dampener of significant size is incorporated into the redrive-- dont believe me --well give it a try --been there done that --cost is prohibitive for a single unit setup--
A cog belt drive redrive will work but it must be set up right-- I have run mine for hundreds of hour at WOT with NO belt failure. There are however harmonic vibrations at 17 34 and 51 hundred RPMs --they are not violent but I would not recommend running for very long in those RPM ranges--Check out my Old Website for further info--http://members.cox.net/mls211/GEO.htm
Thank's for the information MMM, I did a search on Lou Ross and haven't found the correct person. Can you point me towards a link? Your websight was/is nice. I did find a link to an intresting gentleman who developed a PSRU from a car trannny and flew a lot of hours with the set up. He was selling a booklet on the set up but he passed away last year.
Lou Ross died several years ago and the company went Kaput!! I dont know of anybody (other than Raven Redrive) that makes a redrive for the Suzuki/Geo engines--
I am building a redrive for Suzuki 1.3B, with cogbelt using specilly made pulleys, a adapter plate to take the prop mounting pulley and am using Vassily's 3 blade,72" cool prop. Because i wanted the pulleys as close to the crankcase mountings, i have taken off the DISTRIBUTER from the present position on the cam shaft and have made a new system for ignition which will be mounted on the pulley of camshaft,using Honda motorcycle iginition pickups,ECU & twin lead ignition coils. The project is ALMOST complete except for the silencer and some minor points. The photos are posted along.
I'd like to see the plans and pictures of your PSRU Vasant as well as how the completed project turns out, it sounds intresting.
hey Jeff Would really appreciate a copy of the psru drawings I am Fitting a BMW R90S engine to a Texas Parasol my email is firstname.lastname@example.org
these are some of the photos from the PSRU i am completing on a carburetted Suzuki G 13 B. The ignition system is getting done in the next week and will have the photos attached once it is done
Cool... but why is the belt half off the crank cog?
Nice looking set up Vasant. How much do you have left to do before completion and what prop are you going to run? Also sent you a PM.
I plan for converting any of G engines for airplane use.
I would be thankful if you give me some info on the issue.
For example what engine rpm you are running at?,drive ratio,engine weight,and some photos on psru.
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