Geared Drives

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BoeveP51

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"Bud Warren- I get the impression that these are automotive components being used for the clutch drive. No known engineering analysis, seems risky to me."

Bud's clutch assembly is not automotive. His design totally. Before making assumptions I would recommend you talk with him and then form an opinion.

PS: I don't have Bud's unit, I have a Geschwender. But if I were out looking then Bud's unit would be first on my list.

Merle
 

orion

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I know or have researched some of these, some more in depth than others - I'll just make a few comments where I'm somewhat familiar with the design or program.

Geschwender- hy-vo chain design, out of production. Also I find it difficult to trust a chain.
Probably the best designed and most robust drive out there - too bad retirement pretty much put the business out to pasture. Silent chain drives are probably the toughest and least prone to failure out there but they do have very specific design requirements which when not met properly could lead to short chain lives. But then this holds true for gears also.

The chain selection must be made specific to the design condition since these components do have limitations on surface speeds. In my work though I've found fine pitch chains that can handle even a Mazda's 6,000 rpm plus environment quite well so choice is not a limiting factor here.


EPI- their first design failed in service. maybe the redesign will work as planned.
At first glance this seems a very professionally built product. However, reading the myriads of pages at the web site, little details start coming out, details that seem to reveal that the author may not be as familiar with his subject matter as the prolific wordiness might suggest. The best example of this is the discussion of torsional vibration, where certain statements and omissions suggest that the author may not necessarily understand the problem.

Cam- drive- I have no idea what happened with this organization.
Another good company gone due to retirement. I met the owner/engineer some years back and was very impressed with his understanding of the flight issues and his engineering approach. This was a very good product - too bad no-one seems to be willing to pick it up and run with it.

Precision aero- suitability and availability of unit unknown
Wasn't this the belt drive that was developed and produced here in Washington State? Although I didn't like some of the details, the overall product was well made and with a bit of refinement, could have been a real contender in the market. First the company was producing redrive and engine packages and then later, just the redrives. But yes, eventually I think it just folded up - I haven't heard from the owner in years.

Bud Warren- I get the impression that these are automotive components being used for the clutch drive. No known engineering analysis, seems risky to me.
Don't have any first hand experience with this one however, looking at the cases he designs, I'd say that he does not take any account of the flight loads developed by the prop and thus provides no reasonable load paths for those loads to smoothly get resolved in the engine case or engine mount. The Subaru case is downright awful - the drive mechanism looks OK but I wouldn't fly behind it. The V-8 housing does not seem any better.

Vesta- I will have to see what they have available.
Another redrive that is simply inadequate for properly handling the flight loads. Here though it seems like they might have an idea of the problem so they made all the components out of a massive plate so some stability is possible. But personally, I'd still consider this to be a poor design.
 

flywulf

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Dec 22, 2008
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I know or have researched some of these, some more in depth than others - I'll just make a few comments where I'm somewhat familiar with the design or program.



Probably the best designed and most robust drive out there - too bad retirement pretty much put the business out to pasture. Silent chain drives are probably the toughest and least prone to failure out there but they do have very specific design requirements which when not met properly could lead to short chain lives. But then this holds true for gears also.

The chain selection must be made specific to the design condition since these components do have limitations on surface speeds. In my work though I've found fine pitch chains that can handle even a Mazda's 6,000 rpm plus environment quite well so choice is not a limiting factor here.

I am really surprised to hear you say that about chain drives. Is there an ideal HP range that can use a chain? I'm seeking 500-700 HP maybe 800 if I can get it from an auto conversion.




At first glance this seems a very professionally built product. However, reading the myriads of pages at the web site, little details start coming out, details that seem to reveal that the author may not be as familiar with his subject matter as the prolific wordiness might suggest. The best example of this is the discussion of torsional vibration, where certain statements and omissions suggest that the author may not necessarily understand the problem.

Yes to me I thought this was the best product available from the site. I'm surprised to find out about the past performance of their products.



Another good company gone due to retirement. I met the owner/engineer some years back and was very impressed with his understanding of the flight issues and his engineering approach. This was a very good product - too bad no-one seems to be willing to pick it up and run with it.

Why is it that the good always die young?



Wasn't this the belt drive that was developed and produced here in Washington State? Although I didn't like some of the details, the overall product was well made and with a bit of refinement, could have been a real contender in the market. First the company was producing redrive and engine packages and then later, just the redrives. But yes, eventually I think it just folded up - I haven't heard from the owner in years.

I thought it was the spur gear unit that was originally designed by Jim Stewart and now I believe it is being promoted by precision aero engineering of torrance ca. I should say I have no definate information on who owns this design now, but I believe it is the same as the unit used in the S-51 pictures I posted earlier.



Don't have any first hand experience with this one however, looking at the cases he designs, I'd say that he does not take any account of the flight loads developed by the prop and thus provides no reasonable load paths for those loads to smoothly get resolved in the engine case or engine mount. The Subaru case is downright awful - the drive mechanism looks OK but I wouldn't fly behind it. The V-8 housing does not seem any better.

I got the impression this is shade tree mechanizing at it finest.

Who is the engineer?



Another redrive that is simply inadequate for properly handling the flight loads. Here though it seems like they might have an idea of the problem so they made all the components out of a massive plate so some stability is possible. But personally, I'd still consider this to be a poor design.
Who is the engineer?

Are there any other units on or near the market?

Ed
 

MKIV

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Aug 19, 2009
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Will, look like fairly substantial belts, another design that had multiple belts found that if any one belt failed it was likely to takethe other/s with it, but with that open cavity below the chance of that happening would be reduced, however the actual shape of the a/c nose bowl would have some influence that as well.. be interesting to see how it pans out long term & what others say.

Jac.
 

pepsi71ocean

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Jan 31, 2009
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South New Jersey
be careful about the red drives, there were a couple of companies that made red-drives that were horrible and broke apart.

A good gearbox has more to do with harmonics and torque reversals then it does anything else.
 

flywulf

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Dec 22, 2008
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Los Angeles California USA
Bud's clutch assembly is not automotive. His design totally. Before making assumptions I would recommend you talk with him and then form an opinion.

PS: I don't have Bud's unit, I have a Geschwender. But if I were out looking then Bud's unit would be first on my list.

Merle[/quote]

My impression of his design are from reading his info on his web-site and viewing his published video clips. And yes it looks like automotive technology applied to aviation to me. Last time I checked the laws of physics hadn't been revised. I don't see that talking with the designer will change my opinion. Whether you agree with me or not. My impression of his work is formed from his published material. Once again it is just my personal opinion.

Ed
 

Rom

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Has there been a consideration of magnetic gears for use in a reduction unit?

Here is something of interest to look at: Infolytica » Gallery » Magnetic Gear

They would eliminate the need for torsional dampening.
Frictional heat would be eliminated. No energy loss due to heat.
No wearing parts except for the shaft and bearings; no gears and belts.

Mark
 

bmcj

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I've sometimes wondered if a reduction drive could be done with magnetic fields (or hydraulics). Another area I thought might be able to use magnets is in a steerable tailwheel with a magnetic "detente". A strong enough magnetic field could keep the wheel locked into the steering arm, but could be broken free to swivel with enough force.

P.S. - I think your magnetic compass would hate a magnetic redrive, not to mention the radios.
 

Rom

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P.S. - I think your magnetic compass would hate a magnetic redrive, not to mention the radios.
The starter and generator do not seem to have a strong affect on the compass or radio. The redrive would sit way out in front of the engine. The magnet field lines would be contained in a magnet gear the same as in an electric motor would I would think.
 

Dan Thomas

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Bud warren, IIRC, has been working on his redrive since I first read about it in the 1970s sometime. That's if my memory is correct. If he's been developing it that long there should be numerous successful Warren drives flying. Are there?

Dan
 

blainepga

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Queen Creek, AZ 85142
It's really difficult to make off the cuff judgments without getting in deeper in order to analyze the details of the reduction's components. But at the same time there are a few comments that can be made based on what's presented at the site.

1) Probably the first and foremost thing that strikes me is that the site claims the producer to be a very experienced machinist but does not mention anywhere his qualifications to design this rather critical component of the drive-train. There is no mention of engineering, his or anyone else's. As such, I doubt there was any serious work done on longevity calculations nor analysis for all the foreseeable flight loads. He seems to make the claim that static dyno testing and his so far short term installation on an Express is sufficient justification (not even close BTW) for the drive's reliability.

2) To me the drive incorporates some red flags. The chief of these is the fact that the drive's case (which handles all the flight loads) reacts the internal forces into the flat end plates (with sharp corners!). The potential of cracking due to fatigue (looks to be cast material) is significant since this configuration might develop substantial flexing as a result of off axis flight loads (gyroscopic and maneuvering loads).

3) The site presents several blanket statements that are made with no justification for the stance he takes. He seems to be of the opinion that planetary reductions and chain drives are insufficient for this application and that his spur drive is the only solution. This of course is not correct since any drive designed for the application and service environment should work well, regardless of the transfer mechanism. Even a cursory examination will show that a planetary drive for instance spreads the load over multiple contacts, thus reducing the tooth stresses, allowing for slightly smaller and lighter components. True, I too am a bit hesitant of drives that use automotive planetary clusters, but otherwise there is no practical reason why a single spur would be better than a planetary one if the latter were designed right. The same argument holds for silent chain drives - they are designed for service well within the rpm range of these engines and due to their configuration, they spread the contact load over many teeth, resulting generally in very durable mechanisms. Chain drives also tend to be quieter than many geared configurations but they can be heavier.

There are several other red flags here but the above is sufficient in my book just to pass this one by.

In my opinion, probably the best reduction drive for V-8s was developed by Mr. Geschwender. The drive business he developed is now for sale so I don't think any are available until they come up with a new owner, but this was one drive done right. You can look at some of his work at www.alternate-airpower.com.http://www.alternate-airpower.com.
Bud Warren was an engineer working for NASA. He has a history in drag racing and he had an inate mechanical knowledge. As an engineer, I was looking for some sort of reduction drive for my project and wasn't satisfied with most of what was out there. I met Bud at the Copperstate Flyin in Maricopa, AZ. What he explained to me about his unit lit a light buld in me. I am still hoping to install one of his PSRU's, but I'll have to wait until we know the status of his company. He and his daughter were killed on 5-7-2011. They were flying a customer plane to an airshow. He reported smoke in the cockpit just after takeoff.
The NTSB has not found anything wrong with the engine(LS2) or PSRU.
 

blainepga

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Bud and Warren and his daughter Phyllis were killed in a crash while in flight to an airshow in Temple,TX Saturday 05/07/2011. They were in a customer aircraft. After take off they radioed that there was smoke in the cockpit and declared an emergency. They attempted to return to the airport in Conroe, TX but came up a half mile short into a very wooded area. This plane carried one of Bud's Chevy V8 conversions with his PSRU. The NTSB in their preliminary investigation has indicated they had no found any indication of mechanical failure with the engine or PSRU. From witness descriptions the airplane was flying level and the engine was turning. The plane nosed up and stalled then came down. It caught fire on impact. It appears that they were overcome by smoke and lost conciousness.
 

blainepga

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The CAM series of PSRU's was purchased by Firewall Forward Aero Engines in Ontario, Canada. They produce and support the full product line including the CAM100, CAM125, CAM500. The 100 and 125 use a belt drive and are good up to 200hp. The 500 is a gear drive and good past what any sensible person could want. This company has many aircraft flying and the PSRU's have a good history for longevity.
 

TXFlyGuy

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From what I have read, this accident is a classic "stall" resulting from trying to stretch the glide just a bit too far. Same thing happened at our local airport a few years ago, although it was not smoke related. A P-51 Mustang had just lifted off and begun it's climbout when the engine lost power (totally or partially) and the owner-pilot attempted to turn back to the runway. The result was a stall and crash which destroyed both the P-51 and the pilot.

In the Geared-Drives case, it seems that this was not related to the powerplant.
 

blainepga

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Bud's company assets have been purchased by a gentleman near the Ft. Worth area. A new web site will be active in a few days. It is called AutoPSRU.

Blaine Anderson
 
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