Aluminum V-Belt Speed Reducer Ultra Light 'Auto' Engine 'Airplane' Propeller

The liability would scare me!

It would take me about 2 seconds to decline doing anything design related to an airplane. You could do a great job and then the guy could fly drunk and crash and you could loose everything you've got just because you are in litigious (sp?) America.

Pete Stanaitis

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Sunworshipper wrote:

They should have used a corvair engine- no speed reduction needed (apparently)!

Dave

Looks like a blower setup...

Dave

On 07/08/2010 03:30 PM, spaco wrote: (top posting fixed)

Yup. Back away slowly until he can't see you, then run like hell.

Not just because it's for a plane -- if I knew the guy already I might make a part or two. It's the fact that a couple of grooves in a pulley morphed into a design/engineering task -- that means that the guy is clueless, which means that you can't trust him to build the rest of the plane right.

(my spell checker thinks "litigious" is just fine).

My friend Chuck and I built a (roughly) 3/4 scale SE-5A (many years ago) that had a 3 cylinder Geo on it.

Chuck adapted a Rotax "B" box for it. That involved making a mount plate that fit the motor on one side and bossed in the box on the other. I recall a spacer on the box side to get the gears to mate up right, but no details now.

But he also turned down the flywheel to reduce weight. That's a common task on VWs and Subarus and can really help. But the Geo flywheel weight is directly proportional to engine life. It HAS to have the whole flywheel or the crank shaft breaks in 10 to 12 hours. It's a resonance issue related to 3 hole motors. And, yes, it broke in flight! Of course.

On a couple of other (2 and 4 cylinder) projects we used belts.

Don't bother with multiple V belts - it's not possible to get several close enough to the same size to work reliably. And when one goes, the rest are immediately overloaded and let go as well.

We never found a single V belt arrangement that worked well or was at all reliable. This on motors in the 50 to 80 hp range.

The best belt solution was the Gates PolyChain set up.

Home made wheels of aluminum worked ok, but hard anodizing is recommended. Chuck made a cutter for that odd rounded tooth pattern, and with a bit of practice, made some serviceable wheels.

One of the problem areas is the bottom (engine side) drive pulley. It needs to be as small as possible to keep the driven wheel from being too large, but small wheels cause higher tooth loads and wear rapidly.

Harmonic resonance issues require staying away from even numbered ratios. IE: 2:1 is horrible for resonance. 2.58:1 is much better! (Guitar players can explain this real well)

Hard learned lesson - don't loose your count on the gear cutter, and never EVER try to back up!

I've seen the Raven belt setup and was impressed.

Might want to explore the planetary gear boxes as the parts are smaller and generally available off the shelf. Excess weight on the nose of a very light airplane is a real killer. The airplane MUST balance properly to be at all controllable. Ballast on the tail may be necessary. Call it Static Stability Augmentation if anybody objects to "ballast".

But my heart-felt bottom-line advice would be to politely RUN (not walk) away from this kind of project.

Beyond the research and development (R&D = ReDo) is the legal liability in the event of a catastrophic failure.

As we have found out over the years, it's a no win situation...

Build your own if you want.

But be careful of the ramifications of building for others...

Respects,

Richard Lamb

Sunworshipper wrote:

Is the engine using a flywheel or is it using the prop. for a flywheel? A belt would take up the slack from a "driven and drive" vibration situation. A gear reducer has to stand up to that vibration

Bill K7NOM.

Hold the presses, we've got a great come back.

One of the first things I asked this guy was how big the back main journal is. I have ground aircraft cranks in a past life time.

Oh well thanks

Sounds like very good advice all around.

Wasn't there someone in this N.G. building an air boat, a while back, with exactly the same problems? Apparently successfully accomplished.

Cheers,

John D. Slocomb (jdslocombatgmail)

Ted Edwards put pictures of an aircraft speed reducer he fabricated (with a Smithy)in the dropbox.

Kevin Gallimore

Tim Wescott fired this volley in news:- _udnRIPBppowKvRnZ2dnUVZ snipped-for-privacy@web-ster.com:

You don't have to trust him to build the plane; it's an experimental. The _instant_ he puts a non-STC'd part on any aircraft, commercial or otherwise, it becomes an experimental aircraft.

I, too, would turn down the task because the guy didn't have specifications -- only hopes. But the liability risk is actually pretty small. NTSC doesn't have jurisdiction over experimental craft, and experimental pilots crack up all the time.

Of course, owners do all sorts of "custom" minor modifications to their commercial craft: instruments, decorations, minor fittings like latches and knobs. But the moment you modify the controls, the airframe, or the powerplant (this pulley) you're off the chart, and on your own. And this doesn't even seem to be a modification, but a build.

Mostly, I'd turn him down because he doesn't really know what he wants, and not being an A&P mechanic myself, _I_ don't know what he wants, either.

LLoyd (SEL pilot with about 1000 hours)

Great find, looks like they had the same problems I was thinking of.

SW

Recommend the airtrike gear-box. It is quality engineered - even if it IS made in Russia. The guy selling them knows his stuff and is very helpfull as well.

3 or 4 cyl Geo?? The 3 cyl needs the heavy flywheel, the 4 doesn't - making them the same weight over-all and the 4 is 30% more powerfull. - and a LOT smoother.

I woudn't use V belts - a properly set up toothed belt perhaps on a 4 cyl - but the gearbox with the BMW cush-drive is the best setup.

Not strictly true.

If it is on a certified plane, it becomes an ILLEGAL plane - but not an experimental.

Correct - but with starter, alternator, exhaust and intake 265 lbs is about "it"

But it's not the NTSC that brings liability suits. It's the relatives of the deceased, and the ambulance-chasers who find them.

My goodness, I feel like such a slacker now!

Jon

V belts seem to be time-tested on the Rotorway. Some info here

didn't realize that the belts were tied together in pairs. Anyway, it seems like most use toothed belts. Harder for an amateur to machine, but lighter and less friction than V belts I presume.

Wayne