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Using motorcycle drive belts from BEHIND an engine

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RSD

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Don't ever say airplane around anyone from Gates or any of their suppliers. Say garden tractor.
Could you say Airboat? as then you could explain the same sort of use (driving a prop), HP, RPM range, etc etc.
 

wsimpso1

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As for the drive shaft I think you could get a bigger head start using a motor that already has a countershaft in the design (many 90deg engines need a countershaft to help reduce vibrations).
Please tell us which V-8's have balance shafts. I could not find references to balance shafts in any V8's. Lots of them in twins, inline fours, the old Ford V-4's, and odd fire V-6's, but not in V-8's. They are a great idea in inline threes too.

What many pushrod V-8's have running through the V is a camshaft, which runs at one-half crankshaft speed and it is not going anywhere - you need it to operate the valves...

This means that the block is already drilled for oil passages and the block ends already have a thick hunk of metal line bored for a sizable shaft.
Typical balance shafts are running at twice engine speed and do not have any other power drawn from them. They are designed with low power and high speed in mind, not engine output level power. Between gearing, bearings, front and rear housing redesign, sealing and shaft design this will be a major modification to the base engine plus the prop bearing, reduction drive, etc.

When I said that I thought the layshaft design would work, I was referring to a reduction drive attached to the RFOB, the shaft supported at the reduction drive and at the prop shaft bearing off the accessory end of the engine, and the intake manifold sharing space with the shaft above the base engine. This scheme of running the layshaft looks doable for driving a prop.

I still think an airboat drive that we already know works plus an electric prop is the way to go with a V-8.

Billski
 

choppergirl

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Why can't you use motorcycle sprockets and chain instead of belts, to drive a prop on an ultralight or homebuilt. I'm guessing the answer is to dampen vibration, but I'm starting to wonder if that's really a valid enough reason not to try an off the shelf motorcycle sproket and chain setup first that come in a million varieties and sizes instead of some cusome airplane belt drive setup that is through the roof.

I just received a replacement sprocket set for my 45hp motorcycle, and it seems awfully light and robust with holes cut out of it to make it even lighter, etc. A good portion of the chain that would be used on a bike is redudant and would not be used in a reduction drive on a plane. Plus, you've just got so may options to swap in different gear teeth counts for different ratios and so on, take out or add links and pieces of chain in, etc.

I saw one youtube video where a guy had adapted one for a really beefy engine on a trike, but it looked overkill.

I'm running right now with a severely shot out and loose chain, that pulses and tightens whenever the link is on a gear because it doesn't wear out out, and still the thing just keeps going and going. I've had a chain this insanely look jump off before, but I was in a sharp slow 180 degree turn. I know for sure if a belt was even half this loose, it would totally slip...
 

Jay Kempf

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Chains in the back of a cowl with good weather abatement strategies so they don't corrode could work as long as you deal with tension and damping somehow. Silent chains as used in 4x4 transfer cases would be ideal but should be in some sort of oil spray housing so maybe not light.

Cog belts don't corrode or run out of lube and they have some inherent damping characteristics. Stiff or soft drive strategy, either approach can work.

Not sure which would win the TBO contest. Probably silent chain with good damping idlers and spray lube. But that isn't going to be the lightest.
 

pictsidhe

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A chain drive is going to need very careful design to avoid TV issues. It would probably have to be a soft system, and probably needs a clutch. I did see some guy on youtube with a chain driven trike and he was utterly unaware of the severe stresses it was placing on things. It was painful to watch...
 

captainreychapin007

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I am planning installing a New Harley Davison Milwaukee 8 motor in aBD5 it’s 115 Cubes 100hp
Stock. Twin plugs, twin ignitions adjustable in flight injection, oil cooled heads internal balancers
It’s capable of up to 400 HP
Non turbo also twin car air bags ejection seat pipe wing spars with carbon fiber inserts fiberglass wing wraps looking for spars parts
I have extras to sell trade
 

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wsimpso1

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Were there TV issues?
During development they had plenty, and for a while the team thought the issues unsolvable. The article I cited earlier has a bunch of history on it. They ultimately fixed it for production. No one on the team even considered resonance at the outset. Some good Engineering from the beginning would have gotten them to marketway sooner. Of course they were still doomed by other issues....
Billski
 

Doggzilla

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I guess Im the only one who bothered to read it.

For those of you who didn't have time to read, the BD system ended up needing a freewheel clutch to avoid torsional vibration which was burning up clutches and belts.

It was something one of the machinists had seen on old belt drive farm equipment, so it wasn't some new high tech solution. It had already been solved very easily and with little weight decades earlier.
 

wsimpso1

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I guess Im the only one who bothered to read it.

For those of you who didn't have time to read, the BD system ended up needing a freewheel clutch to avoid torsional vibration which was burning up clutches and belts.

It was something one of the machinists had seen on old belt drive farm equipment, so it wasn't some new high tech solution. It had already been solved very easily and with little weight decades earlier.
There was also making the system quite soft torsionally so that its natural frequency was substantially lower than its idle firing frequency. IIRC, neither the OWC nor the low natural frequency were enough by themselves, but the combination made it work. The topic of vibration isolation and how to achieve it was already an old one when the BD-5 program came along.

Billski
 

Doggzilla

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There was also making the system quite soft torsionally so that its natural frequency was substantially lower than its idle firing frequency. IIRC, neither the OWC nor the low natural frequency were enough by themselves, but the combination made it work. The topic of vibration isolation and how to achieve it was already an old one when the BD-5 program came along.

Billski
Yes, but is still a good example of the behavior I have been trying to discuss lately.

The other engineers ignored him despite it being a known fact, and once they admitted the fact, it was not solved by an engineer, but a farm boy.

What if they had mocked him and told him off?
 

Sockmonkey

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IIRC the article about the BD-5 they mentioned that they might have solved most of the problem sooner if the belt had rounded rather than square teeth that kept trying to climb off the sprocket.
 

Riggerrob

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Has anyone looked at the PSRUs in airboats?

Auto-engine conversions save money at both ends of the scale: purchase and fuel consumption. The 300 horsepower Corvette engine conversion for Republic Seabee develops more horsepower for half the fuel consumption. That is the difference between a 1940s-vintage, air-cooled, carbureted, Franklin versus a 1990s-vintage, liquid-cooled, fuel-injected Detroit product.

But for the vast majority of homebuilders, the least expensive option is a half-life Lycoming or Continental.
 

cheapracer

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Please tell us which V-8's have balance shafts. .... not in V-8's.
One thing I have learnt about engines in my lifetime, is never say no engine did or had that. My dad was worse than me, I would go up to him with a brilliant new engine idea, and he would immediately cite the engine from the past that had done it already. I only ever stumped him once!

 
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