a couple questions for the VW crowd

Barney Bahle

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Jul 25, 2011
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483
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Crossville, TN 38571
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Rotorway 162F
First a little background. 1982 Bensen Gyroglider kit. The engine is supposed to be an 83 Great Plains 1835. 1985 Ken Brock VW conversion kit.

Does anyone recognize this prop hub? I don't see it available from Great Plains. Linda at Okeefe Aero (the original owners of Great Plains) thinks it's a HAPI. My main concern is what torque value to torque the hub bolt onto the crankshaft. Secondary concern is why does my GP VW have a HAPI prop hub?

Next question: Tennessee Propellers suggests a 52X28 for a 1800cc VW on a Gyro. The prop that came with the engine is a Brock 50X20. Any of you guys running a 50X20 on your VW? If not, what are you running?

I look forward to your expertise.
 

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gyrojake

Gyro Rehab Candidate
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Ken Brock used Hapi V.W. engines.
I used a 52x26 on my 1835 and ran at 3800 rpm max.
Then I when to a 54x24 and liked it better.
 

Barney Bahle

Junior Member
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Jul 25, 2011
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483
Location
Crossville, TN 38571
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Rotorway 162F
Thanks for the input Jake. Didn't know that about Brock using HAPI and that does explain a few other inconsistencies. There's always the possibility that the Great Plains info came from a different project. I just wish HAPI was still around so I could find out the proper torque for this hub bolt.

52 inch should leave a good 1/2 inch clearance to the keel. 54 becomes a whole new ball game.

Jeff, that's a GP Force 1 prop hub. Wish that's what I had. In the picture you posted the aluminum part against the case is actually a crankshaft bearing and extends fairly deep into the case, which needs to be machined to accept it. mine is simply glued and screwed to the case to hold an oil seal. Imagine my disappointment when I pulled this engine apart and realized I didn't quite have what I thought I did. BTW, they don't generally use those until they get into the 2 liter strokers.
 

Doug Riley

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Jan 11, 2004
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Barney: If your engine doesn't have a beefed-up #4 bearing... well, it should. Even the very shortest hubs on unmodified cranks sometimes led to the fracture of the crank at the radius where the fanshaft journal begins, followed by the departure of the prop and the stub of the crank. Scary.

The situation is worse with a cast stroker crank, but even a stock (or other) forged crank is not strong enough to tolerate the cyclic bending loads on this dinky little journal and #4 bearing in their stock config. Especially with a hub that features a bit of cantilever extension, as yours does.

IMHO, simply drilling the original bolt hole deeper, while keeping the tiny #4 bearing, is not a proper fix. It just keeps the parts aboard the aircraft when they break.
 

Barney Bahle

Junior Member
Joined
Jul 25, 2011
Messages
483
Location
Crossville, TN 38571
Aircraft
Rotorway 162F
Thanks for the reply Doug. Fortunately it is a forged crank so less prone to breakage. Other than the Great Plains hub that Jeff posted, are there any other options to beef up #4?

I'm still looking for the hub bolt torque. Anybody?
 
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