SonexBuilders.net

I would like to hear from those who may have switched to the Great Plains Force One hub crank. Specifically, we you able to use their 8 dowel pin crank with the timing system of the Aerovee flywheel?
Thanks guys

Hey Gary,

You may be able to get some good info from Jay Gibbs on this one. His Sonex started as an AeroVee then was rebuilt using the GP hub. The airplane is now owned by Mark Waldron (vigilant104) and I'm sure Mark could help you as well.

Are you having issues with your engine?

You have a 1 in 4 chance of it working right, The standard VW crankshaft has 4 dowel pins in it. For higher horsepower engines there is a jig that you buy to install on the 4 pins and drill holes for an additional 4 pins. One of the holes in that jig is offset slightly so that you can only re-assemble the flywheel and crank one way with the 8 pins. In order for it to work GP would have to choose the same two pins to locate the offset pin in between as Aeroconversions does. If they choose another set of pins to locate the offset hole your timing is going to be off either 90, 180, or 270 degrees. I'm sure it can be done as others have put a force one crank in an Aerovee. Maybe ask GP if you can specify where the offset pin goes or have them give you a crank that hasn't been drilled for the additional pins and drill them yourself with the jig you buy online.

Keith
#554

Gary,
I'll be of limited help. As Mike mentioned, my plane does have a GP crank and prop hub. It uses the the Aerovee ignition system (primary and secondaries--all four components). So, yes, it is possible.
As Keith suggests, maybe a call to Steve Barrett of Great Plains could clear up any questions you've got.

Mark

Mark,
Did you have to modify the crank or was the dowel offset already in place to match the Aerovee fly?
Thanks

Gary,
Sorry, I don't know what was done regarding the dowel offsets. The plane, and engine, were built by Jay Gibbs and the GP crank and Force One hub were installed several years before I bought the plane. But I can tell you everything works fine.

Mark

Thanks for your reply. When I go back to the machine shop I will ask if they are able to to the Porsche dowel pin placement if not already done by Great Plains. For those interested, I had recently notice my oil pressure declining and just very recently a large amount of oil coming from the prop hub. When I disassembled the engine, I found out that the number four journal was fairly deeply gouged. I do not feel comfortable with machining the marks out as this is already the spot where most of these cranks fail. The machine shop could not readily say what the cause was. They are in the process of cleaning the case and will then mic it to see if anything can be found. So, I am just looking at options.

Sorry to hear it Gary. Please keep us up on what they say and what you decide to do. Good luck!

Gary, did you have the restrictor plug to the #4 bearing removed on your case? If you did and the journal was gouged, that would be of concern to all of us that have removed the restrictor.

Ken W

No my plug is still there. This mod was recommended after I had assembled my engine and I have planned to remove it on next rebuild. I do not know if it would have made a difference. I still have not hear back from the machine shop yet. It's a bummer though, I would much rather be flying than thinking about other options on a rebuild.