VW Engine Mount

philtua

Newbie
Joined
Apr 21, 2011
Messages
20
Location
Orlando, Florida
I am currently re-building a Bensen Gyro that came with a Mac engine and am looking to convert it to a VW engine. Does anybody have the drawings to build the VW engine mount?
Any information I can get will be greatly appreciated.

Contact me at [email protected] hotmail.com

Thanks.
 

Doug Riley

Platinum Member
Joined
Jan 11, 2004
Messages
6,763
There are several types of VW mount for gyros.

Your first choice is which end of the crank to mount the prop on. Bensen and a few others put it on the clutch end, which is the proper place from the crankshaft's perspective. You need to create a prop hub that picks up the four drive pins in the big end of the crank and (if you follow Bensen) also is supported by an extra bearing that fits into the existing recess in the crankcase.

Mounting become awkward in this situation. Bensen opted for a crude bed mount made of aluminum angle and no vibration isolation. He didn't supply plans, but the photos in his manual are clear enough to copy the design. I can scan mine to you if that's your option.

OTOH, many have used the small (fan journal) end as the power takeoff point. This is not a safe option without some modification, as the #4 bearing, and that end of the shaft, were both designed only to support the torque and side loads imposed by the fan belt. This belt merely drives the fan and the alternator/generator -- only a few horsepower. There have been cases of this small crank journal snapping off and departing the aircraft (along with the prop). This obviously is a lethal possibility, what with your rotor just above the prop and the tail tube just below it. The prop really needs to stay on the gyro.

There have been various approaches to beefing up this end of the crankshaft. The most extensive, expensive, and elegant is Revmaster's. Great Plains had a simpler approach IIR.

If you do use the small-end drive, there are firewall-style mounts that attach to the bell-housing portion of the case. I'm not aware of plans for this option.

Be aware that the bare minimum displacement for a VW to work reasonably well on a gyro is 1835 cc (a 92 mm bore). The livelier machines used a stroker crank and a special cam as well as the big-bore kit, totalling 2100 or 2200 cc.

It's quite an involved project and (in my experience from decades ago) not terribly reliable in the end -- even if your prop doesn't fly off.

Loud, too.
 

WaspAir

Supreme Allied Gyro CFI
Joined
Oct 21, 2006
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5,657
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If you dig deep into this:


it describes the mods that Limbach did to make their successful line of VW based aviation engines.
 
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