snips...

Easier still is to use an aircraft vac. pump and small toothed belt.
Ian.

Not really Ian. Aircraft vacuum pumps have no provision for bearings
of any kind. A toothed belt chain or any other kind of belt drive
will produce a side load on the vacuum pump shaft. They normally drive off

the

accessory gear case on the back of an aircraft engine. That means you
must machine a mounting block and a properly supported auxiliary shaft
to mount the aircraft vacuum pump. Its been done. Back in 1991
Tim England had a Velocity with a GM 4.3L V6 at OSH with a Singer
sewing machine flat belt drive aircraft vacuum pump. I got a picture
of this around here someplace but cannot find it right at the moment.

In the mean time here is the bearing requirements for a belt drive.

Paul Lamar

Thats what I did. It was quite easy, because the vac. pump has a cast metal
housing around the dog coupling. I fitted two bearings (press fit) and a
steel shaft with a 10mm toothed cog. The other cog fits onto the water pump
pulley utilising the existing 4 bolt holes with longer bolts.I'll take some
pictures. There is a bit of maths involved for cog sizes. The pump runs at
1.3 times engine speed on the Lyc.
Ian RV6A.

 
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