I think there was something else going on in the failure of your aircraft

vacuum pump

set up. I am just trying to understand what it was. Perhaps a vibration of
some sort. Do you have a drawing of the bearing housing?

This is not to say I am against smog pumps used as vacuum pumps. I love

low

cost solutions like that.

Ed Anderson wrote:

No, Paul, you are correct.  I never let my engine rpm below aprox 1500 rpm

due to
the clanking of the gear box.  Actually, in flight, I seldom let the rpm get
below 3000 (except last stages of final approach) which give a prop rpm of
around 1400 rpm.  A lycoming at an engine/prop speed of 1400 rpm would spin
the vac pump at 1400x1.3 = 1820 rpm and would certainly produce sufficient
vacuum, so you are probably correct about something other than rpm range.

  However, after two vacuum pump in a years time (I rebuilt the first one
with a kit) and insufficient vacuum at low rpm, I elected to go with the
smog pump. I tried pulley sizes from 5" to 7.5" dia for the vac drive.  I
forget what my eccentric shaft pulley dia is, but it is the two sheeve
reduced diameter one from Mazdatrix. I think its around 4" in dia.

I have attached several DXF files of my fitting in case they are of any use.
I am not a mechancial engineer so there well could be some design flaw in
the one I came up with.

Ed Anderson

I'll load these DXF's later and see if I can convert them to gifs.

Paul Lamar

 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org