----- Original Message -----
From: "Marvin Kaye" <marv@lancaironline.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, June 03, 2003 8:54 AM
Subject: [FlyRotary] Re: electric vacuum pump - a way unscientific science
experiment


> Posted for "Ian Beadle" <ianb@ozzienet.net>:
>
> > Rats, I'm thinking electric gyros now.
>
>   Marko,
> Electric instuments are noisy, unreliable and expensive.
> An ordinary aircraft vac. pump can be modified to be driven by a 10mm
> internal toothed timing belt by removing the shear coupling and adding two
> push fit ball bearing races. The pump can be driven at a lower speed than
in
> the Lycoming by selecting the appropriate cogs and driving from the water
> pump pulley. For aircraft use smaller a smaller crank pulley than
standard.
> Ian Beadle
> RV6A Rotary.
>
>

Ian, do you have a photo or sketch of your aircraft vac pump set up?  I
tried that myself, although I drove it from the main pulley (might have been
a mistake) and found that if the pulley on the pump was smaller enough to
produce vacuum at lower rpms (3000) that the pump soon dissintergrated at
high engine rpms (6000)  If I made be pulley diameter larger, it lived at
high rpm but did not produce adequate vacuum at lower rpm.  The water pump
pulley driving it did not occur to me.

Ed Anderson