On Aug 28, 6:44 am, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
James Waldby fired this volley in news:E4-
:

If the push rod and vacuum inlet had their positions swapped,
pulling a vacuum would pull the membrane out against the cylinder,
improving the seal. Conversely, pneumatic operation would tend
to collapse the membrane.

In short, from your earlier description I had envisioned the
membrane being on the other side of the vacuum, ie, with the
vacuum inlet on the left and push rod entering on the right.
So, have I got things backwards, or maybe the direction doesn't
matter?

Y'know, I might have mis-remembered the arrangement -- it was, like,
1978-to-1982 when I built it, and I was copying another device I
couldn't afford to buy.

I think you're right about which end the vacuum goes on. I didn't
catch that when I drew it, but it would make more sense.

LLoyd
(Chet? You listening?)


Looks like it would work fine to pull the actuator bar in to the
device, it just needs an external spring or such to pull it back out.
But, it also looks like the sock would collapse on itself, so pulling
vacuum such that the sock is expanded against the walls (from the
other end) would probably be better for smoothness and longevity.

Dave