Vacuum Pump Control

[Mick Tomlin]

Peter

The small slave pipe is 1.5in waste pipe with stop ends at 8ins long.
For intended purpose this works just fine.
My pump is a Thomas rated to -21inHg.
Maybe for a bigger capacity system it would be worth enlarging to give it more capacity.

Mick

[Peter Balcombe]

Having now found a scrap length of 4” soil pipe, I see that the standard stop ends are £4.50 a throw at the local Master Plastics store! A clubmate has donated an old aluminium gas (may have been CO2) tank which is 110mm diameter & 300mm or so long & another has suggested old (empty) fire extinguisher tanks.

Looking on the web, I see that a 1L capacity dry power extinguisher tank is a similar size & can be bought new for £12 or so. A 0.6L tank is not much bigger than the sub-reservoir.
https://www.firesafety.uk.com/fire-ext ... inguisher/

Thus fire extinguisher type tanks may be a possible alternative to PVC pipe - although converting the outlet size may be more of a challenge!

[Peter Balcombe]

A quick calc shows that a 4” pipe 15” long is approx. 3L capacity.

[Mick Tomlin]

Peter

The total length of the two 4in. pipes on the system I constructed is 24.
2mt. wings have been done without any problems holding vacuum, that is after chasing and curing any leaks.
Personally I would go the pipe reservoir route as the unit will be a lot lighter and more compact for storage and moving about.

Mick

[Peter Balcombe]

Mick, I got hold of an Aluminium cylinder approx. 4” diameter & 300mm or so high at the neck which started me looking at gas cylinders as a possibility.
You’re probably right in that most extinguisher cylinders are steel & heavier. However, I’ve just found a possible source of 110mm x 400mm ish ones, so am hopefully getting a couple to try for <£10.
The PVC end caps alone were going to cost £20!, but I could still go that route.

I will report back in due course - maybe with a bad back
Peter

[Mick Tomlin]

Peter
If you want to go the metal cylinder route how about one of the 7Kg capacity lightweight propane cylinders.
These are being fazed out and no longer eligible for refill.
It may be possible to pick one up for scrap price or free from a local bottled gas supplier.
Ally construction and very light.
Mick

[Philkiteflyer]

Mick, I got hold of an Aluminium cylinder approx. 4” diameter & 300mm or so high at the neck which started me looking at gas cylinders as a possibility.
You’re probably right in that most extinguisher cylinders are steel & heavier. However, I’ve just found a possible source of 110mm x 400mm ish ones, so am hopefully getting a couple to try for <£10.
The PVC end caps alone were going to cost £20!, but I could still go that route.

This option brings to mind 'Failed' Aluminuim skuba tanks. They would be lighter than steel for sure but I know nothing about volume / weight etc.
If you have a dive shop close by, maybe worth a try ? ? A quick google found this add in NZ https://divedoctor.co.nz/product/catali ... ith-valve/ I'm sure they would last longer than plastic.

Cheers from NZ,
Phillip C
Invercargill