I've posted this elsewhere but know that there are some clued up people here, so though I'd throw it out to see if anyone can help.

It's not a "which model" or anything like that, but does anyone know if it's possible to slow the motor down on one using a dimmer type switch?

I have a little Vax Mach8 which is currently being used as part of a dust extraction system in a blast cabinet, though at the moment it's much too powerful and sucking half the media out as well as the dust.

I was thinking of something like a light dimmer switch though, as I know the square root of all about either electricity or motors, thought that someone may be able to point me in the right direction as in what to get to slow it down.

The only condition is that it needs to be variable as it will be a lot of trial and error, plus different air pressure for various things, so adjustment will be necessary. Dave
2010 5.0 Autobiography

Why not put a branch on the pipe with an adjustable opening so that you can leak in fresh air and thus reduce the suction applied to your application?

I think that, having looked at several (all expensive) ways to slow the motor down, this is going to be the logical solution.

Going to have a play with it as soon as I get a bit of time.  Dave
2010 5.0 Autobiography

If you're trying to regulate the speed of a motor then be careful using light dimmers. You need something which can cope with inductive loads, whereas lights are mostly resistive loads.

Would it not be easier to fit a filter which passes dust but traps the media?

It's possible using a triac or thyristor dimming circuit with a suitable optocoupler for isolation. But if all of this is gibberish to you I'd recommend the bypass pipe route that others have suggested.

Most vacuum cleaners have that sort of arrangement as standard now with a bleed-off valve. 2007 Vogue TDV8 with 255/55/20's fitted

Thanks for the responses guys, much appreciated.

A Variac was recommended as a way of controlling the speed but they're quite expensive and also just too complicated for what I need. Unfortunately my old second hand vacuum cleaner doesn't have any form of bleed valve, so I'll just put a variable one in between it and the filter arrangement I'm going to be using.

I was hoping for an easy(ish) way out but not a major problem really, the hardest bit will be hiding all the plumbing out of the way probably.  Dave
2010 5.0 Autobiography

Thinking about it I had a similar situation a few years ago with a high end but under-spaced (!!) fountain installation whereby the pump needed to get the head of water flowed too much water and it splashed everywhere.
Solution was to put a t in the outlet, one side going to the fountain, and the other had a quarter (or half i forget) turn cutoff valve on the end. By progressively testing different valve settings (and getting very very wet) we got the perfect flow through the fountain.
Same principle effectively. 2007 Vogue TDV8 with 255/55/20's fitted

all you need is a hole in the bit of vac pipe going to your cab which you can open or close as needed, a lot of hoovers have this on the handle as standard.

i suggest cutting a hole as close to where you have it connected to the blast cab as possible, start with something about 1/2" x 1/2" and increase until the reduction in suction is needed. at the end of the day if it doesnt work, which it should, then you can always wrap a bit of gaffer round it to seal it back up again...... There is nothing that can't be fixed with a hammer😜😜
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