Dust Collection Vacuum Source

[nvecta]

Board,
Forgive my newbie questions. Terribly new here and researching on building my own bench. I have a question on a vacuum source that I have laying around that I can use. I have a central dust collection setup for woodworking. The unit is rated at 500CFM at 2.76" of pressure through a 4" diameter inlet. Is this enough to start with? I would be primarily working with small 4cyl heads that flow max 225CFM.

[86rocco]

Most likely, that will not be adequate. The types of blowers most commonly used in dust collection system usually aren't capable of generate a large enough pressure difference, typical test pressures are 10", 25", 28" and sometimes higher with 28" being the most common.

You can test your blower by making a crude test rig sort of like the picture below but without the head and see how much pressure you're able to generate if you restrict the out flow.

[Tony]

No, the developed pressure is really far too low to be useful. Speeding up the blower to increase the pressure is not really practical either.

I suspect that might be around a 1 horsepower unit.

For instance doubling the blower Rpm would give you eleven inches, and 1,000 CFM, but drive horsepower would increase roughly eight times.

Something with less flow capacity and more pressure is needed.

[nvecta]

Thanks for the advice.
I had this unit as a portable for sanding-routing. I should just break down and buy some motors since I don't want to re-route the big unit - It can pull 3560 cfm at 17 inches on a 9" inlet.

[Thomas Vaught]

If you just buy the motors from the Surplus Center web site the motors are perfect for your needs and are CHEAP.

JMO

Tom V.

[nvecta]

Thanks - I will search for the link.

[nvecta]

Well for giggles while waiting for motors I hooked up the vac to some PVC to the head on a simple bench with a hole the size of my cylinder. I connected everything without gluing up - just taped the joints for temporary and very poor sealing. Pulled 7" with the vac - Put a wye in and connected up the shop vac - Got 10" on the nose. Quite surprised.

Joel

[Tony]

A cluster of vacuum cleaner motors will certainly do the job, that is what most people use, it is the easy and low cost way to do it.

The only problem is that the required mains power can rise to pretty scary levels fairly quickly, and the available electrical power is probably what restricts most of us from just adding more and more motors !!!

[nvecta]

Power is not a problem - When we built the house I had the electrician drop in 2 -110 circuits -1 -220 circuit - Then I added another 220. This was for my woodworking days.

[nvecta]

Well, I glued up some of the pipe - Made an averaging pitot tube from some brass tubing laying around. Hooked up some flex tubing leftover from my moms oxygen tank when she was here last. Ran the tubing up on the wall against a yardstick. Put the head on the bench and turned everything on. Ran everything at 10" -Measured 3 or 4 times to make sure it all matched up - converted to 28" - Plugged it all into some spreadsheets I located in the forum. SURPRISE SURPRISE SURPRISE - I measured a flow within 9 CFM (5%) of what the head flowed last week on a superflow bench. I need to glue up some straws to clean up the flow and see if it comes closer.

Joel