Do Vacuum Motors Pull & Push Equal Amounts of Air?

[Dom G]

I was able to get my MSD based bench wired today and test run the motors. They are the GS 16-1234 motors. I have 6 of them installed and have been hoping to be able to measure up to 400 cfm at 28".

With the problem that Mousehouse1 has been having I'm getting a little concerned that perhaps these motors have low output and I may not reach my objective. It may be premature to come to any conclusions because I'm not ready for a real test yet, but may be by next weekend.

When I test ran the motors today I noticed what seems like considerably more air being exhausted through the motors than the depression side of the motor.

So I'm wondering whether that's normal or is it actually an illusion and the amount of air being pulled in the motor is the same as being pushed out.

Thanks.

Dom

[larrycavan]

[Dom G]

Larry,

I hope to do a actual leakage test some time in the next week. All I was able to do today was to wire everything and test run the motors.

I decided to make the lower back panel 2 pieces, one to cover the depression side of the cabinet and one to cover the exhaust side. All I did out of curiosity when I ran the motors for the first time was to put the depression side back on with about 20% of the screws and left the exhaust side panel off entirely which shouldn't matter. Of course I sealed the exhaust valve as well.

Then I put my hand and a small piece of wood over the smallest orifice hole (.750 ") to get a sense for how much vacuum it seemed to have. I wasn't real impressed. But when you felt behind the motors there was a significant amount of air exiting the motors.

That's the reason I'm asking.

Dom

[Thomas Vaught]

Dom, even with all the screws in you would be surprised at the leakage some people have.

Sounds like you need to test with a good weatherstrip gasket and all of the screws.

By the way, rarely do any two vacuum motors pull exactly the same air flow. When say two are running one typically is not working quite as hard as the other one. Multiple motors like 4 or 8 is even worse. One reason why I put the motors in pairs in "motor cabinets" with one inlet per two motors to try and average the flow.

Keep trying you will get it.

Tom V.

[larrycavan]

Dom,

That was a good idea splitting the rear panel into two pieces. I've often wished I did that...one day I'll get around to it.

Duct tape works great as a temporary seal when you'r trying to sort through a leakage problem.

If you felt significant exhaust from the motors and weak suction at the intake, the door was probably leaking like Tom suggested. A candle works good for finding leaks around cabinet seams.

Hang in there....you're nearly home now...

Larry

[bruce]

I use a verticle water manometer connected with tubing to a thin stainless steel wand. U can use it to run around any place you think you may have a leak, the slightest leak will show on the manometer. I also use it to probe my test peice for leaks prior to making a test

[84-1074663779]

Another way is a bucket of soap suds.

A handful of "bubbles" reacts fairly rapidly to even a very small air leak. It is especially good for finding vacuum leaks.

[B. Elliott]

Quick question,

For my vacuum box I have 6 motors sitting face-down. The top of the box is just large enough to house 12 motors side-by-side (3 rows of 4). The box is approx 12" tall.

Something i've noticed is, when i have all of the vacs running, the exhaust side of them seems to pulse. the airflow would look like a wave pattern if you plotted it over time.

would this be a side effect of each motor flowing differently, or would it seem more of a power/voltage issue... considering they're wired up with three computer monitor cables? :laugh:

[larrycavan]

[B. Elliott]

[gofaster]

B.Elliot,

"considering they're wired up with three computer monitor cables? "

STOP!

You need to get the proper sized conductors for your motorsI

I would recommend at least 14 ga. stranded wire to each individual motor. The feed to more than one motor should be heavier.

I'm no electrical whiz, but I know that if your wiring is getting warm to the touch, that you are flirting with disaster. You could start a fire very quickly.

If you go to the building supplies outlet or wiring center, you will see that there is probably a guide for wire sizes and applications printed on boxes of wire. This is a very dangerous area to try to be frugal.

If there is nobody you can ask for direction on this, there are books on basic wiring that should help. Please use the proper connectors, enclosures, and procedures for your electrical components.

[B. Elliott]

Yeah i know. I haven't been running them long enough to get too hot. When i feel warmth in the wire, i shut'em down.

One thing that had me concerned, I did have a 12ft length of welding or phase 3 cable with a black, red, green and white wires running through it. Same diameter as a nickel, maybe a quarter. I had a friend come over and look at it to see if he could wire it up for me (more experienced w/120). He said, "Are you kidding me, thats overkill. You don't need wire that big". He ended up asking me if he could have the wire and i said, sure.

Is that wire really overkill for 6 motors, or did he just shaft me on a 12ft extension for his welder?

[Thomas Vaught]

A SF 600 Bench requires Number 10 gage wires from the wall plug or breaker box. This is for a bench with EIGHT motors that draws 37 amps.

You have 12 motors. Think about it.

A SF 1200 has 16 motors and pulls almost 80 amps. More than most welders. You are probably around 60 amps. A welder needs Number 6 gage wiring.

I would look carefully about your wiring strategy.

Tom V.

ps I think you got shafted.

[B. Elliott]

Gotcha'.

Right now there's only 6 motors wired, there's just room for 12. With that example i do get your saying and i think i'll put it on hold for a while. (I'm getting my cable back!)

So far it's pulled 54"h2o thru a 1.004" hole. No velocity readings yet, since i dont have my pitot tubes. I have noticed i can pick up some pressure difference tapping into the inside and outside wall of the first 90deg bend under my plenum.