Vacuum pumps?

[Zach]

Hi guys,

Wondering what sort of vacuum pumps you guys have used/recommend for doing fiberglass layups? Brands, sizes... etc.

Had a curiosity about them for a while and never have got around to asking!

Thanks,

Zach

[Quetzalsailor]

I now own two: One is an old milking pump, bought in an Amish farmer/mechanic shop not far from Intercourse, PA (no, really; also just a little further from Ephrata). It is a vane type and was abused after rebuild by friends of mine who were laying up something or other. It now is so noisy that you would not wish to be in the same space with it. Still works, though. Unfortunately, the farmer has closed his shop and no amount of Googling has revealed a source of parts or service for that brand. I recently bought a Welch laboratory pump on Craigs List for $150; they've been made since the '50s and are still available new for $3k. I expect that the milking pump is the more useful for bagging: lots of volume and good degree of vacuum. The Welch is much lower volume but will generate vacuum suitable for neon tube, electronic tube, and similar serious percentages of vacuum work. Both of these are massive lumps of cast iron with belt drives to 1/2 horse motors, and with serious lubricating oil provisions. The Welch actually uses an oil bath for its seals; special Welch oil which I have not bought.

Some folks think they can use a vacuum cleaner: cheap, lots of volume, some with reasonable vacuum. The problem is the load and heat on the motor. Home types cool the motor with the exhaust air and the whole idea of the bagged part is little or no leakage. The pump has to run for several hours, well beyond having reached terminal heating levels. There's a remarkable amount of heat involved; the milking pump exhaust is over the melting-to-droop point of my PVC exhaust muffler.

[Bill Reichert]

You CAN use a vacuum motor with a simple bleed. Grainger has several models to choose from. The bleed would just be a wood box with in/out holes for the hose and a third hole for the bleed. The bleed is a box with a round hole. On the inside of the bleed is a disk with a piece of leather and an eyelet. A spring is attached to the eyelet. The spring goes through the hole and has a nail in the coils. The vacuum at which the bleed opens is determined by which coil the nail is in. More vac means the nail is closer to the eyelet.
The trick is providing enough cooling air for the vac motor. A motor speed controller will also help cool the motor since the larger motors will provide the required vac will be produced at a lower speed.
This setup has been in use on some cheap player pianos for close to 40 years with few problems other than replacing the brushes.

In the player unit, the in hole (vac side) is attached to the player hose. The motor is mounted in the box over this hole with a foam spacer between the motor and hole for an airtight seal . The bleed box is attached on one side. The boxes are made of particle board to lessen noise. They have fiber packing material inside the box to help dampen sound.

You can also use the box with adaption for an HVLP compressor!

[David]

How about an air conditioning evacuation pump, like one of these:

http://www.ctd4ac.com/vacpumps.html

[jollyboat]

You guys are hard core!
<grins>

[Quetzalsailor]

You're right about the cheap player piano vacuum motors; however, the air that passes through the action as the bellows collapse, etc., is plenty to cool a vacuum cleaner. (It's another hobby of mine.)

The Welch laboratory pump I bought is larger than a normal refrigeration evacuation pump. The issue is, I think, that you'd want lots of capacity to overcome leakage in your vacuum bag and you really don't need the high degree of vacuum you need for refrigeration or laboratory work.

Another cheap way to get vacuum is using the venturi-air compressor deal that Gugeon writes about for small bags.