vacuum pump for experiments

All the broken pumps I've seen were neglected and ruined on the pump side, not the motor. Not using a pump (letting it sit with old oil) seems to be the worst thing you can do to it.

Reply to
Cydrome Leader
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What are the important clues to look for when buying a used pump?

Reply to
Chuck Sherwood

the motor. Not using a pump (letting it sit with old oil) seems to be the worst thing you can do to it.

Interesting. I got a two stage pump with a burnt out motor free from the Cavendish Laboratory. Probably the motor had burnt out because of a faulty oil distributor valve in the pump, which allowed the pump chambers to fill with oil and stalled the motor. I got the motor rewound and replaced the pump seals and it's a good pump. I've been lead to believe that this isn't uncommon on pumps which don't have a thermal cut-out fitted to the motor. Badly damaged pumps are most likely the result of water being drawn into the pump (and being allowed to sit, causing corrosion), or abrasive dirt causing wear.

Chris

Reply to
Christopher Tidy

I have two 1/3 HP direct drive vacuum pumps that I am about to throw away. Chicagoland.

Both pumps do NOT work well. They both spin, but do not suck.

I know exactly why. They rusted solid and could not spin, when Ibought them. I took them apart, cleaned etc. Now they spin but produce almost no vacuum.

If anyone needs them, for the motors or whatever, let me know. I can post more details if anyone is interested.

i
Reply to
Ignoramus633

FWIW, I bought a vacuum pump from William Noble who posts on this BB occasionally. I use it for a vacuum chuck I built. I don't know if one of the pumps he has will meet your needs, but I found William to be a help. The pump I bought pulls about 25 in and works well. Quiet little thing too.

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Peter

Reply to
Peter Grey

Take a look at the gast pumps, they seem to be much lighter, especially the oiless rotary vane ones. Shipping seems to be around

25-40. What you need sort of depends on what you want to do with it too. You can get all of the max vac and flow rate information for the gasts out of their on line info (some times you have to dig a little and figure out their catalog # systems) jk
Reply to
jk

THe only time I tried vacuum with urethane, it started foaming with no end in sight. How do you do it?

jk

Reply to
jk

Chrisopher Tidy posted: " I think neon signs do require a pretty high vacuum if they are to work well and stand the test of time, but I'm not certain of this. Perhaps someone here can confirm? There's also a short article about vacuum pumps for neon signs here, which suggests that the ultimate vacuum required is pretty high:

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" Chris, just for the record neon signs do not require a particularly high vacuum level, and usually just mechanical pumps are required for their production. Their lifetime is limited by only the outgassing of their electrodes.

The link that you posted largely addressed secondary oil diffusion pumps and their ilk, which produce vacuums order beyond anything required for lighting technology and at a cost orders of magnitude beyone anything required for this application (as in 10^-6 MM Hg.). In fact, this is the quality of vacuum required to produce cathod ray tubes and transmitting tubes, with a little help from something called a 'getter'.

For the purposed of the original poster, he would be well advised to salvage a sealed compressor from an old air conditioner or refrigerator, then convert it to a vacuum source per article that both appeared in Scientific American and the Amateur Scientist's Handbook.

Harry C.

Reply to
hhc314

Weight and shipping cost.

Harry C.

Reply to
hhc314

I think its much easier to buy a pump vs make a pump. There are plenty available. I think the conversions centered around belt drive AC compressors, which I think are a thing of the past??

Reply to
Chuck Sherwood

A Refrigerator Compressor Vacuum Pump

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Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

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Reply to
Boris Mohar

Yes, yes. Another case of hands working faster than brain.

Reply to
TheAndroid

Here are a few things to look for. Some of these you can only check if you can see the pump in person, but that's always a good idea if it's nearby.

  • Check out the general physical condition: does the pump appear to have been looked after well or is it knocked around and covered with grime and rust?
  • Ask the seller what is has been used for. If it has been used in industry for neon sign manufacture or air conditioning servicing it will probably have seen much heavier use that if it was used in a school science laboratory.
  • If the seller has a vacuum gauge available, ask them to measure the pump's ultimate vacuum.
  • Inspect the oil. Is it dirty? Metallic particles in the oil may indicate heavy pump wear. Vacuum pump oil is usually colourless and doesn't smell. If it smells it's the wrong kind of oil.
  • Unscrew the oil drain and let a few drops run out. Is the oil contaminated with water?
  • Listen to the pump running. These pumps are usually pretty quiet. Clacking noises may indicate sticking vanes.

It seems from what Harry says that you should be fine with a mechanical pump for making neon signs, although you will need to be able to manufacture and seal the glassware. Perhaps Harry could confirm if a single stage pump is adequate or if a two stage pump is required?

Hope this helps

Chris

Reply to
Christopher Tidy

The urethane mixes I work with contain around 80% solids, so foaming isnt usuallly a problem. It will be if humidity is high or any of the ingredients arent nice and dry, though.

Reply to
Greg Deputy

Is it possible to use a regular compressor as a vacuum pump? After all, both do the same, pump air out of some place and into another place.

i
Reply to
Ignoramus633

On 13 May 2005 19:58:34 GMT, the inscrutable snipped-for-privacy@w-sherwood.ih.lucent.com (Chuck Sherwood) spake:

Old refrigerator pumps work well for many things and can be had free around most parts of the country. I see a couple free every week in the local paper, and the town has just 23k people. One of these days I'll go get one, pull the pump, and salvage whatever else I can, like the sheetmetal.

Here are two decent home-made solutions:

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------ We're born hungry, wet, 'n naked, and it gets worse from there. -

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Website Application Programming -

Reply to
Larry Jaques

Or an old refridgerator. I have one that I use for vacuum bleeding brakes. Pulls a very good suction. Lane

Reply to
Lane

Yes but the dead space above the piston (ie, the part of the cylinder which isn't swept) limits the ultimate vacuum quite badly. Oil-sealed rotary vane pumps don't suffer from this limitation; their ultimate vacuum is usually limited by the vapour pressure of the oil.

Chris

Reply to
Christopher Tidy

Related question: what does "gas ballast" mean in the context of vacuum pumps, and what is it for?

Reply to
Don Foreman

I guess it ought to be asked if you have an idea of what kind of volume, flow, and vacuum level you intend to work with? Light vacuum, up to about

29 inches of water or more and great volume and flow is available from your household vacuum cleaner. Find surplus vacuum blowers and you can get to 90 inches of water. With a large volume system you first empty it with a high volume pulp like the mentioned blowers then you close that system, switching to a slower pump. HF sells one or two, one being an air operated one that is for A/C systems. No vacuum draw is given, but I assume the A/C guys know what it should be. Above that, then you start looking at lab pumps. Available in all sizes, flows, and costs, so you need to quantify what your needs/desires are first.
Reply to
carl mciver

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