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Harbor Freight Vacuum Pump Performance

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LAN_403

Arcstarter

Wed Jul 13 2011, 06:45AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

To help speed the process up, you could try to use a backing pump. On this website

it claims that a single air conditioner compressor can get to 1 Torr, and 2 series compressors achieved 10mTorr. I am very skeptical of those numbers, but if it is true, i would be highly impressed. Either way, putting a pump in series with your pump, be it the same pump or something with less of a vacuum, should help somewhat. You may even achieve a better ultimate vacuum, im not sure. I got my A/C compressor on eBay for around 20 dollars plus shipping, and im sure your pump would pump better against ~1 Torr rather than 1atm.

Or, if you are serious about doing the experiments you are talking about, why not get a turbo molecular or diffusion pump? They can be had for fairly cheap used (as compared to brand new ones) on eBay, and they can reach a deep enough vacuum for making assorted vacuum tubes, i am almost sure of that.

Patrick

Wed Jul 13 2011, 07:03AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

I would kill for a turbo molecular pump, there just so cool!!! like a tiny jet engine.

Daedronus

Wed Jul 13 2011, 08:39AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

What if you got one of the cheap turbo pumps on eBay, that have bad bearings, and recondition it?
Would that work?
Sometime in the distant future I would also like a turbo or diffusion pump....

Ash Small

Wed Jul 13 2011, 11:14AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'd also reccomend a turbo or diff pump.

diff pumps are much simpler and don't need the expensive controller and connecting lead, but there are instructions for building both single phase and three phase turbo controllers on the net. I've posted the links before on here, but will post them again later.

There are also instructions for building diff pumps (I'll post a link later) but they are usually available pretty cheap on Ebay, etc. (A two inch diff pump is usually sufficient for most amateur stuff, but 3 or 3 1/2 inch pumps are usually cheaper. (I've a 2 1/5 inch and a 3 inch diff pump)

dude_500

Fri Jul 15 2011, 04:03PM

Registered Member #2288 Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179

jpsmith123 wrote ...

If I never had the Dosivac pump, I probably wouldn't be complaining about the HF pump right now. The Dosivac took all of about 2 minutes to bury my TC gauge. Now that's performance.

Anyway, what I would like to do is to find the ideal vacuum pump for amateur experimenters such as us.

Here are the qualities it should have, IMHO:

(1) The pump should have at least a 3 CFM capacity;
(2) It should be able to do 15u or better ultimate vacuum;
(3) It should have a gas-ballast feature;
(4) The intake port should be a standard pipe thread, e.g., 1/4" NPT;
(5) It should have some open area around the intake port (e.g., don't need a cumbersome handle in the way), so that standard vacuum hardware can be used instead of the AC type inlet fitting; e.g, so that a standard 1/4" NPT to KF-25 adapter can be used if desired.
(6) Spare parts and documentation (manuals, parts diagrams) should be available.
(7) Cost should be reasonable, say less than $300.

In my opinion, the pump should not have:
(1) Any kind of built in valve;
(2) Any kind of built in vacuum gauge;

So far I unfortunately haven't been able to find all of these features anywhere...all in the same pump, that is.

You're describing just about any scientific grade belt drive rotary vane vacuum pump. You won't get one new for $300, but you can certainly get a used one for that price, they come up frequently on ebay. Welch pumps are very good. Also, replacement parts are easily available from many sources for just about every model of Welch pump ever made, especially their belt drive series. I had a Welch 1400 I got off ebay for $70 + $60 shipping that pulled to 50 microns out of the box with an oil change. This could easily be improved to 10 microns or less with a refurbishing kit that would cost $100-200, but since I was backing a diffusion pump I didn't really care since 50 microns was enough. There are actually not many processes where 50-100 microns is not enough, yet you don't need a secondary high vacuum pump such as turbo/diffusion.

jpsmith123

Fri Jul 15 2011, 09:49PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

There *were* some cheapo AC type pumps that met my criteria, but for some reason, it seems you can't get them anymore. There was a place called "fierychill.com" or something like that, that had what I wanted for $150; and then when I went to buy it, they were sold out, never to be seen again.

The Dosivac would've been perfect, if only the mechanical design of the intake port had been reasonably designed. As I recall the larger Dosivac pumps didn't have the problem, but it seems there are no longer any Dosivac distributors in the U.S.

So I may ultimately be forced to buy a used Edwards or Varian or something on ebay.

Arcstarter

Mon Jul 18 2011, 10:44PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, today i was lucky enough to convince my mom to buy me one of these harbor freight pumps. They used to be 70 dollars, but they are 150 now, which is total bullshit. I filled it will oil and tried it out (using a finger over the intake, how else) and it seemed to be worked. I then fixed up a bell jar to be evacuated with a ball valve and some fittings and 2 copper electrodes, and the pump won't run anymore. It pulls no current.

Has anyone had any experience with the similar pumps on eBay? Is the brand Viot any good? I am not fucking with harbor freight anymore, i have already had a drill of theirs explode on me the second time i used it (when people say one time use, they realllly mean it). I never buy tools from their anyway, unless it is a screwdriver i am going to use for drawing arcs or something i know i will be breaking.

I only have about 150 dollars for a vacuum pump, but i don't think it is possible to find one worth a damn for that much, so i guess i will just not get one. I would rather not have one than spend 150 dollars on something that isn't going to work.

jpsmith123

Mon Jul 18 2011, 11:01PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

I'm confused...you bought a used one on ebay, or you bought a new one from HF?

Arcstarter

Mon Jul 18 2011, 11:10PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

jpsmith123 wrote ...

I'm confused...you bought a used one on ebay, or you bought a new one from HF?

It was a new one from harbor freight.

Patrick

Mon Jul 18 2011, 11:34PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Arcstarter wrote ...

It was a new one from harbor freight.

If they dont give you your money back, their cowards.

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