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Re: El Cheapo Vacuum Pumps

Original poster: "Mike" <mike.marcum@xxxxxxxxxxxx>

I got a 20 micron Robinaire that goes down to 25 micron measured (not sure of the meter accuracy, it came with it as a package deal new from ebay). The hard part is finding petcock valves designed for vacuum that won't leak over time when closed (not much of a glassworker to make more permanent seals, guess I should learn).

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, August 05, 2006 12:24 AM
Subject: RE: El Cheapo Vacuum Pumps

Original poster: "Dave Halliday" <dh@xxxxxxxxxxxxxx>

Quick heads up -- this is a __venturi__ unit and needs a separate air
compressor to run.

If you download their service manual, you will see that it requires 4.2 CFM
at 90 PSI.

If you look at their air compressors, you will see that their item #47065
with a 3Hp motor and a 152 pound shipping weight is only rated at 3.5CFM at

The vacuum pump is perfect for a large auto shop that already has a
high-capacity air system and wants to work on air conditioning systems but
for anything else, there are better alternatives.

Your best bet for small vacuum pumps is to salvage the compressor from a
busted refrigerator. Many times, these are tossed because the thermostat
breaks.  Some of them will have bad compressors but not all.

> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Friday, August 04, 2006 11:27 AM
> To: tesla@xxxxxxxxxx
> Subject: El Cheapo Vacuum Pumps
> Original poster: Mddeming@xxxxxxx
> Hi All,
> Anyone wanting an inexpensive first stage vacuum pump that can get
> down to 30-40 mmHg might want to consider this item from
> Harbor Freight Tools:
> Item No. 92475
> Central Pneumatic
> Air Vacuum Pump with R134A Connector
> Regular Price $16.99
> Sale Price $11.99
> Their on-line catalogue is at:
> <http://www.harborfreightusa.com/usa/common/start.do>http://ww
> Since Tesla described a number of his experiments with partial vacuum
> as being in the 50-150 mmHg range, this should put most experimenters
> in the ballpark.
> Peace,
> Matt D.
> Disclaimer:
> I have no financial or personal interest in Harbor Freight Tools, Its
> suppliers or any associated companies, and this is not a compensated
> endorsement.