Vacuum Potting in the "At Home" Shop

[kayakerca]

Thought I'd post a little video so anyone interested could see just how fast and furious the air is extracted from pickup with a single stage vacuum pump. I wish the video had been a little better, but you'll get the idea!

Vacuum Potting - YouTube

Last set I did for nearly 2 minutes. This set. . . ~ 30 seconds before I pulled the plug.

[big_teee]

Great Video!
You make me feel obsolete, and old fashioned with my non Vacuum mode!
T

[kayakerca]

Great Video!
You make me feel obsolete, and old fashioned with my non Vacuum mode!
T

You have skills Terry, I just have curiosity.

But does that look like it's is sucking the air out or what!

[David King]

Jim. . .

Who makes that vacuum pump? Is it a Gast? Was it for automotive refrigerant recovery?

[kayakerca]

Jim. . .

Who makes that vacuum pump? Is it a Gast? Was it for automotive refrigerant recovery?

It's just a cheap little no name "Made in China" single stage vacuum pump identical to the one sold by Harbor Freight for ~ $90. It pulls 30 inches of vacuum based on two different sets on gauges I have (one of which I used to use when I did air conditioner repair work back in the day).

[RedHouse]

... identical to the one sold by Harbor Freight for ~ $90...

This one?

http://www.harborfreight.com/25-cfm-...ump-98076.html

[kayakerca]

This one?

http://www.harborfreight.com/25-cfm-...ump-98076.html

Wow, it's gone up $10 since I started the this thread. That is basically it other than only one size fitting to the gauges and 2.5 cfm vs. 3 cfm.

Here is the exact one I bought off ebay.

http://www.ebay.com/itm/R410a-1-Stag...item4606d79350

[David King]

The ebay one goes down to 5Pa whereas the HF one is rated to 10 pascals. Somewhere there's a table that will convert Pa or pascals to inches of mercury. It's right around 29"/Hg but the Ebay one looks like a better deal all around.
I didn't think a single stage rotary vane could pull that kind of vacuum.

[kayakerca]

The ebay one goes down to 5Pa whereas the HF one is rated to 10 pascals. Somewhere there's a table that will convert Pa or pascals to inches of mercury. It's right around 29"/Hg but the Ebay one looks like a better deal all around.
I didn't think a single stage rotary vane could pull that kind of vacuum.

Definitely not the quality of pump I used when I did component work on window air conditioners, but it puts 30 inches on the same set of gauges (over a much smaller volume of my mini crockpot). If you have a look at the little video I did, you have to ask yourself if you have ever seen so much air removed from a set of pickups being potted. :-)

[RedHouse]

Definitely not the quality of pump I used when I did component work on window air conditioners, but it puts 30 inches on the same set of gauges (over a much smaller volume of my mini crockpot). If you have a look at the little video I did, you have to ask yourself if you have ever seen so much air removed from a set of pickups being potted. :-)

I was wondering if some of that was from the wax, maybe not all of it was air in the coil?.

[kayakerca]

I was wondering if some of that was from the wax, maybe not all of it was air in the coil?.

Interesting question. Any chemists in the crowd?

I'll be potting some this week. I run the pump against the liquid wax and see what happens. I'll be surprised if much air is saturated into the liquid wax, especially after it has been evacuated a bunch of times potting pickups. I would suspect that the same principle would apply to non vacuum potting as well. If the air is removed easier in non vacuum potting, the same would apply in vacuum potting, and at some point, all the air that could be removed from the wax at the level of vacuum used would be liberated and all subsequent potting would extract only air from the pickups. Anyway, I'll test it and see.

[David King]

It would be easy to check the intake filter for signs of wax building up if it is boiling off at low pressure.

[kayakerca]

It would be easy to check the intake filter for signs of wax building up if it is boiling off at low pressure.

If wax were being extracted from the potting process, the gauges gumming up and not operating would probably be the first sign. I don't know if there are any filters on evacuation pumps of this style and there do not appear to be any that are intended to be accessed and maintained.

[RedHouse]

It would be easy to check the intake filter for signs of wax building up if it is boiling off at low pressure.

No I didn't mean "wax" I meant other things in the parrafin/bee's wax, assuming of course, that's what he was using.

I don't know, like oils which might have some compounds that gass-off under heat and extreme vaccume.

[kayakerca]

I don't know, like oils which might have some compounds that gass-off under heat and extreme vaccume.

The oil in the vacuum pump is intended to a medium for trapping gas molecules being extracted. Not sure how you would determine what exactly was being drawn off during the process.