Vacuum pump rebuild

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
Tyler Meagher
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Vacuum pump rebuild

Post by Tyler Meagher » Wed Mar 21, 2018 10:17 pm

Hi,

I have started taking apart my vacuum pump. It is a Pfeiffer DUO 1.5 A. I removed the motor from the pump and the motor was complete stuck. I didn’t know it was completely rusted over inside until I started taking it apart. It looks like the shaft seal leaked and water and oil got inside the motor. My dad said the motor can probably be fixed with a little cleaning and some new bearings. We had to make a special tool to remove the motor housing bolts because they didn’t have a standard bolt head. Below are pictures of the pump and the disassembled motor.

Tyler
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Adam Binns
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Re: Vacuum pump rebuild

Post by Adam Binns » Wed Mar 21, 2018 11:49 pm

please keep us up to date on the results as I have always avoided broken parts due to lack of experience with repairing them and would like to see someone repair vacuum parts.
"it's not illegal just don't get caught"

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Rich Feldman
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Re: Vacuum pump rebuild

Post by Rich Feldman » Thu Mar 22, 2018 3:56 pm

Yuck! I'm sure the motor will feel much better after some TLC from you.

Rust-encrusted steel tools clean up amazingly well with an overnight soak in plain vinegar.
I've never tried that with electric motor parts, but imagine it would be no problem on a stator.
For armatures, pay attention to side effects from galvanic current between dissimilar metals in contact.

To get residual vinegar out of nooks and crannies, and maybe porous insulators, plain water ought to do the job. It's safe, cheap, and available under pressure from garden hoses.
Richard Feldman

Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher » Sat Mar 24, 2018 9:12 pm

Adam, the pump I’m rebuilding is the same pump Andrew Seltzman rebuilt: viewtopic.php?f=10&t=9214&p=62499&hilit ... duo#p62499. He provided tons of photos and the service manual so I have a good guide to follow.

Rich, thanks for the advice. This morning I cleaned the parts with simple green and scotch bright pads. I then put the stator in a bucket of vinegar. Tomorrow I’ll see how it turns out. I also ordered two new bearings. Next weekend I will reassemble the motor.

Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher » Sun Apr 01, 2018 3:41 pm

I finished rebuilding the motor. There were 5 hard parts.

1) We didn’t have the correct punch to remove the roll pin holding the fan on the shaft. We used a small nail instead.
2) The bolts holding motor together had a special top and my dad had to make a custom tool for me to remove the bolts.
3) There was a snap ring holding the front housing. It was hard to get off.
4) The pump coupler needed a special tool to remove, and we broke the plastic and magnetic ring when removing it. I’ll post more about that later.
5) Removing the bearings was tough for me and needed my dad’s help.

The first picture is the motor completely disassemble and cleaned. I used simple green and scotch brite pads to clean everything. I tried Rich’s suggestion soaking the stator in vinegar overnight. It removed some of the rust but I used 400 grit sandpaper on the metal inside to remove the rest. I put the rotor in a drill and used sandpaper to clean it up more. I also used the sandblaster on a few parts for fun.

The second picture is cooling the rotor shaft with dry ice. I heated the bearings with the heat gun and cooled the shaft with dry ice to make them go on easier.

The last picture is the fully assembled motor.
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Rich Feldman
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Re: Vacuum pump rebuild

Post by Rich Feldman » Mon Apr 02, 2018 4:54 pm

Looks very nice, Tyler. Does it run when you plug it in? :-)

I just did a vinegar soak on some motor parts myself, for the first time, and on a big old screw extractor.
DSCN0217.JPG
The rotor sections are from my friend Tom. They appear to be of identical design, except for a mysterious difference in the twist direction.
Richard Feldman

Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher » Tue Apr 03, 2018 2:57 am

Thank you. Yes, it runs when I plug it in. My dad wants me to run some more tests before I connect the motor to the pump. I will post about the those tests soon. In your picture I’m not sure why the twists would go in opposite directions.

Jerry Biehler
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Re: Vacuum pump rebuild

Post by Jerry Biehler » Tue Apr 03, 2018 4:26 am

It's usually a good idea to put a megger on the windings to check for leakage after a motor has been in that state.

This is also a good use for electrolytic rust removal. I dont like using acids no matter how benign around stuff like this.

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Rich Feldman
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Re: Vacuum pump rebuild

Post by Rich Feldman » Tue Apr 10, 2018 8:35 pm

Don't want to hijack Tyler's thread, but my own motor-part-cleanup experiment needs an "after" picture.
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The red object, included for scale, is a deformed M&M.
The metal parts got a vinegar soak and, I admit, some wire brushing. Armature bearing on the left was protected with petroleum jelly. Commutator was only half submerged. High water level was visible before polishing, where the brass surface had been de-zincified.

I haven't yet meggered the armature winding, but want to. That part was fished out of an e-waste bin, and isn't expected ever to run again. Unless it's re-animated by un-natural methods, for a "ball bearing motor" demonstration. :-)
Richard Feldman

Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher » Wed Apr 11, 2018 4:01 am

I got my first piece of test equipment. It’s a Fluke Digital Multimeter. This is the first time I’ve ever measured anything with electricity. I'm just learning about some of the test we ran, and I don’t have a good understanding of the meaning of each test yet.

I performed 6 test:

1) The resistance through the coil windings was 4.9 ohms. This measured the same before and after cleaning.
2) The resistance from the coil leads to chassis was open. OL displayed on the DMM.
3) The voltage was 121.4 volts AC when I plugged it in.
4) The current was 2.25 amps running the motor with no load.
5) The motor ran at 3568 RPM (revolutions per minute) with no load.
6) I didn’t have access to a megger meter to measure the insulation leakage, but we used a high voltage power supply to generate 500 volts DC across the coils and ground. I then measured if there was any leakage current with another meter. See picture below.

I'm currently measuring the mechanical horse power of the motor and computing the motor efficiency. I will have another update soon.
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