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.
Jerry Biehler
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Re: Vacuum pump rebuild

Post by Jerry Biehler »

Other than megging it and current the rest of the tests are not important. Put it together and get it working.
Bruce Meagher
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Re: Vacuum pump rebuild

Post by Bruce Meagher »

Patience you must have, my old Padawan.

The motor is complete. In fact, Tyler just finished making some measurements with the Prony brake we assembled. Next, he has to cracked open the pump side and try to get it back into a usable state. Given the current pace he's still a few weeks/months away from his first vacuum test.

BTW, I respectfully disagree that the other tests are not important. For the young folks (and old folks too) I think the fusor journey is about getting some practical hands on experience in a number of diverse areas. Tests and measurements are key elements of that experience. I have a half dozen working pumps, but why pass up an opportunity to look under the hood to gain a little better understanding of how they work.

Bruce
Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher »

My dad and I built a Prony brake to measure the horsepower of the motor. We used this article:

http://chestofbooks.com/crafts/popular- ... otors.html

The first picture is the Prony brake setup. The second picture is measuring the input power and the mechanical horsepower. The third picture is a graph of motor efficiency vs measured horsepower. The forth picture is the first look inside of the pump. It looks much worse than the motor.
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IMG_8.JPG
IMG_9.JPG
Motor efficiency.jpg
IMG_10.JPG
John Futter
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Re: Vacuum pump rebuild

Post by John Futter »

I was surprised at how bad the motor efficiency was, but then I realised you are not measuring the phase agle of the current vs voltage.
So the actual power will be alot less due to current and voltage not being in phase.
analog devices make some brilliant metering chips ADE7751 that are simple to setup and although designed for kW/Hr meters some have an analog output (CF) of instantaneous power as well as the watthour pulse output
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Rich Feldman
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Re: Vacuum pump rebuild

Post by Rich Feldman »

Good catch, John. The exercise is simpler with DC motors.

Compliments to the Meaghers on the Prony brake. Never seen one like that for real. Once I ad-libbed a motor efficiency demo, using an analog "true wattmeter" and a brake made of wood, shaped like:
brake2.JPG
The brake collar tightness on motor shaft was adjusted with a screw and wingnut. Soon the shaft got hot, the wood began to smoke, and I bet the friction changed. I guess we could figure the mechanical power from torque x rotation rate, or from matching the amount of smoke when the brake is clamped onto a soldering iron. :-)

It being break time, I whipped up an AC phase angle demo in Excel instead of finding one on the Internet. Simple arithmetic instead of trigonometry and calculus, for Tyler's benefit.

It shows instantaneous voltage, current, and power every 10 degrees for 2 whole cycles. Voltage and current are signed values, but when they are both negative their product P = V * I is still positive. It peaks at 240 watts in each half cycle, and averages out to 120 watts.
pf0.JPG

In this demo the sinusoid data points are computed from the control knob values entered in blue cells.
The values in Average and RMS boxes to the left are computed from the same numbers that are charted.

When current has same intensity, but lags voltage by 40 degrees, the average power is down to 92 watts. At some instants the power is negative.
pf40.JPG
Ooh, the forum let me post an Excel file. See what happens when the lagging current phase is set to 80 degrees (unloaded motor, perhaps), or negative angles (a capacitive load), or near 180 degrees (an alternator with resistive load, or a wattmeter with I or V connection made backwards).
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rms_demo.xlsx
(23.4 KiB) Downloaded 384 times
All models are wrong; some models are useful. -- George Box
Bruce Meagher
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Re: Vacuum pump rebuild

Post by Bruce Meagher »

Oops, my mistake! John, thanks for pointing out the error. I was trying to keep the exercise really simple, but that doesn’t work when you're doing it wrong! Rich, thanks for the spreadsheet and explanation. We'll spend some time talking about it, and re-run the experiment correctly when we have the proper measurement setup. In hindsight this is probably a little advance for a first look at electricity, but is a great example of why it's important to have other people review what you're doing.

Bruce
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Re: Vacuum pump rebuild

Post by John Futter »

Bruce, Rich, & Tyler

Sorry to rain on the parade, but Tyler now has to learn something that most EE's only get very late in the course.
It reminds me of my youth when with little or should I say no knowledge I thought I could light a flouro tube using a magneto a battey for the tube filaments and direct connect to the 230 volt mains.
Never the less the resulting explosion and glass going everywhere except on me (read very lucky) put me off playing with mains until I learnt how they use inductive ballasts to limit tube current--- much later in life.

So now we have introduced power factor. Tyler I hope your maths is strong.

But first make the vac pump look as good as the motor!!
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Richard Hull
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Re: Vacuum pump rebuild

Post by Richard Hull »

Ugh.....That photo of the guts of the pump is typical of a pump that pumped a lot of moist air for a long time (months/years) with no oil change and then stored for years. It represents what is usually a pump's death and an indication that a new pump is a good idea.

Fighting back from situations like this can be fun, instructive, expensive and often not worth the effort. All the very best in this resurrection effort.
Sometimes it looks far worse than it is....Other times, it is far worse than it looks.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Jerry Biehler
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Re: Vacuum pump rebuild

Post by Jerry Biehler »

Yep, unbolt the pump and check the rotor and stator. If there is ANY pitting the pump is scrap. That probably should have been the first thing that was done.
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Richard Hull
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Re: Vacuum pump rebuild

Post by Richard Hull »

I didn't want to say it, but Jerry is right on. #1 check out what really makes the vacuum. A nice, pretty, clean, smooth running motor married to it's special pump shell never makes a vacuum.

This is why I love belt drive pumps. Quiet running and separate unit pump and motor. The pump system doesn't have to have its special motor working at the same time as its pump. Any motor will work a belt drive pump..........and the motor will power any pump housing.

Any pump housing containing a pitted rotor, damaged blades or especially a pitted internal round housing is typically junk yard bound. How do you know this without opening the case?? If it is direct drive and the motor won't run, you will never know until you inspect it.

With a belt drive, if the motor runs and the pump turns you can vacuum test the system.

I would not hold out much hope for that rusty mass in your image.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
richnormand
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Re: Vacuum pump rebuild

Post by richnormand »

I do agree with Richard's and Jerry's views here. But, if you are in for a hero experiment, in particular after rebuilding the motor, here is what I ended up doing to mine.

When I got my Trivac D16AC pump it was jammed. Not quite as bad as yours in appearance inside but it had been used to pump silicone for molds...
The roll-pin on the center shaft driving the vanes holder had broken and the pin remnants had scored the inside walls and also chipped the vanes. I was able to restore the outer surface for the vanes using a flex car cylinder hone (smallest size I found). Started with a coarse one and went directly to the finish grade. That left a nice crosshatch finish that would bed in the new vanes.

While in there, I used a Duniway major rebuild kit. Fill with oil, dump, second fill and 5 x 10^-3 t and steady for the past 10 years or so.
Its lots of work but doable depending on how stubborn you are.

Worth it for kicks on your own time but not otherwise. I can post photos of the rebuild should you like.
Good luck with it.
PC272478 (Medium).JPG

=^,^=
Bruce Meagher
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Re: Vacuum pump rebuild

Post by Bruce Meagher »

I agree that normally you wouldn’t give this pump a second look. There are tons of vacuum pumps available on the second hand market in great shape that require little to no work. Add oil and go. Is this pump destined for the scrap yard? Potentially, but honestly it does not matter.

I fully expect a pitted mess when we crack the pump apart (hopefully soon)!

What level of vacuum could one achieve with “ANY” pitting? What about a lot of pitting? I don’t know the answers but this sounds like an interesting experiment. The vanes have significant travel. Can one remove 0.030” by boring and/or honing the cylinder to revive this sucker with little performance losses? The sides walls will probably have issues as well. What are the options to fix this… Boring, honing, facing, surface grinding, lapping, and the measurements of these processes are whole new areas to potentially explore. My hope is we gain a little practical knowledge about how two stage mechanical pumps work and maybe a few other things while we’re at it.

Rich, I’d love to see the pictures from your rebuild.

Bruce
Rex Allers
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Re: Vacuum pump rebuild

Post by Rex Allers »

Quick short test after three long reply attempts failed.

Please ignore.
Rex Allers
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Re: Vacuum pump rebuild

Post by Rex Allers »

Fifth try failed.

7 pictures ~100K each uploaded and inserted into fairly long post. Previewed the post and all looked ok. Click the submit button and after a few seconds connection is reset. No post. I open browser window again to forum and I'm still logged in but my post is vaporized.

Must be something in my post that the forum system doesn't like. Is there a file upload number limit per post?

I give up. Thought it might be a little helpful.

These short ones seem ok.
Rex Allers
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Re: Vacuum pump rebuild

Post by Rex Allers »

One last try of the message with just the text place holders I inserted for the images. No jpg images uploaded or inserted this time.

I would think if you open the actual pump chambers and find nasty surfaces, that your question about honing the inside of the stator or smoothing the outside of the rotor would be limited to very small amounts.

I think all these pumps require a very close tolerance between the rotor and stator that is set in the narrow region of the stator between the input and exhaust ports. This very small gap with the pump oil forms an effective gas seal that must be good if the pump is to work well at all. If you take even a mil or two out of that gap, the pump may not work well at all.

On the other hand, I have some experience with crapish pumps that were still useful.

--- Pump 1 ---

I bought an Edwards E2M12 from eBay -- "Like new vacuum pump in good working order. Pumps down with no issues" -- partially because the seller was local. I picked it up locally and was a bit concerned when I found myself in a semi-commercial-looking garage setting. Got it home and tested. First pass: 15 Torr! Ye gads -- that sucks in general but not very much in the vacuum sense.

More trying over a day or two, eventually it seized up.

I eventually figured out that the pump was used to extract air from fiberglass molding processes. This seems to be a common cause of destruction of pumps that find themselves to be sold on eBay. They suck abrasive glass fibers and plastic resins.

Talked with seller and eventually he agreed to refund most of what I paid and I used that to buy a major rebuild kit with vanes. Here are a few pictures from that process.
em extern yuck.jpg
Some schmutz I found early but this is actually external to the pump unit so not too worrying.

Next a pic of the inside.
em inside.jpg
Not too bad at first look but that vertical rod is a fine mesh filter. It is totally encased in the crap that was running through the pump.

One of the rotor shafts shows a bit of scoring at its bearing surface.
em shaft abuse.jpg
Not terribly bad. Nothing sensible to be done about this so I just ignored it.

Now the worst of pump internals, probably from whatever got loose and jammed to seize the pump while I was testing.

The stator.
em stator scoring.jpg
There's that one nasty small gouge from something that got into the pump. You can also see finer scoring lines around most of the surface. I also marked the region between the input and output ports where the tolerance between the stator and rotor surfaces must be very close to seal gas with the pump oil.

Here's the rotor.
em rotor gouge.jpg
A nasty mark corresponding to to the one on the stator. No idea what happened to get it to cause a dent down into the vane groove but there it is. You can also see minor scoring across the whole surface.

So I did the whole rebuild, being sure to clean gunk out of all the passages. I did a little bit of fine sanding on the rotor and stator, mostly just to be sure there were no high spots. All the valve parts, gaskets, and o-rings where replaced.

At the end of the rebuild this pump seems to run well and I am getting about 14 mTorr from this pump. Quite usable.

--- Pump 2 ---

I bought an old Welch Duoseal 1402 belt drive pump from Greg Courville on this forum. Checked it out and pump was working well. I measured about 5 mTorr vacuum. (I used a less trustworthy gauge then than my recent measurements so could be off my a couple.)

This is a 1402 with the top ballast valve and keyhole sight windows so must be very old. Maybe 70's? Maybe earlier?

I decide to do some cleanup. First I made new hard rubber feet for the base. Then I cleaned all the externals. No signs of oil leaks. The sight windows for oil level were dirty enough on inside that it was hard to easily see the oil level. I drained a little oil and got some crud coming out. I decided to open the case and do some cleaning.

Here's what I found.
01 Case Open Sludge 1.jpg
Kind of yucky. I decided to clean up what I could without opening the pump unit, that seemed to be working fine.

I took off the external valve parts and cleaned them. Here's the pump module after cleaning.
17 Clean Pump Inside.jpg
The valve parts are removed and wooden dowels are protecting the pump ports while I was cleaning.

Here's the case inside after I did lots of cleaning.
21 Cleaned Case 2.jpg
Much sludge scraped out then scoured cleaner. The inside of the oil level sight windows was one of the harder parts to clean. I also lightly milled the gasket surface flat. (I'll skip the details.) Years of people jabbing stuck gasket off had left it kind of not too flat.

So put back together it's nice and clean. With my MKS 901P sensor (I have 3 and trust them) I see about
3 mTorr. My best pump.

All the clean up work didn't change the good vacuum it started with much, if at all, but it makes it look better and should help it keep working well into the future.

--- Pump 3 ---

Just a few days ago I bought Ian's Edwards RV5 pump. He measured good vacuum, about 4 mTorr, and I confirmed the same when I got it home. I let it run for a half hour or so until it got pretty warm and the vacuum came up to about 6 mTorr, but that's still great.

It is very quiet while running too.

It looked good but I spent a day cleaning it all externally and it looks almost new again. In the process, removing side covers and such, I saw no bad signs like oil leaks or anything. From parts in the electronics of the motor start, it looks to be probably from about 1995. So probably more than 20 years old.

(But the Welch 1402 might be about 40 or more years old.)

--- Conclusions ---

The pump you have could be saveable if the insides are not bad.

If they are bad, I think most rotary pumps can't tolerate more than a tiny amount of surface removal.

A pretty clean looking pump can have major problems from contamination, but I was able to bring it back to fairly good performance.

A perfectly working pump can have a good bit of crap inside.

--- My thoughts ---

I'd clean enough to open up the pump module more easily and then see how good or bad the rotors and stators look. Also any shafts and bearing surfaces.

My E2M12 shows that slightly damaged pump internals can still make a useful pump. But I wouldn't expect very much damage could be recovered from.

The Welch pump shows that some significant crap inside that can be there and the pump still works fine.

A nice clean 20 year old pump is a lot easier than fixing or refurbishing old pumps.
Rex Allers
Bruce Meagher
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Re: Vacuum pump rebuild

Post by Bruce Meagher »

Thanks for the pictures Rex, and the data point with the small pit on your first motor.

I don't know what I was thinking last night. Clearly you can only remove a very small amount of material from the cylinder or rotor while still maintaining the oil seal at the top between the rotor and stator. We'll know more about the condition of the pump internals this weekend.

Bruce
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Richard Hull
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Re: Vacuum pump rebuild

Post by Richard Hull »

Rex did a good job on the 1402 oil reservoir. I love that he noted the vacuum didn't improve all that much, if at all.

I have always said let the sleeping dog lie. I have two 1402's here. I rate them as one of the finest pumps ever made by anyone.

I bought my first one over 18 years ago. It pumped down with dirty oil to 15 microns. I drained the oil after a 1 hour run. It was a bit rusty and filthy as well. I reloaded TKO pure oil and ran for 3 hours. Drained and the oil was murky but cleanish. I finally reload with good belt drive oil and it pulled down to 5 microns. I never looked inside. At 5 microns it is a good pump.

TKO oil is flushing oil made specifically as a thin pump cleaning oil.

The second pump I picked up at a hamfest. I could see no oil in the pump at all. The drain plug yielded about a cup of grime and sludge that oozed out. I dare not try to hand rotate the pump pulley.

I mixed TKO 50:50 with Marvels Mystery oil and filled the pump. I let it set for 1 week, after which time I tried to turn the pump wheel and it broke loose from a locked condition fairly easily. I turned it by hand for several turns and was smooth. I ran the pump for only 5 minutes and then drained a pure rust colored ruby red oil. I reloaded this time with TKO and let the pump run for a full hour and the pressure was down to 20 microns. (Marvels Mystery oil has fractions that create vapor from that first fill.) I drained again and the oil came out only slighly rusty but without sludge. A final filling with real pump oil and the pump went to 10 microns. I ran it with this oil fill on and off for a week and on the final day it pulled to 12 microns.

One final drain had the oil fairly clear of rust and just a little light gray near the end of the draining, (sludge). A final last fill with oil and the pump pulled to between 5 and 8 microns. I have left this pump sitting for 8 years. About 6 weeks ago I used it to evacuate a discharge tube that I was testing and it pulled to 10 microns after 10 minutes of gas ballasting.

Two sleeping dogs restored with no peeky up their skirts to see what was really there. For my money if your old used pump gets down under 15 microns, your pump is good enough. A nice sludge lining that allows the system to pump to that level can be left in the oil reservoir. If you change your oil in heavy use as required, it will ultimately work its way out in the draining.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher »

I took apart the pump this morning. The first picture is the pump. It is only three inches long but it does all the work. You can see the little coupler that attaches the motor to make the pump turn. The second picture is looking down at the pump. The third picture is the first stage and second stage split apart. The U shaped cutout is what connects the two stages together. The fourth picture is everything inside disassembled. I didn’t take the vanes out of the rotor yet. The last two pictures are the first and second stage chambers. They have some rust so the pump might not work well when I put it back together. I’m going to clean everything, and then put it all back together.

My dad is also going to help me learn how the pump works in more detail.

Tyler
Attachments
The pump and coupler
The pump and coupler
Top view of pump
Top view of pump
First and second stages split
First and second stages split
Pump disassembled
Pump disassembled
Second stage chamber
Second stage chamber
First stage chamber
First stage chamber
Rex Allers
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Re: Vacuum pump rebuild

Post by Rex Allers »

It looks better than one might have expected from the rust caked picture a few days back.

You might want to try electrolytic rust cleaning on the pump parts.

Hope there's still some life in it that you can save.
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Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher »

I used simple green to get the oil off the pump parts, and now they are in the electrolysis bucket. It’s a 5 gallon bucket with 1/3 cup of washing soda and 4 gallons of water. A 12V DC power supply is connected to 4 pieces or rebar. I hung the parts in the water from a metal bar. The bar is connected to the negative side of the power supply. I don’t really understand how it works, but it sure does remove the rust.
Attachments
IMG_0657.JPG
John Futter
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Re: Vacuum pump rebuild

Post by John Futter »

Tyler
your father has introduced you to the magic of reduction
in this case iron oxide is being reduced back to iron.
this process is used by vintage experts to reclaim old engine parts left out in the weather for 50 years or more.

Note to others if it is a saltwater corrosion you have to use a different electrolyte -- google it!!
Tyler Meagher
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Re: Vacuum pump rebuild

Post by Tyler Meagher »

I finished cleaning all the pump parts. I have also been studying how the different parts fit together and make the pump work. I will post more about that after I have the pump running. Below are pictures of my progress. The first one is of the whole pump cleaned and ready to be assembled. The next four pictures show the pitting on the rotor and stator. The wire in the picture is 0.004” in diameter to help understand how big the damage is. The next three pictures are the pump being assembled. Next week I’m going to attach the motor and see how well it works.

Tyler
Attachments
Pump parts cleaned
Pump parts cleaned
Rotor pitting
Rotor pitting
Rotor pitting zoomed
Rotor pitting zoomed
Stator pitting
Stator pitting
Stator pitting zoomed
Stator pitting zoomed
Second stage assembled
Second stage assembled
First and second stages
First and second stages
Assembled pump ready to be attached
Assembled pump ready to be attached
richnormand
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Re: Vacuum pump rebuild

Post by richnormand »

In my previous posting in this thread about rebuilding my Trivac D16 I mentioned the damage caused by a split-pin holding the rotor to the main shaft that disintegrated in the pump. It was mostly to the stator walls, rotor sides, vanes and they were pretty deep since the pin was made of hardened steel(similar to your photo but not as distributed) .

Two things to note here however. My pump uses vanes on the rotor. This allowed me not to worry too much about how much metal I removed from the stator (photo in previous post) and second, as stated by the rebuild manual, scratches at the ends of the rotor or the center rear bearing will cause poor pump performance. To repair these areas I used Permatex cold weld or some metal epoxy with similar expansion coefficient and adherence. It is an epoxy with metallic filling. Cleaned with methanol (hot) and acetone. Waited two days after the epoxy and machined and sanded the ends smooth while keeping the original rotor thickness identical so the epoxy only filled the damaged area. As I mentioned it has been running perfectly for 10 years now since there are little contact there apart from the pump oil.

Same process with your pump might work for you, as long as there is no metal to metal contact with the rotor in those areas. Another option is plasma torch buildup as used in repairing car crankshafts and valve lobes. Your local machinist might be of help here and hone the stator cylinder for you. Same for the rotor.

Looking forward to seeing your progress.
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Richard Hull
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Re: Vacuum pump rebuild

Post by Richard Hull »

I follow with great interest this adventure and love's labor into the attempt to restore a pump that under any reasonable and cogent examination would be instantly and unquestioningly consigned to the scrap metal pile.

If billed for labor at a mid-range figure for metal cleaning, electro-chemical activities and machining of $40.00 per hour, coupled with the supplies consumed would make the effort of saving this pump exceed the price for a brand new pump by two or three times!

It is also noted that if even only moderately successful, the "hands-on" knowledge gained and the extent of the effort involved in this attempt might well be priceless in that it will lead to successful future efforts when one is "up against the wall". The "hands-on imperative" drags one not only to greater mechanical prowess, but also to gained knowledge and advanced creativity and inventiveness as all of these skill sets are often pressed into service and even tested to their limit.

Again, this is a fascinating and heroic thread about the "doing".

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Vacuum pump rebuild

Post by richnormand »

Quote Richard:
""It is also noted that if even only moderately successful, the "hands-on" knowledge gained and the extent of the effort involved in this attempt might well be priceless in that it will lead to successful future efforts""

Have to agree with Richard about this. After my rebuild success I have come across a few pump repairs and even a turbo pump bearing change with a lot more confidence and it was quite worthwhile. In addition the knowledge and tools acquired (that had to be paid for only once) but keep on being useful in the workshop quite often and have "repaid" themselves many time over, for pumps to dishwasher to car repairs etc...

Can't wait to see what performance you get out of it. And, if not to your liking, nothing prevents you to get in there again (should be much faster) to rectify the issue.

Note: should you get acceptable performance don't forget to change the oil after a while to get rid of impurities and metal bits before putting it in regular long term service.
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