My Turbo and Homemade Driver

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.
Post Reply
Nnnnnnn
Posts: 58
Joined: Tue Jun 13, 2017 6:25 pm
Real name: Niels Geerits

My Turbo and Homemade Driver

Post by Nnnnnnn »

I would like to share my turbo and the driver I made for it. The pump is a used Pfeiffer TMH064 from Bulgaria that I found on ebay. The pump has a centertapped motor so the driver was pretty easy. I found that someone on this forum built a driver for a similar pump, so I built forth on that (original thread viewtopic.php?f=10&t=4036). I used an LM358P to amplify the 400mV coming out of the Hall sensor to 3.5V. This output is sent to a digital pin of an arduino. Two other digital pins are used to control the gates of two N FETs. Other than that my driver is the same as Alexi's. I tested the pump at low frequency in air (before I do anything in vacuum I want to make sure that my TC reading is correct). I know you are not supposed to, but I had to test it and figured if I did a slow test I would not damage anything. Here is a video of the pump starting up (I filmed it for the sound):

https://www.youtube.com/watch?v=rNelG-ngSPw

And here a rough drawing of my circuit:
turbocircuit.jpg
The frequency was below 100Hz. To me it sounds like two things might be grinding together as the blades spin, however I have heard this in other turbo pump videos. Something I haven't heard yet is the low hum mine makes.

I was wondering if someone with more experience with turbos could tell me if it sounds normal and if not what the most probable cause is (oil bearing etc.)?
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

Bearings are shot.
Nnnnnnn
Posts: 58
Joined: Tue Jun 13, 2017 6:25 pm
Real name: Niels Geerits

Re: My Turbo and Homemade Driver

Post by Nnnnnnn »

Sounds like I have another project on my hands then. The pump has an oil lubricated bearing and a magnetic bearing. My guess is this magnetic one is fine (don't see how it could wear. correct me if I am wrong) and only the oil lubricated one needs to be replaced Do you know if any specialized tools are required to take apart the pump to replace the bearings?
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: My Turbo and Homemade Driver

Post by Dennis P Brown »

I have (successfully) taken apart turbo's and removing a bearing is not easy. Be very careful not to bend or break the blades - they are very brittle. Also, blades often are not interchangeable and sometimes (mine for instance) not only is the order critical but mine used two different sets of insert blades! So keeping track of how they went in (order), what the blades look like is important; and do draw/note the correct order for the re-assembly.

Most general tools will break a pump down (allen and screw drivers) but pulling a bearing is not easy nor simple in all cases (might need a bearing puller to get it off the shaft - especially if it has over heated.)

The oil for a turbo bearing is very expensive and you might have to have that with a new bearing (keep that in mind.) Cleaning afterward may be necessary - read up on how that is done for your pump (mine allows immersion but the bearing then has to be re-oiled ... .)

That all said, have you tried the pump pulling vacuum against a high vac gauge? It might work well. Also, maybe just re-oil the bearing? Finally, never again run your turbo in air - that is a really great way to bend the blades! Even slight bending can damage those pumps (yes, some can tolerate some air but unless you know for certain, just don't do it.) So, always run it with power only under vacuum.
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

If this is like my other pfeiffers it is pretty easy. You pull out the oil cart from the bottom, there is a cone shaped nut with an hex hole for an allen wrench. you need to hold the rotor still to unscrew it. There should be something else retaining the outer race. The bearing should pop out from there. There is no need to take the whole pump apart.

Now you need to get a bearing. The one out of my big pfeiffer (1000l/s) was a standard size with a special ball retainer. I ordered another ABEC 7 ball bearing from a supplier in Cali and swapped retainers.

The smaller one I have (500l/s) is a different story, it is a custom bearing so I am going have to get creative with that one. It basically has one side of the race integrated into a 1mm thick shield, all one piece. So I am going to have to get a stock bearing and add what will basically be a precision washer to one end to space it out.

I dont know what the situation with the little bearing in the pump you have will be. You can get a off the shelf replacement from Alpine Bearing. Probably going to run $1-200. Then you will need a new oil cartridge which is about $75.
ian_krase
Posts: 636
Joined: Mon Nov 28, 2016 2:48 am
Real name: Ian Krase

Re: My Turbo and Homemade Driver

Post by ian_krase »

Does Alpine Bearing have it?
John Futter
Posts: 1848
Joined: Wed Apr 21, 2004 10:29 pm
Real name: John Futter
Contact:

Re: My Turbo and Homemade Driver

Post by John Futter »

As far as I know
most turbo makers use custom bearings and if you learn a bit about bearings they are right on the edge of what a bearing can do vs speed.
Leybold seem to use Bardin bearings from the UK and I have tried to buy
but they wil not sell and divert you to leybold
Boca bearings have some bearings close in dimensions but not the same
might be worth a punt
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

Looking at the cross sections for the tmu071 and the 065 I am pretty sure they use the same bearing. here is the bearing for the tmu071p. It has one of those integral shields like the other bearing I have to replace has. https://alpinebearing.com/ball-bearings/yc1340tphw6/

Give them a call, they were helpful the last time I called, I never got any response from their online form. They should be able to tell you if that is the right bearing. Alpine bearing is who supplies bearings for the rebuild kits for places like PCH Chemlabs. Their search engine for the website sucks.
Nnnnnnn
Posts: 58
Joined: Tue Jun 13, 2017 6:25 pm
Real name: Niels Geerits

Re: My Turbo and Homemade Driver

Post by Nnnnnnn »

That was helpful. I did not recognize that the conical thing had any grooves for an allen wrench last night, but you are right. I found that by removing the four screws that connect the bottom part of the pump to the central part something pops loose and you can no longer turn the blades by hand, however it appears that if I turn that conical nut hard enough the rotor will still turn. So I will have to come up with something else to keep it still.

I have had contact with both Pfeiffer and Alpine Bearings and got quotes from both for replacements. It is likely that I will only have to replace the lower bearing. Once I remove the old one I will order a replacement.
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

Yeah, the top bearing is magnetic so there is no contact and nothing to wear. When you release the bottom beating the rotor will be pulled up by the magnets.
Nnnnnnn
Posts: 58
Joined: Tue Jun 13, 2017 6:25 pm
Real name: Niels Geerits

Re: My Turbo and Homemade Driver

Post by Nnnnnnn »

So I removed the conic nut and the top came right off. I can see the bottom bearing but it won't budge. I have tried pushing it out from the top with an allen key but as I said it will not move at all. So I think that it must be retained by something else, however I have no idea what is holding it in place. All the drawings do not mention anything. In addition the TPU 170 manual (different pump) has a guide with pictures. In that guide it also seems like the bearing should come straight out.

Edit with some extra info. I have a hunch what maybe holding the bearing in place:
tmh.png
In this drawing you can see that there is some kind of retainer below the bearing. I checked the holes that I circled red and found that they are threaded. So I think I could pull the retainer out if I put some screws in there and pull on them. But it is hard to tell because the holes are very small. However I would also think that pushing from above would force the bearing and the retainer out (but that hasn't worked and I do not feel comfortable applying more force).

Second edit: After further examination it could be that the retainer is being held in place with very small hex screws. But despite good eye sight it is impossible to be sure.
Peter Schmelcher
Posts: 228
Joined: Sat Nov 13, 2010 1:56 am
Real name: Peter Schmelcher

Re: My Turbo and Homemade Driver

Post by Peter Schmelcher »

Niels attached are some pics of a tph 055 that might provide some useful insights for your repair. Mine was missing the other bottom parts when I got it. BTW the tph magnetic bearing also has a 6x13mm ball bearing for takeoff and landing.

I investigated high speed ball bearings some time ago. The only inexpensive types I know of are for dental equipment which has fantastic rpm but unfortunately limited sizes.

-Peter
Pump bottom shaft
Pump bottom shaft
Bottom shaft in pump body
Bottom shaft in pump body
Attachments
Magnetic bearing with C-clip removed
Magnetic bearing with C-clip removed
Ball bearing inside magnetic bearing with preload washer and C-clip removed
Ball bearing inside magnetic bearing with preload washer and C-clip removed
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

You need a pin spanner to unscrew the piece that is holding the bearing in place. I have gotten away with finding two drill bits or dowel pins that fit snugly in the holes and grip the both as close to the surface as I can and unscrewing it. It shouldn't be that tight, it does not need to be. If that does not work measure the distance between the holes with a digital caliper and take a small bar of aluminum that will fit in the recess where the plastic cap was and drill two holes to match for pins. Probably something like 1/2" thick, 3/4" wide and about 2" long.

You could also try something like this: https://www.amazon.com/Andoer-Professio ... ench&psc=1
Nnnnnnn
Posts: 58
Joined: Tue Jun 13, 2017 6:25 pm
Real name: Niels Geerits

Re: My Turbo and Homemade Driver

Post by Nnnnnnn »

After hours of cursing I finally did it. The retainer came out using an aluminum bar with 2 holes drilled into it, 2 allen keys fit into those holes, which also went into the holes in the retainer and a wrench to hold the aluminum bar and apply the torque. The retainer was so tight that the torque bent the aluminum bar and broke a piece off of my low quality allen key.

The bearing, o rings and anti vibration ring had a phenomenal amount of black and yellow crud on it. I gave the bearing a spin in my hand and was able to feel the friction (there is probably crud inside of it which would destroy the bearing at high speed). It did not look like any of the balls were missing though.

In addition the interior of the pump had a criminal amount of backing pump oil residue inside of it, which I cleaned out. I still have to clean the upper stage. According to the manual you can just dunk it in some alcohol.

On monday I will ask Alpine to send me a replacement. Pfeiffer recommends to replace the anti vibration ring, but mine seems fine so I will probably just re-use it. I will also have to order some oil.

Peter thank you for the images. That ball bearing close to the magnetic bearing is an emergency bearing as far as I know. It can save the pump should the magnetic bearing fail. Those takeoff and landing bearings also exist in those fancy hipace pumps that use active electromagnetic bearings. I have been told that sometimes this emergency bearing needs to be replaced. But first I will just replace the lower bearing and see if that gets rid of the strange sounds.
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

You dont order oil, you replace the cartridge. The landing bearing on top is just for if the machine the pump is attached to gets hit or something while the pump is running, these pumps are not like maglev pumps which set the rotor down on a bearing when it is shut down. On my big maglev (2000l/s) I you get 5 landings at high speed before you have to replace the bearing. I have the turbo on a UPS to make sure I never lose power while it is running.
Nnnnnnn
Posts: 58
Joined: Tue Jun 13, 2017 6:25 pm
Real name: Niels Geerits

Re: My Turbo and Homemade Driver

Post by Nnnnnnn »

Oil cartridge and lower bearing have been replaced with pfeiffer parts. Most of the sounds are gone, however I think I may have messed something in the upper stage up. Before I replaced the bearing I opened the upper part of the turbo to look at the rotor. I did not take anything apart I looked at the magnetic bearing and then put the upper part with the flange back on. Locked the screws which push the magnetic bearing down and thus mounts the blades on the bearing. Then today I put in the new lower bearing and put the pump back together. Once it was reassembled I gave the upper blade a push and noticed that the friction had severly increased! The blades spin and then come to a rather abrupt halt. Here a video:

https://youtu.be/zn0KrE6dhJk

If I put my ear on the flange I can kind of hear the friction. It is obvious that the source is somewhere in the upper stage, but I am not sure what exactly the cause is. Anyone have any idea what I did wrong?
Jerry Biehler
Posts: 975
Joined: Tue Nov 24, 2009 3:08 am
Real name:
Location: Beaverton, OR

Re: My Turbo and Homemade Driver

Post by Jerry Biehler »

I think it is fine. You are going to need to run it up to speed and see how it does.
Post Reply

Return to “Vacuum Technology (& FAQs)”