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Old 22nd August 2011, 10:37 AM   #31
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Quote:
Originally Posted by PhilippeS View Post
See the video on this page and maybe the manufacturer can help you

http://paillard.claude.free.fr/

Philippe
Thanks for the link!!!!!


It's pure art ...
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Old 22nd August 2011, 07:30 PM   #32
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Homemade Vacuum Tube
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Old 23rd August 2011, 04:06 AM   #33
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Interesting DIY diffusion pump! Somehow missed that in the earlier thread. Have you made any performance measurements? How many Watts to operate the heater? I was shocked to see the restored prices for a Varian HS-2 diff. pump recently, several times what I paid for a new one 30+ years ago. I used to see old diff. pumps at the scrap metal yard years ago, could buy rusty ones for $0.50 a pound scrap metal price. Maybe just local supply and demand before Ebay came along.
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Old 23rd August 2011, 08:04 PM   #34
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The heater power is about 120 watts. As far as testing goes, I've chosen to make a useful chamber arrangement to accommodate the gauges and flow meters needed to qualify the pump. This pump and chamber should be quite universal for an assortment of small vacuum experiments including the pumping of homemade vacuum tubes.

The point of the whole exercise is to demonstrate that a working high vacuum system can be fairly easily constructed without having to plug in any power tools or use anything exotic in the way hand tools. This is a truly handmade pump and chamber.

Here's a look at where things stand so far: Fusor Construction & Operation - Download complete thread
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Old 27th September 2011, 03:42 PM   #35
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I came across a US patent (#5137429) for reducing power consumption in diffusion pumps. It uses a thermally insulating ceramic collar between the heater and the cooled outside cylinder of the diffusion pump. Seems that one could just arrange for a Viton "O" ring with some flanges to do that. Fiberglass bolts to hold the flange together. Or a T shaped Viton circular gasket with some hose clamps around the outside.

I came across the thermal collar term for a Veeco EP3AB diff pump, but it does not seem to be of reduced power consumption. But I do notice Edwards makes the TVA50/60, which uses only 80 Watts and has an obvious mod to the boiler to cooled cylinder interface. (other similar pumps use 200 to 250 Watts) No mention of how it works in their literature.

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A little off topic, but I just obtained a Pfeiffer TPH060 turbo pump for cheap and it needs the bottom bearing replaced. The official tool kits to do this are like $750 and the replacement bearing kits something like $450 to $650. So I proceeded to see how far I could get without any special tools. After removing the bottom bearing cover I found the bearing had lost its plastic spacer between the rollers.

There is a long conical tapered nut that holds the bearing to the shaft. It has only a tiny 2 mm Allen Hex wrench fitting on the end. After bending up several Allen wrenches, I tried contacting several of the pump repair outfits to inquire if this was a normal right hand thread nut or a special left hand nut. (since the operating shaft rotation would tend to unscrew a normal right hand thread) The ones that did reply essentially told me to pay the $1000+ and offered no help (top secret apparently). Well if one can't get the old bearing off, there is no point in buying a new one! I would just order the bearing from a bearing manufacturer anyway for < $100.

I am thinking maybe the threading is left handed. Or the previous bearing changer used Loc-tite or something on it, or the special tool kit has a conical female taper tool that gets hammered onto the outside of the nut (instead of using the tiny Allen wrench fitting). (Pfeiffer mis-conveniently deleted the bearing change instructions from the turbo user manuals of all their products a number of years ago.) Any help on this would be greatly appreciated!! If I knew for sure which way to turn the nut, I would try heating the nut to loosen it. A big soldering gun with some #12 copper wire configured to wind around the nut should do.

I do have an old TPU050 manual in storage up in Ct., which likely had the bearing change instructions still in it. But I won't be getting up there till next Spring likely. Worst case would be to just take some Vice-Grips and remove it, but I fear that might bend the shaft (90,000 RPM!), plus I would have to obtain a new tapered nut, or machine one. Wouldn't be too hard to machine one from some threaded SS spacer rod, but if its a left handed thread....

If it does turn out to be economical to repair the usual (damaged, dead ...) Ebay turbos, then this would be a viable solution to setting up a high vacuum system such as the original poster needed.
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Old 27th September 2011, 06:05 PM   #36
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OH, if I do get the Vac pump up and running, I plan to make some TiO2 cathode heaterless vacuum tubes for an efficient OTL amplifier. 20 or 30 amp emission triodes should work well. Seeing as how none of the current tube makers have taken up the heaterless tube technology, maybe I will start selling them too.
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Old 27th September 2011, 06:06 PM   #37
Matt BH is offline Matt BH  United Kingdom
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Smoking Amp, could you post a photo of the bottom bearing?

If it has been Loctited then heating it and letting it cool could do the trick. Tends to work, it expands the thread then contracts on cooling cracking the Loctite.

Some of the guys who build and repair model jet engines use ceramic ball bearings. A Google about may find a suitable size and supplier. Some of these little engines spin at 120,000RPM!

Cheers Matt.
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Old 27th September 2011, 06:34 PM   #38
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Here are some pics:
Only the inner race of the bearing is still in place yet at the bottom 1/4 inch of the nut. I was able to remove the outer race and balls already. Some pics have the Allen wrench in place at the end of the tapered nut.
Attached Images
File Type: jpg turbo1.jpg (16.3 KB, 84 views)
File Type: jpg turbo2.jpg (18.9 KB, 83 views)
File Type: jpg turbo3.jpg (24.0 KB, 82 views)
File Type: jpg turbo4.jpg (22.8 KB, 83 views)
File Type: jpg turbo5.jpg (19.1 KB, 82 views)
File Type: jpg turbo6.jpg (19.8 KB, 13 views)
File Type: jpg turbo7.jpg (22.3 KB, 15 views)
File Type: jpg turbo8.jpg (23.0 KB, 19 views)
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Old 27th September 2011, 06:46 PM   #39
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Some profiles:
Attached Images
File Type: gif Turbo_A.gif (100.2 KB, 18 views)
File Type: gif Turbo_B.gif (21.8 KB, 15 views)
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Old 27th September 2011, 07:16 PM   #40
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The easiest way to "make" a vacuum tube: Take a bifilament car bulb with convenient geometry. Distroy one of the filaments (the lower power one). The result is a very basic direct heated triode (good enough for school demos).
Building high-performance vacuum tubes is a serious challenge. It requires deep knowledge of physics, chemistry and matheatics, not just some cookbook recipes. I've worked a few years in that field (SEL).
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