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Vacuum Pump Mount and Arrangement

Discussion in 'Woodturning Discussion Forum' started by Timothy Allen, Sep 14, 2020.

  1. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I don't know anything about the Thomas 2660 vacuum pump specs, but Gast rotary vane vacuum pumps do have a shutdown procedure in the Operation and Maintenance manual. The procedure is to first run the pump open port for five minutes (open port means all plumbing completely disconnected from the pump). Next, the pump is run blocked port for ten minutes (blocked port means the vacuum port is closed with a plug or valve). And, finally run the pump for five minutes open port.

    If you don't receive a manual with your vacuum pump I'm sure that it can be found on the Thomas website. I believe that the purpose of the shutdown procedure is to clear any residual moisture from the pump and to cool the pump down.

    I loosely follow the shutdown procedure sometimes, but not always. I have a 1/4" NPT brass T installed on the vacuum port of my Gast pump with ball valves on the other two legs of the T so that I can easily do the shutdown procedure without disconnecting the plumbing from the pump. I would guess based on past discussions that most woodturner owners of Gast rotary vane vacuum pumps have never heard of the shutdown procedure and wouldn't follow it anyway.

    This isn't an issue with rotary vane pumps because the vacuum disappears as soon as the pump is turned off. This is because there are no valves unlike piston or diaphragm pumps. When a rotary vane pump stops the vanes no longer are extended by centrifugal force and therefore the vacuum side is open to the ambient air pressure.

    Even with piston and diaphragm pumps the vacuum will quickly disappear because of system leaks ... mostly around and through the wood, but also leaks from the bleed valve and rotary coupler.
     
  2. Lou Jacobs

    Lou Jacobs

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    Thanks for this clarification Bill. The pump arrived yesterday, and I’m now putting together an order from McMaster and possible Surplus Center. I imagine I’ll have more questions as I move along.
     
  3. Lou Jacobs

    Lou Jacobs

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    William,
    In your post number 32, the photo that shows the view of your pump (Copied below, I hope) with the labels, I feel like I’m seeing some kind of mirror image on the top right side of the pump - just to the left of the hose barb. Am I hallucinating?
    here is a picture of the top of my pump. I wonder if I can impose upon you to tell me what label each of your connections has? A, B, E and F. Thanks loads! upload_2020-9-24_12-42-34.jpeg




    AED6524F-CB25-4844-B8F3-3196121BEA1A.jpeg
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Are you referring to this:

    image.jpeg

    It appears that a small snippet of the image was copied and pasted on top of the larger image.
     
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  5. Lou Jacobs

    Lou Jacobs

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    Yes. That’s it! Can you tell me which orifice (A, B, E, or F) your nose barb muffler, and your vacuum line are connected to? Thanks!

    whoops! I see you’re Bill, not William. Sorry.
     
    Last edited: Sep 24, 2020
  6. Larry Copas

    Larry Copas

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    A 3 way valve from McMaster Carr on my shop made rotary adapter.

    This picture the lever is in vacuum mode.
    IMG_3269.JPG

    This picture the lever is in the off position.
    IMG_3270.JPG

    This picture the lever is in the up position. Vacuum is off but the valve is letting in air from the top so I get immediate release at the vacuum chuck. Makes it easy to re-position a piece to run true.
    IMG_3271.JPG

    I use a needle valve with a filter downstream to reduce pressure.

    I should also add quick connects are air flow direction sensitive because there is a spring in the female coupler. Make sure you get it right or they will fail after a while. Also PEX fittings work perfect on the hose we use and make for a neater, easier installation.
     
    Last edited: Sep 24, 2020
  7. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I removed the quick connectors from my system after I learned that there is a significant pressure loss across these connectors.
     
  8. Timothy Allen

    Timothy Allen

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    So are you saying that on a vacuum system, the connectors should be set up in the opposite sense from how they are typically set up on a compressed air system?
     
  9. Bill Boehme

    Bill Boehme Administrator Staff Member

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    The direction of air flow would be the same, but in an air compressor the flow is away from the pump and in a vacuum pump the flow is towards the pump.
     
  10. William Rogers

    William Rogers

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    Bill is good, That is exactly what happened. I just didn’t notice it. It is a piece of the motor. 5829F78A-A537-4CD9-B01F-6CAD95DD2984_1_201_a.jpeg
     
  11. Lou Jacobs

    Lou Jacobs

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    Thanks William. It looks to me like the vacuum hose is in position “F” and the hose barb exhaust is in “A.” Have I got that right? I’m about to go out and assemble my system. Keeping fingers crossed...
     
  12. Tom Gall

    Tom Gall

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    I think if you just turn it on you will be able to determine which is which by placing a finger over the ports. Some of them may already have plugs installed. Regarding the 'hose barb exhaust' (technically that is not a hose barb but a quick-connect fitting - either will work) if you add a piece of hose/tubing over the fitting it will decrease the exhaust noise even more (longer - less noise). Or you can add one of these mufflers if you prefer. :)

    https://www.mcmaster.com/9835K42/

    https://www.mcmaster.com/4450k2
     
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  13. Lou Jacobs

    Lou Jacobs

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    Tom, thanks! I figured that out. It was a bit confusing at first because of the multiple fittings attached to my used pump. apparently it was used as a goat milking pump before offered for sale on eBay!
    Here is the muffler I had ordered from McMaster Carr:
    CC3DE93D-E6C4-4A6B-82B0-E917482C105F.jpeg 5E92395B-8CD6-4A19-B13F-4AAC7E7CE396.jpeg AE6E000F-9940-4D2E-98C6-CB452EBF324F.jpeg https://www.mcmaster.com/4450K2
    My system is now up and running, and working well. It draws about 23# of vacuum when all closed up. I think I’m going to move the manifold further to the right, away from the headstock, as I’m not comfortable with it directly in line with the chuck/work on the lathe. I also intend, as you recommended, to install an air regulator for fine adjustments. But for now, very gratifying to see that all works and holds a vacuum. I shut off the pump with a test bowl on the lathe and had ten or so seconds before it lost vacuum and released the bowl, which is real good to see. I’d pictured having the bowl fly across the room if ever there would be a sudden power loss. one thing I don’t think you can see on these pictures is that I also installed an auto fuel filter between the pump and the headstock adapter.
    I welcome any comments on my setup from those of you (everyone!) more experienced with vacuum chucks than me.
     
  14. William Rogers

    William Rogers

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    Lou, your system looks great. Note that wood is very porous. If you have not already seal your wooden adapter components. Also if you make any homemade chucks seal the wood on those. It takes at least two coats of sealer. The Thomas pumps are good and you can get 28 i. hg. from a fresh rebuild. 23 will work fine for what we do in wood working.
     
  15. Lou Jacobs

    Lou Jacobs

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    Yes, William, I’ve sealed the wooden components with polyurethane. Also, you can’t see it, but I’ve got a rubber O ring in a slight groove between the hand wheel adaptor and the wheel. I’ve thought it might be a good idea to get the rebuild kit for the pump. After all, I don’t know how much goat milk the thing has sucked!
    (Edit) as I think about it, the one piece that’s not sealed is the small purpleheart Hose barb at the adapter. I can’t imagine I lose much there, but worth coating that too.
     
  16. William Rogers

    William Rogers

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    Lou, you would be surprised how much vacuum you could loose. I know from experience a lot more than you think. I’m generally pulling 26 in. hg + on my system, but I have rebuilt it.
     
  17. Steve Fairbairn

    Steve Fairbairn

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    This is my vacuum chucking system on my Oneway lathe. My apologies for the rather busy photo but there's a lot going on behind my lathe. The vacuum pump is inside a plywood box on the floor behind the lathe to keep dust and shavings off. On top of the vacuum pump box is a muffler. The pump and motor are relics from the 1960's and came with the vacuum chucks and spindle adapter when I bought them secondhand. The hose from the pump is connected to the bottom of the vertical black pipe that is fastened to the lathe such that it can swivel. The gauge and valves are connected to the top of the black pipe and there is another connection that goes down to a 5 gallon tank under the lathe (buried in shavings) acting as a reserve in case I lose power while turning. The tin can you can see behind the headstock is just a storage receptacle for the Oneway vacuum adapter that threads onto the lathe spindle. Obviously, I need to remove the handwheel first. Above the headstock, looking from the front, there is a manifold with a bleed valve, a valve to shut off the vacuum and a connection to the lathe spindle and reserve tank. The remote control dongle hanging from the vacuum gauge is for turning the vacuum pump on and off. You'll notice that I am using compressed air quick connects for all of the hose connections because I also use the same pump and valves for my vacuum chamber and vacuum press.

    Vacuum Chuck Plumbing Back.jpg Vacuum Chuck Plumbing Front.jpg
     
  18. Bill Boehme

    Bill Boehme Administrator Staff Member

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    It's not unusual for a bowl to stick to the vacuum chuck after the vacuum is shut off. as William said, you will be surprised at how much air is sucked through a wooden bowl. Sanding dust and uncured finish can get sucked right through the wood.

    Hopefully, you used at least two double sealed bearings as well as shaft seals in your rotary coupler. If you didn't, the grease will be sucked out of the bearings and then it will become a huge point of air leakage. You can substitute thin rubber washers for the shaft seals.

    How much vacuum your system draws will depend on your local elevation. If memory serves me correctly, you lose roughly an inch of Mercury vacuum per thousand feet altitude above mean sea level.
     
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  19. Lou Jacobs

    Lou Jacobs

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    No, I just used a single bearing. I don’t think that’s something I can change now that the bearing and hose barb are seated with epoxy. I’d read about bearings being sucked dry, and several responses I’d read stressed relying on American made bearings. Where would you place a rubber washer? Under the bearing? I do have an o-ring between where the coupler mates to the handwheel, but that would only serve to be sure that vacuum does not leak before the bearing.
    (Yes, the standard pressure drop is 1” of mercury/1000’ of altitude. Pilots adjust their altimeters, and calculate pressure altitude that way. Standard pressure at sea level, 29.92 inches, becomes 28.92 at 1,000 ft., etc. why water boils so much cooler at high elevations, and why scuba divers blood “boils” if they ascend too quickly.)
     
  20. Tom Gall

    Tom Gall

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    Lou, you can check for leaks by covering your wood parts with masking or electrical tape (more flexible) and see if there is any change in your gauge. Your adapter is a little fancy to cover with tape - if it was just a cylinder it would be easier. If you notice any improvement you can add more polyurethane or just leave the tape! :) Assuming you're using the spindle as your vacuum tube you can make a rubber cover plug or just use the palm of your hand over the spindle. That will eliminate any possible leakage from your chuck - or - use a non-porous surface (pc. of plexiglass or plastic dinner plate) on your chuck. Also I would recommend you place your ball valve before the gauge - between the pump and the gauge.
     
  21. Tom Gall

    Tom Gall

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    Lou, a single bearing will work just fine. My homemade version has been working very well for many years. My first and only commercial adapter was the E-Z Vac Adapter (purchased in 1994 from Packard) and it has only one bearing. Just make sure you use a sealed bearing.
     
  22. Lou Jacobs

    Lou Jacobs

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    Thanks Tom. Your suggestions, as well as all others here, have been very helpful. I’m just in from the shop where I put a coat of sealer on the hose barb on the adapter. I also moved the manifold over To the right side of the headstock. I’m getting 25 inches of vacuum when I run it with my finger over the headstock outlet, and it takes about thirty seconds for vacuum to bleed away after cutting off the pump. I’ll watch for that to change over time, possibly indicating that the bearing is being sucked dry, I’m now making a motor-mounted bracket to hold the hose in line with the adapter, to take any lateral pressure off the bearing.
     
  23. Bill Boehme

    Bill Boehme Administrator Staff Member

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    The washer would go on the high pressure side of the bearing. The washer should be about the same diameter as the bearing and the hole diameter should fit snugly on the shaft. Then put an O ring on the shaft to keep the rubber washer against the bearing. The main reason for having at least two bearings in the rotary coupler is to keep the shaft from flexing. Even the slightest amount of flexing distorts the bearing races and causes the labyrinth seals on both sides of the bearing to open slightly allowing a big air leak as well as sucking the grease out. A secondary advantage of using multiple bearings is that the differential pressure is divided equally across each bearing which reduces the likelihood of the of the labyrinth seals blowing out.

    There are bearings made in Japan that are are also high quality, but you just need good bearings. Shaft seals are cheap and an easy solution to sealing against leaks. However, they won't work with a purpleheart shaft. I buy brass pipe nipples and other plumbing fittings and then turn them down to the inner diameter of the bearing.

    It's probably been 25 years since I I had to quit flying due to health issues so my aviation memory can stand to be fact checked.
     
  24. Bill Boehme

    Bill Boehme Administrator Staff Member

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    If it's a design like the E-Z Vac then a single bearing is fine.
     
  25. Lou Jacobs

    Lou Jacobs

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    Here is the tubing holder I made, showing the jaws open and closed. I made it from the design in Doc Green’s book. It keeps the tube from flexing while rotating. It allows for quick removal of the adapter when it’s not in use. The adapter drops easily into the tool holder on the leg of the lathe just below.

    Regarding the discussion about quick-connects and loss of pressure, I suppose a simple, but more parts-intensive solution for having a line available for a vacuum chamber or the like is to put in T with a second cut-off valve and hose. B010C88C-3FF2-4424-9F58-82B804E6AC06.jpeg B48CAC34-5F40-464A-86CD-FD902B2936C7.jpeg
     
    Last edited: Sep 27, 2020
  26. Dave Landers

    Dave Landers

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    So somewhat related... your tape suggestion reminded me... I keep a roll of the stretch plastic film around (like kitchen plastic wrap, but used for wrapping boxes to keep em on the pallets - you can get it at Home Despot etc). I use it to wrap around a bowl or hollow form and the vacuum chuck if the bowl is leaky or has a few bug holes etc. Can help with the leaks and also adds a bit of support. Can then tape over the wrap without getting tape-glue stuck to your piece.
     
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  27. Lou Jacobs

    Lou Jacobs

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    Bill, I got a pilot’s license in high school and flew through college. Met my wife my senior year (45 years ago) and at that point put flying on a back burner as I had other needs for any available $$. I’ve had a few hours here and there since, but nothing serious. I keep thinking I’d love to take it up again, but it’s a different world now.
     
  28. Lou Jacobs

    Lou Jacobs

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    Dave, that’s a great idea! Thanks!!
     
  29. Tom Gall

    Tom Gall

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    Yes, that works well. I have a 2" wide and a 6" wide roll - have used it more that a few times in the past, especially if there are holes or inclusions. Usually I have a turning already sealed or finished before I get to the point of using the vacuum so there isn't a leaking through the wood problem.
     
    Last edited: Sep 27, 2020
  30. Tom Gall

    Tom Gall

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    Nice tubing holder....but I don't think you need the clamp. Having the tubing just resting parallel to the floor is enough so as to not put any undo pressure on the bearing. There shouldn't be any flex in the tubing - maybe just a little movement if your adapter fitting isn't perfectly true (not really a problem). Tighten the screws on your arms and that should be enough friction to hold it closed.....or add a rubber band or a sleeve of sorts. Just my 2¢. :)
     
  31. Lou Jacobs

    Lou Jacobs

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    I get your point, but the clamp ensures that the hose goes straight towards the adapter, rather than following an arc slightly pulling up, granted very slightly, on the bearing. I think it’ll be less trouble to clamp on the spring clamp then to take a screwdriver to it. All of a moment.
     
  32. Tom Gall

    Tom Gall

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    No biggie here, Lou. Maybe I wasn't clear in my explanation. Use your wooden fixture as is for alignment. Tighten the screws enough for friction so you can open and close the arms with your fingers....no pressure on the tubing is necessary and you won't need a screwdriver every time. Either way....it's your set-up - do what makes you happy! :)
     
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  33. Lou Jacobs

    Lou Jacobs

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    I understand Tom. I’ll start using the system and see how things work best for me. I haven’t yet done any new turning since beginning this project. Next (last?) step is to make a cover for the pump to keep it dust and chip free when not in use. Actually the box that it was shipped in fits pretty well, but I think it deserves something a bit more finished than a cardboard box.
     
  34. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I wouldn't put the vacuum pump in an enclosure. If it's like the Gast they get quite hot even in the open. My Gast needs air at room temperature for cooling the motor. If it were in an enclosure it would only get hot air. Just set the pump where it won't get buried in shavings and don't worry about dust. The Thomas pump might be different and not run as hot.
     
  35. Lou Jacobs

    Lou Jacobs

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    Absolutely agree Bill. The cover is only for when the pump is not in use.
     
  36. Ric Williams

    Ric Williams

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    This thread has been a huge help in figuring out what I need for my vacuum chuck system. The pump (Gast 0523) and manifold parts are arriving today and my rotary adapter and chuck are finished. The manifold will have a needle type bleed valve and a ball valve for vacuum shutoff, filter at the pump, no quick connectors, and every other recommendation from this thread that I could incorporate. One operational question remains. Is it bad for the pump to be on while the vacuum is cut off by the ball valve? Obviously, I wouldn't leave it running that way any longer than needed, but I'm curious what effect that has on the pump.
     
  37. Gary Beasley

    Gary Beasley

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    Running with the valve shut will cause heat to build up a little in the vane chamber, but it has cooling fins built into it for that reason. Gast pumps were used extensively in the graphic arts field for contact printing frames in the darkroom and platemaker. In this case the vacuum is drawn to max and held there during the process so the pumps can take it. The vanes are graphite or some kind of composite for low friction so heat buildup is the sign of stress on the pump. Keep an eye on that and you should be good.
     
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  38. Lou Jacobs

    Lou Jacobs

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    Ric, I’m hardly an expert, so take this with a grain of salt. I recently built my system, with much advice from here. I’ve only finished three bowl bottoms with it so far, but it’s been working great. I did decide to go with quick connect fittings, as, like Steve (above) mentioned, I want to be able to, at some point in the future, use the pump to evacuate a vacuum chamber for stabilizing wood. I added those after first using the system on one bowl, when I realized I already had the fittings from an old compressor I no longer use. After installing the quick connects in the vacuum line, I experienced the same 24” of vacuum in my system. It still holds the vacuum for a good 30 seconds after turning off the pump. I realize that this may change over time, but I’ll keep my eyes on the gauge and watch for leaks. Good luck with yours!
     
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  39. Ric Williams

    Ric Williams

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    Thanks Gary, that's what I was hoping to hear. The pump seems to max out at 22", so it may need a rebuild kit if I find I need a little more vacuum, though I suspect it'll be fine as is, for anything I'm likely to be working on in the foreseeable future.
     
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  40. Gary Beasley

    Gary Beasley

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    My Gast goes to about 24” tops, and it can pull a very good vacuum on my chucks. Its a 15 cfm rated pump so any small leakage in the system tends to be overcome by that.
    If you want to do stabilizing one of those pumps used for evacuating ac systems works great and can usually be found fairly cheap used. They will pull up to 30” or a tad more on a good day. My Robinair pump will make water boil at room temperature from the pressure drop.
     
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