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Gunsmithing Vacuum Pumps

LRI

LRI

Lance Criminal
Full Member
Minuteman
    • Mar 14, 2010
    6,321
    7,503
    53
    Sturgis, S. Dakota
    www.longriflesinc.com
    #1
    Short of a 5 stage dry sump pump, I don't know chit about these things.

    I want to stick "something" in a big bag and pull a vacuum on it so that it pulls down tight around it.

    Anyone familiar with this sort of stuff? I need edumacating on it.

    Thanks.

    C.
     
    #3
    Are you talking about something like the vacuum storage bags that have a fitting that you hook a regular vacuum cleaner up to? My wife has used them to store clothes more compactly.
     
    #5
    When I did some fiberglass work I just grabbed a used vacuum pump from an appliance repair shop. Think it was from a GE fridge.
    I think I spent $15:00 on the setup including an aquarium valve to bleed a little air in so the pump wouldn't deadhead.
    Worked really well for laminating a ski eye in the boat and graphite arrow shafts in a GI M1A fiberglass stock to stiffen the forearm.
     
    #6
    LongRifles said:
    I want to stick "something" in a big bag and pull a vacuum on it so that it pulls down tight around it.
    Click to expand...

    Pumps are pretty easy to come by for this purpose. Do you only want to do this once? You could probably hook up the inlet to an old air compressor to the bag. You could even hook up the brake booster line from a car to the bag and use an idling engine to pull a vacuum. If you happen to have a chamber that can hold pressure (like an autoclave) you can put the bag inside the chamber, attach a hose to the outside and pressurize the chamber. This is the same as taking air out of the bag and letting atmospheric pressure compress the bag. Also, you probably want to put a strip of cloth or batting in the bag to let the air out, otherwise the bag may seal against itself near the hose. If it's an epoxy layup you may want some batting in strategic places to absorb extra epoxy that will be squeezed out. The sticky putty used to seal metal roofs can be used to seal the edges of the bag and around the hose attachment. If it needs to sit for a while you can hook up an air tank to the vacuum line to "hold vacuum" and you won't have to run the pump continuously. If the part is all convex you might be able to just stretch a balloon over it or wind rubber tubing around it to apply the pressure you need. Plenty of ways to rig it just to do it once, but for production there are some techniques and tools that help. There are probably a bunch of youtube videos of this too.
     
    Last edited:
    #7
    Pos-T-Vac has what your looking for Chad. Looks like it even has a discreet carrying case
     

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    #10
    Old A/C evac and recharge machines have pumps that run on 110v with gauges and pressure switches to monitor and hold a set vacuum. Older machines can be had fairly cheep usually once the scale that monitors the charge weight goes its too costly to fix.
     
    #11
    LongRifles said:
    Short of a 5 stage dry sump pump, I don't know chit about these things.

    I want to stick "something" in a big bag and pull a vacuum on it so that it pulls down tight around it.

    Anyone familiar with this sort of stuff? I need edumacating on it.

    Thanks.

    C.
    Click to expand...

    I know about vacuum pumps. Are there specific things you would like to know?
     
    #15
    I just use a 2 CFM pump from Harbor Freight. its been pumping away for a few years now. considering its also used out at our little Goat dairy, its done well. For mold making I have an old propane tank hooked up in a T line to the pump with a couple valves, one to the part the other to the tank.

    basic instructions (ignore if you already know this)
    with the tank valve open and part valve closed,you draw a vacuum on the tank.
    when the tank is at full vacuum you close off the tank
    when your ready to work, open the tank valve and the part valve.
    the tank will pull most of the air out in short order.
    close off the tank valve and let the pump do the rest.

    Of course I built this system for thermoforming Poly-carbonate and ABS it can easily be used for fiber applications as well.
    The obvious downside to this since it's only a 2 cfm pump is that we are needing a tank to help reduce the atmosphere at a fast rate when working. The initial setup will take much longer, but if you are not doing this kind of work on a regular basis and you plan out your project accordingly, you can stay busy while the tank is charging, while also saving yourself some cash that could be invested elsewhere.
     
    Last edited:
    #17
    Heres the app:

    Kalli is applying stencils to stocks for paint. Stencils dont adhere well until you put a touch of heat to them. Too much and they curl up on the edges.

    Fail to heat them and theyll lift at the edge causing "ghosting" when color is applied.

    So, my thought is to slip a freshly stenciled stock into a bag, pull a vacuum on it, and run a low temp heat gun over the stock to get the stencils sucked down nice and tight against the surface. Then release and get on with shooting paint.

    It should work me thinks.
     
    #20
    I think you'll find that trying to put a stock in a bag with slightly curled stencils will drive you nuts. Invariably a tip of a stencil WILL catch on the bag and get ripped off. If you do manage to get it in there without screwing up a stencil then you have to worry about them seating flush as the bag collapses under vacuum. This won't be easy.

    Perhaps a better approach is to warm the stock and stencils before actually applying them. This way gets (and keeps) the adhesive softened to the point that it does what it is supposed to do. A small light table would work for the stencils and a heat gun for the stock. No need to get fancy.
     
    #21
    If you don't mind the pump having oil in it, get a Robinair Model 15600. There are some new ones on ebay for $298.00 and free shipping. That is a good price.

    If you don't want oil in it, look at something like a Thomas Model 2680CE44.

    Those air operated pumps are awful but if you would like to try your idea before you buy anything, I'll send you a new one of them to try for free.
     
    Last edited:
    #23
    Edds said:
    If you don't mind the pump having oil in it, get a Robinair Model 15600. There are some new ones on ebay for $298.00 and free shipping. That is a good price.

    If you don't want oil in it, look at something like a Thomas Model 2680CE44.

    Those air operated pumps are awful but if you would like to try your idea before you buy anything, I'll send you a new one of them to try for free.
    Click to expand...


    Generous offer.
     
    #25
    Edds said:
    If you don't mind the pump having oil in it, get a Robinair Model 15600. There are some new ones on ebay for $298.00 and free shipping. That is a good price.

    If you don't want oil in it, look at something like a Thomas Model 2680CE44.

    Those air operated pumps are awful but if you would like to try your idea before you buy anything, I'll send you a new one of them to try for free.
    Click to expand...

    I agree the air operated vac setup wouldn't be for an everyday setup, I figured they are a better option to try to see if it worked rather than spending $3-400 on a good electric vac pump to find out it's not going to work as planned.
     
    #26
    A lot of general purpose vac pumps have been made from the compressors scavenged from old refrigerators and AC units. It doesnt sound like you need anything to specialized. That said, a Gast brand piston style vac pump would be perfect. It doesnt have internal oil, is relatively inexpensive and reliable. I have one and it works well. I use it sometimes to bleed brakes, evaporate solvents or de-gas stuff. Good luck.
     
    Last edited:
    #27
    Vacuum Pumps

    Try one of these. Old used ones can be found cheap at your local EMS office. The EMS services usually buy new ones when they get a new ambulance. As often as once a year. The old ones are hardly used. We used to have vaccum splints to immobilize fractures and these things would make them hard as a rock within seconds. They are battery powered and can be plugged into 110 to charge. You wouldn't need a canister unless you're pulling fluid. Put a clamp on the tubing to hold suction.
    http://portablesuctionmachines.com/
    I may know where a few are for free! ;)
     
    Last edited:
    #28
    I have used many kinds of vacuum pumps through the years. We use them for pulling deep vacuums on refrigerant circuits. Ritchie yellow jacket has a good quality vacuum that will hold up for years of harsh use. It may be overkill for your application, but it will probably last forever.
    You could also plumb in a tank to speed up the evacuation on your project. Just pull a deep vacuum on the tank, and let her rip when you are ready.
    Check with your local HVAC supply houses. Don't tell them you are not in the HVAC industry (they will try to price rape you). They will also have all the hoses and fittings to make the connections you need. PM me if you need any help getting it.
     
    #31
    LongRifles said:
    Short of a 5 stage dry sump pump, I don't know chit about these things.

    I want to stick "something" in a big bag and pull a vacuum on it so that it pulls down tight around it.

    Anyone familiar with this sort of stuff? I need edumacating on it.

    Thanks.

    C.
    Click to expand...
    To what level of CFM/Hg do you want to attain.
     
    Last edited:
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