| Vacuum Pumps #174357 04/09/09 07:09 AM 04/09/09 07:09 AM |
Joined: Jun 2001 Posts: 115 Kevin Cook OP
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Posts: 115 | The vacuum pumps that home builders use show an amazing variety and range of capability. Everything from aquarium pumps to vacuum cleaners. A professional outfit at retail prices can easily cost $1000 US. That’s a steep price to pay for an amateur builder. So somewhere between a $1000 pump and your home vacuum cleaner there must be a rig to get the job done without bankrupting the builder. The two important things are that a pump be reliable (if it quits during the cure you are screwed) and it has to have enough capacity to tolerate minor leaks in the bag or mold. Theoretically, if a bag is totally sealed, a very small pump is all you would need. Real life is very different. Even if you do a complete dress rehearsal with the bag and pump before committing to wetting out the reinforcements, and the bag proves to be tight, there are still things that happen during the actual lay up. For instance, a drop of wet resin where the bag seals to the mold will prevent the sealant tape from sticking and will cause a leak. There may be a minor leak in the pleats and folds of the bag that is nearly impossible to find. For these reasons, some significant pump capacity is needed – the more the better. I’m sure there are a lot of opinions on this but to vacuum bag something the size of a Tornado hull side; I would recommend a pump of a least 4 cubic feet of air per minute. This equates to around 1/3 horse power which is a little bit more than the average HYVAC air conditioning service pump. There are oil filled pumps that can develop more vacuum than dry rotary vane pumps but they are messy and require a lot of maintenance. I have acquired several pumps over the years, a couple of Gast 1/3 horsepower rotary vane units, a one horse power (14 cubic feet per minute) Gast vane pump, and a two horse power oil filled vane pump (16 cubic feet per minute). Although most pumps can produce 27 to 29 inches of vacuum, 20 inches will produce good quality parts. If you can’t get above 15, the quality of the part will definitely start to suffer. Finally, this brings us to the issue where to buy a pump. I swear by Ebay. If you search under ‘vacuum pump’ there will be a hundred or more hits. The 1/3 horse power Gast units are common in computer rooms and machine shops. A unit in excellent condition can be had for around $100. They retail for around $400. My 14 cubic foot pump cost $180 on Ebay and was brand new surplus. Retails for about $800. So, the deals are out there if you look around a little.
| | | Re: Vacuum Pumps
[Re: TheManShed]
#174459 04/10/09 07:58 PM 04/10/09 07:58 PM |
Joined: Aug 2007 Posts: 190 lesburn1
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Posts: 190 | When I set up my vacuum pump (home made) I also bought a vacuum generator as well as a backup. In case your main pump fails you should have a backup "plumbed" and ready. http://www.vacmotionorders.com/vcv10hs-basic-venturi-vacuum-generat.htmlWhile I have never had a problem, it's nice to know that I have a spare in the shop. When I first started looking for my main pump last year I went to a dairy farmer friend that was just in the process of selling their farm. I asked if they wanted to sell one of the pumps they use to milk the cows ( a roots vane type) but another farmer had taken them earlier in the week
lesburn1.blogspot.com
A-Cat USA 49 18Sq 49
member- Royal Society for Making Cool Stuff
| | | Re: Vacuum Pumps
[Re: Kevin Cook]
#174465 04/10/09 08:37 PM 04/10/09 08:37 PM |
Joined: Aug 2007 Posts: 190 lesburn1
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Posts: 190 | I'll have to say I don't feel the pressure. The epoxy I use will sit in the pot or roller tray (10 oz. at a time) for one hour before I start to worry about it. It takes me about 90 minutes of "wet work" to layup a side of an A Cat hull. Most of my time is spent in the prep. work. And checking the bag before I turn up the heat. Once every thing is good it goes to 130/140 and six hours later I turn every thing off and walk away for 36 hour, then pop out the part. I used to use West Systems and always had to change rollers and brushes and mixing pots because the resin would start to pop off to quickly. But back then Gougeon only had two flavors "fast" or "slow".
lesburn1.blogspot.com
A-Cat USA 49 18Sq 49
member- Royal Society for Making Cool Stuff
| | | Re: Vacuum Pumps
[Re: Kevin Cook]
#174488 04/11/09 12:14 PM 04/11/09 12:14 PM |
Joined: Aug 2007 Posts: 190 lesburn1
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Posts: 190 | Since I am using a mold there is probably not a lot of crossover. If he does use the "band of epoxy where the seal tape" (another thread) he should cover everything from that band outward with blue painters tape. I put down my "tacky tape" and then cover it as well as most of the flange before I start the wet work. Then after everything is in the mold (glass, core, peel ply, release film, and breather) I pull up the blue tape and every thing is "dry" and clean.
lesburn1.blogspot.com
A-Cat USA 49 18Sq 49
member- Royal Society for Making Cool Stuff
| | | Re: Vacuum Pumps
[Re: Kevin Cook]
#174500 04/11/09 04:25 PM 04/11/09 04:25 PM |
Joined: Jun 2005 Posts: 133 The Netherlands Kennethsf
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Posts: 133 The Netherlands | do some of you use an vacuum resevoir? [reverse of an compressor tank]
this guy did it [btw used an old fridge compressor]
see link [use bablefish translator or something- org. text is in dutch]
http://www.xs4all.nl/~ebb/kiteboard/html/handleiding/hl_24bou.html?page=eee
Last edited by Kennethsf; 04/11/09 04:32 PM.
| | | Re: Vacuum Pumps
[Re: Kennethsf]
#174502 04/11/09 05:22 PM 04/11/09 05:22 PM |
Joined: Aug 2007 Posts: 190 lesburn1
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Posts: 190 | Yes, my pump has a four gallon reservoir and then across the shed from where the compressor and vacuum pump are I have a six foot section of sched. 40 pipe setup as a reservoir and it has three connectors on it. One fore a vacuum gage, and the other two connect to vacuum line to go to my bag.
lesburn1.blogspot.com
A-Cat USA 49 18Sq 49
member- Royal Society for Making Cool Stuff
| | | Re: Vacuum Pumps
[Re: Rolf_Nilsen]
#175415 04/20/09 02:14 PM 04/20/09 02:14 PM |
Joined: Nov 2005 Posts: 1,203 uk TEAMVMG
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Posts: 1,203 uk | Looks like a bit of pvc pipe that is connected to your WC [Wash it 1st] and a pair of end caps.
Paul
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