Jumbo Vacuum Cleaner Wanted

I need a hefty vacuum cleaner to build a vac forming table. In the USA theyre referred to as shopvacs, which I assume just means heavy duty. About 4Kw should do the trick. Im hardly expecting to find one for sale in this group but does anyone know who makes these things so I know what to look for? A Vax is nowhere near big enough.
Evacuated
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On Thu, 25 Nov 2004 12:36:16 +0000, snipped-for-privacy@aol.com strung together this:

<http://www.elektrabeckum.co.uk/eb/uk/en/produkte/dustcollectors/dustcollectorspa2000d_0130020011.html
Or;
Numatic NTT2003 on <http://www.numatic.co.uk , look out, it's another one of those crappy frame affairs.
Or are we looking proper industrial sized, not for home use.
--

SJW
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snipped-for-privacy@aol.com wrote:

Generally, it's just an industrial vac.

'4Kw' may be misleading. All electrical appliances in the US tend to be wildly optimistically rated. A typical practice is to measure the instantaneous startup current, and then multiply by the line voltage. This means that you get ridiculous numbers like '5Hp' compressors that run from a plug that won't handle more than 1.5Kw.
Why do you think that a Vax is nowhere near big enough?
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I beleived a Vax only rate at about 1.5Kw? All the sources I've tried so far recommend about 4Kw. If I become convinced a Vax wlll be enough could hire before I buy,
Evacuated
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snipped-for-privacy@aol.com wrote:

    Do you think that a vacuum cleaner will take the pressure low enough. IME, vacuum formers tend to use vacuum pumps, and go down to a few cm of pressure. How big a table do you want? How are you heating the plastic, which types of plastic are you planning to use, etc?
    Regards     Capitol
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wrote:

I'd have thought any vacuum would suck things to shape if the material was soft enough and the end of the hose was properly sealed. But something like these:
http://www.bocedwards.com/vacuum/dry_pumps/01001_A72401906_overview.html
would do a great job of making anything pop into shape in the correct former/mould.
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I wonder how your common-or-garden vacuum cleaner motor would regard being connected in series with a few others with intercoolers in line, to increase pressure difference.
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There are many sites and advice on the web from people forming with industrial vacs. My platen is about 2 feet sqr and qtr inch deep air space, i.e. about 2.5 litres volume. I've built a grill to heat the plastic and it's 0.75mm HIPS. That side of the setup is fine, it's getting the air out according to my vacuum guage readings Evacuated
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snipped-for-privacy@aol.com wrote:

If it's getting the air out, what's the problem?
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Frequently, the mould is on a plate which is moved up to push the mould through the plastic on small vacuum formers. The mould plate is mounted above a tank of the same area, but about >3x the depth of the plate movement, which has previously been evacuated to low pressure, <.05bar. The action of moving up the plate, allows the evacuated tank to equalise with the base of the mould which has vent holes inserted to aid airflow into the vacuum. This action provides about a +0.25 bar vacuum. I think this is rather more than the average shop vac. Many shop vacs use two bypass motors(no cooling problems) to give better "suck", but as these are a fan action, the suck will disappear if the airflow is blocked. (AIUI All fans only operate by sucking, so if you block the airflow you've had it!) If you wish to find out how well units suck, you need to do a search using " wet & dry vacuum water lift" The norm is in the region AFAICS of 7' which is roughly +0.8bar. If you are simply heating the plastic and then sucking down at the same time, the temperature control is very, very critical, too low and the material splits/doesn't form properly, too high and you get holes everywhere! The process is also dependent on the prior history of the plastic, who made it etc and a lot of suck it and see is required.
    Good luck
    Capitol
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Thanks everyone. The problem is the vacuum gauge is only showing about 6 inches mercury, so the table may be leaking. My delay in replying is because I've decided to use a tank between the pump and table, i.e. empty the tank, release a valve and woosh (hopefully) as air leaves the table. My tank (OK my pressure cooker) now shows 16 inches mercury which is the best I've got so far. Cannot get a release valve til Monday but does half an atmosphere seem sufficient? Has anyone a better idea for a home made vacuum tank? Evacuated
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" snipped-for-privacy@aol.com" snipped-for-privacy@aol.com says...

A propane bottle would give you more capacity, and a valve already fitted.
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Thanks everyone. With a new seal my pressure cooker is showing 0.63 bar. Assuming I get the plastic heated right AND find where my table is leaking does 0.63 seem enough? The tank volume is 4 litres. I've aquired a table that has a cunning sandwich. Between the two layers of ply is a layer of fine metal mesh slightly angled to lift the ply apart by 1-2 mm. This makes about 120 cc volume, Evacuated
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Thanks everyone sorry to be so long but its not through disinterest but through labouring over all possibilities. Thanks Rob re propane tank, I found one by the kerb as you do, 15 to a welder and Ive 44 litres of tank emptied to 18 inches mercury. This sucks my vacuum form down fine but there is one spot for improvement. The plastic is held in a frame over a 18 inch sqr grill. Frame gets hot and is pushed down onto the vacuum table but the frame to table seal is not great. Have any vacformers out there a good seal idea - rubber oven door sealant? It has to take the heat and be fairly air tight Evacuated
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On Thu, 25 Nov 2004 12:36:16 +0000, snipped-for-privacy@aol.com wrote:

If it's like the one the guy used to make his STormtrooper suit then I'd have thought a Henry would be just the job or his older brother perhaps? ;-)
"Shop" to me means something that's built to use rather than built to look pretty in the living room.
Mark S.
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wrote:

Isn't there a problem is the air flow is "stalled"? I believe that the current drawn can rise and the cooling air is diminished. The universal motor has its speed limited by the air resistance I believe. Change this by restricting a flow and the speed might rise.
--


Regards

John
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snipped-for-privacy@aol.com wrote:

Axminster do one with a couple of 1kW motors in sequence... might be enough, failing that a pair of them.
--
Cheers,

John.

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Hi All
On the subject of vacuum cleaners, you have to be a little careful. I'd forget anything domestic for a start, they won't take the strain for long. Look at Numatic or Nilfisk.
There are two types of motor used in commercial vacuums. Vacs designed for dry use have Direct Cooled motors - that is, the air they suck passes over the armature etc to cool it down. Stop the airflow for any length of time and the motor will overheat - no good for vacuum tables.
Vacs designed for wet or wet/dry use have By Pass motors. The air they suck is diverted sideways away from the amrature (wet air on electrics not being a good idea) and they have a separate fan on the back for cooling purposes. They will continue to operate without any airflow, so won't burn out on a vacuum table.
By pass motors come in two types - peripheral discharge and tangencial discharge. By discharge I mean how the air leaves the motor. Peripheral discharge have slots around the casing, tangential have a tube.
Two tangential by pass motors can be connected in series (inlet of one connected to out let of the other) to increase vacuum. Most twin vac carpet extraction machines work like this.
Connecting in parrallel, as in most twin motor vacs only increases airflow, suction remains the same.
Hope that helps
Dave
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