Which shop vac for table?


SeventhSense

New Hunter
Hey I'm about to build my first vacuform table and have some questions about the shop vac:

1. What horsepower does it have to be?

2. Does gallon size matter at all?

3. Does the hose size matter at all?

I was thinking about getting this one http://cgi.ebay.com/BRAND-NEW-5-GALLON-HANG-UP-SHOP-VAC-W-ATTACHMENTS_W0QQitemZ160049856800QQihZ006QQcategoryZ20615QQrdZ1QQcmdZViewItem
If anyone could help me out I would really appreciate it as I want to order one off ebay ASAP. Thank You!:)

Edit: Don't know if it matters but I will be using the design off of http://www.halloweenfear.com/vacuumformintro.html unless I find a better/cheaper one in the meantime.
 
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KaanE

Well-Known Hunter
On this web The VACUUM TABLE

All the information for the VacuumTable;)

figura25.jpg
 

drcrash

Hunter
Shop vacs aren't all they're cracked up to be. These days a lot of regular home vacs or even hand vacs suck as hard as shop vacs. Shop vacs can suck a lot of air in a hurry, but they don't really suck harder than a good canister vacuum. They're also big and bulky.

The gallons don't matter; if anything, smaller is better; the vac sucks air through the big bucket, so the bucket just holds more air to suck out. (Probably true for hoses, too. A 1 1/4" hose is sufficient for at least a 2 x 2 foot table, and the 2 1/2" hose just holds unnecessary air. It probably doesn't matter much, but the big hoses tend to be awkward.)

If you have a shop vac sitting around anyway, by all means use it. But if you're buying a vac, I'd recommend going to thrift stores and getting the one that sucks hardest for a lot less money.

One way to see which sucks hardest is to put a piece of craft foam over the end of the hose, and see how far into the hose opening it dimples. Whichever vac pulls it furthest in, buy that.

For my small (12" x 18") platen, I use a Euro Shark Ultra Big hand vacuum, which is actually quite small. It is about a tenth the size of my shop vac and actually sucks a little bit harder. I'm not sure it sucks enough cubic feet per minute for a big platen, but it's plenty for the small one. It cost me something like three dollars.

There are no good specs on vacuum cleaners. What you mainly want to know is how hard a vacuum they can pull, not how many cubic feet of air they can move.

Horsepower isn't a reliable indicator of how hard a vac can pull, but on average more is better. How hard it actually pulls depends on the impeller design, and whether it's designed to move a whole lot of air against low resistance, or less air against a higher resistance. (Basically a torque-like "gear ratio" tradeoff.)

I wouldn't look at horsepower, particularly. I'd look for amps or watts. (At a given voltage, like regular wall outlet voltage, amps and watts are perfectly correlated.) That will let you compare across shop vacs and regular vacs.

I got my little hand vac because it's got an 8-amp (1000 watt) motor in it. (Most old hand vacs are only 2-amp; newer Dirt Devils are mostly 6.5. Unfortunately Shark doesn't seem to make 1000-watters anymore; they top out at 700.) Once I got a vacuum gauge, that turned out to be a good call. The little sucker really sucks.

Another possibility is an electric leaf-blower type "blower vac." That's a lot like shop vacs without the big worse-than-useless bucket.

But if you really want a shop vac, I have one to sell, which I bought before I realized these things. Hardly used it at all...
 

drcrash

Hunter

drcrash

Hunter
Another good resource is Douglas Walsh's book "Do It Yourself Vacuum Forming for the Hobbyist." Inexpensive, and chock full of info on homebrew vacuum formers and vacuum forming techniques. Most of the info is available for free somewhere on the web, but it's an inexpensive book and full of good stuff.
 

asok

Well-Known Hunter
I am going to look into making on that you don't flip it. But, heating element is on the top and you just bring the material stright down. I just need to find a heat source.
 

drcrash

Hunter
I am going to look into making on that you don't flip it. But, heating element is on the top and you just bring the material stright down. I just need to find a heat source.

Then you definitely should check out the discussion board on tk560.com. Several of us have done exactly that, and there are things you need to know about oven design, etc.
 
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