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tiofilo123
11-26-2010, 11:06 AM
New guy here, seeking help, and i don't know if im posting this in the right place. I'm trying to figure out if i can use a regular shop vac for my vacuume clap down or do i have to use a fein vac, my work area is small 2'X3'

JD_Mortal
11-26-2010, 01:52 PM
It is possible to use a shop vac... However... Most shop vacs are not made for long operation. None are made for constant vacuum suction. (Loaded suction.)

You can extend the life of your shop-vac, while using it this way, with a few things...

1: Reduce the canister volume. This gives better suction, for the following tip.

2: Add a manual controlled pressure release valve. Having a high volume of fresh cool air through the vac is required for operation. The shop-vacs use the flowing air to cool the motor. Keep this valve inlet close to the motor, near the filter inside the canister. This stops it from interfering with the vacuum pressure by your work surface.

3: Cut a few kids-foam strips to cover unused holes in your vac-surface. You find this at walmart, or craft stores. Plugging unused holes allows greater suction where it is needed, on the surface of your hold-down item, and at the pressure release valve, for cooling.

If you do not do #1, you will not have enough suction to hold down your item well, once you add a pressure release valve.

"Central vacs", like the kinds used for homes, have external motors and cooling. They do not depend on flow, as much, but still depend on flow of some kind. (They usually have a bypass valve built-in, in the event that the vac is left-on, while sucked to a floor.)

Actual vac-hold units have external cooling, better holding power, are designed for constant loaded operation, and may have options for liquid cooling the motor. At 10x the cost of the alternatives above. (You could easily go through 10 shop vacs, and have 10 new vacs each time... or be stuck with the same vac-hold, for 10-20 years... No chance for upgrades.)

tiofilo123
11-26-2010, 03:25 PM
thank you jd,
any brand you recomend, or do you think i can get away with using a couple of old hoovers from the flea market

JD_Mortal
11-27-2010, 12:43 AM
It is less about the brand, and more about the power. Since you will not be using this traditionally, as a vacuum cleaner... The accessories and function are even less important.

Things to look for...

1.5 HP, 6 Amp (Shop vac) Should hold most semi-smooth surfaces ok.
or
2.5 HP, 12 Amp (Upright) Will easily hold porus balsa securely.
or
4.0 HP, 20 Amp (Canister) Would hold a porch-screen securely in place.

Metal motor housing, if possible. That is a possible sign that it is designed for long-term use, operating in a commercial or industrial environment. (Such as a rainbow, or hoover bag model.)

Plastic is still fine, but expect a shorter life. Plastic insulates, dry-rots, becomes brittle, usually has non-repairable parts, and is made for intermittent consumer use. (Like vacuuming three rooms, or one car interior, or pickup of a shop monthly.)

The lower amp models will keep your electric bill down. Obviously, the 12 amp models will consume twice as much power, but not yield twice as much power. They will also pop circuit breakers twice as fast, under load. Match the cord and outlet to the max power of the vac, as it will be nearly at maximum power consumption the whole time. (Sound is your best determination for detecting motor stress, besides exhaust heat from the motor.)

Also note, many uprights have metal tubing with a pressure release slide-valve near the handle. You can rip-off that cheap plastic slide, and attach a real ball-valve to that hole.

If you need stronger gripping-force, you can also use a full sheet of soft-vinyl with holes that match your vac-table holes. The soft-vinyl that feels like rubber, not the slippery shower-curtain stuff. Use it between your vac-table and the item you are holding.

You can also make a foot-valve, for quick-release, if you need to adjust or rotate the item on the table. (A similar ball-valve, with a spring-close, hooked up to a foot pedal. Stepping on it opens the valve, releasing the pressure without turning off the vacuum. You will not have to wait as long for the pressure to resume full gripping power. That also allows you to release pressure in the event of accidental air blockage while setting up the table. Remember, you still need constant air-flow of some kind.)

ger21
11-27-2010, 06:57 AM
You can buy the motor only and possibly get a lot more power for your money.
ShopBot Vacuum Motors (http://www.centralvacuummotor.com/shopbot.htm)

CarbonKevin
11-28-2010, 10:17 PM
1: Reduce the canister volume. This gives better suction, for the following tip.

Can you explain this further to me, please? It seems completely contrary to the notion of vacuum cleaners losing suction as they become full...

ger21
11-28-2010, 10:31 PM
Can you explain this further to me, please? It seems completely contrary to the notion of vacuum cleaners losing suction as they become full...

If a vacuum loses suction as it gets full, it's because the airflow is being restricted, not necessarily because it's full. The outlet size is decreasing.

JD_Mortal
11-29-2010, 08:03 AM
Yes, he is correct... it is not "full" as in, full of blocking dirt...

Full is a loose term, improperly used when talking about a vacuum cleaner. People say it is full, when it is clogged, having nothing to do with fullness, though, being full of dirt could lead to clogging. (A vacuum can be full of dirt and still have full suction, and not be clogged. Often, that is what happens with most vacuum cleaners. We empty them when they are full and clogged.)

However, since you will not be vacuuming with this, you will rarely ever see it full or clogged. Perhaps some dust will be sucked-in while you work, but not enough to impede operation of the suction.

When you reduce the volume of the canister and use more solid/rigid lines, you increase pressure. Line-flexing and large volumes of air act as an undesired "buffer", which causes irregular pulses of vacuum pressure. (This condition is also alleviated by having a constant slow leak, by the pressure control valve I talked about in the prior posts.) As the vacuum pressure increases, the air is being removed, and the blower-fan spins quickly since it has no real pressure, causing more of a vacuum. This results in a "pulse" as the super-vacuum now draws in air, back through the exhaust and the soft flexible bucket and line become rigid. Thus, reducing pressure, slowing down the blower, and causing another pulse as the vacuum returns to full negative again...

When you reduce the volume of air, and use rigid lines, and stiffen the canister... You create an ideal and steady vacuum. Not as steady as a piston-vacuum, but as steady as a blower-fan can produce, for static load. The advantage of using a blower, over a piston-vac, is reduced voltage-load and heat while operating. You also gain the ability to retain a greater steady pressure, without complex valves and buffer-tanks, and without as much wasted power.

Sorry, I tend to over-explain everything.