HoverPad anyone?

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wrote:

The air pressure that is needed depends on how large the pads are, how heavy the load is, and how smooth the floor is. The floor smoothness and the condition of the pad skirt's bottom surface significantly affects the volume of air that is needed. Of course, some air has to leak out to provide the air bearing function, but the less air escaping from under the pads, the less dust will be blown around. I always sweep my floor before using them, but I don't make it perfectly clean. Sometimes I'll see some dust being blown around on the floor but I never get major dust clouds in the room from them. I guess it really all depends on how good the skirt to floor seal is. They used a vacuum cleaner to inflate the cheaply made pads in the link, which is high air volume and very little pressure, probably only a few psi. I use my shop compressed air system, a 3/8 line to supply line my regulator bank and 1/4 inch lines from the regulators to each pad. My air system has an 80 gal tank and 18 cfm compressor and I've never run out of enough air to run them, but if I was to run a pad over an 1/8 inch crack in the floor, the pad would collapse. I can sometimes crank up the pressure (and thus the volume) to a collapsed pad to get over small defects, but it's best to make sure that the floor doesn't have any significant voids in it where you are going to be using the pads. We used bondo and duct tape as a temporary floor fix to get the pads to work over some bad spots in the floor when I was using the commercial pads to move the robots, but rough floors can be a major problem. Floor defects can easily damage the rubber skirt seals on the pads as well as pose the significant air leak problems. To lift an 800 lb table saw with 3 - 8 inch diameter pads on a tile floor you probably will only need about 2 or 3 psi. I rarely move my tools with my pads any more as my present shop is relatively small and tool locations are stable. Lately, they seem to just get used for moving big clumsy projects where it is very inconvenient to try to move them around with dollys, etc. or sometimes when I'm the only one in the shop and I want to move something myself. Once the pads are in place under a project I usually leave them there until the project is finished, so it can be moved or turned around for the convenience of getting to the other side, etc.
I didn't mention in the previous note that I have been adding a small circle of 1/2" plywood in the center of my pads to take the load off the rubber skirt material when the pads are not inflated. I found that this helps to protect the rubber should a side force (bump) be applied while the pads are deflated. They can easily tear if a load is on the rubber alone and the load is pushed sideways. With the plywood in the center the weight of the load is on it and not on the rubber.
Charley
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PCPaul wrote:

What risks? When the air's not on it's a piece of plywood sitting on the floor. When the air is on either it lifts or it doesn't. If it doesn't then you've wasted what, ten bucks? If it does, how high is it going to lift? 1/8 of an inch would be quite a lot.

Kill the air and down it goes. If it's going real fast _then_ it may tip.
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Actually, the answer is "No" it doesn't require an increased amount of pressure to stop it. When I was playing with it at the woodworking show with a sizable tablesaw on it, I was able to manoeuvre and stop or change directions quite easily. So much so, that my wheelchair was only slightly prone to rolling away when I was moving it around.
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wrote in message

Momentum is the word.
It's easy to get something moving when it's on an air bearing, but there is so little friction that it wants to keep moving at whatever speed you get it up to. Instead of the normal friction slowdown that we are accustomed to, you will need to supply very nearly the same force to stop it as you did getting it moving. We are so accustomed to friction slowing and stoping things that we move our bodies aren't really prepared to have to supply this much negative force to stop something once it's started moving. After a few minutes of pushing and pulling we quickly adjust to it, but the first experience with a relatively heavy object on an air bearing (like 1-2 tons) can be a bit of a surprise and an almost certain crash. I almost pushed a 3600 pound robot through a wall with my first experience. I got it stopped in time, but nearly got pinned in the process.
Charley
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Thanks. I've bookmarked that one too.
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Nice to see somebody engineer this out to an affordable level. The tech, as you know, is old hat. I seen those used when moving 100 ton presses. Here's a supplier:
http://www.hovair.com/products.htm
What I did not want to do, is rain on anybody's parade. But the blow- up dust is a huge issue, as mentioned in here already. The nice thing about the whole concept is that it easily done by the little guys on the cheap. I see guys move skids of granite cut-offs all the time. Whole sheets of granite moved on pucks, home-made from 3/4" UHMW, where air pressure is applied to move the piece, and then flipped over with a 3- way valve to vacuum to hold while machining. Their problem is water flying all over the place.
To make your own? I was thinking small inner tubes... wheel-barrow/ lawn-tractor style. Cut them along the external and internal circumference... maybe, if small enough, leave them whole and perforate them on one side? Insert them in a channel routed out of a slab (doubled) of MDF with a bowl bit and a circle cutter? Maybe a bicycle inner tube stretched into a rectangular slot with rounded corners? The inlet is already on the tube...even...
Come ON PEOPLE!! We're a smart bunch here. One groove for the tube, one groove outside that tubed perimeter for the shop vac? I want ideas on my desk by night fall. hehehehe
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Way cool, especially how it makes heavy objects levitate 1/2" above the floor. I wonder if a sheet of plywood with a hole in the middle wouldn't do just as well.
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Can't answer that. The time and effort I'd need running around to get the parts and assemble one to my satisfaction would be put to better use my just doing my job the equivalent amount of hours and buying the General version. Guess which one I'd choose?
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1/2 sheet 1/2" plywood, 1 2" cutoff 3/8" pipe, hose, clamp, epoxy, 30 seconds labor to drill the hole in the center of the sheet.
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wrote in message

If you look closely at the General hoverpad you will find that it's really many small hoverpads on a big sheet. Making one big one will give you stability problems. Multiple small ones like 3 or maybe 4 on one common sheet will give you the stability of the General's version.
Charley
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How hard would it be to glue up a manifold from 1/2" PVC?
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wrote in message

Actually, my pads have a sort of manifold made into them. I groove one sheet of 3/4 ply and then sandwich/glue it on top of another piece to allow me to have the air inlet enter along the middle of one edge. I epoxy any voids in the plywood groove and also epoxy a quick connect air line fitting into the hole (bored out to fit) in the edge. It's positioned so that nothing interferes with the flat top surface. That way the pad will fit under anything. To be sure of a good glue-up of the two sheet joint and have no leakage I make sure that I run an unbroken bead of glue all the way around the groove area so that it seals real well when put together. Then I hold the sheets together with clamps followed by screws "until the glue dries". Of course, the screws remain when the clamps are removed. If you were making several small pads on a large sheet, manifolding between them this way may not be such a good idea. Maybe you could sandwich a piece of pipe in the groove to minimize the possibility of leakage.
I have never made a multi pad assembly. All my pads have been single and each one has had it's own air line from it's own regulator, so I can feed each one and control it separately. I don't know how they would respond if they were all manifolded together.
Charley
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Depends what supplies you have on hand, I guess. I do plumbing, so I have lots of spare 1/2" PVC pipe and fittings laying around the shop.
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That's the difference then. For some things I like to build them from scratch like setting up and organizing a workshop, but other things I like them to just be there for use. The HoverPad would fall into that category as far as I'm concerned. I'd just want to use it and not worry about saving a few dollars building one. It's unlikely I'd be saving any time, so building one from scratch is just not a consideration.
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