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  • Plastics Question

    I have a shop cart on which I move heavy items around the shop. I'm guessing but I think it is about 50 or more years old. The problem I having is that the plastic tread is flaking off the wheels when ever it is rolled which makes for rough handling and bumpy ride. The plastic tread has come completely off the hard plastic hub which has very nice roller bearing in it. I'd like to put the cart back into service but have some questions. Since the hubs, pictured below with the bearing and tread removed are completely serviceable, I'd like to put a new tread on each of them. I have found Impact-Resistant Ultra High Molecular Weight Polyethylene Tube which I'd like to use for the tread. The cost to replace the wheels in each caster is about $60 each while a foot length of UHMW tube with 4" OD and 3" ID is only $40.

    The question I have is about how stretchable is the UHMW material. The diameter of the hub at both outside edges is 3.340" while at the center, the hub diameter is 3.395". If I machined the inside diameter of the tube to 3.340" and pressed it on to the hub, would the UHMW stretch enough to go over the larger diameter at the center or split? Would I have to make the inside tube diameter larger to get the new tread to fit over the center hump of the hub? Once I get the treads on the hubs, should I use heat to seal the tread edges to hubs?

    Appreciate assistance. Thanks.



    Bill

    Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

    Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

  • #2
    By no stretch of the imagination am I a plastics expert, but why not chuck up the wheel and machine it to ....say 3.200 or so and then bore the new tire for a few thou. press fit. Boil the new tire in a pot of water and then press it home? That way You end up with a thicker tire and eliminate the crown problem.

    Steve

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    • #3
      Harbor Freight sells swivel castors in various sizes and medium to heavy duty most for less than fifteen dollars each. Throw in a 20 or 25 percent coupon and I have to ask, Do you really want to fix what you have? Even if you just take the wheels off a set of theirs it would save you a good bit of work. I have bought a few sets there and they have worked great. Mike

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      • #4
        +1 even if don't like HF .. 40 - 60 per caster is really a lot. You can get beautiful casters on
        ebay for a fraction of that.

        Then .. of course if you are like many on here, that are just looking for a project, then go for it.
        John Titor, when are you.

        Comment


        • #5
          First, I agree with Mike279 about getting a new set of wheels, search ebay and you can come up with some good deals on casters.

          Second, if you really want to repair them, I agree with doctor demo, chuck up the old hub and machine the crown out of it. Trying to get the material to sit right on that is asking for trouble.

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          • #6
            Here is 2 link from a quick ebay search.
            http://www.ebay.com/itm/Set-4-Swivel...item27c8c8b30f

            And if you want a heavier set than the first link.
            http://www.ebay.com/itm/Set-4-Swivel...item27c8c8b30f

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            • #7
              UHMWPE isn't a great choice because of its creep characteristics, which theoretically will cause the tyres to stretch and loosen. It's a great material, but I think you'll find it's not used for similar purposes for exactly that reason.
              Elastomeric polyurethane or rubber would usually be the first choice, though I realize that would be difficult. It may be possible to find natural or synthetic rubber tube close to the right diameter. Otherwise, consider glue and rivet either a section of hose or belt.

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              • #8
                I guess I was looking in the wrong place (McMaster-Carr) for replacement castors. Thanks for the tips. I guess I'm from the "old school" where you fixed broke things and didn't buy new items but at $25 for a set of four castors, that is cheaper than I can buy the replacement treads!

                Thanks for the help.
                Bill

                Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

                Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

                Comment

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