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  • #16
    Originally posted by plunger View Post
    I made a kmg knife grinder . These wheels in darkest africa cost a bomb.How difficult would it be to cast or machine an aluminium wheel and bond some polyurethane on it.
    I am concerned as to how to bond the urethane to the wheel securely so it doesnt delaminate.
    Also how would one make those tyre grooves that run at an angle.How would one machine that.?
    https://guide.alibaba.com/shop/250-5...l_5830549.html
    I don't think it should be too difficult. If you have a lathe or a mill you can make the wheel itself. Castable urethane rubber is readily available, although maybe not in darkest Africa. Hard silicone rubber or even latex rubber might also work.

    I suspect my approach (depending on how long I thought the rubber would lasts) would be to make the wheel, cut grooves in the surface, place it in a mold and pour the rubber of my choosing. After curing I'd set the4 wheel back on the lathe and either grind or cut it to concentricity depending on what tools I had available. I think I would make the aluminum rim of the wheel thick enough to allow me to skim cut it if I had to recast the rubber again in the future. I would certainly make the rubber thick enough so I could true it up once or twice if I needed to.

    That being said, there are utility wheels for carts and other things dirt cheap. Some might even be wide enough for the application. Machine one for better bearings, and then true up the rubber surface and you could have a useable wheel in an hour or two.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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    • #17
      https://www.surpluscenter.com/Wheels...eel-1-4096.axd
      When I get Time... I'll...

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      • #18
        A company in the Chicago area made elevator guide rollers by casting PU onto aluminum hubs. don't know much about the process except he has a row of wall mount ovens for curing. The ovens were the type ypu buy at an appliance store. I don't know how the bond would hold at the speed you will run. I do have a wheel, if I remember correctly, it was about 6" OD and 2" wide. It has a PU tread about 1/4" thick. If you can figure out how to handle shipping you are welcome to it.

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        • #19
          Contact wheels are over-hyped. Just make a convex patten with the desired radius.

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          • #20
            Originally posted by MattiJ View Post
            Probably going to fly away when the 200mm wheel is running 6000rpm...
            12,000+ sfpm?

            Sent from my XT1585 using Tapatalk

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            • #21
              How does the PU do with the heat? IIRC, past threads say rubber is more resistant and PU can melt. Be a shame to put a lot of work into a nice PU wheel and have it melt.

              I was curious about MDF vs. good plywood for wheels. I see both get used, and I can think of reasons to choose either material.

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              • #22
                Originally posted by Glug View Post
                How does the PU do with the heat? IIRC, past threads say rubber is more resistant and PU can melt. Be a shame to put a lot of work into a nice PU wheel and have it melt.

                I was curious about MDF vs. good plywood for wheels. I see both get used, and I can think of reasons to choose either material.
                MDF is more consistent in density and doesnt have any voids, thats why i prefer it. Ive seen people use plywood for bandsaw wheels, and it always seems to take a lot of work to balance the wheels, never had that problem with MDF

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                • #23
                  Turning large diameter wheels is a job I’ve on the spindle of a Bridgeport with the lathe tool in a vise.

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                  • #24
                    I used a scrap polyurethane caster for a contact wheel on my grinder. Has an aluminum hub and is overmolded with the plastic. Mine did not have bearings in place so I bored each side with the mill and then trued up the OD on the lathe after the bearings were installed. Works a treat.

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                    • #25
                      I made mine with a simpler wheel from Surplus Centre. I think mine is 14” couldn’t swing It in the lathe made an arbor and cleaned it up on the drill mill. Works good.

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                      • #26
                        You can use mdf, but make sure you don't get the flakey stuff. Some of that wants to peel in layers, other types are pretty good at being strong in all directions. High density fiberboard would probably be a better choice. In any event, for a strong bearing seat you'd probably want to bore a section of steel pipe to insert through the stack of mdf discs to spread the load. Epoxy works well to bond the discs to the pipe section. If you chuck the pipe and bore to bearing size, then epoxy the discs over the pipe while it's still in the chuck, you can carry out pretty much all operations to true this up and bond an outer covering over it- which you then also true up- before the pipe needs to be removed from the chuck. Now you have concentricity, in terms of measurement and in terms of balance of each component of the structure. You can also bond a short piece of rolled steel sheet into the bore for a shoulder for the bearings to come up to. This insert could be another piece of pipe also, turned to fit the ID of the bore.

                        This is a fair amount of work, but could be a way to let you use existing materials. The epoxy might be harder to find. Some hardware type stores carry various construction type epoxies that are quite useful.

                        I've made many rollers using pvc pipe as the outer sleeve. Like everything else it has a temperature limit. It wears quite well, and can be turned easily which could be a boon if your setup is barely able to machine at the diameter required. If you start by finding a suitable sized piece of pvc pipe, you can dimension everything else to fit. You would cut the pvc to length, then bore it so you know how big to make the mdf discs. When the final assembly comes, the bored pvc will better fit over the machined mdf disc stack. I don't think there is any pipe which is true enough on the ID as is for a good fit.

                        Other options- if you can get decent epoxy in quantity at a decent price, like say a liter or more, or even a half liter, you could consider casting a home made mdf. Start with mdf sawdust and mix up an epoxy mud to cast into a mold. If the mold holds the bearing tube concentric with an outer sleeve, the mud can be packed into the gap to form the body of the roller structure.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #27
                          Originally posted by paul463 View Post
                          12,000+ sfpm?

                          Sent from my XT1585 using Tapatalk
                          Oops, make that more like 6000rpm and 100mm wheel or 3000rpm and 200mm wheel.

                          Still at risk that the inner tube would fly away instantly.
                          Someone could calculate this... Im too lazy at the moment.
                          Location: Helsinki, Finland, Europe

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                          • #28
                            I glued a piece of inner tube to a 5 inch aluminum billet wheel I made.Have run belt as fast as 8000 feet per minute.I used 3m weather strip adhesive.Once you have first layer on you can use tire tube cement for more layers if you what a softer wheel.You need a inner tube that stretches to go over your wheel. I think i used a motor cycle tube.

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