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  • O ring drive belt.

    I have made an high speed cartrige spindle and wish to use an O ring drive belt to drive.

    Something like 5:1 speed increase is the plan so the pulley at the spindle would be 40mm diameter and the drive pulley 200mm.

    So the motor would run at 2800rpm and the spindle 14000rpm.(maximum)

    I see these belts used on pantographs and tool grinders like THIS ONE but am having trouble finding specs of this belting to calculate if it will work.

    Will be used for 3mm carbide slot drills and I'd estimate 1/4 hp would be a max load at the belt.

    Any experience or advice?

    Thank you
    "...do you not think you have enough machines?"

  • #2
    Iu have a little watchmakers lathe and wanted to drill 0.020" holes in jets, had a Viton ring as a belt, it got hot, i toched it some time after and burnt my fingertips with the acid that came out of it!, changed to Neoprene!
    [it still works]
    mark

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    • #3
      Any help?

      Any help?

      http://www.google.com.au/search?hl=e...&oq=round+belt

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      • #4
        mc master Carr . Urethane belting . Its round comes 1/8 ,3/16 and larger diameter . it is orange in color. You buy by the foot and put it to gether your self by melting the ends. Works real good and does not slip.
        Every Mans Work Is A Portrait of Him Self
        http://sites.google.com/site/machinistsite/TWO-BUDDIES
        http://s178.photobucket.com/user/lan...?sort=3&page=1

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        • #5
          Hmm. A 40mm diameter pulley at 14,000 rpm- that belt is going to stretch and swing wide. I see that on my tp grinder with neoprene o-ring, and it doesn't spin that fast. The driven pulley on that is about 30mm dia at the bottom of the groove.

          Some kind of corded belt might be a better choice- just my opinion. You also have torque to consider- how much slippage is there going to be under load- belt will get hot, power will be wasted, pulleys will get hot and transfer that heat to the spindle-

          I would personally try to use a flat belt like a power head on a vacuum cleaner uses. It can still be a non-corded one, or you could make your own corded belt like I have done. It's not that hard, and is an interesting project. I've done that in dacron and in polyester, using tool handle coating called Plasti Dip. You'd need a tp grinder to surface the layups.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #6
            I am using a 1/4" o-ring with a 1/2 hp brushless motor on my mill right now. Maximum is 3000 rpm on the drive motor. The fact that the small pulley will be turning at high rpm isn't going to make the belt go wide Darryl, especially on a small pully. I use o-ring drive up to 35000 rpm on the driven pulley.
            Free software for calculating bolt circles and similar: Click Here

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            • #7
              Hmm. I'll have to check the rpm on my tp grinder- maybe it's higher than I think. I'm using a 1/4 inch o-ring on that, and it does blow out-

              Just checked- I can get the driven spindle up to about 15k rpm and the belt is just about leaving the pulley. Maybe it's weak by now though.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #8
                It the rim speed of the driving pulley that counts. The belt won't be going any faster than that regardless of ratios.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  Well, my driving pulley is 3 inches diameter, with the driven one being 1 1/4 diameter. Davids spindle doing 14krpm with a 40mm pulley is going to have about the same belt speed as mine, so the o-ring will have to be stronger than mine currently is, or it will stretch almost to the point of coming off. My belt (o-ring) is weak now I'm sure, so the result is worse than it could be. I could just replace my ring and be able to run the spindle faster, but I don't usually care to run it any faster than I normally do, about 7-8 k. This is with the spindle going about 14k.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    A pic is worth 14k rpm...

                    Without internal supports, a round belt really expands.

                    Most Dumores and commercial grinders ran a thin flat belt... Wonder why ???

                    HP transferable, depends on width/thickness of belt (for flat belts) speed, and diameter of pulleys.
                    Last edited by Bguns; 12-27-2009, 06:58 AM.

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                    • #11
                      Lots of helpful suggestions, thanks

                      sounds like Evan is doing what I want to do so I'll press ahead...

                      Evan, would that setup run for an hour with the belt not overheating?


                      Here is where I am at, this setup works but is nowhere near fast enough. The drive pulley is crowned and has no teeth, tensioner not shown. the ratio is about 2.3:1 giving about 6000rpm



                      A bigger drive pulley is not going to work driven off the spindle because there just isnt enough room so I need another motor mounted somewhere.
                      "...do you not think you have enough machines?"

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                      • #12
                        I've run my mill just lately for several hours under heavy load facing off a new sub table and the belt is holding up just fine.
                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          Originally posted by Evan
                          It the rim speed of the driving pulley that counts. The belt won't be going any faster than that regardless of ratios.


                          True but there are limitations within the ratio's and some can and will cause deflection and stretch due to the nature of the O-ring not having thread reinforcement ---- the smaller the driven pulley the greater the the return curve angle - this is fine if belt speed feet per second is kept within certain parameters but like so many problemo's this situation has two negatives working against it -
                          One is the belt creating its own internal "stir fry" (internal heat) as the smaller the radius is not just added to the FPS its more like multiplied,
                          Two - while the belt is getting all weak and mushy it also has another compound effect that's trying to destroy it - getting from the point A entry of the small pulley and changing its direction to exit point B, due to the belt having mass as darryl pointed out this can cause deflection --- actually seeing the deflection that is causing the belt to lose grip on the smaller pulley is as simple as looking at the trailing side of the belt leaving the pulley,

                          Due to the rubber not wanting to immediately conform it will try and keep the small pulleys radius so what you will end up with is actually an inboard hump instead of a straight line directly back to the larger pulley, The more you see this hump you can also count on one other thing, although you cannot witness it the belt that's leading into the smaller pulley just got done with a huge straight line - the last thing it wants to do is be immediately bent due to both its internal integrity AND the immediate change of direction --- so the first part of the smaller pulley that's engaging the belt is actually barely in contact with it - the higher the speed the more degree's of this critical contact area you give up...

                          This compounded "tug of war" between these forces are met with a slight countering force as the entire belt is wanting to go into a circular pattern - but this is no match for the forces that are going on directly at the radius of the small pulleys entry and exit.

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                          • #14
                            Originally posted by boslab
                            Iu have a little watchmakers lathe and wanted to drill 0.020" holes in jets, had a Viton ring as a belt, it got hot, i toched it some time after and burnt my fingertips with the acid that came out of it!, changed to Neoprene!
                            [it still works]
                            mark
                            Breaks down into Hydrofluoric acid under heat or flame, very nasty stuff.
                            The shortest distance between two points is a circle of infinite diameter.

                            Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

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                            • #15
                              Darryl,

                              Try a smaller length "belt", so it has some loading.

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