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Shaft Friction

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  • Shaft Friction

    A few weeks ago a friend of mine contacted mo to help with a job he was biding on. Part of project was to place into service waterwheel that has been Idle for several years and never used. There are several issues that need addressed but the one that is bugging me currently is that of power transmission from; the wheel to the shaft and from the shaft to the additional equipment. The issue is: the wheel shaft is not keyed.
    Wheel speed is only about 10 rpm but we think we will be producing about 8 hp. So that is a lot of torque. Shaft Dia. is 3 7/16. The wheel is attached to the shaft with a split coupling that is clamped around the shaft much like a split collar. so I am concerned about slippage between the wheel coupling and the shaft and also on the output end of the shaft where I attach a pulley for power transmission. The outboard end of the shaft is not keyed either so I must "clamp" to the shaft also. Welding is out of the question. wheel/shaft dissemble is not an option.
    Has anyone had any experience increasing the friction of a power coupling by device; wrapping a shaft with aluminum oxide paper (sand Paper) and clamping around that with couplings, bushings etc. IF so what is your guess as to the benefit? Or I am open to other suggestions as to how keep my device from slipping on the shaft.

  • #2
    You could easily grind a small flat with an angle grinder for a set screw or two.

    With skill, paitence and much test fiting, you can key a shaft using just an angle grinder and files (Well, technicaly just files, but the angle grinder should really speed up the roughing out)

    a touch of loctite might help too.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


    • #3

      Could you drill a hole through the collar and the shaft and put a bolt through it?



      • #4
        Another key form -

        You can also key a wheel to a shaft with a round pin. Drill in from the end of the shaft and parallel to the shaft where the collar and the shaft meet. and then drive the round pin in the hole. May notr be as nice as a square key, but that's how they did it before square keys.

        Have you done anything like lock the shaft and then load the wheel to see if it slips? Those taper locks can exert a trmendous clamping force on a shaft. If necesary you can tighten the taper collar, smack it a few times with a hammer and tighten it some more. Even more clamping force.


        • #5
          The proper way to do it is with a split taper sheave. It can provide enough clamping force on the shaft to run without a key.

          Free software for calculating bolt circles and similar: Click Here


          • #6
            If you really see 8 hp @ 10 rpm, that's only 4200 foot lbs. I say only because you have a nearly 3.5" shaft to work with.

            There are bushings out there 3-7/16" diameter that can transmit 3 times what you need. If you've got an appropriately sized split taper bushing, I wouldn't worry about keying anything.


            • #7
              Sounds like a case for wash, rinse and Loctite!

              If you go for kf2qd's pin in the end of the shaft you can tap the hole and screw a bolt in.


              • #8
                It ain't never gunna slip.
                No need for a key.
                I've worked on stuff in grain elevators with a similar situation.
                Sounds like no problem.



                • #9
                  Evan is right on the mark with the taper sleeve.
                  However, given the numbers involved, you could do a quick "check"
                  based on what the fasteners can do for you -- I imagine you have
                  two bolts holding the split collar together?

                  Check out the charts (online, etc) for bolt clamping forces. Torque
                  them properly and you'll get a good bite on that shaft (assuming there
                  is enough clearance between the split hub that it doesn't bottom out when

                  Go to a larger fastener (which might mean a beefier hub) if you want
                  higher clamping forces.



                  • #10
                    Originally posted by Doozer
                    It ain't never gunna slip.
                    No need for a key.
                    I've worked on stuff in grain elevators with a similar situation.
                    Sounds like no problem.

                    I agree. No way that thing is going to slip.


                    • #11
                      Another one for Taper-Loc, but you say it's in situ and hasn't been run, so you need to check the condition of the shaft and existing bolted clamp.

                      Regards Ian.
                      You might not like what I say,but that doesn't mean I'm wrong.


                      • #12
                        How about a taper pin, maybe #7 or #8?
                        Duffy, Gatineau, Quebec


                        • #13
                          Thank you for the inputs.
                          I think a tapered bushing in a hub would be perfect except, I can't get access to the ends of the shaft to allow sliding a solid ring over the shaft.
                          I am now thinking along the lines of a split flanged collar/coupling that I could place on each inboard side of the wheel and clamp over the shaft with bolts perpendicular to the shaft to clamp it to the shaft and bolts thru the flange to attach to the Water Wheel. Maybe with a long enough coupling and enough bolts it should hold. Does anyone know of a manufacturer tho makes such a product? I'm afraid my 10" SB isn't the right machine for the job.


                          • #14
                            Your getting carried away with something that will never cause a problem. When you clamp the split collar down on the shaft it will NEVER slip. Your not going to see a shock load on the water wheel and shaft nor will there be a shock load on the output side. I doubt that any water wheels used a key in the shaft. Some water wheels use wood bearings.

                            Was the water wheel made by a factory or an individual?
                            It's only ink and paper


                            • #15
                              It is estimated the wheel will produce about 5300 Ft. Lbs. of torque when running.