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Grinding wheel balancing fixture

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  • Grinding wheel balancing fixture

    I'm looking at making a grinding wheel balancing fixture. The types I've seen use a pair of parallel surfaces on which the arbour is supported and the balance point determined. However I've seen another type that uses a pair of rotating disks on either side on which the arbour can sit. I believe the latter type has the advantage of not requiring precision levelling. Has anyone made the latter type or can provide information from which I could fabricate one?

  • #2
    McGyver did a balancer project some time back.



    • #3
      I'm not sure if you're talking about a normal bench grinder or not, but Oneway makes a very simple balancer that made a world of difference on the grinder I use for sharpening lathe tools.


      • #4
        I'm thinking about both bench and surface grinding wheel. I wonder if a small surface grinding wheel is able to overcome the stiction involved in the bearings of a simple stand such as that above?

        The type of stand I would like to find out more about is the bottom one in the page below.


        • #5
          I bought some open (unsealed) skateboard style ball bearings for building a balancer. Oiled not greased. Amazingly low stiction/friction. Definately let you balance a wheel easily.

          Dang, I just noticed those stay with the wheel, iv been wanting a system like that... oh well. Allready gave away my crappy grinder.
          Last edited by Black_Moons; 08-25-2011, 09:53 PM.
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


          • #6
            One of the problems of course is being able to perfectly center the wheel on the balancing shaft, then subsequently mounting the wheel to a grinder while keeping that same exact centering. And before you mount the wheel to the grinder, does the grinder shaft run perfectly true?

            There are always going to be errors here, and those errors can easily be shown with the simple shaft-on-rails as the first picture shows.

            All I'm saying is that even if you took every precaution to mount the test shaft well centered to the wheel, then carefully balanced the wheel, you could still find that it's off balance once you mount it. This kind of suggests that there's a practical limit to how close you should try to get it. You don't need anything more elaborate than what the first picture shows.

            On the other hand, the model with twin discs each side gives you better control over the thing you're balancing- it stays centered within the machine. This would be important when the weight of whatever you're balancing starts to get up there. Motorcycle wheels, while not particularly unweildly are heavy enough that the disc type balancer is normally used. The additional weight and the degree of unbalance tolerable are larger factors than bearing friction, so the disc type has its place- but if you try to balance anything light you'd be better off with the first type shown. Very important is to have the contacting surfaces free of any particles of dust or anything.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


            • #7
              The disk type doesn't require perfect levelling for use. That is its primary advantage. The beam type is simpler however more time consuming to set up.


              • #8
                As to the disk type is there anything special about making one? Do the disks spin while it seeks the heavy spot? If so would you use plain bearings or ball bearings or what? I would like to make one or the other and have it on my list of things to do.


                • #9
                  Originally posted by Dale Lusby
                  As to the disk type is there anything special about making one? Do the disks spin while it seeks the heavy spot? If so would you use plain bearings or ball bearings or what? I would like to make one or the other and have it on my list of things to do.
                  the disks do spin, And you'd use ball bearings, Idealy unsealed if you can stand it, or metal sealed but oiled filled. (less friction then rubber contact seals)

                  definately don't use grease filled bearings but oil filled ones, much lower friction. (VXB bearing has unsealed skateboard bearings for like.. free if they where any cheaper.) Mine only uses 1" OD bearings and no 'disks' but seems to work well enough. the idea of the disks is it incresses the torque on the bearings, reducing thier effective friction. (Of course, your disks must be balanced, and mounted on center, and have a smooth rolling surface free of defects.. Bearing races come prehardened/polished and reasonabley balanced. (also small enough to not matter much)
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                  • #10
                    BM do you have one of these bearing type balancers? Did you make it yourself and would you mind posting a picture. In principle they seem quite simple but I have no practical experience with them and how much the bearing stiction and friction will affect their operation.


                    • #11
                      Electronic balancer

                      I used to work for a company that makes electronic balancing equipment, and have often thought about making a simple DIY electronic balancer. The idea is to make a gadget spins the offending object, said gadget being euipped with a vibration sensor, a strobe light (or LED), and a degree wheel that rotates with the work. The signal from the vibration sensor goes into a zero-crossing detector, which emits pulses, which trigger the strobe light, which indicates the angle of the imbalance on the degree wheel. The same vibration signal can be rectified and fed to a meter to indicate the amplitude of the imbalance. When the amplitude is zero, you're done. The electronics should be PDS (pretty darn simple).

                      Has anyone already done this? Is anyone interested in doing it?


                      • #12
                        I'm nearly finished with a small soft bearing dynamic balancer and am currently working on the electronics. I have a linear velocity transducer and a MEMS accelerometer for each shaft cradle. I've looked at both maximum voltage and zero crossing detectors - I should say I have electronic engineer friends who have helped me look at the options. The max voltage appears to be easier to implement - the zero crossing detector that I have triggers the LED at each crossing - that is at 180 deg. I haven't found a circuit that will trigger at only one crossing.

                        Another necessity is a filter to eliminate mechanical and electrical noise. One of my bigger problems is vibration from the drive motor - I can't yet balance it. That will be the first use of the balancer.

                        All this to say that I am interested in working on this project. I can build and test circuits but am not a designer.




                        • #13
                          Millhand: I think you want an edge detector to turn the output of a compairitor into a single pulse once per revolution.

                          Zero cross is easyer to detect accurately then peak, because there is much higher slew rate (assuming a sinewave signal) at the zero cross, while its nearly 0 at the peak (Any noise/varation in supply voltage will give false peak triggerings)

                          Tanto: its just two bearings side by side with basicly no gap inbeween, bolted to an L bracket I made (Two of these made)

                          I clamp em to a table when I need to use em.
                          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                          • #14
                            Black Moons:

                            Thanks, I'll pass the edge detection suggestion to the guys who are helping me. I did a Google and it looks like that is what I need.

                            Do you have any familiarity with the Retrotek balancing instrumentation package? The local balance guy said I should look for one but he suggested that the current price was in the range of 5K USD. Well that's a non-starter but I'd sure like to know the basic outline of its circuitry.



                            • #15
                              It is possible to use something as simple as a dual-trace o'scope and a pair of tape recorder heads pulled from a couple of junkers. The heads are placed at 90؛ from each other on a shaft that holds the object you're balancing. A shaft greater that one foot length will do.

                              The out of balance object on the shaft will produce a circular Lissajous figure on the o'scope and the maximum deflection will happen at the natural frequency of the shaft and wheel. Attaching a strobe to the Trigger Out will provide orientation of the heavy spot relative to a painted spot on the wheel.

                              This is all added complexity but not much added expense.