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A doozie of A Pinion Problem !

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  • A doozie of A Pinion Problem !

    I've got one for y'all : months ago, while I had a little extra change, I stocked up on scratch build supplies and parts, for future Projects.
    I purchased 5 or 6 all-different Motors, to experiment with and learn from. Here's my problem : one of those motors, a Piranha 21.5k, ( I love the Piranha motors, 21.5 and especially the 25k) ended up in my "Old Junk Motors and Motor Parts" container ! This is a Brand New Motor, mind you !
    What happened was that as I was installing the pinion onto the shaft, I somehow pushed the pinion All The Way up against the motor. Pinion and shaft spin beautifully, but there is literally No Space between the pinion and the end of the motor, to get anything in there, to move the pinion !!
    I might mention, that I have my own ways of pushing pinions on, and have a couple of ways of "pulling" them off. This is because, I purchased a pinion puller for small motors, that turned out to be Just A Fraction, too big ! I was so pissed and frustrated, after spending my money ! So I never bought another puller. I found a guy on youTube that has a simple, but Effective, method of getting pinions off.
    But as I said, it's All The Way, up against the motor, with no way to get anything lodged in there. The only thing I can see to do, is destroy the pinion, to possibly get it off.
    I'm about to begin a Build, that this motor would be perfect for, so I brought it back out. I'd like to use this pinion gear, and not have to use my one last pinion that I have left. I'm making my next Order tomorrow, but all those supplies and parts won't get here, until the end of this week, at the earliest.
    All I need to do, is move the pinion, back near the end of the motor shaft, and I'm good to go ! I know just the position on the shaft, where it needs to be, just by eyeballing it !
    Any ideas, hobbyist's ??

  • #2
    feeler gauges... is the thinnest stainless steel you will find. If you can't get those to work then you'll be forced to grab the pinion with some force (like a vise) and push the shaft out somehow, if that'll even work. It's possible the force needed to hold the pinion will also crush it against the shaft.


    • #3
      Simple solution is to split the pinion and replace it
      Peterborough Ont


      • dinglebery
        dinglebery commented
        Editing a comment
        That's not a solution because he wants to use it! However, he may be forced to do just that.

      • 4424ever
        4424ever commented
        Editing a comment
        Only time Iโ€™ve had this problem I was in the same position had to split it to save the motor

    • #4
      Well,...........if you want to be daring, and, have steady could power up you motor (4/5 volts) ,and with a dremel and a cut-off disc, take 30thou. or so off of the inside of the pinion, to a depth that will allow your puller to slide over it. Do not worry about narrowing the pinion, do not need full width pinions in any situation.

      I have done this more times than I can mention for club members/customers..........all who have somehow forgotten to leave a bit of space .........worst case scenario is that you bugger the pinion and will need a new one.

      It is a good idea to wrap a bit of masking tape around the Piranha cooling holes to stop brass bits entering the can.

      Take a walk on the wild side .

      Chris Walker


      • Kevan
        Kevan commented
        Editing a comment
        I've never tried this but will try to remember next time the sturdy blunt knife trick doesn't work.

    • #5
      You should be able to wedge it out by driving a flat head screwdriver blade between the pinion and motor end. Put the pinion in a vise and push the screw driver between the motor and the vise. It doesn't have to be as tight as you might think. The pinion will come off pretty easily with little to no damage. A really tight pinion may require another screwdriver on the opposite side, to apply even force.
      Attached Files
      Last edited by Bal r 14; April 3, 2022, 03:35 PM.


      • #6
        Edge of a sturdy knife and slowly lever it along until there's room for your puller.
        Kevan - Isle of Man
        Life is like a box of Slot cars...๐Ÿš“๐Ÿš—๐Ÿšš๐Ÿšœ


        • #7
          I would strongly advise against using either a screwdriver or blade to pry off a pinion,......too many bad things can happen.

          1/ As the can bushings on these motors are press fit (and the cans are made of soft steel) any undue pressure on one side of the motor shaft when levering off the pinion can tweak the alignment of the can bushing, or, slightly distort the can face....not good

          2/ Similarly, levering the pinion, can distort the bore of the brass pinion, which can introduce a slight wobble in the pinion......again,....not good.

          While you may get lucky, you may not,.....I have seen this happen too many times over the years.

          Chris Walker

          PS The only time a blade should be used to "slide" a pinion is with solder on pinions. (which do slide on the motor shaft) .....once the solder has been melted with an iron these pinions can be moved with a blade


          • #8
            I use to use diagonal cutters with a sharp cutting edge. It's like driving in a wedge on both sides of the pinion at the same time. Just a small pair will do.
            Butch Dunaway
            Oxford, Ohio


            • #9
              I have used side cutters (diagonal cutters) like Butch says....and I have done the Dremel thing like Chris says too. Don't worry about the Dremel and the motor shaft, the sparks will tell you if you get down to steel but it's easy enough, if relatively slow. Patience will save the motor though.....and Predators are nice motors.
              Come Race at The Trace!
              Timberline Trace International Raceway - SW of Mpls, MN


              • #10
                The screwdriver method works just fine, it doesn't require enough force to damage anything. Those pinions are not on that tight. Do you see any kind of damage or distortion in the image I posted above? If it feels like it's not coming off fairly easily, stop trying!
                Last edited by Bal r 14; April 3, 2022, 05:07 PM.


                • #11
                  I like post #3 the best. You didn't ask, but I can recommend a simple way to prevent this from happening again.


                  • 6666hotrod
                    6666hotrod commented
                    Editing a comment
                    Let me know !

                • #12
                  You could also probably use an old wood chisel that you didn't care about. Sharpen it to a sharp edge to get it started.
                  Butch Dunaway
                  Oxford, Ohio


                  • #13
                    I have done this a few times , be sure to oil first then pry off with an exacto
                    Courtney Smith
                    Chattanooga TN


                    • #14
                      Of the solutions proposed I prefer Chris Walkerโ€™s option. I naturally dislike forcing something between the pinion and the bearing/case as that relies on the armature or commutator being pushed up against the case/bearing on the inside of the motor. I would prefer not to do that.


                      • #15
                        Smack the end of Armitage shaft one or two times with a little hammer this will get the gear off the bearing and a little bit of room to get something thin to prise the pinion enough to get a puller under it!