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About Soldering Pinions

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  • About Soldering Pinions

    Before I begin my current scratch build project, I want to ask a question (at the risk of making me look intellectually-challenged, or flat-out ignorant). This project will use an ARP tapered pinion (48P)! Upon delivery, when I opened my parts order, I discovered this pinion, is a Solder-On pinion ! I have no experience with soldering a pinion onto a motor shaft, and am quite concerned about trying it ! Here is my Question : MUST, this pinion, be soldered ?? And just for the general knowledge, solder-on pinions, won't hold (will slip) if not soldered ? I fear getting solder where it should not get to. I know it's just likely time, to learn how to do this, but I had to ask.

  • #2
    Yes, soldered pinions have a larger bore than press-on pinions (which are slightly undersized for the friction fit).
    Clean, flux, and tin the motor shaft (not the pinion), generally just a little bit away from the end of the shaft.
    Place the pinion on the end of the shaft.
    Press it on using the tip of the soldering iron (e.g. hold the iron tip against the pinion/shaft. It will take a few seconds but once everything heats up it will slide right into place.

    If you use acid flux, be sure to clean everything afterwards.
    Come Race at The Trace!
    Timberline Trace International Raceway - SW of Mpls, MN


    • #3
      I use a torch and keep the heat on the pinion, not the motor shaft. Put some putty around the base of the motor shaft to absorb excess heat; any kind will do. Hold the motor upright. When the pinion gets hot enough, put some solder on the end and it should suck right in. I don't like using soldering guns because you won't get adequate heat penetration. It's just like soldering copper pipes.

      A tapered pinion may hold without solder, but not likely.
      Last edited by Bal r 14; September 24, 2022, 05:30 PM.


      • #4
        This is how I deal with pinions:
        1. tight enough to need a pinion press = no need for solder
        2. if it needs soldering I tin the motor shaft first after rolling the motor over with fine diamond needle file on the shaft where the pinion is going which slightly roughens the metal (sometimes this is enough to hold the pinion). Use acid flux and normal 60/40 solder, clean with lighter fluid and an old toothbrush.
        Kevan - Isle of Man
        Life is like a box of Slot cars...🚓🚗🚚🚜


        • #5
          Thanks, guys !!


          • #6
            Hello 6666hotrod,...if you are nervous about soldering the pinion, you can use some "RED" will hold up just fine !! Lots of racers use loctite to secure both pinions and axle bushings, on motors much more powerful than the ones you are likely using

            Using a toothpick. place a drop into the bore of the pinion on the side of the pinion that will face the motor, and press the pinion on. Placing the loctite on this side of the pinion will force the loctite along the bore of the pinion, and the motor shaft, and will push it away from the motor. Do not put the loctite on to the motor shaft, and press on the pinion, this may result in the loctite being forced along the motor shaft,and ,if you are unlucky, into the motor bushing.

            Let the loctite set-up for an hour or so.

            To remove the pinion. touch an iron to the pinion (the heat will soften the loctite) and you can pull it off.

            Chris Walker
            Last edited by chrisguyw; September 24, 2022, 10:09 PM.


            • 6666hotrod
              6666hotrod commented
              Editing a comment
              W o w : "myDude", Chris, to the rescue, yet again. Man, you saved the day !! I really appreciate this info, contributing to expanding my Hobby-education. I would like to thank ALL of you, that took the time to help me !

            • Brumos RSR
              Brumos RSR commented
              Editing a comment
              6666hotrod: We all stand when we read SirChrisGuyW post 😀

          • #7
            I've got nothing better to do, so...

            I endorse using Loctite rather than soldering. Chrisguyw's advice is spot on. However, just to be contrary, I use the blue, breakable grade of Loctite instead of the 'till-death-do-us-part red Loctite. You can pull the blue Loctite without heating. Either grade of Loctite will work just fine.

            If you insist on soldering, definitely use acid flux, but make absolutely dead certain sure it doesn't get down into the motor bushing. You might try pushing a sheet of paper down on the motor shaft so it punches a close-fitting hole through. Cover the bushing with the paper to stop any flux leaking down the shaft. Once your soldering is done just rip the paper off.

            If you're using a torch and you're worried that the paper will catch fire, you can smear a little bit of rubber cement over the bushing. It will stand up to the heat but peel up easily once you're done.

            FYI, that rubber cement trick is one of my favorites when I need to mask parts I'm soldering. Goes on easily, stays put, stops flux, stops solder and comes off clean.
            Ed Bianchi
            York Pennsylvania USA


            • 6666hotrod
              6666hotrod commented
              Editing a comment
              Good stuff, HO RacePro !! ...good thing I hadn't yet transferred this series of communications onto my latest SlotCar Reference Files, before you shared this : I need ALL of the great information contained in This thread, for reference when and if needed !

            • Wobble
              Wobble commented
              Editing a comment
              Yep same, I've always found Loctite blue more than adequate.