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Changing gears on cars w/plastic wheels & knurled axles

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  • Changing gears on cars w/plastic wheels & knurled axles

    How do you do it? I've done one. It was a Scalextric A1GP (open wheel) car that stripped the crown. The old gear needed to pressed off, and new gear pressed on. I kluged something together, but it wasn't pretty, and I'm not sure that I didn't damage the gear and/or bushing. I also have other cars with plastic wheels and knurled axles on which I'd like to change the gearing. I don't really want to have to buy a $20 axle set every time I want to change a gear ratio.
    Last edited by GearHead36; May 18, 2021, 04:28 PM.

  • #2
    Knurled axles are not designed for easy replacement of wheels and axles. Depending on the knurling pattern, sometimes you can pull wheels straight off and they will go back on again. But if you twist them off, then it's pretty tough to keep them on without glue. Using CYA on wheels is well established....it has a low shear strength so you can pull wheels off again if needed.

    But the real issue as you have noted is the bushings. If they allow the knurling through, they are too sloppy to let the car run well (see Artin, among others). That can be fixed with a light coat of CYA inside the bushing while the axle is turning, but it's a temporary fix.

    If you need to replace the crown gear, it's best to replace the gear, bushings, and axle together. This often includes a replacement of the wheels, but that depends on the manufacturer of the car as some use odd size axles. I keep a stock of 3/32 piano wire for replacements, although if you want higher performance drill rod or axles from slot car manufacturers will be more accurate. I keep a stock of bushings, gears, and wheels for replacements.

    So.....it's a pile of spare parts, or a replacement axle set if the gear strips.

    And, by the way....if the gear strips, why did that happen? Did the motor come loose? If so, that needs to be fixed before another gear or rear end set gets ruined.
    Come Race at The Trace!
    Timberline Trace International Raceway - SW of Mpls, MN

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    • #3
      In theory you can enlarge the hole in the wheel, insert a piece of brass tubing, then superglue the wheel back onto the axle.

      In practice you are better off replacing the whole rear axle assembly with better aftermarket parts. That knurled axle assembly is unlikely to ever run true. Getting new rear wheels that look like the originals will be a project, if that is important to you.

      It would be nice if the manufacturer offered an upgraded rear axle assembly with a straight and hardened axle, and set-screw gear and wheels. Wheels that look authentic. Snap out the old axle, snap in the new, and have a much better car with little effort.

      But the manufacturers that make cars with knurled axles aren't marketing to serious racers. There are folks who do make race-ready cars, but their products cost quite a bit more.

      Ed Bianchi

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      • #4
        You could go to the Scalextric USA site and see if a complete replacement rear axle assembly is available for your car, that would be a lot less expensive than using aftermarket parts. I just checked the site and there does not seem to be a rear axle assembly listed for that car.
        People that race their cars, especially without traction magnets, would often be inclined to use aftermarket parts in which case they might have what you need hanging around. You might try a wanted to buy posting.

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        • #5
          If you are keen on using the stock rear axle set-up, and are looking to change gear ratios,...why not change the pinion up or down a tooth ??.......much less room for error.

          This will eliminate the fussing around with wheel removal/installation, and will also be less expensive,..if that is of concern.

          Cheers
          Chris Walker

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          • #6
            Originally posted by chappyman66 View Post
            And, by the way....if the gear strips, why did that happen? Did the motor come loose? If so, that needs to be fixed before another gear or rear end set gets ruined.
            I was truing the rear tires on a sanding pad. After getting the new gear on the axle, I found that the bushing mount on the chassis had broken. THAT'S why the gear stripped. Irritating, as I don't think that chassis is available separately.

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            • #7
              Originally posted by RichD View Post
              You could go to the Scalextric USA site and see if a complete replacement rear axle assembly is available for your car, that would be a lot less expensive than using aftermarket parts. I just checked the site and there does not seem to be a rear axle assembly listed for that car.
              People that race their cars, especially without traction magnets, would often be inclined to use aftermarket parts in which case they might have what you need hanging around. You might try a wanted to buy posting.
              Unfortunately, the local club is a big fan of traction magnets. So anytime we run A1GP/Formula cars, we run traction magnets. I would prefer to run them no-mag.

              BTW... W9331 Rear Axle Assembly, A1GP. I guess this is what I'll need to use.

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              • #8
                Originally posted by chrisguyw View Post
                If you are keen on using the stock rear axle set-up, and are looking to change gear ratios,...why not change the pinion up or down a tooth ??.......much less room for error.

                This will eliminate the fussing around with wheel removal/installation, and will also be less expensive,..if that is of concern.

                Cheers
                Chris Walker
                What's the smallest pinion that won't cause mesh issues on an inline? I don't really want to change the gearing on my A1GP's, but I have a Scaley Ford GT GTE with slim-can motor with 9/27 gearing, which is way too tall for that motor. I'd like to change the gearing on that one if I could to make it more equal to my Scaley 911 RSR, with s-can and 9/27 (3:1) gearing. Scaley's s-can is rated for around 20K. The slim-can... 26.8K. To get the same axle speed as a 20K motor with 3:1 gearing, I'd need right at 4:1 gearing, which would require a 7T pinion. Would a 7T pinion work?

                Thanks, everyone for the responses.

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                • #9
                  MR Slotcar offers an 8T 5.5mm diameter pinion for slim-can motors (1.5mm dia. motor shaft). I have not seen a 7T 5.5mm diameter pinion for the 1.5mm motor shaft but other forum members will chime in if they know of one. Here is a link to the 8T pinion:

                  MR Slotcar 8T Pinion

                  Last edited by SCC_Steve; May 19, 2021, 11:27 AM.


                  www.slotcarcorner.com
                  email: [email protected] phone: 603.753.6263

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                  • #10
                    You could try a 7 tooth pinion. I do believe MR Slot car has them. You will need a 1.5 for that motor not a 2mm shaft size that is on your other cars.
                    Mike
                    Clover Leaf Racing 7746 Clyde Road Fenton MI 48430 U.S.A. 313-473-SLOT
                    web site: https://cloverleafracing.com Facebook: http://www.facebook.com/cloverleafracing
                    YouTube Chanel: http://www.youtube.com/user/CLR132slots?feature=watch

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                    • #11
                      Originally posted by Slot Car Corner View Post
                      MR Slotcar offers an 8T 5.5mm diameter pinion for slim-can motors (1.5mm dia. motor shaft). I have not seen a 7T 5.5mm diameter pinion for the 1.5mm motor shaft but other forum members will chime in if they know of one. Here is a link to the 8T pinion:

                      MR Slotcar 8T Pinion

                      Thanks, Steve.

                      Originally posted by Mikeinclover View Post
                      You could try a 7 tooth pinion. I do believe MR Slot car has them. You will need a 1.5 for that motor not a 2mm shaft size that is on your other cars.
                      Mike
                      MR Slot DOES have 7T pinions, but they're 4.5mm. Are those the same pitch? I could get it to mesh by shimming the axle, but only if the gear pitches match.

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                      • #12
                        Originally posted by GearHead36 View Post
                        What's the smallest pinion that won't cause mesh issues on an inline? I don't really want to change the gearing on my A1GP's, but I have a Scaley Ford GT GTE with slim-can motor with 9/27 gearing, which is way too tall for that motor. I'd like to change the gearing on that one if I could to make it more equal to my Scaley 911 RSR, with s-can and 9/27 (3:1) gearing. Scaley's s-can is rated for around 20K. The slim-can... 26.8K. To get the same axle speed as a 20K motor with 3:1 gearing, I'd need right at 4:1 gearing, which would require a 7T pinion. Would a 7T pinion work?

                        Thanks, everyone for the responses.
                        If you want to use the stock axle and Crown on either of your Slim-can powered cars, you have a choice.

                        1/ You can use a 1.5mm bore 5.5 mm diameter pinion...........and without really buggering up the mesh, 8T is the smallest you can go. If you can find a MRSlotcar #MR4138 pinion, it already has a small nub built into it so the gear mesh will be perfect. as it will align. itself with the trough on your Crown. You can use anyones' 1.5mm bore pinions, but, you will need to use spacers to center the axle to obtain a good gear mesh which, entails taking the wheels off/on, which sort of defeats the whole process.

                        2/ You can buy a 2.0mm bore 5,5 mm dia pinion and use a 1.5mm id. 2.0 mm od piece of tubing (lots of slot shops sell these)........the tubing is pressed into the pinion, and this whole assembly is then installed to the motor shaft. Again, in a 5.5mm dia. an 8T is as low as you can practically go.

                        Both of these options may sound a bit finnicky, but once you have done one, both are fairly simple.

                        If you need to go smaller than an 8T pinion, you will need to but pinions of smaller diameters, and you can find pinions as low as 6T in a 4.5 mm bore.............anything smaller than a 5.5 mm bore (using your stock Crown/axle setup will require you to use either spacers to center the axle,.....so, if that is the case, it is adviseable to make the switch to removeable wheels on a new axle with new bushings and a new Crown.

                        Hope this helps, and if you need more help, and would consider sending me your phone #, I will be happy to give you a call,.........it will save my two typing fingers !!

                        Cheers
                        Chris Walker


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                        • #13
                          already covered

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                          • #14
                            The 8 tooth is the same pitch as the normal pinion. I do have 1 MR4017 in stock. It is a 1.5 shaft 4.5 diameter 7 tooth pinion.
                            Mike
                            Clover Leaf Racing 7746 Clyde Road Fenton MI 48430 U.S.A. 313-473-SLOT
                            web site: https://cloverleafracing.com Facebook: http://www.facebook.com/cloverleafracing
                            YouTube Chanel: http://www.youtube.com/user/CLR132slots?feature=watch

                            Comment


                            • #15
                              Originally posted by Mikeinclover View Post
                              The 8 tooth is the same pitch as the normal pinion. I do have 1 MR4017 in stock. It is a 1.5 shaft 4.5 diameter 7 tooth pinion.
                              Mike
                              Steve, If you choose to get this pinion from Mike (Cloverleaf),...while it will mesh just fine, and is a really top quality piece, be aware that you will need to control the lateral rear axle movement with spacers in order to adjust/maintain the gear mesh. This is a result of this pinion being 1.0mm less in diameter than the stock pinion, and, as well, this pinion does not have a 2.0 mm "nub" to control the lateral movement of the Crown.......neither are big issues, but, FYI, it will not be a straight swap.

                              So, while this pinion will work perfectly well ( it is steel/.....good !!,....and all MRSlotcar gears are cut by a very high end US gear producer),....it will entail removing/re installing the wheels to do a proper job.

                              Cheers
                              Chris Walker

                              PS All of the well known Pinions/Crowns/Spurs currently produced by the popular plastic car manufactures, are .5 module (roughly 50 pitch), so there is no need worry about mixing brands.

                              The only issue that can occur is if/when you choose a specific tooth count for a given gear diameter that is too far off of "ideal",......but that is for another thread !!

                              Last edited by chrisguyw; May 20, 2021, 10:58 AM.

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