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Locating the rear axle

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  • Locating the rear axle

    My scratchbuilding is limited to one or two very basic chassis each year for Showdown cars. By "basic", I mean to say that I'm happy if the body stays on and the car makes it around Harry's oval without leaving a trail of parts. Anyway, there seems to be two ways of locating the rear axle side to side. One is to let the motor shaft engage the groove in the crown gear hub. Simple, with the added benefit of automatically setting the gear mesh. The other is to cut the motor shaft short of the crown gear and cut axle tubes to set the track width. Is one method any better than the other?

  • #2
    I set the width of the brass tube at or close to the width needed for the body. A little narrower allows for some shimming later if required. This allows me to go with the gear aligned axle or cut to width.
    You can see the shims in the pictures of the chassis if you enlarge it. I wasn't sure if I was going with an offset chassis so this allowed me to easier make changes later. For the showdown I cut single shims to length to achieve the maximum width.
    Click image for larger version  Name:	IMG_0707.jpg Views:	0 Size:	3.17 MB ID:	141168
    Ayton, ON Canada


    • #3
      I am not a big fan of using a gear boss to locate the rear axle. I prefer to use spacers to limit side play to a minimum and then adjust the crown gear for the proper mesh. The end of the motor shaft would first have to be shortened. I loosen the crown gear set screw, put some plastic bag material between the crown and pinion gears, push the gears together and tighten the set screw. With the plastic removed the mesh will be perfect.


      • #4
        I use axle stops or spacers where allowed in our club rules. removing the end of the motor shaft from the crown eliminates another source of friction.


        • #5
          I have done both and don't find any difference in performance. However, letting the motor shaft fit into the groove in the crown gear limits the gear ratios you can use, without changing both gears. You can experiment with lots of different pinion/crown gear combinations if you don't use the groove in the crown gear.


          • REL13
            REL13 commented
            Editing a comment
            That's not true, if you look at SCC gear chart for inline, you will see that if you use the 5.5mm pinions no matter how many teeth it has, it will fit any of the crown gears. hope this helps.