Chas­sis Lean

RC Car Action - - TECH CENTER -

I have a Vaterra As­cen­der, and ev­ery time I run it, I see the chas­sis lean to one side. Why is this hap­pen­ing, and can I fix it?

Be­cause the trans­mis­sion has more gear re­duc­tion than the axles, twist­ing oc­curs when the drive­shafts try to spin the axles. The twist­ing mo­tion of the shafts wants to turn the gear­box around, and since it’s at­tached to the chas­sis, you get a lean when power is ap­plied. You can’t elim­i­nate the twist, but there are two ways to re­duce it. You can mount up an axle with a gear ra­tio lower than 1.85:1 and in­crease the size of the pin­ion gear to raise the gear ra­tio in the trans­mis­sion. Or you can in­stall a se­cond threaded col­lar on your shocks to limit the travel of the top spring and ap­ply pres­sure sooner to the stiffer lower spring. You can make this mod­i­fi­ca­tion by get­ting your hands on a se­cond preload col­lar and re­mov­ing the knurled sec­tion from it enough so that it will fit in­side the springs. In­stall the mod­i­fied col­lar so that it’s about half an inch lower than the top preload col­lar. Then the bot­tom col­lar will stop the travel of the softer top spring when the plas­tic up­per and lower spring cou­pler hits it. Do this on all four shocks, and make sure they all have the same set­ting.

In­stalling the mod­i­fied preload col­lar will stop the spring cou­pler sooner, which then uses the stiffer lower spring sooner and helps re­duce torque twist. 27

The As­cen­der has a trans­mis­sion with a lower gear ra­tio than the axles, so this causes chas­sis twist when power is ap­plied and the drive­shafts try to turn the gears in the axle.

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