Monday, September 16, 2019

Wltoys 12428b (part 22: rear wheel drive conversion)

I was getting some quite serious While i was doing some maintenance

So I was halfway through installing a spare front diff from the parts car when i decided I'd had enough of front diffs and their noise and friction and various wear issues, so I decided on a whim just to pull it out, and the front drive shafts as well:

Front diff and drive shafts notable in their absence.

So although it's dark out, i went up and drove it on the road.  On a LiIon battery in storage mode (~7.4v) and with throttle trim turned right up, the thing absolutely flies.  It's a completely different car!  I'm slightly in awe.

  1. It accelerates like a demon, especially on the road (traction)
  2. It's relatively very quiet and the motor noise is much more evident.
  3. It doesn't suffer from power on under-steer.
  1. It's really fast.. ;) and i hit the curb more than once :/
  2. The brakes only work on the rear wheels..
  3. Toe out factory front wheel alignment causes tracking issues.
  4. More power through the rear wheels induces wheelspin
  5. The open rear diff servers to accentuate this issue.
  6. The tail-shaft CV joint angles could be improved (noisy).
I do have even more front diffs on order, but i don't know what to do now!

UPDATE: I took it up the hill to play on the dirt and the major limiting factor regarding acceleration is the open rear diff.  You can hear it variously spin up one wheel or the other, and it won't power slide as it lifts the inside wheel and just spins it.

I fixed the CV joint issue by lowering the rear ride height a bit.  Fwiw; for ease of maintenance etc when on the bench I have the car in a cradle (you can see one of the dowels in the above picture).  This means that there is no weight on the wheels and the extra droop causes the CV noise issue.

Possible mods, lock the rear diff and fit adjustable steering arms.

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