Wednesday, June 10, 2020

Wltoys 12428b (part 26: Two bent drive shafts)

So we've been having a bit of fun lately, and so this morning I was doing a little proactive maintenance on my boys car; his always seems more .. agricultural .. than mine and I wanted to have a closer look.  Among the general increase in wear and tear (he's a kid) I noticed that both drive shafts (front and rear) on the right hand side of the car were bent.  And during disassembly I then broke the screw holding the pinion to the shaft (as has happened elsewhere on these cars).

Figure 1: Bent and broken

Ignoring how the bent shafts might have happened I was able to get his car working smoothly by replacing the whole rear diff assembly and also a front CV shaft from the spare parts car.  The specific replacements of the parts are below, and I ordered them from Bangood.
The rest of this article discusses how to repair the bent shafts, and replace the broken screw.  It does assume you have seen inside the rear diff of a 12428b ;)

After rolling it on a flat surface, I found the high side of the rear axle, I held the axle in a vice and tapped the high side with a light hammer.  After repeating this a few times it came good.  Or so I thought; I then put it in a drill and it's still out of round by half a mm or so.. hmm..

Harder was the repairing the broken screw which had to be drilled out to 2.5mm and tapped at 3mm (I've also had to do similar previously).

Figure 2: After drilling out the broken screw

In Figure 1 the parts are lined up screw, spider gear, axle housing and axle shaft, with the (now broken) screw fixing the spider gear to the shaft.  During reassembly I didn't have a m3 screw with a small enough head to clear the spider gears, so I had to phone my friend Randal who specializes in such things :)

And finally, the front CV shaft was also quickly fixed with a couple of gentle taps of the ball pein hammer. 

Sorted :) .. hmmm but now what .. ;)

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