LRP X11 Brushless - TRF501x - pinion wobbles & mesh hard to get right!

[Fiddybux]

Right, this is a bit strange and I have actually fixed it, although it's not a perfect solution and quite sloppy.

Because on the 501x there is quite a distance between bulkheads, the pinion needs to be right on the tip of the motor arms bevelled-edge in order for it to reach the spur.

If you put it right over, so that it is fully (not 3/4 or 1/2) in contact with the spur then when you tighten the pinion it moves off centre, and because it is not perfectly true it wobbles when the motor is running because it is offset from perfect centre. This causes it to mesh perfectly for part of the radius of the pinion and to either be very tight or barely in contact with the spur for the rest of the rotation. This equals scary noises and probably a wrecked spur in the end (and undue motor stresses).

The only way to get the pinion to sit true is to set it back slightly at about 2/3 on the spur gear, but this is also problematic because too far back and it grinds on the belt - too far forward and were back in wobbly land! This is a very very fine line for me and takes ages to get right.

I'm using Losi pinions for this, size 16, because it's all I have. Size 15 does the same, as does 17, because they're right on the end of the bevelled edge on the motor arm and so aren't as tight a fit as they could be (if you slide the pinion back it feels physically tighter and more secure than on the end).

Does anyone have the same problem and is there a known solution, like maybe some different pinions? Are Tamiya or another make of spurs longer / different and solve this problem??

The problem would be solved if the X11 bevelled-edge motor arm was longer, or the spur gear was set closer to the motor, but it isn't and can't be, so that's a dead end I suppose (unless someone knows otherwise).

I'm running the 87T associated spur and not the stock 96T....although I'm pretty sure there would be little difference...unless the 96T spur is thicker.

I have considered grinding the bulkhead down to allow the motor to be closer to the spur, but this seems a bit extreme and a lot of work.

Any ideas, comments, questions welcome.

Thanks.