Hi fellow Esk8ers, I recently finished my first e-board and am having great fun with it. Just a while ago, I had been riding it in the local park, when I notice that the motor mount had bend/twisted. It had really surprised me as it was 6 mm solid aluminium. (which I bought of eBay and was weld on by my metal tech teacher at school) I believe that it may bend/twisted because of the continuous bumps in the bricks. When I asked my automotive teach at school he was convinced that it had to do with the torque of the motor. I have listed some pictures down below and would like to hear your theories regarding this issue. I was thinking to use the schools CNC machine and make a new and improved mount. My knowledge of CAD design is poor, therefore hope that you might have a file that could help me.
(hope the images show how the motor mount is bend)
I would have to agree with your teacher. The torque of the motor is causing the twisting across the weak part of the mount, that is, the thinner middle area. I would imagine if it was not slim in the center, it would probably not have twisted as easily.
As for motor mount designs, it may help to look around on the forum a bit first, there are a ton of different ones
To me also looks like the weight of the motor has twisted the mount, it bends the right way for this. You can get peaks of high g-forces going over bumps, together with too little width on the mount and maybe soft alu type, this could happen.
If you have access to the aluminum welding equipment still, (bend it straight first, and) add another piece of aluminum at a 90 degree angle to the first one. So it makes a triangle between the motor, the current weld, and closer to the bushings
I used to have a similar aluminum mount which costed me 25€ and broke after 8 months. I then asked a workshop to weld a couple big and thick steel washer on each side of my trucks (in case some day I wanna go for a dual motor setup):
I’ve designed and printed a pla support for the motor, it broke the first week
I’ve redesigned it thicker and since then (6 mothes ago) its dirty but intact in terms of structure:
I haven’t seen a lot of similar builds and I think this setup is better in some way because even if it will maybe break at some point, the washer will not, and the support costs less than 2€ and a couple hours to print
As others already said, the 6mm is part of the problem, but the other part is the weld, i don’t know what alloy you bought, but even if it was a 7075 ou 6061 they would bend. What makes them strong is the heat treatment and aging, all of this is lost when you weld and let it cool naturally, the correct process would be to heat treat the entire piece but even so it would be weaker than the original.
And by the way, welding 7075 without specific equipment and post treatment is asking for problems in the long term since the internal stress cause micro cracks all across the surface
I’ve redesigned it thicker and since then (6 mothes ago) its dirty but intact in terms of structure:
