A fellow Ev-er down in Goolwa, SA (Rod from Strath Steam) put me onto the idea of laser cut adaptor plates. So I had a go at it for EV#2 (another Charade using Goombi/Eugen's low cost Chinese kit).
The idea is to come up with a DXF file that anyone can download and get laser cut locally. No reason this should be repeated for every conversion, by sharing our files we can drop the machining costs for everyone doing conversions. Even if you are using a different motor, you can edit that layer for your motor and keep the bell housing. The same idea can be used for other cars.
I have no mechanical background so I learnt to drive Qcad (nice free CAD package with DXF format files). There were a few challenges:
1/ Measuring up the bell housing holes. Tricky, I ended up measuring between hole centers using a steel rule, then drawing arcs of that radius on a measurement layer and looking for intersections. I tested by printing on transparency, and cross checking distances between various holes.
2/ Measuring the motor holes. Easy, as the hole positions were 60 degrees apart and the radius obvious.
3/ Aligning the centre of the gearbox input shaft to center of the motor. Very tricky as the gearbox input is recessed into the bell housing.
There are of course many other ways of doing this. The best way I have heard is to put the gearbox on a mill table with calibrated xyz axis. Then just move the mill head to each hole and read off the coordinates.
Anyway I had my adaptor plate cut last week, just $88 for 12mm mild steel ($150-$200 for aluminium). I got (1) and (2) pretty close but was off by a few mm on (3). 1 hour with a good metal file fixed that and I now have a nice alignment between the adaptor plate and the gearbox input spline (measured with a simple gauge).
Pls let me know if anyone would like the DXF file to check out, I am not sure how to attach files to these posts. It's needs a little bit or work to get it spot on, but it's a good start. And at $88 the price is right!
- David
