If you’ve spoken to me in the last four months, you’ll probably know that I’m working on a project to scratch build an electronically controlled dynamometer for the student air motors as part of MECH 1400. The end goal is to have a magic testing station that ‘plugs’ into any student air motor and in five minutes tells the whole class how efficient the design is.
Sounds tricky right?
I had something going at the end of 2021 but there were a lot of issues around electronic load control. What made this even more difficult was that the whole system was dependent on input from a student made air motor which was inefficient, non-portable, and prone to falling apart. To address this, I decided to put together a replacement with much better control - a BLDC motor and Electronic Speed Controller (thanks @ben_van).
I showed some pictures of this set up last week:
Thats an XNOVA 4612 BLDC motor on the left. Its connected (badly) to a QMOT BLDC motor with a flexible coupler on a 3d printed shaft… yuck. Figuring that this would fail almost immediately, it was amended with a cool 3d printed component that replaced half of the flex coupler and bolted onto the mounting holes on the XNOVA.
(that’s the part that was replaced, half of the flex coupler, in my hand)
So now it all spins up pretty well. I’m getting a rectified DC out of it thanks to an IXYS FUS 45-0045B schottky three phase bridge rectifier and dumping that into a little adjustable buck converter and 25W resistor. Increasing the output voltage on the buck converter (a DFR 1552) increases the load on the XNOVA which then draws more current as expected.
More detailed testing to come, ideally this whole thing will run off the one raspberry pi stack.
