This week has just been a torrent of Deathblades work. I’m (kind of…) proud to say that the skate motors are all finished. Well actually, two of them still need their share of custom arc magnets, which I hope to take care of soon through Supermagnetgeorge again. At the least, they can support my weight and I can skate around unpowered.

In other words, I’ve successfully built a set of roller blades. Hurray.

Yesterday, I was able to terminate and test one motor, so today I repeated the process for all of the remaining ones.

Here they are, sitting on the “drying rack”. Again, I kept C-clamps on the pigtails so they would be pulled down as low as possible. This time, I mixed up some thin laminating epoxy and let it flow across the wires. The 5-minute stuff I used before was sort of gel-like and didn’t really flow well.

To make the thin epoxy set in under a day’s time, I added a few times the recommended amount of hardener. This probably trades off alot of strength, but it’s not really structural anyway.

Know what’s cool? Having two motors.

Know what’s not cool? Not having enough breadboard space to put another DEC rig on. I wasn’t that interested in pursuing the simultaneous control of both motors immediately, so I decided against mocking something up. To test the other motor, I just swapped wires.

What I found very interesting was that the motors were heavily timed – possibly up to 30 degrees difference between the two directions.  Both motors registered about 1,600 RPM in the “reverse” direction, where reverse is defined as the direction the frame would fly in if I dropped it on the floor with the motor spinning. They only achieved around 1,300 in “forward”.

Additionally, one of the motors required a cyclical shift of the phase terminations (i.e. motor-A to controller-C, C to B, B to A), but the other one only ran with A and C swapped but B unchanged.

Motors are strange.

The fake motors get the red wheels. I only ordered 2 sets of magnets and haven’t gotten around to ordering the rest, so for now one skate (the left side, as I’m right-dominant) will have dummy motors.

Or, if you think of it another way, motors with really really crappy Kt.

So what did I do with two dummy motors? Put the dummy skate together!

The stock ‘blades used a very unique M6 bolt with a very flat and broad head to attach the wheel frame to the boots. I wanted to keep that bolt since it was unlikely that I could find a similar bolt.

Consquently, I decided to extract the matching nut because there was no way you could get me to dig through all of MITERS for a M6 nut.  The stock wheel frames split in two after all hardware is removed, so extracting the nut was simple.

The stock nut was also a very broad kind, which translates to a bit more rigidity.  Unfortunately, I can’t remove the boot without also removing the wheels. Oops.

And here is the dummy skate.

I decided to orient the motors such that their cables faced inwards. This is probably a position that’s safer in terms of snagging. The good news is that they all reach to the middle of the frame, so any conceivable control board orientation is achivable.

The bad news is there’s no board to attach them to yet. Sigh.

And here’s both of them!

Clearly I’ll have to take these apart again to install the rest of the components, but in the mean time, publicity shot!

I took a short unpowered run around the hallway to see if they were still useful as.. you know, skates. The LRK winding and magnet arrangement yield very little drag and ripple torque. I suspect my bearings are contributing more loss than the motor drag. Overall, they “skate” well.

So if the motors or batteries ever become dysfunctional, the whole thing doesn’t become instantly useless. Such is the beauty of hub motors.

Read more “Deathblades: Enough for Cosplay”