Thursday, March 24, 2011

p0w3r Drive: Cut.

Mad rush to get the wheel spinning before Spring Break. It is Spring Break now, was I successful?


First operation was machining of the endcaps as discussed in the previous post.

Mounted to the lathe through a 5/16-18 cap screw and a copious number of hex nuts. Spun counter-clockwise at about 200 rpms for something that large in diameter.

Resulting part. Pretty shiny on all surfaces touched by the cutter. I did notice some wobble produced from radial play between the cap screw and the inner bore of the plate. This must have been what Shane was talking about. We will see if this proved troublesome enough to require correction, but considering the history of this project (v1 - v2 rebuild), I'll probably end up making new ones out of frustration.

The build is progressing very well so far! All components considered, it weighs just over two pounds, which is 2x lighter than the current kollemorgen system on my scooter. Speaking of which...

Stupid things to do on an electric scooter:


Part 2 to follow.

Sunday, March 13, 2011

p0w3r Drive: Sexy Things that Spin

Believe it or not, but I am halfway through revision 2 of the hubmotor. You ask, "what happened to the first version?"

Simple answer: I got lazy and the aesthetics bothered me. I mean, the motor was 1.625" wide, with only 1" of filleted tread. The 1/4" endcaps looked bulky and unattractive but I couldn't add an edge chamfer because the inner diameter features were already finished. Additionally, I neglected to add sufficient wiggle gap to the magnet ring rings, which made it extremely difficult to get the magnets in place. One formerly excited afternoon transformed into a painfully disappointing sanding feat. Once I had ONE magnet in the spacers, I knew that this was not worth the effort.

So with all these changes to be implemented, I elected to simply not finish version 1. Here is version 2: incredibly badass and sexy.

The wheel is now only 1.25" wide, with a 1.5" hubshaft (more wire space, finally!). I will still be using 1/4" endcaps, but I will turn down the edges and internal features so I can sink the endcaps further into the wheel. This also allows me to rid of the polycarbonate spacers, which served no purpose whatsoever. The mechanical lock nubs were replaced with precision eyeball machining aka I will be relying on a frictional fit from the endcaps and the OD of the magnet ring. This might seem like a bad idea, but It is better than trying to use 4-40's to lock the wheel and any slipping might act as a neat clutch feature. I also added .016" of space to the magnet gap so the magnets just drop in. No file work required.

To make the endcap features, I will be adopting a trick I learned from Shane Colton. First, machining will begin with a waterjet rough circle cut. A severely undersized internal bore and the seven through-bolt holes made. The bore will have a capscrew through it, accompanied with several nuts. These nuts will then be clamped in the chuck of the lathe, and all outer features will be finished. Thereafter, the bolts will be removed, and the bore will be opened with a boring bar. More work certainly, but I expect a much finer product.

Monday, March 7, 2011

InVenture Prize: Final Run!

This week is the finals round of the InVenture Prize!

Not much to say here except...

... COME TO THE EVENT! It will be held at the Ferst Center for the Arts on the Georgia Tech campus, at 6:30. Come early, get better seating.

Here's a Facebook event:!/event.php?eid=167796909938807

I am told it will be streamed live here:

Come please!