Category: Project RazEr

Revamping the electric scooter project.

Snuffles Reloaded: Update n(n-1)!/k^n

chorl

I forgot which update I’m on again, so pick a value of n and k of your liking which evaluates to the previous update + 1.

Finally got a chance to actually work on the wheelmotor… the days so far have been absorbed by the abrasive waterjet cutter at the Media Lab, among other things. I should be able to get some more work done soon.

Remember the aluminum biscuits I got a while back? Shouldn’t have gotten them supersize. The side plates are .393″ thick at the maximum and I got .75″ slices of aluminum. This meant I had to turn down almost half the length of each disc, which was sketchy enough considering the lathe’s limited spindle speed and feed options.  Worse, I still haven’t figured out how to activate the power feed for the cross slide, so it was hand cranking all the way…

I dug up the reversed jaws for the chuck in order to hold the 4 inch piece. This first facing cut was just slamming one bandsaw-finish side onto the chuck, since I need at least one flat, round surface to start.

The piece was then flipped over and spaced with milling parallels shoved between the chuck and the flat face. This gave me some reasonable accuracy and trueness despite the different setups (and the very frighteningly loose chuck jaws).

And violin, three trimmed biscuits. They’re both .393″ thick with a nonplanarity between the faces of at most .002 across the diameter, which is pretty good I think for ghettocentering. One piece was faced too far because of some strange force of machine nature which causes the tool to not cut until I crank the handle past my original target dimension, at which point it removes all material up to the new dimension at once. Oops.  The short piece is .385″, and has been designated as the practice piece.

Two pictures don’t quite convey the passage of time, but these three discs took two hours.

Because you can’t machine an outer diameter while holding onto the same outer diameter, I had to make my first metapart, a part which helps make parts. Dale clued me in on using a mandrel, or custom spindle mount, for machining the other features of each side plate.

This doohickey is made from 1″ aluminum round and has a .875″ section which the discs mount on. A large custom washer (not shown) fits the bore of the discs from the other side. The whole thing is retained by a 3/8-24 bolt. Like a giant inverse prop adaptor, almost.  Each disc has a center bore of .875 (or close enough to it) to mount snugly on the mandrel. The were, of course, made using the not-boring-bar.

Test cut! I threw the short disc onto the mandrel and tested everything. Seems to work great, and the runout is minimal once the mandrel itself is secured and centered. I called it a night there, as it was somehow 4AM.

Now that the raw outer-dimension parts for the side plates have been made, I can take another evening and actually make the final parts. More pics to come! Everything is actually round this time! Holy Robot Jesus!

I can has shenanigans?

chorl

So I fell back into a phase of “Oops, didn’t bring the camera” syndrome, but here’s some of the goings-on for the past two days. I’m pretty sure that my left arm is going to fall off on its own and beat me to death just by itself soon. There’s been alot more threading and tapping. It builds character….and muscle, since it allows me to try to equalize the arms a bit. Being right handed, my right arm has historically been a bit stronger than my left.

Anyways, onto pictures.

More progress on the steering arm, now with 99% more gears! They are all some ungodly large pitch (10? 8? Module 3?) and 3/8″ in thickness, and all waterjet-cut.

I have watched the pile of 50-pound bags of abrasive sitting outside the waterjet room slowly get smaller over the past week. I wonder how much the machine weighs with a full tank of water and sand?

A closeup of the geartrain. Yes, I know, two of the gears don’t touch and two more have very little contact. This was a design error that was corrected by recutting those gears.

The total ratio is around 40:1.

Random closeup through the Lexan mount. I suggested running the gear teeth in with polishing compound to smooth out the sandblast-like finish of the waterjet, which probably pitched the efficiency out the window. They haven’t taken me up on it….yet.

Switching gears a little bit, I did some more cutting and subsequent assembly work on this parking stand for the scooter. It does two things – allow the front wheel to lock against something for leverage while folding, and also allows the vehicle to rest vertically, leaning on the Wolverine-claw-like things (Which will actually have a plate mounted on top). It’s missing a few parts, but that will be addressed soon.
The big difference between this piece and the steering arm is that this has right angles and hence was easier to slam on the drill press and drill quickly and accurately.

Hmm, so all this fabbing has distracted me a bit from wheelmotor work. My magnets and bearings both arrived today.

Interesting thing about these bearings is that they’re tiny. 15mm bore, same as the previous, but only 24mm diameter and 5mm width. I’m slightly concerned about loading and bearing life. Whatever, I suppose. I should be able to get some work on the side plates done tomorow (today? what week is it!?.

28 magnets test loaded and…. HEY! What’s that giant gap?! It’s supposed to be a perfect fit!

Oh well. Nothing some index cards can’t solve. Did you know that a full circle of magnets like this can actually be detrimental to efficiency becuase of increased hysteresis losses in the core?

Stay tuned for the next episode. Meanwhile, bot on.