Category: Project RazEr

Revamping the electric scooter project.

Snuffles Reloaded: Update 6

chorl1 Comment

It’s shiny. Really shiny.

After another day of furious metal shaving, the structure of the motor is mostly complete. Here are some in-process pics.

Motor side plates before length trimming. They were done step-by-step, one then the other, such that I had to move the asstastic tool holder as little as possible. In retrospect this was probably not the best option, since I did not have the luxury of a tailstock center, so the runout from rechucking a few times is probably obscene, but out of retrospect – oh well.

Test fitting a side plate before finishing the holes.

The internals.

Putting the stator together. No, that’s not the final winding. The wire coils are there to hold the individual laminations in-line while I pressed the whole thing onto the mount and while the epoxy hardened.

Threading the holes in the ring. Here’s Critical Design Flaw #1 (you knew it was coming somewhere!). The wall of the ring is too thin for anything other than, say, 2-56 screws. However, the waterjet made the holes bigger than 2-56 clearance-size. Oops. The next option was #3 screws, which are stupid and rarely used. Then #4, which was just on the edge of bursting through the walls of the ring. I risked it anyway, and things turned out okay.

Hey, the internal ferrous magnet ring. This was actually a rolled strip of 1/32″ steel. This is Critical Design Flaw #1.5, because in retrospect it would have been much better and more effective to make the whole ring from a piece of steel. I wouldn’t have to worry about the ring bursting out and implanting itself in my face, and the magnetic flux would have a better path to travel through. The bolt holes wouldn’t be so close to the edge, and the whole thing would be stiffer anyway.

The precarious seam that somehow holds everything together.

Test installation of the guts. Hey, it seems to be working out!

Actually, it doesn’t. The tolerances and machining imperfections disagree with eachother. Normally, this wouldn’t be that much of an issue, but inside the motor, the airgap between the stator and the magnets is tiny by design. Throw in a dubious lathe with no centers, repeated rechucking, transferring work between different machines, and my awesome skillz, and the magnets don’t fit in. A bit of sanding made things slide in, but it’s inconsistent over the course of one revolution.

There’s alot of improvements that could be made before I continue, such as redoing the can out of steel. Everything else seems to be fine – it rolls smoothly and there is indeed clearance for wiring and windings.

I could redo it, or I could hire it out to a machine shop to take my inconsistencies completely out of it. Although it’s fun to DIY, some times you just want things to work.

It’s finals season, so I have other priorities (like TB4.5-SP1!) to worry about before continuing on this. There’s nothing that prevents it from working conceptually, just manufacturing.

So that probably means SR is going to be on hold for a little while. But it’s still REALLY SHINY!

Snuffles Reloaded: Update 5

chorl

The calm before the storm has arrived. About a week from now, I’ll probably hole myself up in my room and prepare to attack four final exams in four consecutive days. If I survive, I’ll post.

Anyway, tonight was “chill night” after the rush by professors to get the last bits of work and final-exams-before-final-exams in. By chilling, I mean heading to MITERS and, after collecting as much balls as I could, hop on the lathe and work more on the wheelmotor.

The MITERS lathe is probably older than the cumulative ages of any randomly-selected 3 or 4 people in the room at any one time. It’s a medium-sized “South Bend” model, but is probably the single largest chunk of cast iron I have ever personally messed with.

 

After I got the hang of it, it’s actually a great machine. The tool selection is lacking, but I intend to raise the proposition of purchasing some tool bits and tool blanks.

 

There’s one thing I don’t like about it. It uses a “lantern” style toolpost that seems to have 8 degrees of freedom and can jiggle in any direction except the one you want. A forged tool holder sits on a weird-ass banana thing which sits in a shallow bowl. You have to hold down the bowl, the banana, and the tool holder, then tighten down the clamping screw. At once. Up hill, both ways, in the snow. It is evil. Then the end of the tool holder is a complete clusterfuck on its own, since that clamp screw likes to drag everything with it.

 

I ended up having to tighten everything down out of whack and then use a mallet to bash things into alignment.

 

Anyways, stuff turned out well.

 

The finished stator mount doohickey, with a bearing. Even with my eyeballing, newbie toolgrinding, and random bashing of the tool setup, it turned out well – most dimensions are within .005, which is just fine for starters.

Since I did not intend to disassemble this ever again, I press-fitted the shaft into the stator mount using an interference fit of about .01 inches. Three times what you are supposed to use. I stuck it in the biggest milling vise there was and cranked it with the biggest wrench I could find.

 

If this comes apart, I probably have also.

 

On a related note, BATTERIES! Here’s two lithium polymer packs I snagged off EBay. Each pack is 11.1v, 3900mAh. Downside? They were 10C. That’s what I get for going “ooh, cheap” – even though my application doesn’t call for military-grade batteries, I still need the newer 20-25C packs for the low-end acceleration.

 

Since 40 amps is unlikely to move even my ass around, I will probably save these packs for Test Bot 4.5 Media Center Edition Service Pack 1, under final planning for the 2008 competition season.