Tag: electric scooter

Media Lab Shenanigans continued

chorl

Even though neither the omnidirectional 4WD vehicle nor the Roboscooter are my own projects, per se, I still feel like taking a bunch of pictures and writing about their development as Media Lab Sponsors Week approaches, especially since I’m pretty heavily involved in the R&D.

And of course I feel like showing off all the shiny toys. Here’s some stuff from today.

40AH large-scale rectangular LiFePO4 cells. Yes, this is one cell. It’s roughly the size of a construction brick, but a little flatter. 3.2 volts per cell. These are from Thunder Sky, which is a big enough name in the R/C hobby world to make me consider them legit.

The 4-wheeler will use one 48v(15S) pack for drive and one 24V (7S? 8S? 7.5S?!) pack for steering and the rest of the electrical system.

Packs under construction. The shipment of cells came with a bucket of formed copper battery bars that mounted to the terminals with screws. Handy, since nobody had to wield a kilowatt soldering iron.

The chassis hasn’t changed much from last week, but that will not be the case soon.

Some waterjet-cut aluminum plate that will be eventually assembled into the steering arms and motor mounts. I love this method of construction and will probably be using it more in my own stuff – that is, 2D plates cut with slots and keys that assemble puzzle-like into a 3D shape, which is then retained by screws. With a 5-axis nozzle, I’m sure we could make even weirder shapes.

Here’s a shot of the (mostly) functional scooter in folded form. No, that’s not me fiddling with it.

When folded, the scooter is strangely aesthetic in a way, like someone in various yoga positions. It has a strangely organic yet still very mechanical look. But now I’m getting too artsy. The parking stand is only a mockup at the moment, as the above picture shows. A hardcøre metal stand will be made for the presentations.

There’s been both mechanical and electrical work on the thing done, since some parts weren’t made to spec or weren’t there at all (Hey, how much moving does it need to do at a show? None!). I’ve been working on a closed-loop controller for the folding process as well as doing some fabrication work.

Like this. This is the main seat folding control link. The 4-bar linkage which folds the seat in sync with the chassis was made with some links too long (I think it was a revision control issue). Fortunately, they were too long, becuase they could be shortened. The process was to slit each link, mill a bit off each end, then recombine them with a “connector block”. The links are C-channel in profile, so making this block was simple.

I also discovered that having the depth stop on the drill press work with your countersink is a wonderful thing. Those are the best countersunk holes I’ve made to date.

So, what on earth am I working on anyways? Well, sort of both projects at once. I’ve been rather general purpose, building whatever needs building, but focusing somewhat on the electronics. This is great, since I get the best of all the worlds involved, but get to work on a field which I don’t have as much experience in.

The whole of spring break will probably be filled with build pics, so stay tuned!

Wheelmotor Beta 2 Update 2

chorl

In another episode of “Hmm, what is Charles building”, we have…

Gee, some aluminum rounds and a large section of steel tubing.

Hmm, it really makes you wonder, doesn’t it?

I opted to skip the Intro to über-basic EE that today’s 6.01 lecture was covering in order to haunt the Central Machine Shop for metal. The guys there are awesome, and cut me off a few pieces of aluminum round and this Seriously Hardcøre steel tubing. They also remember the MIT Battlebots team.
No, this is not a prototype weapon module, despite the temptations, but rather the ingredients to the wheelmotor. Obviously the motor doesn’t require such a Seriously Hardcøre outer shell, but it was the only thickness of tubing (Can something this thick be called tubing any more?) they had in the diameter I needed. At first I wanted to get the aluminum in one large chunk, but after some discussion, they cut it into slices since 1) They have a giant bandsaw and I don’t and 2) It was on the house.

The tubing, though, is likely Hardcøre-er  than the MITERS lathe can handle, even with the jaws reversed. I will definitely have to get into one of the main student shops with larger machines to turn it down.

In the mean time, I’ll work on winding the sucker. Here’s pics from a few days ago.

  Testing windings. On the right is 30 turns of single-strand #22 wire. On the left is 30 turns of double-strand #22 wire for an effective winding gauge of #19. I haven’t settled on a particular winding yet. That will come after some math, testing, and stretching the R/C hobby builder rules of thumb to the edge of existence. I will probably end up winding this motor alot milder than the last, and run high voltage.

One thing that attracts me to keeping the 30T of dual-strand #22 is that everything works out perfectly in terms of fit. I’m left with a little more than .025 clearance on both sides with the winding ends accounted for. That means I can wind the motor, then stuff the whole thing in a vise and squish down the windings some and not have to worry about wire clearance.

I may be able to stuff on more, but we’ll see.

Stay tuned! Spring break is approaching, which means I get to go party my head off somewhere in Florida lock myself in the shop and not come out until this sucker’s done!