Tuesday, August 16, 2011

Busy on Holiday

I'm currently on my two weeks holiday between work and institute but I'm kept relatively busy by upcoming events. Dragon Con and the Georgia Tech Mini Maker Faire are both coming up, which means I have about 5-6 things I need to get done.

Robots:
Running the bots at PA Bot Blast was a good way to test their metal against some real north east powerhouses but now I am left with no satisfactory running robots. Dragon Con doesn't run the 150 gram classes, but I still like to make a showing with an ant, beetle, and maybe a macro-class robot this year. I should have enough extra frame parts to revive Cake (I want to rebuild!) but the drums are just so fucked up I don't see too much in point in it. I would like to bring something different from DDT. The main idea is to not spend any extra money so we'll see how that turns out.

Costume(?):
If I go to any of these conventions, I like to put a little extra into it by dressing as something and then saving it for Halloween. As awesome as Tony Stark is, I DO NOT want to recycle a costume past a year. Hell, multiple conventions was pushing it. Right now I am looking into something Matrixy but those long coats are really damn expensive...

On to the interesting parts...

Scooter:
I bought this. Do I really need to state my intentions?


Safety Razor v1.1 is still in deployment, but I am putting foot down... on something other than concrete for braking. There are a few minor inconveniences in the current iteration that I am wanting to address in a new revision.
  • Braking - my left foot is unacceptable, and I just bought a pair of Nike shoes
  • Heft- At 13-15 pounds, the scooter weighs on the heavier side of objects. The motor alone weighs about 6 pounds, and the frame is unpocketed aluminum. All aspects of it (except the handlebars) are overspec'd.
  • Waterproof- it is not, and wetness has hurt it before
  • Switches - periodic replacement of switches due to destructive arcing is unacceptable. A precharge circuit is needed, or a high amperage switching method.
  • Longevity- last longer (she said that)
  • Smoother Rides- make it suck less when I hit cracks in the sidewalk
These are very realistic goals that all begin with the wheelmotor.

Weren't you building one already? Is it done yet? The answers to those questions are "yes" and "no". Since it isn't done yet, the logical thing would be to design another one.



In reality, I have an issue with leaving proper amounts of space for wires. I wish they were of infinitesimal thickness. Besides, that version was fitted to a 5" wheel, and as my calculations show, I can get a more efficient package from a smaller diameter but wider wheel (assuming stator also follows).


The new wheelmotor plan has lots of space for wires to route (over 1/4" of room) and a beefy 3/4" shaft for the passage of wires. The stator comes from a Turnigy motor, has a diameter of 52mm, and a length of 30mm. The stator will be wound dLRK with ~25 winds per tooth. Each magnetic pole is composed of two N52 neodymium bar magnets. All of this will be captive in a 4" rubber wheel of 40A durometer. Air gap is currently 0.6mm ideal.



To make this motor comparable to the 400W Kollemorgen , I will be routing sensors through the motor. A tad bit of trial/error is involved because I am planning on using a 150A RC car esc to drive it. Thanks to Charles and Shane, I have the pinouts of the sensor cables but I'll still be playing the mix 'n match game to determine the "A", "B", "C" motor terminals.


As a result of the motor swap, the entire frame gets a redux. The frame rails are still Aluminum but only 19" long now, and 3/16" thick instead of 1/4" before. In fact, all 1/4" plate is changed to 3/16". The top and bottom plates are still 1/8" Al, but there is no longer a garolite fancy cover plate. Instead, I am going to try engraving on some skater's grip tape and stick that to the aluminum. Also notice there are no T-nuts. All holes will be mill drilled and a silicon caulking will be applied to the inside corners to help with waterproofing.


Why don't I need the garolite cover anymore? All charge plugs are now externally accessible. A simple cover will go on top of those to prevent crud from getting inside.

What on earth is that monstrous black tumor protruding from the back? That is the model of the 150A esc. I don't actually have it on my persons yet.

Meanwhile, the battery was upgraded to a 6s1p 5000mAh lipoly pack. Super longpak!


A slight modification to the front forks to make it look less... awkward. This is the true advantage of the Razor A2 or A3 scooters.

For now, this will sit under the Safety Razor tag, but I am open to new names. Razor Wind?

2 comments:

  1. Hey,

    Fantastic blog. Do you have an email I can contact you on? Have a few questions. My email is: rgibson@farnell.com

    Thanks!

    Ryan

    ReplyDelete