Sunday, December 21, 2014

MacroKart - Transient Version 2

Wow, this hasn't been updated in a while. Since the last post on MacroKart, just about everything that was made of wood is now metal, and the thing went through a brief period of complete functionality before I decided things needed to change... but we'll get to that. This summer I had a friend machine a few parts for me since I was at work during shop hours. These parts included the front wheel uprights, the motor mounts, and the brake mounts. I also borrowed a stem from a friend's bike for the handlebars.



3D printed steering column support

The tube was too small so I had to improvise.
 I also changed the throttle to a twist throttle. The pedal required my foot to be uncomfortably extended at full throttle.
Brakes partially complete



Brake assembly after a bit of use

Here's a short video of the brake supports moving. I don't have a video of one with the complete system, unfortunately.

video

At this point, the kart was complete. I rode it up and down the street many many times. I did a few time trials and found that I was going about 17 miles/hour. It was fun, but I wanted MORE. So I bypassed the current shunt on the controllers. this involved removing the loop of wire in the picture below and replacing it with a shorter copper wire. The picture below also shows the capacitor that fell out of one of the controllers when I opened it. I guess it wasn't important. I soldered it back in anyway.


This was a huge success. Big boost in acceleration and about a 30mph top speed. As a result, I was blowing 60A fuses like it was my job. At 33V, that's two '350W' controllers burning through 1kW each. Below are two of three that I blew the first week. After that, I was more careful and did fewer 'full-throttle-from-a-stop' runs. I had 5" wheels - the acceleration was something fierce, I'm tellin ya.


Sadly, all good things must end. Not that my controllers were particularly good, but they both died after about three weeks with the current boost.

Tragic.
On to bigger and better things. I pulled out some 8" pneumatics and put them on the front wheels, yielding a pretty goofy looking setup.


Just for fun, I threw a controller on the left motor and did a few runs up and down the street. I ran into my friend Amir, who took a lovely picture and then went on his way.


Summer also participated in the Imagineering 500 and took both first and last place.


Current status: I have two Kelly KBS36101 controllers and sensors mounted on both motor cans. Rear wheels have been replaced with razor scooter wheels that come with brakes! I need to mount the controllers, wire precharge circuitry for the controllers, attach throttle, sensors, power and finish the brake supports/cabling. I'll also probably redo the steering column and have something a little more robust holding the handlebars in place.




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