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.

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.

It's Made of Wood... Yup.

Earlier in 2013, I started designing a version of Chibikart. Athought I knew I wanted my vehicle to be substantially larger and more comfortable to ride, the final goals for the project were not set in stone at the time and continue to evade me. I'm going to keep this post short because the project is not complete and this is basically just a photo dump with some words in between.

...just like all of my other posts.

The t-slot extrusions, known to me as 80/20 (supposedly 80% of the strength of aluminum at 20% the weight) will serve as the frame for this build and hopefully be adequate for any future four-wheeled vehicles I may feel the need to create in the near future. Special nuts can be inserted into the slots and removed without harming the extrusions, making them ideal for builds that are somewhat fluid in nature when it comes to component placement.

Thanks to the help of Evan Lane, I was able to cut sprockets from 1/8" 6061 Al using the mill in the BU Tinker Lab. <-- BU students, please come do things here so you will enter the job world with real engineering experience!

Test run on foam insulation

We made a fancy jig to hold it.

Number of end mils broken doing this: zero.

Done! Chamfer was added to the edges later, I promise.

The sprocket spacers were cut next.

A few tapped holes later, we've got drive wheels!

There was a small (big) snafu with materials and I was on a deadline for a competition (that I completely misunderstood the criteria for) so I was forced to lasercut all of the pieces that I needed so I could show the judges a thing that looked like a go kart and not a $800 pile of nuts and bolts...and a frame.

Here's a picture of the rolling chassis plus the throttle pedal, which I was overly excited to use, so I put it on as soon as I could.

The front wheels line up - cute.

The brakes were next

Then came the motors and chain.

Special thanks to Abominable Snowman Steering Systems.

A few hours later (in which I did not take pictures) a fully functional kart was completed. Not pictured: the seat, (arrived a few days later) the correct battery, and the sensors+boards (too lazy to put on before aluminum parts get here).

Please note comically large steering wheel. 

Current home:

Anti-grav comes standard in jasontrollers.

For the record, I did ride the wooden kart down the hallways of 44 Cummington for a few feet, but the wooden parts, especially the uprights, were very unhappy and were sagging from the weight of my huge ass. Stay tuned for when aluminum parts are cut and we do garage testing, hopefully by the end of the summer!