Go-Kart Revival: Part I

So about that go-kart I was building...

Continuing where I left off, I needed to wire up the motor controllers with the motor, throttle, and mains (power). It was pretty simple; just read the wiring diagram in the motor controller manual and connect wires where appropriate.

My work layout on the EE bench is pretty simple. I have a 30V power supply powering the motor controller (the silver brick), which is connected to the three phases of the motor, hall sensor, and the throttle (not pictured here). The red multimeter is for testing the various voltages on the motor controller wires to make sure none of the wires are broken. One of my friends had this bug, and it took her a while to figure out!

I also have some helping hands, which are the silver arms holding wires over the table. The throttle is near the bottom right of the picture, below the blue strippers. The super awesome soldering station is a Weller industrial soldering station.

It took a while for me to figure out that both power inputs to the motor controller need to be 18+V, something the manual doesn't say. Thanks Charles!

There are two red LEDs (well one has a red housing and the other has a clear housing) amid the wires which indicate the motor controller status. Here, the clear LED should be solid red and the red LED off.

Here's a photo of hall sensor jiggling, with a great writeup by Charles. The goal is to figure out which permutation of phases I should connect the motor to the controller. If the motor and controller are not matched properly, then the motor will not spin. There are 3! = 6 permutations, but luckily I found the right pairing on my second try.

However, one motor has to spin CW and the other CCW since the motors are mounted opposing each other. To make the motor spin the other way, you have to cyclically shift the three phases. There are only two distinct shifts, and I was pretty happy that I got the motor spinning on my second try.

There's more to come! What remains is hooking up the motors to the chassis, installing the chains, and refurbishing the rest of the vehicle as necessary to get it running!

KawaiiKart: Mechanical Assembly DONE!

Alright. This is the third-to-last post that ends the KawaiiKart saga! I am extremely naive, at least considering my current trajectory. Actually the aforementioned claim seems fine, since all I have left is getting the EV section to run, then the gas engine to run, and finally coordinating the two!! I will detail the assembly of most of the kart, from most of the steering assembly to mounting the engine.

MLK weekend

Remember from last time that I messed up the steering knuckles? I got a chance to re-waterjet my parts (on campus! no week-long delays!) with a nice Omax waterjet. Unfortunately, there were no 0.25" thick aluminum sheets that were large enough, so I was going to make twice the number of parts on a 0.125" thick sheet.

It's a $400,000 printer that takes sheets of aluminum!

At first I waterjetted on quality 4 (second best), but the waterjet's software said that it would take an hour as well as 50lb of abrasive. I decided to let it run for a while, but I realized that my routing did not include small tabs on the parts (to prevent the parts from falling into the waterjet tub), which the second part did. At this point, I stopped the waterjet, added tabs to my parts, and reran at quality 3. The run time and abrasive consumption were much more reasonable, clocking in at 14 minutes total and 7 lb of sand.

The new knuckles turned out to be perfect. At this point, I was supposed to have a rolling frame, but by virtue of sloppiness, I forgot to order 3/8"-24 nuts, some steering column lock collars, as well as more L joints for the tie-rod steering.

Better waterjetted steering knuckle: the nut fits!! (of course I winged it)

Vise-ing bearings into steering mounts.

The legendary T-nut.

Assembled frame!

My temporary parking space at MITERS.

Charlesg welded my unidirectional flywheel tight.

Testing the fit of the wheel axles.

Taking a break to track ChibiKart in the snow. This is the result.

Mounting the steering knuckles.

An engine and wheels appeared!

Servicing engine mount with a makeshift carjack.

Week before Techfair

This is the week when the EVERYTHING happens. Literally. It's the last week of my externship, Battlecode quals + finalists' dinner + final tournament, and KawaiiKart cram week. Basically all the time after work was dedicated to either writing code for Battlecode or working on the go-kart. During this week, I went from chassis and parts to a mostly working kart. Picture dump below:

Scraping self against a piece of aluminum or Nancy's hexapod.

Using vise as holder to insert one notch into motor mount.

Vising entire motor mount into steering knuckle.

Chibi motors!

Mounting motors onto motor mount.

The bore of the pinion gear is slightly too large, so we'll pad it with Coke can.

Too lazy to file deeper notch in motor shaft.

Adjusting pinion gear on motor shaft.

Motor on wheel!

I fail at ordering parts again.

It's a masterlink!

Cutting fluid does wonders.

The chain is on! Now to tighten it a bit more.

Steering column with tie rods!

The MITERS parking garage.

Side profile.

My hands turn black after a day's worth of hard work.

BigLathe!

Motor controller (it's a Kelly controller).

Revised steering column end mount.

That steering wheel was not intended for this vehicle.

Soldering the Hall sensors onto those boards was really annoying!!!

Last but not least

The correct way to listen to K-pop is to turn the bass all the way up, and then knock the treble down a few notches to compensate.

Up next: electronics and a working EV!

KawaiiKart: December/Early IAP Update

I spent most of yesterday night working on KawaiiKart. In fact, I promised myself not to leave MITERS until the rear wheel was on the chassis. This is more complicated than it sounds because I screwed up assembling the rear of the kart twice!

My first problem was that the distance between the aluminum extrusions was too wide. Turns out you must take into every little dimension when CADding parts. Since I normally work with things that have infinite tolerance (code/math)...go figure -_- The solution wasn't too tricky; I made two plates that went on top of the extrusions that connected two more extrusions on the respective insides.

This solution introduces more torsional flex, but to what extent is unknown so far. It seems to pass a rudimentary twist and sit test, though.

The second issue dealt with how my rear wheel was installed. Since I had the wheel essentially slide into the space between the aluminum extrusions, I couldn't tighten the bolts if I first installed the extrusions onto the chassis.

Here's to hoping I tightened the bolts enough such that the wheel won't fall off during operation!

I also had a slew of smaller issues, like incorrectly measuring dimensions and not accounting for dimensions and the like.

Because the axle diameter isn't 5/8"; it's really 10mm!

Because T-nuts have finite size

Because axles have finite length and need to be secured...somehow.

That's all for now! Hopefully I can have a rolling frame (with motors!!) by the end of MLK.

KawaiiKart Chassis Assembled!

Or part of. If I fail my finals, this would be the reason.

It only took about three hours to cut the 80/20 into their requisite lengths (while screwing up the lengths for the main chassis because I don't know how to use a ruler -__-) and screw them together. Hopefully I get more done after finals.

12 Days of Christmas

Sung to the melody of Twelve Days of Christmas

On the first day of Christmas
My true love sent to me
a OneTesla coil

On the second day of Christmas
My true love sent to me
Two PSUs
and a OneTesla coil

On the third day of Chirstmas
My true love sent to me
Three mannequins
Two PSUs
and a OneTesla coil

On the fourth day of Christmas
My true love sent to me
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the fifth day of Christmas
My true love sent to me
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the sixth day of Christmas
My true love sent to me
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the seventh day of Christmas
My true love sent to me
Seven ballcopters
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the eighth day of Christmas
My true love sent to me
Eight processors
Seven ballcopters
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the ninth day of Christmas
My true love sent to me
Nine monitors
Eight processors
Seven ballcopters
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the tenth day of Christmas
My true love sent to me
Ten SSDs
Nine monitors
Eight processors
Seven ballcopters
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the eleventh day of Christmas
My true love sent to me
Eleven bugs to fix
Ten SSDs
Nine monitors
Eight processors
Seven ballcopters
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

On the twelfth day of Christmas
My true love sent to me
Twelve sticks of RAM
Eleven bugs to fix
Ten SSDs
Nine monitors
Eight processors
Seven ballcopters
Six hamburgers
Five KawaiiKarts
Four GPUs
Three mannequins
Two PSUs
and a OneTesla coil

Steering: Conquered

I finally fixed the steering on KawaiiKart, which meant securing one of the two remaining degrees of freedom so that the steering column won't wobble while trying to steer. Here's the updated CAD:

I did the entire CAD on my MacBook Pro Core Duo (yes, one of the first MacBook Pros!) 2.0GHz with 2GiB RAM and a now wimpy ATI Mobility X1600 driving a custom 1920x1200 panel. I'm very impressed by how old hardware works. Then again a 100-part assembly isn't very much at all.

In other news, I got a $500 grant from Techfair to partially fund building Kawaii! I estimate the build will run upwards of $1.2k, since waterjet parts are expensive (~$400), but the journey and the end product will be well worth it. Stay tuned!

KawaiiKart Mega Update

Quite a bit of time passed since my last update and quite a byte has changed! (well, maybe not 8x as much, but you get the idea.) KawaiiKart is almost finished designed! Here's the latest model:

The box behind the seat is the 35cc engine. I also have to install the steering assembly at some point and decide what to do with the extra lengths of aluminum on the outer frame of the chassis.

The steering is still a little sketchy (I had to remove some (important) constraints to make Autodesk happy), but it looks fine! I still have to work out how the steering column works; my plane projection for the loft on the steering column is very sketchy. Turns out the angle of the steering column with respect to the chassis is 35 degrees, not 45. No big deal, band saws are my friends.

I also have some design updates. I'm ditching the hubmotors because time to production is way too long compared to using off-the-shelf components. I am willing to manufacture battery packs though; a 16-cell pack isn't very hard.

If you're interested in following my progress, check back every so often; I hope to make lots of progress before the new year! In fact, my BOM is almost done!

Start of Something New

I've always wanted a go-kart since sixth or seventh grade. Fortunately, after years of hard work and meeting the right people (hi Charles and Shane!), I have the skills and support to build one of these. The target goals are as follows:

• Weigh less than 25kg
• Top speed of >30mph

It's going to be an AWD hybrid. The rear wheel will be driven by a Honda GX35 and the front wheels will be driven by two custom hubmotors and controlled by a custom motor controller.

This build will be largely based off the Democratic People's Republic of Chibikart and its older brother Chibikart, whose comprehensive build instructions are here. It will be an exercise of implementing a small asymmetric hybrid (similar to the Lexus RX hybrid with AWD).

And yes, the title is a High School Musical reference.