Sunday, August 4, 2013


9 weeks have past and we're leaving US next week, awhhhh......
So we managed to finish everything, I did the electrical system and now the one thing I hate most in the world is the hall effect sensor. I would never go for a brushless motor next time. It will just save us so much time in soldering all the electronics stuff. Anyway, the first sensor I did was totally screwed up and two out of three wan't working, so the motor speed was very slow. And I glued guned everything so I needed to do everything all over again T T. So I spent 2-3 hours on the new hall effect sensor to make it perfect and it worked perfectly!!!! The motor was spinning real fast, so fast that the whole body of the kart was suffering from a serious vibration.

The video of the motor spinning could be seen here. And I didn't press the throttle all the way down, so that's only 1/2 of the maximum power we could get. 

One thing we worked on a lot was the alignment of the chain, if we don't align the two sprockets properly, the chain will just fall out as the motor spins. And also the mounting for the motor because of the severe vibration and also the secure the small sprocket so it won't fall off as the motor was spinning. We didn't realize all these things until the motor started spinning real fast and all problems come out. So we needed to make a lot of adjustments along the way and finally we managed to make it work and made a perfect alignment and a good tension for out chain, as you can see in the above picture. Another good trick to see whether your sprockets are aligned is to spin the wheel freely and see if the teeth of the sprockets fall in the middle of the chain. 

So we passed all the inspections. The final race day came but a lot of unexpected problems popped up and we were fixing them along the way. Our first run, the throttle suddenly doesn't work. But we took the seat out and put it back on, it worked again.... Anyway, so we went for another run, and the kart stopped before the fist turn... Turns out to be a battery problem, but that was weird cause we charged our battery overnight and the voltage was ok. So we had to charge it again. But our charger got spoiled and when it hits the limit of the battery, the charger didn't stop and just kept pushing in power....So we blew two battery fuses.... So we replaced the fuse and everything worked fine! I double checked all the wiring and made sure there would be no open circuit.... We were good  to go, BUT!!!!! When jiawei went through half of the first lap, we were stopped by Charles and it turns out we never pumped our rear wheel!!!! NOOOOOOO!!!! And the rear wheel came as an assembly with the sprockets and everything, and the opening to pump air in was slanted in an angle that was so sharp that it looked like it was impossible to pump without taking everything out!!! And with a not fully pumped wheel, the mass of the human body would just deform the wheel and it will just spoil the motor and controller.... So we took it to the bike shop down at IDC but their compressor wouldn't fit the angle either. We then decided to really take everything out and pump it. But then our lovely classmate Xinhui MEOW~ gave us this magical air pump and we managed to find a way to push air inside!!! So everything was fine and we were on our way back to the race place, which is a nearby mit parking lot. BUT !!! Jiawei bumped into the wall as he drove out of IDC and then the chain came out!!! So we needed to loosen everything and put the chain back on. But when we finished that, the rest came back and the race was finished. 

I know I know that was sad and we never got a timing for an entire lap. But it was because that we finished everything quite late so we didn't have much time to test and the problems didn't show until the real race came :p....

But I'm still very proud of our kart and I want to drive it around now!!!!Though one thing we could improve is the steering, cause we're using the free aluminum bearing and it's the same material as the steering rod so there was a lot of friction going on. We should have bought some bronze bearings which were quite cheap actually. And the horizontal rod could be longer if we had enough money so it's easier to control. 

A photo of me with all the wirings I did. It finally worked I was so happy!!!!
More videos to come!!!!

Budget overview:

Item Number Model Budget:500
motor  1 turnigy aerodrive 6374-149 76.53
controller  1 KBS48121 149
battery  1 A123 75
rear wheel assembly 1 200x50 Rear Wheel Assembly for Chain Drive Razor E200 (Versions 5-27) 25.99
front wheel 1 200x50 (8"x2") Front Wheel Assembly for Razor E150 23.99
Pedal/Sensor 1 Thumb Throttle with 48 Volt Power Meter 17.99
Ball Joint Linkage Shielded, Steel, 1/4"-28 4 6058K25 11.76
Alloy Steel Threaded Rod Plain, 1/4"-28 1 92580A107 (3ft) 4.78
Aluminum 3/4" steering shaft 1 9056K693 (no use) 7.39
screw 1 92196A636 5.22
Brake lever 1 15.99
Switch (small) 1 3.99
Switch (big) 1 hella 13.29
1/2 aluminum tube (vertical) 1 1658T45 share Andrew (4 ft) 3.5
7/8 aluminum tube (horizontal) 1 9056K723 (1 ft) 7.39
brake cable  1 from charles  5.95
shaft collar 6 6436K14 19.8
bearing  4 6383K16 17.64
nuts 1 91845A031 (free!) 0

Now as I look back, I think about the first night I came to IDC and after the buffet, I saw all those motors, controllers and stuff, and I had not a single clue of what that was all about. But now I just can't believe we built this stuff. Two people with absolutely no clue of what all these things are about (like you need to pump your wheel :p). I still remember myself holding this turnigy motor and asked our TA Justin: what is it? HAHA.....

Everything is machinable. Famous quote of Charles! Thanks for being strict, now I feel more independent and I can actually do things on my own!!!! 

Drag race back at SUTD????

Oh yes, I love MIT :3 Let's bring this culture back to SUTD!!!!