Wednesday, February 20, 2013

New Bike, New Brakes

After the testing in the hallway and in the alley outside N52, we realized we needed a more reliable bike. The aluminum Geoby bike was a nice bike but it was definitely not designed to handle the loads we were putting on it. We had no issues with it but before anything happened we decided to switch to a steel frame, disc brake bicycle. Luckily Lennon had a Surly Disc Trucker he was willing to let us use for the project.

Joey working on the new frame.

We moved all the electronics onto this new frame and we also replaced the stock brakes with very nice high end Shimano disc brakes with integrated heat sinks. Rango, Lauren and I also decided to revamp the electrical wiring system with better connectors and a better more logical layout.

new controller-motor wiring system

Friday, February 15, 2013

New Suspension Design

During February we underwent a big suspension system redesign. Our previous design used 6 springs, and 12 brackets. It was a very machining intensive design, furthermore it was unconstrained and hysteretic (when the suspension was pushed on, it wouldn't spring back up because of jamming issues due to the high number of joints).

Johnathan and Nick came up with a neat redesign using only two shocks and a pair of hinges. The idea is to emulate what you see on a motorcycle or bicycle rear suspension where you have a combination of a pivot and a spring/shock that absorbs the loads. Nick even designed it so that it would be easily waterjettable with only some slight machining needed.

New suspension design with a fancy FSAE shock.
Notice the heavy duty hinges towards the front.
This new suspension gets us a little step closer to a full system test. We are currently planning a trip to Concord sometime during March to see how our vehicle handles in the real roads of Massachusetts.

Thursday, February 7, 2013

TechFair 2013!

EVT participated in MIT TechFair 2013!

We took our eBike and the pocket bikes! We even teamed up with MITERS and did an EV parade around the building.

Lauren on the eBike!

Sunday, February 3, 2013

Connector Meltdown

We were out testing the eBike today and while starting up we saw some smoke! Immediately we cut power to the bike and stopped. This is what happened:

The connectors melted and shorted each other terribly (thus the smoking), interestingly when the power was off and we were pushing the bike forward we saw some crazy vibrations from the front wheel, this was due to the back EMF of the shorted motor.

The connector failed terribly, these are supposed to withstand 50A but they obviously do not live to the challenge. I phoned the company and they said they had seen this before and blamed it on the connectors that come from the manufacturer, they suggested we switch them with better connectors (which we did). The motor seemed that it undergone no severe damage, we spun it back up and it ran smoothly as before.