MIT Electric Vehicle Team Blog

Tuesday 6-23-09:
I finished up the CAD drawing for the motorcycle battery pack in the morning and we had a battery review meeting in the afternoon to critique and improve the design. Many great suggestions came out of the meeting such as ways to improve the battery cooling, ways to simplify the design, and a way to reduce vibration when the battery is on the bike. We decided that we are not going to use FR4 initially and instead are just going to make the battery enclosures out of only Polycarb. We also decided that we are going to have a double enclosure design so that we can put foam in between the boxes to dampen vibration and so that we can use the outer box as a manifold to pull air through the pack. I will integrate these suggestions back into the design later this week. Mike and I are planning to water jet the casing tomorrow or Thursday. We are also going to water jet the tabs for one of the modules this week.

Wednesday 6-24-09:
Mike has a friend who offered to help us water jet so we cut the battery tabs today. They look very good. In order to cut the nickel, we sandwiched it between two sheets of Aluminum. We test fit the battery tabs onto the batteries and they fit well. We did not have enough time to water jet the polycarb battery enclosure today.

Thursday 6-25-09:
Today, I helped Matt look for a spline shaft for the electric motor. We have an engineering drawing of the shaft so I thought it would be relatively easy to find. I spent several hours calling up junkyards and transmission rebuild shops and did not have any luck. We do not know what transmission has the spline we are looking for so I tried to look up the spline by the number of teeth and the outer diameter. In the afternoon, I drove out to the junkyard that Matt went to last week and talked to them about the shaft we needed. The junkyard was called Nissenbaum's Auto Parts. They were very helpful and interested in our project. I first looked for the spline shaft in a dumpster they had that was full of busted transmissions. Then I looked for the shaft in their stock of good transmissions. I thought I found the shaft we were looking for so I took down the information for the transmission. The guy in charge at Nissenbaum's had a good suggestion that we look for the shaft at a transmission rebuild shop. He recommended New England Transmissions in Alewife. I called them up and made an appointment to come in around 9am on Friday morning.

Fridays 6-25-09:

I took the T early in the morning to New England Transmissions. The guys were very helpful and told me I was welcome to look through their shelves of used transmission parts and see if I can find the shaft I'm looking for. I looked for about 3 hours and finally found the shaft that fit the engineering drawing. I took it back to the shop and it did not fit. It turns out, I had been looking for the wrong size shaft. The CAD drawing showed a shaft with two ends and we had just assumed that the one on the left side of the shaft was the one we were looking for but it turns out the right end was the correct spline. So I drove back out to the shop and looked for another hour and was unable to find the correct spline. When I got back to the shop, I walked over to the central machine shop and they said they do not have the right tooling to make a spline shaft. While I was out, Mike finished water cutting the battery enclosure and he partially assembled it. The clear polycarb casing looks very nice. It makes it very easy to see the tabs so in case a battery internally shorts, we should be able to see if the cell fuse has blown. I spent a couple more hours in the afternoon trying to find a machine shop to cut the spline for us. Over the weekends, I will continue to look for the spline and also work on getting the battery pack ready to assemble when the battery welder comes.