Tuesday, March 31, 2009

Behold the boxy goodness!

After a lot of thought and consideration, I decided to go with plastic for the battery boxes. They are made from 1/4" thick polypropylene plastic, welded at the seams. They will not corrode and will contain any acid spill that may come their way. Plus they are nice and lite.

There's room for 11 group 31 batteries in them there boxes. I'll be using 12 volt Crown deep cycle batteries, for a total of 132 VDC and approximately 18.5 KW of juice. Of course I'm going to have to build a steel support structure to hold them in place, and devise a way to hold the batteries firmly inside the boxes so pot holes and the speed humps in my neighborhood don't send them flying. Details.

Next up, I have to finish cutting the fuel tank out. I've been putting it off or working on other things because it is teh suck! But it has to be done.

Wednesday, March 11, 2009

Instrument Cluster

One of the things that truly does worry me about all this is how to make all the instruments work. The Zilla controller will run the tachometer, IF I can isolate the leads to it, figure out what each one is and plug them in to the hairball correctly. The Zilla can also use the "Check Engine"light (or any other unused light for that matter) to warn of system faults, again IF I can figure it out.

The tough one is going to be the speedometer. The sensor for the speedo is in the trans axle. It sends a signal to the ECU (Electronic Control Unit, the car's computer) which in turn sends a signal to the instrument cluster. Well, the ECU is effectively dead. At least I think so. It's still there, but of the 6 wiring harnesses that were plugged into it, all but one is gone. My hopes that the one remaining cluster of wires contains both the lead in and out for the speedo, AND the unit will work as designed with no input from an engine are slim.

I may end up having to build something that processes and sends the correct signal to the instrument. Stop laughing! Yeah, I'm not so sure I can do it either. I may be left with no other choice than to use an after market speedo. I think you can see why this part worries me.

Front Battery Boxes

It occurred to me that I'd better start solving any problems with fitting batteries in the front end. I spent some time building some cardboard trays that would hold the cardboard batteries I built. All the cardboard mock ups that I made are carefully built to match the actual size of the batteries I intend to use. I'm planning on using 11 Crown 31D36 12V batteries, for a total of 132 VDC and approximately 18.5 KWh. Originally I wanted to use 14, but there simply wasn't anyway to accomplish that.

As you can see, I'll be able to fit 7 batteries up front quite easily. Under the front battery box is plenty of room for the accessories I'm going to use, A/C system and power steering pump and vacuum pump for the brakes. The three batteries back by the firewall will end up being about the same height as the two directly in front, I just couldn't find anything to hold them up there. Eventually, there will be some pretty substantial bracing to hold them up.

I haven't decided what to make the actual battery boxes, or trays out of. Fiberglass is out, not enough room. As I see it, I could use steel or carbon fiber. They measure up like this. Steel is cheap, but heavy. Carbon fiber is light, but decidedly not cheap. I have a few weeks to decide.

Tuesday, March 3, 2009

My God, Man! What have you done?!

BMW lovers, you may want to look away for a moment. You've been warned.

I prepared the trunk for some serious brutality this morning. Measured out the space where the battery box will go, got out an angle grinder with my best diamond bit and went at it.

It went surprisingly well. Lots of sparks, a little smoke and no blood. Sounds like a near perfect date. I'm considering using carbon fiber to make the battery box that will fit in that hole. Of course it's lighter than steel but also many times more expensive. But how cool would that be?!

Here you can see a mock up of how the batteries will fit in the space. Each of the boxes is slightly bigger than one of the batteries I intend to use. See, I've conveniently drawn battery terminals on one of the boxes to show it's supposed to be a battery. Isn't that clever? No... it really isn't is it. Lets move on.

Once I build the box to hold them and mount it in place, the tops of the batteries will be just below the surface of the trunk's floor, and yet several inches above the bottom of the bumper and the rest of the under-carriage from underneath.

Monday, March 2, 2009

Brown Disappoints

Early last week the transmission arrived at the shop that I've hired to build the adaptor plate and mounting hub. In spite of the fact that we used the paper from 10 hectares of forest packing it into that box so that it was immobile, UPS managed to inflict a bit of bad. You can see one of the eyelets along the bell housing was broken off. The machinist at the shop said that it would not effect the adaptor plate, so that was good news. I looked at the photo closely and began to think "I don't remember an eyelet in that location." I looked at the service manual and sure enough, I found that it was the location of a locating pin used simply to help you hold the tranny to the motor in the right place as you bolt it on. Sweet! Absolutely no impact. Big sigh of relief.