Fabrication

I seem to have successfully moved my inverter to the rear of the car. This will allow me to put a much larger number of cells in the front of the car and improve the weight distribution (I'm currently rear heavy). I found connectors to extend the motor's encoder cable and Ed made one up using some special cable he had left over from a job. I replaced the terminal cover on the inverter with a mounting plate for the new Gigavac GX14 contactors (replacing the large Schaltbau 162 units that wouldn't really fit anywhere), precharge circuit and the EVision shunt. This has a number of drawbacks,

• quite a lot of effort is required to inspect the terminals under the cover
• the positive battery cable connection is partially obscured below the boot opening and is close to the body, working on it is a little scary
• a rear end crash could cause major problems
• I haven't worked out how to form a cover

Pictured is my current test implementation, there are a number of things that need fixing,

• there are some very thin copper bus bars that need to replaced with thicker bars
• the jumpers between the contactors and the inverter are much too thin
• the fuse should be much closer to the battery
• one of the phase cables is completely unsuitable (about 10mm2 total from all three conductors of a household electric oven supply cable (including the oven's on-off switch!)
• the low voltage wires need some tidying up
• putting everything on top of an insulator and standing some insulation between the various components might be a good idea
• I need to make a cover

I did have one mishap while testing. I know you have to keep the loop area small in the phase cables (this is a clever way of saying "keep the phase cables close together"!) and Ed repeated this several times while I was fabricating, but when it came time to actually put it together, well, I forgot. The inverter was most unhappy to have one phase cable go over, one go under and one go around the side (the latter two going out the boot aperture). It refused to run the motor smoothly with no load and then it blew the 30A test fuse! I re-directed the cables to all go over the inverter and through the hole in the front of the boot and everything was smooth and happy. My testing so far is limited by the thin wires in both the battery and motor circuits but I think (and hope) I put enough current through the phase cables to prove it will work. The encoder cable runs down the side of the car while the phase cables run down the middle. Shortly additional battery cables will also run down the middle, hopefully this won't introduce problems.

There is room for another row of cells in front of the two shown, but this row will have to be slightly lower since the front of the car curves down. There is enough height in the middle to put cells above the motor where it protrudes through the plywood, higher than the rest.

It seems improved Weight distribution can be had by putting the inverter in the boot and most of the battery in the front. This does introduce longer motor cable runs which will reduce efficiency but it is looking worth it -- with the inverter up front there isn't much room for cells and it's 70kg lighter on the front axle than when I started. I'll be mocking up the front to see exactly how many cells fit without the inverter before I commit to this move.

I don't have enough room for a proper press brake, and it seems that a shop press brake adapter for my shop press isn't available in New Zealand, but what I have found, is a good way to break your vice. The Vice Brake is sold as being capable of bending 2mm mild steel, and while this might be true for small pieces, you vice will struggle to do a long bend in 2mm.

Enter the vice brake shop press. This works surprisingly well, with the vice brake seemingly very stable and not at all threatening to explode out the side.

Of course, even a small 10 tonne shop press is much more powerful than a vice. I used the back, less visible, end of the die to bend a small piece of steel and didn't supervice it sufficiently. This damaged the die, but it still copes with bending 3mm steel.

The other end of the die is undamaged.

I've now re-installed 30 of the 36 cells in the rear battery box. I added plates at each end of the box to make the walls flat, so it will provide better compression to the cells. This is working better than with no plates (there is a lip at the bottom where the floor of the box overlaps and is spot welded to the sides, but this lip is only 10mm high), but sadly it turns out Auckland is shut in January, and the cutting department is still on holiday. I improvised with 1mm steel (old computer cases turn out to be good for something) and a plasma cutter. Many thanks to Edward for lending me his plasma cutter, it's fantastic, no home is complete without one. I need to reinforce the outside of the battery box, as it bulges a little when you swash the cells in. I realised this only after I'd put three coats of paint on it :-(

Anthony (woody on the AEVA forum) is in Auckland this week and came to have a look at what I'm up to. He was a great help, passing clamps while cutting, sanding the terminals on all the cells and helping me install the cells. He also pointed out many obvious things that I missed (things like you should hammer cells on the edges and the conical plasma cutter torch is conical, but it still has a flat face which you can use to run down the side of a guide and get a straight line).

Sadly the second battery rack was to complex to finish in time for the LCA Open Day and KillaCycle tour so I'm going to have the same 36 cells and 118v or so open circuit that the car had last time it was working.

I've mostly finished the bracket which will hold the front mount (where front is closest to the front of the car if the motor was in a north south configuration, which means it's on the left on this car). The mount is the black round thing hanging below the pipe I welded in earlier, and I've spent the evening grinding the curves on the bracket between it and the pipe. The bracket needs a bit of tidying up I'll be ready to weld it onto the frame.

In unrelated news, the KillaCycle arrived in New Zealand safely, the Tumanako VC motor controller had it's first drive yesterday in the Greenstage electric Saker (first time that has moved under electric power too!) and I have about a week left to put this car together before I'm leaving for LCA2010 in Wellington.

I've mostly finished the rear battery rack. I need to fold up some feet to lift the rack up off the boot floor, decide how to support the front and rear sections (cantilever from the middle one? more feet?) and devise a way to hold the cells down.

For a while, the rack came with added vice grip.

I once said I should get a load leveller. Well, I finally gave in and got two. I think I did well with $50 Chinese units from Save Barn. After a little fabrication, they hang at right angles and I can adjust everything in comfort. I'm never installing another engine without one.

Part of the fabrication involved a strap with two holes, and the levellers came with a piece that just needed a little straightening. I'm not sure if this steel is particularly hard, or just poor, but it did not take kindly to being straightened.

I'm making progress fashioning the structure between the gearbox and the mount that will isolate it from the frame of the car. I'm using an aluminium and rubber mount from a small Nissan (the round silver and black thing between the tube on the left and the gearbox in the middle).

After many hours of fettling and weld practice, I've managed to weld the reinforcing bars into my front subframe. The motor will hang between these bars and they also provide strength at the front of the frame for cells or other equipment.

My 175A welder took a bit of tweeking to make good welds in 3mm steel. The biggest change that made the most difference was switching from 0.6mm to 0.8mm wire. I think this could also have been achieved by turning up the wire feed on the 0.6mm wire. MIG is a little counter-intuitive, if you weld isn't penetrating and the wire is building up in a large bead on top of the work, you'd think that you have to turn down the wire speed and weld slower so the heat has more time to penetrate. Actually you want to do the opposite, as the faster you push the wire into the work, the smaller the arc, the greater the current and the deeper the penetration. Of course wire speed isn't the only parameter which affects the current.