Cutting for the rear battery box

I've been racking my brain and trying to set a program outlining the step by step progression for converting however I keep changing my mind and if I stop long enough I change it again. I came back from work determined to get the body painted before Christmas but ... dammit, I've changed it again! I've realised that as it is new to me and that there aren't many RX7 conversions I find that I'm working it out as I go, I'm sure that is what everybody else is doing.

So, I will cut the rear boot to accommodate the rear battery box, make up the coupling to connect motor to gearbox, get fabricated the adapter plate, fabricate the front battery boxes and plan the next step after that. Sounds easy doesn't it? So I started on cutting out the rear of the boot for the battery box. They say you should measure twice and cut once ... hell's teeth! I spent 3 hours procrastinating with my measurements before I put my heart in my mouth and made a cut! Of course once I made a start, cutting was 'in like Flynn'. I should mention now that if one is to cut the body of a car I suggest the use of an air saw, it is like a hot knife through butter ... so long as it is only 1-1.5 mm. I bought one from Trade Tools Direct for $68 and I love it! Sometimes I need to use the 4" grinder but the air saw is a beauty.

The problem with the series 1 (S1) RX7 is that the boot is not very big, the spare tyre is recessed with the 50ltr fuel tank underneath that. Together they measure on the vertical 300mm. The batteries are 285mm but I'll need a little extra to accommodate BMS sensors and cables/straps so I am looking at 300mm. So how was I going to get this right? Due to the catch for the hatch is on an angle it made the the fitting of the box awkward so I followed what Ian from ZEVA did and made a box from MDF to the actual dimensions. This allowed me to see if it could fit in, not so much in the hole that I cut out but getting it through the hatch and body of the vehicle.

Looking at the underside of the chassis I have not touched the main chassis rail at all, only the skin at the back section as I want to retain the integral strength of the monochoque body. I've had to make the opening a bit bigger to allow the box to rotate in. I was a bit desperate as I wanted to have 27 batteries in the box with a further 18 batteries in the front, total 45; so reducing the amount of batteries in the rear would completely stuff up my traction voltage. As you can see the picture to the left it will keep the back boot nice and clean. The other picture below shows that it doesn't extend far at all, I made a botch up when I made the mock up as it extends 12mm more than it should. Should the box be too low (but I think the height is okay) I can raise the box within the rear compartment. I originally thought I would weld plate and box onto chassis but now will bolt the box as it is larger than I thought and will have strong tensile strength. One issue that I will be looking at further down the track is that of spare tyre. There is a trend that vehicles are not supplying a spare tyre ie: Lotus Elise, BMW M Roadster, Peugeot 206CC but supply a pressurised can of latex or similar to blow up the flat tyre. A pressurised can of sealant is my preferred course.

The other option is to put a 'skinny' spare on top of the battery box complete with a tie down or even a skinny with flat tyre. Really, how many series 1 have you seen with 15-17" wheels, do they have a spare? Because a 15-17" won't fit in the 13" spare wheel well.