Mazda MX5 Conversion Blog


2 April 2008: The Fabricated Aluminium Arrives

After an unnecessarily long wait due to an assortment of communication breakdowns, the aluminium pieces for the motor frame and battery boxes were FINALLY ready to be picked up from the laser cutters.

They were designed to fit together like a jigsaw, with tabs and slots in adjoining parts (made possible since laser cutting is so accurate), and this ensures precise positioning of the pieces before welding. One of the pictures below shows a close-up, for example.

The 12mm pieces did need a bit of finishing before they would go together. Firstly it seems the laser must struggle a bit going through 12mm Ali, as the edges were a little rough and there was some blowout on one side. It also appears they used half inch (~12.5mm) aluminium for the main frame instead of 12mm.

And the tolerances were tighter than planned. I was expecting them to cut with the laser centred on the lines in the CAD file I supplied but it seems they accounted for the width of the laser and cut at the outside edge of the lines. We're only taking half a millimetre, but as a result I had to spend some time with the linisher to grind some of the parts down a little until they fit together.

Anyway, so far it all seems to be a good fit for which I am very glad, and now that fitment has been confirmed I can send them off to be TIG welded. I also need to get the driveshaft lengthened so have measured it up with the real frame in there, and will send that off to be done as well. Once they are back I can actually install the motor and machine up the coupler between motor and tailshaft.

Then it's time to wire everything up. I can almost see the light at the end of the tunnel now.. ;)


(1) The pieces of 12mm aluminium making up the motor frame

(2) The loosely assembled frame next to the old wood prototype

(3) Test fitting in the engine bay

(4) Test fitting with dummy motor (the real one is too heavy until the frame is actually welded)

(5) The rear battery box next to the wooden prototype, one battery shown

(6) Test fitting the rear battery box

(7) The front battery box

(8) Closeup of a corner joint on a battery box, joined like a jigsaw

(9) Test fitting the front battery box

(10) Showing placement of the front battery box JUST ahead of the motor - a tight squeeze!

(11) Beneath the car, showing rear subframe joining to new frame (bolts not done up obviously)

(12) Motor frame has little feet for bolting to factory engine mount locations

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