Making the adaptor plate

Another week or so of big progress. Tomorrow (sore muscles permitting) I will test fit the motor and gearbox for the first time.

Adaptor Plate

Over the last week my daughter and I have measured and drilled the holes in the two halves of the adaptor plate (marking them out with a transfer punch), bolted them up to the motor and gearbox respectively, welded on some captive nuts, then welded the two plates together with a square made from the box section in the middle. It took two hole saws and a lot of sharpening of bits but we got there in the end. As of today the whole assembly can be bolted together and it is ready to go into the car for test fitting.

There’s still lots of work to do on the adaptor plate. It will need cutting down to save a bit of weight. Some of the holes need adjusting. A few more welds wouldn’t go amiss. And then it needs painting. But first we need to make sure it all fits, and work out how the engine mounts will bolt up. Plan is to use some of the 40mm box cantilevered off the motor plate to bolt up to the existing engine mounts. The two circles of steel cut out from the centre of the plates are actually a perfect fit for the mounts. So those will be welded on underneath. It will all make sense when you see it.


The steel tube I bought was for the coupler to link the gearbox and the motor. I bought two diameters, but it turns out I only needed the 37mm as both clutch centres will sit inside it if turned the right way around. The BMW clutch is a really nice tight fit so getting that square was fairly easy. The Fiesta clutch less so. It has funny little stepped splines that take a little balancing to get them square. And when I say ‘balancing’, I mean welding it, spinning it, cutting one of the welds off, hitting it with a big hammer, welding it again, until it looked pretty straight.

This just left me with the outside of the clutch centre to sort out. There’s a few rough bits from where I cut it out with the angle grinder. I’d been looking for a local company to turn it down in a lathe. But then I got chatting to my neighbour from three doors down and it turns out he has three lathes in his basement workshop! It’s with him now.

Before I dropped it round to him, we used it to make sure everything aligned properly before putting in the final welds on the adaptor plate. Sticking the box into gear I could rotate the prop end and watch the motor turn through the hole left by the clutch cylinder. Despite the rough way in which the coupler was put together it all seems to spin pretty smoothly. Hoorah.


While I’ve been working on the hardware in the day time (when I can get away from work), I’ve been working on the software in the evenings.

So far, I have hacked together a little sketch for an Arduino Mega clone – one with loads of easily accessible i/o pins – that can read the CANbus data from the inverter and change its state or trigger actions based on what it sees. The first thing it does is switch between a series of states: Off/On/Charging/Run etc. Each of these states will require a different set of actions. e.g in run, I have two thermostatic switches coded that will turn on the cooling pumps for the motor and the inverter when they reach a defined temperature. These will be triggered by relays connected to the Arduino.

Next step is to start reading in the shunt data and then mount it all in the car so I can begin interacting with the ABS/ASC. Fortunately, all the devices seem to run at the same bus speed (500kbps).

I also need to knock up a mount for the Arduino, CANbus interface, and various sundries. I bought an old ECU/DME off a BMW forum and I plan to harvest the connector so that I can re-use the existing loom and connectors. The stuff I want to fit in won’t go in the old case so I’ll 3D print something that will slot into the old cradle.

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