Conscious coupling

Per our plan from the last entry, we have spent much of the last week cleaning the engine bay and components and preparing to start putting things back together. There’s still some cleaning to do (transmission mostly) but we’re now at a stage where we can start building. First order of business is getting a coupler made to link the electric motor to the transmission.

First thing I noticed on removing the flywheel from the old motor is that it is bloody heavy. A dual-mass unit, it is rather more weighty than I was expecting and I am concerned about the load it will place on the electric motor’s bearings – a load I don’t think they are designed to bear. You can see pictures of the flywheel temporarily connected to the electric motor on a 3D-printed test of my original coupler design below.

I could replace the heavy flywheel with a light weight aluminium version but that will add another couple of hundred to the build cost. So I am tempted to just ditch the clutch idea and connect the output shaft of the motor directly to the input shaft of the transmission. We shall see.

The next challenge is getting the coupler made. My original plan was to put something together in Fusion360 and send it off to Protolabs to have it made. But this hasn’t worked out. Protolabs’ machining capabilities, although sophisticated, can’t reach inside the 19mm hole of my original coupler design to carve out the splines that mate it to the motor. They can 3D print it instead, but this would cost £1400 – completely out of my budget.

I have found a local company (well, Oldham) who specialise in drive trains and can cut me a slightly redesigned adaptor using wire erosion. But this would cost over £400 for the single piece and I would then need a second piece made, albeit much simpler, to stop the coupler sliding on the shaft under pressure from the clutch (if I use the flywheel) or to mate to the input shaft on the transmission (if I don’t).

The alternative is to get down and dirty and make my own coupler by finding things that will fit the splines on each end. I already have a clutch plate that mates to the transmission. The challenge is finding something that mates to the motor. My fellow EV adventurer Jamie has now acquired the same motor I have and believes that a Suzuki Jimny clutch plate will fit. I’m not so sure as the spline count doesn’t seem to match. We will find out today when he picks one up.

Looking at the specs for them, an old Fiesta clutch has a 19mm bore and 17 splines. I’m wondering if that might work instead. I might drop by some garages today and see if they have any old clutches lying about.

The challenge then is making something that is sufficiently balanced to spin at 7,000 RPM without exploding. It needs to be very carefully balanced and that is hard to do without a lathe. I might have to outsource it anyway, if I were to go down this route. Or I might be able to make something good enough to get me going…

In the meantime I’ve ordered some more parts. My high voltage cabling (doubly insulated 35mm2 welding wire, and the conduit (to give it an extra layer of protection) is on the way.

I also bought another steering rack, this time from a Mini, because the 1-Series rack didn’t fit in any dimension. It was too wide and the electric motor fouled the anti-roll bar. And the angle of the input shaft was all wrong. If this Mini one doesn’t work, I may have to go back to the hydraulic one and buy an electric pump. But that feels like a messy solution for an electric vehicle.

The project continues…

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