As you will know if you have been following this project, I’m a little disappointed with it on two fronts so far. First, the range, and second, the power. I now have a plan to address both of these issues.
First up is an additional battery pack. Now that I have rescued the batteries from my extreme range test (they turned out to be fine with some gentle charging), I have two packs. One was going to go in Project 2 but I think I might go for a different technology/brand for that. Much as I like the design of these BMW packs, they don’t have the greatest power to weight/space ratio. So for now this pack can boost the range of this one. I may even try to squeeze a third pack in at some point.
There’s plenty of space at the back where the spare wheel was without any modifications to the structure of the car. I’ll just add some tabs to the rear rails and bolt it in there, once I’ve made up a new battery box.
The plan is actually to make two identical ones, since I’m not happy with the front box. I still have some CAD work to do on the design and I probably need to find someone with a big metal brake to bend some sheet for me, so not sure how soon I’ll get this done.
Changing the front box will also release space for a larger radiator, and a heater up front. And I will need to add a junction box to bring together the outputs of the two packs. But those will be separate posts.
Range is useful and all, but what I’m really excited about is improving performance. Over the summer I picked up a rear motor from an Outlander PHEV.
This week I separated the motor from the diff/gearbox it came with and started measuring up for a new coupler and adaptor plate.
Though it is notionally less powerful in terms of maximum output, the new motor is significantly beefier than my current one. I suspect it will offer much better torque and it also operates over a much more sensible rev range.
The black pipes are coolant pipes. What’s nice is that the rear motor is water cooled so I will be able to do away with my oil cooling setup altogether and maybe use that space for a large radiator. I’ll be hanging on to all the parts for the future though: the gearbox motors I want to use in Project 2 are oil cooled.
I extracted one of the spindles from the gearbox that mates to the splined axle on the motor to use as the basis for a coupler.
I could have hunted out a clutch centre to match up but I’m not sure which ones work. This will be a perfect fit, and if I do decide I want to do a front-wheel-drive conversion at some point, these motor/diff combos are not expensive.
I’m waiting on a clutch centre to fit the BMW that is being kindly donated by another member of the ZRoadster forums. Just like last time, this will be attached to the other end of the splined spindle with the lathe providing alignment, then welded up.
I’ve started sketching out an adaptor plate and mounts for the new motor. The nature of its shape and particularly its depth means I won’t be able to re-use much of the old ones so there is a fair bit of fabrication involved. But that’s OK: it’s fun, especially now that I have my workbench outside.
The good news is that the new mounting frame should sit much lower in the engine bay, clearing more space for ancillaries up above. Between this and the new battery box, there should be loads of space.
Because I don’t have a full scan or even sketch of the empty engine bay, or the various components, a lot of the fabrication will need to be done on the fly with access to the car and can’t all be done in CAD. But the sketch has done enough to inform what metal I will need and I will be picking up a selection of plate and box tomorrow. I still have tube for the coupler, should it be needed.
That’s it for now.