The blog for conversion of vintage BMW 3.0 CS coupes to Tesla powered electric vehicles
Stop, park, but don't roll
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The Tesla drive unit only has Forward, Reverse and Neutral. There is no Parking pawl. On a real Tesla there are electric worm-drive parking brake calipers that clamp down on the rear discs when park is engaged and stay there even when power is cut. Paul adapted those to his car because he was already fabricating new caliper mounts for his Wilwood upgrade but I'm sticking with stock brakes so that wasn't an option for me. Initially I thought I'd just flash a "Pull Hand Brake" type message on the dash app when you engaged Park but I found a better solution with a product called eStopp.
The eStopp electric parking brake installed on my car
It is a linear actuator and control module that pulls to 600 pounds and then stops. Being a worm-driven linear actuator, it stays in place when power is cut. It is designed for hot rods, etc and comes with a push button for operation but it was a simple task to adapt the electronics to my new shifter mechanism. Fitting it to the car took a bit of planning since I didn't want the parking brake cables to hang below the rear suspension crossmember. In the end, I opted to drill two holes through the lower portion of the crossmember for the cables and fabricated a bracket that attached to the previously fabricated brace in the trans tunnel.
I ran the parking brake cables through the rear crossmember to keep them from scraping on speed bumps
Fully installed on the tunnel brace
Solid and effective. The car won't roll anywhere now when in park and it uses the original parking brake shoes in the stock disc rotors and just mimics pulling the hand brake (which is now gone).
The two parking brake cables come together and are pulled with a equalizing bar
No more parking brake handle
I removed the parking brake tubes and handbrake mount and filled in the hole in the tunnel, cut the cables, swedged on a couple cable ends, and now the car won't roll when it is put into park. Check it out below (ignore the banging -- that's elsewhere in the shop):
As you probably know, I'm not converting just one BMW 3.0 CS coupe to Tesla power but two. One for me and one for my son-in-law, Alex. In fact, I'm involved in a third project for a customer as well. Brett Perkins at P3 Conversions is handling that build and I just consult a bit but I thought it would be interesting to compare how each project has tackled similar problems in different ways.
There are 350 DC volts of Telsa LiIon batteries in my car but I need a 12 volt source to kick off the electronics that energize all the complex systems such as the precharge controller and traction contactors. Therefore, I use a small LiIon 12v battery designed for a motorcycle. The problem is, I keep some things, like my Raspberry Pi gauge computer constantly running so that everything works instantly at the turn of the key and that drains the little 30 Ah battery pretty quickly, like in a day or two.
You've read about the fancy digital dash app I've written that displays all sorts of information on a display in the hole that used to belong to the tachometer. But that still leaves four other analog gauges in the instrument panel: The speedometer, clock, fuel, and temperature gauges. These are old school VDO gauges that just look proper and cool so I want to make them all work with this new digital vehicle.
