It has been a long haul, but I finally have the motor in my '67 Beetle EV conversion. I've had one setback after another, but I expected it to be the most technically challenging part of the job and I've come to appreciate Murphy's law.
At first glance, mounting the Mars Electric motor to the transmission of an old-school Beetle should be a snap. You need exactly two parts to do the job: a shaft coupler and an adapter plate. The coupler lets you mount the flywheel and clutch to the electric motor. The adapter plate, which looks a bit like a top hat, secures the motor to the transmission.
But converting a car is not an exact science. Every conversion requires fabricating parts and inevitable adjustments along the way. I mentioned in my last post that the engine-mounting holes in my adapter were in the wrong place. Turns out the holes on the transmission side were off as well. I had hoped that was the end of the problems, but it was just the beginning.
Good thing I found some good help.
Spencer Stromberg of the Electric Car Company of Utah has been a savior, helping solve one problem after another to get the motor mounted. During the day he's a mechanic and parts fabricator. At night he's a student earning a degree in manufacturing engineering. The guy is a mechanical whiz: If you need it, he can build it.
I called Spencer a few days after discovering the mounting-hole snafu. He was way ahead of me and already working on a solution. He measured and drilled new holes for the motor side of the adapter. Easy. The transmission side was more difficult.
He used a 3-D laser modeling device (I've added one to my Christmas wish list) to trace the Bug's transmission into a computer. Once he had the transmission's exact measurements in the computer, he mounted the adapter in a CNC milling machine and cut new holes. Then he welded the old holes closed and ground them smooth. Now I have a perfect adapter plate.
A few days later, I stopped by the shop at lunch to see if we could get the motor in. If everything lined up, it would've been a breeze. I should have known Murphy would rear his head again.
We'd fixed the adapter, but so far all we'd done with the shaft coupler was admire its precision machining. It's gorgeous. But when we tried tightening it onto the motor shaft, it wouldn't cinch. Turns out some extra threads in the bolt holes were keeping the coupler from tightening. Spencer used his trusty CNC machine to remove them. It was pretty cool, so I had to ask what it costs.
Can you imagine? "Honey, there are lots of uses around the house for a CNC milling machine!"
I don't think she'll go for it. Used ones start at $7,000.
Once we got the coupler and adapter plate mounted on the motor, we tried mounting the flywheel. Of course there was a problem. It was rubbing against the adapter. It was a simple fix that required moving the coupler out a bit, but we had to disassemble everything. Argh!
Next came inserting a pilot bearing into the coupler to center the transmission shaft in the flywheel. It was too big. Somewhere Murphy was busting a gut laughing at me.
"No problem," said Spencer, "I'll just mill out the hole to fit the bearing."
At this point I was recounting all the times Spencer has saved my bacon with his cool toys and thinking I really need to buy him lunch. Unfortunately my lunch break was over and I was due back at work. It would take some time for Spencer to set up and mill the coupler, so he suggested test-fitting the motor and getting some pics before I left. A test fit required cutting a piece out of the rear apron of the Beetle.
Spencer brought out a plasma cutter, which I promptly added to my Christmas list: "It will be great around the house, honey."
I don't think she'll go for it.
After the cut, it looked like things would go together well, once we get the bearing problem solved. I went over Saturday to finish things up and tow the Bug home. The good news of realizing we were simply using the wrong bearing (no milling needed) was followed by another setback.
As we assembled everything, Spencer noticed it didn't look like the clutch would sit far enough back in the transmission. If his hunch and quick measurements were right, the clutch pedal wouldn't travel far enough to engage. We decided the company that made the coupler probably knew what it was doing, so we went for it. The motor mounted fine, but sure enough, the clutch didn't work. Murphy struck again, hard.
Spencer and his cool toys couldn't fix this one. We needed a little more than an inch and couldn't move the shaft coupler that far out on the motor shaft.
I was starting to wonder if we'd ever get the motor mounted, and I was entering the final two stages of grief (depression and acceptance), when Spencer suggested eliminating the clutch altogether. Turns out he had a clutchless shaft coupler on hand from another project that fell through.
There are two schools of thought within the DIY EV crowd about clutches, and I've had long conversations with convincing disciples of each side.
Many converters see no reason to keep it, because an electric motor has no need to idle when stopped. An electric motor also has very little friction, maintaining enough RPMs when you lift off the accelerator pedal to eliminate the need to decouple the transmission and motor while shifting. Ditching the clutch also reduces rotating mass, which leeches energy from the motor when accelerating. Finally, an electric car is mostly driven in a single gear, so you don't need to do much shifting anyway. Hell -- the Tesla Roadster has only one gear.
But there are those who say you've got to keep the clutch to minimize wear on the transmission synchros and provide a connection between motor and transmission that "gives" a little under high torque. Sometimes the accelerator on a conversion is a bit jumpy, and a clutch lets the driver apply a bit of finesse.
As I mapped out the project, I decided keeping the clutch would be wise, because I'm using a motor that is larger than those found in most conversions. But going clutchless would let me get the motor mounted and the project moving ahead. Lance Michael of the Utah EV Interest Group happened to be in the shop observing. He has a clutchless '70s Bug and has driven it for more than a year with no issues. It's always seemed like an elegant solution, and it is much simpler.
I decided to ditch the clutch. It took a little tweaking, but everything went together easily. We jacked up the car, hooked up a battery and watched the wheels spin. Success! Take that, Murphy!
One remaining concern is whether to add additional support for the motor. The same four bolts that supported the 250-pound engine support the 203-pound electric motor through the adapter plate. I'm not worried about those bolts, but there are four others that hold the motor to the adapter plate. They're pretty close together, and I'm a little worried. But I'll sort that out later.
After buying Spencer lunch, he helped me get the car home. With the Bug in my garage, everything seems a bit more real. My wife caught me giggling after dinner Saturday when I opened the garage and saw my project. Next up on the to-do list are cleaning the engine compartment, removing the gas tank and figuring out where to mount the batteries.
It will be much easier to plan and work on now that the project is only a few steps away. Here's hoping Murphy doesn't catch up with me.
Got any advice, suggestions or ideas for Matthew? Share ‘em with us! Follow his progress on Twitter @Wired_EV and here at Wired.com every week. He’s also launched a blog, evBeetle.com, to cover the conversion in microscopic detail.
Photos: Matthew Redd/Wired.com
See Also:
- We're Building an Electric Car!
- Our EV Conversion Gets A Curvaceous Body
- Searching For a Motor To Drive Our DIY EV
- Our DIY Electric Car Gets Some Batteries
We test-fit the motor.
This is the shaft coupler, flywheel and clutch assembly, which wouldn't fit. So we ditched the clutch and replaced the entire assembly with ...
... this clutchless shaft coupler. My electric Bug won't have a clutch now, but it isn't really necessary anyway.
