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Fun with Tesla motor

129326 Views 142 Replies 32 Participants Last post by  matchke
So last week I've became a proud owner of a Tesla drivetrain:

On the way home, we stopped by a Tesla superchager - the owner of the brand new white Tesla was quite surprised, to see a Peugeot with a Tesla drivetrain :)

By the looks of it, this motor indeed is the same one as in Tesla Model S. I have no idea if different battery in Model S means different motor, but most likely they are all the same (as power limiting factor is the battery).

The history of this motor is quite complicated. It came from Mercedes, where they were using it on a testbench. Most likely this motor never even seen a car :) The reason why Mercedes had it, is their new Mercedes B electric car. I presume that they couldn't be bothered with downsizing their licensed Tesla parts (they bought everything from Tesla, including the battery and charger), so Mercedes B motors are (most likely) Model S motors. If someone has the dimensions of Tesla Model S motor, please write them here. I would love to compare them.

I've bought the whole drivetrain - motor, single speed gearbox and the inverter. Since this is a factory test motor, most likely the firmware will not be compatible with Model S (it might be compatible with Mercedes B). In the best case it just spits bit more diagnostic information, but most likely having a Tesla capture will not spin it. This is okay, as my plan is to use my own motor controller to replace the "brain" of this beast. Over the past year, I've started to enjoy performing lobotomy to different inverters :) (link in my signature).

I'll be using this thread to give some information about this motor, and how to use it in your conversion.
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The rotor cannot be removed from the gearbox assembly. So reusing just the Tesla motor without the gearbox is not possible.
Well thats annoying :mad:
Would you even want to hook this up to another gearbox? I believe that you will just be destroying these boxes.

The lash in a standard gearbox is way to much for an electric torque monster.
If you wanted to use this in a direct drive application in a conversion with a solid rear axle, the integral gearbox might make things a bit more complicated than they would be with just the motor alone.
In theory you could block one differential output, rotate the drivetrain by 90 degrees and then connect the other dif output to your shaft. But the ratio would probably be unusable.

What could be done, is just to crack open the gearbox case, throw one half + all the reduction gears, and cut out "irrelevant" pieces of the other half. Then you don't have to manufacture anything (except for the motor shaft coupler of course).
Yeah, but that could complicate motor mounting if you have limited underhood space.
You could change the rotor, but the stator is heat shrunk into its housing which is welded to the gearbox casting .
So, if you want to change the gearbox, you have to change the motor also.
Of course you could always keep the old box housing and motor with new internal fitted. Or fit the old motor rotor into a new gearbox and motor stator...but really , do any dealer warranty repairs involve stripping down and rebuilding something like a failing gearbox ...or do they just replace the whole assembly ?
Anything is possible , but It's just not practical !
I don't think Tesla wants individual service centers doing things that involved. They seem to prefer sending the whole unit to specialists within the company. Same with servicing of the battery pack.
There is a post in by Robert Macy on May 17, about a MEMS motor with over 1000 poles and driven at 1 MHz. A stacked version was built in about a 6 inch cube with approximately 360 HP. The post was an OT drift in a thread about the Amtrak wreck.
This really made me curious, so I looked up the post. Seems that was predicted output, not actually measured. Just in case anyone is as curious as I was:!searchin/$20360/

Thanks for the info, forgot about the 'practicalities' of electrical
distribution where the weather can be a bit daunting to survive,
especially where it is not possible to make the system 'grounded' like
here in the U.S. [I am assuming Finland soil is a lot like Norwegian soil.]

Learned a lot about skin effect after working with a MEMS motor design.
The motor had over 1000 poles, so the drive was 1MHz, and desired to be
3MHz. You want skin effect? Work at those frequencies!

Learned two things:
1. Turned out 'leaving' unused conducting metal created a lot more loss.
It wasn't just a matter of hollow aluminum tubes in a TV antenna to save
money, but truly the unused metal in the centers 'ate' some energy. Skin
effect is usually described as 'attenuation vs depth' and the phase shift,
a 'rotation' as you go down in depth is left out of those papers. Currents
actually go the WRONG way, subtracting from what you want and still
consume energy.
2. Trying to 'simulate' Litz effect by using multiple strands made little
difference. Envision a bus bar where the carriers all go to the two
furthest separations of the rectangle. So I naively tried placing a
multitude of wires to simulate the rectangular cross section BUT having
the wires separated I THOUGHT would produce better results. NO! The second
you connect the conductors in parallel at each end, the distributed
inductance/resistance forced the carriers right out to the outside, almost
as if everything was still a solid rectangle. ...very frustrating.
However, I have seen some IEEE papers describing a 'pseudo' Litz effect
from using stranded cabling, where the cross conductance is decidedly
different than the longitudinal conductance. Just because its a paper
doesn't make it so, but I never pursued checking data OR refining my
analyses tools, and their premise does seems like a reasonable effect.

By the way, that MEMS motor has some incredible characteristics, like when
the rotor and stator of this 1.5 inch diameter motor were put together,
its overall thickness was around 80 microns, thinner than a sheet of
paper, had NO wear surfaces, all air bearing, and had several oz-inch of
torque and small mass so was up to 6,000 rpm in about 9 mS. and we
routinely/indefinitely ran current densities through the copper that were
equivalent to 100 Amps through a 36 gauge wire! Only if we went to 200
Amps equivalent densities did we lose a copper trace. As a lark, I once
applied the design concepts to making a 'stacked' motor with diameter of
4-6 inches and lots of disks to make a 6 inch cube size [didn't check the
heat] the idea was to make a small efficient electric car motor.
Amazingly, using a standard multi-battery pack, the predicted output
torque/power of such a 'block' was an electric car motor that had
something like the equivalent of 360 HP gasoline engine, be like a
corvetter engine, but only a six inch cube. And drain your batteries
REALLY fast.
OK, that would be a very costly business model:)
It would be if they were meant to serviced regularly. However, if most of them last for at least 8 years, as they are intended to, then its not an issue. Also, they can more easily diagnose a manufacturing issue if many owners are having problems.
I doubt there are many auto makers who expect (allow?) component level repair ( gearbox internals, engine internals, etc) , by a regular dealer service technician , especially under warranty cover.
Assembly replacement is the norm and often cheapest (time is the real cost) as well as enabling better analysis of defects from the returned assemblies.
Yep, although it does makes things more difficult for us junkyard builders.
I almost died laughing at the first paragraph of this article:

"Electric Vehicle Television (EVTV) prides itself on producing some of the most boring video content available on the internet. Truly, unless you have a passion for electric vehicles, learning how they work and how to build them, it more closely resembles a sleep aid than entertainment. "
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