openinverter forum

Some of you may know I have been feeling the pain working on the M3DU inverter pcb project these past weeks. So logically the thing to do is take a break, refresh myself and return with a clear head. To that end I dragged in my "spare" drive unit and got it up on the bench. Using only Tesla approved tools I proceeded to open the inverter end of the gearbox. The inverter was sent to Artur for the PCB project but that`s not important. My super evil plan is to extend the layshaft out through the case. Replacing the uber sexy "BB1-4560" bearing on the front of the layshaft with a 6308-2RS and a oil seal held in a 3d printed part.

Now I know Fellten do a set of gears to give a final drive ratio of 3.54:1 https://shop.fellten.com/shop/tm3rdu-gs ... 54-1-13829

My current plan is to remove the diff altogether and 2.61 : 1 is a better fit for my very tentative project which has a 3.46:1 giving a road speed of approx 47mph at 6k rpm on the motor. Also, I'm an opensource cheapskate

Anyway, lets see how I get on

Pardon my ignorance, but is your goal to connect the motor directly to a driveshaft (or "prop shaft," I believe it's called across the pond) in an RWD vehicle? So, like a baby Revolt Systems crate motor?

Exactly

Picked up some supplies for the project

Cool. I’ll likely have the measurements of the motor interface side of the housing in the next month.
I’d like to use the motor entirely independently of the r gear box.

I’ll take a closer look at the intermediate shaft, and how we could interface to it. Are one of the gears pressed on the shaft?

The big gear is a press fit on the intermediate but we need that one. Center bore is 22.90mm by my measurements so will be making a press fit into that and weld with some 29/9 rods. Will have a video soon so the internet can tell me I'm doing it wrong.

split my rear du apart.

very simple and minimal amount of parts.

all the case halves only have plainer machine features on them, this should lend itself to easily re-housing the motor alone.

Damien has the new 4d3 drive unit with hairpin windings, at first glance, this is the more ideal motor as it’s easier to bend the phase leads 90degrees..

Very Cool! Ive seen completed units like this although information on how its actually done and the oiling are extremely hard to find.

I am planing to use Model 3 drive unit in my project as “straight” drive by replacing whole “reduction gear box” part of unit by custom made part.

Stator housing has only flat surfaces as mentioned above by Bratitude. There is only coolant pass through, shaft from rotor, 3 phase cables and coolant return. I plan to have phase cables bend 90 degrees so inverter will be mounted on the side on stator housing. There needs to be roughly 2 litres of coolant (it is somewhere in Tesla docs maybe i am wrong).

Middle part should include housing for original Tesla coolant pump and filter. on side i would like to create provision for mounting point to car chassis. Output shaft and mounting should allow to use almost “any” gearbox/reduction gear box.

I did not purchase my motor unit yet so all of this is theory till i will have unit and time to start working on this.

Davidk wrote: ↑Sat Jan 25, 2025 8:38 pm There is only coolant pass through, shaft from rotor, 3 phase cables and coolant return. I plan to have phase cables bend 90 degrees so inverter will be mounted on the side on stator housing. There needs to be roughly 2 litres of coolant (it is somewhere in Tesla docs maybe i am wrong).

You’re a bit mistaken, there’s no coolant in the m3 drive units. Only atf. The oil pump runs Through a heat exchanger, then into a manifold. this manifold diverts part of the oil through a port that pushes the oil through channels in the stator. the other part of the manifold pumps oil through the input shaft bearing.


As it stands non-hairpin wound motors like the one I have, it’s probably not a good idea to bend the phase leads, as they are covered in an epoxy coating.

A 3d4 (or is is 4d3?) drive unit is the new hairpin design, which uses solid copper. This would be find for bending out of the way.


I’ve started looking at and designing an adapter plate to use the motor independent of the gearbox. There’s a lot of funky features and challenges to make this viable and economically possible, as it’ll with require a 1ft dia 5in thick billet block of aluminum todo

Bratitude wrote: ↑Sun Jan 26, 2025 2:11 am You’re a bit mistaken, there’s no coolant in the m3 drive units. Only atf. The oil pump runs Through a heat exchanger, then into a manifold. this manifold diverts part of the oil through a port that pushes the oil through channels in the stator. the other part of the manifold pumps oil through the input shaft bearing.

Yes, you are correct i was trying to be precise in my writing and called atf as coolant by mistake.

Regarding pricing, yes it will need hug chunk of aluminium and lot of CNC time, that will not be cheap.

BTW as you disassembled your motor, what is purpose of that (white) plastic round guard on stator side? I did not figured why it is there…

Davidk wrote: ↑Mon Jan 27, 2025 11:11 pm BTW as you disassembled your motor, what is purpose of that (white) plastic round guard on stator side? I did not figured why it is there…

It’s an oil baffle

Here’s the motor side case half. you can see the larger hole at the bottom edge of the case, this is in inlet for the oil pump.
Adjacent to that is outlet hole from the oil filter.
This hole connects to the top right hole via a plastic tube (seen in the other photo). Oil then passes through the heat exchanger (across the top of the case), then exits back into the case via another hole. Another tube splits the oil from there to the hole right next to it(which feeds the motor) and y’s off to the other case half. On the other car half the oil is pumped through the input shaft and intermediates shaft bearings.
Here’s the other case half where you can see where the oil tube inserts and routs the oil into the bearing bores
Using the intermediate shaft for out put would require cutting a hole in this case half, and making a plate with a shaft seal on the other side of the case. Not sure of oil pressure, but I image the pump runs at different speeds based off temperature? the viscosity and how small some of these Chanel’s are, I’d imagine it’s pretty decent.
Hard to say if you could have a shaft seal there without the oil blowing by. Just need to keep those bearings lubricated

After bit searching on internet it looks like Damien has 3D6 or 3D7 version.

Newer 4D1 and 4D3 are with new “squared” inverter, relocated filter and pump.


Tesla has description here: https://www.tesla.com/ownersmanual/mode ... CAA58.html

Wiki with a lot of details: https://tff-forum.de/t/wiki-model-3-mod ... its/190111

Really interesting project and looking forward to seeing how the seal holds up.

I think im out of the loop, but which of the BMWs is this destined for?

6k at ~60mph seems a little high (not saying you wrong) just thinking that a some of the BMW gearboxes are 1:1 in 5th gear with a rear end of 3.64 and would have assumed they were at around 3k at that speed? Looking forward to seeing if Elon can put out enough torque to get you around well enough.

Ah wait, I am an ijjit. Just reread your post. I thought you were going direct drive from the rotor to the final drive. Is there a 2.61 reduction in the model 3 motor before the original diff? I haven't seen inside one.

I am in the midst of a similar project: I am adapting the Model 3/Y motor for use as a longitudunally mounted motor with a gear reductuion system. it will be located in the transmission tunnel and hook up to the driveshaft. I am completely remoting the inverter, oil pump, heat exchanger, etc. We are nearly ready to produce the first prototype. I will post the project once we have a working model.

Just to confirm, my 3d6 motor has hairpin design.

3D scan of casting (stator side) created today. Feel free to use them, precision should be 0.05mm.
https://drive.google.com/drive/folders/ ... sp=sharing

Progress is slow, many small details that are hard to be replicated or i will not replicate them. Working with CAD/Fusion after 20 years of not using these tools is hard.

First issue i am facing is "requirement" of 2 litre of atf oil as it takes considerable amount of space.