openinverter forum

Hey Mods.

Can we have the rest of the thread from this point moved to this new topic.

MattsAwesomeStuff wrote: ↑Sun Feb 16, 2020 1:48 am Bit of a tangent... a guy on the DIYEC forums was asking about the whole Gen2 transaxle thing and I couldn't find him a clear answer.

I'm not sure what the difference was between what Damian did to the Lexus gearbox (with external oil pump) and the Prius gearbox, if any.

The user has an operational Gen2 Prius, and notes something I haven't seen discussed before: "With the ICS Kill applied (basically the fuel pump disabled) it can reach 85km/h (roughly 50mph) when the battery is fully charged. I understand this limit is to avoid over speeding the planetary set."

So here's the diagram of the drivetrain for anyone curious:



And, naturally, if you lock the Engine output (planetary carrier), with the ratio difference between MG1 and MG2, you're going to be spinning MG1 what looks (if scale in the diagram) maybe 4x as fast as MG2. Can MG1 handle that at highway or above highway speeds? Is it a concern? Is it not a concern?

The user also asked about using a Gen3 inverter to run the Gen2 transaxle (since the Gen3 inverter control board is more mature), and I suggested that's probably no issue, as the motor has basically 6 power inputs and is otherwise agnostic of how the 3 phases are powered. But, as always, I'm not sure.

A couple of videos from Damien's early experiments with Toyota FWD transaxles.

Includes welding of the power split device, oil cooling

Anyone have a definitive answer if the Prius with a welded planetary gear can run at 100kph and do it for extended periods of time (assuming adequate cooling is provided)?

I'm wondering out loud if a modified Prius transaxle would be suitable for a (BMW) Mini or MR2 conversion.

sfk wrote: ↑Thu Mar 05, 2020 4:09 am Anyone have a definitive answer if the Prius with a welded planetary gear can run at 100kph and do it for extended periods of time (assuming adequate cooling is provided)?

I'm wondering out loud if a modified Prius transaxle would be suitable for a (BMW) Mini or MR2 conversion.

Tesla SDU would be better

*disclamer: I have one for sale suddenly

sfk wrote: ↑Thu Mar 05, 2020 4:09 amAnyone have a definitive answer if the Prius with a welded planetary gear can run at 100kph and do it for extended periods of time (assuming adequate cooling is provided)?

What are you hoping for in terms of definitive?

As in, a few thousand miles on an actual vehicle? Or as in, "We checked the math, it looks like it's within spec"?

For the former, I'm not aware of any but that's not saying much.

For the latter...

A welded planetary on a Prius Gen 2 should be fine over 100kph. It's almost fine (85kmh?) without a welded planetary. Which I think is a 2.61x geardown from MG2 (which spins in lockstep with the tires I think, so, MG2 is okay with whatever the max speed of the Prius is). Once you weld the planetary, you spin MG1 at the same rate as MG2, meaning that both are fine at the max speed of the car. Doing the math backwards, 85km/h * 2.61 = 222 km/h. And, looks like the actual top speed is ~170-180km/h, maybe because of tire reasons but also some other people checking the max ratios for the motors. So, ballpark that's right.

As to whether MG1 and MG2 will overheat when driving at 100km/h? I don't know. But they'll spin fast enough within spec with a welded planetary.

A welded input (engine output) shaft on the Gen 3 I think is fine, because Gen 3s have an added planetary set on MG2.

I also found out that the 2012-2016 Prius Prime (plug in) is limited to 85km/h Europe, and 100km/h elsewhere, though I don't know if that's a component difference or just a legal one.

Hope that helps.

Yes that is very helpful thanks. I just wanted to know if 100kph would be spinning the motor bearings faster than their max.

The answer is : that would be beyond max speed for MG1 on a Gen2 transaxle if the planetary gear was not welded but should be just fine if spinning same speed as MG2.

i have had a special axle made that joins MG1 and MG2 together. My project is very slow, so when i started my project half of the motors available now, were hot when i started.

Hoping to make more progress in the next couple of months.

Hi there Johnspark, seems you are making progress, how ever slow it might feel. I'm about to purchase a Gen 2 Prius for the same type of project. Would be great to know about your axle made between MG1 and MG2.
From what I see, it is safe to say locking MG1 and MG2 will not cause overspin of MG1?
Provided oil pump and cooling is provided, and the vehicle beeing driven is around 800kg, the gearbox should be a reliable option for 100% EV.

Hi RetroZero, I am sure MG1 won't overspin. The welded planetary gear has two teeth that engage with a spindle for turning the existing oil pump. Are you thinking this wont be adequate? The transaxle does have water cooling that needs to be used of course. This transaxle would be able to move a 800kg vehicle with gear box. I forgot to get the two teeth added to my axle so have to use my own electric oil pump to pump the oil around.

I am planning the transaxle to be motor and gearbox in one. Just found out, the donor véhicule is a Gen 3. Checking out the differences that could have, besides the logic board drop-in being way more simple

Bummer, it's a Gen 2 - not a simple 'plug and play'. However, this helps with moving R&D forward to have a nice logic board. Seems lots of people working on minor problems to make Damiens' work around/Johannes Brain board even better, so hopfully I can add my 2 cents on practical side.
Do you know of any operational Gen 2 transaxle conversions?

I'll try not to forget the 2 teeth for the oil pump. I would like to make the planetary lock up an option for reproduction through open inverter... Will obviously have to sort out details with company that makes it in the first place. Do you have any rough drawings of part you had made?

post deleted

Thanks, I know why they must be locked up. Thought you had some fancy coupler made up - I am anticipating ISO9001/TUV and all the other certifications they can throw at me...

Get a coded welder to tig the planet gears. Worst case you have to xray the welds once to keep them happy.

Not a bad idea, thanks. Got some one here who does weld x-ray testing . KISS (Keep It Simple STUPID)

This all looks very promising!

With the welded modification made so MG1 and MG2 turn in unison, what are the thoughts on coupling the protruding MG1 splined shaft with the transmission for a RWD vehicle?

If it's feasible then could remove the running gears to reduce weight. Forgive me if this was the plan all along and I'm just stating the obvious!

My plan is FWD for the moment. Transaxle will replace original transmission, and substitute engine block with a battery pack.. If we can make MG1 and MG2 run in unison (which Damien has done on Bexus), we have 80Kw

RetroZero wrote: ↑Tue Apr 28, 2020 9:58 am My plan is FWD for the moment. Transaxle will replace original transmission, and substitute engine block with a battery pack.. If we can make MG1 and MG2 run in unison (which Damien has done on Bexus), we have 80Kw

Hm... Could we do that with a single brain while muxing feedback from both sides current sensors? I know that it could be sumed and averaged, but what would then IGBT signals demand? I mean if you have 450Arms requirement from one brain and then signal is distributed to two power sections...
could be that we would need one fast chip to mux those signals and translate them summed to the brain. Then there would be no problem if brain would demand 500A and MG1 would provide 200A and MG2 woould provide 300A. Complicated?

How did Damien did that exactly?

Yes, complicated, but Damien managed. Let's get the Gen 2 inverter running MG2 first. That's already enough for my little brain. Johu mentioned having 2 boards in the future (who knows). Locking up the MG's is necessary in any case to not have MG1 over spinning (even if used for charging only)

1h30 later, transaxle Mg1 was removed. Not as scary as I thought it would be. Now off to see how we lock up this baby to withstand 30kW of Mg1 Japanese Power added to Mg2... Will hopefully blend power in like Damien's Bexus, so not to solicit from standstill = less torque stress... Planning 4 'toothed wedges' between cage and planet gears to lock them up. Will see what 3D printing comes up with

Surely you can just MIG weld the ring gear to the planets, with gusset plates if necessary?

xp677 wrote: ↑Sat May 09, 2020 11:18 pm Surely you can just MIG weld the ring gear to the planets, with gusset plates if necessary?

Yeah, not sure why this is so difficult, Damien has already posted instructions and a 'how to' video

Jack Bauer wrote: ↑Fri Apr 24, 2020 2:40 pm Get a coded welder to tig the planet gears. Worst case you have to xray the welds once to keep them happy.

In the country of regulations, any modification requires 'certifiable proof' (documented) that mechanical integrity is maintained and will not cause premature failure - we beat Germany on rules
(Local government - "DIY is the devil - they just botch things together and cross their fingers it will work ")
We'll prove them wrong hey?

RetroZero wrote: ↑Sun May 10, 2020 7:10 am In the country of regulations, any modification requires 'certifiable proof' (documented) that mechanical integrity is maintained and will not cause premature failure - we beat Germany on rules

So, give the planet carrier to an engineering shop together with a link to Damien's video. They will give you a receipt for the welding work they do which is as much 'certifiable proof' that you will ever get or need. This really is not complicated.