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Tesla LDU drive shaft conversion

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#21 ·
We need to hear it from the man himself.
How was the 5700rpm calculated? It would be nice to know the gear reduction ratio that’s being used.



Roadstercycle said:
I don't use chain and sprockets for this reduction. It is a helical gear reduction. The gears are good for over 600 HP. I'm building this to test the housing, bearings and external oil pump for spraying the bearings similar to the model 3 setup but my own design.
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#22 ·
Bowser330 said:
How was the 5700rpm calculated? It would be nice to know the gear reduction ratio that’s being used.
Click to expand...
The Tesla Model S LDU has a 25-tooth gear on the motor shaft driving a 78-tooth gear on the intermediate shaft. If these gears are being used, the reduction ratio is then 78:25, which is 3.12:1.
Prof. John Kelly's teardown video (@9:30)

If the ratio is 3.12:1, then 5700 RPM shaft output would correspond to 17,784 RPM. Since the P100D motor speed has been listed as 18,000 RPM, this ratio is at least close to correct... and likely exactly correct because those original equipment Tesla gears are being used.
 
#23 ·
brian_ said:
The Tesla Model S LDU has a 25-tooth gear on the motor shaft driving a 78-tooth gear on the intermediate shaft. If these gears are being used, the reduction ratio is then 78:25, which is 3.12:1.
Prof. John Kelly's teardown video (@9:30)

If the ratio is 3.12:1, then 5700 RPM shaft output would correspond to 17,784 RPM. Since the P100D motor speed has been listed as 18,000 RPM, this ratio is at least close to correct... and likely exactly correct because those original equipment Tesla gears are being used.
Click to expand...
Thank you that’s great work, much appreciated.

Something close to 3:1 is perfect, I was thinking of putting a Tesla motor in-line with a driveshaft of a car or truck and the current offering of 4.5:1 is too much! because the final drive is 2.93 on the car so 4.5 x 2.93 = 13.19, which is 113mph with a 28” tire. Could exceed this momentarily and damage the electric motor.

3.12 is muuuch better 3.12 x 2.93 = 9.14 which is slightly less than the standard oem 9.73. 9.14 at 18k rpm is 164mph with a 28” tire and much more logical for a performance car speed window.

I am guessing I would have to connect the 3.12 yoke from the motor and connect it to a differential (at 1:1) that is inline with the cars driveshaft.
 
#24 · (Edited)
The motor max speed is a whole lot less important than the rpm at which field weakening begins. You don't want your cruise speed to be using FW or your efficiency will drop quite a bit, as will the steady-state power of the motor. LDU is a bit over 8krpm
 
#25 ·
^^ Your post is very confusing.

The Tesla motor spins way too fast. It needs a gear reduction. That motor + reducer takes it to 3.12:1.

The yoke connects to the driveshaft and the driveshaft connects to the diff pinion input. That's not "1:1", it's a driveshaft. The diff has a 2.93:1 reduction to the axles.

There isn't a 1:1 gearcase anywhere.

You're also not going to exceed anything "momentarily". Top speed is governed. On the Bolt EV it's 93. Leaf is 89.5 mph. No reason to go faster in the USA.
 
#26 ·
Sorry I didn’t clarify, I want to add the Tesla motor to an existing ice car to make a hybrid.

So I would not just connect the yoke to the drive shaft and run it to a diff, that’s what I would do for an ev, not a hybrid. I need to put the e-motor inline with the ice run drive shaft so the e motor provides acceleration assist.


remy_martian said:
^^ Your post is very confusing.

The Tesla motor spins way too fast. It needs a gear reduction. That motor + reducer takes it to 3.12:1.

The yoke connects to the driveshaft and the driveshaft connects to the diff pinion input. That's not "1:1", it's a driveshaft. The diff has a 2.93:1 reduction to the axles.

There isn't a 1:1 gearcase anywhere.

You're also not going to exceed anything "momentarily". Top speed is governed. On the Bolt EV it's 93. Leaf is 89.5 mph. No reason to go faster in the USA.
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#27 ·
Great point and the 8000rpm speed at 9.1:1 would be about 879 wheel rpm and with a 28” wheel that would be 73mph, which would be around my primary cruising highway speed, perfect.

57Chevy said:
The motor max speed is a whole lot less important than the rpm at which field weakening begins. You don't want your cruise speed to be using FW or your efficiency will drop quite a bit, as will the steady-state power of the motor. LDU is a bit over 8krpm
View attachment 125709
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#28 ·
But you keep saying Tesla motor and inline. That's not supported by OP's gearbox, is it?

How do you think you'll run the power path through this overpowered, underbatteried, hybrid? Why a Tesla motor?
 
#29 ·
Bowser330 said:
Something close to 3:1 is perfect, I was thinking of putting a Tesla motor in-line with a driveshaft of a car or truck and the current offering of 4.5:1 is too much! because the final drive is 2.93 on the car so 4.5 x 2.93 = 13.19, which is 113mph with a 28” tire. Could exceed this momentarily and damage the electric motor.

3.12 is muuuch better 3.12 x 2.93 = 9.14 which is slightly less than the standard oem 9.73. 9.14 at 18k rpm is 164mph with a 28” tire and much more logical for a performance car speed window.
Click to expand...
The 4.5:1 gearing set is offered for people who want to have two outputs, to front and rear axles in a 4WD vehicle, using the Tesla transaxle as both reduction gearbox and front-rear power splitter ("transfer case"). While the 4.5:1 ratio is probably as tall as they could arrange while changing only one of the two gearing stages, it also works out for the Land Rovers for which it was intended.

Bowser330 said:
I am guessing I would have to connect the 3.12 yoke from the motor and connect it to a differential (at 1:1) that is inline with the cars driveshaft.
Click to expand...
The way Roadstercycle's system is intended to be used, you just run one shaft from the output of his 3.12:1 gearbox to your axle or IRS final drive (which in your example has a set of 2.93:1 ring-and-pinion gears in it). No other gear reduction, so 1:1.
 
#30 ·
remy_martian said:
But you keep saying Tesla motor and inline. That's not supported by OP's gearbox, is it?

How do you think you'll run the power path through this overpowered, underbatteried, hybrid? Why a Tesla motor?
Click to expand...
No, it's not readily supported. A transfer case in high range (direct) could be used, but that's a lot of hardware.

An alternative would be to use the whole Tesla transaxle with the available 4.5:1 gearing and a spool replacing the differential, feeding the transmission output to one side of the Tesla transaxle and taking the combined drive from the other side to the axle/final drive. This is a large pile of hardware, so it would only be suitable in a relatively large vehicle... and one that needs such a large motor in a hybrid configuration.
 
Discussion starter · #31 ·
Wow, I have not logged in a bit. So here's some answers. The output is a 3.12 ratio and the diff is a 3.55 so we end up with an 11:07 final drive, great for quick 1/8 mile and rally cross but not high speed. The car was built to test the feasibility of doing this with drive shaft setups in older Mustang and Camaro builds. So far so good but I'm being driven crazy by the gearbox oil pump whine. Any thoughts on that would be appreciated for sure. I'm using a gear pump which are really noisy. I just put 2 new videos up on YouTube with the Tesla under glass Rabbit build and my latest Mustang build with the Model 3 motor. Here's the links.


 
#32 ·
Dug late in to this one & not sure if there's a newer post with updated info, but I really like this as a possible option for my '68 camaro built... I have a Roadster Shop chassis & a Read Deal Steel body, so basically building a Camaro from scratch with a full frame and very interested in this way of utilizing the Tesla setup... If there's another post I missed, I apologize. I'll keep digging! :)
 
#33 ·
I'm guessing few here know what a Roadster Shop chassis is and people are too busy to go research information you already have.

For starters...

Does it have IRS? What's the inner spacing of the frame rails? What's the track width? Are you willing to flare or tub the body? "the Tesla setup"...which one? What do you want out of the car by doing this?

Take a look @428RC's Corvette thread to see what kind of PITA it might be to squeeze a Tesla LDU (one of many "Tesla setups") into a custom frame.

Also pick up a copy of May 2022 Hot Rod magazine to see what GM is about to launch, which might work better for your application than a Tesla DU. They electrify a 57 Chevy with the GM factory team involved who want to launch a "crate motor"
 
#34 ·
The Roadster Shop SPEC chassis (likely the one already purchased) has a beam rear axle with parallel lower and angled upper control arms. Although no single detail is the same as a the stock 1968 Camaro, it is designed to use a stock body and stock-style (or more likely more modern equivalents) powertrain (engine and transmission). The problem with using it for a conversion will be finding somewhere to put the battery.

This thread is about adapting a Tesla motor to be placed longitudinally, driving a remote axle, which could work with the stock Camaro layout. The obvious alternative is to use an entire EV (Tesla or otherwise) drive unit at the rear axle, with an independent suspension instead of the beam axle. That would leave the entire engine compartment for battery, but of course mechanically it's bigger project (due to the required IRS), and it would require body floor modifications (which the RS chassis carefully avoids). The frame rails of the custom chassis are widely spaced (because of the design for a beam axle which is good for fitting in the width of a drive unit, but will be in the way of most IRS.

The Roadster Shop Fast Track chassis is available with IRS. The IRS design (which likely uses C7 Corvette parts) has relatively short arms and widely spaced frame rails (although not as wide as with the beam axle), so it might be a reasonable basis for build with a complete EV drive unit in the rear. The bolted-in rear subframe or crossmembers would need to greatly modified, or completely replaced.
 
#35 ·
brian_ said:
The Roadster Shop SPEC chassis (likely the one already purchased) has a beam rear axle with parallel lower and angled upper control arms. Although no single detail is the same as a the stock 1968 Camaro, it is designed to use a stock body and stock-style (or more likely more modern equivalents) powertrain (engine and transmission). The problem with using it for a conversion will be finding somewhere to put the battery.

This thread is about adapting a Tesla motor to be placed longitudinally, driving a remote axle, which could work with the stock Camaro layout. The obvious alternative is to use an entire EV (Tesla or otherwise) drive unit at the rear axle, with an independent suspension instead of the beam axle. That would leave the entire engine compartment for battery, but of course mechanically it's bigger project (due to the required IRS), and it would require body floor modifications (which the RS chassis carefully avoids). The frame rails of the custom chassis are widely spaced (because of the design for a beam axle which is good for fitting in the width of a drive unit, but will be in the way of most IRS.

The Roadster Shop Fast Track chassis is available with IRS. The IRS design (which likely uses C7 Corvette parts) has relatively short arms and widely spaced frame rails (although not as wide as with the beam axle), so it might be a reasonable basis for build with a complete EV drive unit in the rear. The bolted-in rear subframe or crossmembers would need to greatly modified, or completely replaced.
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You're correct, Brian... I would be interested in utilizing this as a way to place the motor unit in a traditional motor placement (or maybe where the Transmission would be- I have to cut the body tunnel for a T56 Magnum if I went a fossil route anyway) & run a full driveshaft. Building out the batteries around it in the engine compartment, then in place of the fuel tank. Just an interesting option. No desire to chop of the RS chassis... more mentioned because it would be great for torque management vs. just a unibody with subframe connectors.
 
#37 ·
#38 ·
#39 ·
Clearly window dressing for their in-house conversion business at that quoted price. At the low end of $25k in the article, it would be painful but perhaps tolerable given the price of a supercharged crate ICE & transmission.

In any case, cat's out of the bag on the packaging., which I really like..someone here might run with it.
 
Discussion starter · #40 ·
I don't think you could ever get one for $25,000, I've been hearing closer to $35,000 at the base model setup. Don't quote me as I heard it through the EV grapevine.
 
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