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This is exciting, Chris tweeted today;

"Check out the inside of the small tesla drive unit. We got the gear box apart and now offer an ATB limited slip differential replacement. Get in contact today to purchase yours be one of the first in the world! "

https://twitter.com/zeroevuk/status/988538706255581184
 

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The images appear to show both front and rear drive units, which are reversed left-to-right relative to each other (because the front motor is on the car's right hand side, but the rear motor is on the left hand side). The first one (from the Tweet) would be a front unit; in the second photo it would be a rear unit on the left and a front unit on the right. Correct?

In both cases, there appears to be a pump, driven by the ring gear, in the bottom of each case. The rear unit also appears to have a fluid pipe connecting to passages in the case at the hose from the pump and to the motor bearing area. Are these lubricant pumps? Am I correct in assuming that they only function appropriately for continuous operation in the normal forward driving direction of rotation?
 

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Nice job Chris! We are very happy with the Quaife unit in our Tesla Cobra EV race car. We can lay down two perfectly matched black strips from a standing start (hillclimb) or put the power down quickly coming out of turns on road race courses.

We haven't had much success in cooling the large Model S motor yet, so we may end up running dual motors at some point in the future and will definitely be a customer for one of your units. Splitting the power between 2 motors should help the cooling situation.
 

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Nice job Chris! We are very happy with the Quaife unit in our Tesla Cobra EV race car. We can lay down two perfectly matched black strips from a standing start (hillclimb) or put the power down quickly coming out of turns on road race courses.

We haven't had much success in cooling the large Model S motor yet, so we may end up running dual motors at some point in the future and will definitely be a customer for one of your units. Splitting the power between 2 motors should help the cooling situation.


I have come up with a coolant mod for the large drive unit that spilts the motor and inverter onto different coolant loops I will be trying it in my skyline build and in 3 stunt cars I am about to build. Drop me a message to [email protected] and I will share my finding once I have tested it will be able to provide you with a kit that you weld on/ in .


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The images appear to show both front and rear drive units, which are reversed left-to-right relative to each other (because the front motor is on the car's right hand side, but the rear motor is on the left hand side). The first one (from the Tweet) would be a front unit; in the second photo it would be a rear unit on the left and a front unit on the right. Correct?



In both cases, there appears to be a pump, driven by the ring gear, in the bottom of each case. The rear unit also appears to have a fluid pipe connecting to passages in the case at the hose from the pump and to the motor bearing area. Are these lubricant pumps? Am I correct in assuming that they only function appropriately for continuous operation in the normal forward driving direction of rotation?


Yep your correct that is a front and a rear.

The pump sends oil into the motor housing though the heat sink that is liquid cooled. So all the windings and bearing are submerged in oil.


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Yep your correct that is a front and a rear.

The pump sends oil into the motor housing though the heat sink that is liquid cooled. So all the windings and bearing are submerged in oil.
Thanks Chris. :)

So the liquid-cooled motor is actually motor -> oil -> water cooled... the stator's heat is transferred first to the gear oil, then from the oil to the (water-glycol) coolant? That would make that little pump in the gearbox critical to motor cooling, and might explain some of the difficulty with cooling the motor under sustained high load.


For those not so familiar with thermodynamics: oil is a poor coolant (compared to water) because it has a low heat capacity, which means that for a given mass of oil and amount of heat, the temperature rise to absorb that heat is high. Oil is only used for cooling when water won't work (such as in a transformer) or when there is oil there anyway and high cooling performance is not needed.
 

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Thanks Chris. :)

So the liquid-cooled motor is actually motor -> oil -> water cooled... the stator's heat is transferred first to the gear oil, then from the oil to the (water-glycol) coolant? That would make that little pump in the gearbox critical to motor cooling, and might explain some of the difficulty with cooling the motor under sustained high load.


For those not so familiar with thermodynamics: oil is a poor coolant (compared to water) because it has a low heat capacity, which means that for a given mass of oil and amount of heat, the temperature rise to absorb that heat is high. Oil is only used for cooling when water won't work (such as in a transformer) or when there is oil there anyway and high cooling performance is not needed.
Exactly. Localized nucleate boiling is a major factor that makes water a far superior coolant.


Could there be a way to run a small aluminum tube with turbulators filled with water coolant through the rotor in order to cool the oil while it is still in the rotor?

 

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From my point of view the way tesla have done it is brilliant. As with the large drive unit the coolant goes though the motor then through the inverter which causes big problems as the motor is happy up to 185 degrees yet the inverter is only happy to 85 degrees there for when under load the inverter over heats very quickly due to the motor heating the coolant up before entering the inverter.

Where as with the small drive unit the coolant loop is the same system but splits on the drive unit so goes through the inverter and the motor heat sink at the same time meaning the motor temp does not over heat the inverter and because it’s a heat sink and oil cooling for the motor the temperature allowing the cooling to efficiently cool the inverter and then only cool the motor a small amount due to the heat sink and oil temp transfer rate so I think the motor would be running at 50 degrees hotter than the inverter which is not a problem.

Hope that makes sense


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Could there be a way to run a small aluminum tube with turbulators filled with water coolant through the rotor in order to cool the oil while it is still in the rotor? [IMG said:
http://www.usa.brauntechnologies.com/enhancement-devices/wrapped-cores[/IMG]
I just don't see that helping - water is about twice the heat capacity of oil so you would be better just flowing the oil faster than sticking tubes down the holes and restricting the flow
 

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If more cooling is required for the motor side I would just fit a larger heat exchanger as you can unbolt it very easily
A great potential improvement, but the oil loop is a still a critical part of the chain. Changing the heat exchanger does not change the heat transfer from motor to oil, except by lowering the cold-side oil temperature.

Since the oil pump is mechanically driven (in a single-speed gearbox), the pump speed is directly proportional to wheel speed. The gearing is chosen to avoid excessive pump speed at the car's upper speed limit, and so it is turning very slowly (relative to what the pump can handle) at normal speeds. If the oil loop's cooling capacity is inadequate for high-performance use, an electric oil pump replacing or in parallel with the mechanical pump could be the solution.
 

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As long as there is space in the case, it looks pretty easy to T the lines for an electric pump in parallel with the mechanical, no?
Yes, it looks like that to me, too, but space is likely an issue and getting lines through the transmission case would not be trivial. Any external pump paralleled with the stock pump would need a check valve to avoid bypassing flow when it is not pumping (it would not be needed at high road speed).
 

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Hi Guys
You have an oil cooling loop and a water cooling loop and a radiator

This sounds like a problem that Cummins had with the engine test system at our High Horsepower plant in Northalerton

This plant was set up with the cooling water going straight to the cooling tower

We had problems with the system overheating - despite having the same amount of cooling as the other plants

What I found was that the other plants used a "Hot well" and a "Cold well"
The cooling tower operated continuously to cool water from the Hot well and return it to the Cold well
The engine test would draw water from the Cold Well and return it to the hot well

This means that you get to use the full capacity of the cooling tower all the time - not just when the engine test is running full bore

So for your system I would recomend

The oil loop - you want an electric pump running at a high level all the time - I would probably remove the mechanical pump as it will limit how much oil you can pump with the electric pump at high speeds which means that it will reduce the amount of oil that you can circulate at low speeds - don't skimp on the oil but don't have too much

The water loop - add some extra capacity (water has a great thermal mass) and run the coolant pump all the time

The problem with the Cummins plant was that they only got coolant flow through the cooling towers when the test cells were running

I got them to add a couple of big concrete tanks as a Hot Well and a Cold Well and the overheating problems went away because they could run the coolant towers all the time
 
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