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Discussion Starter #1
Has anyone got a power/rpm curve for the leaf motor (with and/or without the gear reducer). I can't seem to find one anywhere. Lots on the charging cycle but none on the power curve.
 

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There is a commonly published graph for the Leaf motor, which has efficiency as a bonus:

This comes from the ElectricVehicleWiki Drivetrain page, but it originally came from Nissan. This is a torque curve, but just multiply by speed to get power. It is for the motor by itself, so multiply torque by 7.937 and divide speed by the same ratio to get values at the axle shafts.

The power version is essentially a straight-line climb from zero (@ 0 rpm) to peak power of 80 kW (@ 2700 rpm) then constant power from there to 9800 rpm, then power falls off rapidly.

This data is based, of course, on the motor driven from the Leaf's battery and by the Leaf's inverter, with all of its control logic.
 

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... The power version is essentially a straight-line climb from zero (@ 0 rpm) to peak power of 80 kW (@ 2700 rpm) ...
That peak torque, from the graph, is about 270 Nm
Not sure where you can get 80kw from that. I'm getting 729kw (270 * 2700)
major's right:
Need to convert RPM to rad/sec.
So, the speed is
(2700 rpm)/(60 s/min) = 45 revolutions per second
(45 rev/s) * (2*pi radians/rev) = 283 rad/s

then
power is
speed * torque = (2700*2*pi/60 rad/s) * 270 Nm = 76340 W or 76 kW

Similarly, right at the top of the constant-power band:
(9800*2*pi/60 rad/s) * 80 Nm = 82 kW

or part-way along:
(6000*2*pi/60 rad/s) * 127 Nm = 80 kW

(obviously I'm not reading the chart precisely ;))
 

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Discussion Starter #6
That peak torque, from the graph, is about 270 Nm

major's right:


So, the speed is
(2700 rpm)/(60 s/min) = 45 revolutions per second
(45 rev/s) * (2*pi radians/rev) = 283 rad/s

then
power is
speed * torque = (2700*2*pi/60 rad/s) * 270 Nm = 76340 W or 76 kW

Similarly, right at the top of the constant-power band:
(9800*2*pi/60 rad/s) * 80 Nm = 82 kW

or part-way along:
(6000*2*pi/60 rad/s) * 127 Nm = 80 kW

(obviously I'm not reading the chart precisely ;))
Ahhhh, very good. A lot of things for my small tired brain to remember, haha, but I shall try. There does seem to be quite an inefficient spot anywhere below 2000rpm. I guess you just put up with it, no choice.
 

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... There does seem to be quite an inefficient spot anywhere below 2000rpm. I guess you just put up with it, no choice.
An area where you seldom operate for more than a second or two. How long can you produce 70kW at like 15 mph and not accelerate to a higher speed? Unless you're dragging an anchor up a steep hill, that "quite" inefficient spot (85%?) will not account for significant energy loss. I'd rather put up with it than the obvious choice lots of gearheads go to; multi ratio transmission.

major
 

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I agree that relatively little energy is used at low speeds (because it doesn't take much to keep moving at low speed, and it doesn't take long to get out of the range when you choose to accelerate), so efficiency isn't such a big deal. And the worst efficiency on the graph is about what more primitive motors do under ideal conditions.

Under 20 Nm motor torque (160 Nm wheel torque) is also not great... but again, if you're only using 13 kW to run at 100 km/h or 60 mph, it won't kill you to produce it at 85% efficiency instead of 95%.
(6500*2*pi/60 rad/s) * 20 Nm = 13 kW

Here we see why Nissian (like almost everyone else building a production EV with current technology) uses a single-speed transmission: they don't need to shift the operating point of the motor. Use a brushed DC motor and the game changes...
 

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Discussion Starter #9 (Edited)
I agree that relatively little energy is used at low speeds (because it doesn't take much to keep moving at low speed, and it doesn't take long to get out of the range when you choose to accelerate), so efficiency isn't such a big deal. And the worst efficiency on the graph is about what more primitive motors do under ideal conditions.

Under 20 Nm motor torque (160 Nm wheel torque) is also not great... but again, if you're only using 13 kW to run at 100 km/h or 60 mph, it won't kill you to produce it at 85% efficiency instead of 95%.
(6500*2*pi/60 rad/s) * 20 Nm = 13 kW

Here we see why Nissian (like almost everyone else building a production EV with current technology) uses a single-speed transmission: they don't need to shift the operating point of the motor. Use a brushed DC motor and the game changes...
In my case I am putting this in a VW Brick so, unlike my wifes Pacifica which does show me using 13kw at 100kph, I suspect I will be closer to 20kw (perhaps more) and i am wondering how this will affect the system and whether some sort of gear change would be good. Majors point about dragging an anchor up a hill brings up another question, which is.....just how strong is the gear reducer in the Leaf. No manufacturer other than Tesla promotes towing and mine is a truck after all. That said, there is a video of a Leaf towing 3 trailers carrying 3 leafs to demonstrate their self driving system. Is the reluctance to allow towing more to do with the frame than the motor components?
 

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In my case I am putting this in a VW Brick so, unlike my wifes Pacifica which does show me using 13kw at 100kph, I suspect I will be closer to 20kw (perhaps more) and i am wondering how this will affect the system...
Sure, I can see the "brick" using more than 13 kW on the highway... but that moves you up the performance chart to a more efficient operating point, so the energy consumption from the battery doesn't go up quite in proportion. Heat load in the motor is due to losses, which means input power multiplied by inefficiency (e.g. at 85% efficiency, 15% of the input power is turning into heat). At 30 Nm and around 6500 rpm (so, 20 kW) the motor efficiency is up to 92%. :)

In rough terms:
car: 13 kW at 100 km/h -> 20 Nm @ 6500 rpm @ 85% efficient, so 2.3 kW (15% of 15.3 kW input) of heat from motor
truck: 20 kW at 100 km/h -> 30 Nm @ 6500 rpm @ 92% efficient, so 1.7 kW (15% of 21.7 kW input) of heat from motor

Churning along at low load is mostly an exercise in generating heat, which is why some recent mid-engine hybrids with front electric drive disconnect the front motor at high speed. It wouldn't make sense in a battery-only EV, but does if the other wheels are driven mechanically by an engine.

... wondering how this will affect the system and whether some sort of gear change would be good.
Up at highway speeds, the same power is available regardless of engine speed, as long as you don't to past 9,800 rpm. That means that a moderate change in gearing won't make any difference to the power (or torque) to the wheels. If you gear lower (more reduction) or use tires of smaller rolling radius, the torque available at low speeds (below 2700 rpm) will improve, but do you need that?

I wouldn't consider smaller tire diameter, mostly because this is a truck.

Majors point about dragging an anchor up a hill brings up another question, which is.....just how strong is the gear reducer in the Leaf. No manufacturer other than Tesla promotes towing and mine is a truck after all. That said, there is a video of a Leaf towing 3 trailers carrying 3 leafs to demonstrate their self driving system. Is the reluctance to allow towing more to do with the frame than the motor components?
Although the Leaf is probably a Versa structurally, and a Versa isn't a heavy-duty vehicle, I doubt that structure is the towing concern. Although the rear suspension doesn't have a lot of spare load capacity, I doubt that's the biggest concern with towing, either (and isn't relevant to the use of a Leaf powertrain or even front suspension in the VW truck). The big constraint is probably that continual high power demand is an overheating concern for the motor, battery, and electronics.

The gearbox is really simple. It will be designed to handle the motor's torque. Handling high torque continually should just be a matter of keeping it cool enough. That might call for circulating oil through a cooler, but simple gear transmissions like this, with no clutches or hydrodynamic components (such as a torque converter) rarely need an external cooler. You'll see a cooler occasionally on a race car's rear axle, but that's due to hypoid gearing and the clutches of limited-slip differentials, neither of which are found in the Leaf.

I'm not disregarding the importance of adequate hardware for the job; I'm just saying that the Leaf motor shouldn't have enough power or torque to hurt the Leaf gearbox, given adequate lubrication and cooling.
 

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Unless someone beats me to it, I can post pics of the gears from a 2015 tonight. I have mine torn apart and all three gears are available to look at.
Excellent! :)

By the way, I believe that you'll find that there are four gears, on three shafts. The intermediate shaft has two separate gears, one meshed with a gear on the input (motor) shaft, and a smaller-diameter and wider one meshed with the big ring gear on the final output (axle) shaft. The intermediate is not just an idler gear, it is a transmission shaft just like the output shaft of the transmission section of a normal multi-speed manual transaxle, transmitting torque from the first pair of gears to the second.

The whole thing is like the complete transaxle of a transverse-engine car, but missing stuff it doesn't need:
  • the clutch
  • the reverse gear set including idler gear
  • the gears for all speeds except for one (about second gear)
  • all of the syncros and shift forks
 

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Discussion Starter #14 (Edited)
Sure, I can see the "brick" using more than 13 kW on the highway... but that moves you up the performance chart to a more efficient operating point, so the energy consumption from the battery doesn't go up quite in proportion. Heat load in the motor is due to losses, which means input power multiplied by inefficiency (e.g. at 85% efficiency, 15% of the input power is turning into heat). At 30 Nm and around 6500 rpm (so, 20 kW) the motor efficiency is up to 92%. :)

In rough terms:
car: 13 kW at 100 km/h -> 20 Nm @ 6500 rpm @ 85% efficient, so 2.3 kW (15% of 15.3 kW input) of heat from motor
truck: 20 kW at 100 km/h -> 30 Nm @ 6500 rpm @ 92% efficient, so 1.7 kW (15% of 21.7 kW input) of heat from motor

Churning along at low load is mostly an exercise in generating heat, which is why some recent mid-engine hybrids with front electric drive disconnect the front motor at high speed. It wouldn't make sense in a battery-only EV, but does if the other wheels are driven mechanically by an engine.


Up at highway speeds, the same power is available regardless of engine speed, as long as you don't to past 9,800 rpm. That means that a moderate change in gearing won't make any difference to the power (or torque) to the wheels. If you gear lower (more reduction) or use tires of smaller rolling radius, the torque available at low speeds (below 2700 rpm) will improve, but do you need that?

I wouldn't consider smaller tire diameter, mostly because this is a truck.


Although the Leaf is probably a Versa structurally, and a Versa isn't a heavy-duty vehicle, I doubt that structure is the towing concern. Although the rear suspension doesn't have a lot of spare load capacity, I doubt that's the biggest concern with towing, either (and isn't relevant to the use of a Leaf powertrain or even front suspension in the VW truck). The big constraint is probably that continual high power demand is an overheating concern for the motor, battery, and electronics.

The gearbox is really simple. It will be designed to handle the motor's torque. Handling high torque continually should just be a matter of keeping it cool enough. That might call for circulating oil through a cooler, but simple gear transmissions like this, with no clutches or hydrodynamic components (such as a torque converter) rarely need an external cooler. You'll see a cooler occasionally on a race car's rear axle, but that's due to hypoid gearing and the clutches of limited-slip differentials, neither of which are found in the Leaf.

I'm not disregarding the importance of adequate hardware for the job; I'm just saying that the Leaf motor shouldn't have enough power or torque to hurt the Leaf gearbox, given adequate lubrication and cooling.
Heat buildup and longevity is my concern. Luckily there is a generous rad available to keep the motor and converter cool. I have to check but didn't think there were ports on the reducer. The port size is only 18mm? so the flow rate seems to be low and I know the head loss will be higher than an ICE as it is cooling electronics. I didn't get the cooling pump with the system so that is another thing to work on.

I'm getting more and more pumped about this project as time goes on. I have $5k into the project and the battery is the only BIG expense left although the little thing can add up. Everything you and others are saying lets me believe that, although it is not a Tesla motor, it is still an acceptable motor for the task......as long as I don't let out the magic smoke.
 

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Discussion Starter #15
Excellent! :)

By the way, I believe that you'll find that there are four gears, on three shafts. The intermediate shaft has two separate gears, one meshed with a gear on the input (motor) shaft, and a smaller-diameter and wider one meshed with the big ring gear on the final output (axle) shaft. The intermediate is not just an idler gear, it is a transmission shaft just like the output shaft of the transmission section of a normal multi-speed manual transaxle, transmitting torque from the first pair of gears to the second.

The whole thing is like the complete transaxle of a transverse-engine car, but missing stuff it doesn't need:
  • the clutch
  • the reverse gear set including idler gear
  • the gears for all speeds except for one (about second gear)
  • all of the syncros and shift forks
Still waiting for Dedlast....hint, hint
 

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Sorry, it was a busy night last night. For refference, the output gear is about 8 inches in diameter and the foot is a US 10.5.
I have the transaxle taken apart because I only want the input shaft and that section of the housing.
And I just realized that the input shaft is the wrong way around. It should be facing the other direction so the parking ring sits over the output gear of the middle shaft.

B
 

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Discussion Starter #17
Sorry, it was a busy night last night. For refference, the output gear is about 8 inches in diameter and the foot is a US 10.5.
I have the transaxle taken apart because I only want the input shaft and that section of the housing.
And I just realized that the input shaft is the wrong way around. It should be facing the other direction so the parking ring sits over the output gear of the middle shaft.

B
I think I need to get one to take apart too. I won't mess with the one on the motor. I would like to see how to change the overall ratio from 8:1 to 3:1 for a different project.
 
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