Carbon wrapped rotor motor…

[JBee]

Welll he said 2000 lbs. Maybe he meant kg. If its 2000 kg then double all my numbers. It did strike me a bit light. Or I have wax in my ears or on my brain. Checked the video. He said "2 ton" which is 2000 kg. I'll go back and fix it.

No worries.

On the subject of numbers I wonder at what rpm a copper rotor with about 150mm diameter would start coming apart from centripetal forces? Ie one without a CF wrap? I'm wondering if a PM can be built without a CF wrap for 20k rpm, because that would give another arguement for a CRIM.

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[Crissa]

The Plaid is a Tri motor. I wonder if all motors are CRIMs? Dual motor Model S has IM and PMSM.

Yeah, I wonder, too. But as you note, they use mixed motors in the Dual Motor S for efficiency.

-Crissa

 

[TruckElectric]

Yeah, I wonder, too. But as you note, they use mixed motors in the Dual Motor S for efficiency.

-Crissa

It would be my guess that having 2 advanced carbon-wrapped CRIMs on the rear would be sufficient for the speed and a PMSM, PMSRM, or switched reluctance motor for efficiency for the front motor.

 

[Jhodgesatmb]

Welll he said 2000 lbs. Maybe he meant kg. If its 2000 kg then double all my numbers. It did strike me a bit light. Or I have wax in my ears or on my brain. Checked the video. He said "2 ton" which is 2000 kg. I'll go back and fix it.

2 tons = 4,000 lbs weight and is not a mass. Ton is an imperial unit. Tonne would be KG. So 2 tonnes would be 4,000 kg weight. I am assuming that you are using metric units for these calculations but lets try to be consistent with the units and quantities.

 

[ajdelange]

On the subject of numbers I wonder at what rpm a copper rotor with about 150mm diameter would start coming apart from centripetal forces? Ie one without a CF wrap? I'm wondering if a PM can be built without a CF wrap for 20k rpm, because that would give another arguement for a CRIM.

Don't know how up to speed you are on the math but the force a mass m is subject to is w^2*r*m/2 in which r is the radius and w is the angular speed in radiand/sec. w = 2*pi*rpm/60

 

[ajdelange]

It would be my guess that having 2 advanced carbon-wrapped CRIMs on the rear would be sufficient for the speed and a PMSM, PMSRM, or switched reluctance motor for efficiency for the front motor.

The CRIMs are going to be lighter (more HP/kg), cheaper, smaller and possibly more efficient than PMSRMs all because of the high rotor speed. I'm guessing it will be CRIMs all around.

 

[TruckElectric]

The CRIMs are going to be lighter (more HP/kg), cheaper, smaller and possibly more efficient than PMSRMs all because of the high rotor speed. I'm guessing it will be CRIMs all around.

So maybe advance carbon-wrapped CRIM's on the tri-motor Cybertruck? ? ?

 

[Diehard]

So maybe advance carbon-wrapped CRIM's on the tri-motor Cybertruck? ? ?

European union will have all cars sold after next summer equipped with Intelligent Speed Assist (ISA) making sure Europeans don't have too much fun on the road by keeping their speed under speed limit. If the regulation makes it's way across the pond, CT3 owners may not get as much out of their carbon-wrapped motors. We will be missing the time when our cars did what we told them to do.

 

[ajdelange]

2 tons = 4,000 lbs weight and is not a mass.

Yes, actually it is. An Imperial ton is 2000 lbs-mass equivalent to 909 kg. So 2 Imperial tons is 1818 kg or 4000 lbs mass.

Tonne would be KG. So 2 tonnes would be 4,000 kg weight.

A metric tonne is 1000 kg mass equivalent to 2200 lbs-mass. Two tonnes would be 2000 kg or 4400 lbs mass.

So whether he meant 2 tons or 2 tonnes its about 2000 kg.

I am assuming that you are using metric units for these calculations

Yes. N, m, m/s, m/s/s, W, are all SI units. As the chart is in Imperial units I had to convert HP to kW and mph to m/s.

but lets try to be consistent with the units and quantities.

I made a mistake. Let's try not to make it worse.

 

[JBee]

European union will have all cars sold after next summer equipped with Intelligent Speed Assist (ISA) making sure Europeans don't have too much fun on the road by keeping their speed under speed limit. If the regulation makes it's way across the pond, CT3 owners may not get as much out of their carbon-wrapped motors. We will be missing the time when our cars did what we told them to do.

That would just make acceleration even more important though?

ISA must be fitted but can be turned off after the vehicle has started. It also allows for manual accelerator overide. Think of it as a assistant rather than an inhibitor.

Besides I don't think Germany will give up open speed limits on Autobahns anytime soon. Even most other EU countries are fairly "flexible" with speed limits depending on where and when (ie not universally enforced)especially on highways out of town.

 

[Mini2nut]

I’m simply amazed that the Plaid can do 200mph from a single speed speed gearbox.

 

[ajdelange]

That's the blessing of high rotor speed and an ideal torque vs speed curve.

 

[JBee]

Don't know how up to speed you are on the math but the force a mass m is subject to is w^2*r*m/2 in which r is the radius and w is the angular speed in radiand/sec. w = 2*pi*rpm/60

I was sort of hoping you'd do the math because it seems you are good at it and like doing it
My forte seems being verbose and most people ignoring my long posts

BTW Plaid wheel is a 265/35 ZR21 with 719mm diameter and 2.258m circumference. So we get 141,718 revolutions at 320kmh (200mph) which is 2,361 RPM which means if the motor is doing 20,000rpm at 200mph we end up with a final motor to wheel drive ratio of 8.47.

Also on the battery front EM has already confirmed in a tweet that the MY that will produced in Austin will start with the 4680 cell pack. It stands to reason that the CT will also have 4680s seeing they will be available for the MY. My argument for that is that they won't want to make two different structural pack types and assembly lines if they want to keep the cost down. That might mean that the CT is cell supply restricted though.

In fact if there's a structural pack in the CT, I'd say they'd have to reduce the exoskeleton frame because of it, which means it will become a necessity to have a structural pack in the CT. There's no benefit in a structural pack if the vehicle is designed to work without one.

Overall I can't really see a CT with anything but 4680, the cost of switching things up all the time would be better invested in making the 4680 work. Same reason why there's a gigapress for the MY in Austin, all those MY will be built one way, with castings, to reduce overheads.

 

[TECHNOMAGE]

The high rotor speed is desired in the CT too as it implies greater efficiency. No, the CT won't have the same top speed but whatever its top speed is it will be at 20,000 rpm. The motor will just be geared down more for the lower CT top speed.

I think Elon said or implied that carbon wrapped motors had better efficiency. Why? Mebbe there is some electromagnetic magic going on besides closer clearances.
That custom carbon wrapped business has gotta add $$$ to cost. If that and some other extra cost features make the CT into an "extreme range" vehicle with "bolt in" motors and some other PLAID parts, fine, but at the moment I don't have a need. Bet those will be modular motors just like Prof Kelly describes in his Tesla Model 3's MOdular motors with many common parts between front and back motors
See video:

 

[ajdelange]

I think Elon said or implied that carbon wrapped motors had better efficiency. Why?

Torque is proportional to stator current and power proportional to the product of rotor rpm and torque. Thus a motor that turns faster can produce the same power as one that turns slower with less stator current. Stator loss is proportional to the square of stator current. Thus the faster spinning motor produces the same power with less loss and is more efficient. QED

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