Electric tractor

[aczlan]

But your entire frame of reference is an internal combustion engine! Electric motors, especially 3-phase electric motors with the proper controllers, are much more versatile than a variable displacement pump on a hydrostatic drive.. A Tesla Model S weighs about 5K lbs., not a "light weight" by any means, and can accelerate that mass to sixty mph from a dead stop in under three seconds. And still go 155. So it has the grunt down low, does it not? Now gear it down 5:1, add some weight [perhaps more batteries!] to bring it to six or seven thousand pounds, a good mid-sized tractor, and you have serious pulling power, and still more speed than you'd want.
I'd buy that for $50K, maybe $60K.

If you look at a modern manlift, they have electric motors for propulsion and a hydraulic pump to run the steering and lift cylinders. They have more power than the old hydraulic drive ones used to and the battery holds up much better.
If you're doing it on a tractor, you could put a wheel motor on each of the front wheels and eliminate all the complications of the four-wheel drive front axle. You would just need to add a second motor controller or use properly wound motors so that they spun at the same rate of speed as the back ones.

Aaron Z

 

[John_Mc]

Elec-Trak - Wikipedia

My father was one of the electrical-mechanical engineers involved with the development of these tractors. Unfortunately, he, like most of the people who worked for GE on these, are all dead today.

My brother had one of those. They were before their time. With today's batteries and controls, it would be interesting to see how it operated. There are a couple of active user's groups on the internet.

This reminds me... I have one of the 36v electric chainsaws that was designed to plug in to the Elec-trak. I was going to give it to my brother, but he sold the Elec-Trak before I could give it to him.

 

[buickanddeere]

The electric motor should be spinning in the thousands of rpm when under full load instead of hundreds of rpm.

 

[CincyFlyer]

The electric motor should be spinning in the thousands of rpm when under full load instead of hundreds of rpm.

It depends on its current [ha!] task at the time; a Tesla Model S will hammer a Corvette off the line, starting a zero rpm on the motor. The torque curve is backwards on most electric motors.

 

[buickanddeere]

But your entire frame of reference is an internal combustion engine! Electric motors, especially 3-phase electric motors with the proper controllers, are much more versatile than a variable displacement pump on a hydrostatic drive.. A Tesla Model S weighs about 5K lbs., not a "light weight" by any means, and can accelerate that mass to sixty mph from a dead stop in under three seconds. And still go 155. So it has the grunt down low, does it not? Now gear it down 5:1, add some weight [perhaps more batteries!] to bring it to six or seven thousand pounds, a good mid-sized tractor, and you have serious pulling power, and still more speed than you'd want.
I'd buy that for $50K, maybe $60K.

Three phase motor or not. Electric motors have a bell curve where they operate most efficiently . At low rpms there is less cooling airflow and the magnetic flux is at or near max, this is not an ideal region to operate in due to the losses.
If you can't understand this, think of a 10 speed bicycle using only the middle gear vs using all the gears as required The rider is going to cover more distance , faster with less effort, wear and tear.
EV's are parasite loss sensitive and eliminating a gearbox and the associated friction is important.

 

[buickanddeere]

If you look at a modern manlift, they have electric motors for propulsion and a hydraulic pump to run the steering and lift cylinders. They have more power than the old hydraulic drive ones used to and the battery holds up much better.
If you're doing it on a tractor, you could put a wheel motor on each of the front wheels and eliminate all the complications of the four-wheel drive front axle. You would just need to add a second motor controller or use properly wound motors so that they spun at the same rate of speed as the back ones.

Aaron Z

What is the range of operation in speed and torque load for a forklift vs. a tractor vs. h i l l a r y supporting , late sipping urbanite single person on their way across town to a Green Peace meeting at the centre for the Arts.
Has no one here ever ran various types of electric motors on a Dyno and charted output in torque, rpm and HP vs input voltage, current and power ? An electric motor is not magic inside a box that does wonders when connected to the mystical black art of electricity.

 

[plowhog]

I would buy one, but only if it has a diesel engine to charge the batteries!

 

[CincyFlyer]

Three phase motor or not. Electric motors have a bell curve where they operate most efficiently . At low rpms there is less cooling airflow and the magnetic flux is at or near max, this is not an ideal region to operate in due to the losses.
If you can't understand this, think of a 10 speed bicycle using only the middle gear vs using all the gears as required The rider is going to cover more distance , faster with less effort, wear and tear.
EV's are parasite loss sensitive and eliminating a gearbox and the associated friction is important.

True. But in a tractor (say, versus a Tesla Model S) you will start with a 5:1 or more lower overall gear ratio (taking tire circumference into account). You aren't going to be constantly running the motor at stall, even if you need to creep. And your PTO can have its own motor, with that subsystem optimized for 540-1,000 RPM running, with options above and below that. So your wheel motors power only wheels. I'd save the money on a gearbox, or, at most, have two ranges, at about 2:1 ratio.
But compared to an ordinary diesel or petrol ICE, a three-phase electric motor with the proper controller will indeed appear to be magic.
The only thing that keeps this from happening on a more general basis (as opposed to specific needs, such as indoor running) is the very low energy density of today's (and yesterday's, and the near future's) battery systems.

 

[4570Man]

I've got a variable speed wood lathe that used a VFD and a 3 phase motor. The Powermatic has a better torque curve than the Jet, but they neither one make maximum torque at the bottom end RPM. And compared to my geared metal lathe the low end toque is a joke.

 

[CincyFlyer]

I've got a variable speed wood lathe that used a VFD and a 3 phase motor. The Powermatic has a better torque curve than the Jet, but they neither one make maximum torque at the bottom end RPM. And compared to my geared metal lathe the low end toque is a joke.

One cannot properly compare a wood lathe to a metal lathe! You may tap with your metal lathe, and require extremely low speeds. On a wood lathe, if you need extremely low speeds, you'd better balance that big knot or whatever you are turning! Or get a bowl lathe.