Talking about electric tractors

I don't have time nor the inclination to read every post to the numerous threads conerning electric "tractors" so admittedly I don't know everything that was said. What I do know is that there have been electric "tractors" for years.

The first ones have long extension cords to take the power to them and typically operate in the thousands of volts range. This set up is typically used on semi-stationary machines like cranes doing dragline or shovel work in mines and quarries or similar operations. Heck Big Muskie, the largest land machine ever built was electric driven.

If your more mobile you then use a generater driven by an internal combustion engine of some type. These are often used on things like mine haul trucks, rubber tired loaders, etc. It's also the most prevailant type of power for a modern locomotive. In the "smaller" equipment range Letorneau had a scraper out back in the late '60's, early 70's that was set up this way. Nowdays the big stuff is still driven this way more often than not and right now CAT has in the plans a D7 size dozer that will be electric driven. It was premeered at the '08 Mine Expo in Vegas and was supposed to be coming out in production in '09 but with the economy who knows.

The advantages of using a an electric drive, especially on larger equipment is two fold, First the prime mover, ie the engine, can set there and run at it's optimal speed for both power and fuel economy instead of constantly speeding up and slowing down as power needs change. Secondly where the engine has to have a transmission to keep up it's speed in order to achieve the highest possible torque output to the driving wheels, an electric motor doesn't have that problem. When you throw the juice to it it almost immediately begins to produce full torque. This gives alot more power to get a large machine, say a 400+ ton haul truck weighng nearly a milion pounds, moving from a full stop to in excess of 40 MPH.

Given all the advantages of electric drive, it's a wonder we don't see more of it. Being an equipment mechanic by trade, the biggest hurdle to overcome to getting more of this type of drive on the market, in my opinion, is finding enough mechanics with the qualifications or more specifically the desire to obtain the qualification to work on the electrical systems associated with them.....But that's all just my .02 on electric tractors....

Complexity, weight, expense. Engine, generator, and drive motors. Not to mention controls capable of controling huge amounts of electricity. OK for railroad engines, probably not terribly practical for farm tractors, unless you want to give Big Bud a run for the money. Farmall tried a onboard generator on the tractor to power a haybaler. Didn't go very far.

What about the GE Electrictrac tractor? Remember those?

In 1968 while in college I worked part time for an electrical contractor and GE appliance company. GE had just developed an electric riding mower. I think it was called the Suburbia and was advertised to mow an average size lawn w/o the noise and pollution. It would charge over night. The GE district manager wanted us to promote the tractor. The owner of the company said that country people wanted to hear the engine and we wanted no part of the tractor. I don't think the production lasted a year.

Cub Cadet had an electric battery powered riding mower. Cost of battery replacement was a problem.

Allis Chalmers built a proto type fuel cell tractor, electric driven, in the early 60,s or late 50,s. I,ve got a picture of it in one of my allis books. Greg

About 40 years ago I watched an earth mover that was electric drive. It had 3 units (pans) hooked together, all wheels were electric driven. As remember it had 4 diesel generators. The advantage to that, besides only having one operator for the size of the machine was that it could fill one unit at a time with plenty of power and traction- could even back the rear unit into boggy conditions with the rest to pull it out. Would make an AWESOME farm tractor, like three 4 wheel drive tractors hooked together!

A pre production electric drive D7 was delivered to the firm my son works for in Texas.Directions use it,inspect it, but don't fix it, call Cat

Electric tractors will face the same hurdles as every other new idea... a resistance to change.
How many of us would seriously debate that carburetors are better than port fuel injection today?
I know there will be some....... but you're getting to be a precious few.
or radial tires, or.... you name it.

I read something about Deere having placed a large generator in the front of a tractor not long ago. I beleive it said the ultimate goal was having it electrically drive impliments. No more PTO's, hydraulics etc. Just electric controls. DC drives. Really quite simple.... but like anything else, it will take time. I'm sure there's going to be a few incarnations of the idea before it gets where it's going.
Opinion changes in time.
I for one would not have wanted an ECU controlled truck engine 10 years ago. Now having had one for 5 years I wouldn't go back...

Rod

US Navy in particular is designing and building electric drives. Electric drives particularly effective where quick maneuvering or multiple sources of power are to be used. Eg icebreakers, aircraft carriers and subs.
For applications where days or weeks of steady state cruising at the ships ideal hull speed. The direct drive between the engine or steam turbine's gearbox is ideal.Eg those freighters with the 102rpm 100,000HP two stroke turbo diesel.

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This is a photo from the IH archives showing the 10KW Electrall. It was constant run with a special gearbox and controlled with a field switch.

This wasn't IH's first attempt at providing an electric PTO. Wendel's "150 Years of IH" has a photo of a 10-20 with an experimental generator attached to front bolster and driven from the front of the crankshaft. There is no mention that it saw production.

This isn't new buickdeere. Navy had elecric drive subs in WWII. Anybody know why we didn't keep them?
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Inefficiency of multiple power sources and battery life. Every motor has inefficiencies so with amotor generator there is the inefficiency of the motor then the inefficieny of the drive motor.
The reason for going to elecric drive today has nothing to do with being efficient.

WWII subs didn't have steam boilers & steam driven turbine generators. They were all electric.
Now instead of duplicating and/or additional equipment inside the tight and $$$ subs. With a separate prop steam turbine, a separate electrical generator, duplicate condensers, pipework etc. and a massive drive shaft. Less noise too without a gear box and turbine on the end of the prop shaft.
Now the sub runs just one overall smaller/lighter steam turbine/electrical generator. That doesn't have to be mounted in a straight line with the prop(s). Electric bow thrusters will allow a sub to turn quickly on it's axis . Instead of ploughing in a circle over thousands of yards. Just the ticket for those tense moments.
Some cruise ships run electric drives as well. The main engines/generators still run at rated power. The ship just slows down some as the "hotel load" rises when all the ladies are using hair dryers. And the kitchen is cooking before supper. The electric props also allow the props to be steered/pivoted. Which allows easier docking of these huge ships, in small ports without $$$ tugs.
The aircraft carriers are going to electric aircraft launching for similar reasons.

LeTourneau used the system to get power at each wheel. Not so simple with mechanical drives. No differentials required.

If you read pretty mcuh any article written concerning diesel electric drive the main reason given is the increased efficiency of the combustion engine driving the generator due to it's ability to run consistently in it's "sweet spot". Imagine running your car around all day climbing a hill in second gear instead of third because the engine had enough power in second at the higher RPM but not at the lower RPM of third. Using the electric driver allows the engine to run at a constant speed all day, with only small changes in the fuel needed to handle a varying load, rather than running at a higher than needed RPM, using excessive fuel, to carry the same load.

It may not sound like it makes sense, and I'm personally no expert, but there are enough experts out there that say it works that I tend to believe it. Experts aside, given the fact that so many companies use the equipment to save on fuel tell me they wouldn't do it if it didn't save fuel and make them money. To me the almighty dollar speeks alot louder than any expert...