[roundrightfarm]

Greetings,
I am a vegetable farmer who wants to convert my cultivating tractor, making it both electric and remote control. Really what I'm imaging is an unmanned tractor that could be operated through video feeds from, say, up to a half mile away.

The tractor in question is an Allis Chalmers model G. (photo attached) This tractor was built in the late 40's, early 50's, as a tractor that would specialize in cultivation (aka weeding). It has a unique design, with the engine placed behind the driver, which allows them a mostly unobstructed view of the crops right in front.

It is relatively low horsepower (11hp) and well suited to become an electric tractor. In fact, others have already done this (see the video below) and a manufactured motor plate for transmission mounting and coupling is commercially available. Everyone I've seen making these conversions uses an Alltrax contoller. This design only powers the wheels with an electric motor, while the steering, brakes and implement lift are operated manually. The original transmission is still used, with the driver being able to select reverse.

I want to expand this design to also electronically control the steering, stopping, cultivator implement lift and forward-reverse gear selection. This would allow full remote control.

I'm also imagining multiple mounted cameras and video feeds that would allow forward and rear views, as well as have close-ups of the crop being cultivated for more precise cultivating. All this would require and understanding of RC and wifi, of which I have none. Are people exploring remote control in these forums?

Any advice on going forward would be appreciated- I have many questions.

1. What is the best steering design? the stock steering is very basic with the steering shaft rotating a gear box connected to tie rods to the wheels. If a motor could control the rotation of the steering wheel shaft, I think it would work

2. Can the main motor be used as a brake by creating resistance to forward motion,

3. Can reverse be created by operating in the main motor in the reverse direction?

4. Can anyone recommend some reading in general ev and/or rc design that would apply to what I'm trying to do?

here's a video of the drift shaft electric coversion:
www.youtube.com/watch?v=M0uAcA6ZvD4

 

[goingbush]

You will have Regenerative Braking and Reverse in you use an A/C motor.

you might get a steering idea here !

http://lainefamily.com/RCTractor.html

 

[Karter2]

There ought to be a law to prevent conversion of classic machines like that. !

 

[roundrightfarm]

Based on goingbush's recommendation, I've started looking into AC induction motors. I've seen some in the HP range I require (http://www.electricmotorsport.com/ev-parts/motor-drive-kits/ac-induction-motor-kits/ac-20-kit.html)

They are sold with Curtis controllers. Will the Curtis model 1236 or 1238 give me control over the drive shaft in both forward and reverse and accomplish braking/stopping with out the use of brake pads on the wheels?

I am new to this forum, so if someone could please advise me on the best place to post this thread if this is not already it, that would be appreciated. Thanks

 

[goingbush]

No, Regenerative braking will not replace friction brakes, they become less effective as you get slower, there noting to stop the vehicle with the motor off , it will roll away , you could rig it to enable reverse at very slow speed, that will pull it up quickly . I would reccomend friction brakes of some type , (or drop a tyne )

 

[roundrightfarm]

Interesting, so, if I understand correctly, the motor shaft is free-wheeling when the motor is not drawing any current? At what point will the AC motor keep the tractor from rolling...is it possible to creep forward very slowly while pointed on a steep downhill, without friction brakes?

 

[brian_]

Interesting, so, if I understand correctly, the motor shaft is free-wheeling when the motor is not drawing any current?

Yes.

At what point will the AC motor keep the tractor from rolling...is it possible to creep forward very slowly while pointed on a steep downhill, without friction brakes?

Yes, that's regenerative braking. It doesn't happen at some speed point, it happens when the controller makes it happen. It's great for slowing down, or for keeping speed from increasing during a descent, but as already mentioned it isn't effective right down to zero speed. Cars which use regenerative braking coordinate it with regular friction brakes.

 

[brian_]

There ought to be a law to prevent conversion of classic machines like that. !

I assume you're kidding, but seriously... the alternative is probably scrapping them. We can't hold on to everything forever, so other than a few machines retained in museums, they need to be adapted to a changing world or recycled. It's the same as with cars - "classic" or not, it makes no sense to keep more than a very few of them.

 

[major]

I think it may be misleading to talk about "no regen" meaning ineffective braking at low or zero speed. Certainly at very low or zero speed it is not possible to charge the battery from the kinetic energy of the moving vehicle (which is implied in "re" generative braking). But it is actually easy to produce even large amounts of braking torque, or holding torque, at low and zero speed. With a proper 4 quadrant torque controller on a motor, up to full torque in either direction is available at any speed in either direction. And with an AC motor, there is no concern producing high torque at stall (no brushes to burn) as long as it is thermally managed.

I've held heavy EVs on steep ramps using only the throttle without issue many times. I've also driven an EV programmed with forward torque command on the right pedal and reverse torque on the left pedal. Some forklifts have a wigwag type throttle pedal for forward/reverse. With proper control programming and AC drive a tractor should no problem controlling speed downhill in either direction. Obviously mechanical brakes need be retained for failsafe.

major

 

[brian_]

Excellent catch, major.

Regenerative braking (generating power) doesn't work down to zero speed, but that doesn't mean that torque in reverse to the direction of motion can't be applied. As long as you don't mind using power to slow down to even to control descent speed, then doing it all with the motor (backed up by mechanical brakes) should be practical.

A rocker pedal (toe for forward, heel for reverse) makes a lot of sense (as long as it has some deadband in the middle to avoid oscillation) - that's how a typical hydrostatic drive lawn or garden tractor is set up, and it's easy to use. Separate left and right pedals would need to be mechanically linked, or the controller would need to designed or programmed to appropriately handle both pedals being pushed at the same time.