[JRP3]

Interesting design but maybe prone to tipping over? I wonder if a more typical two side by side drive wheel design might be better? Low speed torque is of course a DC series motor specialty, that and low cost is why I chose it for my AMPhibian project.

 

[JRP3]

I think simple and cost effective are paramount in this design. Solid axle with two wheels and chain and sprocket for gear reduction. At this speed and weight brakes are probably not needed. Steering would just be physical manhandling, I don't think you are doing much more than spinning it around at the end of a row.

 

[JRP3]

A narrow track width and moderate weight shouldn't be that hard to spin. Tip it slightly to unload the outer wheel and spin it around on the inner. The chain and sprocket design allows use and reuse of fairly standard items with minimal fab and machine work.

 

[JRP3]

Modify what you have. Don't go reinvent one. Cost is a big factor and I am sure there are plenty of very good used walk behind tractors available to modify.

That may not be the case depending on his location.

 

[JRP3]

I read that the DC series motor (is that a "universal motor") demands a lot of maintenance, especially for the brushes? But it's probably the one we need, because of its superior traction at low speeds. (Frankly, I have no clue on electric motors).

Brushes are the only real wear item, other than bearings, but should last a very long time. EV's typically estimate replacement around 60,000 miles of use or more.

 

[JRP3]

Given the speed of even a 36-48v motor there would need to be about 30:1 reduction to a 25" diameter wheel to get a reasonable working speed of 10mph at 4000rpm. The reduction may even need to be more, say 50:1 to bring that speed down to 6mph. Much easier to obtain such reduction with a worm wheel gearbox then a chain.

Run a 48 volt motor at 24V to cut motor speed in half.

 

[JRP3]

That looks good. Another idea might be to take your design and put a tray or basket over the battery or on the front for carrying heavy objects such as rocks or wood. Maybe you could clarify this but I get the feeling that some of the posters are overlooking the realities of your area, where finding some scrap metal, chains, sprockets, and maybe even old motors are one thing but shipping in new or even used previously built tractors are an order of magnitude more difficult and not cost effective. Cheap labor means anything that can be built on site is going to be a better choice.

 

[JRP3]

Electrical components could be as simple as a solenoid. You could do something a bit fancier with a few solenoids to switch between 12 and 24 volts, a simpler version of this:
http://www.poormansev.com/id24.html

 

[JRP3]

Should the weight be set further forward since attachments at the rear would shift the balance back?

 

[JRP3]

That could be a heavy suitcase

 

[JRP3]

Might need to use a jack shaft setup to get the gear reduction needed, though there are some motors built for lower RPMs.

 

[JRP3]

I build and sell plans to a machine that should do what you want.

Neat machine you have there.