[Woodsmith]

Hi and welcome.

I was also thinking the one wheel drive would be unstable, expecially slow speed in the field.

I would be tempted to go with two wheels on the same axle but possibly driven by two geared motors, like the ones use on powered wheel chairs but bigger. If the angled gear drive was by worm and wheel gearing then you would get a big reduction ratio in a compact space and it would remove the need for braking thus aiding simplicity. The tractor could be controlled by separate power controls on each hand grip for each wheel so it would steer like a tank with skid steering.

The wheel hubs could be on bearings on the drive shafts and drive would be transmitted from the shaft to the hub by means of a drive peg from a flange on the drive shaft to the hub. That would allow the tractor to freewheel and be towed manually to and from a job.

 

[Woodsmith]

Spinning around a two wheel tractor like that is difficult if the axle is solid. With that approach a simple ratchet freewheel would be useful as used in some rotavator designs.

The other thing to consider is whether the tractor is to be funded by an organisation that can afford a good and reliable design made from new parts or if it will need to be made from locally sourced parts of variable quality and possibly preused.

Also if there is to be only one tractor that will be different to one that will be the concept for a short production run that could add value to the community tasked with its supply.
The later case would be better with a reliable supply of parts where as the former could be made of anything that comes to hand.

 

[Woodsmith]

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.

Even a single worm reduction on an axle would do it and it would be both robust and sealed from the environment for a long life.

It would mean having to buy in an expensive component but could be viable if it was a production run.

 

[Woodsmith]

I think what you need is something like this. These are everywhere around here and are very robust and have lots of torque to dig into the ground. I am sure someone could make one with detachable tools too. Maybe they already have one. Remove the gas motor and put on a nice DC sepex motor and use like 24 volts and simple contactor control. Either on or off. Use the gearing on the tractor for speed control like is done with the gas engine anyway. I turn it on and turn up the throttle and go. I never throttle up or down while using this tiller. It will dig through anything.

Pete

That sort of thing would make an idea candidate for a one off conversion or a perhaps a conversion kit if other similar tractors were easily obtainable.

Not so easy if they needed to be made from scratch for production.

Plenty of food for thought.

 

[Woodsmith]

To aid options, what sort of resourced and facilities would there be to work within?
Is the preference towards adapting and converting exisiting machinery or developing something from scratch?

 

[Woodsmith]

How about a two fold design?

First off you need a design for a simple motive impliment, the simplest is the two whell tractor. They are fairly easy to design and make with scraps to suit the local resources and needs.

Secondly you could look at a simple motive power source. A sepex motor with a simple means of control and a battery cradle that can be easily constructed and used to replace any equipemnt that otherwise has a small petrol engine.

The two would give you a locally made tractor. The power unit on its own would be a conversion system for existing equipment with a greater range of application.
Depending on what salvageable machinery is available then either a sprocket or a geared output with something in the region of 20:1 to 50:1 depending on application.