[congofarmer]

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

Pete, thanks, this is one of the inspirations for our tiny tractor. In fact, all roto-tillers, walk-behind tractors, and one-wheel tractors have been the inspiration.

However, it's not difficult to design a similar frame from scratch. We have many people here who know how to weld, and the sheer number of car, truck and motorbike mechanics is mind-boggling. They are highly skilled (especially when you have to use creative skills) and they don't ask a lot of money for their work.

 

[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.

 

[congofarmer]

My point, why make from scratch when you more than likely could buy them for less. There are many manufactures of walk behind tractors world wide. I'd almost bet he could get them there. Just gotta do your homework.

Pete

True, if only we could find these here. But we haven't. As said, all the metal-work would not be too costly and relatively easy. The electric parts shouldn't be too difficult either. The main problem is the choice of motor and batteries, deciding on how to reduce gears and which kind of transmission we'll use, and the general outlay of the design (where to put the wheels? How to make it turn?, etc...).

 

[congofarmer]

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?

Well, given that we have some room to play (both in terms of cash and human resources and time), we might want to develop something from scratch.

It would also facilitate getting a fund for any replication program (but this is the distant future), because "innovative" concepts get money easier than "adaptations" or modifications of existing designs. (That's my experience).

 

[congofarmer]

This one is available worldwide. http://www.paddyricetransplanter.com/walk-behind-tractor.htm

Gottdi, if there isn't a dealer, we will never import it. Import costs for Congo-Kinshasa are one of the highest in the world.

Sadly, there are no walk-behind tractors in Congo. Perhaps they can be found in Congo-Brazzaville, but we'll have to check this out.

 

[toddshotrods]

Nice project. What type of materials and fabrication capabilities would be available? For example, do you have steel angle iron or tubing available for building the frame? Do you have the materials and skilled labor to work with it? Are there electric forklifts or some type of common machinery you will be getting the motors from, or wil they be sourced new? More info from you will narrow the options and ideas down to those more applicable for you.

I agree with the two wheel, side-by-side, design. It's the most practical, most stable for the intended purpose. I actually had an antique walk-behind tractor when I was a teenager. Got it from a neighbor to build a gokart, but never did. It had a plow on it. I imagine it would have been ideal for what you need.

Gotta go back to work now, but I'll be back later with more input and ideas. I agree with the thought that muscling it around to change direction wouldn't be that big of a deal. I used to do that all the time with tillers in the garden.

 

[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.

 

[Jimdear2]

This is a wonderful idea, a lot of american small farmers used equuippment ilke this for the household gardens (your 1 acre plot). You might read this article that compares a couple of currently available machines.

I do want to stress that a build it youself project i.e. making something out of off the shelf components is quite possible. But I would think that anything built like that would probably have a very limited life under the circumstances you describe. I am sure that some of the international agencies could help with engenieering and design.

http://www.motherearthnews.com/Mode...Behind-Tractors-Comparison.aspx#ixzz1BmkYpcY4

The BCS is a tough machine and has many (I've heard up to around 300)attachments. I can only think that you would want something currently in production (look at their transmission warrenty). You might contact the manufacturer in Italy to see if the machine could be made available electrically powered, in kit form or less engine for conversion.

The other machines of this quality such as Gravely and Allen Bradley are no longer in production and have become collectors items.

I have heard mention of Honda producing a walk behind. You might check with their power products division. Again ask if it is available as an electric or without power plant ready for conversion.

Ther is still a lot of small farmer equippment made in Eastern Europe, maybe you can find something there.

My feelings are whatever you do, you would want to stay in the 12 to 24 volt range. Dependin on how many units you plan even a custom (Extra Tough) motor and controller package could be developed. You would for sure want something like a sepex setup so a blown belt or chain wouldn't equal a blown motor.

The speed of most of these tractors were controlled by the transmission gear chosen so the controller could be a sealed single speed thing. Just on/off.

As a last resort look at China, go to Ali Baba

Hope this helps,
Jim

 

[Harold in CR]

If your welders are as good as you say, and you have cars and trucks all around you, why not cut down a car differential and axles ?? You can attach pulleys, sprockets, gears, right on the input shaft, and the housing will already have "spring pads, to attach a section of cut down car or truck chassis.

This is done all the time.

I would cut the axles so one end is cut on two sides, and fits into a single cut out on the center of other half. Clamp in an Angle piece, and weld and turn, to keep it straight. You will never break that joint with what you are trying to do. You could even put the joint inside a strong tube and just weld the ends of the tube. That way, you don't take out the strength of the axles where you cut them.

Tires and wheels should be easy to change out. This could turn into a common design for selling or renting out, so to speak ??

 

[Jimdear2]

Here are a couple of thoughts.

A lot of make do tractors were constructed from reinforced car or light truck frames with two and even three transmissions and tall mud and snow tires.

You say you have a lot of people with good mechanical skills. Do a Junk Yard Wars type competetion. With one rule, the components have to be plentiful.

 

[congofarmer]

Before replying to the new input, first a quick pic of the two-wheel design. I know this isn't a great innovative concept, but I like to sketch the things we discuss. Even if they're extremely simple.

This is many people's suggestion, and I think I'd agree with its simplicity:

 

[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.

 

[congofarmer]

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.

Well, the situation is nuanced. Kinshasa is (perhaps) Africa's second biggest city, with an estimated 10 million inhabitants.

If you search well, you will find almost anything, including perhaps a walk-behind tractor and a new, imported, highly expensive electric motor. But this requires a real search, and there are few channels in which you can work. You mostly depend on luck.

There are no real dealers of quality products, except for a few houses like Iveco and Yamaha. And even they have very limited stocks and choice of products. What is more, their price is consistently much higher than if you were to buy in the U.S. or E.U.

This is due to excessive taxes (on imports) and Congo's problematic logistics.

In short, we're touching one of the key reasons as to why the country is in a bad fix, and develops so slowly.


On the other hand, Kinshasa is a gold-mine for the so-called "récup" - that is all kinds of used goods that can be found, repaired, refurbished, adapted, what have you. There are literally tens of thousands of people in the informal economy who depend on this sector.

It's here that we're looking into finding the materials for our little experiment.

But then suddenly, when it comes to, for example steel products and the skills needed to manufacture something - there is no problem. Most basic steel products are to be found new (or, again, recup): tubes, plates, bars, t-frames, etc... Welding and metal workshops are plenty.


In short, as a starter, I could say that it's best to source everything locally. Importing is simply out of the question - unless you can rely on a person who can bring the object in his luggage from Europe or the US to Kinshasa. Else, importing is simply a losing proposition.

Let's not dramatise the situation: there are people here who succeed in building huge boats (barges) with very powerful engines and everything that this requires. It's doable, but you need some creatives and people who can search stuff for you. In this sense, the e-tractor is not a big project; in fact, I don't see any problem in finding the necessary materials.


On a final note: electric components should be kept to a minimum (not too many controllers, etc). But I can buy them here (EU) and take them with me in my luggage. But all the other materials: sourced locally.

 

[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

 

[toddshotrods]

Due to time constraints, my CAD models are even more rudimentary than yours, but will hopefully get the points across.

I think you should build a sturdy steel basket main frame that would hold the motor and batteries, handle all the torque reaction and stresses, and balance the weight of the motors and batteries evenly over the axle. Considering the tasks you have in mind, I would want to make the tractor as naturally balanced as possible placing as little stress on the operator as possible. Long, wide, handlebars will allow the operator to easily counterbalance forward and backward, and maneuver the tractor easily. For tasks where you need more proactive counterbalancing, you can have bolt on caster wheels.

A standard size main frame would also allow you to develop different drop in powertrain combinations. So, for example, if you had two different motors you could have a drop-in powetrain cradle for each one. That way if one was down for the service the tractor could its work with the back-up powertrain. Attachments and accessories could be contracted out to fit the frame, and simply (ideally) just bolted on when they arrived.

 

[congofarmer]

Due to time constraints, my CAD models are even more rudimentary than yours, but will hopefully get the points across.

I think you should build a sturdy steel basket main frame that would hold the motor and batteries, handle all the torque reaction and stresses, and balance the weight of the motors and batteries evenly over the axle. Considering the tasks you have in mind, I would want to make the tractor as naturally balanced as possible placing as little stress on the operator as possible. Long, wide, handlebars will allow the operator to easily counterbalance forward and backward, and maneuver the tractor easily. For tasks where you need more proactive counterbalancing, you can have bolt on caster wheels.

A standard size main frame would also allow you to develop different drop in powertrain combinations. So, for example, if you had two different motors you could have a drop-in powetrain cradle for each one. That way if one was down for the service the tractor could its work with the back-up powertrain. Attachments and accessories could be contracted out to fit the frame, and simply (ideally) just bolted on when they arrived.

Exactly. Thank you for the drawings. This is the most elegant and simple solution. It can be easily made with the steel materials at hand here.

 

[JRP3]

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

 

[toddshotrods]

Exactly. Thank you for the drawings. This is the most elegant and simple solution. It can be easily made with the steel materials at hand here.

Surely. I forgot to mention that I was also thinking with the idea of importing needed supplies like pillow block bearings to mount the axles, sprockets, chains, etc, in your suitcase as you said. The tractor itself is a product of the area, the rest is open to interpretation.

 

[JRP3]

That could be a heavy suitcase

 

[toddshotrods]

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

Not for a universal design. You can always shift the weight with counterweights, attachments, etc. IMO, you would want the basic design to be as naturally balanced as possible. That way your not fighting to achieve a natural balance, just adapting to the situation.