[congofarmer]

Dear EV experts,

I'm new to the forum and to EV's in general. I'm amazed to find so much experience here, which is why I would want your help with the small project I'm creating.

Let me sketch you my situation.

I work for an NGO in the Democratic Republic of Congo. We're working with small and very poor farmers in a very remote region. They do all their work manually. Some form of mild mechanisation is highly welcome. The "walk behind tractor" or "roto-tiller" serves as the starting point.

• fuel (gas) costs a lot here in the interior (2200 francs / liter, that is: 1.8 euros /l or $4.9 / gallon); diesel is cheaper, but still off-limits (about 20% less the price), which is why we don't like IC engines
• big tractors are too big; people don't have the cash to invest, nor the technical skills. Getting such a machine to the interior (via the Congo river) is prohibitively costly
• farm fields are tiny: the average field is around 1 acre (half a hectare)
• we already have several solar panels (to charge the 12V batteries of our big radio and our P.A. system) and could add some more
• this situation had us decide on designing a simple, small, low-cost electric tractor

The are several back-breaking tasks for which we seek mild mechanisation and for which the tractor should be used:

• removing roots from trees that have been cut down (slash-and-burn farming is the main type of farming here)
• removing big chunks of slash (burned branches of, say, two meters)
• cutting or pushing down weeds and small trees on fallows (every 2 to 3 years, a fallow is re-used; it has then grown a lot of biomass)
• tilling
• weeding
• fertilizing
• harvesting
• pulling a cart with produce to the warehouse

Main subsistence crops grown:

-corn, cassava (manioc), rice, beans, groundnuts


Our idea is to train a few people to operate the tractor, and to help others use it. Costs are carried by the cooperative which we have created.

The tractor should be (I know this will be a tall order):

• multifunctional
• durable
• relatively powerful (we've done some tests pulling roots with a Yamaha 125 DT, which worked; the DT boasts 17hp)
• low-cost (functional: no gadgets!)
• extremely simple to operate and to maintain
• should be possible to build the machine in Kinshasa, by local technicians

The tasks it has to perform are short-duration tasks; a capacity to work during 1 hour is already OK.

We made a tentative sketch of what it could look like, which I attach to this post. (Don't mind the simplicity of this drawing).

Now since we've got no expertise whatsoever on EV's, we'd highly appreciate your first impressions, advice, or input.

If the eventual tractor were to work well, we have network resources (contacts at major agricultural and international development organisations) which may help replicate it and make a real program out of it.

Thanks!

PS: I found Woody's E-tractor project, which is great, but of an other order. /woodys-tractor-project-39910.html

 

[congofarmer]

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.

Your project is very interesting, and already offers a good view on the capacity we're looking at. In one of the videos you show how you pull a log through the forest, in a for me highly impressive way! Our chunks of wood are often smaller, but if the tractor can handle a log that big, many of our farmers would be exhilirated.

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).

 

[congofarmer]

Hi and welcome.

Thanks.

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

Sure. JRP3 and Woodsmith, as said, the design is completely open. I will at each step quickly re-design, so you can view your input graphically.

I would be tempted to go with two wheels on the same axle

I'll draw, because it's also one of JRP3's suggestions. Which makes 2 of you.

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.

I've thought about this, and have a design ready. The steering via the wheels' motors would be very easy to handle. But I have put it on hold, because it may be too complex and perhaps too costly. Let's not forget that the fields are tiny, and the jobs not too intricate.

But all ideas remain open and welcome!

 

[congofarmer]

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.

I think you are on the right track. Low cost and simple. Turning is the only operation that may require some force by the farmer, but they're used to heavier things, so that shouldn't be the problem.

 

[congofarmer]

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.

In fact, the tiny wheel in my first design, is a such a freewheel. Turning this one-big-wheel tractor would be very easy. But spinning-over may be a prob.

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.

Well, for this prototype we'll use new parts for the frame, but all the rest will be locally sourced. The Congolese are masters in finding decent used stuff or in re-furbishing it (and they're also masters in quoting you a hefty price once they know you're "NGO").

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.

I prefer a kind of "open-source", ultra-basic design, that can serve any motor one finds.

If ever there were to be more than one of this to be made, it would still be manufactured locally, with few parts being sourced abroad.

 

[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.

 

[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.

 

[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:

 

[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.

 

[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.