Kotonki: Agricultural Vehicle Built For Customization

Agriculture on any scale involves many tasks that require lifting, hauling, pushing, and pulling. On many modern farms, these tasks are often done using an array of specialized (and expensive) equipment. This puts many small-scale farmers, especially those in developing countries, under significant financial pressure. These challenges led a South African engineering firm to develop the Kotonki, a low-cost hydraulically powered utility vehicle that can be customized for a wide variety of use cases. Video after the break.

The name Kotonki is derived from the Setswana phrase for a donkey kart. It is in essence a self-propelled hydraulic power pack, capable of hauling 1 ton of anything that can fit on its load bed. It comes in front-wheel drive or four-wheel drive versions, with each wheel individually driven by a hydraulic motor. The simple welded steel frame articulates around a double pivot, which allows it to keep all 4 wheels on the ground over any terrain. At a max speed of 10 km/h it won’t win any races, but neither would most other agricultural vehicles. The Kotonki is built mostly using off-the-shelf components and is powered by a common 12HP Honda engine. In the world of DRM agricultural equipment, this makes for simple repairs, low running costs, and easy customization for the task at hand. This can include mounting log splitters, water pumps, lifting beds, or anything else that can be driven by its hydraulic and rotary PTOs (Power Take-Off).

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Simple hydraulics using syringes

Super Simple Hydraulics Using Syringes

When making a toy excavator arm, or any robotic arm, the typical approach is to put motors at the joints, or if there isn’t room, to put the motors somewhere else and transfer the force using fishing line and pulleys. [Navin Khambhala] chose instead to do it more like the real excavators, with hydraulics using syringes. And we have to admit, the result it pretty elegant in its simplicity.

The syringes do the job of single-acting hydraulic actuators, one at the motor and the other where the force is needed. In between them, what appears to be clear vinyl tubes carry the fluid between syringes. 12 volt DC motors with bolts on them move nuts attached to the syringe pistons to push and pull the pistons. It is so simple that no further explanation is needed, though like most apparently simple things, we’re sure a lot of effort went into making it that way. The video below shows the finished product, as well as walks through the making of it.

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Retrotechtacular: Principles Of Hydraulic Steering

Have you ever had the pleasure of trying to steer a one-ton pickup from the 1940s or wondered how hard it would be to turn your car without power-assisted steering? As military vehicles grew larger and heavier in WWII, the need arose for some kind of assistance in steering them. This 1955 US Army training film handily explains the principles of operation used in a hydraulically-assisted cam and lever steering system.

The basic steering assembly is described first. The driver turns the steering wheel which is attached to the steering shaft. This shaft terminates in the steering cam, which travels up or down along the camshaft depending on the direction steered. The camshaft connects to the steering shaft through a spline joint, which keeps the travel from extending to the steering wheel. The steering cam is connected to the Pitman arm lever and Pitman arm shaft. Movement is transferred to the Pitman arm, which connects to the steering linkage with a drag link.

The hydraulic system helps the Pitman arm drive the linkage that turns the wheels and changes the vehicle’s direction. The five components that comprise the hydraulic system use the power of differential pressure, which takes place inside the power cylinder. The hydraulic system begins and ends with a reservoir which houses the fluid. A pump driven by the engine sends pressurized fluid through a relief valve to the control valve, which is the heart of this system.

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