Hackaday Prize Entry: A Light Electric Utility Vehicle

[Chris] lives in South Sudan, where there are a lot of poor areas with terrible infrastructure. One of the bigger challenges for this area is getting people and materials over roads that are either bad or don’t exist. Normal vehicles aren’t built for the task, and a Hilux or Land Cruiser is much to expensive. For his Hackaday Prize entry, [Chris] is building a rugged low-cost utility vehicle platform for the developing world.

This battery-powered, four-wheel cart is made out of what [Chris] could find. The frame is made out of 50x50mm angle iron that’s welded together, with the body panels fabricated out of 1200x2400x1.2mm sheet that’s sourced locally. While [Chris] would like better wheels, the cheap Chinese motorcycle wheels are everywhere and cheap – $65, which includes the bearings, breaks, and sprockets. It even has higher ground clearance than the Land Cruiser.

[Chris] already has a prototype of his project built and it’s rolling around. You can check out a video of that below.


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32 thoughts on “Hackaday Prize Entry: A Light Electric Utility Vehicle

  1. Thanks for posting this. I posted a question on one of my project logs about the OSMC open source motor controller, but didn’t get any responses. Maybe with a bit more exposure I’ll find someone with some experience. Has anyone built or used one? I need a controller with higher continuous current capabilities, but I am concerned about the heat sinking.

    Thanks

      1. I have joined the group, and tried to go through past post. I find yahoo groups to be just awful for this kind of information.

        I have looked at Open Revolt, but it is for series wound motors, and I am using pmdc.

        Thanks

  2. You probably aren’t well placed to make your own tires, but perhaps this video can serve as some inspiration.

    These large low pressure tires will get you over rough terrain and won’t get bogged in the wet. Being low pressure, repairs should be relatively easy.

  3. Needs some suspension, or a twist axis at the hinge. A couple of coil springs there would keep the twist under control. The pivot wouldn’t need to be fancy, no bearings, just two pieces of as large a diameter pipe as can be found, which nest together with decently close tolerance. Slather it with grease before assembly and that could do for the life of the thing.

    Why do you want something like that? Watch Full Metal Challenge episode 4 on YouTube. The Flying Horse team from China failed hard in the Roller Coaster event with a suspensionless center pivot vehicle.

    Large construction vehicles with that design get away with it on rough ground because they’re large and heavy to smash the ground down until all four wheels touch, or they use squishy wheels to flex over bumps, or they’re wide enough they’d have to tipped well over 45 degrees to roll over.

    1. Yeah what you are describing with the center pivot at the of articulation is exactly what I am doing. I have a 25mm solid shaft that spins in a casing made from two 50mm angle cut so that it is tight. So far it works really well. I wouldn’t love the system at high speeds, but at the speeds I am going it seems to work. So far I haven’t needed to limit travel because the batteries are so low they act as good ballast. This system means there is way more suspension travel than a typical vehicle. A similar system was used in the Pug articulating 4×4 vehicles, but it is much easier in an electric vehicle because there is no complicated universal joint to transfer power.

    1. Yeah the remote is more for testing than anything. It is actually cheaper than most joystick setups. I have some dual pot joysticks coming at some point to make a mounted control panel, but with remote and receiver at about $25 usd through HobbyKing it is tough to make something for less. Hopefully I can keep remote control an option for some of those more questionable areas.

      1. Could you not repurpose a wired gaming controller? They’re available for cheap and have reasonable enough resolution even for the worst brands. You could use extra buttons for later features: Headlights, dump mechanism (though a simple human power one would probably suffice), &c.

  4. Yeah I was thinking that the lack of suspension is very hard on the passengers, the load and the wheels and frame – and the dirt roads.

    AND it is a really shitty way to convert forward motion (requires electricity) into pogo stick motion (wastes enormous amounts of energy). because in essence, your having to accelerate and decelerate the entire mass of the vehicle AND the load it is carrying in a vertical fashion – or at least ~25% of it, just to get over bumps and ditches;

    Where as allowing more or less ONLY the wheels to rise and fall, independently of the vehicle mass, means that everyone gets a comfortable ride, the product getting carried gets minimal damage and the vehicle does not get broken apart.

    There is also the issue of vehicle damage in terms of wear and tear, as a wheel rated to carry say 100Kg as part of a sprung mass – when that is doing say 30Kmh, and it hits a large bump / pot hole – then the entire mass of the vehicle is separated from it.

    When the vehicle is an unsprung unit, the wheel then has to accelerate the entire mass and during that transitional period the load may go up to 200 – 300 or 400Kg etc., thus wearing out / breaking the wheel (bearings / spokes / rim / axle) and the chassis, and chewing up the dirt roads rather badly.

    This is the difference between a GOOD basic design, and a design that has failed.

    I’d suggest that 20 cm of fairly stiff plain sprung suspension would be adequate – and given the low speeds etc., that dampeners / shock absorbers are not needed yet – but your design should leave room for these to be included at a later date.

      1. Purpose of the build: haywagon.

        Seriously though. Two 85 Ah AGM batteries will give you about 1 kWh of useable energy, unless you want to destroy your batteries with more than 50% DoD.

        1 kWh of energy drives 2x 650 W motors a minimum of 45 minutes. Assuming you’re going 15 mph at half throttle, you can reach about 20 miles of distance, or 10 miles out and 10 miles back in. Just enough to reach someone’s field outside of town and come back when the day’s work is done.

        The vehicle is obviously never able to really go anywhere. It’s not a transport system like a car or a bus, but more like a lawn tractor.

  5. Forgot to add this:

    I’d also be very inclined to use a drive system that uses a simple stepped power feed to each motor, and to use a purely basic leverage based mechanical steering system.

    Your thinking like a university graduate, instead of someone who knows that on slippery wet dirt roads, that with your steering by motor, means that if the wheels are not getting traction, then you have not got steering either.

    By having a highly geared / leveraged steering, you get steering whether the wheels are getting traction or not, which is a great help when the unit gets bogged etc., or the batteries have been run flat and it needs to be pushed to it’s destination.

    It’s a little bit of design issue, that I’d be inclined to use only a single axis pivot and mechanical steering AND long travel suspension, as the two axis pivot, while noble, makes everything else linking the two parts – needing large amounts of extra material, as the body sections rotate relative to each other.

    It’s a single plane set of controls, vs. a three axis set of controls connecting the two parts.

    1. I think you make some really good points. I think one thing to look at is intended speeds. I am looking at not more than about 20kph which limits the bouncing effect you are talking about. I had initially planned to use suspension from the same motorcycles I got the wheels from, but I wanted to test it without suspension to see how it handled. So far it seems pretty good, but it needs a lot more abuse to see. I have tested it with myself in the front and maybe 10 kids in the back and it worked pretty well. Seems to grip the road better with more weight in the back. It may also just mean you drive it differently (as in slow down more) than you would a vehicle designed for higher speeds.

      In terms of steering, that is another area I am still testing. I am ultimately trying to make something that is as simple as possible so I am testing to see if differential motor control can work. I think the fact that I will have 4 motors one for each wheel, and have the opposite wheel on the front and back run in parallel from the controller (as in front right paralleled to back left) should help. I can get steering with only the front motors connected or only the back.

      Thanks for your input. I guess trying out ideas and learning from everyone is what this contest is about.

      Chris

      1. If they’re DC motors, a differential is as simple as connecting them in series/parallel.

        In parallel, the one motor that spins faster develops higher back-EMF which sends all the current the other way. This is effectively a locked differential where the slipping wheel gets power taken off and sent to the one with traction.

        Connecting the motors in series sees the opposite effect. The wheel that runs faster sees more voltage, gets more power distributed out of the mutual current, so the steering becomes very light.

        Since you have two batteries, the difficulty of varying voltages in the series-parallel configuration are also solved and you can trivially switch between the two. A sliding contact switch could be made out of plywood and a bunch of soup cans that allows one to switch the battery/motor configurations and the controller can be a simple PWM switch with a single potentiometer for throttle.

    1. Yeah I’ve bought 400 watts of panels that I hope to build into a canopy which should also protect from the sun and rain. I am hoping that the intermittent use that a utility vehicle gets will lend itself to solar charging. Often its a mater of short trips with lots of time sitting between.

      Now I just need to figure out how to get my panels across the border.

      1. Did you get a charge controller? Did you buy diodes to connect the solar panels in a way that lets one panel to be in a shade without frying it? Did you get spares? Did you get extra panel or two to compensate for degrading panels?

        I am not trying to be a criticising smartass, but solar panels and electric vehicles are too much complicated for this setting in my opinion.

        Is it possible to get something old, simple and reliable that runs on biogas/biodiesel?

        1. I’ve done quite a few small pv set ups out here, and where I live has about 3.5kw of panels so I am comfortable with solar. I have a tracer 4215 bn made by ep solar coming from China hopefully soon. That is a 40a controller which does real mppt, and has serial output that can easily be grabbed by an arduino. I have a 10a version and they seem to be fairly well made. For about $225 shipped to Uganda I think it is a decent compromise. Much better than the cheapo pwms out there and much cheaper than something like an Outback (which I have had nothing but problems with.)

          I would say that setting up biogas/biodiesel probably adds more complexities than solar, but it certainly has it’s advantages. I have considered more of a hybrid with a small engine running a heavy truck alternator. There is currently a fuel shortage in South Sudan which has pushed me towards solar. Petrol prices have gone as high as $7 USD per liter or about $28 USD per gallon.

  6. Really cool project!!!

    I was just thinking about mud ruts during the rainy season, would it be possible to weld 2 additional struts (something akin to a cutting and welding a shortened piece of a garage door spring, connecting it to the smaller wheels that would lead and trail the main wheel?) at greater than 60′ underneath? Maybe find and cut two old semi-truck/large tractor tires to make belts that can be used as treads? (The small wheels don’t need to provide any weight support just be able to lay down and provide some tension to keep the “belt” in place as well as overcome the bumps/logs/rocks).

    I’d very much encourage you to reach-out to groups like protrackapu co.za I imagine they could really use this in their anti-poaching campaign. Either as an automated scout / animal decoy or help with supplies.

  7. A very imaginative project! Some thoughts from my experiences with similarly simple vehicles:

    1. Spoked motorcycle/bicycle rims can’t handle side loads. It’s easy to fold them over in a 3- or 4-wheel vehicle that can’t lean. Maybe tack weld solid sheet metal disks to each side to reinforce them?

    2. Some kind of suspension is needed for 4-wheel vehicles. Without it, the force on the frame becomes extreme when one wheel is in a hole so the two diagonal wheels are supporting all the weight. This can often be mighty simple. Look at old wagon front axles for ideas. Or a single leaf from a car leaf spring, supported on just one end so it’s much easier to flex.

    3. Maybe use old car tires that are too damaged or worn for a normal vehicle? Even if they won’t hold air, they are still stiff enough to support a reasonable amount of weight, yet soft enough to provide some “suspension”. Or stick an inner tube in them. Our kid-built EVs have used these successfully. They even made wooden rims, with the tires screwed to them!

    4. You’re planning on 4-wheel drive with DC motors? Then use a contactor controller like the early EVs. Cheap and simple as dirt (good in 3rd world situations). By switching the motors in series/parallel combinations, you effectively get “gears”. All in series = lowest speed, highest torque (every motor gets 1/4 of battery voltage, but full battery current). 2 series, 2 parallel = medium speed and torque. All in parallel = highest speed, lowest torque (each motor gets full battery voltage, but 1/4th of battery current). See http://www.sunrise-ev.com/controllers.htm for more.

    5. What are you going to use for batteries? Don’t use car batteries; their life will be abysmal in this application. Golf cart batteries will probably give you the best performance/cost ratio, if they are available in Sudan.

    1. Thanks for your thoughts.

      In regards to the wheels I think I will torture test them and see how far they will go before failure, and then start looking at modifications/upgrades.

      Contactors are great for there simplicity, but by the time I bought all the contactors I think I could make a proper h-bridge controller. Which gives me the ability to reverse, regenerative braking, and differential motor steering.

      In terms of batteries if I was in the States I would use golf cart batteries, but there is not much golfing here in South Sudan. I currently am using 2 225ah AGMs, but I have 200ah tubular gel batteries coming with the panels.

      1. I’m assuming this is a low-voltage system (48v or less)? If so, then plain old automotive starter solenoids will work for a contactor controller. A few tricks to make this work:

        1. Connect a parallel R-C network in series with the coil, to hit it with full power for pull-in, then low power to hold it. This keeps intermittent duty coils from burning up in continuous use. Or use an automotive brake light in series (even cheaper and simpler). When cold, it has low resistance to pull in fast. Then its filament heats up to limit the current.

        2. Contactor controllers have multiple contacts in series. Arrange the circuit that switches the coils so you never have one 12v contact breaking a higher-voltage circuit.

        3. Rectactor circuits replace half the contactors with diodes. Much simpler and cheaper. :-)

        4. And of course, you can just use a big rotary switch, like they did years ago. Look at the old ones; they are simple to make. Yes it is crude, but there are 100-year-old trains and industrial controls still running on this kind of technology.

  8. An “E” type jaguar has a “welded iron box section ” from the firewall forward for strength and weight reduction. Holds all the motor , front wheels and steering ,battery and bodywork. Bolts onto the firewall.

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