The Trials And Tribulations Of E-Bike Drivetrain Design

August 26, 2019 by Lewin Day 32 Comments

[Tom Stanton] is well-regarded in the maker community, and has put much effort in over the years on a variety of electric vehicle builds. In the process of upgrading his e-bike last year, he ran into some issues with the main drive pulley. Rather than rely on guesswork, he threw engineering at the problem.

Static weight tests were carried out in combination with FEA to determine the root cause of the problem.

The problem concerned the mounting bolts on the pulley’s hub, which would pull out under high torque. [Tom’s] initial finite element simulations had suggested the design was sound, but reality was proving otherwise. After further analysis and testing, [Tom] determined that his analysis hadn’t properly simulated the bolt pull-out condition. With this corrected in the software, it was readily apparent that there simply wasn’t enough material around the bolt holes to hold the torque load.

With the simulation now more closely agreeing with reality, [Tom] was able to correct the design. New parts were created with a strengthened mounting section, and the pulley was successfully able to deal with the loads in service.

It’s a great example of using engineering simulation tools to solve a problem quickly, rather than simply guessing and hoping things will hold up. We’ve seen [Tom]’s work before, too — like this fun backyard trebuchet build. Video after the break.

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Electric Dump Truck Produces More Energy Than It Uses

August 22, 2019 by Bryan Cockfield 77 Comments

Electric vehicles are everywhere now. It’s more than just Leafs, Teslas, and a wide variety of electric bikes. It’s also trains, busses, and in this case, gigantic dump trucks. This truck in particular is being put to work at a mine in Switzerland, and as a consequence of having an electric drivetrain is actually able to produce more power than it consumes. (Google Translate from Portugese)

This isn’t some impossible perpetual motion machine, either. The dump truck drives up a mountain with no load, and carries double the weight back down the mountain after getting loaded up with lime and marl to deliver to a cement plant. Since electric vehicles can recover energy through regenerative braking, rather than wasting that energy as heat in a traditional braking system, the extra weight on the way down actually delivers more energy to the batteries than the truck used on the way up the mountain.

The article claims that this is the largest electric vehicle in the world at 110 tons, and although we were not able to find anything larger except the occasional electric train, this is still an impressive feat of engineering that shows that electric vehicles have a lot more utility than novelties or simple passenger vehicles.

Thanks to [Frisco] for the tip!

A Range-Extended Electric Van

August 20, 2019 by Bryan Cockfield 76 Comments

The only thing limiting the range on any electric vehicle isn’t really battery technology, but cost. Customers don’t want to pay more money for an electric car or van that does essentially the same thing as one with an internal combustion engine. This in turn limits the amount of batteries manufacturers put in their cars. However, with enough money, and thus enough batteries, electric cars can get whatever range you want as [Muxsan] shows with his Nissan e-NV200 that gets over 400 ~~miles~~ kilometers on a single charge.

The Nissan e-NV200 is a battery electric vehicle (also available as a badge-engineered Chevrolet van in North America) with a drivetrain from the Nissan Leaf. This means that all of the components from the Leaf basically plug-and-play in this van. [Muxsan] took an extra 45 kWh of batteries and was able to splice them in to the existing battery pack, essentially tripling the capacity of the original 24 kWh pack. Some work was needed to the CAN bus as well, and the car’s firmware needed to be upgraded to reflect the new battery pack, but a relatively simple modification otherwise, all things considered.

While watching the video [Muxsan] also notes how much empty space there is all around the van, and Nissan could have easily upgraded the battery pack at any time to allow for more range. It also took the car 10 hours on a 6 kW charger to charge completely, but that’s not unreasonable for 430 miles of range. If your high voltage DC chops are up to snuff, it’s not impossible to find old Leaf batteries for other projects, too.

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Electric Vehicles On Ice

August 16, 2019 by Sharon Lin 10 Comments

This winter, a group of electric vehicle enthusiasts, including [Dane Kouttron], raced their homemade electric go-karts on the semi-frozen tundra nearby as part of their annual winter tradition. These vehicles are appropriately named Atomic Thing and Doom Sled, and need perfect weather conditions to really put them to the test. You want a glass-like race track but snowfall on ice freezes into an ice-mush intermediate that ends up being too viscous for high-speed ice vehicles. The trick is to watch for temperatures that remain well below zero without snow-like precipitation.

The group is from the community makerspace out of MIT known as MITERS and already have EV hacking experience. They retrofitted their VW Things vehicle (originally built for a high speed electric vehicle competition) to squeeze even more speed out of the design. Starting out with an 8-speed Shimano gearbox and a 7kW motor, they assembled a massive 24S 10P battery out of cylindrical A123 cells salvaged from a Prius A123 Hymotion program. This monster operates at 84V with a 22AH capacity, plenty for power for the team to fully utilize the motor’s potential.

The battery is ratchet strapped to the back of the Atomic Thing to provide more traction on the ice. It must feel just like riding on top of a different kind of rocket.

Original configuration of battery packs

Battery packs ratchet strapped

They tried using ice skates in the front of the Atomic Thing, but the steering was difficult to control over rough ice. Studded solid tires perform quite well, resulting in less jarring movement for the driver. Doom Sled is a contraption built from a frame of welded steel tube and a mountainboard truck with ice skate blades for steering. The motor — a Motenegy DC brush [ME909] — was salvaged from a lab cleanout, transferring power to the wheels through a chain and keyed shaft. The shaft-to-wheel torque was duly translated over two keyed hub adapters.

The crew fitted a seat from a longscooter and made a chain guard from aluminum u-channel to keep the flying chain away from the driver’s fingers. The final user interface includes a right-hand throttle and a left-hand “electric brake” (using resistors to remove the stored energy quickly to combat the enormous inertia produced by the vehicle).

Overall, ice racing was a success! You can see the racing conditions were just about perfect, with minimal ice mush on the lake. Any rough patches were definitely buffered smooth by the end of the day.

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Cheap Electric Scooter Gets A Big Brake Upgrade; Unlocks Proper Drift Mode

August 14, 2019 by Lewin Day 7 Comments

The last few years have seen a huge rise in the prominence of electric scooters. Brushless motors, lithium batteries, and scooter sharing companies have brought them to the mainstream. However, electric scooters of a variety of designs have been around for a long time, spawning a dedicated subculture of hackers intent on getting the best out of them.

One such hacker is yours truly, having started by modifying basic kick scooters with a variety of propulsion systems way back in 2009. After growing frustrated with the limitations of creating high-speed rotating assemblies without machine tools, I turned my eye to what was commercially available. With my first engineering paycheck under my belt, I bought myself a Razor E300, and was promptly disappointed by the performance. Naturally, hacking ensued as the lead-acid batteries were jettisoned for lithium replacements.

Over the years, batteries, controllers and even the big old heavy brushed motor were replaced. The basic mechanical layout was sound, making it easy to make changes with simple hand tools. As acceleration became violent and top speeds inched closer to 40 km/h, I began to grow increasingly frustrated with the scooter’s one glaring major flaw. It was time to fix the brakes.

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Electric Dump Truck Tricycle Is No Toy

August 13, 2019 by Bryan Cockfield 31 Comments

There are some utility bicycles on the market, some with electric motors to help carry a good bit of cargo. If you really need to haul more weight than a typical grocery-getter like this, you’ll want to look into a tricycle for higher capacity loads. Nothing you’ll find will match this monstrous electric tricycle hand-built by [AtomicZombie] out of junkyard parts, though. It’s a mule.

Since [AtomicZombie] sourced most of the underpinnings of this build from the junkyard, it’s based on an old motorcycle frame combined with the differential from a pickup truck, with a self-welded frame. He’s using an electric motor and a fleet of lead acid batteries for the build (since weight is no concern) and is using a gear reduction large enough to allow him to haul logs and dirt with ease (and dump them with the built in dump-truck bed), and even pull tree stumps from the ground, all without taxing the motor.

[AtomicZombie] documented every step of the build along the way, and it’s worth checking out. He uses it as a farm tractor on his homestead, and it is even equipped with a tow hitch to move various pieces of equipment around. Unlike a similar three-wheeled electric contraption from a while back, though, this one almost certainly isn’t street legal, but it’s still a blast!

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Automate The Freight: Platooning

August 13, 2019 by Dan Maloney 34 Comments

On yet another one of those long, pointless road trips that seemed to punctuate my life starting when I got my license, I was plying the roads somewhere in eastern Pennsylvania with a friend. He told me that on long trips he’d often relieve the boredom by finding another car from the same state as his destination, and then just follow it. I wasn’t sure then how staring at the same car, hour after hour, mile after mile, would do anything but increase the boredom while making you look sort of creepy, but it seemed to work for him.

What works for college kids in cars also works for long-haul truckers, and the concept of a convoy has long been a fact of life on the road and a part of popular culture. Hardly a trip on the US Interstate goes by without seeing a least two truckers traveling in close formation, partly for companionship and mutual support but also for economic reasons. And now technology is poised to take convoying to the next level, as platooning becomes yet another way to automate the freight.

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