Motorcycle Builder Makes Downhill Mountain Bike

[Allen Millyard] is a premier British motorcycle builder. In these circles he is widely regarded and his custom motorcycles are nearly world-famous. But when his son took up downhill mountain biking, he decided to put his skills building a different type of vehicle. This is the Millyard MR001, one of the most unique mountain bikes ever built thanks to some design choices that solve many problems otherwise inherent in bicycles.

Perhaps the most immediately striking design of this bike is the aluminum space frame, a lightweight but extremely strong frame necessary for the high speeds and stresses of downhill mountain biking. Upon closer inspection, however, the sealed drivetrain warrants further inspection. Unlike most mountain bikes with gears, this one eliminates the typical derailleur which hangs below the rear gears. The gears are instead above the pedals in front of the rear tire, are completely sealed eliminating the maintenance requirements of a typical bike, and are designed in such a way that they can be shifted without the bike moving.

Despite the bike being built in 2007, it still includes plenty of features that still aren’t widely adopted in mountain biking. It’s also nearly completely silent thanks to the custom drivetrain, and [Allen] reports that it still sneaks up on other mountain bikers as a result. This is essentially the opposite problem of another bike we’ve seen around.

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Riding Mower CVT Upgrade Really Gets Things Moving

As we’ve learned from past experience, videos from [HowToLou] tend to be a bit controversial. His unique style of expedient engineering isn’t everyone’s cup of tea, especially when it’s combined with a devil-may-care attitude towards safety. On the other hand, there’s no arguing that his methods get results. His video on converting an 18 HP riding mower into something akin to a go-kart is a perfect example.

The first phase of the project involves removing all the hardware related to mowing, as obviously you won’t be cutting any grass while pushing speeds of 48 kph (30 mph). This both saves weight, and removes a lot of mechanical complication that would be in the way of further modification. That said, it also leaves the mower immobile, as there’s no longer be any connection between the engine and transaxle.

The new drivetrain features some beefy bracing.

In its place, [HowToLou] installs an off-the-shelf torque converter kit that uses a continuously variable transmission (CVT) clutch. As he quickly demos, the CVT technology allows the gear ratio to automatically adapt to the engine RPM thanks to pulleys that change their size depending on how fast they’re spinning. It’s a big improvement over the system he originally yanked out, though as you might expect, fitting it into the mower required some custom work. The final step was to pull the old pulley off of the transaxle and replace it with one that’s less than half the original size.

Wearing his protective flip-flops, [HowToLou] hops on the souped-up mower and is nearly thrown off the back of it as soon as he steps on the gas. Clearly the modifications were a success, and the video ends with some open road testing — presumably he’s riding off to the store to go buy a helmet.

We actually missed this video when it first made the rounds, but it has since picked up steam and is pulling in some impressive numbers. [HowToLou] tells us he thinks it’s due to the fact that a lot of people are upgrading to more modern zero-turn mowers, meaning there’s a surplus of these second-hand mini tractors on the market. Whatever the reason, we’re happy to see this backyard engineer get some mainstream success; his methods might not always be by the book, but they’re always entertaining.

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Ball CVT Drives Robot From A Constant Speed Motor

[James Bruton] is experimenting is a series of interesting mechanical mechanisms, the latest being a CVT transmission system which uses a tilting sphere to get a variable speed output from a constant speed input. Video after the break.

In [James]’ proof of concept RC vehicle, a single powered disc is mounted on top, at 90 degree to the wheels. A rotating sphere makes contact with both the driven disc and the wheel. When the rotation axis of the sphere is at 45° between the disc and the wheel, it provides a one 1:1 transmission ratio. As the axis is tilted, the contact points on the sphere shift, changing the relative circumference at the contact points, and therefore changing the transmission ratio. It can also reverse by tilting the sphere in the opposite direction, and disconnected from the output wheel by aligning it with the hole in the bottom of the sphere. [James]’ simple two-wheel RC car concept quite well, driving around his kitchen with the transmission spheres being tilted by servos.

Thanks to the response time, CVT gearboxes are generally not needed for electric motors, but on internal combustion engines that which run best within a certain RPM range they can be very useful. One possible weak point of a design like this is it’s dependence on friction to transfer torque, which makes it vulnerable to wear and slipping.

This build is a spin-off of his spherical omni-wheels and the robot chassis he developed around them. For another interesting robot mechanism, check out is gyroscope balancing system. Continue reading “Ball CVT Drives Robot From A Constant Speed Motor”

Can The Solenoid Engine Power A Car?

[Emiel] aka [The Practical Engineer] makes all kinds of fun projects in his fully-featured shop, and one of his tangents has been building a series of solenoid engines. These engines mimic the function of an internal combustion engine, with each solenoid acting as a piston. The only problem with [Emiel]’s concept engines, though, was that he never actually put them into a vehicle to prove their effectiveness. This build finally proves that they can work at powering a vehicle.

The project starts with a new engine. [Emiel] chose a V4 design using four solenoids and an Arduino-based controller. After some trouble getting it to operate properly, he scavenged a small circuit board he built in his V8 solenoid engine to help with timing. With that installed, the solenoids click away and spin the crankshaft at a single constant speed. The vehicle itself was mostly 3D printed, with two aluminum tubes as support structures to mount the engine. Even the wheels were 3D printed with a special rubber coating applied to them. With a small drive train assembled, it’s off to the races for this tiny prototype.

While the small car doesn’t have steering and only goes at a constant speed, the proof of concept that these tiny electric engines actually work is a welcomed addition to [Emiel]’s collection of videos on these curious engines. Of course they’re not as efficient as driving the wheels directly with an electric motor, but we all know there’s no fun in that. If you haven’t seen his most intricate build, the V8 is certainly worth checking out, and also shows off the timing circuitry he repurposed for this car.

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This Robot Swims, Skates, And Crawls

You often hear that art imitates life, but sometimes technology does too. Pliant Energy Systems’ Velox robot resembles an underwater creature more than it does a robot because it uses undulating fins to propel itself, as you can see in the video below.

The video shows the beast skating, but also swimming, and walking. It really does look more like a lifeform than a device. According to the company, the robot has excellent static thrust/watt and is resistant to becoming entangled in plants and other debris.

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