How does that work?!? Check out the chainless NuBike

The chainless NuBike is a design that has been around for some time now, but we thought we’d show it to you just because it’s so unusual. Some might call it downright strange.

NuBike is an idea from US inventor Rodger Parker. Rather than a traditional chain drive system, it uses two long levers connected to a gearbox that converts your up/down stepping motion into rotational movement at the rear wheel. That’s the gist of it.

The obvious question: why?

Rodger Parker claims that NuBike goes faster than a normal bike with less effort.

“The first advantage is leverage,” he says. “NuBike’s pedal cranks deliver two and a half times more power to the rear wheel using leverage.”

The argument is that NuBike’s longer levers deliver more force. Granted, a longer moment arm will reduce the moment force that you have to put in to get the same output, but generally we just use gears (as Nubike can) to control the input force independently of the output force, no matter the length of the crank or moment arm.

“The second advantage is the use of gravity,” according to the inventor. “The rider’s weight provides forward motion throughout the entire pedal stroke, not just for part of it.”

We've seen vaguely similar arguments for the use of Rotor Q Rings which are designed to enhance torque production during your pedal strokes, but that's a whole other can of worms that we're not going to get into here.

Rodger Parker also reckons that the NuBike system results in less drag and less maintenance, and says, “With linear motion, there’s less stress to the body, so less blood oxygen requirements to the legs, less strain on the heart, and less flexing of the hips, knees and ankles.”

If you’re cycling for fitness, part of the appeal is that it challenges your muscles and cardiovascular system, but Rodger Parker says that part of his motivation for developing the NuBike was that his wife “ended up with a knee problem likely caused by years of extensive riding”.

We're not going to go into a full critique of the science – this is just a quick Bike at Bedtime – but you can check out NuBike's YouTube videos for all of the claims and see what you think. We'd be interested in your comments.

We've not swung a leg over the NuBike so we can't comment on the performance. We can tell you that the use of treadle-type systems to transfer power to the rear wheel is far from new. The American Star Bicycle used independent treadle mechanisms back in 1880, for example, and then there was the more recent Alenax bike that prompted the late engineer and cycling guru Jobst Brandt to write, “I think the inventor (and investors) did not realise that converting reciprocating motion into circular motion is best done by a rotary crank rather than a reciprocating lever, and above all, they weren't bicyclists.”

There are plenty of other examples out there, but NuBike’s system has its own patent which says, "The mechanism includes a crank lever, which when forced by the driver’s legs, pushes a drive arm that, in turn, rotates a drive wheel. The rotation of the drive wheel transmits a torque to the bicycle’s rear wheel via a gearing mechanism.

“This invention is… a bicycle propulsion mechanism... whose crank levers are much longer than those of a conventional bicycle, provide excellent ergonomics, makes a highly efficient use of the power transmitted by the rider, and which uses relatively few parts for a smooth, reliable, and highly adaptable mechanism."

The patent claims that "one improvement offered by the invention is that many frame elements in a double-triangle frame configuration, such as a chain stay, seat tube, bottom bracket, and down tube, can be eliminated and [it] thereby allows a reduction in weight.”

A built-in mechanism “prevents horizontally opposed lockup of the drive levers by advancing one pedal at the top of the stroke and retarding the opposite pedal at the bottom”, according to NuBike. This is also designed to provide “a smooth, natural transition from one stroke to the next”. 

Rodger Parker reckons that a carbon-fibre NuBike frame weighs less than 1.36kg (3lb) and the gearbox that converts linear pedalling to rotational motion “weighs less than the chain and sprockets of a 10-speed”. A complete road bike is a claimed 8.16kg (18lb).

When it comes to fixing a flat or putting NuBike into the back of a car, removing the rear wheel is said to be quick and simple: you just open two quick-release levers and disconnect the shifter cable.

 

 

 

 

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What about hills? The patent says, “The invention is adaptable to bicycles using a conventional gear cassette, an internal gear hub, or any of the numerous gear configurations known in the art.”

You’ll see that “known in the art” phrase in patents all the time. It simply refers to designs that are already out there.

The NuBike in the video (above) is a 4-speed system that allows you to customise your ratios. The design also lets you coast.

> L-shaped cranks — explore the crazy idea that just won't die

Is NuBike ever going to set the market alight? Don't hold your breath for that one. When looking for £275,000 investment on Kickstarter five years ago, it received pledges of £3,000 so funding was unsuccessful. Be honest, though: you'd still like to give it a quick blast, wouldn't you?

Check out loads more Bikes at Bedtime here. 

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