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Spokeless bicycle adds some 'cool' to pedal power

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February 16, 2010

The spokeless bicycle was the brainchild of nine Yale seniors from an engineering class

The spokeless bicycle was the brainchild of nine Yale seniors from an engineering class

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Usually, when you put nine university seniors together from a mechanical engineering class in a room for a whole semester with no strict agenda, the last thing you expect to get is a useful product. But this team broke the mold and created a “human-powered spokeless bicycle”. Admittedly, only the back wheel is spokeless, but the Yale students had two very good reasons for that – time and money.

It ain’t pretty, but the students admit they just didn’t have time or the cash to spend on niceties like paint jobs, suspension, gears or even a second brake. All they wanted to do as part of their mechanical engineering class at Yale was prove that it was possible to build a human-powered spokeless bicycle - something they seem to have accomplished with this prototype.

As readers will notice, only the back wheel is spokeless. This was due to time and money constraints. The class only ran for a semester and manufacturing the rear wheel/rim was very expensive, so only one was machined to see if it would work.

One of the students, zhaolander, explained the reasoning behind the concept of the spokeless bicycle via reddit, “First, it looks cool. Second, we only had a semester so we wanted to pick something that was both feasible and challenging. Also, you can do a lot of things with the space that opens up where the spokes use to be. You can stick an electric motor in there. You can install some sort of gyro balanced storage basket. Finally, the fact that we couldn't find pictures of a real spokeless bicycle online really sealed the deal.”

The spokeless bike is a single speed unit that uses two cranks and two bottom brackets in the front to gear up the ratio. In bike parlance it goes from (IIRC) 53 to a 13, which is connected to the second crank and another 53 that connects to the rear hub. The rear hub is a ratcheting rear hub that is mated to the belt pulley.

The students admit that on this model the balance is a little off – it’s rather back-heavy – which does affect the performance of the bike when turning. However, if the front wheel was also spokeless it would help even things out. This is even though the the front wheel could be made a little lighter as some of the aluminum could be shaved off since there's no powertrain to connect to.

The 26-inch wheel/rim itself is made from T6061 aluminum, while the frame was water jet cut out of 1/8" thick aluminum alloy to keep the cost down. The team responsible for building the bike currently have no further plans to develop the bike, but zhaolander teases, "tons of improvements could be made in future (another class perhaps)".

Via Reddit and Crunch Gear.

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8 Comments

talk about reinventing the wheel! This is definitely a solution waiting for a problem.

felix
17th February, 2010 @ 01:18 am PST

Well executed solution to a problem that doesn't exist. Yes it's spokeless, but where's the actual benefit. The classic chain driven spoked wheel is a marvel of engineering efficiency, with power loss in the 2-3% range, an excellent strength to weight ratio, low rotational weight, and resilience for shock absorption and traction.

When dealing with the low power available in human powered vehicles, efficiency is the most critical element, there simply isn't the extra power to waste as we've gotten used to in the automotive world. The typical rider produces less power than most cars use in their audio systems alone.

So I give them an A for cool factor and execution, and an F for practical analysis of the real needs of the application.

Francis Bollag
17th February, 2010 @ 06:15 am PST

Hello:

This is nothing new. The Swiss designer Sbarro build a spokeless motorcycle and also bycicle in the late '60's, i should look the articles up. With Sbarro BOTH wheels were spokeless. The idea was shelved because of cost and the higher unsprung weight.

I do have pictures of them, will look it up.

Andre
17th February, 2010 @ 09:23 am PST

One of the main purposes of the spokes on a wheel is to increase the strength of the rim without excessive weight. Because this wheel assembly is so heavy, it fails on this account alone!

Ed

Ed
17th February, 2010 @ 04:35 pm PST

Also - do you know how dangerous spokes become in bike crashes? I know of a couple of people who've had them go through their calf muscles.

Joshua Smallwood
17th February, 2010 @ 08:56 pm PST

This almost looks like the first bike ever built. A triumph of concept over common sense. By the way, Joshua, a spoke through the calf sounds like the most minor injury in what must have been a horrific crash. When you think about it, why do you need a large wheel at the back. What does it actually do? I suppose it has some ratio effect.

windykites1
18th February, 2010 @ 11:52 am PST

If publication on Gizmag is encouragement to current undergraduate Mechanical Engineers to try and build a design of their own, on their own, then this article is worth reading. I've seen graduate projects where in drawings of their solution, dimensions are carried out beyond 6 decimal places, and no it was not needed. There is a learning process involved when trying to build something that is just not absorbed in the classroom. I'm not convinced all the changes in the classrooms are in the right direction, I met a fellow who made his own drill press, castings and all, in his undergraduate education 30 odd years ago.

I hope that these students did indeed learn the processes behind the welding of their aluminum frame to the turning of the rear wheel hub. I am encouraged that it appears they built around an existing part, the drive belt when determining the wheel's dimensions. That is cool and smart thinking, building around something commercially available saves time and money. I am surprised they chose to use the top of the wheel, in literal terms, that's like log rolling. Not the most stable design. Think of the force direction of going over a bump... and then think of the distance from the tire contact of that bump and the resisting mechanism all the way at the top of the wheel. Not excitingly new, but refreshing nonetheless.

CreativeApex
19th February, 2010 @ 06:29 am PST

It seems like Lotus Sport 110 from 1994.

See on http://www.grouplotus.com/engineering/lotus_heritage.html

Sergius
26th February, 2010 @ 07:35 am PST
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