Comments on: The NuFixie Challenge: Can you build a fixed-effort bicycle?

By: How to iterate towards your ideal commuter

How to iterate towards your ideal commuter — Sun, 19 Apr 2009 22:58:34 +0000

[...] holder now holds my sound system. I’m still waiting for the opportunity to turn it into a NuFixie. Lest it should sound like I now ride a completely different bike, I will point out that these [...]

By: shannon

shannon — Mon, 29 Dec 2008 17:25:54 +0000

looks like Fallbrook have at least part of the answer to your quest…
http://www.fallbrooktech.com/09_lev_kit.asp
It’s a cool idea I think that a constant cadence should be the optimal measure of ‘effort’ and this new electric bike from iZip sort of covers the idea too click on the EVO express bit: http://www.izipusa.com/efacts.php

By: David

David — Tue, 09 Sep 2008 06:06:21 +0000

You would want to change gears based on speed, not torque. Otherwise it would change to higher gears based on the amount of pressure you applied to the pedals, not on the speed. You would have to inversely control the gear ratio according to pressure, the greater the pressure the lower the gear. Why do that when the end result is that you want to control speed. Cadence is the same thing as speed. Your steps are cyclic, and are translated into rotation of the wheel, same thing.

By: Crankzone » Dwell, the Trailcart, and a challenge

Crankzone » Dwell, the Trailcart, and a challenge — Sat, 05 Jul 2008 18:57:20 +0000

[...] and Bikes blog has a question/challenge for all you designers and engineers who might be reading: Can you build a fixed-effort bicycle? The idea, which he is calling “NuFixie”, is to build up a bike that uses the NuVinci CVP hub, [...]

By: Efried

Efried — Sat, 07 Jun 2008 21:58:37 +0000

Well I rode the NuVinci. and I find it too heavy- would love to have a leaner solution- possibly without a chain

By: ari

ari — Thu, 05 Jun 2008 14:13:51 +0000

Ron, thanks again for your analysis! For those of you who haven't take a look at Ron's blog post, I highly recommend checking it out: http://cozybeehive.blogspot.com/2008/06/all-automatic-cvt-based-bicycle.html. A number of thoughts, suggestions, and links have been raised in comments, and I haven't gotten a chance to read through all of them yet. The ones that stuck out for me were:

Iain Crouch. Optimal gear selection on an automatic bicycle. (published in Human Power, Number 55, Winter 2003-2004)
Joe Friel. Training with Power. (geared towards racing, but still relevant)
Jian-Wei Cheng and Brandon Stanley. Automatic Bicycle Gear Selector. (A senior design project at UIUC)
Chester R. Kyle. The Browning Automatic Bicycle Transmission. (Reproduced from: Cycling Science, Winter 1995)
Finally, I should add to the list one more: David Gordon Wilson. Bicycling Science. (Chapter 9 is on power transmissions)

I'll reiterate that I don't have the knowledge or materials to build the NuFixie myself, but I'm certainly enjoying the discussion. Perhaps an enterprising engineering student or two can take up this challenge for a future class project?

By: Ron

Ron — Thu, 05 Jun 2008 05:03:42 +0000

Hey, I hope you’re checking the comments section on my blog. More ideas and links are coming in.

This is a fun project, making things simple first would be the way to go for a prototype.

The aim of the project, and I hope yours too, is not to increase speed or decrease weight, but to improve COMFORT in bikes, primarily through an all automatic “intelligent” shifting utilizing a Nuvinci hub, and programming. That said, Nuvinci is not for race bikes, it clearly has its niche and I hope the company recognizes too that its not competing in that market.

By: Chris Lyon

Chris Lyon — Wed, 04 Jun 2008 13:09:00 +0000

A couple of thoughts:
Each of us has a power output sensor: our legs. The feedback loop can be a simple as a cadance sensor with a +/- range. Set it for 100, and as the load increases, your legs slow, and the shifter downshifts – and tother way around.

Therefore, we need a power supply, programmed chip, an input device, and a servo mechanism

By: Ron

Ron — Wed, 04 Jun 2008 05:12:26 +0000

Hi Ari.

I wanted to respond to your idea. Very interesting. Too long to type here though.

Visit my blog post for my reply

Dan : CVT and the existing auto transmissions you mentioned are not the same.

By: bits and bikes: NuFixie Challenge | BikeHacks

bits and bikes: NuFixie Challenge | BikeHacks — Mon, 02 Jun 2008 08:01:37 +0000

[...] RSS feed. You can also subscribe to BikeHacks by email. Thanks for visiting!Ari over at the blog bits and bikes is looking for some help. He has an idea for a new drive train and is interested in reader [...]