[LAU] A crazy idea

Joseph Sheedy joseph.sheedy at gmail.com
Fri Mar 5 02:14:54 EST 2010

You should check out the S.F. Bicycle Music Festival

They cycled from San Francisco all the way to Vancouver, B.C. with
bands and a bicycle powered PA system.   I caught them here in Seattle
and helped broadcast a singer in a cargo trike during a parade over my
bike sound system via FM transmitter.   They set up 3 stationary bikes
attached to generators with ultracaps to power a PA system for shows
in parks and wherever.

I didn't have my 12" JBL subwoofer bike system with me at the time,
but it requires a lot more power than my legs can put out :)


On Thu, Mar 4, 2010 at 1:48 AM, Jonathan Gazeley
<jonathan.gazeley at bristol.ac.uk> wrote:
> Morning LAU,
> As I cycled to work this morning, I had a crazy idea. It's just
> daydreaming and will probably never happen, but I wondered if anyone on
> the last has any useful/interesting thoughts.
> I want to measure how fast I'm turning the pedals on my bike (the
> "cadence") and synthesize/sample the sound of an internal combustion engine.
> As far as I can work out, there are three major parts to this.
> 1. A sensor that can measure my cadence. A simple magnet switch that
> triggers once a revolution won't be enough to measure the cadence with
> sufficient resolution, since my cadence is usually between 50 and 80
> rpm. I would probably need to mount multiple magnets spaced equally
> around the chainwheel and have a single sensor on the frame. Then I have
> to get it to supply this information to my control program.
> 2. I need a control program that can read in the input from my cadence
> sensor and convert a cadence reading of "66 rpm" into a frequency that
> should be sampled/synthesised, e.g. "500 Hz" (I'm making these numbers
> up). It will also need to be able to somehow smooth out the readings,
> perhaps by interpolation, so when I accelerate, the sound of the revs
> climbing doesn't increase in obvious steps. It could also have other
> logic, e.g. when my cadence is 0 rpm, the sound of the engine is idling
> rather than off.
> 3. I need a synthesiser or sampler that can take an input from my
> control program and make the sound of an engine (or more likely, a sine
> wave to start with). I've never sampled or synthesised on a computer
> before but this engine-specific sampling technology already exists in
> video games, such as torcs[1].
> I have absolutely no idea why I would want such a device - just for the
> fun of building it, I guess. I would like it to work in realtime (rather
> than later generating the soundtrack from recorded cadence data). The
> thought of sitting at the traffic lights with my earphones in and then
> hearing the mighty roar of a V8 as I pull away would be really satisfying...
> [1] http://torcs.sourceforge.net/
> Any thoughts - useful, interesting, humorous, or otherwise - are welcome!
> Cheers,
> Jonathan
> ----------------------------
> Jonathan Gazeley
> Systems Support Specialist
> ResNet | Wireless&  VPN Team
> Information Services
> University of Bristol
> ----------------------------
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