I would think a bicyclist is depending on force feedback from the steering gear. This would complicate a steer-by-wire system. Bob Ammerman RAm Systems ----- Original Message ----- From: To: Sent: Monday, November 25, 2002 10:47 AM Subject: Re: [OT]: Bike gear ratios > While on the subject of bikes, I have a project I have been kicking > around. I've built a number of recumbent bikes, some with underseat > steering and some with a conventional handlebar on a really long > gooseneck. > > The long gooseneck models are easy to build, but suffer from excessive > weight. The rider can pull very hard on the handlebars, and so I end up > beefing up these components so they weigh quite a lot. Also, brake cables > become excessively long, and the back brakes hardly operate at all because > they stretch. This is also sometimes a problem on tandem bikes with long > cables. > > Underseat steering solves both problems nicely. The handlebars are under > the rider's seat, brake cables are shorter than a regular bike and thus > stiffer. Another advantage is the arms hang at a natural angle. Folks > like me with carpal tunnel appreciate it when our hands are used in > relaxed, natural positions, as opposed to bearing weight on a regular > bike, or up in the air. > > Underseat steering has one complication that is a showstopper, though. You > must have some linkage from the handlebars to the front wheel. I have > used cables, rods, and various other things. Any play in this system can > result in wierd oscillations in your front wheel. These oscillations > usually kick in at high speeds going downhill. They can get really scary. > > > The forces involved in steering a bicycle are really quite small. though. > I usually steer my recumbent with one finger. One hangs on to the > steering bar more for support, or to oppose pedaling, than to steer. > > I keep imagining an underseat steering mechanism with a servomotor > connection to the front wheel, a steer-by-wire system. It is not hard to > find standard servos which will handle 300 oz-in of torque, seems like > plenty. Most steering is actually very fine adjustments, not gross > movements. I can imagine a system which would monitor it's own battery, > and alert the user if the battery was low. Seems like a really > interesting project. > > > -- Lawrence Lile > > > > > > "Peter L. Peres" > Sent by: pic microcontroller discussion list > 11/23/02 04:10 AM > Please respond to pic microcontroller discussion list > > > To: PICLIST@MITVMA.MIT.EDU > cc: > Subject: Re: [OT]: Bike gear ratios > > > On Sat, 23 Nov 2002, Jinx wrote: > > *>> Apparently there is a french company called Mavic Mektronic that > *>> makes an electronic gear change system for bikes with Derailleur > *>> type gears. Uses a push button on each handle bar, one for up, one > *>> for down shift - F1 paddle change style > *> > *>I'd heard about something on the market but hadn't looked into > *>it too seriously, thanks for the link. I reckoned a couple of steppers > *>with worm gears could do it, kind of like machine heads on a guitar, > *>there's not that much tension in the wires > > Last time I used a bicycle and tinkered with the derailleur gear mechanism > I found out the hard way that the wire tension is 3-4kgf-ish. > > The force required for the torpedo-style (in-hub) gear changers is much > lower, but with 2kgf peaks and some continuous tension. > > Peter > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.