A pot probably wouldn't stand up to the rigours of cycling.... it would be better to find some other type of sensor - optical or magnetic would probably be favourite. Chris ----- Original Message ----- From: To: Sent: Tuesday, November 26, 2002 4:30 PM Subject: Re: [OT]: Bike gear ratios > Now, force feedback is an interesting complication I haven't considered! > That would certainly make the project extra complex if it is needed. > > I think sideways forces on a bicycle wheel are usually minimal, except > when you are going down a track full of ruts. This is no off-road bike, > so I won't worry about that possibility just yet. I am imagining the > rider is more involved with feedback from the vestibular system than the > hands. I'm tempted to hack this up just to see if it would work. > > Now I have worried a little about what kind of sensor to sense the > position of my underseat handlebars with. The handlebars themselves will > be a conventional carbon fiber straight handlebar in a conventional > gooseneck bearing welded onto the frame. You need lots of strength in a > handlebar because the rider pulls on the bars to oppose the legs. The > sensor has to accept getting wet, and either has to accept 360 rotation or > be arranged with a heavy duty end-stop since you have a 40 cm lever to > haul on it with. I can't imagine the end-stop torque on a conventional > pot being good enough. Rotation at least 180 degrees is essential. Is > there a waterproof pot that would fill the bill? > > > OTOH, servomotors are quite waterproof all by themselves and contain a > nice high quality pot and a beefy end-stop. Maybe I could hack apart a > small servo and couple it's pot to my PIC. I could even stick the whole > thing in the servo case! > > ANd thus we also have the makings of a force feedback system. Big servo > drives the steering wheel, and a signal off the big servo feeds back to > the PIC processor. PIC drives the little servo which is coupled to the > steering bar. Signal off the little servo POT drives the PIC which runs > the big servo. > > Now, can any one spell O S C I L L A T O R ? I can imagine this thing > going down the road flapping, or getting unstable at certain speeds. > > -- Lawrence Lile > > > > > > Bob Ammerman > Sent by: pic microcontroller discussion list > 11/25/02 07:22 PM > Please respond to pic microcontroller discussion list > > > To: PICLIST@MITVMA.MIT.EDU > cc: > Subject: Re: [OT]: Bike gear ratios > > > 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. > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body