I attached a sketch of what I envision the bell-crank solution being. I'll try to describe it also... A tab extends rearward from the pivot. Crank arms are mounted outboard on either side, and oriented such that one leg extends rearward, and the other extends out (left or right) from the pivot. Moving the outboard end of the crank arm from front to rear will turn the front wheel from left to right. A rowing oar setup is used to create this motion. Another analogy is the ball & socket orientation of a shifter in a manual transmission car. It pivots at hip height and the levers extend up to your hands. But what advantage does this have over just attaching bars to the front half of the bike? Is the goal to gain greater mechanical advantage, so that a larger hand motion results in a smaller wheel movement? It looks like the Resatec pivots are constructed with two pieces of square tubing. One is small enough so it can freely rotate in the other. The inside piece is oriented at 45 degrees to the outside, and the space between them is filled with rubber. That way it can go through small rotations, but still hold it's position reasonably well. That's my take on what it is anyway. The picture here helped me... http://www.resatec.com/index1.html p.s. I'm a long time lurker, and have been wanting to build a python for the last 10 years or so. Hopefully my life is coming to a point where I can make it a reality! ________________________________ From: Logan Streondj <weyounet@xxxxxxxxx> To: python@xxxxxxxxxxxxx Sent: Saturday, June 1, 2013 8:30 PM Subject: [python] Re: Geared Steering George, I'm not sure how the bell crank and link rods would work, since they change the direction of a straight line of motion, whereas here we need to change direction of a turning motion, so bevel gears seems more appropriate. If you do know how it'll work, perhaps you could make a picture of the concept. The rubber pivot idea is curious, though I don't know how to implement it, if there was some kind of tutorial or at least pictures/videos of it in action would make more sense. Gerald, yes so the legs can help with steering, by changing angle between stern boom and forward wheel, So I'm wondering if perhaps can use clipless pedals on forward wheel, and handle-bars on stern boom, to allow steering while going downhill, or when using electrical assist without pedalling. An alternative to clipless pedals, maybe a spot where can hold the front wheel with feet, perhaps by squeezing it between feet. That would certainly be an easier solution, than having gears, and may achieve similar results. On Sat, Jun 1, 2013 at 3:56 AM, Gerald <bepb@xxxxxx> wrote: >Hi Logan, >there is certainly Jürgens orginal construction >page:http://www.python-lowracer.de/construction.html >Also, there is some info on the Python WIKI: >http://en.openbike.org/wiki/Main_Page. > >Concerning the lever system, I think you will face the same issue as with the handlebars. If you want to steer with the levers, you have to counteract the forces extended by your legs. >I like to point out, that with some practice, the legs only steering becomes very comfortable. > >BR >Gerald > > > > > > > > >On 30.5.13 17:28 , Logan Streondj wrote: >hmmm, I don't think a damper would really do the trick. >> >> So guess the gears and levers is worth attempting, would probably cost 15-30 for the gears, and some more for the levers, though can probably just use some bike frame parts. >> only thing gotta figure out now is some kind of pivot for the side gears, though guess it could just be some kinda short pipe that flares out or has a cotter pin at the end, >> that may interfere with the lever placement, though guess the "green" housing can simply be around that part so it should work. >> >> I'm hoping to get a chance to build a python this summer, can probably use my parents backyard, since my apartment doesn't have anywhere to do welding. >> >> Is there a listing of python building tutorials somewhere? I like to read up on as much information as I can usually before doing something. >> >> >> >> >> >> >>On Wed, May 29, 2013 at 2:28 AM, Steffen Risse <big.skangster@xxxxxxxxx> >>wrote: >> >>Pay attention that you don't understand me wrong please. if you lock the >>pivot on a bike it's sure that you'll fall over. On a trike it's less a >>problem. The thing is just to dampen fast big movements especially at high >>speeds. A possible solution comes from the motorbikes: steering damper @ ebay >>(Lenkungsdämpfer) Make sure you're not using the spring ones for the ladies >>bycicles, because there's no damping included. >>> >>> >>> >>>2013/5/29 Logan Streondj <weyounet@xxxxxxxxx> >>> >>>Steffen, that sounds like a pretty good idea, a steering brake. >>>> maybe even a cheap calliper break, with rounded pads would do the trick. >>>> assuming can make steering adjustments with legs, >>>>the steering brake would then hold the adjustment. >>>> likely can have the steering brake at the left side, >>>> >>>>so can use the rear/main brakes on the right side, simultaneously. >>>> >>>> considering that using a brake is a simpler solution, it's probably the better one also, fewer moving parts and components, next I guess it would be good if someone could try it out, though I'm not sure how it would be mounted, or even how to keep a certain part of the pivot exposed to allow for applying the brake pads, I'm sure there must be a way. >>>> >>>> >>>> >>>> >>>>On Wed, May 29, 2013 at 12:54 AM, Steffen Risse <big.skangster@xxxxxxxxx> >>>>wrote: >>>> >>>>Just a thought from a python triker: Maybe the steering bar is the wrong >>>>point to work on for high speeds. When I built my trike I used my old first >>>>try on a python frame and combined it with a wheelchair. While completing >>>>it with parts I didn't greased the bearings for the steering pivot. Half a >>>>year later I greased them. After that I noticed a big difference while >>>>coasting down one of the bridges here in Berlin. The bike was more nervous. >>>>It also hadn't a slip-stick like behaviour anymore. Maybe a steering damper >>>>whould therefore help more than a steering bar on the frontpart. The >>>>problem is, that the damper might has to be connected to the speed. Some >>>>variable friction in the steering system could might help - like a brake on >>>>the steering. >>>>>Cheers, >>>>>Steffen >>>> >>> >> > >
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