cb250nproject
If you can make it better do so
jpmobius said:Very nice project! I'm afraid you will need to do a bit more work on your shift linkage though. The driving and driven links need to be much closer to being parallel to each other. (Red lines in pic) They do not have to be exactly parallel, but much closer than you have them. You can't adjust the driving link without cutting and welding or changing the pedal location, so you have to work around that. Ideally, the angle between the driving and driven crank arms and the connecting link would be 90o, but there is also a bit of leeway here and this likely will be ok. I realize that you have a very nice 90o angle between your crank arms and connecting link, but the 90o needs to be between the crank arms and a straight line between them. This is the theoretical or imaginary dark green line in my pic. Often as you know, this straight link is not possible to fit, but for design purposes, you must think about the link as if it were straight. No matter what the shape of the link (light green line), the function (discounting strength/flexibility issues born from the shape) is as if the link were straight. If you draw a straight line for the link on your existing setup (I didn't make a line for this), you will see that when you push down on the pedal, you won't be rotating the driven link very much. Easy fix though. Just rotate the driven crank to match the driving, and create a new connecting link. Making the bend in it as small as you can (orange line) will make it flex less. And once you are driving the bike, you will find making very small changes to the angles of the components can make a big difference in the shifting quality.
Yea the gear linkage was a tricky set up for a few reasons
First was how much backward travel I had when pushing the lever upwards before I would hit the rear side of the chain guarding.
The next issue was that when you would push the lever down wards causing the linkage to travel forwards the linkage hits on the foot peg housing, this in turn acts as a fulcrum causing the linkage to go up.
There is a very small sweet spot in which the linkage will; A not hit the housing causing it to go up, and B still actually change the gears both up and down.
How you see it in the photos is actually in that sweet spot.
Although I am yet to ride it (for obvious reasons) I will have to wait to see if it impacts on riding comfort. I’m. It particularly concerned about the linkage breaking due to it being under excessive force, give there is so little pressure required to select gears.
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