A new shift concept for the engineers....

Right, so if you put on the SA s3x flipped so it drives on the left and put on a 36 or 40 tooth for example, that would be your highest gear or 1:1 on the 3 speed fixie (in third gear would be like having a 40 tooth connected directly to your motor). I think I got that...

What do you do with the pedal side? you'd need to be able to put a gear with a freewheel on the right ALSO, correct? I'm new to this and trying to understand...would that be hard to do?

OK, so say you got that all worked out. I read earlier that someone is convinced that the SA 3 speed would not hold up? Regular bike parts seem to hold up on the SBP shift kits. I guess that's due to some gear reduction on the jack shaft?
 
gareth5000 said:
I found another way round this problem. Drive the front sprocket and use the gears you've already got.
I've got a shimano 4 spd auto rear hub to try as soon as I get it laced up. I think auto would be cool.
Click to expand...

Whoa whoa whoa there! More information on your drive system is needed. That thing looks friggin COOL!

Do you have some kind of a bevel gear system?
 
silverbear said:
Hey Jim,
Understood, and that's how things should be with business first. Hopefully the sprocket cluster shift prototypes will work out and eventually become part of your production runs. All good things are worth waiting for.
SB
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I am using a standard S-A 3- sp. and it is holding up quite well. I had to run 2 JACKSHAFTS DUE TO THE FREEWHEEL DIRECTION, BUT I LIVE WITH IT.
 
I think the concept is at the point were it is being over engineered. My original hope was to come up with bolt on (rear sprocket included) I know there are currently some good things out there for gearing of the rear heel, but given that we can easily pancake a couple of different size sprockets to the left side, a simple tensioner/derailer would be nice. Three speed hubs, and jack shafts kinda get away from the original concept. I also subscribe to the idea of simple means less to go wrong which leads to higher reliability.

Currently here are the problems I see that need solving: First the chain tension, switching between sprockets leaves lots of chain to slack out. Secondly the derailer, the drive chain needs to stay above the chain stay to give the drive sprocket enough teeth to drive the chain, so copying the right side tensioner is not an option.

A few sound concepts to consider: Shifting under power may not be advisable, but because the left sprockets do not freewheel we can use the rotation of the wheel to drive the chain through the shift, similar to how the front derailer works on a regular bike. Tensioner and derailer can be two seperate units, again look at the front derailer, all it does is move the chain, rear derailer maintains tension. The two unit design would allow for a "poor man" shift kit be cause with just a decent tensioner, one could stop the bike and manual move the chain to the desired sprocket.

Just what I have so far from my tinkering, I currently have multiple sprockets, my current problem to tackle is the tensioner...
 
whats going on with the ORIGINAL plan. ??

creative designs reply please! :D


note: i think people are going away from the ORIGINAL plan with the 3 sprockets.
 
Try running two tensioners. One on top pointing up and one on the bottom pointing down. This would take care of the slack in the chain top during start and coasting and would give more room for the slack on bottom to go when using a smaller sprocket.

Just a thought, though it is early and my brain is just waking up so, sorry if I missed some obvious flaw. ;)
 
ballermj23 said:
whats going on with the ORIGINAL plan. ??

creative designs reply please! :D


note: i think people are going away from the ORIGINAL plan with the 3 sprockets.
Click to expand...

I'm still working on it.

I've been doing production runs for my distributors, so the machines have been tied up. I'll be done with production next week.

I don't have enough machines to run production and do prototypes at the same time.

Jim
 
ferball said:
I think the concept is at the point were it is being over engineered. My original hope was to come up with bolt on (rear sprocket included) I know there are currently some good things out there for gearing of the rear heel, but given that we can easily pancake a couple of different size sprockets to the left side, a simple tensioner/derailer would be nice. Three speed hubs, and jack shafts kinda get away from the original concept. I also subscribe to the idea of simple means less to go wrong which leads to higher reliability.

Currently here are the problems I see that need solving: First the chain tension, switching between sprockets leaves lots of chain to slack out. Secondly the derailer, the drive chain needs to stay above the chain stay to give the drive sprocket enough teeth to drive the chain, so copying the right side tensioner is not an option.

A few sound concepts to consider: Shifting under power may not be advisable, but because the left sprockets do not freewheel we can use the rotation of the wheel to drive the chain through the shift, similar to how the front derailer works on a regular bike. Tensioner and derailer can be two seperate units, again look at the front derailer, all it does is move the chain, rear derailer maintains tension. The two unit design would allow for a "poor man" shift kit be cause with just a decent tensioner, one could stop the bike and manual move the chain to the desired sprocket.

Just what I have so far from my tinkering, I currently have multiple sprockets, my current problem to tackle is the tensioner...
Click to expand...

I, too, would like to see the focus stay on something bolt on and simple. Allowing for the wheel you already have is a plus economically, but also you could change the setup from one bike to another pretty simply. Yes, derailleur and tenshioner, those are the keys. If two sprockets stacked makes the difference between success and failure, then two is good for a bare bones, poor guy shift option.
And if it requires stopping and manually moving the chain to the desired gearing, then that is still better than one fixed gear with no options. My thoughts in the beginning when you first suggested this possibility was that two would be adequate for me... one general purpose like a 44 tooth and one with a bit more hill climbing capability, like a 48 tooth. Keep it simple. If Jim can figure how how to make the three stack work, shifting on the go, why that would be grand, wouldn't it?
SB
 
Double tensioner yes but I don't think one top and bottom would work. You need to be able to so something with all that extra chain when it's running on the smaller sprocket and the best way to take up slack is an S.

Excuse the crudeness but what about something like this? Spring loaded on the center pivot so it can rotate to take up the extra slack.
 

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kevlarr

COOL, NOW IF YOU COULD SLIDE IT IN AND OUT, YOU WOULD HAVE YOUR SHIFTER.

INSTALL A OUTER PLATE TO KEEP CHAIN IN PLACE.

ALSO MAY NEED A CHAIN GUIDE ON TOP BY TRANNY OUTPUT SPROCKET.

RON
 
How about an uber simple two speed/two belt "shifter" like a lot of scooters used in the 40's and 50's?

Bolt on a small plate with four pulleys, two belts and a rocker lever to tension/untension the belts.

Low gear/high gear made simple.
 
Bikeguy Joe said:
How about an uber simple two speed/two belt "shifter" like a lot of scooters used in the 40's and 50's?

Bolt on a small plate with four pulleys, two belts and a rocker lever to tension/untension the belts.

Low gear/high gear made simple.
Click to expand...

Sounds simple as long as you have belt drive. Converting my HT to belt drive doesn't sound so simple to me. Any pictures? From a scratch built bike with a four stroke it might be a good way to go. I admit I know little about all this. What I do know is that it would be nice when I came to a hill to shift a lever or something and get to the top without effort. If people keep thinking about it something will work. This is our quest, our 'impossible dream'. Ha! Dreaming is good.
SB
 
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