I posted this in the Iron Horse forum, but figured it might be of interest to others as well, but the idea is still half-baked.
You've heard of "ghetto tubeless"? I'm calling this "ghetto adjustable seat post."
You've probably seen the old school guys adjusting their seat height manually on the fly: undo quick release, grab seat with inner legs, pull seat up, reclamp QR, etc.
I could never get the hang of it so I started thinking about how to make the seat go up and down on it's own. What I came up with is the use a gas stut (aka "gas spring").
These are the little struts commonly used on hatchbacks and windows on cars. They're light, cheap, small, reliable, and come in a wide range of lengths, forces, strokes etc.
I measured the "stroke" on my seat post (difference between full up and full down) and bought a gas strut with that length stroke at Napa Auto Parts for $30. You want the longest "eye to eye" length you can get without it being so long that when strut is at the bottom of your seat tube it doesn't hold your seat post up higher than you want. It's unlikely you'll find exactly the right length, so error on the side of shorter and then just rig a spacer (pvc or even stuff some old tube rubber) down inside the seatpost to get the right height. The strut will run down inside your seat tube, and up inside your seat post approx 4" below the seat. Oh ya, you'll want either the 20lb force version or the 40lb force version of the strut. (you can buy from 20lbs to 140lb, this is the force required to compress the strut).
Stand up when you unclamp your QR, the seat rises, sit on it and it does down. You just have to learn to clamp and unclamp the QR on the fly, which isn't that hard if you have a good quality QR (like Salsa). I may post some better pics is people are interested. I've only tried it out on the street, but it seemed to work well.
Here a little clip of it working:
A few pics are attached.
You've heard of "ghetto tubeless"? I'm calling this "ghetto adjustable seat post."
You've probably seen the old school guys adjusting their seat height manually on the fly: undo quick release, grab seat with inner legs, pull seat up, reclamp QR, etc.
I could never get the hang of it so I started thinking about how to make the seat go up and down on it's own. What I came up with is the use a gas stut (aka "gas spring").
These are the little struts commonly used on hatchbacks and windows on cars. They're light, cheap, small, reliable, and come in a wide range of lengths, forces, strokes etc.
I measured the "stroke" on my seat post (difference between full up and full down) and bought a gas strut with that length stroke at Napa Auto Parts for $30. You want the longest "eye to eye" length you can get without it being so long that when strut is at the bottom of your seat tube it doesn't hold your seat post up higher than you want. It's unlikely you'll find exactly the right length, so error on the side of shorter and then just rig a spacer (pvc or even stuff some old tube rubber) down inside the seatpost to get the right height. The strut will run down inside your seat tube, and up inside your seat post approx 4" below the seat. Oh ya, you'll want either the 20lb force version or the 40lb force version of the strut. (you can buy from 20lbs to 140lb, this is the force required to compress the strut).
Stand up when you unclamp your QR, the seat rises, sit on it and it does down. You just have to learn to clamp and unclamp the QR on the fly, which isn't that hard if you have a good quality QR (like Salsa). I may post some better pics is people are interested. I've only tried it out on the street, but it seemed to work well.
Here a little clip of it working:
A few pics are attached.