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Discussion Starter · #1 ·
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:
http://www.youtube.com/watch?v=IdrbabekQ5k

A few pics are attached.
 

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Still using dork disk.
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Doesn't look half bad. I like the DIY spirit! Please keep us updated on what you think after a ride.

Ryan
 

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Brilliant! said in my best british accent!

only isue i view is rattle. mabe wrap it at the bottom and the middle in the frame section with a little packing foam sheet. its lite, chep or free, and would help stop side to side movement, if there is any.

ill be trying this!
 

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Village Dirtbag
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Very creative- good idea. Does it rattle? What does it weigh?

That said, would a hite-rite be a superior solution? Lighter, simpler, more durable and reliable, and keeps the seat pointed the right direction. If only someone could think up an effective remote QR, dropper posts would've never caught on.

 

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Discussion Starter · #7 ·
the-one1 said:
Cool idea. Only flaw I see is if you have a nice seat post, it will get scratched up.
Seat post shouldn't get scratched up. Possibly a little on the inside of the seat post, but not on the part you see. Using the gas strut essentially mimicks the same action as lowering and raising the seat height yourself. So if your seatpost does get scratched, it won't be any more than normal.
 

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Discussion Starter · #8 ·
@dam said:
Very creative- good idea. Does it rattle? What does it weigh?

That said, would a hite-rite be a superior solution? Lighter, simpler, more durable and reliable, and keeps the seat pointed the right direction. If only someone could think up an effective remote QR, dropper posts would've never caught on.
Ya, keeping the seat automatically aligned which changing height is the next step. I need to do some research to see if anyone makes a gas strut that doesn't allow the shaft to spin inside the canister. Then I could attach the strut to the inside of the seat post and the inside of the seat tube and the seat would stay aligned. A "two-bar" linkage might work. Basically do what the external spring in the picture does but without the spring function, that may keep the seat aligned.

I like the old external spring idea, very simple. However the one in the picture only looks to provide about 3" of drop height, my ideal is 6" of drop, others may be 5" or 4." You can just buy whatever gas strut stoke matches whatever amount of drop you want.

A clever remote release would be a gem, but that's probably the hardest part to do well, I'll keep tinkering and see if I can come up with anything.
 

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Discussion Starter · #11 ·
That IRD remote clamp would be perfect if you only you could find one. You'd still use your existing QR clamp, but remove the shaft/nut/lever mechanism and install this IRD clamp instead. It would look kinda hokey, especially if you replace the external coil spring with a two-bar link, but it should work. Again, the biggest challenge is getting your hands on one.
 

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DirtyMartini said:
That IRD remote clamp would be perfect if you only you could find one. You'd still use your existing QR clamp, but remove the shaft/nut/lever mechanism and install this IRD clamp instead. It would look kinda hokey, especially if you replace the external coil spring with a two-bar link, but it should work. Again, the biggest challenge is getting your hands on one.
I have the IRD remote. Not enough throw for use with separate collars. Would love to make a modern collar/remote QR/spring unit.
 

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I think it would be much better and economic to design a combo remote qr and spring for a normal seatpost than the fancy over priced over engineered dropper seat post we see today. yo could simply put a thin ti coil spring around the seatpost. it would keep it aligned and have up and down set up heights and a remote qr and that would be it! but too cheap to make 200 or 300 $ out of it so it is not interesting for rs or crank brothers
 
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