Dropper seat posts

[Sterba]

I put a disabled person on the back of a tandem. He has trouble getting over the saddle, so it has to be set too low for him to get enough leverage on the pedals. I was thinking about fitting a telescoping seat tube with a lever (I think the frame size is 27.2mm, or it may be slightly less). But I need it to be able to LIFT the seat with the person on it, as well as drop it. Do these devices crank up as well as down? I say crank, because Crank Bros make one, but they would have to have a powerful spring or hydraulic mechanism to to do that, as he weighs more than 60 kgs.

Advice please

 

[marzjennings]

None of the ones I've seen and used (Crank Bros) have enough spring or pressure to lift both the saddle and the person. Generally you unweight the saddle, stand on the pedals, when you want it to return to full extension.

 

[Sterba]

Yes, that's what I feared. I suppose it's why they are called droppers, not risers! The person can't stand on the pedals while the saddle goes up. Back to the drawing board. Thanks.

 

[PaulSB]

My son has this problem, is also disabled and weighs 62kg. The solution we use is this. My son is very short and it might not work for a tall individual

Position the bike by the kerb which has the effect of lowering the bike. Lead rider, captain?, gets on first, clips in right foot and raises it to the top ready to push away. then lean the bike into the kerb taking the strain on left, standing foot.

My son can then step across the frame and get on the seat. He gets his feet in the rat-traps. I level up the bike and push away hard.

We've never had a problem with this technique though it doesn't work well on hills but I try to avoid those anyway!!!

 

[sidevalve]

I assume you're using a "ladyback" tandem ? If not it may be worth experimenting with [hire one for a day] one to see if it was possible to step through the frame then lift himself onto the saddle via the pedals while you hold everything steady.

 

[Sterba]

We have to resort to an unconventional approach. I have to get my stoker on first, fix him into one of the pedals and attach him to one side of the bars, and then get on myself. It can only be done by leaning the bike up against a wall. This works better than it sounds. But the fundamental problem is that the seat height he can get to is too low for proper leverage once we are going. I need to be able to raise the seat once on board and lower it before he gets off. Standing on the pedals is not an option.

Thanks both for your thoughtful ideas, any discussion of this is valuable for me.

 

[Howard]

Inspiring reading.

With a 27.2 seat tube your options for a dropper post would be limited. But if you can get one, could your stoker be taught to use a remote leaver to raise the saddle whilst taking their weight off the post? I have a crank bros Joplin on my MTB and I weigh about 60kg - I don't need to completely un-weight myself from the saddle - a transfer of 60pc of my weight is enough to get the pressure in the post to do the rest.

 

[sidevalve]

As an idea try to contact a local model engineer group. They can have some amazingly skilled members and the challenge of installing a hydraulic or poss gas ram in the seat tube [allowing the saddle to be "pumped" up] may be well within their capabilities. After all once in place locking it is not really a problem [just clamp like a normal saddle]. If this fails a small engineering shop may be able to help and the work involved may not be that great.

 

[boybiker]

As an idea try to contact a local model engineer group. They can have some amazingly skilled members and the challenge of installing a hydraulic or poss gas ram in the seat tube [allowing the saddle to be "pumped" up] may be well within their capabilities. After all once in place locking it is not really a problem [just clamp like a normal saddle]. If this fails a small engineering shop may be able to help and the work involved may not be that great.

You basically want a bottle jack to lift and lower the seat. It's highly feasible one could be fabricated, car bottle jacks are big yes but they lift 2 tons+ one to lift a person could be smaller. It's a long shot but possible IMO.

 

[Sterba]

Thanks all, I'm not sure if he could stand on the pedal. It may be a few weeks before we get to try.