Sliding Seats

I decided I wanted sliding seats. Well, any kind of arrangement that would let me change the rider height quickly and easily. The usual arrangement I've seen in Australia has a sliding extension on the front boom, so you move the bottom bracket away from the seat. This means changing the chain length, which is a pain. Michael Rogan ( MR Components) has a cunning device on one of his demo trikes that lets him do this easily, but it sucks power. Basically he has two extra idlers, on of which slides backwards and forwards.

The idler that moves has a quick release bolt on it and slides in an aluminum channel. So it really is quick to move. Too bad about the power loss.

The obvious option is some kind of sliding rail, as used in cars. Not too hard on a trike, just weld a couple of bits of angle iron onto the frame and clamp to that.

This would be fairly simple, easy to build and resist torsion quite well I think. However, I think I'd need quite a lot of angle iron - twice the slide length per seat plus the length of the clamps. Of 3mm thick 30mm angle iron, which is cheap but weighs a lot.

Another option is to use another tube clamp. Just get another length of whatever oversize tube I use to join the frame, and weld the seat to it. The disadvantage is that it's not going to be trivial to shift as there will be a collection of bolts under the main tube.

One slightly odd idea is to use pivoting rods to hold the seat, and a clamp somewhere to lock it. This lifts the shorter rider up as well as forward, and means there is not a lot of sliding going on, so the paint should stay put. Like so:

I'd need to clamp the swinging arm, or possible have a sliding tube extending back to lock it. The advantages of this are that it's light and quick to adjust. Also no-one seems to have done it before. Maybe that's a disadvantage... but it could also end up being flimsy and it would be tricky to undo, because I'd need to put the pivot bolts through the frame tube.

Another seating issue was whether to make them adjustable or fixed. Fixed is simpler, but if I can recline them I can play with seat angles fairly easily. However that will be complicated to do well, since as the seat back reclines the bottom section also has to move, but not as much. So I'd need two (or three) piece seats. That's way too complex for me.