I'm not sure what you mean by variable seat recline. I'm planning on making the seat adjustable within a reasonable range (approx 30 +/-5 deg abovr horiz for the hip-shoulder section of the seat, upcurved top to limit neck/upper shoulder strain) using a similar system to a t-bone. My current drawing puts the BB center at about the same level as my hip joint when seated (a few inches above the seat base).
Speed at all costs is not my primary goal but the thing needs to be fairly fast and also climb reasonably well. This is more fast tourer than racer. My primary design consideration is to optimize this bike for my commute. It need to handle traffic adequately when needed. It needs to be fast on the flats and it needs to climb reasonably well. My morning commute consists of a long gradual downhill which I usually maintain about 25-30 on on the road bike. followed by a streatch through town which is all stop and go. Then a ~10 mile streatch of flat to rolling hills which I maintain about 20 on the road bike, then a 3 mile climb (2 - 10%) , a 2 mile downhill and a 1/2 mile climb (4 - 15%). Avg speed on the computer is usually a hair over 16mph avg. at the end. If I can match that rolling avg on the bent with a bit of practice, I'll be happy. I'd rather gain a bit of speed on the flats in exchange for a little climbing ability since the flat roads are heavily travelled and the faster I am, the safer I am.
I'm not sure what you mean by variable seat recline. I'm planning on making the seat adjustable within a reasonable range (approx 30 +/-5 deg abovr horiz for the hip-shoulder section of the seat, upcurved top to limit neck/upper shoulder strain) using a similar system to a t-bone. My current drawing puts the BB center at about the same level as my hip joint when seated (a few inches above the seat base)....
By variable seat recline I mean a seat where the angle of the seat back can be changed while riding. This is complicated by needing to have the seat base move forward to keep the rider's leg extension constant while pedaling. The Forte lowracer I posted a link too is one example of such a bike. [1] The variable seat recline allows for an upright seat back for more sprinting and climbing power, and a reclined seat back angle for minimizing frontal area on flat and downhill sections.
Further testing is needed, but variable seat recline could potentially improve overall climbing ability of recumbent bicycles by allowing changes in position. [2]
[1] The only other I am aware of is the one ridden (and built?) by John "Rocketman" Williams which reportedly has a seat recline angle adjustment from 10 to 40 degrees from the horizontal. [3] [2] Studies have shown the fastest way to climb longer grades on an upright bicycle is to alternate between sitting and standing. [3] By convention, recumbent seat back angles are measured from the horizontal. -- Tom Sherman - Fox River Valley "Abnormal would be a mountain lion speaking English." - M.V.
ah, the variable seat position is a very neat idea. A bit out of the scope for this project but maybe someday.... hmmm. I can envision a 3 part seat so that the base, back, and shoulder sections move relative to one another so that each position is comfortable and effective.
