Recumbent laboratory test bed

My early experience road testing my first prototype demonstrates a number of things.  Pedaling in a recumbent position is not at all the same as pedaling on an upright bike; it seems to use different muscles.  I'm also aware that my prototype doesn't seem to climb very well.  I put aside my tools and arc welder for a while to devote some time to research on the internet.  A couple of themes rapidly become apparent as important and contentious issues; body position and chain line management are two of them.

Body position for a recumbent rider is generally defined by two parameters; seat back angle, and the difference between seat and bottom bracket height.  However, one or two more astute internet contributors (in my opinion) consider that a more significant parameter is the "body-hip angle", or the angle that the torso makes with the upper thigh when pedaling.  It is noticeable that the body angle is considerably more "closed" (i.e. smaller body-hip angle) on an upright bike than on a recumbent.  Could this be a clue as to why my bike doesn't climb well?  (I also discover that I am not alone; apart from a few contenders, most recumbent riders accept that they do not climb as rapidly as upright bikes.)

Chain line management is all to do with solving the practical problems of guiding the chain so that it doesn't interfere with the front wheel or the seat.  This generally involves (at least for low seated bikes) guiding the chain over the front wheel and under the seat.  This is usually achieved by the use of idlers (pulleys or cogs), but the addition of any intermediate idler between the cranks and the rear wheel - as well as any deviation of the chain from a straight line - is a potential source of efficiency loss.  Much debate seems to accompany this subject, with various views on how significant this efficiency loss may be.

I decide that both these issues merit serious scientific study, and that a "laboratory environment" is most suited to do this.  I set out to construct a "laboratory efficiency test bed".

Here, then, in all its splendid glory is the Fitzhugh recumbent laboratory test bed. The seat inclination can be varied to give a more closed or open body-hip angle, and the intermediate idler can be repositioned to give more or less chain deviation in the drive chain line that passes under the seat.  Pedaling resistance is provided by my hydraulically damped home trainer.

My optimism for the advancement of objective scientific study and analysis of the variables that govern recumbent pedaling efficiency and performance is rapidly diminished by the realisation that I am missing any means to measure key factors such as power input by the rider or resistance overcome at the rear wheel.  This technical deficiency renders any analysis of changing the parameters of my laboratory test bed no more than a subjective impression.  For objective measures I would require at least a power meter at the rear wheel and, preferably, a second on the crankset to be able to study the power in/power out ratios.

I briefly consider adding a dynamo to the home trainer with an electronic multi-meter to measure power output as a means of giving some objective value to the power at the rear wheel.  However, I recognise that the resistance of the home trainer is non-linear so the speed of the rear wheel - and hence power output of the dynamo - will not be easily or reliably related to the true power developed to overcome the home trainer resistance.

I reluctantly admit that these pose serious problems to the objective value of my laboratory test bed.  I finally accept that it should perhaps best R.I.P. and I shall have to be content with using laborious and less reliable road tests to investigate the performance of different configurations of critical variables.  Oh well....