Originally Posted by
iconoclast
I was wondering why recumbents have such a hard time climbing hills.
So, I did a little experiment.
I used a digital scale to compare the force available to the pedals.
When on a DF standing up pedaling, you obviously have your weight + any additional force from extending your leg.
On a recumbent you only have the force from extending your leg.
For me, standing on the scale I got 200 lbs static.
When I extended my leg, I saw the scale jump to approximately 270 lbs.
Then I positioned the scale so I could replicate my recumbent position.
With my back against the wall and the scale securely mounted, the most force I could muster from my leg extension was 160 lbs.
However, I really doubt that I could exert this force continuously while pedaling.
I tried to exert what I thought was my normal uphill leg force.
The scale reading was around 100 lbs.
So, basically what we have is 200 - 270 lbs vs 100 -160 lbs force to the pedals.
That's essentially a 2 to 1 advantage that DF riders have over recumbents.
I'm not a physicist, but I can't get my mind around this analysis. When you saw the scale jump to 270 pounds, (presumably by starting from a squatting position, then suddenly standing up?) you must have noticed that the effect lasted only a second or two. To reproduce it you would first have to squat down again, causing the scale to momentarily move in the other direction. Moving your body up and down in this way would seem to be just a back-and-forth transfer of energy with no net gain.
I think that if the amount of force you can generate by a leg extension is 160 pounds, that's about what you're going to get on any kind of bike. On a DF bike the effective pedaling force is ultimately limited by your weight (since anything greater would lift you into the air rather than pressing the pedal down), but since that's a higher number in your case it's basically irrelevant. On a recumbent the external limitation is the strength of the seat frame you're pushing back against.
At least these are my rambling thoughts. It's an interesting subject, and I've never seen what seemed to me to be a competent analysis of it.
Lee