Climbing and Sprinting technical talk

Rick Youngblood

CarbonCraft Master
The reason I believe an on the fly seat angle adjustment is not practical is, you would then need on the fly boom and handlebar adjustments as well. My experience with adjusting seat angles, be it Cruzbikes and other recumbents I've owned, anytime I change the seat angle, I'm having to adjust the boom due to my hip moving also, which then causes my hip to pedal distance to change. For me 3-4 mms can cause my knee to hurt. Handlebars aren't as critical for me unless it changes the wrist to arm angle, then I also need to make that change too.
 
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MrSteve

Zen MBB Master
The reason I believe an on the fly seat angle adjustment is not practical is, you would then need on the fly boom and handlebar adjustments as well. My experience with adjusting seat angles, be it Cruzbikes and other recumbents I've owned, anytime I change the seat angle, I'm having to adjust the boom due to my hip moving also, which then causes my hip to pedal distance to change. For me 3-4 mms can cause my knee to hurt. Handlebars aren't as critical for me unless it changes the wrist to arm angle, then I also need to make that change too.
Yes, totally true.
True as in, fact of life and/or written in stone.

On my modded Sofrider, the ultra-reclined seat was built about an inch closer to the pedals than the less-reclined seat.
This 'measurement' was arrived at via cut-and- try and exactly meets my personal requirements.
This was done so that when I wanted to swap seats, it could be done quickly and easily without adjusting everything else.
 

JOSEPHWEISSERT

Zen MBB Master
The reason I believe an on the fly seat angle adjustment is not practical is, you would then need on the fly boom and handlebar adjustments as well. My experience with adjusting seat angles, be it Cruzbikes and other recumbents I've owned, anytime I change the seat angle, I'm having to adjust the boom due to my hip moving also, which then causes my hip to pedal distance to change. For me 3-4 mms can cause my knee to hurt. Handlebars aren't as critical for me unless it changes the wrist to arm angle, then I also need to make that change too.
Seems pretty simple compared to what Tony Stark did with his Iron Man suit.
 

murmur

Member
Yes, totally true.
True as in, fact of life and/or written in stone.

On my modded Sofrider, the ultra-reclined seat was built about an inch closer to the pedals than the less-reclined seat.
This 'measurement' was arrived at via cut-and- try and exactly meets my personal requirements.
This was done so that when I wanted to swap seats, it could be done quickly and easily without adjusting everything else.

So... now it does sound like what's needed is an "adjuster" that changes the seat's angle and its fore/aft position simultaneously. If that's enough (i.e. if the change in arm extension isn't enough that it requires a change in the bar position as well) then yeah, it isn't a Stark Industries-level contraption, but it will add weight.
 

MrSteve

Zen MBB Master
Everyone is different, though: different torso/leg length ratio, arm length... on and on and on.
Like me, for example. I'm so incredibly different, with the shorter right leg, weird non-stock knee angles, and stuff.
The brain goes without saying, so don't say it.

The adjustable-on-the-fly seat for everyone is a cool idea, but kind of a pie-in-the-sky idea in the real world.
Unobtainium.

Now, chew on this: ejector seats.
Discuss.
 

PeteClark

Active Member
Another thought exercise on the topic of adding power with one's upper body...
The most efficient way to apply force is in the direction of motion. On a bike, the most efficient way to transfer force from one's leg to the chain is to apply force to the pedal at a right angle to the crank arm, and always in a plane that is parallel to the chainring. However, on a Cruzbike, this would result in pedal-steer. Focusing on the top of the pedal's arc, where the pedaling force is greatest for most people, applying force to the right pedal in a plane parallel to the chainring will push the bottom bracket to the left. To minimize pedal steer, one would need to apply force to the pedal in a plane that passes through headset and the center of the pedal. (Those lucky few who can pedal a Cruzbike no-hands must have learned to do this.)

On my Vendetta, the bottom bracket is about 21 inches in front of the headset, and the center of the pedal is about 4.5 inches outside the center line of the bottom bracket. So at the top of the pedal's arc, the angle between a plane parallel to the chainring and a plane through the headset and the pedal is about 12 degrees. The tangent of 12 degrees is a bit over 2%. If I were able to pedal without any upper-body input, applying force to the pedal in the plane through the headset and the pedal, about 98% of the force applied by my leg would move the pedal in the plane parallel to the chainring, and 2% would be "wasted." If I could push the pedal in the plane parallel to the chainring and use my upper body to perfectly offset the pedal-steer effect, the force applied by my leg would be 2% more effective.
 

murmur

Member
If I were able to pedal without any upper-body input, applying force to the pedal in the plane through the headset and the pedal, about 98% of the force applied by my leg would move the pedal in the plane parallel to the chainring, and 2% would be "wasted."

Only a fraction (and I'm not at all sure what fraction) of that 2% is actually wasted. The force used to push on something in a direction it won't move in doesn't transfer any energy to that thing, although some energy will still be lost in the form of heat (because your muscles generate heat when they produce force, even if they don't perform any work.).
 
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