#61
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If you put the pedals at 12 and 6 and load the pedal at 6 you're putting a sideways load on the frame.
Given what Dave said before about frames that are out of alignment being resistant to shimmy it would make sense for weighting one pedal to work.. you're mostly likely twisting the frame slightly out of alignment and changing how it loads/unloads. |
#62
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The center of mass is more-or-less at about your belly button and there is no practical way to get it to be lower on any given bike than it is when sitting in the saddle.
dave |
#63
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So as an aside, can anyone explain how they think this will effect handling?
If I put a scale on the saddle and the pedals... If I'm sitting on the saddle scale it will register the majority of my body weight there, very little at the pedals. If I stand up the weight on the saddle will go to zero and all of my body weight will register at the pedals. One high above the axle axis of the wheels, one below the axle axis of the wheels and more centered. Seriously, shifting the weight has to have an effect. Quote:
William PS: Sorry if this bike belongs to a member, I just pulled it off the inter web. |
#64
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Quote:
There are entire scientific journals (at least one) dedicated to bicycle dynamics. You'd be surprised what is not known! For example, it was long thought that the ability of a rider-less bicycle to stay upright was due to a combination of gyroscopic stability and trail. But recently a bicycle was built that had negative trail and gyroscopic effect cancelled, but that could self-steer and stay upright. In fact, I think this was posted in a Paceline thread. http://www.nature.com/news/the-bicyc...matics-1.20281 |
#65
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Quote:
First, I'm sure most here have experienced the transformation in handling and traction that occurs between the fully seated to fully standing position on the bike when traversing rough terrain. The fact: As others have stated, simply weighting the pedals/unweighting the saddle does nothing to change the center of gravity of the bike/rider composite (other than the slight vertical displacement needed to get your butt off the saddle). The physics of this is well-understood. The intuition: Changing your weight-support location from the saddle to the pedals creates a sophisticated bogie-type suspension system (bogie suspensions are used on trucks, airplane landing gear, and trains). The bicycle becomes a 2-wheeled bogie with the frame as rocker arm and the pivot effected by the bottom bracket/pedal spindle/ankles. The rider is the main load whose arms and legs become the spring and dampening elements of the suspension. Add to that the anticipation the rider uses to preact on obstacles and you have serious technical complexity. So, fully-seated with feet off the pedals results in no suspension effects whereas standing on the pedals with weight off the seat (or railing a corner with your outside foot supporting all your weight) results in a complicated and effective suspension bike/rider system that smooths the ride and maximizes traction. This question is all part of the charm, beauty, simplicity, and mystery that makes riding so compelling. Back to the OP. If nothing seems to alleviate the handling difficulties with that bike, I'd pass it along and get a different one. There are far too many beautiful and well-behaved bikes out there; don't put up with one that you can't trust. |
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