| ??? 03/12/12 06:31 Read: times |
#186589 - Crank rpm - not back wheel rpm Responding to: ???'s previous message |
Justin Fontes said:
When riding my bike uphill, downhill, and flat; I try to make it where I can continue keeping my breath. So, I like to stay at an average power. Lowering the power output is also a way of keeping my breath.
In all of your cases, torque and angular velocity of the pedal is not changing which means that you expect power to change because you are cycling through the gear train. This will keep a constant linear velocity, but will put the cyclist out of breath quickly because the load may be much larger and power must be increased. Err... No. I expect the rider to change gear, so the rider stays at the same output power. Same torque and angular velocity of the cranks. But different angular velocity of the back wheel. In my case, I expect the rider's linear velocity to vary quite dramatically between flat and uphill. A constant applied power will do just this because of the varying loads. Don't think anyone have claimed anything different. Either way, you have been correct early in your posts, but it seems that we may have a communication problem. For example, a constant RPM in all three cases being the same RPM or different RPMs that are held at a constant rate. I think subscripts would be very helpful in this case. Maybe you assumed I was talking about constant RPM of the back wheel, and missed I talked about same RPM of the cranks? Cadence is the normal term used for the RPM of the cranks in bike lingo. It is, after all, the main goal with having lots of gear on the bike that you want to keep the crank RPM at a quite narrow window to maintain the efficiency of the rider. Different riders have quite different optimum RPM window, but it is normally quite narrow. So road and MTB bikes have lots and lots of gear options. |
