Because of our rainy and snowy winter I got a bit out of shape. This offered me an unusual chance to relive the process of getting in shape in the spring, like I experienced it years ago, back East. It was the sequence of the human machine that interested me. First the quadriceps get stronger. Then aerobic fitness makes a comeback. These two things happen quickly. The last thing on the list, which takes all summer, is lower back strength. It really is the back, and not "thunder thighs," that gets you up the hills.
The second-to-last machine part is the subtle one. The human body must be harnessed correctly in order to efficiently operate a crank-machine like a bicycle. I can't quite remember, but I think it was the classic book on medieval technology by Lynn Townsend White that emphasized how slow the development of the crank was. A crank mechanism converts rotary motion into linear motion, or vica versa.
You might even remember your grandmother powering her Singer sewing machine with a foot treadle. And she might have remembered her great grandmother using a similar mechanism for spinning. Without a crank, water-wheels would not have been able to use a rotating shaft to run a reciprocating sawmill. Nor would the linear expansion of steam (or gasoline) have been good for anything other than a reciprocating pump. There would have been no Industrial Revolution, steam locomotive, or paddle wheel steamboats.
You might even remember your grandmother powering her Singer sewing machine with a foot treadle. And she might have remembered her great grandmother using a similar mechanism for spinning. Without a crank, water-wheels would not have been able to use a rotating shaft to run a reciprocating sawmill. Nor would the linear expansion of steam (or gasoline) have been good for anything other than a reciprocating pump. There would have been no Industrial Revolution, steam locomotive, or paddle wheel steamboats.
I believe it was White who said that 'there is something about the crank that repels the human mind.' Indeed, show a conventional gasoline engine to a young child, with its clumsy pistons, connecting rods, and crankshaft; and then show the same child a rotary Wankel engine. I'll bet that 99% of the children would prefer the latter, regardless of their demographic background.
The main pieces of crank-based machines were all present in ancient Roman times, but it didn't lead to anything. Even a civilization as ancient and advanced as China didn't have crank-machines until the twentieth century, according to the Wikipedia article. But ever so slowly crank-machines were finally developed in medieval Europe.
The main pieces of crank-based machines were all present in ancient Roman times, but it didn't lead to anything. Even a civilization as ancient and advanced as China didn't have crank-machines until the twentieth century, according to the Wikipedia article. But ever so slowly crank-machines were finally developed in medieval Europe.
One of the weird things about a crank-machine is that no usable force is produced at top or bottom dead center. Hence the flywheel.
This brings us to the problem a cyclist has: his machine is converting linear contraction in his thigh muscles to rotary motion. No matter how strong he is at pushing down on the pedals, his thigh muscles are only used effectively for 60 degrees out of a 360 degree circle. Fortunately for us we have many muscles that are underutilized. It takes cleated bicycle shoes to pull backwards at the bottom of the stroke -- like you're scraping mud off your shoes at the front door. This pulls in large muscles such as the gluteus maximus and the lower back.
It usually takes several weeks before my muscles are scraping mud off the bottom of the feet. I wonder how many people take an unstudied slap at cycling every now and then, and never appreciate how the muscles of the human machine must work as a team in order to have fun and be fast. Imagine how frustrating and unsatisfying swimming would be if you just jumped in and flailed and thrashed like a dumb kid.
It usually takes several weeks before my muscles are scraping mud off the bottom of the feet. I wonder how many people take an unstudied slap at cycling every now and then, and never appreciate how the muscles of the human machine must work as a team in order to have fun and be fast. Imagine how frustrating and unsatisfying swimming would be if you just jumped in and flailed and thrashed like a dumb kid.
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