Slow Ride, Take It Easy
Yes it’s been Slow but not Easy, see this Foghat music video.
On Thursday I made two rides, one an ad hoc trip with GCC Team Captain Mike McIntyre beginning at his workplace, Academy One in Malvern. A shorty by his standards, 13.8 miles on the Chester Valley Trail. This is the last day of the GCC September Challenge, so while there was plenty of daylight left I drove over to the Norristown Transportation Center and continued on the Schukyll River Trail up to Valley Forge, another 13.5 miles for a total of 27.2 miles that day.
Yesterday I made a “short” 9.9 mile ride on the Valley Forge National Park system of trails. It took me 1 hr 15 minutes for an abysmal 7.9 mph average speed, whereas my usual is up around 11 or 12 mph on the Chester Valley and Schukyll River Trails, which are relatively straight and flat. At Valley Forge, the trails are neither straight nor flat. Here’s a pic of the route:
I am now up to 145 miles and $125 raised for the cause. This is well short of my $500 goal. You can still contribute at https://greatcyclechallenge.com/Riders/RexSaffer. I have gotten a new App for my phone called Strava that uses GPS to record my rides. You can see some of them now at https://www.strava.com/athletes/93056483.
My UBER COOL jersey arrived!!!
How deluded we can be. I tried it on in front of the dresser mirror, and I feel like a beachball–shaped sausage mercilessly squeezed into one of those slimy cases. The XXL I ordered is a skitch too small, or more accurately, I am a skitch too big. Mike said I’m just too sensitive about the look and that it will loosen up some with time. Hopefully, if I can just break this boom or bust cycle (pun not intended, honest) with baked goods and chocolate, all these miles and Calories burned will translate into weight loss, and I will look marginally cooler if not Uber Cool. But that day is not today…
If that’s not incentive to peel off some pounds, there never will be.
But my cross section is actually of interest, from a Physics of Cycling perspective. In my previous post, I waxed effusively on the energetics of Cycling. In summary, I want to apply the maximum torque at which I do not go hypercardio at my comfort zone pedal turnover rate to deliver optimal power to the bike, getting the most bang for my Cycling buck. Now, this is the applied power in the direction of motion. But there is a drag force in the opposite direction due to air resistance. For an object moving in a resistive fluid this force is given by, and excuse the mathematics, it will only hurt for a moment,
where ρ is the fluid density, here air; A is the object’s cross–sectional area; C_D is the drag coefficient, strongly dependent on the cyclist’s riding position and streamlining; and v is the velocity. I ride a hybrid bike, so my position is more upright than Mike’s, and I have a slightly larger drag coefficient, but not much more. So the main variable is the cross–section, and while mine is more like a beach ball above the bicycle seat, Mike’s is more like an oversized mango stood on end. Still, these do not differ by much either. So does anything actually matter? Oh yes.
The acceleration produced by a force is given by Newton’s Second Law of Motion, where the acceleration is the force divided by the mass. Oh Ho! Here is where I really excel. I outweigh Mike, at least for now, by maybe 30%. So the amount of power I have to apply to the bike is, at least for now, 30% less than Mike has to apply to maintain the same velocity. So why do I find it so hard to keep up with him? He’s just in much better shape than I am and doesn’t get as winded for the same level of exertion. So it seems there are several factors at work here: 1) As I get in better shape and lose some weight, DOG willing, I will be able to propel my bike at a higher torque level without getting so winded, and 2) my cross–sectional area will decrease, causing the drag force to decrease. On the other hand, 3) my mass will also decrease and that will increase the (backwards) acceleration due to drag.
Now mass increases or decreases like the cube of a length or dimension, but area only increases or decreases as the square of that length. So independent of the improvement in my physical condition, the resistive drag acceleration will increase linearly with a decrease in mass, but my cross–section will only decrease as the square root of the decrease in the mass, reducing the drag acceleration proportionally, that is, I cannot win that race on mass loss alone. So it seems counterproductive to lose weight given those considerations, at least from a purely physical perspective. Of course, the health benefits of significant weight loss are difficult to quantify, but surely they are much, MUCH more important than any other consideration.
Mike took some pictures and made a video on our last outing, so if he will get up off his you know what and send them to me, I’ll post them in my next post. I do so hate verbing nouns, as I have said repeatedly, but escaping them would not really be an escape, if you catch my drift. Oh No! Do you experience drift by drifting?? I am in lexical Hell. But I’m off to play Bridge, so there’s that.
All the best,
From Broomall, PA on Saturday, 10/02 at 1:45 PM
Rex
