The Physics of Descending on a Bicycle

When a solo rider or a group of riders descend any hill, particularly a steep hill, why are some of the riders so much faster than others? 

The fastest descenders, whether by experience or instinct or learning, are the ones that sense or know the laws of physics and do everything they can to use them. 

When a rider descends, the motion of the bike is governed by a series of variables: 

--The grade of the hill 

--The total frontal area of the bicycle and rider 

--The air speed of the bike 

--The total mass of the bike and rider 

--Momentum: the combination of ground speed and mass 

--Spoke count of the wheels 

--Rolling resistance 

The grade of the hill is the most important variable. I have descended eight percent grades in the Alps and in the eastern US and never hit 50 mph, even after two or three miles. But I have gone 55 to 59 mph on half-mile hills with 15-20 percent grades. 

 

The frontal area of the bike and rider determines the top speed on any given grade. Wind resistance increases by the square of the speed. Double the speed, quadruple the wind resistance. At 11mph a rider is mostly pedaling to move the mass of bike and rider. To maintain 22mph, the same rider is putting 80% effort into moving air. The riders who descend the fastest, especially above 40mph put their crotch on the top tube and their sternum on the handlebars and pull their elbows and knees in. 

Related to wind resistance is air speed. I worked seventy miles east of my home for many years. I would ride to work once a month between April and September. I would wait for a day with a 20mph west wind and ride that 70 miles in under four hours, under 3.5 hours on the best days. When the wind was exactly behind me there were times it was quiet. I was going 22mph in a 20mph tail wind. My air speed was 2 mph. I was flying. 

I am the wrong size to be a bicycle racer. At nearly six feet and 185 pounds, I am 20 pounds heavier and several inches taller than many top racers. But descending, every pound is to the good, because… 

Mass plus ground speed makes momentum. The higher the speed and the greater the mass, the more force pushes the bike down the hill. When I pull out of the draft and sail past a 160-pound rider, momentum is my friend. 

One variable every rider can control is spoke count. Every revolution of the wheel, from the perspective of the wind, whips the spoke from no speed to twice the speed of the bike and back to zero. Low-spoke-count wheels with thin or bladed spokes reduce the wind resistance and the turbulence of spokes. The faster we ride, the more wind we whip through the spokes in our wheels. 

On a road bike with fully inflated 23 or 25mm tires, rolling resistance is negligible, but not zero. 

In summary, to go really fast downhill, find a steep grade, make yourself as small and narrow as you can, ride low-spoke-count wheels with fully inflated tires and hope the wind is behind you. I love going fast. My Strava KOMs are downhill, not up.

Rural Drivers Hating Bicyclists is Nothing New

In 2004, a bicycle hater with the unlikely name John F. Kennedy threw tacks on the road when he knew bicyclists would run over them and get flats and possibly crash. 

He did it twice. The second time, I saw him do it. I got his license number and harassed the local police until they arrested and charged him. Here’s the story: 

From the mid-1990s until March of this year, I rode two or three times a week with a daily training ride group led by a former National Champion named Scott. Monday through Thursday at 4pm and Friday at 1pm, riders join the group from the west side Lancaster, Pa., and follow an unvarying route of 35 miles by the time the riders return to the city two hours later. 

The ride is so predictable, that I and other riders would join the ride at several different points knowing within two minutes when the riders would pass a given intersection or landmark. The ride goes southwest of Lancaster to Safe Harbor Park near the Susquehanna River, then turns north toward Columbia, and back to Lancaster through Millersville. 

Just before Safe Harbor Park is Conestoga Boulevard, the place where pickup trucks are most likely to pass too close, blow their horns or occasionally yell their displeasure at sharing the road—a nearly empty road. One day in 2004 passing over the crest of a half-mile hill, several riders got flats. 

There were tacks on the road. Recently a man in an old red pickup truck had yelled at us several times as he passed. The ride crests the hill at 4:40pm and that was when he was headed home to the apartment where he lived south of Safe Harbor Park. Apparently, he got ahead of us, threw tacks on the road and drove away. I thought it was him. 

Two weeks later he passed us yelling as we neared the top of the hill. I sprinted as hard as I could down the hill wanting to see where he went at the next intersection. As I neared the bottom of the hill, I saw him on the side of the road throwing tacks. He saw me, got in his truck and took off. I got his license number. It was a level road and he was speeding so he was gone in moments, but I did see that he went south. 

Two other riders had followed me and seen what happened. Now we had witnesses and actual tacks. I called the Conestoga Police Department and got little cooperation, but I insisted, and they relented. John F. Kennedy was charged two misdemeanors. I told the officers that I had witnesses and we would all be happy to testify. 

On the day of the trial, Kennedy arrived in the pickup truck I had identified. We learned later he had another vehicle. It turns out he did not have an attorney. Criminals, when you get to know them, are stupid. Those of us who were witnesses showed up at trial in suits and ties. 

Kennedy wore work clothes and had his sunglasses on top of his head. If he had a lawyer, the lawyer would have known that the judge had a son who was a Lancaster City police officer, a member of the bicycle patrol. The lawyer also would have known that one of the witnesses was a bicycle patrol officer and a veteran. But Kennedy was too arrogant to think he needed a lawyer. 

The judge presented the evidence. The witnesses said what they saw. Kennedy spoke in his own defense saying he did not throw the tacks on the road, but bicyclists should not be blocking the roads and we deserved what happened. After the testimony, the judge gave a summary of the evidence and the defense. He was so calm and impassive, I thought Kennedy would get the case dismissed. The police officer who rides with us and was a witness knew better but said nothing. 

When the summary was complete, the judge told Kennedy to stand to receive the verdict. He stood and smirked, also thinking he would get off. The judge exploded. Kennedy stood straight. All of us sat up straight. The judge lectured Kennedy for ten minutes, gave him the maximum fine of $880 dollars and said he would be in jail if every penny was not paid on time. 

Four of my kids were at the trial. They all rode bicycles and they knew all of the riders who were endangered by Kennedy. Like us riders, they sat very straight and still when the judge charged Kennedy. I was glad they could see justice served. 

Kennedy never bothered us again. I never saw him again.

Saved from a Blizzard by a Roach Clip

Stewie's roach clip had a smaller white feather

One of my favorite people on Hill Air Force Base, Utah, was Airman Stewart “Stewie” Caldwell. We both went through Basic Training at Lackland Air Force Base, went to tech school at Lowry AFB and were assigned to Hill. Stewie was a year older and had been at Hill for more than a year when I showed in October 1972. 

Stewie was in the Air Force because he had a low draft number and did not want to get drafted into the Army. He was from California and from his as-long-as-regulations-allowed hair to his tan to the sandals he wore when he was out of uniform, he was a laid-back Californian. 

He smoked weed when he could and became even more laid back than usual when he was high. Stewie had a yellow Volkswagen Beetle, the bright yellow color available that year. He kept a roach clip with a feather on in the glove box when he was on base. When he was away from the base, he would hang it from the mirror. 

On sunny day in March of 1973, Stewie decided he wanted to go to Salt Lake City. We went in his car. I don’t remember where we went in the city, but I remember seeing the clouds in the west shortly after we arrived and saying we better get back to the base. Western storms can go from clouds to sideways blizzard in minutes. 

We left Salt Lake City in falling snow. Ten miles north on I-15 we were in a sideways blizzard. The temperature had dropped below freezing. Stewie was driving looking through the triangular vision slit which was as much as VW windshield wipers would clear. We were rolling in the accumulating snow. I was wiping the windshield every couple of minutes because Beetle defrosters never worked. The skinny VW tires and rear engine kept us rolling when bigger cars were already getting stuck. 

Then Stewie yelled, “Fuck. It fell apart. Fuck!” The gas pedal and its mounting bracket were under Stewie’s heel. The pedal had come off its mounting and also from the cable that connected the pedal to the carburetors. I had owned a half dozen cars by this time and had fixed them with odd parts when needed. I slid under my side of the dash, reached for the cable and pulled. I revved the engine, then lost grip. 

There was a fitting on the end of the cable. I said, “Stewie, give me the roach clip.” It worked! I pulled the cable and got the roach clip behind the crimp fitting on the end of the cable. I could pull the cable and hold it. And I had the flexibility of a 19-year-old, so I could be under the right-side dashboard and work the gas with my left hand. Stewie had to wipe the windshield himself.

Stewie put the car in second gear and while I held the gas, he slowly released the clutch and got us going. When he stepped on the clutch, I released the cable and pulled it up again. The snow was really deep by the time we got to the gate at the base. Stewie opened his window and held out his ID. Luckily, we got waved through. The guard did not want to come out of the gatehouse, and we didn’t want to stop. We made it back to the snow-covered parking lot and stopped in a snow drift that seemed to be close to a parking space. 

Not our fate, thanks to the roach clip

Stewie told the story of the roach clip that saved our lives for months afterward. He was particularly dramatic when he said, "The feather got crushed. Dude, I loved that feather." 

A Book Justifying Support for Trump by White Evangelicals

 

I am reading a book by a white Evangelical Christian justifying his support of the "chaos candidate." I am reading it with two friends who are Christians who live in German and are trying to understand the trumpian Church in America.

The author quotes Christian leaders who celebrate him as a "Chaos Candidate." These trumpians see the white Evangelical Church as embattled by dark forces of secularism who want to take away their freedom.

Imagine those who say they worship the Creator of the Universe celebrating chaos! Chapter 6 has extensive quotes of those celebrating the chaos candidate.

It reads like a librarian celebrating book burning.

The book is a strong confirmation in Church language that the trumpians in the Church, like all trumpians, love their orange idol because he hates who they hate.

Another chilling bit of clarity in the book is that in his reptilian instinct for power, trump has found a huge loyal group who really, deeply celebrates his authoritarian goals. The religious people who support him want rights reversed for everyone who is not them.

MAGA re-elected will reverse gay rights, abortion rights, women's rights, voting rights, the rights of the disabled, worker's rights and when the steamroller gets some momentum going, Bill Barr will reverse civil rights.

Evangelicals at the Crossroads: Will We Pass the Trump Test?

Fortune's Wheel and the Place of Peace

 

In “The Consolation of Philosophy” Boethius pictures fortune as a wheel. The world, like a wheel in motion, is always putting stress on those who are in the world. But the stress is far from equal. There are times of relative calm, when the wheel moves slowly. And there are times of trouble, like war and pandemic and tyranny, when the wheel speeds up. 

Those near the edge of the wheel, even in relatively calm times, have large forces acting on them. They are never at peace. They live inside their circumstances, often they believe that Fate is all they have. In hopeless circumstances such as terminal illness or being a refugee, they may be right. They may also make the perception that Fate is all they have into a self-fulfilling prophecy. 

Boethius says those who pursue philosophy move closer and closer to the hub of the wheel of this world. Those who are at the hub of the wheel, no matter how fast the wheel spins, are at rest. When we rest at the hub of the wheel through philosophy we can be at peace in a world with political strife and wars and storms and fire and flood. Elie Wiesel showed this in Auschwitz. 

We could, of course, be caught in any sort of disaster by chance and circumstance, but through seeking the good and the true and the beautiful, we can stay at the hub of the wheel of this world through anything. Since we live in this world, and cannot totally leave our responsibilities to others, we have to grab one of the spokes of the wheel of this world--family troubles, work problems, the pandemic—and we have to grip tight against the centripetal forces shoving us out of the refuge of philosophy. 

But when the crisis is resolved, we can turn back toward the peace at the hub of the wheel. In my case, daily meditation or riding up a hill I've ridden up 50 times before can bring my mind to the hub of the wheel, at rest even while my life is in motion.

Peaceful Transfer of Power and Change of Command

Most of my recent military service was during the Obama administration. I re-enlisted in August 2007, deployed to Iraq for a year in January 2009 and then left the Army National Guard in May 2016.  

During those 11 years I witnessed dozens and dozens of change of Command ceremonies.  From command of a company to a full division, the passing of the unit colors from the old commander to the new commander is very much the same ceremony. Whether in front of two dozen soldiers or ten thousand soldiers the officer holding power gives that power and privilege and responsibility to the next commander.

At many of these ceremonies, the new commander in the first address to the unit will talk about the peaceful transfer of power. How this peaceful transfer of power is a true American tradition dating back to President George Washington and continuing right up through the moment of the ceremony.  

Nearly all of the commanders I served with, as well as most of the soldiers, were Republicans or conservative independents.  They were proud of upholding this American tradition and looking forward to the peaceful transfer of power to a conservative President.  

But these same soldiers I served with are now will continue their support for the current President even though he will not commit to the peaceful transfer of power.  

In 1993, Vietnam War veterans made a great show saying they would not back President Clinton as a matter of honor, then honor melted like snow in the Sahara when they had their own despicable draft dodger.  In the same way the words about the peaceful transfer of power will melt faster than the polar ice cap when their Dear Leader refuses to leave office.

The military reports to the Commander-in-Chief.  When the C-in-C breaks the law, they will follow. 

Unhappy Guy Pushing His Bike

 

I was standing on my front porch just a moment ago. It's a beautiful day. A man was walking by my house pushing a bicycle.

He stopped and said, "Did you live here when the Sharks were here?"

My mind goes to literal in a millisecond. I looked at the empty parking lot that used to be for an out-of-business lumber yard and looked puzzled, not thinking sea creatures were part of the Lancaster cityscape. I said, "We just moved here."

He said, "The Sharks used have a block party. Closed both of these streets. Beer, hakey sack, girls in bikinis." The Sharks were on MTV, but they never quite made it big."

If he was playing hakey sack, they must have been on MTV in the 80s. The bike pusher is about 75 years old. He was wearing coveralls with a plaid shirt and a big hat with a circular brim. He had a thick white beard. He was wearing a medical mask upside down tight against his face.

"You can't have any fun anymore," he said. "Even before the COVID. Too many rules. I feel sorry for college kids now."

He strode off.