https://www.cnn.com/2018/09/19/health/woman-rides-bike-183-mph-trnd/
This is with a big windshield in front. Denise Mueller-Korenek.
They must have had a very high gear to wheel ratio!
This begs the question, suppose you were on the moon, with of course space suit and such, with no atmosphere at all, how fast could a human go on a bicycle there? Assuming they had a nice paved course up there....
@sonhouse saidThe limit factors are not air drag of course, but internal friction in the bike itself and the friction between tires and ground.
https://www.cnn.com/2018/09/19/health/woman-rides-bike-183-mph-trnd/
This is with a big windshield in front. Denise Mueller-Korenek.
They must have had a very high gear to wheel ratio!
This begs the question, suppose you were on the moon, with of course space suit and such, with no atmosphere at all, how fast could a human go on a bicycle there? Assuming they had a nice paved course up there....
What about friction of the space suit? Not so much in my opinion. It has to do with ration between gear to wheel. Let's say that you pedal at a steady state, and let the bike transform this force to accelleration. I think you can gain quite high speeds.
- Joined
- 10 Dec 06
- Moves
- 8528
Probably not much faster than what was accomplished here. She effectively negated drag (the predominant force opposing her at those speeds) by riding in a pocket of air traveling with the vehicle ahead of her( very low relative velocity between rider and fluid ). On the moon she could do it without the vehicle, but bearing friction will be present in both cases in similar portions. It basically becomes a question rider of physiology. It becomes increasingly more difficult ( more energy per unit speed change) to change your speed at higher speeds. How much power can they supply and over what duration before they fatigue, overheat, etc...
@joe-shmo saidOf course lunar gravity at 1/6 here would effect all the friction numbers. As would dirt getting into the bearings unless they can hermetically sealed.
Probably not much faster than what was accomplished here. She effectively negated drag (the predominant force opposing her at those speeds) by riding in a pocket of air traveling with the vehicle ahead of her( very low relative velocity between rider and fluid ). On the moon she could do it without the vehicle, but bearing friction will be present in both cases in similar ...[text shortened]... speeds. How much power can they supply and over what duration before they fatigue, overheat, etc...
- Joined
- 10 Dec 06
- Moves
- 8528
@sonhouse saidI was thinking the weight of a 300+ pound climate controlled space suit would counteract a good portion of lost weight, keeping frictional forces comparable between the two scenarios. Also, sealed bearings are quite common. Am I overlooking something that prevents them from working in the vacuum of space?
Of course lunar gravity at 1/6 here would effect all the friction numbers. As would dirt getting into the bearings unless they can hermetically sealed.
@sonhouse saidWas the woman trying to get away from Harvey Weinstein?
https://www.cnn.com/2018/09/19/health/woman-rides-bike-183-mph-trnd/
This is with a big windshield in front. Denise Mueller-Korenek.
They must have had a very high gear to wheel ratio!
This begs the question, suppose you were on the moon, with of course space suit and such, with no atmosphere at all, how fast could a human go on a bicycle there? Assuming they had a nice paved course up there....
Ba-dom-bom.
😀
@joe-shmo saidNot sure the weight but whatever it is the total would be 1/6 that of Earth. So suppose the rider weighs 180 pounds, 30 pounds on the moon and 50 pounds worth of space suit (it may be less, not sure) anyway, going with those numbers the total would be the average weight of a ten year old child with an adult body and the bike may weigh say 24 pounds (again probably too high) so that would add another 4 pounds and we are up to a grand total of 84 pounds of weight (gravitational attraction to the ground) on the moon. If on Earth, 500+ pounds.
I was thinking the weight of a 300+ pound climate controlled space suit would counteract a good portion of lost weight, keeping frictional forces comparable between the two scenarios. Also, sealed bearings are quite common. Am I overlooking something that prevents them from working in the vacuum of space?
- Joined
- 10 Dec 06
- Moves
- 8528
So 90 (on the moon with all the gear) to 180 on earth is about half. As far as radial bearing load capacity is concerned, both loadings are very small. There should be a drop in rolling resistance on the moon, but I don't see much of anything else.
I think the limiting factor would be human physiology. Lets say a human on the moon with all the gear has a mass of 200 kg. To go to 200 mph ( ≈90 meters/sec) from 90 mph ( ≈40 meters/sec) she would have to input at a absolute minimum about 650,000 Joules. ( see calc. below for details)
1/2*(200 kg)*(90^2 - 40^2)m^2/s^2 ≈ 650,000 Joules
I'm reading that the best cyclists can sustain about 250 W for extended periods of time. Meaning she would have to apply that power for 1800 sec. or half an hour to reach 200 mph.
So I watched the video and the whole thing start to finish is 3 minutes.
https://www.autoblog.com/2018/09/21/bicycle-speed-record-bonneville-dragster-video/
This leads me to believe there is some effect where she is literally being pulled along by the draft of the dragster. In order for her to go from 90 mph to 156 mph ( as the video suggest) under entirely her own power she needed to input a bare minimum of 97500 J. That's is completely neglecting friction. From the time of the tow release ( 1:30) to the end of the run ( 3:00) is a duration of 90 s. That means she applied an average 1.5 Hp over the duration of the unleased run. According to most information I see, the strongest male athletes can supply 1 Hp for mere seconds. I conclude there is something helping her along that is not "seen".
@joe-shmo saidSounds reasonable. Could the pulling effect be caused by the rather small size of the shroud? Suppose the shroud was ten times bigger with say 10 feet in all directions away from the bike, that should change the pulling effect if that is present, right?
So 90 (on the moon with all the gear) to 180 on earth is about half. As far as radial bearing load capacity is concerned, both loadings are very small. There should be a drop in rolling resistance on the moon, but I don't see much of anything else.
I think the limiting factor would be human physiology. Lets say a human on the moon with all the gear has a mass of 200 ...[text shortened]... n supply 1 Hp for mere seconds. I conclude there is something helping her along that is not "seen".
Suppose we move the goalpost a bit: Now the track on the moon is magnetic like a maglev and the bike is maglev'd off the surface of the metal track so the pedals are now powering a superconducting alternator (virtually 100% efficient conversion of pedal power to electricity) and that energy now powers a linear electric motor while being suspended over the track magnetically and the drive force comes also magnetically. I wonder how fast she could go under those circumstances on the moon?
- Joined
- 10 Dec 06
- Moves
- 8528
@sonhouse said"Sounds reasonable. Could the pulling effect be caused by the rather small size of the shroud? Suppose the shroud was ten times bigger with say 10 feet in all directions away from the bike, that should change the pulling effect if that is present, right?"
Sounds reasonable. Could the pulling effect be caused by the rather small size of the shroud? Suppose the shroud was ten times bigger with say 10 feet in all directions away from the bike, that should change the pulling effect if that is present, right?
Suppose we move the goalpost a bit: Now the track on the moon is magnetic like a maglev and the bike is maglev'd off the ...[text shortened]... force comes also magnetically. I wonder how fast she could go under those circumstances on the moon?
I'm sure it would. From what I'm reading on the slipstream, a zone of low pressure is created behind the vehicle. The rear of the zone could be pushing her along a bit.
"Suppose we move the goalpost a bit: Now the track on the moon is magnetic like a maglev and the bike is maglev'd off the surface of the metal track so the pedals are now powering a superconducting alternator (virtually 100% efficient conversion of pedal power to electricity) and that energy now powers a linear electric motor while being suspended over the track magnetically and the drive force comes also magnetically. I wonder how fast she could go under those circumstances on the moon?"
Lets drop the maglev stuff because it is not intrinsic to the argument of what happens without frictional resistance of any type. Also, another thing that won't exist is a drive train that converts rotational motion into translational motion without any energy absorption of it own. For instance, even in your mag lev electrical motor drive some of the energy from your pedaling will be used to spin up the rotor.
However, since we are talking about riding bike on the moon in space suits...we can pretend.
Again this basically comes down to human physiology. I'm making an educated guess the best cyclist can sustain 250 W power output for like 4 hrs. If our cyclist has a mass of 70 kg and is beginning from rest and his/her output directly converts to translational kinetic energy then it works out to about 718 mph.
Obviously this strongly depends on the actual output and output duration of a rider.
@joe-shmo saidAnd tires that can take that kind of velocity and an airless place to do it in.
"Sounds reasonable. Could the pulling effect be caused by the rather small size of the shroud? Suppose the shroud was ten times bigger with say 10 feet in all directions away from the bike, that should change the pulling effect if that is present, right?"
I'm sure it would. From what I'm reading on the slipstream, a zone of low pressure is created behind the vehicle. Th ...[text shortened]... out 718 mph.
Obviously this strongly depends on the actual output and output duration of a rider.
If room temperature superconductors are ever developed then a pedal powered bike on the moon would be as close to 100% efficient as it is possible to get so there would not be much absorbed in eddy currents and such.
@sonhouse saidthey'd just fly off the face of the moon...
https://www.cnn.com/2018/09/19/health/woman-rides-bike-183-mph-trnd/
This is with a big windshield in front. Denise Mueller-Korenek.
They must have had a very high gear to wheel ratio!
This begs the question, suppose you were on the moon, with of course space suit and such, with no atmosphere at all, how fast could a human go on a bicycle there? Assuming they had a nice paved course up there....
- Joined
- 10 Dec 06
- Moves
- 8528
@karoly-aczel saidNah, that wouldn’t happen until they were traveling about 3,800 mph. ( ball park figure around traveling along a great circle)
they'd just fly off the face of the moon...