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The world's fastest human-powered vehicle tops 85 mph

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Re: The world's fastest human-powered vehicle tops 85 mph

#21

Post by yurisagalov »

irl_zebra wrote: post #19
yurisagalov wrote: post #11

Earlier quoted context omitted.

Todd is actually a world-class rider (based on the chart you provided, as well). From the article before they won the Sikorsky prize: "Reichert, a national-level speed skater, can pedal at 1.2 horsepower for a full minute" http://m.thestar.com/#/article/news/gta/2012/08/26/humanpowe...

EDIT: Made a mistake with the numbers! This is interesting; 1.2hp is about 895 watts. Assuming he's probably 65kg (total guess from the looks of him). That means he can do about 13.7 Watts/KG for 1-minute. According to the chart I posted above, looking at 1 minute power, that puts him as a Far to Moderate level cyclist. Even giving the benefit of the doubt and assuming 55kg, making the ratio a better 16.2 Watts/KG, t…

You are looking at maximal power output for 5 seconds (the left most column) while you should be looking at maximal power output for 1 minute (the 2nd column from left) :)

Re: The world's fastest human-powered vehicle tops 85 mph

#22

Post by QuotedForTruth »

darkstar999 wrote: post #14
drpgq wrote: post #8

I wonder why for fastest human-powered they don't use more than one cyclist. I assume with eight humans like in rowing you could get up to a ridiculous speed. Might be a little dangerous though.

Would the multiplied power be offset by the multiplied weight and potential loss of aerodynamics?

Max speed has very little to do with weight as long as you have sufficient room to accelerate. Additional drag would be small if you put one rider in front of the other and both inside of a fairing. The frontal area and shape could stay the same. This is the major source of drag. There would be small amounts of additional drag from the air running along a longer fairing, but doubling the power would more than make up for it.

However, the speed would nowhere near double. Power required to overcome drag force is related to velocity cubed. So if you double power, the velocity will increase by a factor of (2)^1/3 or the cube root of 2, 1.259.

So if they added another rider of equal power and managed to keep drag the same (it would actually increase a little) they'd go around 25% faster or 107 mph. You may run into other problems like stability and bumpiness first though.

Re: The world's fastest human-powered vehicle tops 85 mph

#23

Post by msandford »

yurisagalov wrote: post #11
irl_zebra wrote: post #4

I'm guessing something can't get much more aerodynamically shaped? I wonder if they used a power meter to measure the driver/rider's power output and whether the driver was an accomplished cyclist. It seems that at this point, it would simply be a matter of getting a stronger cyclist, say someone like Brad Wiggins who can push 430 watts for an hour over an amateur, but still respectable rider, who puts out something…

Todd is actually a world-class rider (based on the chart you provided, as well). From the article before they won the Sikorsky prize: "Reichert, a national-level speed skater, can pedal at 1.2 horsepower for a full minute" http://m.thestar.com/#/article/news/gta/2012/08/26/humanpowe...

1.2 horsepower for a minute is a damn fine effort. A college friend of mine is a domestic pro. Last I heard his max power was 1100 watts and his 30 second power was 1050 watts.

One horsepower is 732 watts so 1.2 * 732 = 878 which is an entirely reasonable number for a 60 second power test.

Also remember that drag goes with the speed squared, so getting a cyclist who is 20% more powerful might cause less than a 10% increase in speed, especially considering that the power of the cyclist may not be the limiting factor but instead the ergonomics of the vehicle, getting the run exactly right (being at max speed over the right 200m rather than any 200m), or something else entirely.

Re: The world's fastest human-powered vehicle tops 85 mph

#24

Post by [deleted] »

irl_zebra wrote: post #19
yurisagalov wrote: post #11

Earlier quoted context omitted.

Todd is actually a world-class rider (based on the chart you provided, as well). From the article before they won the Sikorsky prize: "Reichert, a national-level speed skater, can pedal at 1.2 horsepower for a full minute" http://m.thestar.com/#/article/news/gta/2012/08/26/humanpowe...

EDIT: Made a mistake with the numbers! This is interesting; 1.2hp is about 895 watts. Assuming he's probably 65kg (total guess from the looks of him). That means he can do about 13.7 Watts/KG for 1-minute. According to the chart I posted above, looking at 1 minute power, that puts him as a Far to Moderate level cyclist. Even giving the benefit of the doubt and assuming 55kg, making the ratio a better 16.2 Watts/KG, t…

[deleted]

Re: The world's fastest human-powered vehicle tops 85 mph

#25

Post by irl_zebra »

yurisagalov wrote: post #21
irl_zebra wrote: post #19

Earlier quoted context omitted.

EDIT: Made a mistake with the numbers! This is interesting; 1.2hp is about 895 watts. Assuming he's probably 65kg (total guess from the looks of him). That means he can do about 13.7 Watts/KG for 1-minute. According to the chart I posted above, looking at 1 minute power, that puts him as a Far to Moderate level cyclist. Even giving the benefit of the doubt and assuming 55kg, making the ratio a better 16.2 Watts/KG, t…

You are looking at maximal power output for 5 seconds (the left most column) while you should be looking at maximal power output for 1 minute (the 2nd column from left) :)

Wow you're absolutely right, my mistake! Todd must be a very, very fantastic cyclist!

Re: The world's fastest human-powered vehicle tops 85 mph

#26

Post by irl_zebra »

Semiapies wrote: post #17
drpgq wrote: post #8

I wonder why for fastest human-powered they don't use more than one cyclist. I assume with eight humans like in rowing you could get up to a ridiculous speed. Might be a little dangerous though.

This isn't horribly safe, either. Wiping out at 85 MPH would suck . I'm curious what multi-cyclist vehicles could do, now that you suggest it. With the lightness of these vehicles, at what point would you have to add spoilers?

While I know it would suck to wipe out, I'm hoping with this thing it may be more of a "slide for 1000ft and off the flat road" type of suck than a "life altering injury" type of suck.

Re: The world's fastest human-powered vehicle tops 85 mph

#27

Post by darkmighty »

msandford wrote: post #23
yurisagalov wrote: post #11

Earlier quoted context omitted.

Todd is actually a world-class rider (based on the chart you provided, as well). From the article before they won the Sikorsky prize: "Reichert, a national-level speed skater, can pedal at 1.2 horsepower for a full minute" http://m.thestar.com/#/article/news/gta/2012/08/26/humanpowe...

1.2 horsepower for a minute is a damn fine effort. A college friend of mine is a domestic pro. Last I heard his max power was 1100 watts and his 30 second power was 1050 watts. One horsepower is 732 watts so 1.2 * 732 = 878 which is an entirely reasonable number for a 60 second power test. Also remember that drag goes with the speed squared, so getting a cyclist who is 20% more powerful might cause less than a 10% in…

I guess he has also the advantage that he can train specifically for this kind of burst power. All his other projects were of this kind -- a minute or two of maximum possible power.

Re: The world's fastest human-powered vehicle tops 85 mph

#28

Post by sandworm101 »

So my question is now: In terms of aerodynamics, what aren't they doing?

Some commentators have noted that the shape of this bike is just about as good as it can get. The rider/engine is also not going to see any vast improvements. So rather than this become a pure athletic event, where can engineers look for improvements? Will they have to start dealing with boundary layer issues? Will the next generation of bike be covered in golfball-like holes to reduce turbulence?

Re: The world's fastest human-powered vehicle tops 85 mph

#29

Post by msandford »

darkmighty wrote: post #27
msandford wrote: post #23

Earlier quoted context omitted.

1.2 horsepower for a minute is a damn fine effort. A college friend of mine is a domestic pro. Last I heard his max power was 1100 watts and his 30 second power was 1050 watts. One horsepower is 732 watts so 1.2 * 732 = 878 which is an entirely reasonable number for a 60 second power test. Also remember that drag goes with the speed squared, so getting a cyclist who is 20% more powerful might cause less than a 10% in…

I guess he has also the advantage that he can train specifically for this kind of burst power. All his other projects were of this kind -- a minute or two of maximum possible power.

It's actually a very specific power profile. It'll be 10-20 or so minutes of work for the actual run (at 30mph it's 2 minutes a mile and you'll spend plenty of time under 30), but perhaps with an hour or more surrounding. Some amount of warm up almost for sure possibly with some substantial efforts.

The body has only a few kilojoules of oxygen debt that it can get into before the pain becomes too much and you're forced to slow down to stop the pain. It's important that you spend those kilojoules just right. So that means accelerating aerobically as long as possible, which is going to be a slow acceleration. You might not use all five miles, but I would wager a good portion of it. And using a power meter to ensure that the cyclist doesn't go anerobic before the critical portion is actually really smart (I don't know if they did this).

The goal is to be doing 50-60mph aerobically (or whatever you can actually do) and then have a 30-60 second interval start at exactly the right point to lead to maximum speed over the 200m. But because the human body isn't as precise as our measurements, you'll never get it exactly right. Some days at the end of the 200m you'll say "I still had some legs left" and other days you'll start to fall apart before the start of the timed 200m.

Re: The world's fastest human-powered vehicle tops 85 mph

#30

Post by [deleted] »

sandworm101 wrote: post #28

So my question is now: In terms of aerodynamics, what aren't they doing? Some commentators have noted that the shape of this bike is just about as good as it can get. The rider/engine is also not going to see any vast improvements. So rather than this become a pure athletic event, where can engineers look for improvements? Will they have to start dealing with boundary layer issues? Will the next generation of bike be…

[deleted]
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