Moon Track Days

[Mr_Yuk]

I hope I did not already post this, but here goes anyway.

 

Do your best laps on your favorite track here on earth. Now transport that exact track to the moon and try again. The "Moon" track is inside a building with controlled atmosphere to exactly match the pressure and composition of your "Earth" track atmosphere. How will your lap times compare? Faster on the earth, slower on the earth, or no appreciable difference, AND WHY?

 

No credit given for the correct answer without a correct explanation of why. What credit do you get if you are correct? Maybe an "Atta Boy" from others that answered, but absolutely nothing material. And if you just said, "Ah sh*t," then no "Atta Boy" either.

 

Rod

[Boffin]

If I recall my school-boy physics correctly, tap times would probably be lower, due to the lower gravity reducing available grip. My (suspect) memory tells me that friction is related to force/surface area, so with a lower force from gravity, the friction of rubber to road will be lower.

 

Andy

[Quinn]

Andy, why would motorcycle builders keep trying to make lighter bikes if that were the case?

 

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[Boffin]

Because a lighter bike has less mass, which needs less force to keep it stuck to the road. Low gravity keeps the mass constant whilst reducing the weight.

 

Andy

[tallman]

By "pressure and composition of the earth's track atmosphere" are you including gravity?

If not, you and your bike would weigh about 1/6th of what they do on earth.

Power output woould not be diminished so...

[Boffin]

By "pressure and composition of the earth's track atmosphere" are you including gravity?

If not, you and your bike would weigh about 1/6th of what they do on earth.

Power output woould not be diminished so...

 

The bikes mass would be undiminished. We refer to power-to-weight ratios, but they are really power to mass ratios. Acceleration would not be impacted.

 

Andy

[flars]

I'd still be faster than Russell, but slower than Vale.

[Joe Frickin' Friday]

If I recall my school-boy physics correctly, tap times would probably be lower, due to the lower gravity reducing available grip. My (suspect) memory tells me that friction is related to force/surface area, so with a lower force from gravity, the friction of rubber to road will be lower.

 

Not only this, but because of reduced gravity and unchanged power output, the bike would wheelie and stoppie far more easily. My RT will barely wheelie at WOT in first gear, so with 1/6 normal gravity, I could only accelerate forward at about 1/6 its earthly maximum rate; I'd have to go very gently on the throttle until I got to higher gears.

 

Braking on the RT appears to be traction-limited, that is to say, the front wheel usually slips before the rear wheel comes up. This is typically not true of sport and track bikes, which means they'll only be able to decelerate at 1/6 their earthly maximum rate before risking the rear wheel coming off the ground.

 

Without the ability to corner/accel/decel at high absolute accelerations, lap times on the moon will be agonizingly slow.

[Joe Frickin' Friday]

Because a lighter bike has less mass, which needs less force to keep it stuck to the road. Low gravity keeps the mass constant whilst reducing the weight.

 

Ayup. The benefit of reduced mass is better forward acceleration for a given engine power output, and snappier handling (a GP bike does better in a fast slalom than a Goldwing).

[Joe Frickin' Friday]

Without the ability to corner/accel/decel at high absolute accelerations, lap times on the moon will be agonizingly slow.

 

I'll even go one step further and note that bumps, dips and hills that would have been adhered to nicely here on earth will, on the moon, result in becoming airborne - in some cases with considerable hangtime.

[Quinn]

So let's take the bike to Jupiter. Lots more traction. Is it going to be faster? Same mass, just heavier.

 

I'm enjoying being the straight man.

 

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[Mr_Yuk]

Here is what I think (in agreement with most of the above answers):

 

Lap times would be much lower on the moon. Consider just the cornering speeds. As noted by Boffin, grip is proportional to weight (mass times gravity) while required grip is the centripetal force in a corner, equal to mass times velocity squared divided by radius. Everything drops out of the ratio equations except the two gravities and the square of the two cornering velocities. The cornering velocity on the moon is the square root of the gravity ratios, or the square root of 1/6, or 40%. So your maximum cornering speeds on the moon would be 40% of what you could do on earth.

 

Rod

[Joe Frickin' Friday]

So let's take the bike to Jupiter. Lots more traction. Is it going to be faster? Same mass, just heavier.

 

That'd be awesome. Same engine power, so you could accelerate just as hard as on earth. in fact, if wheelies were a problem on earth when snapping the throttle open, they certainly won't be on Jupiter. Likewise with braking: Jupiter's surface gravity is ~2.5x Earth's, so your braking distances could be shortened by that much, and by even more if stoppies (on earth) were a problem.

 

Per Rod's analysis, your cornering speeds could be 1.6 times what they were on earth. If catching air on bumps and dips was a problem on earth, it sure wouldn't be on Jupiter.

 

Crashes would be a mixed bag. Falling off the bike or highsiding, you'd hit the pavement with much more vertical speed; it'd feel like falling from 2.5 times as high. OTOH, the added friction would slow you down a lot more rapidly, so you'd be more likely to come to a stop before hitting trackside objects.

 

It would be difficult to keep your head from resting on the tank, and the aero lift on your torso would not mean much in the context of 2.5X earth gravity; your arms would definitely get tired of propping up your upper body.

[Danny caddyshack Noonan]

So let's take the bike to Jupiter. Lots more traction. Is it going to be faster? Same mass, just heavier.

 

 

That'd be awesome. Same engine power, so you could accelerate just as hard as on earth. in fact, if wheelies were a problem on earth when snapping the throttle open, they certainly won't be on Jupiter. Likewise with braking: Jupiter's surface gravity is ~2.5x Earth's, so your braking distances could be shortened by that much, and by even more if stoppies (on earth) were a problem.

 

Per Rod's analysis, your cornering speeds could be 1.6 times what they were on earth. If catching air on bumps and dips was a problem on earth, it sure wouldn't be on Jupiter.

 

Crashes would be a mixed bag. Falling off the bike or highsiding, you'd hit the pavement with much more vertical speed; it'd feel like falling from 2.5 times as high. OTOH, the added friction would slow you down a lot more rapidly, so you'd be more likely to come to a stop before hitting trackside objects.

 

It would be difficult to keep your head from resting on the tank, and the aero lift on your torso would not mean much in the context of 2.5X earth gravity; your arms would definitely get tired of propping up your upper body.

 

Yeah....but, you'd have to start a whole new tire thread.

[ESokoloff]

I would think that turns would have to have more banking (to make up for the reduction of gravity) in order to maintain the same speed as on earth.

[russell_bynum]

I'd still be faster than Russell, but slower than Vale.

 

That's a pretty big target to shoot for.

[artig]

Here is what I think (in agreement with most of the above answers):

 

Lap times would be much lower on the moon. Consider just the cornering speeds. As noted by Boffin, grip is proportional to weight (mass times gravity) while required grip is the centripetal force in a corner, equal to mass times velocity squared divided by radius. Everything drops out of the ratio equations except the two gravities and the square of the two cornering velocities. The cornering velocity on the moon is the square root of the gravity ratios, or the square root of 1/6, or 40%. So your maximum cornering speeds on the moon would be 40% of what you could do on earth.

 

Rod

 

So if the cornering speeds are only 40% of those on earth, wouldn't the lap times be much higher, instead of much lower? (I'm sure some riders would like to know how to reduce lap times by reducing cornering speeds.)

 

[Mr_Yuk]

Here is what I think (in agreement with most of the above answers):

 

Lap times would be much lower on the moon. Consider just the cornering speeds. As noted by Boffin, grip is proportional to weight (mass times gravity) while required grip is the centripetal force in a corner, equal to mass times velocity squared divided by radius. Everything drops out of the ratio equations except the two gravities and the square of the two cornering velocities. The cornering velocity on the moon is the square root of the gravity ratios, or the square root of 1/6, or 40%. So your maximum cornering speeds on the moon would be 40% of what you could do on earth.

 

Rod

 

So if the cornering speeds are only 40% of those on earth, wouldn't the lap times be much higher, instead of much lower? (I'm sure some riders would like to know how to reduce lap times by reducing cornering speeds.)

 

Whoa, what a misstatement on my part. You are exactly correct. I meant to say that lap times would be much higher. I must have been thinking that speeds would be much lower. Actually, who knows what I was thinking?

 

Hope you are having fun with it anyway. Jupiter would be a blast.

 

Rod

[Heck]

Seems like you would need an electric bike for Jupiter....Not much O2 for an internal combustion engine to run....or for you to breathe for that matter.