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So, if you run the conveyor and leave the plane's engines at idle or off, the plane will not move? you're kidding...

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Sorry, you are neglecting the difference between dynamic and static friction. In the case you just posed, the airplane will accelerate backwards due to static friction. Once the static friction is overcome, the wheels will begin spinning and the lower dynamic friction will apply. Once that happens, the plane will cease accelerating backwards, but still be traveling backwards.

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The friction in the bearings is still negligible as far as my claim goes, and I continue to use the assumption of a frictionless bearing.

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Wait, so you're assuming frictionless bearings now? In that case then yes, moving the conveyor underneath the plane will simply cause the wheels to roll and the plane will not move.

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I am simply talking about the rolling resistance of an inflated rubber tire. If we were talking about a train, you'd be correct. However, the difference between the equations and assumptions for steel on steel and rubber on concrete are too different to compare in a problem like this.

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By assuming frictionless bearings, you are removing the temperature increase due to that friction, which is the dominant variable in figuring the coefficient of rolling resistance. Yet you do not eliminate the pressure effect on rolling resistance, which is the lesser variable.

This is an invalid set of assumptions. You can not assume the dominant variable is negligible while figuring in the effects of a lesser variable.

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By assuming frictionless bearings, you are removing the temperature increase due to that friction, which is the dominant variable in figuring the coefficient of rolling resistance. Yet you do not eliminate the pressure effect on rolling resistance, which is the lesser variable.

This is an invalid set of assumptions. You can not assume the dominant variable is negligible while figuring in the effects of a lesser variable.

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What makes it so invalid? If I did consider the heat in the bearings, the coefficent of friction in them would increase with the added heat. This is because of two things: 1) thermal expansion increasing the pressure of the rollers on the races, and 2) the changing properties of the wear surfaces and how they interact with each other (heat increases the size of the flaws in the metal).

your claim states that if you take the rollerblader on a treadmill example given earlier, and increase the speed of the treadmill by 1000% it would not put any more tension on the rope that the rollerblader is holding on to...

I just don't know how the posts here can get dumber!

If an aircraft carrier had a conveyor for a runway, would it need wires anymore to snag planes?

If an aircraft carrier had a conveyor belt for the deck, and ran it in the direction of takeoff, would that increase speed, and obviate the need for a steam catapult?

Would it enable us to downsize our carriers?

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What makes it so invalid? If I did consider the heat in the bearings, the coefficent of friction in them would increase with the added heat. This is because of two things: 1) thermal expansion increasing the pressure of the rollers on the races, and 2) the changing properties of the wear surfaces and how they interact with each other (heat increases the size of the flaws in the metal).

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I say again. Coefficient of rolling resistance decreases as temperature increases.

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your claim states that if you take the rollerblader on a treadmill example given earlier, and increase the speed of the treadmill by 1000% it would not put any more tension on the rope that the rollerblader is holding on to...

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Exactly. Again, f = gmc. Where does the speed of the treadmill appear in this equation?

in the c...

there is no title to that chart, but I guaruntee it isn't for the rolling resistance of an inflated rubber tire against concrete.

I would agree that it is for a solid wheel of some type. maybe the steel on steel of the railroad, or a solid plastic wheel on some type of dolly, or cart... maybe even the solid rubber wheels of a forklift...

more than likely it is the Crr chart for a ball, roller or needle bearing pack...

here...first google hit

The question often arises whether a small cross section tire has lower rolling resistance than a larger one. The answer, as often, is yes and no, because unseen factors come into play. Rolling resistance of a tire arises almost entirely from flexural rubber losses in the tire and tube. Rubber, especially with carbon black, as is commonly used in tires, is a high loss material. On the other hand rubber without carbon black although having lower losses, wears rapidly and has miserable traction when wet.

Besides the tread, the tube of an inflated tire is so firmly pressed against the casing that it, in effect, becomes an internal tread. The tread and the tube together absorb the majority of the energy lost in the rolling tire while the inter-cord binder (usually rubber) comes in far behind. Tread scuffing on the road is even less significant.

Patterned treads measurably increase rolling resistance over slicks, because the rubber bulges and deforms into tread voids when pressed against the road. This effect, tread squirm, is mostly absent with smooth tires because it cannot be bulge laterally by road contact because rubber, although elastic, is incompressible.

Small cross section tires experience more deformation than a large cross section tire and therefore, should have greater rolling resistance, but they generally do not, because large and small cross section tires are not identical in other respects. Large tires nearly always have thicker tread and often use heavier tubes, besides having thicker casings. For these reasons, smaller tire usually have lower rolling resistance rather than from the smaller contact patch to which it is often attributed.

These comparative values were measured on various tires over a range of inflation pressures that were used to determine the response to inflation. Cheap heavy tires gave the greatest improvement in rolling resistance with increased pressure but were never as low as high performance tires. High performance tires with thin sidewalls and high TPI (threads per inch) were low in rolling resistance and improved little with increasing inflation pressure.

As is mentioned at "Mounting Tubular Tires", tubulars, although having lower tire losses, performed worse than equivalent clincher tires because the tubular's rim glue absorbs a constant amount of energy regardless of inflation pressure. Only (hard) track glue absolves tubulars of this deficit and should always be used in timed record events.

another good one

any one know when this will be replayed on the discovery channel?

You mean the episode when the plane took off and proved the conveyor was moot?

No, I dont know

Update?

why is this thread still around? it took off.

DIE THREAD DIE!

ttt for Flaith and Badman.

oh if it's purely as an annoyance, i'm in full support of ttting the hell out of this thread

The plane will always take off in any kind of realistically producable simulation. That includes building a friggin runway sized high speed conveyor belt. Please lock this MF'ing thread!

what if we make a runway of pb and jelly sandwiches and change the wheels of the airplane for fat slobs?

conveyor is moot!!

conveyor is moot!!

conveyor is moot!!

conveyor is moot!!

conveyor is moot!!

conveyor is moot!!

crunchy or creamy peanut butter?

ttt for VikingNik

If the point of the plane on a conveyor argument were to find out if the resistance of the wheels were why a plane couldn't take off, the argument wouldn't be the "plane on a conveyor" argument. Instead, it would be "747 on a conveyor" argument. The point of it is the theory behind the whole thing and the understanding that the free-rolling wheels don't provide the propulsion which was demonstrated by a light-weight plane.






So let's sum it up:

1) A plane's propulsion is not from wheels
2) Yes, a plane's wheels have resistance, but that's beside the point. Even with the resistance of the wheels, if you think a big plane doesn't have the power to overcome that resistance... ha.
3) The plane will take off.... deal with it.

4) The conveyor is moot!

The moot is conveyor.

i believe the plane is moot, and the conveyor will take off in flight.

now that being said, anyone know when the mootness will be replayed on the discovery channel.

I don't know if this has been said or not but..

think of it this way, if you are running on a treadmill, do you feel wind hitting you in the face as you would if you were running outside?

no.

ok then, how would a plane under the same conditions be able to lift off?

I really hope you're trolling.

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Jebus H. christ another one?

The earth is a giant conveyor. Planes take off every day in every direction.

hth