Author Topic: plane on a conveyor belt? (Read 19893 times)

lukster · « **Reply #390 on:** January 26, 2007, 06:16:44 PM »

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Originally posted by Golfer
You're allowed to agree that it will fly, lukster. It's not too late for that.

The question was abiguous, there's more than one interpretation and a few variables that will allow it to fly. I'm only saying that if the wheel speed is what the belt matches in the opposite direction and is capable of accelerating at a rate capable of inducing into the wheel a force equal to the engine's thrust it will not.

Golfer · « **Reply #391 on:** January 26, 2007, 06:17:49 PM »

I'm trying to uncomplicate things.

Answer the question. Come up with something that invalidates the boat example and we'll name the theory of aircraft conveyor relativity after you.

The examples are valid. Air is the fluid through wich an airplane passes. Water is the fluid through which a boat travels. The conveyor works the same way.

Invalidate the boat.

lukster · « **Reply #392 on:** January 26, 2007, 06:25:36 PM »

Quote

Originally posted by Golfer
I'm trying to uncomplicate things.

Answer the question. Come up with something that invalidates the boat example and we'll name the theory of aircraft conveyor relativity after you.

The examples are valid. Air is the fluid through wich an airplane passes. Water is the fluid through which a boat travels. The conveyor works the same way.

Invalidate the boat.

I don't understand how your boat scenario is any different from the plane. I'm sorry but I couldn't follow your explanation. Tell me how your boat scanario is different from that of the plane and let's talk about that.

Golfer · « **Reply #393 on:** January 26, 2007, 06:27:29 PM »

Quote

Originally posted by lukster
if the wheel speed is what the belt matches in the opposite direction and is capable of accelerating at a rate capable of inducing into the wheel a force equal to the engine's thrust it will not.

Exactly how do you plan on getting a spinning wheel on a spinning treadmill to counteract 6,800lbs of thrust for something like a Citation Encore?

Golfer · « **Reply #394 on:** January 26, 2007, 06:28:11 PM »

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Originally posted by lukster
I don't understand how your boat scenario is any different from the plane. I'm sorry but I couldn't follow your explanation. Tell me how your boat scanario is different from that of the plane and let's talk about that.

BINGO! It's not any different all. The boat goes...the plane goes...the end!

lukster · « **Reply #395 on:** January 26, 2007, 06:28:30 PM »

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Originally posted by Golfer
Exactly how do you plan on getting a spinning wheel on a spinning treadmill to counteract 6,800lbs of thrust for something like a Citation Encore?

How about a belt that is accelerating at 1,000,000 mph/s, think that will do it?

eskimo2 · « **Reply #396 on:** January 26, 2007, 06:30:39 PM »

Here is a glimpse into how a treadmill pushes a wheel back as it accelerates. Note the set-up:

The fire extinguisher is an anchor (overkill, I know) for the rubber band that is tied to a wire that is looped through the axel of the wheel. To keep everything aligned, the wire goes through tubes that are taped to the green stool.

The wheel is resting on the belt sander. When the sander is turned on, the sander and the wheel gain RPM for less than ½ a second. During this time, the wheel shoots to the right, stretching the rubber band. When the sander and wheel stop accelerating and the RPM become constant, the wheel is no longer gaining significant energy from the belt and the rubber band pulls the wheel back to the left where it spins merrily in a steady state of energy.

The acceleration of the wheel stretched the rubber band in the direction of the treadmill (belt sander). This is an example of how a treadmill of unlimited speed could load energy into a wheel of unlimited strength (and through a perfect bearing) through rotational acceleration. Since the force is only applied to the bottom of the wheel where it contacts the treadmill, it is not balanced. A vector of the force is applied to the axel in the same direction of the belt. Note that it will not prevent the plane from moving if it only accelerates for ½ a second. The acceleration (increase in RPM) must be constant, and must be massive.

I hooked a crappy variable speed Dremel motor control to the sander. I sort of got the 2 speed effect. Both movies are available in AVI and QuickTime. The QuickTime ones are in the original Nikon format and are a bit sharper and are easier to move frame by frame.

Watch the movie and imagine things on a much greater scale.

1/250th exposure wheel on sander:
http://hallbuzz.com/movies/wheel_on_sander_250th.AVI
http://hallbuzz.com/movies/wheel_on_sander_250th.MOV

1/250th exposure 2-speed wheel on sander:
http://hallbuzz.com/movies/wheel_on_sander_2_speed.AVI
http://hallbuzz.com/movies/wheel_on_sander_2_speed.MOV

Better movies:

Here is a paper treadmill; the source off acceleration is a falling shoe tied to the paper. On the paper treadmill are a mouse ball, a copper pipe with a rubber band glued around it for traction, and an acrylic ball that may have skid/slip some.

Picture of the set up:

AVI:
http://hallbuzz.com/movies/paper_treadmill.AVI

QuickTime
http://hallbuzz.com/movies/paper_treadmill.MOV

Golfer · « **Reply #397 on:** January 26, 2007, 06:30:40 PM »

Since the the belt is supposed to match the wheel speed...if the airplane is moving forward at 1,000,000mph then your belt would still only double the wheelspeed.

Golfer · « **Reply #398 on:** January 26, 2007, 06:35:59 PM »

Eskimo in all of your experiments the conveyor is initiating the action onto the wheel. In the question its the wheel that initiates the conveyor.

If your points regarding this are valid I have just one more question...

Why can't you dyno an airplane?

That right there blows any argument could make right out of the water. You dyno an airplane in a still-air environment then I might listen to what you have to say. Other than that...can't be done.

get an airplane to dyno on one of these...your arguments are all valid. You won't...

lukster · « **Reply #399 on:** January 26, 2007, 06:38:17 PM »

Quote

Originally posted by Golfer
Since the the belt is supposed to match the wheel speed...if the airplane is moving forward at 1,000,000mph then your belt would still only double the wheelspeed.

The plane isn't moving at all but the wheel is accelerating and the belt is accelerating at 1,000,000mph/s.

Take it away Eskimo.

Golfer · « **Reply #400 on:** January 26, 2007, 06:43:52 PM »

See above.

eskimo2 · « **Reply #401 on:** January 26, 2007, 06:56:00 PM »

I think part of the problem here is that when people finally realize that there is a real force involved in accelerating a rotating object they just can’t get past that it could potentially rival the power of an aircraft engine.

It’s like saying, “Ants could never win a tug-o-war against a human.” At first it sounds true and obvious. When you think about it, however, there is one very important letter in that statement that we all would naturally overlook. Plural has no upper limit.

SteveBailey · « **Reply #402 on:** January 26, 2007, 06:59:21 PM »

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You think it's not possible for the engine to be at full power without rolling the wheels forward? Try tying together two planes facing opposite directions. Anywhere is fine but tie their axles together and you will most closely simulate the force being applied by an accelerating belt. If both planes are identical neither will move with engines at full power.

No, i'm saying that the wheels can only begin moving by the plane rolling forward. If the hweels of the plane stop moving forward, as you said they would,(you said the plane would stop) then since the wheels were no longer acceolerating, the conveyer would catch up. If the wheels are no longer moving forward, and the conveyer does not spin the wheels, but merely paces it, the wheels will slow down and stop since there is nothing causing the wheels to spin. Again, in youir model, the plane stops, the wheels stop, the conveyer stops yet the plane goes nowhere.

2bighorn · « **Reply #403 on:** January 26, 2007, 07:09:28 PM »

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Originally posted by eskimo2
I think part of the problem here is that when people finally realize that there is a real force involved in accelerating a rotating object they just can’t get past that it could potentially rival the power of an aircraft engine.

True, what you don't realize is that maximum amount of force you can transfer from conveyor to the airframe is equal that of rolling resistance which is defined as following:

Rolling resistance = ((Aircraft weight X gravitational acceleration) / number of wheels) X coefficient of rolling friction

Coefficient of rolling friction used in aircraft industry is about 0.0035 in average.

Now do some math and you'll see that amount of your usable force is nothing in comparison to the thrust.

lukster · « **Reply #404 on:** January 26, 2007, 07:12:58 PM »

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Originally posted by 2bighorn
True, what you don't realize is that maximum amount of force you can transfer from conveyor to the airframe is equal that of rolling resistance which is defined as following:

Rolling resistance = ((Aircraft weight X gravitational acceleration) / number of wheels) X coefficient of rolling friction

Coefficient of rolling friction used in aircraft industry is about 0.0035 in average.

Now do some math and you'll see that amount of your usable force is nothing in comparison to the thrust.

You do the math and see if your engine can overcome the coefficient of friction of your skidding tires. If it can I just increase the acceleration to reduce your tires to smoke in a microsecond. Then you have to figure the drag of the gear. I already addressed this.