Here is the definitive article!! When the conveyor belt is stationary, so is the plane. And the forces described in the picture are nil. Start the conveyor belt. As the tethering mast/rope initially have to overcome inertia, the load on the tethering pylon is greater, until the wheels start turning.It then decreases, once inertia is overcome, and remains steady.By a VERY crude experiment, I have worked out the coefficient of inert mass weight to actual force to overcome the inertia OF that weight..it is roughly, 7%.of the weight of the object, in ft/lbs. In other words if the plane weighs 1000lbs, it will exert 70 ft/lbs of load on the tethering pylon to keep the plane in place.NOW!!!!! Replace the tether mast AND ROPE with an engine and propeller, exerting 70ft/lbs of THRUST on the STATIONARY AIR surrounding the plane, and the plane will STILL stand still!! NOW...if you speed the conveyor belt up by 100%...does the load on the tether, or the engine/propeller increase by 100%? NO, IT DOESN¨T! It increases at a rate of 7%, not 100%. And so, even if the conveyor belt can speed up to 10000 mph, it does NOT exert more force on the tether at a greater rate than 7%. So, by that equation, if it takes 70 ft/lbs of thrust to keep it stationary, it will only take the normal thrust, PLUS the 70 ft/lbs, to enable the plane to move forward, and take off.
Nick
[This message has been edited by fierofetish (edited 01-06-2008).]
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08:25 AM
fierobear Member
Posts: 27106 From: Safe in the Carolinas Registered: Aug 2000
Nick, Thanks for the calulations. It's alot more than most in this thread. Yea, I know you said something in the 1st page similar but hard facts is what I was after. Your argument is pretty convincing so for now I will concede and say the plane could fly but the tires will blow so the plane won't fly.
[This message has been edited by Gokart Mozart (edited 01-06-2008).]
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11:44 AM
fierobear Member
Posts: 27106 From: Safe in the Carolinas Registered: Aug 2000
Nick, Thanks for the calulations. It's alot more than most in this thread. Yea, I know you said something in the 1st page similar but hard facts is what I was after. Your argument is pretty convincing so for now I will concede and say the plane could fly but the tires will blow so the plane won't fly.
So...assuming the tires *don't* blow...you agree the plane will fly?
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12:45 PM
blackrams Member
Posts: 33163 From: Covington, TN, USA Registered: Feb 2003
Gokart...what makes a helicopter lift off the ground?
According to John Stricker, they're so ugly the ground repels them and once in the air, according to you, they beat the air into submission. If I had only known those two theories while in flight school, I could have sailed through contact phase.
------------------ Ron
It's the Soldier, not the reporter Who has given us the freedom of the press. It's the Soldier, not the poet, Who has given us the freedom of speech. It's the Soldier, not the politicians That ensures our right to Life, Liberty and the Pursuit of Happiness. It's the Soldier who salutes the flag, Who serves beneath the flag, And whose coffin is draped by the flag.
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03:26 PM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Nick, Thanks for the calulations. It's alot more than most in this thread. Yea, I know you said something in the 1st page similar but hard facts is what I was after. Your argument is pretty convincing so for now I will concede and say the plane could fly but the tires will blow so the plane won't fly.
The tires are going to blow becaue they're turning twice take off speed?
Hi Dan!! Just one final little point about the tyres ..as the speed of the plane increases, so does the lift caused by the wings, increasing until the plane finally leaves the ground. The load on the tyres diminishes at an equal rate to the lift of the wings..so the tyres won´t blow or shred either Nick
quote
Originally posted by Gokart Mozart:
Nick, Thanks for the calulations. It's alot more than most in this thread. Yea, I know you said something in the 1st page similar but hard facts is what I was after. Your argument is pretty convincing so for now I will concede and say the plane could fly but the tires will blow so the plane won't fly.
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04:20 PM
Gokart Mozart Member
Posts: 12143 From: Metro Detroit Registered: Mar 2003
Sec. 37.167 Aircraft Tires--TSO--C62c. (a) Applicability. This technical standard order (TSO) prescribes the minimum performance standards that tires, excluding tailwheel tires, must meet in order to be identified with the applicable TSO marking. Tires which are to be so identified and which are manufactured on or after (the effective date of this amendment) must meet the requirements of the "Federal Aviation Administration Standard for Aircraft Tires," dated (the effective date of this amendment), set forth at the end of this section. (b) Marking. In lieu of the marking requirements of sec. 37.7(d), aircraft tires must be legibly and permanently marked at least with the following: (1) Brand name and the name or registered trademark of the manufacturer responsible for compliance. (2) Speed rating, load rating, size, skid depth, serial number, and the manufacturer's part number and plant code. (3) Applicable technical standard order (TSO) number. (c) Data requirements. (1) In addition to the data specified in Sec. 37.5, the manufacturer must also furnish to the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration (or, in the case of the Western Region, the Chief, Aircraft Engineering Division), in the region in which the manufacturer is located, one copy, or copies as otherwise requested by the regional office, of the following technical data: Speed rating, load rating, rated inflation pressure, tire size, width, outside diameter, weight, skid depth, static unbalance of the test tire, wheel rim designation, manufacturer's part number, and, for high-speed tires, a summary of the load-speed-time parameters used in the dynamometer tests. As used in this section, the term "high-speed tire" means a tire tested at a speed greater than 120 mph. (2) The manufacturer must also furnish the applicable maintenance and repair instructions to the regional office identified in paragraph (c)(1) of this section. The maintenance data provided by the manufacturer must include inspection criteria for tires to determine eligibility for used tires to be continued in service. Recapping procedures must included in the maintenance information along with any special repair methods applicable to the tire and special nondestructive inspection techniques. (d) Previously approved equipment. Notwithstanding Sec. 37.3(a) and (b) of this part and the provisions of any specific previous TSO approval, after (the date 2 years after the effective date of this amendment) no person may identify or mark a tire with TSO numbers TSO-C62, TSO-C62a, or TSO-C62b.
Wiki Aircraft Aircraft tires are designed to withstand heavy loads for short durations. The number of tires required for aircraft increase with the weight of the plane. Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel away water to prevent hydroplaning, and for braking traction. Aircraft tires are usually inflated with nitrogen gas in order to minimize the expansion and contraction due to the extreme changes in temperature experienced during flight. Dry nitrogen expands at the same rate as other dry atmospheric gases, but common compressed air sources may contain some moisture, which would increase the expansion rate with temperature. Aircraft tires generally operate at high pressures, up to 200 psi (13.8 bar) for airliners and higher for business jets. Aircraft tires also include heat fuses, which melt when a certain temperature is reached. Tires often overheat if maximum braking is applied during a rejected takeoff or an emergency landing. The fuses provide a safer failure mode, since the tire will no longer explode when overheated, but deflate in a controlled way, thus minimizing damage to aircraft or injury to people on the ground. The main purpose of requiring that an inert gas, such as nitrogen, be used instead of air, for inflation of tires on certain transport category airplanes is prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching autoignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion. Federal Aviation Administration 14 CFR Part 25 [Docket No. 26147; Notice No. 90-7] RIN 2120-AD37 Use of Nitrogen or Other Inert Gas for Tire Inflation in Lieu of Air
If the tires are rated to 120, what would happen if you take them faster?
You mean to say you haven't tried this with your daily driver on at least one occasion?
Seriously though, you're trying awfully hard to continue your argument if you're now making an issue of the wheels/tires spinning twice (not a thousand times) their normal take-off speed.
"...and I would think that the strain on the tires when landing would be be a whole lot higher than during take-off." Really. As it turns out, Safety Factor on tires is dependent on several variables, of which speed is only one. A little googling found that tires are usually built on a safety factor of 8, and that is on a NEW tire, properly mounted and balanced on good rim, under proper loads, inflations, etc. Age of a tire may drop that to 4. The factor is basically calculated by loading divided by use. It was also noted that a "ZR" rated tire may not hold up to its speed rating indefinitely.
Not that it has that much to do with the ultimate question. Just interesting. Also found out that rolling resistance often increases with tire speed. Obviously not enough to ground a plane though.
[This message has been edited by TennT (edited 01-06-2008).]
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05:41 PM
fierobear Member
Posts: 27106 From: Safe in the Carolinas Registered: Aug 2000
Originally posted by AntiKev: Yeah, especially when ham-handed student pilots land REALLY hard time after time until they learn finesse.
Even guys with more experience make mistakes. I've got 650 hours, and I flat-spotted a main tire getting my T210 into Sea Ranch by braking a little too hard. Airplane tires are made to stand up to the stress of landing. Consider that you're putting 4000+ pounds onto those tires, which have to go from zero to landing speed on contact with the runway.
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05:48 PM
PFF
System Bot
fierobear Member
Posts: 27106 From: Safe in the Carolinas Registered: Aug 2000
Even guys with more experience make mistakes. I've got 650 hours, and I flat-spotted a main tire getting my T210 into Sea Ranch by braking a little too hard. Airplane tires are made to stand up to the stress of landing. Consider that you're putting 4000+ pounds onto those tires, which have to go from zero to landing speed on contact with the runway.
Not to get too far off topic, but when I was at NASA, one of the landings I worked on (I forget the mission number) the pilot hit the brakes either too soon or too hard and locked up one of the rear main gear. The inner tire on the right side blew, and the outer tire was down to the cord and looked like it could blow at any moment. We had to set up a perimeter and wait for the tire to cool down before approaching.
Guess it can happen to anyone. Although, in his defense, it is a 100 ton glider touching down at over 200 mph.
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06:04 PM
Patrick Member
Posts: 39122 From: Vancouver, British Columbia, Canada Registered: Apr 99
Fact is the plane will fly as the trust is produced by the engine which turns a propeller which pushes against the air.
If the engine is not producing thrust the aircraft wont move on the treadmill.
If the engine is producing full thrust the aircraft will take off regardless of how fast the treadmill is going.
Side note:
Even a light plane can produce enough thrust to pull a tie down out of the ground concrete and all. I know this for a fact as a tard at the airport was about to taxi for takeoff with 60 pounds of concrete tied to the tail. Had he tried to take off he would probably have qualied as a Darwin Award candidate. I'll have to look around for the picture.
Not that it has that much to do with the ultimate question. Just interesting. Also found out that rolling resistance often increases with tire speed. Obviously not enough to ground a plane though.
Rolling resistance will only increase in a tyre fitted to a car-type vehicle, where downforce will put a heavier load onto the tyres, meaning the tyre will run with a bigger 'footprint' of contact with the road. And as that footprint is flat, the tyre has to continually flex from round to flat at the point of contact with the road. Under-inflated tyres at motorway speeds cause blow-outs for that very reason..the tyre fabric has to flex continually, which generates a lot of heat. Rolling resistance on a plane will DECREASE as it picks up speed, because the lift from the wings increases with speed, reducing the pressure on the tyres, so they don´t have to flex as much as a car's tyres... Nick
You mean to say you haven't tried this with your daily driver on at least one occasion?
Back when I was 18 (and stupid), and had my second Fiero; I was driving one morning and was late for school. I can personally say that a space saver tire rated for 50MPH will roll around 100MPH without blowing. (It wasn't till after I got to school that I remembered that I had a space saver tire on the front). ...And no, no box full of kittens, nuns, or space saver tires were harmed in the trip that morning.
[This message has been edited by Deabionni (edited 01-07-2008).]
Originally posted by Patrick: ...and I would think that the strain on the tires when landing would be be a whole lot higher than during take-off.
for the obvious "hitting the ground" reason - but also because upon landing, you are coming DOWN for WAY faster than 120. if 120 is the take off speed, 200 is probably the landing speed. so - hitting the pavement - full wieght of aircraft, at over 200 mph - then applying full brakeing. yes - if the plane can handle the landing - it can most certainly handle a treadmill take-off. and - it will take off. unless you actually tether it - as some have mentioned. then - of course it wont. but - the wheels - as long as they are free to roll in any direction, and at any speed - the plane will take off.
how's about this: if a plane flys a few feet OVER a teadmill spinning at the same speed as the plane is flying, but in the opposite direction, does the plane suddenly go backwards or crash? of course not - so - how the heck does it affect the takeoff? it doesnt. the wheels are just things to keep the thing from dragging along the ground. they have nothing to do with the take-off - other than to reduce ground friction.
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09:44 AM
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
If the tires are rated to 120, what would happen if you take them faster?
I'd mount tires with a higher speed rating.
Incidentally, FAA certification requirements for all single-engine airplanes require a stall speed (and thus a minimum takeoff speed) of less than 62 mph. Tires rated for 120 mph would still be suitable for the problem as stated.
Oh, yes. The airplane will still fly!
[This message has been edited by Marvin McInnis (edited 01-07-2008).]
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09:55 AM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Incidentally, FAA certification requirements for all single-engine airplanes require a stall speed (and thus a minimum takeoff speed) of less than 62 mph. Tires rated for 120 mph would still be suitable for the problem as stated.
Oh, yes. The airplane will still fly!
But, but, but, what if the take off speed was half a billion mph and the tires had to spin a billion mph, and, and, and there were bugs on the windshield causing more drag, and uh, uh, the wheel bearings had peanut butter in them instead of grease, and and and and uh, the air was made of glycerine? Huh, what then yeah?
------------------ Calling an illegal alien an "undocumented worker" is like calling a heroin dealer an "undocumented pharmacist."
[This message has been edited by Formula88 (edited 01-07-2008).]
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10:31 AM
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
If if if, remember, land speed records are set using tires. Glad to see you finaly got it though.
Speed ratings for car tires M 81 mph N 87 mph P 93 mph Q 99 mph R 106 mph S 112 mph T 118 mph U 124 mph H 130 mph V 149 mph When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities. W 168 mph Y 186 mph
http://www.saltflats.com/I30%20Club.html 130 MPH Club Rules Vehicles must have H, V, or Z rated tires which are rated for speeds in excess of 130 mph. Tires & wheels for all vehicles will have metal valve caps (metal valve stems highly recommended) & crack-free valve stems. No tires wider than 10" will be allowed, unless the tires are OEM to the vehicle. (Narrow tires work better on the Salt).
150 MPH Club Rules Tires must be V or Z rated street tires or acceptable racing tires with metal valve caps. (Metal valve stems are highly recommended). Driver must have objective evidence of tire speed rating. No tires wider than 10" will be allowed, unless the tires are OEM to the vehicle. (Narrow tires work better on the Salt).
http://www.roadsters.com/750/ Glynne Bowsher, who had helped Noble with the design of the Thrust 2, was happy to be able to contribute to the new project as the mechanical and structural designer. On a computer, Bowsher used finite element analysis to design the unique aluminum wheels, which had to withstand more than 35,000 Gs. The wheels were forged by HDA Forgings and then machined by Dunlop Aviation, who tested them on a dynamometer at 9,500 rpm.
763.035 miles per hour
[This message has been edited by Gokart Mozart (edited 01-07-2008).]
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12:44 PM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Speed ratings for car tires M 81 mph N 87 mph P 93 mph Q 99 mph R 106 mph S 112 mph T 118 mph U 124 mph H 130 mph V 149 mph When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities. W 168 mph Y 186 mph
http://www.saltflats.com/I30%20Club.html 130 MPH Club Rules Vehicles must have H, V, or Z rated tires which are rated for speeds in excess of 130 mph. Tires & wheels for all vehicles will have metal valve caps (metal valve stems highly recommended) & crack-free valve stems. No tires wider than 10" will be allowed, unless the tires are OEM to the vehicle. (Narrow tires work better on the Salt).
150 MPH Club Rules Tires must be V or Z rated street tires or acceptable racing tires with metal valve caps. (Metal valve stems are highly recommended). Driver must have objective evidence of tire speed rating. No tires wider than 10" will be allowed, unless the tires are OEM to the vehicle. (Narrow tires work better on the Salt).
http://www.roadsters.com/750/ Glynne Bowsher, who had helped Noble with the design of the Thrust 2, was happy to be able to contribute to the new project as the mechanical and structural designer. On a computer, Bowsher used finite element analysis to design the unique aluminum wheels, which had to withstand more than 35,000 Gs. The wheels were forged by HDA Forgings and then machined by Dunlop Aviation, who tested them on a dynamometer at 9,500 rpm.
763.035 miles per hour
Which has nothing to do with the subject at hand, and you still refuse to answer my question.
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03:41 PM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
how's about this: if a plane flys a few feet OVER a teadmill spinning at the same speed as the plane is flying, but in the opposite direction, does the plane suddenly go backwards or crash? of course not - so - how the heck does it affect the takeoff? it doesnt. the wheels are just things to keep the thing from dragging along the ground. they have nothing to do with the take-off - other than to reduce ground friction.
Originally posted by fierobear: Gokart doesn't seem interested in answering, maybe you will...put a helicopter on a treadmill. Will it take off?
Well wait now...
If you had a 100 knot head wind and if you put an airplane on a tread mill with the engine off.. You need to ask yourself one question.... punk. Would it still fly? Well.. would it... Punk?
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05:20 PM
Gokart Mozart Member
Posts: 12143 From: Metro Detroit Registered: Mar 2003
If you had a 100 knot head wind and if you put an airplane on a tread mill with the engine off.. You need to ask yourself one question.... punk. Would it still fly? Well.. would it... Punk?
Replace the tether mast AND ROPE with an engine and propeller, exerting 70ft/lbs of THRUST on the STATIONARY AIR surrounding the plane, and the plane will STILL stand still!!
..as the speed of the plane increases, so does the lift caused by the wings, increasing until the plane finally leaves the ground. The load on the tyres diminishes at an equal rate to the lift of the wings..so the tyres won´t blow or shred either 
...And no, no box full of kittens, nuns, or space saver tires were harmed in the trip that morning. 
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