Tire Stress for Heavy Bombers

[gruad]

There are many stories of Tyres bursting on take off and landing which would be catastrophic putting the bomber into a violent spin on the runway.

On take off the tyre is under pressure to support the load.

Did ground crews super inflate the tyres like on a car to deal with heavy loads and stay round?

There's also the centrifugal force trying to rip the spinning tyre off. It should be easy enough to calculate take off rpm for say a Lancaster.

I have been told the tyres got hot which deformed the ideal structure although in terms of physics I can't see how this works if someone could help.

On landing the spin up will place a huge stress on the tyre. I was thinking a vane in the wheel hub could spin up the wheel to the required speed but no one has adopted that presumably because of weight and complexity issues.

Once you get thinking about it flying is damn difficult!

 

[bf109xxl]

There's also the centrifugal force trying to rip the spinning tyre off. It should be easy enough to calculate take off rpm for say a Lancaster.

f = V/(2*Pi*r), V - speed, r - tyre radius, you may need to convert speed or radius values using appropriate units. For the Lanc, f ~700-730. Not very impressive comparing to the modern jets.

 

[bf109xxl]

Once you get thinking about it flying is damn difficult!

Here's a book that explains everything about aircraft tires in the simplest terms:

 

[EwenS]

There are many stories of Tyres bursting on take off and landing which would be catastrophic putting the bomber into a violent spin on the runway.

On take off the tyre is under pressure to support the load.

Did ground crews super inflate the tyres like on a car to deal with heavy loads and stay round?

There's also the centrifugal force trying to rip the spinning tyre off. It should be easy enough to calculate take off rpm for say a Lancaster.

I have been told the tyres got hot which deformed the ideal structure although in terms of physics I can't see how this works if someone could help.

On landing the spin up will place a huge stress on the tyre. I was thinking a vane in the wheel hub could spin up the wheel to the required speed but no one has adopted that presumably because of weight and complexity issues.

Once you get thinking about it flying is damn difficult!

There is also the issue of the surface that the bomber is flying on. I read recently (can't remember where now) that when bombers moved from grass surfaces to hard concrete runways it was possible to increase the tyre pressures. Lower pressures were required for grass fields, some of which existed until well into WW2. Scampton, for example, only got concrete runways between Aug 1943 and Oct 1944. New airfields in Britain were being built with hard runways starting from the 1938-40 period.

 

[z42]

There's BTW a recent interesting video about rubber (flashback to studying polymer physics in uni, but I digress..), where it was mentioned that aircraft tyres are one of the applications where natural rubber can't be substituted by synthetic rubber (which is fine for automotive tires).


View: https://m.youtube.com/watch?v=AFXLZ7FEJc4&pp=ygUKdmVyaXRhc2l1bQ%3D%3D

 

[GregP]

There are many stories of Tyres bursting on take off and landing which would be catastrophic putting the bomber into a violent spin on the runway.

On take off the tyre is under pressure to support the load.

Did ground crews super inflate the tyres like on a car to deal with heavy loads and stay round?

There's also the centrifugal force trying to rip the spinning tyre off. It should be easy enough to calculate take off rpm for say a Lancaster.

I have been told the tyres got hot which deformed the ideal structure although in terms of physics I can't see how this works if someone could help.

On landing the spin up will place a huge stress on the tyre. I was thinking a vane in the wheel hub could spin up the wheel to the required speed but no one has adopted that presumably because of weight and complexity issues.

Once you get thinking about it flying is damn difficult!

MUCH easier to change tires than to replace wheel bearings!

With tires, only the wheel and tire have to come off. ALso, overspeeding the wheels could have a detrimental effect on drum brakes (as they generally should have used brakes to stop the wheel before retracting the gear) as well as heating up any disc brakes that may or may not have been used in WWII.

 

[gruad]

There's BTW a recent interesting video about rubber (flashback to studying polymer physics in uni, but I digress..), where it was mentioned that aircraft tyres are one of the applications where natural rubber can't be substituted by synthetic rubber (which is fine for automotive tires).


View: https://m.youtube.com/watch?v=AFXLZ7FEJc4&pp=ygUKdmVyaXRhc2l1bQ%3D%3D

Wow!

Just watched the video. 70% synthetic but not for aircraft because synthetic can't work the temperature ranges cold temperatures in the atmosphere to heat in speed up on landing where the tyres smoke.

Here's my solution. Tyre heaters and a turbine like structure on the wheel to speed up the tyre before touchdown. Somebody talk me down please!

 

[EwenS]

Here's my solution. Tyre heaters and a turbine like structure on the wheel to speed up the tyre before touchdown. Somebody talk me down please!

Well the last of your ideas was used on the nose gear of the Vought F7U-3 Cutlass in the 1950s.

"Vought engineers, concerned about the kickback load on the nose landing gear actuator and mounting structure, added small turbines, powered by engine bleed air, to pre-spin tire on the nosegear tires to 90 mph. But the nosegear strut continued to fail, despite efforts to reinforce the structure by 30 percent. A weak drag link brace tended to give out during landing."

In the early jet age, pilots had good reason to fear the F7U

The Gutless Cutlass.

www.smithsonianmag.com

 

[bf109xxl]

Here's my solution. Tyre heaters and a turbine like structure on the wheel to speed up the tyre before touchdown. Somebody talk me down please!

It has already been tested on at least two types of aircraft. For many reasons, this solution is not suitable - too heavy, too unreliable, and, perhaps, too expensive.

 

[gruad]

Well the last of your ideas was used on the nose gear of the Vought F7U-3 Cutlass in the 1950s.

"Vought engineers, concerned about the kickback load on the nose landing gear actuator and mounting structure, added small turbines, powered by engine bleed air, to pre-spin tire on the nosegear tires to 90 mph. But the nosegear strut continued to fail, despite efforts to reinforce the structure by 30 percent. A weak drag link brace tended to give out during landing."

https://www.smithsonianmag.com/air-...ss-cutlass-12023991/[/URLGreat minds etc etc!

Thank you! Great Minds etc etc Thought this was going to be dismissed as Heath Robinson!

 

[gruad]

It has already been tested on at least two types of aircraft. For many reasons, this solution is not suitable - too heavy, too unreliable, and, perhaps, too expensive.

In the rubber video they were saying existential threat to air travel if the rubber fungus wiped out far east rubber... So I guess solution might be viable if that happens - praying it does not though!

 

[GregP]

Here's a video about why that idea isn't practical.


View: https://youtu.be/Jm6hOnsxy3M

 

[bf109xxl]

A radical solution:

PS. It was just a joke.

 

[bf109xxl]

In the rubber video

I do not consider YouTube to be a reliable source of information and I do not recommend it to you.

 

[wozza]

A quick comment [ from memory ] I have it in a book somewhere that B24s [ and B17s ? ] were having the tyres changed after 6 landings -- in the Australia / New Guinea area because of the rough nature of the South Pacific airstrips . That also the P47s wheels were spun [ cannot remember how ] before landing [ Pacific area again ] . If you look at pictures of burst a/c tyres [ ww2 era ] you can see that for the most part the rims are still intact and undamaged -- which suggest to me that aircraft tyre design back then kept the flat tire and tube fairly intact to run on and save the rim . Nowadays [ vis Concorde crash ] , a/c tires seem to be designed to break up into small pieces .

 

[pinehilljoe]

I remember reading during the XB-36 development, the main tires took a considerable amount of engineering work.
"existing brake designs meant a 65-inch tire tread in a four-wheel arrangement, and this could not be housed in the wing. Consequently, work proceeded on the single wheel design, with Goodyear Tire and Rubber Co. as the subcontractor. The 110-inch diameter by 46-inch wheel was, and still is, the largest airplane tire ever developed, weighing 1475 lbs. by itself" Quoted from Wings/Airpower magazine. Eventually a 4 wheel configuration was developed.

 

[GrauGeist]

The Douglas B-19's main gear tires were 24-ply and measured 8 feet (2.4m) in diameter.

This also points out a key point about a bomber's tires: the layers of belts in the tire's casing.

The more the plies (or layers of belting) in the tire's construction, the more weight and resistance to heat the tire can handle.

 

[EwenS]

AIUI the problem with the original single large wheel main undercarriage units was two fold:-
1. Weight. The entire wheel unit (tyre, inner tube, wheel, triple-disc brake assembly) weighed 8,550lb
2. Fitted with that single wheel, there were only 3 airfields in the world capable of supporting the XB-36. A runway needed to be constructed with a concrete surface 22in thick to support it. Those runways were all in the USA (Fort Worth, the site of the factory building them, Eglin Field Florida and Fairfield-Suisun in California.

So really there was no option than to come up with something better, even if it did mean bulges on the upper wing and the wheel doors to accommodate the new 4 wheel bogies. The new design saved 2,600lb over the original. And it spread the aircraft weight over a greater surface area allowing it to use many more airfields.

They even tried a tracked bogie unit to spread the weight further. All it did was spread itself along the runway!

Key Publishing "Convair B-36 Peacemaker"

And from Joe Baugher's old site.
"The first XB-36 (42-13570) was rolled out of the Fort Worth factory on September 8, 1945. It sat on massive single 110-inch diameter main wheels, which restricted it to only three runways in the USA which had sufficiently thick concrete to support the weight of the aircraft. "

"In June of 1948, the single-wheel main undercarriage was replaced by a four-wheel bogie-type undercarriage, which was to be standard on production models. Each wheel had a 56 inch diameter. This reduced the runway thickness requirements. In addition, 3500 hp R-43660-41 engines were fitted. The plane was then redesignated YB-36A. It was reflown in this configuration in June of 1948. The original single-wheellanding gear tire is on display at the USAF Museum in Dayton, Ohio."

Convair XB-36 Peacemaker

It is nearly 35 years since I visited Dayton, but the size of the B-36, and its tyre, still stick in the mind. Standing under it gives true meaning to the phrase "aluminium overcast"!

 

[Thumpalumpacus]

It is nearly 35 years since I visited Dayton, but the size of the B-36, and its tyre, still stick in the mind. Standing under it gives true meaning to the phrase "aluminium overcast"!

When I was in tech school at Chanute AFB, my gal and I would have a picnic under the wing of the static -36 they had. Freakin' amazing.