Allied/Axis Bomb-Shapes

[tyrodtom]

No we were still using WW2 munitions, partly at NKP, Thailand.
We operated only prop jobs, A1, AT-28, A 26, O-2, etc.
I remember one in particular, a British 500 lbs thermite cluster bomb, I think M-47,or MK-47, we had a lot of problems with it after it had been in storage somewhere for over 20 years.
That same M-47 designated some other bomb types too

 

[alsaad]

Highly recomend following titles:

Wolfgang Fleischer- German Air-Dropped Weapons to 1945

John A. MacBean and 2 more - Bombs Gone: Development and Use of British Air-dropped Weapons from 1912 to Present Day

Castle and Bromwich - Story of Ordnance

Arthur Hariss - War dispatches

There you will find a lot on development and use of the aerial bombs. There are several more titles like col. Meriman - Italian Bombs and Fuzes and few on Soviet bombs which can put some light on the topic.

 

[alsaad]

The British Medium Capacity bomb body shape was inspired by the Luftwaffe SC (Sprengbombe Cylindrisch) but the tail design remained much the same as the older GP bombs. The GP bomb shape was very good aerodynamically and when Jets came along the bomb shapes reverted to the GP style though with much thinner higher quality steel walls to keep explosive capacity high

British MC design was inspired by both German SC and US GP design. Actually, British GP design was among the poorest bomb designs at the beginning of the WWII. Quality of British steel prior to WWII was lower than US and German forcing British bomb designers to increase bomb casing thickness and decrease charge weight. That is why British bombs performed worse than German. That was the reason for the development of MC series which corresponds with SC and US GP designs.

 

[Brooke]

With the accuracy of bomb aiming from 25,000 feet I think most of the aerodynamics was concerned with making sure the bomb exploded when it hit.

This is the elephant in the room. Horizontal iron bombs are very inaccurate. The Navy developed the Norden bombsight and after testing it went to dive bombing. The Army picked it up but when they tried to do "precision bombing" it was a failure and "carpet bombing" was the outcome.
Gyroscopes
Aircraft
TED: Malcolm Gladwell: The strange tale of the Norden bombsight

 

[BAGTIC]

Some of the German bombs were stored in the bomb bay vertically (H-111, maybe others too), fins down, so that fact might have had something to do with the size of the fins on German bombs.

I have often wondered why some German bombs were stored vertically tail down. As a child I was intrigued by videos of them doing their flip.

Did this have any effects on accuracy versus a horizontal drop?

 

[alsaad]

Part of the answer is in the fact that all German bombs larger than 50 kg had transversal electrical fuzes rather than mechanical nose/tail setup. In such design it was much easier to provide arming installations in the bomb bay for the bombs in vertical position. The other part of answer is fact that German bombers could receive more bombs in there bomb bays vertically than horizontally. For the same reason Italians were hanging their bombs vertically in some bombers.

 

[tomo pauk]

...
The other part of answer is fact that German bombers could receive more bombs in there bomb bays vertically than horizontally.
...

IIRC only the He 111 was able to carry bombs in vertical position, 8 x 250kg.
Do-217 carried up to 3 tons of bombs, all in horizontal position.

 

[Shortround6]

I believe the HE 111 could carry 110lb bombs (50Kg) in the vertical cells, four per cell that carried a single 250kg bomb.

 

[fastmongrel]

British MC design was inspired by both German SC and US GP design. Actually, British GP design was among the poorest bomb designs at the beginning of the WWII. Quality of British steel prior to WWII was lower than US and German forcing British bomb designers to increase bomb casing thickness and decrease charge weight. That is why British bombs performed worse than German. That was the reason for the development of MC series which corresponds with SC and US GP designs.

There was nothing wrong with the steel but the low filling weight was down to the fact that the bombs were cast steel rather than the German SC bombs which were forged and rolled. The design of the later MC bomb probably owes virtually everything to the SC after all there were plenty of them to study they were falling out of the sky for free, whereas a US GP bomb would have to be imported for hard cash before 1942.

There was a problem with bad fuses on the GP bombs caused by the mad rush to ramp up production in 1940/41. Fuses are a precision manufacturing job not something you can easily farm out to an inexperienced company.

The aerodynamics of the GP were very good for external carry but explosive weight counts for more in wartime than fuel savings.

 

[alsaad]

British forging technology prior to WW2 could not produce casing strong enough so they were forced to produce casings by casting and make them thick. Later that technology improved due to some American "know how" and British could produce thinner casings that were strong enough not to break upon impact. The other thing is that prior to WW2 in Britain there was literally no live bomb drop tests but structural strength of the bombs was tested by firing bombs from some kind of gun to concrete obstacles while explosion effects were tested by static bomb detonation. Only aerodynamics was tested by dropping the dummy bomb. The results were bombs with the poorest terminal effect at the beginning of the War. Very important thing is that drop like shape of the British GP series, even very aerodynamic, leaves smaller explosive cavity than cylindrical SC/US GP bombs shape.

 

[alsaad]

And regarding the fuses... if you look into British No 28 or No 30 tail pistol you will notice that they were functioning same way as US AN M100/101/102 fuse...and mostly every inertia operated tail fuse...which was quite satisfactory. Problem with British fuses generally was not malfunction upon impact but short arming time and vertical safety due to no arming gear mechanism which was present on US fuses. Short arming time sometimes caused bombs to detonate in mid air after colliding with each other too close to the aircraft which dropped them and to destroy or damage it. For example on US fuses vanes had to make no less than 158 revolutions to arm the fuse (except on fuses for low level bombing) while on British fuses arming process was completed after 7-11 revolutions.

 

[Shortround6]

The British seem to have had a "thing" for cheap ammo and it also seems that some of the lessons of WW I had been forgotten.

see, Shell Crisis of 1915 - Wikipedia

for just part of it.

The follow up part was that scores of guns (if not hundreds) were wrecked and scores of gunners killed/wounded when the hastily built substitute standard shells were used at the front and prematures began to happen (shell explodes in the bore of the gun or just in front of the muzzle).

Part of the "solution" between the wars seems to have been a deliberate policy of designing ammunition that could be built using low grade steel and still have a decent safety margin.
The 'trap" with this solution is that you need more shells to get the same target effect if the desired effect was destruction of earth works or buildings. A British 25pdr shell carried less explosive than an American 75mm shell of less that 15lbs.

The British for example were still fooling around with a cast iron projectile for the 25pdr gun half way through 1944. after years of effort and numerous trials where the projectiles (or at least a certain percentage) simply disintegrated after leaving the muzzle due to centrifugal force. Cast Iron may work for mortar shells (no rotational forces) and the British may have learned quite a bit about cast iron in high stress situations but it had zero effect on the artillery war.

This may have carried over to the aircraft bombs. Or the price they were willing to spend for them.

 

[alsaad]

The British after WWI ended reduced investment into the explosive ordnance development. Due to such policy at some point during late 1930s they just could not keep up with Germans which ordnance designs at the time were among the best globally. Fortunately on some other fields British were in front of Germans significantly.

 

[fastmongrel]

British forging technology prior to WW2 could not produce casing strong enough so they were forced to produce casings by casting and make them thick. Later that technology improved due to some American "know how"

The casting method of production and the cheap low grade Steel were chosen for cost reasons not because the forging method was faulty. Forging and or rolling a shape like a bomb casing was well known technology by the 20th Century. After all if virtually every foundry in Europe could do it in WWI why would they suddenly lose the knowledge.

 

[alsaad]

Drop like shape chosen by British was much easier do cast than to forge, that might be a part of the answer too. However British were on the wrong path of the development as they admitted by themselves. On the other side 500lbs GB bomb with 531.334 pieces expended by the Bomber Command was the most used bomb from the British inventory. Still in the 1000lbs category MC with 253.800 pieces expended is far in front of GP with 82.164 pieces dropped.

 

[Reluctant Poster]

The British after WWI ended reduced investment into the explosive ordnance development. Due to such policy at some point during late 1930s they just could not keep up with Germans which ordnance designs at the time were among the best globally. Fortunately on some other fields British were in front of Germans significantly.

Britain did make significant advances in explosives, in particular their development of RDX.

 

[alsaad]

RDX, cyclonite or hexogen is invented in Germany. British took part in the invention of the method for desensitising RDX by mixing it with small amount of wax. Germans did it by mixing RDX with graphite. British actually invented Torpex (Torpedo explosive) which was mixture of RDX, TNT and aluminum powder and about 50% more brisant than TNT, but that explosive was not in use prior to mid 1942. It was used in MC bombs 500-4000lbs, HC 4000 lbs and both DP bombs. US version of RDX based mixture was Comp B present in some number of US GP bombs. Germans in their bombs used Trialen which had only about 15% of RDX.

 

[Zipper730]

"In 1921 the War Department convened a Bomb Board to conduct an extensive program for testing bombs against various kinds of structures and surfaces. The tests, running over a period of two years, provided data that guided the Ordnance Department and the Air Corps through the 1930s, Ordnance engineers strengthened demolition bomb cases by forging them as nearly as possible in one piece, with a minimum of welding, and substituted for the long fins of World War I short box fins that gave greater stability in flight"

So the box-fins came out of this period of time?

 

[Zipper730]

I read the article, and will post some questions and stuff later, provided I remember.

 

[Niceoldguy58]

I was very recently reading some USAAC documents on tests in the late 1930's of round bomb "fins" -which the Air Corps had been using since WWI - vs the box fin. The AAC's findings were that the box fin made the bombs more stable and allowed for greater accuracy, a very important aspect to the Air Corps and its daylight bombing philosophy.

Thus the box fins.

AlanG