# German hammer

HAS ANYONE SEEN A REAL SHELL FOR THE LATE WAR GERMAN EXPERIMENTAL A.T. WEAPON - THE HAMMER ? HOW ABOUT A GOOD PHOTO OF ONE ?

A SIMILAR JAPANESE WEAPON.

I HAVE THE MANUAL BUT THE IMAGES OF THE AMMO ARE NOT VERY GOOD.

CSAEOD,

Dave

This was officially the Panzerwurfkanone 8H63 produced by Rheinmetall. According to the book “Anti-tank Weapons” by Terry Gander, rather then a recoilless effect, it operated on the “hi-lo” principle as currently used in the various 40mm grenade launchers–on a much bigger scale.

First fielded in December 1944, apparently few made it to the front.

Wendigo

Please excuse my ignorance but what is the “hi-lo” principle? High impact-low velocity?

The High-Low pressure principle uses the basic laws of gases, Boyle’s Law, in that under constant temperasture, the pressure of a (confined) gas is directly related to its volume. Mathematically written, P1V1 = P2V2 ( or more into physics, PV= Constant.

So if you get a small capacity Charge in a small volume, producing a high pressure, when the gas enters a high volume chamber, the pressure drops in accordance with Boyle’s law ( of the early 1800s).

Mortars and Cartridge grenade launchers (such as the M79) work on this principle.

The volume inside the blank propellant cartridge is small, and the gas generated is high poressure; the gas flows out into the larger chamber under the grenade (or Mortar Bomb, asnd so the pressure drops, giving the Payload a gentle “Push” onto its target. (also because the grenade/Bomb is much heavier.)

If you look at a fired M79 GL shell casing, you will see a dome in the bottom with three or four radially spaced side holes. THis the the “Hi” chamber where a .38 cal blank is discharged. The gas then leaks out of the small holes to the larger volume under the grenade, and the pressure, much lower, pushes the grenade loose from its silicone rubber seal ring, and onto the target. (“Fumpah!”

The Mortar Bomb works in much the same manner. The shotshell blank in the tailpipe is discharged, and the paper shell case is penetrated at the gas relief ports in the steel tube. The powder has all burnt, as the pressure required to breach the paper is quite high. The gas then expands into the larger volume between the tail fins and the Bomb major diameter, and “pushes” the bomb on its way.

If you wish to increase the range, one adds extra charges around the Main tail tube of the bomb, to be ignited by the primary charge, and produce More gas for the same volume, hence increasing the pressure.

One problem, when the Tube (Mortar Barrel) gets too hot, the gases of discharge can also “cook off” the main charge.
That is what probably almost killed Mussolini during a training exercise in 1917. That is because Pressure is also related to Temperature as well as Volume ( “PV= nRT” where “n” is a Constant, and R is a factor related to the gas’s nature. )

HI-Lo is an interesting application of a Physical law of the performance of gases discovered some 200 years before the general use of the “Stokes Mortar”.

regards,
Doc AV
AV Ballistics.

Thanks Doc

Doc,why do you consider “n” as a costant?
It should be a constant only for the specific case

in pratica:
perch

I’ve been taught “k” for constant.
But now I’m really off topic

While I admit to being technically challanged and find myself confused by Roadrunner cartoons, I guess I can’t see the weapon pictured as being a high-low pressure, sealed breach device. I don’t see what would constitute a breach for one thing and to generate any useful ballistics with a projectile the size that would likely come out of a tube that large in diameter, I would think that the recoil would be a problem. The dude sitting behind the buggy wheel carriage sighting the device would be in harms way even if the wheel did tend to roll over him…

Recoilless gun or rocket launcher (fast burn type as no blast shield is noted?) would be my guess.

Dave

Rocket launchers work according the third dynamic principle action-reaction if there isn’t a breech

I am not a rocket scientist (no pun intended)…but we can all agree by glancing at the photos provided…that “recoil” is apparently not an issue with either weapon…thus…I am hard pressed to assume the breech is closed on either weapon…right ?

also please remember the ‘shotgun shell’ ignites the increments of propelling powder clipped to the tail fins on some weapons–U.S. 81 and 60 mm.

[quote=“Wendigo”]This was officially the Panzerwurfkanone 8H63 produced by Rheinmetall. According to the book “Anti-tank Weapons” by Terry Gander, rather then a recoilless effect, it operated on the “hi-lo” principle as currently used in the various 40mm grenade launchers–on a much bigger scale.

First fielded in December 1944, apparently few made it to the front.

Wendigo[/quote]

GANDER HAS USED THIS INFO IN A COUPLE OF PUBLICATIONS USUALLY WITH THE NOTICE " the data below should be regarded as provisional. ".

Here is info about how it works and the shell from the manual. Not a very clear photo but what there is so far.

This weapon followed the same development scheme as the Panzerfaust and later the RPGs. of similar design . Once a propelling charge was added to the projectile to carry it farther it became a different animal.

One can clearly see from the image of the projectile for this weapon that there is no onboard propelling charge.

IT IS NOT A HIGH/LOW PRESSURE WEAPON. IT IS A HIGH AND GOODBYE DESIGN.

The weapon is an open tube. The charge burns in the tube throwing a blast jet out the rear and the projectile out the front. This design is far more "recoiless’ than the “recoiless” guns which have a closed breach and bleed off the charge.

Anyone who has stood near one of these guns or even seen them fired know that they are REDUCED RECOIL weapons NOT RECOILESS.

The Japanese version shown is a rocket launcher of conventional type. The projectile is a rocket AND A REAL RARE ONE.

[quote=“DaveE.”]While I admit to being technically challanged and find myself confused by Roadrunner cartoons, I guess I can’t see the weapon pictured as being a high-low pressure, sealed breach device. I don’t see what would constitute a breach for one thing and to generate any useful ballistics with a projectile the size that would likely come out of a tube that large in diameter, I would think that the recoil would be a problem. The dude sitting behind the buggy wheel carriage sighting the device would be in harms way even if the wheel did tend to roll over him…

Recoilless gun or rocket launcher (fast burn type as no blast shield is noted?) would be my guess.

Dave[/quote]

In this design the entire propelling charge is consumed in the firing with a flame jet exiting the rear. There is no flash in front as with a rocket launcher.

Other German designs tuned the gas jet to allow for more range and heavier projectiles.

The manual for this guns shows the measured upward movement at firing and it is very little.

Considering the igniter cartridge in a typical mortar as “high-low” principle is a bit of a stretch.

The holes in the tail boom are designed to fire the propelling charge as evenly as possible and have little else to do with propulsion.

A cartridge with sufficient power to blow a mortar bomb out of the tube through the tail boom holes would produce dangerously high pressure.

A mortar bomb is thrown by relatively slow burning and lower pressure attached charges rather than the igniter cartridge.

Considering the igniter cartridge in a typical mortar as “high-low” principle is a bit of a stretch.

The holes in the tail boom are designed to fire the propelling charge as evenly as possible and have little else to do with propulsion.

A cartridge with sufficient power to blow a mortar bomb out of the tube through the tail boom holes would produce dangerously high pressure.

A mortar bomb is thrown by relatively slow burning and lower pressure attached charges rather than the igniter cartridge.[/quote]

The British 2 inch mortar used only the 28-bore cartridge inside the tail tube to launch the bomb, no secondary charges.

gravelbelly

Yes , these minimortars play by different rules. The 2 inch British and the Japanese “knee mortar” ,both trigger fired weapons, are considered by many to be grenade throwers rather than typical mortars. Both fire fixed shells.

The British shell is a nontypical design which is more a cylindrical grenade than a mortar bomb. The British shell uses a high pressure propelling cartridge of shotshell design.

The Japanese shells include a typical hand grenade with a propelling device screwed into the base and the famous fixed version.