Length of paw 1000

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David Hume
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Posts: 19
Joined: 20 Apr 2020, 04:58
Location: Los Angeles

Length of paw 1000

#1

Post by David Hume » 20 Apr 2020, 23:24

In some graphs by Hilary Doyle, the paw 1000 seems at least 4m, as compared to the chasis of 38d.
Image
Image

However, from several sources the length of paw 1000 is 2.4m.
http://www.lexikon-der-wehrmacht.de/Waf ... onen-R.htm
"Bei Krupp wurde die 10-cm Panzerabwehr-Wurf-Kanone 10 H 64 entwickelt, welche mit dem System des "übergroßen Ladungsraumes" arbeitete. Ein Expansionsraum war konzentrisch um den Ladungsraum angeordnet und mit diesem durch zahlreiche Öffnungen verbunden. Die Treibladung wurde dabei als Ringkartusche um den Schaft der Wurfgranate gelegt. Diese Waffen hatten zwar Schußweiten von fast 5.000 m, bei einem Trefferbild von 1,5 x 1,5 m auf 1.000 m war diese Entfernung jedoch die maximalste zur Panzerbekämpfung. Die 900 kg schweren Waffen hatten ein 2.400 mm langes Rohr, aus dem eine 6,6 kg schwere Wurfgranate verschossen wurde. Diese konnte auf 1.000 m bis zu 200 mm Panzerung durchschlagen."

http://beyondthesprues.com/Forum/index. ... ic=3442.15
show the photo Image from which it seems 2.4m is reasonable. These photo looks similar to the "Krupp mock-up" from Ian Hogg's German_Artillery_of_World_War_Two.

https://en.topwar.ru/131537-protivotank ... aniya.html
http://alternathistory.com/8-sm-protivo ... r-germani/
These two sources mentioned the muzzle velocity for the 6.6 kg projectile is increased to 600 m/s from 520 m/s of paw 600. The pressure is 2100/700 as compare to 1200/550.

The length of of paw 600 is 3m. 10.5cm lefh 18 is aslo 3m, and the muzzle velocity is only 470m/s. And 7.5cm FK 38 is 2.55m, muzzle velocity 607m/s for a 6.3 kg projectile. The pressure in the barrel of the later two should be much more than paw 1000. This makes me suspicious if the low pressure in a 2.4m barrel can give a 6.6 kg projectile a 600m/s velocity.

On the other hand, to improve the effective range, the higher velocity seems necessary.

Do you think if Doyle just made a mistake, or paw 1000 should be longer than 2.4m?

By the way, lexikon-der-wehrmacht.de says the weight is 900 kg, while multiple sources including wikipedia says 1035 kg. This seem too large to be the difference from combat and total weight.

David Hume
Member
Posts: 19
Joined: 20 Apr 2020, 04:58
Location: Los Angeles

Re: Length of paw 1000

#2

Post by David Hume » 21 Apr 2020, 00:33

Actually, a simple calculation will show there is something wrong.

Assume the pressure in the barrel is indeed 700 kg/cm^2 for the whole duration. This actually overestimates, as the pressure will decrease while the projectile is moving forward.
The area of the cross section is A=3.14*(10.5/2)^2=86.54625 cm^2
the force pushing the projectile is F=700*9.8 A=593707.275 N
the total work W=2.4 F=1424897.46 J
this should equal the kinetic energy of the 6.6 kg projectile
E=mv^2/2=6.6*600^2/2=1188000 J
this is 83.4% of the total work, which seems too high an efficiency.

In comparison, for paw 600
E=2.7/2*520^2= 365040 J
W=3*550*(8.14/2)^2*3.14*9.8=841062J
E/W=43.4%

It's unlikely the efficiency increased by two in this case. Hence either:
1, the projectile is much lighter than 6.6 kg. But (1050/814)^3=2.15, and 2.15*2.7=5.8, ratio is only 0.88, which seems reasonable. In comparison, the shell of 105 mortar is 7.38 kg, and for 81 mortar it is 3.5 kg. 3.5*2.15=7.525, ratio 1.02. So the weight shouldn't be too low.

2, the pressure is much higher. In order to explain the high efficiency the pressure need to double, which is more than the high pressure of 1200 for paw 600, which seems unlikely. (Can any one inform me the pressure inside barrel for a ww2 gun?)

3, the length has to increase to about 2. This would be much closer to the drawings of Doyle.


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