Warhead data

[ArmySGT.]

Armor value 48 = 2.54cm of Rolled Homogenous Steel. (RHA)

2.54cm = 25.4mm

Penetration for 85mm HEAT-FS is 300mm.

300 divided by 25.4 = 11.81102362

Rounded to 11.811 inches of RHA

11.811 divided by 2.54 = 4.6500093

Rounded to 4.65 doublings from 2.54

AV 48 * (2.54^4.65) = 3661.997299

Rounded to 3662

Efactor for HEAT-FS is 3662.


Nope. Can't be right. I am screwing up the math in figuring how many times a penentration has doubled from the original 2.54 cm.

[ArmySGT.]

Originally Posted by ArmySGT.

Armor value 48 = 2.54cm of Rolled Homogenous Steel. (RHA)

2.54cm = 25.4mm

Penetration for 85mm HEAT-FS is 300mm.

300 divided by 25.4 = 11.81102362

Rounded to 11.811 inches of RHA

11.811 divided by 2.54 = 4.6500093

Rounded to 4.65 doublings from 2.54

AV 48 * (2.54^4.65) = 3661.997299

Rounded to 3662

Efactor for HEAT-FS is 3662.


Nope. Can't be right. I am screwing up the math in figuring how many times a penentration has doubled from the original 2.54 cm.

Armor value 48 = 2.54cm of Rolled Homogenous Steel. (RHA)

2.54cm = 25.4mm

Penetration for 85mm HEAT-FS is 300mm.

300 divided by 10 = 30 centimeters (not inches!)

30 cm divided by 2.54= 11.811023622047244 inches. (Almost a foot!)


Now where I run into a problem. What was doubled and doubled again to reach 11.811023622047244?

Time to stop.

[ArmySGT.]

Originally Posted by ArmySGT.

Armor value 48 = 2.54cm of Rolled Homogenous Steel. (RHA)

2.54cm = 25.4mm

Penetration for 85mm HEAT-FS is 300mm.

300 divided by 25.4 = 11.81102362

Rounded to 11.811 inches of RHA

11.811 divided by 2.54 = 4.6500093

Rounded to 4.65 doublings from 2.54

AV 48 * (2.54^4.65) = 3661.997299

Rounded to 3662

Efactor for HEAT-FS is 3662.


Nope. Can't be right. I am screwing up the math in figuring how many times a penentration has doubled from the original 2.54 cm.

300mm = 30 cm

2.54 ^ 3.64 = 29.75738257

29.75738257 = 1428.354364

E-factor = 1428

Better?

[robj3]

85mm HVAP-T
Armor Penetration (mm):
180mm (RHA) at 1,000 meters E-Factor =
113mm (RHA, 30°) at 500 meters E-Factor =

AV 48 = 25.4mm RHA.
For each x2 in armor thickness, x2.5 AV

180mm = 2.82 doublings. E-factor = 48 * (2.5^2.82) = 636
113mm = 2.15 doublings. E-factor = 48 * (2.5^2.15) = 344

HEAT-FS
300mm = 3.56 doublings. E-factor = 48 * (2.5^3.56) = 1253

AP-HE
90mm = 1.82 doublings. E-factor = 48 * (2.5^1.82) = 254


Another way of looking at:
"For each x2 in armor thickness, x2.5 AV"

is

Armor thickness varies with 2^(a)

Final armor value = 48*(2.5^(a))

So 180/25.4 is about 7.09, which is 2^(2.82).

Using the scientific calculator in Windows:
- Take the log of 7.09 (~0.851)
- Store in memory
- Take the log of 2 (~0.301)
- divide by what's in memory
- take the reciprocal (1/x) (~2.82)
- use this answer to find AV/E-factor (48*[2.5^2.82])

It's roundabout but accurate...

Rob

[ArmySGT.]

Thank you for your reply Rob3j!

Hopelessly over my head here though. It has been too long since I have had to do something like this.

Thank you again!

[robj3]

Sorry, I wasn't sure how active the forum is.
Should have checked back in sooner.
Consolidating the previous math:

E-factor/AV = 48 * 2.5^[3.322(log(mm RHA) - 1.4049)]

3.322 ~= 1/log(2)
1.4049 ~= log(25.4)

Checking , the formula returns slightly different values thanks to rounding:
300mm = 1255
90mm = 255
113mm = 345
180mm = 639

sub 1% differences are OK, I think.


Rob

[ArmySGT.]

Originally Posted by robj3

E-factor/AV = 48 * 2.5^[3.322(log(mm RHA) - 1.4049)]

Rob

Thanks Rob!

I am going to go forward using this formula to make stats for some Soviet, Canadian, and Mexican systems as well as some updates for US and project equipment.

This is a huge help! Thanks again.

Stay tuned folks.

[ArmySGT.]

Armbrust.


SYSTEM
Alternative Designations: Crossbow
Date of Introduction: INA
Proliferation: At least seven countries
Description:
Crew: 1
Caliber (mm): 67
Weight (kg): 6.3
Length (mm): 850
Rifling: None
Breech Mechanism Type: N/A
Rate of Fire (rd/min): N/A (disposable)
Fire From Inside Building: Yes (see NOTES)
SIGHTS
Name: N/A
Type: Reflex
Magnification: None
Location: Left side
Sighting Range (m): INA
Night Sights Available: INA
VARIANTS (INA)
AMMUNITION
Name: INA
Type: HEAT
Range (m):
Maximum: 1,500
Effective AT: 300
Flight Time (sec) @ 300 m: 1.5
Penetration:
Armor (mm): 300
Reinforced Concrete (m): INA
Muzzle Velocity(m/s): 210

E-factor 1255

Projectile mass: 1.0 kg
Filler: RDX, 0.16 kg
Using weapon(s): ARMBRUST antitank weapon
Remarks: None


Name Armbrust (updated)
Cal. 67mm
E-Factor = 1255 48 * 2.5^[3.322(log(300) - 1.4049)] = 1255.079738
DPW = 451 ((0.16 / 0.563) x 1300) x 1.22 = 450.7282416
Wt. (Empty) 6.3 kg
Min. Range 50m
Eff. Range 350m
Max. Range 1500m
Burst Radius 5m
Type of Fire Single shot disposable
Rate of Fire Single
Feed Device n/a
Feed Device Wt. n/a
Basic Load 2
Load Wt. 12.6 kg
Total Wt.
Additional Comments: A disposable, flashless, noiseless, recoilless gun firing a high explosive shell. The shell will penetrat 30 centimeters (300mm) or steel. The "backblast" from the weapon is made up of plastic flakes and is so short the firer can stand with a wall only 1 meter behind him.

Found in Load out: #17

[nuke11]

Originally Posted by robj3

Sorry, I wasn't sure how active the forum is.
Should have checked back in sooner.
Consolidating the previous math:

E-factor/AV = 48 * 2.5^[3.322(log(mm RHA) - 1.4049)]

3.322 ~= 1/log(2)
1.4049 ~= log(25.4)

Checking , the formula returns slightly different values thanks to rounding:
300mm = 1255
90mm = 255
113mm = 345
180mm = 639

sub 1% differences are OK, I think.


Rob

Has anyone converted this formula to an Excel formula yet?

[ArmySGT.]

Originally Posted by nuke11

Has anyone converted this formula to an Excel formula yet?

I have not. I am not sure of how to insert a logarithm into the equation.