Estimate:
| Caliber | mm | |
| Mass | kg | |
| Velocity | m/s | |
| Penetration | mm |
Reference (DeMarre only):
| Caliber | mm | |
| Mass | kg | |
| Velocity | m/s | |
| Penetration | mm |
I'm not sure what it is but there is some problem with the right side (DeMarre) Penetration result. You have to enter a value there and then one pops into the left side (Krupp) Penetration. This is confusing.
ReplyDelete-m
That's intentional, but I can see how that would be confusing. I'll get around to changing it.
Deletewhat value do i put in for the DeMarre Penetration result
DeleteThe reference penetration value. Here's an example: http://tankarchives.blogspot.com/2014/10/penetration-equations.html
DeleteAt what range and angle the penetration value is given?
ReplyDeleteIs it point blank, i.e. 0 meters @ 90 degree?
Thanks.
Depends on what range the shell achieves that velocity at. Penetration for Krupp is 90 degrees, penetration for DeMarre is at whatever your reference angle is.
DeleteHow do you know what your reference angle is?
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ReplyDeleteThis comment has been removed by the author.
ReplyDeleteYour calculator isn't working properly. When you try to get the results for the DeMarre calculation it gives you a result of "NaN"
ReplyDeleteIt's working for me. Make sure to fill out all the fields in the Reference section and all fields in the Estimate section except Penetration. If it still doesn't work, post your browser and console output.
DeleteThe DeMarre calculator doesn't work.
ReplyDeleteFilled out the conditions for Calibre, Mass and Velocity but when clicking the Calculate (DeMarre) button it just gives a NaN message in the Top penetration calculator.
You need to enter reference values in the lower set of boxes if you want the DeMarre calculation.
DeleteThanks it's working now
DeleteCan you post the DeMarre equation. I can't find it anywhere
ReplyDeletehttp://tankarchives.blogspot.com/2014/10/penetration-equations.html
DeleteThanks!
DeleteI might not be entering the values correctly, but I am finding it very difficult to get 150mm of penetration with a 77mm shell like the 17 pounder was historically capable off.
ReplyDeleteThe Krupp method does give values that are too low, but I plugged in British data for the 6-pounder (2.7 kg shell, 900 m/s muzzle velocity, 101 mm of penetration) and got 152 mm of penetration for the 17-pdr.
DeleteMaybe because the 17 pounder is a 76.2mm gun, and not a 77mm.
DeleteMy Experiments.
ReplyDeleteFor HMG rounds I am seeing rather high values, for example. 15mm HMG, 0.076kg, 890mps penetration is 26mm, I am assuming ta 90° at peak velocity. This seems a bit high as MG151/15 mm cannon firing AP rounds should achieve 16mm at 30° from horizontal – which is about 18mm of armour. This is a 100m and a small round like that may lose momentum quickly, but at 500m its penetration only drops by 1mm so I am uncertain. The Germans liked using an APHE round, so this could be the cause, but the Besa has similar values. Not a major issue, but interesting.
The 12.7mm round, in this case an AP W.Mk.1, weights 0.038kg with a velocity of 787mps can penetrate 11mm@30° - which is about 12-13mm of armour. The calculator shows 18mm. If we use an AP/T round which has a higher velocity the penetration is 20mm.
For the 6-pounder, using the L43 version the British normally used rather than the L43 the US preferred, the APCBC round (APCBC,Mk 1T) has a velocity of 823mps and weights 3.3 penetrates 83mm. British tests show a value of 112mm@90° at 100m. This seems a bit low. If we look at the APC round (APC, Mk8T) the weight is 2.86kg and velocity is 946mps we get an 88mm value. This is more accurate as British tests show 92mm@90° at 100m. At 500m this drops to 83mm. Note: The error could be caused by converting yards to metres. Finally the APDS round, APDS Mk 1T, weights 1.42kg and has a velocity of 1151mps which comes in at 76mm. As this had a value of 120mm@60°, or about 132mm@90°, at 100m. I suspect if using exotic rounds like APDS the calculator does not work, but its acceptable for most rounds such as APHE, AP, APC, APCBC and APBC. I do not have the weight for an APDS would with sabot, perhaps if this is added in the values will look better.
Generally this is a good attempt.
Are you using a reference round? If so, the reference round should of course be similar to the hypothetical. So WWII Soviet APCR would compare nicely with WWII German APCR.
DeleteWhat is DeMarre? I can't find a reference for it.
ReplyDeleteThe DeMarre equation was developed to estimate penetration of naval armour. It's described in many books, I got it from WWII Ballistics - Armor and Gunnery.
Deletewe did this for a manhole... turns out it can pen 14m of armour with Krupp calculation... interesting.
ReplyDeleteSorry what does it means NaN
ReplyDeleteNot a Number. That means you entered some information wrong an an error occurred.
DeleteDeMarre calculator isn't really working, I put in 12.7kg mass, 125mm caliber, and 1050m/s, and hit calculate with nothing popping up except NaN in the Krupp penetration value area.
ReplyDeleteMake sure you hit "Calculate Krupp" rather than "Calculate DeMarre". I don't think that you'd get a good estimate for 125 mm APFSDS with the Krupp equation.
DeleteWhy is War Thunder Japanese Type 5 75mm only pens 150mm flat, when archives documents and this website put it above 180mm of pen
ReplyDeleteHow come when i ran the L55 smoothbore gun that can be found on the leopard 2A7 it gave me a 2,296mm penetration? Seems(and forgive my french) a little bullshit
ReplyDeleteProbably because these equations predate this gun by about a hundred years.
Deletethese equations work only on regular, full caliber shells. modern discarding sabot ones don't reflect accurate results in general. although, they technically should work if you enter the caliber of the penetrator rod, not the overall gun
DeleteThe penetration of the steel pen my friend has is about 90mm at 800m/s if you think of it as an AP shell, to which it actually comes close in material and shape :D
ReplyDeleteThe Krupp formula seems to achive somewhat more realistic results for low velocity shells while high velocity shells tend to have less penetration than they should. DeMarre is the opposite, where low velocity shells tend to have too little penetration.
ReplyDeleteSince Krupp never has more penetration than DeMarre at high velocity I would say the Krupp value is more accurate for the times it is higher than the DeMarre value.
For example the German 37mm APHE (0.685kg) is supposed to penetrate 19mm at 30° at 1500m.
German penetration data gives the shell around 19mm at 30° penetration for a velocity of 300m/s and around 34mm at 30° for 700m/s.
The shell supposedly penetrates 45mm at 0° with 745m/s.
When using DeMarre this results in the shell only having 12mm of penetration for 300m/s. Krupp at least gives 17mm. Still somewhat off from 19mm at 30° but I guess it's the work of overmatch that isn't really considered in those formulas.
Might also be related to the armor hardness, since the test plates were quite hard and hard armor is less efficent against overmatching shells.
Krupp values are also very similiar to the protection offered from FHA.
FHA is effective against low caliber high velocity shells but not so much against overmatching shells. Which would explain the armor values for Krupp shells.
Correction:
Delete37mm APHE is supposed to penetrate roughly 50mm and not 45mm.
Unfortunately it appears the DeMarre calculation is not working. I tried to input the calculation without touching the Krupp calculation and it would not allow me to. I am also not seeing anything with regards to mythical angles calculations or whatever that people keep mentioning. Help?
ReplyDeleteTo get a DeMarre calculation you need to fill out all the fields in Estimate except Penetration and all the fields in Reference, then click Calculate (DeMarre).
DeleteThe calculator doesn't support angles.