Xlucine

I hope you like submarines.
 
http://www.dtic.mil/dtic/tr/fulltext/u2/a059747.pdf
The submarine equivalent to Technology Of Tanks. By the chief engineer at Kiel when Germany restarted production. I know a few mechanical engineers involved in subs who say that this is about as good as books on the subject get.
 
http://www.dtic.mil/dtic/tr/fulltext/u2/342338.pdf
Unconventional sub propulsion methods.
 
http://www.dtic.mil/dtic/tr/fulltext/u2/a213542.pdf
Submarine electric propulsion
 
http://www.dtic.mil/dtic/tr/fulltext/u2/a538633.pdf
AIP

German concept proposed during the Kampfpanzer 3 / FMBT project to the UK via https://andrei-bt.livejournal.com/928203.html
 
Twin-gun casemat tank from Maschinenbau Kiel:



 
Low-profile turret tank with driver in turret by Krauss-Maffei (similar to MBT-70, but with 120 mm smoothbore gun and manual loader - maybe derived from the Eber concept):


 
Data:


 
Armor is spaced steel plates, sometimes with fuel inbetween them. The MaK design has 727 mm thick armor, but the actual steel thickness is just 259 mm...




 
Note that according to Krapke a third concept (AFAIK either turretless or with unmanned turret?) was proposed.

It wouldn't - the benefit is the reduced cross-section reducing the drag.
 
Technically the propellant gases will still accelerate the projectile through the conical bit, but as the diameter (and area at the base of the projectile reduce) then the force applied by the gases also reduces (the energy taken to crush the skirts also slows it down) - so muzzle velocity for a squeezebore is lower than for a straight walled tube of equal length. To model one in the powley computer I'd be tempted to adjust the barrel length for constant swept volume (i.e. starting diameter * length input to powley computer = (starting diameter * length of straight bit of barrel) + (volume of conical bit of barrel)), the swaging losses are probably pretty small.

Let's say you're developing a tank with a unique (AKA non-historical) gun for one of our competitions here on SH. It would be nice to have an idea of the size of the gun, its shells, and what their performance both in terms of shell weight and velocity but also penetration, wouldn't it? Well, fortunately there is a way to do this with reasonably accurate results using your solid modeling software and some free to use browser tools.

First, you want to have a general idea of the size and performance of your gun. For this example, I decided I wanted an optimized, high velocity 85mm caliber gun with a case about as big as the 7.5cm KwK 42 (as it happened, I ended up with a case that had significantly greater volume, but that fact is unimportant for this example). The cartridge I decided on has a 130mm wide rim and a 640mm long case, of course in 85mm caliber. My first step was to model this case in SolidWorks:


 
You will also need to model your projectile, in this case a tungsten-carbide cored APCR round:


 
Next, we need a bit of freeware: A Powley computer. Originally developed by DuPont engineers for small arms ammunition, the Powley computer is an accurate enough tool to use for much larger tank rounds as well! When you click the link, you'll be greeted with this screen:
 

 
You'll note the dimensions are in inches and this thing called "grains" (abbreviated "gn"). The grain is an archaic Imperial mass unit equal to 1/7000th of a pound which is still used in the small arms field, today. Another quirk of small arms has the case capacity - a volume measurement - listed in grains as well. This is in fact grains of water (gn H2O), or the weight of water that will fill the case to the top. To find this, simply multiply the volume in cubic centimeters by 15.43 - which is also the exchange rate between the metric gram and grains mass.
 
Finding the volume of the case is easy with a solid modeling program; simply model the interior as a solid and find the volume of that solid:


 
Filling in my Powley inputs gives me this:
 

 
Note that I typically use the diameter of the projectile across the driving bands for "Bullet Diameter", but it really makes very little difference.
 
So far, though, we haven't actually produced any results. That's because our gun is well outside the bounds of DuPont production IMR powders, hence the output "Much slower than (IMR) 4831" in the lower left. So, we need to override the computer by checking the box next to the blue "Pressure" function, and typing in a pressure value in CUP that is reflective of tank guns of whatever era we are trying to represent. My tank gun is trying to represent something from about the late 1940s/early 1950s, so I'm going to use 45500 CUP EDIT: USE 41000 CUP for APCBC and 42800 CUP FOR APCR (or better yet, do your own calibration!):
 

 
This gives me an estimated muzzle velocity of 3,964 ft/s for my L/50 barrel. Not bad! Note the outputs on the left, which tell you a bunch of fun facts about your round but aren't terribly relevant to what we're doing here today. Next, we need to put this gun's performance in terms of penetration. The way I like to do this is through comparative analysis.
 
The first thing we need is to know to find penetration the ballistic performance of our round. We can estimate this using JBM's ballistic calculator and a few rules of thumb. When opening the calculator, the first thing you'll see is this:
 

 
We care about basically none of these settings except BC, velocity, and maximum range. Caliber, projectile weight, chronograph distance, etc are all pretty irrelevant to us. Keep the environmental settings (temperature, pressure, etc.) set to their defaults. First, change the ballistic coefficient type from G1 to G7 using the dropdown menu. Then, change the muzzle velocity from 3000 to whatever the muzzle velocity was that was calculated by the Powley computer. Finally, set the maximum range to your desired distance - in my case 2,000 yards.

For my round, I now have inputs that look like this:
 


We also need to get some idea of how fast our projectile loses velocity, something we can't know for certain without actually building a real gun and test firing it - or at least without some really sophisticated simulations. However, projectiles with the same shape tend to fly the same way, and that's something we can exploit here. To figure this out, we need a graph showing us the performance of a real-life gun. Fortunately, there is a handy one for an IRL gun similar to what I'm designing, the 90mm M3 from World War II, and its M304 HVAP-T, which is broadly similar in construction and shape to my 85mm APCR projectile:
 

 
Based on this chart, we see that the M304 should drop from its 3,350 ft/s muzzle velocity to about 2,500 ft/s at 2,000 yards. Doing a little trial and error with JBM tells me that this means the M304 has a G7 ballistic coefficient of about 1.13.
 
Now, our projectile will not have the same ballistic coefficient, due to it being a different size and mass. But, we can figure out what its ballistic coefficient would be by finding its sectional density and comparing that to the sectional density of M304. To find sectional density, take the projectile's weight in grains and divide it by the square of the projectile's diameter in inches, times 7000. So for M304, we get:
 

 


And for my 85mm, we get:


 

 
This means that the ballistic coefficient for an identical-shape projectile with our size and weight will be about 1.019/1.330 - or 76.6% as much - as that of the 90mm M304. That means a BC of 0.866 G7 should be approximately correct for my 85mm APCR round. Let's plug that in:


 
And then scroll down to the bottom to click "calculate", which gives us a big ol' chart that goes out to 2,000 yards:
 

 
O-Kay! Now we have some data. It looks like at 2,000 yards, my projectile holds about 2,800 ft/s striking velocity. It's important to note here that what we really care about isn't the striking velocity of the projectile per se, but the velocity and energy of the projectile's core. The core is what's actually doing a lot of work to the armor, so for now let's stop thinking in terms of the whole projectile, and take a look at these two cores, that of the M304 90mm HVAP, and that of my 85mm APCR round. The core of the 90mm M304 is an approximately 8 pound lump of tungsten-carbide that is about 45mm in width. My penetrator is also 8 pounds, but it's longer and thinner in proportion - just 40mm wide, rather than 45mm. This means my penetrator will penetrate more armor at a given striking velocity, and we can estimate how much more by taking the specific energy of the rounds and comparing them. That is, the energy in Joules of the penetrator alone, divided by the penetrator's diameter squared:
 

 


So the specific energy at 2,000 yards is about 826J/mm^2. Now, we need to find out at what impact velocity the M304 penetrator produces this same specific energy. Do do that, we go backwards, using the figures for M304:
 

 

 
Therefore, the equivalent impact velocity for my 85mm APCR round at 2,000 yards is 3,150 ft/s for the M304. That means, in theory, that the M304 would have to impact a target at 3,150 ft/s to produce equivalent penetration of RHA to my 85mm APCR striking at just 2,800 ft/s.

Now, we head back to that chart:


 
On the left side of the graph, we put our cursor on the line that corresponds to approximately 3,150 ft/s velocity, and follow it over until it hits the curved line that corresponds with the angle of plate we care about - arbitrarily, let's pick 20 degrees. Then, we follow that point straight down until it hits the x-axis:


 
Therefore, we estimate that at 2,000 yards, my 85mm has just over 10 inches of RHA penetration - not bad at all for a lowly APCR round!

I like the mental image conjured by that article of Jeb! walking around manhattan, showing everyone on the street the paper because he's just so damn happy

So, firstly, there has been no uncompensated siezure of land. And the compensated seizure of land fell over because it was at market rate. In fact, it was such a non-issue that Jacob Zuma (our previous president recently deposed in an internal party battle by Cyril Rhamaphosa) actually let the funding for the paid expropriation scheme drop to around 20% of the Thabo Mbeki era. The result is that whites currently own well over 70% of farm land in South Africa.
 
Was this process perfectly squeeky clean? Heck no. Even under the paid compensation scheme dubious land claims were put through (the one which included my folk's shared farm went in literally on midnight on the last day for claims to be submitted) and the resulting handovers had a disturbing tendency to go to politically well-connected businessmen operating "on behalf of" the communities that had a usable claim wherever there were, say, potential mining rights involved.
 
This new idea of making expropriation without compensation only came up about 10 minutes before Rhamaphosa captured the internal ANC vote and became the next leader of the party (and thus the president) by a whisker over his opposition, Nkosazana Dlamini Zuma (who is a story all by herself). It seems that, in the horse trading which got him the vote, Rhamaphosa had to agree to back the expropriation-without-compensation scheme once he became president. This must have been a bitter pill, because he is basically a Davos drone come to power and one of his early crowning political achievements was to help draft our Constitution (which the expropriation-without-compensationists maintain needs to be amended to make this work). So the whole thing has been a bit of a slow-roll so far, with lots of committees and hearings before anything too drastic happens.
 
The current news is that government has gone forwards with a 'test case' to see if expropriation-without-compensation can be done within the confines of our existing Constitutional provisions. Which it can't. This will inevitably turn into a giant, years-long fiasco in which our courts look at the issue before deciding that its bullshit and axing the whole thing. By which point the ANC will be safely past the 2019 elections and can go about pretending that this all never happened. That is, unless the EFF manages to out-maneuver them and so on.
 
Make no mistake: this is all very worrying. There is a good chance that the ANC, if it wants to retain power and not slide into an era of coalition government, will play on this obvious sore spot in our national dialogue to keep the EFF from gaining more traction and help differentiate themselves from the DA. And, since a bunch of our minority parties do actually want honest-to-goodness expropriation, communism, rains of blood etc, a constitutional vote may actually take place and an amendment may pass. Which will promptly make king Goodwill Zwelethini explode and will also end up getting declared un-constitutional (improbable as that sounds), but that's a story for another day. 

I guess this is fair; I should have withheld judgement, and I appologize for jumping to conclusions. Though, the current situation (with practically uncompensated, government sponsored seizure of land) is somewhat damning. 
 
 
I guess the biggest difference between these 2 situations is the media coverage: 
the cops “targeting blacks” over here was overblown by the media to ridiculous levels. Conversely, I personally haven’t seen much news from over there about the land seizures (and murders), except by smaller news sources and youtubers. Feel free to post stuff that enlightens me, though. 

I tried putting the values for the US 105mm on the T29 into that a few years ago and it matched exactly with hunnicutt (IIRC), which shows that there is precedent for predicting large calibres with it

Those idiots are serious that APILAS is Javelin.
 

Because diversity of views is the intellectual equivalent of exercise and getting enough fibre, I chatted to a colleague and friend who is more Afrikaans, conservative and right-leaning than me. His take is that an investigation should be welcomed and our government's reaction has been too negative. The innocent having nothing to hide etc.

Dude, as a South African: what the fuck are you talking about?

M.I.L.E.S, specifically the thing that flashes when you die. Fuck M.I.L.E.S. no seriously FUCK M.I.L.E.S.

Some photos from forest near my house. From this summer started to run in it.

 
 

Loader's position:

Final drives gave out after 150km on average, transmission excluding 3rd gear was ~1500km. (Governed) Engines were also around ~1,500km. The French also found that pivot steering greatly accelerated wear on the final drives, to the point of having cases of the drives breaking mid-turn, and they gave strict orders to avoid pivot steering it.

Wars started by america to force people to take opium: 0
Are you even trying?

Didn't the french find the panther broke after 150km, not 1500?
 
Panther was better than sherman at swimming uphill through mud, but churchill was dominate in poor conditions. Tigger was just hopeless, for some reason, and T14 (!) was about the same as the sherman
https://imgur.com/a/fV825TZ

Wars started by america to force people to take opium: 0
Are you even trying?

You know, that's pretty smart of them launching this probe at night. It'll have a better chance of not burning up since it's dark out. Probably can sneak up on the sun better too.

I remember being asked on this forum about the Israeli acoustic/dummy bombs Mikhol (paint brush) and/or Mikholit (small paint brush) which are used in the "Roof Knocking" protocol. Just found a video, from a recent event, that shows the implementation in a very clear way, compared with the limited available footage on YouTube.
 
 

1930s era histomap of religion:
 

Your correct that it's related to the Ram 3.7" Evolution of that. Designed but never built.

3.7" Assault SPG
 

 
 

Hi SH_MM, this is definitely not a 105mm projectile. Source: I saw it last sunday in the WTS museum in Koblenz. It looks like it is 25 or 30mm, does not have a type designation, but was something experimental. Forgot to take a picture of the sign. I'll do that when I visit it again. Very interesting museum for people interested in experimenta; weapons and prototype vehicles. I can recommend going there.
 
My fingers on the display for size:
https://imgur.com/UIFyFvP

Here (sadly) is the best photo I got: