[40k] Calcing the LeMan Russ

[MKSheppard]

http://uk.games-workshop.com/imperialgu ... manders/1/
GW Statz on LeMan Russ

Tanksharp Sheet on the LeMan Russ

Weight
61 tonnes

Hull length
7.08m

Hull width
4.86m

Height
4.42m

Barrel length
3.07m (making it a 120mm L25.7 weapon)

Ground clearance
0.45m

Armour
45 - 200mm

Max Speed
29kph on road

Crew
6 (Driver, Commander, Gunner, Loader, 2 x Sponson Gunners)

Armament
Turret-mounted battle cannon (120mm smoothbore), hull-mounted lascannon, 2 x sponson-mounted heavy bolters

Main ammunition
36 shells in flash protected magazine.

----

Keep in mind that tanksharp was designed for modern tanks, with no sponsons...

So putting these numbers, I find that "plassteel" is probably 4 g/cm3 (0.5 g/cm3 lighter than titanitium), compared to 7.86 g/cm3 (steel); in fact, we NEED a density of that much, in order to meet (or get close to) the weight of 61~ tons.

I also decided that the KE and HEAT resistance of plassteel would be 1.23 (e.g. 23% better than RHA), which is pretty impressive, considering that Titanitium Armor today has a mass of 4.5 g/cm3, and only a KE resistance of 0.8 (80% of RHA).

So overall stats of the LeMan Russ in Tanksharp:

Length 7.08 meters
Width 4.86 meters
Height 4.58 meters
Track Width: 640mm (calculated from known lengths on the diagrams on the GW site)

Crew 6 men
Passengers 0 men

Weight Breakdown
Crew Weight 1.08 metric tons
Passenger Weight 0 metric tons
Armor Weight 42.13 metric tons
Armament Weight 1.05 metric tons
Ammunition Weight 0.91 metric tons
Engine Weight 0.27 metric tons
Fuel Weight 1.07 metric tons
APU Weight 0 metric tons
Capacitor Weight 0 metric tons
Transmission Weight 1.91 metric tons
Amphibious Equipment Weight 0 metric tons
Suspension Weight 2.25 metric tons
Track Weight 9.29 metric tons
Road Wheel Weight 1.53 metric tons

Engine 620 horsepower (Gas turbine)
Fuel Capacity 350 gallons
Maximum Hull Speed (water) 7.43 MPH

Combat Weight 61.51 metric tons
Ground Pressure 19.3 PSI
Power/Weight Ratio 10.08 hp/tonne
Top Speed 18.27 MPH
Operating Range 105 miles

Density of Vehicle 0.60 g/cm3 (My god, it can can float!)
Vehicle Freeboard (Transiting) 1.38 meters
Vehicle Draft (Transiting) 2.07 meters

Protection Levels:
I assumed that only the frontal hull would be armored to 200mm of Plassteel, while all other areas were armored only with 45mm Plassteel (previously I had the sides as 60mm plassteel, and the rear and hull floor and roofs as 45mm, but that drove weight up to 67 tons).

If you're asking me: Why the fuck did I choose 45mm hull roof and floor, when you don't need that much? Well, because 40k design philosophy is THAT STUPID, and the GW website on the LeMan Russ gave minimum armor as 45mm.

So the protection level is:

----------------------------- KE (mm) ----- HEAT (mm) ---------- KE Resistance

Front Hull Armor ---------- 348 ---------- 348 ---------- Resistant to Early 105mm and modern 76mm
Side Hull Armor ---------- 55 ---------- 55 ---------- Resistant to Soviet 30x210mm M53
Rear Hull Armor ---------- 55 ---------- 55 ---------- Resistant to Soviet 30x210mm M53
Top Hull Armor ---------- 55 ---------- 55 ---------- Resistant to Soviet 30x210mm M53
Hull Floor Armor ---------- 55 ---------- 55 ---------- Resistant to Soviet 30x210mm M53

Front Turret Armor ---------- 293.32 ---------- 293.32 ---------- Resistant to Early 105mm and modern 76mm
Side Turret Armor ---------- 66 ---------- 66 ---------- Resistant to Soviet 30x210mm M53
Rear Turret Armor ---------- 55.35 ---------- 55.35 ---------- Resistant to Soviet 30x210mm M53
Top Turret Armor ---------- 55.35 ---------- 55.35 ---------- Resistant to Soviet 30x210mm M53

[MKSheppard]

Addenum: The 45mm top protection might not be as stupid as it seems; since da Orkz have jetpakz and mines.

[MKSheppard]

Addenum II: I'd be open to making the KE/HEAT thickness efficiency of Plasteel to 1.5; that would be giving it a resistance of:

Front Hull Armor-------424-------424-------Resistant to Early 105mm and modern 76mm
Side Hull Armor-------68-------353-------Resistant to 40mm L70 M56 AP
Rear Hull Armor-------68-------68-------Resistant to 40mm L70 M56 AP
Top Hull Armor-------68-------68-------Resistant to 40mm L70 M56 AP
Hull Floor Armor-------68-------68-------Resistant to 40mm L70 M56 AP

Front Turret Armor-------357.71-------357.71-------Resistant to Early 105mm and modern 76mm
Side Turret Armor-------80.48-------80.48-------Resistant to US 25mm
Rear Turret Armor-------67.5-------67.5-------Resistant to 40mm L70 M56 AP
Top Turret Armor-------67.5-------67.5-------Resistant to 40mm L70 M56 AP

Please note, that if such a material with a density of 4 g/cm3 and a TE of 1.5 existed, it would be hailed as a uber wonder material, and the Army would be buying it all up to make the M-1 have many many times the protection on the same weight...

[white_rabbit]

Interesting read, whats tanksharp ?

[Vehrec]

Shep created a HAB spreadsheet to design tanks in. This is a product of it.

Also, while it might float on paper, I would never take my Russ in the water. Too many holes and it's shape is all wrong for boating. If I'm guessing correctly, they based that height from the base of the treads to the top of the turret, and Tanksharp unless I miss my guess calcs the volume as a simple box. Not that Shep used bad numbers! It's just that GW's numbers are crap.

It's interesting that the LR's Frontal armor can be penetrated by a 76 according to these numbers. Plassteel may be even more impressive than is estimated here.

[Shroom Man 777]

Hrm, I thought the main gun was stubbier and of a wider...width than just 120mm.

[MKSheppard]

Shep created a HAB spreadsheet to design tanks in. This is a product of it.

You can see it here

Also, while it might float on paper, I would never take my Russ in the water. Too many holes and it's shape is all wrong for boating.

Well, you can use the treads for propulsion, and as long as proper water sealant methods are taken, like covering over the bolter muzzles, etc, it should be able to swim easily.

If I'm guessing correctly, they based that height from the base of the treads to the top of the turret, and Tanksharp unless I miss my guess calcs the volume as a simple box.

This is the current mathy model for Tanksharp:

[Azazal]

Hrm, I thought the main gun was stubbier and of a wider...width than just 120mm.

Can't remember where, but GW has it listed that the main cannon has a cooling shroud on it, which makes it look like a snub nose 14 inch cannon.

[RRoan]

Keep in mind the levels of protection provided by the armor is likely way higher than what's put down. Remember, in one of the stories a Leman Russ (probably a variant, but I wouldn't think the difference would be that huge) took a shot powerful enough to shove it several meters sideways without its armor being penetrated. In fact, I have the quote:

Re-laying the gun took a vital second. In that time, the second tank fired again and hit the Wrath squarely. The impact was enough to lurch all sixty-two tonnes of armoured machine several metres sideways. But it didn't penetrate the twenty centimetre-thick armour skin. Inside, the crew were dazed and they'd lost most of the forward scopes.

That would seem to indicate armor a tiny bit tougher than what you have on there.

[andrewgpaul]

That also pretty much states side armour of 200mm, too.

[MKSheppard]

Remember, in one of the stories a Leman Russ (probably a variant, but I wouldn't think the difference would be that huge) took a shot powerful enough to shove it several meters sideways without its armor being penetrated.

A LeMan Russ weighs 61 metric tons; that's 61,000 kg.

That works out to 597,800 Newtons; and to move that much oh, four meters; you need 2.3 million joules.

A 155mm artillery shell weighing 44.5 kg (typical weight), fired with the lowest propellant charge, giving it a velocity of 400 m/s, will have a muzzle energy of 3.56 million joules. Obviously, such a shell will not have excellent penetration characteristics; but would strip away external things like vision blocks and lights.

Alternately:

The 120mm M829 "Silver Bullet" penetrator weighs 4.26 kilograms, and has a muzzle velocity of 1,670 m/sec; giving it 5.9 million joules of energy.

The 120mm M829A1 "Silver Bullet" penetrator weighs 4.88 kilograms, and has a muzzle velocity of 1,575 m/sec; giving it 6 million joules of energy.

The 120mm M829A2 "Silver Bullet" penetrator weighs 4.92 kilograms, and has a muzzle velocity of 1,680 m/sec; giving it 6.9 million joules of energy.

The 76mm M464 (aka modern 76mm) penetrator weighs 2.52 kg and has a muzzle velocity of 1,433 m/sec, giving it 2.5 million joules.

So yes, my armor numbers are correct. Did anyone EVEN think to do these numbers before?

That also pretty much states side armour of 200mm, too.

That's simply impossible.

If we up the side armor to 200mm; guess what? Vehicle weight goes to 87 metric tons; and ground pressure goes up to a whopping 27.5 PSI; and road speed falls to 12 MPH.

If we assume that there IS 200mm of side armor AND the vehicle weight IS 61 tons; then guess what; the density of this armor is going to be around that of Aluminum, or less than it, e.g. 2.66 grams/cm3, and that simply rapes the laws of reality even more.

[Ford Prefect]

Of course, then you have stuff like the Leman Russ Conqueror (mounting a lighter gun) with 'a hundred and ninety tons of recoil force'. I remember that back in the day, Connor explained that 'ton-force' came out at around 9-10,000 newtons. That's over a million newtons, compared to just under 8300 for the M829A2.

It's a pity I can't find his detailled analysis of the Wrath incident though.

[MKSheppard]

Of course, then you have stuff like the Leman Russ Conqueror (mounting a lighter gun) with 'a hundred and ninety tons of recoil force'. I remember that back in the day, Connor explained that 'ton-force' came out at around 9-10,000 newtons. That's over a million newtons, compared to just under 8300 for the M829A2.

So you're saying that a 60 ton tracked vehicle can mount, AND withstand the recoil force of a weapon equivalent to the 16"/50 Mark 7 Naval Rifle, firing a 1,225 kilogram (2700 lb) Superheavy AP shell at 762 m/sec in shear power?

That 16"/50 comes out to a recoil force of 933,450 newtons; LESS than the million plus newtons your LeMan Russ Conqueror supposedly can fire.

Even more fun is that the triple mount for that 16"/50 averaged about 567 tons per gun; about oh, 9 times the weight of a LeMan Russ.

[Ford Prefect]

Yeah, I am. We are talking about a society advanced enough that it can throw multi-hundred million, multi-billion ton objects around at thousands of gees. That they don't have the technology to negate a measly million newtons would be rather inane.

Also, doing a little searching, I found NecronLord's grand 40k quantification thread (here), where he suggests that the Wrath incident is upwards of seventy megajoules to as much as a gigajoule.

[Winston Blake]

Remember, in one of the stories a Leman Russ (probably a variant, but I wouldn't think the difference would be that huge) took a shot powerful enough to shove it several meters sideways without its armor being penetrated.

A LeMan Russ weighs 61 metric tons; that's 61,000 kg.

That works out to 597,800 Newtons; and to move that much oh, four meters; you need 2.3 million joules.

What on earth are you doing? You just found the energy required to lift the tank upwards 4m. At the very least we'd need to model the sideways reaction force as viscous damping, which would depend on the terrain.

That 16"/50 comes out to a recoil force of 933,450 newtons; LESS than the million plus newtons your LeMan Russ Conqueror supposedly can fire.

Who cares about overall force, anyway? Impulse is what matters here - you could apply a giganewton to a gun for a nanosecond and it'd move as much as it would if you applied a 100 g force for one second. The pressure applied would be enormous (probably enough to do damage), but it's certainly not going to blast off.

In other words, the Leman Russ could easily have the stated recoil if it's just a narrow peak on the force by time curve.

[MKSheppard]

Yeah, I am. We are talking about a society advanced enough that it can throw multi-hundred million, multi-billion ton objects around at thousands of gees. That they don't have the technology to negate a measly million newtons would be rather inane.

And where does all that energy go? Handwavium land? Do the magic space fairy pixies take it away?

You can get away with it on a massive miles long starship with a lot of mass to damp stuff; and all that energy that is absorbed from a weapons hit or a weapon's recoil can easily be radiated away into space (quite easy when the rough temperature outside of the hull is -233.15 Celsius).

It's not so easy on a mere 62 metric tons, and in a planetary atmosphere of 20~ C.

[Ford Prefect]

And besides, 2.3 million joules is far too low. Just doing some very rough numbers, a projectile with almost six hundred thousand newtons of force would have a KE of almost three hundred million joules.

[Ford Prefect]

And where does all that energy go? Handwavium land? Do the magic space fairy pixies take it away?

Intertial dampners, that magical science fiction technology stopping people turning into jam at ridiculously high accelerations.

[Academia Nut]

If we assume that there IS 200mm of side armor AND the vehicle weight IS 61 tons; then guess what; the density of this armor is going to be around that of Aluminum, or less than it, e.g. 2.66 grams/cm3, and that simply rapes the laws of reality even more.

Yeah, cause superstrong aluminum is impossible

Plus, there are two ways of interpreting the word plassteel in my mind.
A) Plastic steel, which from a materials point of view is a little funky considering that you want your steel to behave in a mostly elastic way under normal conditions, unless of course this is merely a colloquialism that describes that the steel contains what we could call plastics, as in long chain organic polymers, in which case who knows what kind of funky nanotech materials it could be made from
B) Plasma steel, which brings to mind all sorts of possibilities for making superlative materials, although this option is somewhat less feasible as it doesn't solve the density problem quite as much

Just remember, this is a civilization that has had tens of thousands of years to cook up the kinds of materials that we would think of as impossible, when the real world is already coming up with things that would have been thought physically unachievable twenty years ago

[Connor MacLeod]

Winston's right about the force issue, and in the case of the "one hundred ninety tons" bit I was wrong about how I calced it - assuming a full second of recoil was rather absurd.

On the other hand, it's quite possible to compare the "recoil force" of the tank to the recoil force of other weapons (I found a number of sites that list them for some tanks and howitzers.) Sufficed to say, the Conqueror is STILL at least sveral times more powerful than "modern" guns. This is consistent with the performance of the Narmenian tanks in Necropolis which blast a titan-sized vehicle (IE massing thousands of tons) off of a wall (And blast a huge chunk out of the wall at the same time.)

As for why the tank can generate these enormous forces/momentums despite its given tonnage, there are several possibilities. The first is that the tanks in question are specified to carry "inertial dampers", which we know from Eisenhorn are specifically gravitic devices. Using them to provide counterforce to counter the recoil would account for that. The other possibility is that they're using rocket-propelled ammunition (like a bolter round.) Admittedly there is no direct evidence for 'Russes to use such ammo, but it is stated in IA1 that Baneblades use it, and Basilisks can use rocket-propelled ammo too.

As a side note, scaling of the 'Russ's Battle cannon tend to put it between 6" and 9" (more akin to an artillery cannon than an MBT cannon.) This makes sense, since auto-cannons (as per Rogue Trader) were stated to be just like modern tank guns (and we know Predators use autocannons as an anti-tank weapon. There are 'Russ variants that use autocannons as well.)

I should note that the Stats and capabilities for a Leman Russ tank can vary ENORMOUSLY, especially if you incorporate the forgeworld stats, what its equipped with, the kind of engine it has, and the quantity of armor used.
Hell, with Chimaeras some models can use some sort of nuclear reactor, so the 'Russ probably can as well.

[Connor MacLeod]

And where does all that energy go? Handwavium land? Do the magic space fairy pixies take it away?

You can get away with it on a massive miles long starship with a lot of mass to damp stuff; and all that energy that is absorbed from a weapons hit or a weapon's recoil can easily be radiated away into space (quite easy when the rough temperature outside of the hull is -233.15 Celsius).

It's not so easy on a mere 62 metric tons, and in a planetary atmosphere of 20~ C.

Probably by whatever defensive means they use to fend off multi-GJ laser and melta gun attacks as well. Considering that the hulls of their vehicles can glow white hot (and stay that way for seconds at a time) without melting (Ghostmaker) If you really want to get pedantic about it, we know from earlier fluff that tanks could incorporate forcefield defenses.

Of course, we don't know how it does it precisely, just as we don't know the precise workings of turbolasers or such. Doesn't stop us from estimating performance from observation. Kinda like we can tell how AT-AT armor can shrug off blaster fire without the sorrts of problems you claim exist.

Why the fuck are you talking about just energy in terms of a physical impactor and recoil anyhow? A kinetic impact deals with force AND momentum as MUCH as KE, unless you're IXJac. Projectiles aren't a fucking energy weapon.

[Winston Blake]

A 155mm artillery shell weighing 44.5 kg (typical weight), fired with the lowest propellant charge, giving it a velocity of 400 m/s, will have a muzzle energy of 3.56 million joules. Obviously, such a shell will not have excellent penetration characteristics; but would strip away external things like vision blocks and lights.

An impact from such a shell would not be able to lurch a 62 tonne mass as described. Energy is irrelevant here, momentum is the important quantity. An inelastic collision would give:

(44.5kg * 400m/s) / (44.5kg + 62 tonnes) = 0.3 m/s.

Imagine a 62 tonne tank resting on a perfectly frictionless surface, which is then hit in the side by a 155mm shell. It's now moving at just 30 cm/s. If that tank is put on normal ground, and hit similarly, it will obviously not be lurched 4m sideways. It probably wouldn't even move. Your pedantic listing of penetrator energies is pointless - they've got far less momentum than even that shell.

And besides, 2.3 million joules is far too low. Just doing some very rough numbers, a projectile with almost six hundred thousand newtons of force would have a KE of almost three hundred million joules.

Can I ask what formula you could possibly be using for that?

Shep was correct that applying 600e3 N over 4m requires 2.4 megajoules - you just multiply them. This is aside from the fact that his model is ridiculously wrong.

[Connor MacLeod]

What on earth are you doing? You just found the energy required to lift the tank upwards 4m. At the very least we'd need to model the sideways reaction force as viscous damping, which would depend on the terrain.

IIRC from Honour Guard the terrain was basically "flat" (forest close to a town cleared of trees for about a kilometer's distance.) It was a close range shot (few tens of meters) on ground that inclined slightly downwards from where the Conqueror was (the enemy tank which caused the Conqueror to lurch would be firing upwards.)

The incline probably wasn't significant, though - a laser-cannon armed tank destroyer was able to fire past the Conqueror and destroy the enemy tank very shortly after and the incident is described as bein gnearly parallel IIRC.

Can I ask what formula you could possibly be using for that?

Shep was correct that applying 600e3 N over 4m requires 2.4 megajoules - you just multiply them. This is aside from the fact that his model is ridiculously wrong.

He's probably citnig one of my earlier calcs (the one I already admitted I screwed up on, the "ton-force" one, that is.) I'm assuming he's actually referring to estimated momentum but screwed up the notation (I suppose that should be "newton-second", rather than just "newton."

As it stands now the actual "momentum" of the Conqueror projectile is probably around 2x that of a 155mm howitzer (I have to dig out the sources on my computer which would take time.) In terms of firepower, ,I now estimate the Battle cannon on a "Russ" to be around a "cruiser grade" gun (6-8") both in terms of scale and performance. It might have KE approaching a small battleship cannon due to the difference in velocity, but the momentum won't be anywhere near that.

[Ford Prefect]

And besides, 2.3 million joules is far too low. Just doing some very rough numbers, a projectile with almost six hundred thousand newtons of force would have a KE of almost three hundred million joules.

Can I ask what formula you could possibly be using for that?

Shep was correct that applying 600e3 N over 4m requires 2.4 megajoules - you just multiply them. This is aside from the fact that his model is ridiculously wrong.

The Wrath was hit by a projectile carrying some 6E5 newtons. I derived a mass and velocity from that (600 kg, which would be pretty silly, and a velocity of 1000m/s). I took those numbers and tossed them through the KE equation.

[Ford Prefect]

EDIT: I forgot to add that on reflection (after your reaction), that is is probably very silly, as I can derive nine billion joules from that.