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COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)


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Copying this from discord because it's important:
 

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OK I have satisfied myself when it comes to tank mass
I used a dual approach, one in which I calculated the mass of the tank using Ogorkiewicz's simple ratio of armor, which gave me 65.55 m.t
the other in which I took the armor mass, and assuming a ratio of 0.43 for the tracks to the armor mass (assuming tracks make up 22% of the final weight and armor 51%, the ratio there being ~0.43), and then I added up everything from the Challenger sheet that wasn't already included
that method gave me 70.09 m.t
that second figure is a good thing as far as I'm concerned as the error mode for Ogorkiewicz's armor ratio is that it scales in mass some minor things that do not scale in mass with the mass of the tank, especially armor. For example, your tank's optical system will not need to be heavier if you have addon armor packages, nor will most of your hatches.
the fact that the second figure surpasses the ratio methodology suggests that, if the ratio gives you a high number, it's not so much higher that it will put you above, say, having shitty heavy bongistani fitments or something
these figures by the way was for Comanche's "light" version. The "heavy" version with meme wedges on the turret is about a ton more
so I wanted to post that to give the competitors a little more to go on when it comes to estimating weights. It seems that using Ogorkiewicz's method gives very fair numbers, overall
this also, it strikes me, explains a lot about why tanks today are heavy
if your ancillaries weigh that much, you actually don't have that much mass left over for armor. like it's the majority of the tank, but you need a lot of armor
if you say "well I want a a 45t tank" great, but you end up with Leopard 1 that dies instantly to 3BM4
there's nothing wrong with Leopard 1 of course, but if you would like to stop the rare and elusive T-62, then you need more armor
yeah I figured you especially will need it
what you will be absolutely required to do with your tank, Curly, is from the beginning dividing all your armor components by 0.51 and tracking your estimated final weight
if a turret/hull armor array is throwing you above your weight goal, then you will HAVE to redesign it
this is why that ratio is so useful, because it gives you a remarkably accurate picture of your final mass at a really early stage of design
if you want to make sure you hit a specific weight, then use a lower ratio like 0.46
for example the Chieftain sheet methodology gives me a ratio of 0.477
so it's not a done thing that you'll be at 0.51 by any means
one notes: this is absolutely brutal
I mean I didn't think I was a tank prodigy or anything, I just figured yeah, you get 2020 hindsight and you can make some improvements here and there. Now that I fully understand this accounting, I am impressed at what designers did before they had tools like Solidworks


Challenger sheet:

j6PXFwN.jpg

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14 hours ago, Fareastmenace said:

I'm actually interested in this.

For example, if a round penetrates the crew comptartment, but to immediately get absorbed by something non essential, do we consider that simply entering the crew compartment generate enough spall? And if so, what kind of spall cone can we expect?

Any penetration of crew compartment is armour failure, simple. Catching shrapnel between teeth is for the movies.

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On 5/27/2021 at 10:57 PM, Sturgeon said:

That's unbelievably light!

The armour is, shall we say, optimized. Thin base armour, ERA providing most of the actual value, and very narrowly directed to the specific threats.

 

I also just realised that I forgot to include the engine bay and covers, which bumps it over :wacko:

 

Luckily there's still a bit to shave off - the hull front and turret front are a bit more generous on KE than they strictly need to be.

 

Edit: so, after some judicious shaving which takes the frontal protection down to the bare minimum in terms of KE protection (16"), I've gotten the total armour weight down to 19.3t (17.5mt). The empty weight according to the software is 37.3t (33.9mt), but my expectation is that a full accounting of weight will push me all the way to my weight limit. 

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I am going to be introducing a new recommended weight accounting method to help standardize results between contestants, and to better prepare them for the judges' ire. This method is not mandatory, however it is strongly recommended, as it is expected to be the method by which the judges weigh (literally) each entrant against each other.

First, we are requiring in addition to the standard elements included on the submission sheet, that you include the armor mass of your tank in your submission. The armor mass includes any armor elements of your tank, including in addition to armor arrays, also structural elements like a cast or welded hull body, skirts, armored engine decks, hatches, etc.

Next, to calculate the combat weight of your tank (as outlined in the submission template), you take the armor mass of your tank, and multiply it by 0.45 to get the mass of suspension components for your tank (this includes tracks, roadwheels, sprockets, swing arms, idler tensioners, return rollers, etc). The reason for doing this is that as suspended mass increases, the mass of the suspension must increase also, meaning that in successful tank designs this ratio of about 0.45 stays remarkably constant (as detailed in Technology of Tanks). Then, add the armor mass and the suspension mass together with these figures:

Gun weight: (variable)
Ammunition weight: (variable)
Ammunition racks weight: (variable, but in the absence of a modeled weight for them, 1,700 lbs is a fine figure)
Gun stabilization system and gun electrics: 1,700 lbs for a ~4.7 inch gun (cubic scaling according to caliber, with minimum of 1,000 lbs)
Engine weight: (variable)
Transmission weight: (variable)
Fuel weight: (variable, but if you haven't modeled it for your tank, then use the value required to meet the range requirement)
Fuel system weight: 750 lbs
Electrical and environmental systems (combined): 3,500 lbs
Optics, sighting: 300-500 lbs (depending on complexity)
Fitments, stowage, and installed equipment: 7,500 lbs
Any other objects you've modeled, like cupolas etc: (variable)
Crew: 265 lbs per crewman

 

This means that if I have modeled a tank's armor, which weighs 18 tons for the hull and 12 tons for the turret (including arrays, engine deck, armored hatches, etc), my math will look like this:

18 + 12 = 30 tons hull (incl. skirts) and turret
30 x 0.45 = 13.5 tons suspension
13.5 + 30 = 43.5 tons hull, turret, and suspension
43.5 * 2,205 = 95917.5 lbs hull, turret, and suspension
95917.5 +
5300 lbs gun
2,650 lbs ammunition
1,700 lbs ammo racks
2,000 lbs gun stabilization and electrics
4,950 lbs engine
5,400 lbs transmission and final drives
3,660 lbs fuel
750 lbs fuel system
3,500 lbs electrical and environmental
500 lbs optics
7,500 lbs fitments, etc
265 lbs * 4 crew

=

134887.5 lbs combat weight for the tank, or 61.2 metric tons.

 

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Reposting this here for our contestants' reference
Height: 80mm plates making up 78% of perimeter, glacis making up 6%, rear (thinnest) 6%
Width: 25-37mm plates making up 81% of perimeter, glacis making up 19%
Length: 80mm plates making up 34% of perimeter, 25mm plates making up 66%
those are for Comanche's hull
also, only length adds track run
so if you need more volume, make your tank longer, and for the love of god do not make your tank hull taller
also you'll notice that raised engine decks are awesome

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Final Entry: Main Battle Tank, 2247, project name "Derebus"

 

7for5rn.jpg

 

Main dimensions and statistics

  • Manufacturer: Paramount-Allen-Fullerton (Para-allful) Conglomerated
  • Mass estimate (as based on CAD model plus ~6600lb to account for drive systems, crew amenities, ammunition and miscellaneous components): 43.1t (39.1mt) fully loaded, fueled.
  • Armour mass (1-2" (25-50mm) RHA base plus ERA, composites, side skirts and engine bay liner): 20.6t (18.5mt)
  • Calculated mass: 43.4t (39.4mt)
  • Crew: 4 (commander, gunner, loader, driver)
  • Length: 246" (6.25m) hull, 379" (9.63m) total 
  • Width:  150" (3.8m) with skirt
  • Height: 95" (2.41m) to top of commander's hatch, 109" (2.77m) total

 

xRy3O9X.jpg

Firepower


Note: the armour used for the target has the same hardness (360BRN) as the armour used in the vehicle. The target was at 0 degree obliquity for calculation purposes.

 

  • Main gun: 5-inch 55 calibre (127mm L/55) high/low pressure gun
  • “High pressure” = 70000 PSI (480 MPa) operating pressure, 14.16MJ energy.
  • Vertical travel: +15'/-10'

 

Ammunition:

  • 46lb (20.85kg) HEAT-FS, penetration of around 21" (535mm) using 122mm BK13 derivative (420mm if using BK13 penetration), 3074fps (937m/s), 9.14MJ using a low-pressure charge (~45k PSI).
  • 46lb (23.2kg) HE, (5.7kg) fill, estimated blast penetration of ~55mm RHA, 2910fps (887m/s)
  • Simple APFSDS (15:1 LD, 550BHN monosteel body, tungsten insert, 115mm cap, ring sabot): 1.57x23.54" (40x597mm) rod, 0.866x5.24" (22x133mm) insert, 14.2/5.2lb (5.6/3.2kg) penetrator/sabot mass, 1800m/s, 15.7/13.8" (400/350mm) penetration at 100/2000y.

 

Note: if following the design of 3BM-26, this could be higher in practice. Using DeMarre the estimated penetration is 17.1" (435mm) at 2000y. Upgraded monobloc projectiles could match and eventually improve on this, up to 25.6" (650mm) before needing to rework the ammunition storage.

 

Details:

 

  • Gun has a high-pressure and low-pressure recoil option, selectable on the slide – this doesn’t affect the recoil mechanism, it just changes where the trip key is to unlock the breech. Warning: don’t fire high-pressure ammo with the low-pressure setting selected!
  • Gun uses a separate 6.9x27" (175x685mm) charge: 44lb/20kg mass, semi-combustible case built along the lines of the 4Zh-40 charge used with the 2A26 gun), matching the length of the HEAT-FS round.
  • This charge gives space to produce a more powerful round to match higher future barrel higher pressures (when using a secondary charge with the APFSDS projectile itself). 74000 PSI (510 MPa) gives a potential power of 15MJ. 94000PSI (650 MPa) gives a potential power of 19MJ.
  • Final penetration potential of the gun with early monobloc DU projectiles is something in the region of 22" (550mm) at 2000y (putting it on par with Mango and Vant). Being able to store and handle a longer projectile (ie: above 27") would probably allow something a bit better than Snivets. 
  • Low-pressure charges are shortened (17.1" / 435mm) and come with an ejection spring to work with the same tubes as the high-pressure charges.

 

Storage:

  • 19 charges and 9 active projectiles (HE and HEAT) in armoured tubes in the turret. The tubes are sealed at the front and lead to a blast chimney that outlets to blow-off panels in the turret roof. 10 inert projectiles (APFSDS) are stored in various places in the turret space, held by retaining clips.
  • 16 charges and 8 active projectiles are stored on either side of the driver behind the fuel cells, also using the blast chimney approach (exhausting out the hull sides). 8 inert projectiles are stored in various spots in the hull.

 

Secondary weapons: 

  • .30cal MG as coax
  • Both the commander and loader’s hatch rotate and have mounts for .30 cal MGs.

 

Fire control:

  • Single axis stabilized gunner’s sight
  • Duel axis stabilized main gun
  • Vertical coincidence rangefinder (stadiametric, 39.4" (1m) base) which doubles as a redundant back-up sight.
  • Simple electronic gun-follows sight fire control system (encoder connected to sight mirror feeds elevation data into a transistor-based PID controller, which tries to match position on a similar encoder connected to the gun. When gun position and sight position align, the firing mechanism is electronically triggered).
  • Semi-autoloader: the loader places the charge and warhead on trays in the bustle. these are then fed into the gun using an automatic mechanism (horizontal rammer, pivoting loading tray and rigid chain actuator to ram the warhead and charge home). The gun automatically returns to the loading position after each shot. A short spring at the end of the actuator helps to smooth out the loading impulse.
  • LRF mounted above barrel.

 

Note: Industrial espionage has allowed Texan engineers to copy the laser rangefinder proposed for use in the Cascadian M8A1 upgrade package. The Texan copy of the LRS-2 ruby laser rangefinder uses a flashlamp-pumped ruby laser, optical sensor, quartz timing circuit and the sequential event time sampling approach (with post-sampling amplification) to allow time-of-flight rangefinding using a lower timebase and bandwidth compatible with current electronics. Solid state electronic components allow the system to be fairly compact and robust. The rangefinder features a numerical readout in the gunner’s station. The rangefinder has a maximum operating range of 5km in clear conditions and has an average estimation error of 1%. 

 

The TBC-3A ballistic computer and IAPO-3 sight were not copied, as the high velocity of the APFSDS used in the 5”/55 cal main gun was felt to provide sufficient accuracy when paired with a good rangefinder.

 

Mobility

DuxRMpb.jpg

  • Transverse-mounted Kharkiv V-2-derived engine (specifically the V-55 diesel): 600HP/448kW, 2248lb/1020kg dry weight. The engine has been slightly re-bored to 40l, but is otherwise mechanically very similar to the engine used on the historical T-62.
  • Hydraulic torque converter feeding into Merritt-Brown-style double differential system.
  • An alternate engine layout would be two V-6 engines of similar total displacement, mounted normally, with a combined linkage to the torque converter.
  • The engine, transmission and cooling system all sit in an aluminium tub that fits into a bay in the rear of the vehicle. This can be removed entirely for servicing, or to replace the powerpack with a different configuration.
  • Suspension: 20" (0.5m) ground clearance, geared torsion bar suspension, each axle pair in detachable units shrouded by aluminium housings. Wheels are 23.6" (0.6m) in diameter, with a track width of 27.6" (0.7m) and a pitch of 7.7" (0.195m).
  • Fuel load: ~2400lb total (639lb/290kg in tanks flanking the driver, 1764lb/800kg in rear sponson tanks, range of 490mi at 30mph
  • PWR: 13.8 HP/t (11.4 kW/mt)
  • Ground pressure (calculated MMP): 29.4 PSI (203 KPa). 
  • Track contact length: 153.5" (3.9m)
  • Track contact area: 58.8ft2 (5.46m2)
  • Nominal ground pressure (based on calculated weight): 10.3 PSI (70.77 KPa)

 

Protection

g2uyzV5.jpg

lJAa9j6.jpg
Notes:

  • Composite liner (50:50 HHA/textolite): density of 4.825g/cm3, layers of 0.2, 0.4, 0.6, 0.8 or 1" depending, with thickness adjusted to prefer the thickest possible layers (1"/1") with a thinner backing layer.
  • Mounting bolts for ERA layers are not modelled, but are accounted for.
  • The covers over the rear fuel cells are 1" RHA.

 

Turret front:

  • Two layers of L-ERA, sloped at 75’
  • Base armour: 1" (25mm) RHA sloped at 75’
  • 2.1" (55mm) composite (25mm HHA, 25mm textolite), sloped at 75’
  • KE: 16.9" (430mm)
  • CE: 89" (2250mm) vs single-charge. Tandem charge rated to penetrate both layers via precursor is something like 17.9/11.4" (455/290mm), corresponding to 3"/3" high/low-precision charges and a 4" form factor.

 

Turret cheeks:

 

Note: because of how the cheeks are sloped, protection actually drops off the closer you get to the 25’ arc.

 

  • Three layers of L-ERA sloped at 25’ in the horizontal
  • Base armour: 1" (25mm RHA), sloped at 25’ in the horizontal
  • 2.2" (55mm) composite, sloped at 25’ in the horizontal
  • KE: 11.4" (290mm) from the front
  • CE: 55" (1400mm) (normal) vs single charge. Tandem charge rated to penetrate both layers via precursor is something like 12.2/7.3" (310/185mm), corresponding to 2.1/2.4" (55/60mm) high/low-precision charges and a 3" form factor.

 

Turret side armour array:

  • Two layers of L-ERA sloped at ~30’ in the horizontal
  • Base armour: 1" (25mm) RHA, sloped at ~30’ in the horizontal
  • 1" (25mm) composite, sloped at 30’ in the horizontal
  • KE: 5.9" (150mm) at 30’ from side.
  • CE: 13.4" (340mm) at 30' from side. Maximum angle that side can resist 7" CE is ~20' from the side (70' from the front).

 

 

Turret rear:

  • 2" (50mm) RHA

 

Turret roof:

  • 1" (25mm) RHA

 

Hull upper front:

  • Two layers of L-ERA, sloped at 75’
  • Base armour: 1" (25mm) RHA sloped at 75’
  • 2.2" (55mm) composite, sloped at 75’
  • KE: 16.9" (430mm)
  • CE: 89" (2250mm) vs single-charge. Tandem charge rated to penetrate both layers via precursor is something like 17.9/11.4" (455/290mm), corresponding to 3" high/low-precision charges and a 4" form factor.

 

Hull lower front:

  • Base armour: 1" (25mm) RHA sloped at 45’ from vertical
  • 4.2" (106mm) composite, sloped at 45’ from vertical
  • KE: 7.3" (185mm)
  • CE: 7.5" (190mm) vs single-charge.

Notes: the area next to the driver contains two fuel cells and two protected storage areas for ammunition. Hits here are correspondingly much more protected than the above would indicate, for both the upper and lower hull.

 

Hull side:

  • 2 x L-ERA layers
  • Composite skirt: 0.2" (5mm) HHA with a 0.8" (20mm) textolite backing
  • 1" (25mm) aluminium roadwheel (depending on hit location)
  • 29.5" (750mm) air gap/fuel (depending on hit location)
  • Inner skin: 1" (25mm) RHA
  • KE: ~3" (75-80mm) (normal) / ~8.2" (190-225mm) (30’ arc from the front)
  • CE: ~3.8" (95-100mm) (normal) / ~30" (690-860) (30’ arc from the front)
  • Immunity zone against 15.7" KE: 21’ arc from front
  • Immunity zone against 7" CE: 54’ from front (36' from the side)

 

Notes: the upper hull side has numerous armoured brackets to hold the skirt. These would be expected to be hit when the impact is from the 30' arc, which would significantly improve protection.
 

Belly:

  • 1" 25mm RHA
  • 0-0.8" aluminium

 

Notes: the suspension units are aluminium boxes, the torsion bars are modelled as 2.75" (70mm) bars and each swing arm is attached to a hollow steel tube. The mine protection for the floor of the vehicle is accordingly expected to be much higher than these figures would indicate.

ZUANVSE.jpg

f0s5am8.jpg

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After finishing up on Derebus, the good folk at Para-allful Conglomerated decided to make a simplified model for the more down-scale customer:

lAfq1xi.jpg

The Derebus-M uses the 4" 40 cal low-pressure gun in an all-new turret. This, along with removing some of the nice-to-haves such as the coincidence rangefinder, complex fire control system and composite internal armour panels, allows the Derebus-M to be made cheaper, simpler and a bit lighter.

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15 minutes ago, Sturgeon said:

On the Derebus, it looks like the gun could be lowered a bit? That might save some height & mass.

 

Also what is your recoil stroke? For an MBT, 14-16" is pretty normal I think.

Recoil stroke is more or less exactly 14" (350mm). It might be worth trying to lower the main gun - IIRC the height was originally set so as to allow clearance for a tall hull periscope and to let the hatch rotate forwards. In the event I decided that the driver would prefer to open the hatch to look out of, so the hatch opens the other way.

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1 hour ago, Sturgeon said:

On the Derebus, it looks like the gun could be lowered a bit? That might save some height & mass.

 

Also what is your recoil stroke? For an MBT, 14-16" is pretty normal I think.

Thanks, that saved about 100kg...

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I'm basically ready, I just need to correct my mantlet because LMAO cleft turret and late modeled autoloader. So I might need one more day.

 

Toxn's tank looks really good, nice weight management.

Edited by Sten
Bees don't like sad camels, why do you want a reason for eddit?
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Final entry: Derebus-M

 

ykUMkdL.jpg

 

Main dimensions and statistics

 

Manufacturer: Paramount-Allen-Fullerton (Para-allful) Conglomerated

Mass estimate (as based on CAD model plus ~5830lb to account for drive systems, crew amenities, ammunition and miscellaneous components): 40.5t (36.8mt) fully loaded, fueled.

Armour mass (1-3.15" (25-80mm) RHA base plus ERA, composites, side skirts and engine bay liner): 21.5t (19.5mt)

Calculated mass: 41.9t (38mt)

Crew: 4 (commander, gunner, loader, driver)

Length: 246" (6.25m) hull, 261" (6.62m) total 

Width:  150" (3.8m) with skirt

Height: 86" (2.19m) to top of commander's hatch, 91" (2.30m) total

 

rTu3Mee.jpg

 

Firepower

 

Note: the armour used for the target has the same hardness (360BRN) as the armour used in the vehicle. The target was at 0 degree obliquity for calculation purposes.

 

Main gun: 102mm L/40 “4-inch 40 calibre” low-pressure gun:

“Low-pressure” = 310 MPa/3.45MJ

“Emergency” pressure = 345MPa/3.83MJ

Recoil stroke: 300mm

Vertical travel: +20/-10’

 

Ammunition:

  • 23.9lb (10.85kg) HEAT-FS, penetration of around 16.9" (430mm) using 122mm BK13 derivative (337mm if using BK13 penetration), 2614fps (797m/s).
  • 26.2lb (11.90kg) HE, 2.92kg fill, estimated blast penetration of ~1.4" (35mm) RHA, 2496fps (761m/s).
  • Simple APFSDS (15:1 LD, 550BHN monosteel body, tungsten insert, 76mm cap, ring sabot): 1x15.2" (26x387mm) rod, 0.55/3.4" (14x86mm) insert, 3.4/1.9lb (1.53/0.84kg) penetrator/sabot mass, 1800m/s, 10.3/9"(261/228mm) penetration at 100/2000y. Uses emergency pressure.

 

  • Case: 4x19.7" (102x500mm) steel case, 4.7" (120mm base), OAL (HEAT-FS) = ~28" (700mm)
  • Charge weight: 4.9lb (~2.2kg) standard, 5.4lb (2.46kg) emergency
  • Case weight: 11.5lb (5.2kg)
  • Overall weight (HEAT-FS): 40lb (18.25kg)

 

Note: if following the design of 3BM-26, this could be higher in practice. Using DeMarre the estimated penetration is 10.8" (274mm) at 2000y.

 

Storage:

21 rounds stored in an armoured storage bin in the turret. The bin exhausts through blow-off panels in the turret side and roof.

36 rounds stored in armoured bins on either side of the driver behind the fuel cells, with blow-off panels in the hull side and front

 

Secondary weapons: 

.30cal/7.62mm MG as coax

Both the commander and loader’s hatch rotate and have mounts for .30 cal MGs.

 

Fire control:

Single axis stabilized gunner’s sight (of the same configuration as Derebus).

Backup 60mm telescopic sight mounted to mantlet.

Duel axis stabilized main gun.

LRF (of the same configuration as Derebus) mounted above barrel.

 

YAmq6Z8.jpg

 

Mobility

 

2xV6 liquid-cooled diesels, 19l displacement each: 290hp/ 216kW each, 553kg dry weight each.

Combined output to hydraulic torque converter, feeding into Merritt-Brown-style double differential system.

The engine, transmission and cooling system all sit in an aluminium tub that fits into a bay in the rear of the vehicle. This can be removed entirely for servicing, or to replace the powerpack with a different configuration.

Suspension: 20" (0.5m) ground clearance, geared torsion bar suspension, each axle pair in detachable units shrouded by aluminium housings. Wheels are 23.6" (0.6m) in diameter, with a track width of 27.6" (0.7m) and a pitch of 7.7" (0.195m).

PWR: 13.8 HP/t (11.4 kW/mt)

Fuel load: ~2550lb total (793lb/360kg in tanks flanking the driver, 1764lb/800kg in rear sponson tanks, range of 540mi at 30mph

Ground pressure (calculated MMP): 28.4 PSI (196 KPa). 

Track contact length: 153.5” (3.9m)

Track contact area: 58.8ft2 (5.46m2)

Nominal ground pressure (using calculated mass): 9.86 PSI (68KPa)

 

yQKcJMt.jpg

mfZ3ayB.jpg

 

Protection

 

 

Notes:

Mounting bolts for ERA layers are not modelled, but are accounted for.

The covers over the rear fuel cells are 1" RHA.

 

Turret front:

Two layers of L-ERA, sloped at 75’

Base armour: 3.15" (80mm) RHA sloped at 75’

KE: 18.3" (465mm)

CE: 104" (2650mm) vs single-charge. Tandem charge rated to penetrate both layers via precursor is something like 17.9/12" (455/305mm), corresponding to 3"/3" high/low-precision charges and a 4" form factor.

 

Turret cheeks:

 

Note: because of how the cheeks are sloped, protection actually drops off the closer you get to the 25’ arc.

 

Three layers of L-ERA sloped at 25’ in the horizontal

Base armour: 3.15" (80mm RHA), sloped at 25’ in the horizontal

KE: 12" (305mm) from the front

CE: 56" (1425mm) (normal) vs single charge. Tandem charge rated to penetrate both layers via precursor is something like 12.2/7.3" (310/185mm), corresponding to 2.1/2.4" (55/60mm) high/low-precision charges and a 3" form factor.

 

Turret side armour array:

Two layers of L-ERA sloped at ~30’ in the horizontal

Base armour: 1" (25mm) RHA, sloped at ~30’ in the horizontal

KE: 5.9" (105mm) at 30’ from side.

CE: 13.4" (215mm) at 30' from side. Maximum angle that side can resist 7" CE is ~58' from the side (32' from the front).

 

 

Turret rear:

1.38" (35mm) RHA

 

Turret roof:

1" (25mm) RHA

 

Hull upper front:

Two layers of L-ERA, sloped at 75’

Base armour: 3.15" (80mm) RHA sloped at 75’

KE: 18.3" (465mm)

CE: 104" (2650mm) vs single-charge. Tandem charge rated to penetrate both layers via precursor is something like 17.9/12" (455/305mm), corresponding to 3"/3" high/low-precision charges and a 4" form factor.

 

Hull lower front:

Base armour: 5.15" (131mm) RHA sloped at 45’ from vertical

KE: 7.3" (185mm)

CE: 7.3" (185mm) vs single-charge.

Notes: the area next to the driver contains two fuel cells and two protected storage areas for ammunition. Hits here are correspondingly much more protected than the above would indicate, for both the upper and lower hull.

 

Hull side:

2 x L-ERA layers

25mm RHA skirt

1" (25mm) aluminium roadwheel (depending on hit location)

29.5" (750mm) air gap/fuel (depending on hit location)

Inner skin: 1" (25mm) RHA

KE: ~3.5" (85-95mm) (normal) / ~9" (210-245mm) (30’ arc from the front)

CE: ~4.2" (100-115mm) (normal) / ~32" (730-890) (30’ arc from the front)

Immunity zone against 15.7" KE: 21’ arc from front

Immunity zone against 7" CE: 56’ from front (34' from the side)

 

Notes: the upper hull side has numerous armoured brackets to hold the skirt. These would be expected to be hit when the impact is from the 30' arc, which would significantly improve protection.

 

Belly:

1" 25mm RHA

0-0.8" aluminium

 

Notes: the suspension units are aluminium boxes, the torsion bars are modelled as 2.75" (70mm) bars and each swing arm is attached to a hollow steel tube. The mine protection for the floor of the vehicle is accordingly expected to be much higher than these figures would indicate.

 

bv1RAou.jpg

0sWKOkd.jpg

 

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Still chipping away at the Brahman, just about ready to start modeling the armor. 

u6pJmLC.png

Spoiler

DS2sACm.png

 

If you're wondering how I'm going to protect the inlet and outlet to the engine, I'm going to use the same trick I used in the californium competition to protect the holes in the side, but slightly thicker. 

 

The plate above the engine is the radiator, which additionally has a 2 inch gap above and below it, where air is forced across it, to cool it. The exhaust and coolant air are both passed through the turbo charger, then through a CV90 type system, to cool it down and hopefully reducing the thermal signature. 

 

I'm going to access the engine and transmission via a similar system to the Merkava 4: the upper plate lifts up, using 2 hydraulic pistons powered by the tanks batteries; or if you need to pull the engine and tranny, you can lift off the upper plate with the same 5+ ton crane you need to lift the drive train. 

 

 

I need a little help, I don't know how to model a "modern" commanders cupola, with all the amenities, without making it too damn big. 

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1 hour ago, Lord_James said:

I need a little help, I don't know how to model a "modern" commanders cupola, with all the amenities, without making it too damn big. 

Use a low hexagonal prism as an all around periscopes

293px-Hexagonal_Prism.svg.png

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Math for mass:

wvSsLze.png

 

HJ3syqW.png
 

10227.98 kg turret armor + 16719.91 kg hull armor = 26947.89 kg

26947.89 kg * 0.45 = 12126.55 kg required mass of suspension components

12126.55 kg + 26947.89 kg = 39074.44 kg

My accessories, fittings, fuel, crew, etc weigh 38,970 lbs or 17,673.47 kg, so:

39074.44 kg + 17,673.47 kg = 56,747.91 kg, or 62.57 short tons.

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