Toxn

The sky's the limit, bud. You go make the 188-tonne tank with two main guns that you've always been dreaming of.

Tiger has similar issues though - that tub and superstructure design philosophy means that the 80-100mm upper box is riding on a 25-60mm lower hull.

Cross-posting a bit, but I found this interesting: I was modelling a Tiger 1 analogue for the Californians as a prelude to suggesting the above competition options, and found that the cost of the front drive system, slightly taller engine and hull sponsons ends up being 10 tonnes of weight (for the same protection level and an otherwise-similar component layout) by the time you get to the final weight of the vehicle. It's amazing how much extra you pick up just from having a taller hull, because of course side armour is one of the more weight-expensive parts of a tank due to the area it occupies. Sponsons are also one of the great enemies of weight saving because they increase roof area and front plate area at the same time. Finally; squaring off the hull (rather than angling it a bit to wrap around internal components better) seems to gain you a small but noticeable amount in the weight department. All this, combined with the fact that you generally want a longer tank rather than a taller or wider one for ground pressure reasons (more track run), means that the best way to economise is simply to follow the Soviet model: make your vehicles as low and thin as possible as possible, and make up internal volume with length if you need to. This is how you end up with T-54/55 having 200mm of RHA on the front, a minimum of 80mm on the side, a potent 100mm gun, and a weight of only 36mt.

I'd maybe set the date as 1960-65. Other than that - I actually had a friend in varsity who ended up doing this in the mid 2000s for T-62s...

What's the weight of the bare hull and turret plus the armour components?

Give it a think - we've got time to chew over this stuff in any case.

How improvised? If we're talking 1920s tech then I'm all for it.

Mini-competition suggestions, for consideration some time next year: 1. Design an AT gun (2239) In this mini-competition, contestants would be asked to design a conventional, WW2-era AT gun for use by one of the post-apocalyptic US polities. The gun would be designed with an understanding of how weapon and armour technology would be likely to develop, and should include a description of the gun itself, its mounting and its ammunition. 2. Design a ATGM (2247) In this mini-competition, contestants would be asked to design an ATGM for use by the Texans, in a project running parallel to their first forays into MBT building. The contestants would have to simulate the overall configuration and aerodynamics of the ATGMs using OpenRocket, and would have to provide a coherent explanation for the warhead layout and control scheme. Submissions would be in the form of ORK files and a brief description. 3. "Fix a tank" 2 - France, 1946 The second "fix a tank" competition, this time to try and fix the problems that the French had with their post-war Panthers. The contestants would not be allowed to radically re-design the vehicles (or, at least, would have to provide better and better justifications for each new change), but would try to work with what they had to fix as many issues as possible. The goal would be to produce a vehicle that the historical 501st and 503rd armoured regiments could operate into the 1950s. 4. "Fill in the blanks" - design the Californian heavy from the first (2239) competition The Californian heavy tank (which was very obviously an expy of the WW2-era Tiger) was the vehicle which kicked off the entire arms race that has become the dominant narrative of the post-apocalyptic competitions. A cryptic beast, it was described as weighing 50mt, having 76mm of armour and being armed with an 89mm gun that can penetrate ~140mm of RHA at 1000m. This competition would involve contestants filling in the blanks to create a tank that fits these criteria (ie: not inventing a vehicle with a better gun, massively thick armour etc). The submissions would be done using a formula approach (for which, see here) with the contestants being asked only to model the hull/turret armour layout in detail (ie: in terms of mass). Everything else (the gun, ammunition, suspension, engine, optics etc.) can be simply a visual representation with standard weights being applied for variable-weight components. The submission would be in the form of drawings (front, side, top view) and a description to follow a standard format.

Main Battle Tank, 2247, project names "Derebus" and "Derebus-M" Manufacturer: Manufactuer: Paramount-Allen-Fullerton (Para-allful) Conglomerated Table of basic statistics: Note: all statistics provided are for Derebus unless otherwise noted. Parameter Value Mass, combat Armour mass: (1-2" (25-50mm) RHA base plus ERA, composites, side skirts and engine bay liner): 20.6t (18.5mt) 43.1t (39.1mt) modelled, 43.4t (39.4mt) calculated Length, combat (transport) 246" (6.25m) hull, 379" (9.63m) total Width, combat (transport) 150" (3.8m) with skirt Height, combat (transport) 95" (2.41m) to top of commander's hatch, 109" (2.77m) total Ground Pressure, zero penetration Ground pressure (calculated MMP): 29.4 PSI (203 KPa). Nominal ground pressure (based on calculated weight): 10.3 PSI (70.77 KPa) Estimated Speed 37 mph (60km/h) Estimated range 490 mi at 30 mph Crew, number (roles) 4 (commander, gunner, loader, driver) Main armament, caliber (ammo count ready/stowed) 5-inch 55 calibre (127mm L/55) high/low pressure gun, (19 charges, 9 active projectiles, 10 inert projectiles in turret/ 16 charges, 8 active projectiles, 8 inert projectiles in hull) Secondary armament, caliber (ammo count ready/stowed) 3 x .30 cal MG (600 rnd belted each ready/ 1200 rnd belted each stowed) Vehicle designer’s notes: The Derebus family of vehicles (provisionally named Derebus and Derebus-M) are intended to fulfil a procurement strategy emphasizing mobility (tactical, operational and strategic), reliability and superb value for money, achieved using a lightweight vehicle design, proven automotive components and a high/low capability mix. Derebus sports a state-of-the-art fire control system allied to a powerful 5" gun, while Derebus-M provides supporting firepower and a larger ammunition load thanks to it's 4" gun. Both vehicles provide superb protection across their frontal arcs, with the Derebus making use of cutting-edge composites to save weight. Both Derebus and Derebus M are immediately available to fulfil all of your defense needs. Vehicle feature list: Mobility: 1. Link to Appendix 1 2. Engine- V-12 Diesel (Kharkiv V-2-55 derivative), 2441 ci (40l) displacement, 600HP (448kW), liquid-cooled. Note: alternate engine and transmission arrangements are provided for in Appendix 3 3. Transmission - hydraulic torque converter feeding into Merritt-Brown-style double differential system, 7 forward/1 reverse gears. 4. Fuel - diesel, ~2400lb total (639lb/290kg in tanks flanking the driver, 1764lb/800kg in rear sponson tanks, estimated range of 490mi at 30mph. 5. Engine, transmission and cooling are arranged in removable aluminium tub housed in engine bay. The tub is removable by sliding out the rear of the bay. 6. Suspension - torsion bar, variable travel (presently 11.8" (30cm)), 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). Survivability: 1. Link to Appendix 1 2. Link to Appendix 2 3. Non-specified survivability features and other neat tricks - highly sloped turret and hull front (75 degrees), charges and active ammunition (HEAT-FS and HE) arranged in sealed tubes leading to a blast chimney that outlets to blow-off panels in the turret roof, turret sides, hull roof and hull sides. A. Weapons: 1. Link to Appendix 1 2. Main Weapon- a. Type: smoothbore, vertically trainable +15/-10 degrees b. Caliber: 5"/127mm c. ammunition types and performance: 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. HEAT-FS (low-pressure setting): 46lb (20.85kg), penetration of around 21" (535mm), 3074fps (937m/s). HE (low-pressure setting): 46lb (23.2kg), 201oz (5.7kg) fill, estimated blast penetration of ~55mm RHA, 2910fps (887m/s) APFSDS (high-pressure setting): 15:1 LD, 550BHN monosteel body, tungsten insert, 115mm cap, ring sabot, 1800m/s, 15.7/13.8" (400/350mm) penetration at 100/2000y (lower estimate, 17.1" (435mm) at 2000y upper estimate). d. Ammo stowage arrangement - 19 charges, 9 active projectiles, 10 inert projectiles in turret; 16 charges, 8 active projectiles, 8 inert projectiles in hull. e. FCS: Duel axis stabilized main gun 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. f. Neat features: 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 historical 125mm 2A26 gun), matching the length of the HEAT-FS round. The 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 storage tubes as the high-pressure charges. 3. Secondary weapons - 3 x .30 cal MG, 1 coaxial, 2 in mountings attached to the commander and loader's turret hatch 4. Link to Appendix 3. B. Optics: 1. Primary gunsight: single axis stabilized gunner’s sight 2. Secondary gunsight: vertical coincidence rangefinder (stadiametric, 39.4" (1m) base), doubles as a redundant back-up sight. 3. Miscellaneous optics: Commander and loader's rotating hatches, including vertically trainable (+/- 15 degrees) periscope in front of hatch, degree markings on hatch ring to allow rough direction of gunner to target. Driver's periscope, vertically trainable +/- 15 degrees C. FCS: 1. List of component systems, their purpose and the basic system architecture: 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). LRF mounted above barrel, solid-state components, maximum operating range of 5km in clear conditions, average estimation error of 1%. Uses 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. 2. Link to Appendix 3. Fightability: 1. List vehicle features which improve its fightability and useability: Engine bay approach simplifies engine and transmission replacement via rear bay doors. Generous rear hull roof hatches simplify servicing and maintenance. Bolt-on suspension units simplify field replacement and repair. Commander and loader's hatch design improves buttoned-up visibility Additonal Features: See Appendix 3 Free expression zone: "...bellicis"

Good going! We'll look forward to your entry.

Looking svelte.

I can't promise that I won't try to make an SPG or something on the same hull, but that should be it for now.

Final entry: Derebus-M 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 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. 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) 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.

Thanks, that saved about 100kg...