Building a tank to fight a mech

Question

Tanks are better than (realistic) mechas. This is an unavoidable truth. However, whenever they appear in general fiction, mechas tend not to be overtly realistic. Still, plenty of the points argued for the benefit of using tanks are indisputable. They are lower to the ground, carry a bigger gun, and can probably move faster than a mecha if they 'floor it'.

So, in my setting, the aristocratic nobility of this world has overthrown the rebel forces using highly unrealistic mecha (think Mazinger-Z and Getter Robo rather than Gundam). They then oppressed the masses, sending society back into their own 'romanticized' version of a feudal society, and destroying all modern machinery besides their own super-powered warmachines.

The question isn't really about those super robots, however. The peasantry and common folk have been given access by the nobility to small, more realistic robots, with which to fight their wars and do their heavy lifting. This question will be mostly about these tiny robots, specifically the ones used by the lower ranking soldiers.

A group of rebels, armed with 'Ancient Forbidden Knowledge', are trying to build tanks. What would be the best way to design these tanks to fight the common small mechas?

The capabilities of the small mecha:

1. They are mostly round and angled, to provide resistance to firearms (think sloped plate)
2. They have small stumpy legs, but are capable of moving surprisingly fast when they sprint, and jumping something like 15 meters or so (not taking into account any customisations).
3. The most common firearm they have is a 40mm autocannon that is shaped like and functions like a modern automatic rifle.
4. They carry swords. These are mostly decorative, but are still a heavy sharpened bar of steel.

The tech level for the rebels should be current era or at most 20 minutes into the future. They cannot afford to make mobile gun platforms that trade deaths with the nobility, because they are the ones who are outnumbered.

EDIT: Limitations: As suggested by a comment by @VilleNiemi, a few limitations will be placed on the rebels' tank building capability:

1. They are capable of producing certain industrial parts by stealing into nobility-owned factories at night, but not en masse, due to the risk of being detected.
2. They probably get most of their components by salvage or underground trade.

This means that things like Depleted Uranium Shells will be very rare and very very hard to get more of. The tanks can and should still be treaded though, as that is part of their strength in comparison to the mechas.

Answer 1

To defeat small, agile mecha armoured with 40mm repeating cannon, we need what would effectively be a medium tank, not quite a main battle tank. Medium tanks have lighter armour, though the composites used would still be capable of resisting repeated 40mm cannon hits from any aspect. With lighter armour, add a large gas-turbine engine to give the tank a good power to weight ratio and a high speed, capable of outrunning the mecha if not necessarily outjumping them. Ensure that the tracks are well protected by armour skirts.

As to armament, mount a heavy, large-calibre gun. The 120mm smoothbore cannon used by US tanks, along with the computer-assisted aiming mechanism means that as long as the target is properly tracked prior to firing and the range is sufficiently low that the target cannot dodge effectively, the shot will not miss. A hit from a 120mm cannon round, loaded with a depleted uranium penetrator or even just a shaped charge explosive will instantly wreck any mecha designed to take on opponents armed with 40mm cannon, probably turning it into a collection of ballistic limbs. As long as the turret traverse and elevation mechanism has some heavy-duty power assistance, it should be able to track any mech at any reasonable range. A lighter, older 105mm or even 88mm cannon should still be able to wreak havoc on such a lightly armoured mecha, and would allow more shots.

Given the strength of composite armour, while not capable of withstanding a 120mm cannon shell, it would still be well up to the task of resisting multiple hits from 40mm shells and big sharpened crowbars. Also, given the acceleration and weight of the tank, at close range, the tank could be used as a battering ram, and running over a mecha would probably cause a mission kill, if not a total kill.

An alternative weapon system, if the tankers expect to face large numbers of mecha with relatively few tanks, would be the GAU-8 30mm gatling system found in antitank aircraft. This weapon's high rate of fire would be ideal for mowing down massed charges by mecha, and while one hit may not incapacitate a mech, the multiple hits such a system would allow likely would.

The weakest point on such a tank would be the tracks and personnel hatches, though it would not be a difficult matter to armour and shape the hatches so that they would present minimal edges to be levered up by the mecha's swords, and could resist 40mm rounds quite well. With low armoured skirts, the tracks could be made to be a small target, and even when immobilised, a tank remains a difficult target to neutralise, unlike a mech.

To achieve some degree of stealth, a tank can be relatively easily waterproofed and hidden in any reasonably large body of water, with only a periscope showing above the surface. Given the ground impacts that mecha movement would cause, there would be relatively little need even for a periscope if the tank was equipped with seismographic equipment. Alternatives for stealth would be to cover the tank with the branches of dense shrubs for a forest setting, or hay in a rural setting.

Answer 2

Basic warfare is to have multiple kinds of units, with different capabilities, supporting each other. Unless you have magic, big firepower weapon will inevitably will be heavy and less maneuverable than light weapon.

So best weapon against your mecha would be something like BMP:

• light tank (with gun),
• which is amphibious (can cross lake which your mecha cannot). Can jump to water with no preparation,
• has laser-beam riding anti-tank (and anti-mecha) missiles,
• can hold 7 infantrymen, who can disembark, penetrate terrain which is hard for tank, and protect it, say by killing mecha by RPG
• very mobile - forest from young trees (or legs of mecha) will not stop it - sharp nose (see BMP-2 photo) will cut it with surprising efficiency, can go fast (up to 45 km/h off road, 70 km/h on road)

If you can have it, add A-10 "Flying tank" designed for close air support (not dog-fighting/interception, not bombing, but close support of infantry on battlefield, killing stuff like your mecha from air). Or anti-tank Apache helicopter

How you fight mechas?

Group of BMP will move into battle area, infantry will dismount. Mechas far away will be killed by BMP's cannon and/or guided missile. Anything closer will be handled by infantry, which has machine guns and another excellent anti-mecha weapon: rocket-propelled grenade - which is cheap, easy to make and hide, fits perfectly to your scenario.

So BMP+7 infantry units has much greater firepower than mecha: cannon + 2 or 3 RPGs + 4 or 5 machine guns + personal grenades. Much cheaper to equip (especially if you have lots of manpower and limited manufacturing), and more modular: easier to replace damaged parts.

If you have extremely limited manufacturing, you can scale down: 4x4 pickup truck

Slightly up-armored civilian 4x4 pickup + your infantry with RPGs and machine guns. Toyota Pickup Truck Is the War Chariot of the Third World. That would be ideal against enemy army with overwhelming technological advantage, as US army found very painfully in Iraq and Afghanistan. Truck is cheap, reliable, fuel efficient, and 6-8 infantry provide lots of firepower (with RPG and anti-aircraft machine gun mounted on truck). And it has stealth capabilities: looks almost exactly like civilian truck, so it can hide in plain sight.

Read links above about Toyota war - how Toyota truck provided mobility to Chad forces to successfully fight and destroy "superior" Libyan army armed by tanks.

To support slow mecha against your more mobile pickup truck chariots, enemy would need air superiority. And again, MANPADS like Stinger missile can be easily added to your arsenal. and be devastatingly effective against low and slow flying aircraft. Unless your enemy has A10, because A10 can absorb ridiculous amount of damage and fly another day.

Or, as kung-fu sensei says: speed defines the master - and can beat superior, but clumsier, firepower.

Answer 3

Make a tank with a flat top, a bunch of vertical launching tubes and use fiber-optics guided missiles to take on the mechas. They will not even know what hit em.

Missiles like the brazilian FOG-MPM can hit targets 32km away, they are guided by a camera in the nose that relays imagens to the station via a fiber optic. Commands are sent upwards from the command station via the same fiber.

You can use those missiles to scout (spending then) for the sake of its camera, to shot low flying helicopters, to sink incomming speedboats at beach etc. A mecha is no harder target than those.

Something like a armored car with 8x8 traction and a flat top, a row/column of missiles in the middle area and driver plus weapons officer is all that it takes. Heck such a vehicle, added to a infantry battalion might take on even on modern, heavy armored tanks due to its top attack capability.

Using movement detection radars would pinpoint the quick and jumpy movement of a mecha. Infantry would provide screening at the front, allowing the armored vehicles to hide behind cover and launch missiles at will.

Even if the mecha is quick and moves by jumps and tries to dodge the incomming missile, a mecha is no more agile than an helicopter, yet helicopters can and will be shot down by such class of missiles.

Answer 4

Take a lesson from Iraq: Command detonated explosively formed projectiles. Since you're talking a higher level of sophistication than most of our opponents had over there it will be much easier. Put a camera on the charge so it can see exactly what's in front of it, the operator only pushes the button when he sees a mech in it's sights.

It's extremely hard to defeat the plasma jet of an explosively formed projectile. Reactive armor works against man-portable missiles because their charges are very short range--the armor destroys the missile before the jet is fired. When you don't need to send it after it's target on a tail of fire you can build it bigger and longer ranged.

Answer 5

Tanks have two advantages over mechs straight up. Cost and terrain

Tanks are far simpler to build thus cheaper to make. The Russian tanks were built three to one against the Germans. They cast the armour instead of forging it and only supplied each tank with three shells but there was much bigger army and the Germans got overwhelmed despite having the superior tank.

Tanks are also better at moving over poor terrain. A tank can churn through a muddy field or sandy beach or over loose rocky ground but a mech puts all it's weight on it's feet which is a much smaller surface area so will sink into the ground or roll it's ankle or trip like humans do on a loose surface.

That means a tank army can ambush the mechs and then flee across muddy fields to escape.

Just as a side note, rebels aren't likely to build tanks at all. Tanks (or mechs) are the domain of a standing army. Tanks are loud, noisy and hard to hide. Rebels would ambush mechs and vanish into the civilian population. Why build a tank when you can fill a car with explosives and take out several mechs? They could lure then into pit traps or attach limpet mines to the knees and then napalm them to burn out the pilots.

Rebels can do a lot of damage to a standing army without much tech at all.

Answer 6

Given the speed and jumping ability of the mecha...

I'd go for a heat-seeking missile, and shoot at them from range.

Why?

• A missile is still faster than a mech (this is an assumption, but a safe one),
• Distance means you can avoid being stomped on, or stabbed, entirely,
• Distance also gives you some safety against that 40mm gun,
• And it follows a target that tries to dodge.

The rebels are going to be employing guerilla warfare, so ambushes are the proverbial par-for-the-course. Don't expect a lot of honourable combat. Catch people(mecha) that are by themselves, or not paying attention. If there's any serious risk faced by the rebels, their most logical action is to slip quietly away.

If heat-seeking is beyond the rebels' capability, go for laser-guided.

Answer 7

Considering these tanks are to be built by scavenging and stealth, I would make some pretty extensive modifications to make it more reasonable to pull off. After all, designing, building, and then supplying modern armor is a huge task even if you're doing it with trained engineers in dedicated facilities.

But doing it in secret means you won't have access to advanced weaponry, most likely. Instead I'd pick a base chassis that resembles a giant bulldozer. Thick plating all around, and a massive extra pusher at the front, preferably with as little clearance as you can get away with. Then, you just try to run the mechs down. Since your front is just thick armor, there's not much their light weapons can do and no mech is going to outrun a threaded bulldozer.

At worst, you'd have to deal with highly mobile enemies, but if you're trying to run them down, they are already on the defensive, and their weapons aren't very effective. It's way cheaper and easier to build and even if it's not as powerful as a real tank it's much more reasonable to be pulled off in secret.

You can support such vehicles with light infantry weapons, as the shock power of a dozer would have enemy vehicles on the defensive enough that you wouldn't be in as much danger. Or you can mount them on/in the tank as you collect them. Since the Mechs are designed to combat each other, mounting their scavenged 40mm turrets on the dozer would probably be enough.

An additional advantage: if you are the rebels, you'll want to use the element of surprise as much as possible. Nothing screams "surprise!" like driving in straight through the wall.

Answer 8

would this be something you'd be looking for? Its a vehicle from the direct to DVD anime called Appleseed, it seems like a good reference to your world:

GUNSLINGER TANK
A tank more suited to the urban jungle than to the badlands. It carries a variety of weapons to get the job done, but under adverse conditions its electronics and cooling systems have been known to malfunction. Depending on the terrain the Gunslinger can switch from tread to tire, to make maximum control of its environment.

Top Speed:60 mph
Crew:3
Range:230mi
Passengers:4
Cargo:4 tons
Type:IFV
Mass:20 tons

Special equipment: Reactive armor, amphibious modification, fire extinguisher, environment control, military radio w/scrambler, anti-personnel grenades, visual and laser rangefinder, auto pilot and navigational system, image enhancement, thermograph, 4 IR smoke projectors, radar, motion detectors, spotlights and enhanced audio detectors.

Weapons systems: 30 mm Gatling in turret mount, 6 shot revolver style 75 mm cannon, in turret mount.

Answer 9

Is this group of rebels on equal footing with the government they're rebelling against? If not, why are they attempting to fight a conventional war, with unit vs. unit? The goal of a war isn't to destroy the other side's army, but to destroy the other side. The tanks should be very mobile - able to escape from a battle quickly - and powerful enough to attack the non-mech military targets. The rebel's goal with the tanks should be to provide mobility to avoid a fight, firepower to destroy a target, and protection for the retreat from battle.

Answer 10

You would need to make an electric tank:

If this civilization has the ability to create mechas, and the rebels have limited access to the production facilities, then they have the ability to steal some very high tech equipment.

The drive train would be an 8 wheel tracked system driven by 250 hp permanent magnet electric motors on each wheel.It would have 2000hp in total. These would be easy to get access to because normal motors would burn out much easier and be replaced so the mechas would need to use some sort of permanent magnet motor which is much more rugged and reliable with a longer service life. The vehicle would have a lower heat signature, it would make much less noise and the drive train would be less mechanically complex owing to the fact that the motors not only take up less space, but have fewer moving parts and reduce the need for a large engine block. The fact that there are multiple drive systems means the vehicle can move even if one or two of the wheels are hacked off. The motors would also be much lighter than a massive engine. The axles of the motors would have miniature electrical generators attached so that the vehicle can partially recharge as it moves. Due to the advanced pneumatics and hydraulics used in a mecha the ability to make a pneumatic suspension system would be there, unless they opt for a cheaper one similar to the one in the merkava.

Power would be stored underneath the floor of the tank (between the floor and the underbelly armor) in layers upon layers of paper thin graphene super capacitors. These would propbably be used in the mechas due to the need for a compact power storage solution. They can recharged in as much time as it takes to fill a gas tank and can be discharged very quickly in case of a lower hull breach. This negates the need for a huge tank (no pun intended) containing volatile fuel. On the motors to cool them down is a system of solid state thermoelectric panels that absorb most heat emitted and turn it to electricity, same with other heat producing components, these could be found on mechas also if they have a compact cooling system.

Since the ability to manufacture composite armors is not there I do have an alternative. The chassis of the tank itself would be made of steel, titanium, or high grade aluminum similar to that of the M109 paladin whichever is available. Over top of the chassis would be plating of alternating layers of stainless steel composite metal foam, and steel RHA. stainless steel coposite metal foam is made by literally adding tiny hollow air filled metal spheres into molten stainless steel to create a foam, The material is extremely light and has a composition of 60-70% air. It can resist 800 degrees celsius of heat for over 30 minutes. It has high ballistic resistance, a single inch of this material can obliterate an incoming 7.62x45mm armor piercing round to dust with only a 8mm indentation in the backing. it also has a high resistance to radiation. The RHA will be there as extra reinforcement against kinetic projectiles. This lighter armor will allow you to place more armor without adding too much extra weight. The fact that the tank has no emissions reduces the need for vents in the back allowing the rear armor to be just as thick as the frontal. The bottom of the hull would be V-shaped to deflect mine blasts. The inside of the hull would be lined with kevlar or ballistic nylon to prevent shrapnel and spalling. The hull would also include a faraday cage of copper wire to protect against EMP. The tank would have armored skirts that are lower to the ground than normal. If you wanted to up armor the tank you could add porcelain panels over top to absorb impact. All viewports are made of nanocellulose, a plant derived polymer that is transparent, stronger than steel, and stiffer than kevlar.

The turret ring would be made of steel and driven by two electric motors using gears with pneumatic assistance. The ring itself would be coated in copper or a similar conductor to allow for power transfer between the turret and hull to allow for redundancy if the capacitor bank in the turret is rendered unusable. The turret is attached to the hull via magnetic seal to prevent it from popping off if lifted by a mecha. The main gun would be a 90mm coilgun. Coilguns are very reliable and they do not contain many moving parts. It would be about the same velocity or slightly faster than a standard 90mm cannon similar to that mounted on the M36 jackson. They are quite easy to manufacture as to the fact that handheld versions capable of killing small game and unarmored humans along with even semi and full auto versions are made by hobbyists from household parts. The guns themselves are much more efficient than railguns and do not have the problems of barrel wear and dont generate as much waste heat. They have no muzzle flash or report, and have much lower recoil than conventional cannons. There is a recoil absorption spring located behind the gun. The weapon is much more accurate than normal weapons due to the fact that the magnetic field keeps the projectile in the center of the barrel at all times without it bouncing around like in a normal weapon. The barrel itself is smoothbore, and the rounds are fin stabilized. The gun itself can be gyroscopically stabilized allowing it to fire on the move by taking a gyroscopic stabilization system from a mecha. It would have a coaxial 40mm cannon also taken from a mecha. A ballistic computer and laser rangefinder can also be taken from a mecha. Parabolic microphones taken from a mecha are hardwired to the computer so that they can hear the trajectories of incoming rounds and within a few seconds triangulate the position of where they came from. It also has 1-60x variable zoom optic for the gunner's sight, along with a thermal camera and laser rangefinder taken from a mecha. The tank can also have multiple video cameras dispersed around the hull to allow for improved situational awareness by the crew. The gun's ammo would be cheap to manufacture because it consists of mostly ferromagnetic metal slugs, or other ammo types with ferromagnetic sabots. The ammunition would have no propellant so it wouldn't be volatile unless you are carrying HE or HEAT, and has no casing so it weighs less and you can carry more of it. If the coils of the gun are properly insulated it could be fired underwater.

There is a crew of four men, a commander, gunner, driver, and a loader. The gunner and loader are in the turret, along with the commander. The driver is seated in the front of the hull. The extra space in the hull can be used to carry troops if you add a rear door, or it can carry extra ammo, and can serve as an impromptu living area for the crew. If you do not want to have to recharge your tank you can mount whatever magical powersource the mechas are using. It will have a hydraulically operated retactable bulldozer to steamroll the mechas. The tank will weigh in the 30 to 40 ton range. Its profile will be made slightly narrower than a normal tank to be able to traverse the narrow roads in this semi medieval setting.

this tank due to its quiet nature would be perfect for hit and run attacks against mechas from long range, even if a shell does not penetrate a mecha it will knock it over due to the high center of gravity, and could possibly deal with a noble. In a close battle this tank will have the distinct advantage that the small mechas won't be able to harm it unless they score a very lucky hit. Even if the nobles show up to battle, they may have a tough time fighting this thing because they will probably be using samurai syle tactics which are obsolete compared to the combined arms employed by the rebels.

Cheers :) enjoy my design before the engineers come and overanalyze it with pitchforks and torches.

Answer 11

If the rebels have to build out of scraps, mount missiles on Jeeps, pickups or SUVs.

The vehicles are fast and relatively mobile and may be found or bashed together from multiple damaged vehicles.

Also, decent missiles may be easier to build than the precision parts needed for an artillery piece. Also, once the missiles are fired, your vehicle is much lighter for getting away.

Answer 12

Without access to dedicated facilities, it's going to be exceedingly hard to make a viable tank. The industrial facilities that you're describing probably aren't going to cut it - to make the protection of a modern armoured vehicle requires the use of some fairly high-tech armour (steel plate is going to be like butter against a 40mm cannon round) and the ability to properly join such materials together (WWI tanks had big problems with bullets 'splashing' between joins in the armour.

Then you need the drivetrain - effective armour against a 40mm is going to require something akin to a modern main-battle-tank, at 50-odd tonnes of mass. This will need components designed for such machinery - maybe available if there is re-purposable machinery for construction or agriculture.

Weaponry is either:

• easy - just steal it of of the enemy (but why not steal the whole vehicle?)
• incredibly difficult - forging large-calibre gun barrels is one of the toughest tests in metallurgy, and far out of reach of hastily-repurposed factory equipment.

Targeting is also a concern if you want the tank to be a match for a mech which can presumably move and shoot simultaneously - stabilising guns was a big challenge for earlier tanks and a huge advantage when it was cracked.

TL;DR - only a few countries on Earth currently make tanks (maybe a dozen or so) and they have free and easy access to their own factories, decades of experience operating the machines and the luxury of long R&D periods. Making tanks isn't easy!

Your best bet for a believable reason to have tank vs mech might be if the rebels had a much more unrestricted access to factories, just not necessarily ones making the mechs. An unsupervised heavy-machinery factory along with a plant that can make hardened steel might be your best bet, just need to find them a source of weapons.

Answer 13

Underground or underworld trading could be quite dangerous. (Think about the Hob from the Hunger Games). If these knights were found out, then the limitations they face could cost them their lives. Just something to think about. Plus, if they're outnumbered by the nobility, then they're frankly stuffed.

So, in conclusion, they're outnumbered and their tanks are unreliable. It would take a miracle for them to win. Just saying.

Answer 14

A 40mm cannon is not every impressive by tank standards; early WWII models were typically 37mm-50mm ( 2pdr to 6 pdr), with the odd 75 millimeter game-changer like the T-34.

Given that mechs necessarily have light armor, they will not be geared up to dealing with anything that takes serious armor-piercing ammo.

So a 1940-vintage T-34 design, but with improved visibility and a few other upgrades, should give you all you need. Shells from German light anti-tank guns of the time just bounced off the sloped, high-grade armor, the 76 mm gun will demolish and mech with ease, and you have plenty of mobility if you need to go after the. Also has lower ground pressure than a mech so better in mud and snow, probably also better at gradients.

Given modern tech though, you couldn't build a tank; you'd use a swarm of smart bombs, EFP-carrying drones or similar , or even an tank-hunting helicopter if you wanted to be more retro. They key is hitting them from well outside the range of their puny 40mm nonsense.