So lets say a post-apocalyptic society that primarily uses steam to power everything wants to make war hammers that have their impact force enhanced through the power of steam. What ways could steam be used to basically enhance them?


  • Needs to weigh no more than 400 lbs.
  • Needs to be effective in hurting and killing humans, mega-fauna, and break through concrete and steel.
  • The more gears the better.
  • This society is post of the modern age so they will have access to things that the steam powered Victorian era wouldn't (not a requirement just wanted to make sure you know that).
  • Also should maintain a hammer-like shape.
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    $\begingroup$ Let's clarify - you don't want steam-propelled projectiles - you want steam-powered melee weapon? $\endgroup$ – Alexander May 21 '18 at 3:39
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    $\begingroup$ Who exactly is using this weapon, what is the primary target, what sorts of defences are available (i.e. why would you need a "steam hammer"), and what are the logistical requirements (i.e. do you need to carry a coal hopper with you, or does it run off a high pressure steam reservoir?). There is a lot of detail needed to answer this question. $\endgroup$ – Thucydides May 21 '18 at 3:43
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    $\begingroup$ @TimBII They would also have a miniature furnace on their back to supply constant heat to build up pressure and carry around a bunch of logs and charcoal to keep it going. It doubles up as a miniature bomb if anything fails or if its struck by the enemy. $\endgroup$ – Shadowzee May 21 '18 at 4:23
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    $\begingroup$ training instructor: "you over there private, repeat to me the sequence..." private: "Yes sir, check water level press the button, swing outward and top up!" $\endgroup$ – user6760 May 21 '18 at 6:53
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    $\begingroup$ Note that actual steam hammers aren't shaped like hammers. The same would most likely be true of steam "warhammers", if such a thing were even possible. At the very least, I'd expect it to work with a linear motion, rather than an angular motion (so more like a steam-powered punch than a hammer). Maybe a powered fist that kind of looks like a hammer when extended (imagine a piston with a broad head)? $\endgroup$ – Luaan May 21 '18 at 13:59

15 Answers 15


As @Keltari mentioned, you could have a steam-propelled hammer to deliver extra force behind your blows.

It's not quite a "hammer", but another potential idea would be to have the head be a long spike out of which high pressure steam is forcibly expelled into the target. This would cause at the least horrific burns and potentially an explosion as the steam pressure built up inside the victim. The steam would be triggered by a button on the base of the handle.

Imagine the Wasp Knife, but on a sledgehammer scale. The Wasp Knife is used for self-defence against sharks and other large nasties, so I imagine a larger version would work well on megafauna.

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    $\begingroup$ The spike could be inside the hammer head, steam would drive the spike forward into the target on hammer head impact and then the steam pressure is released through the spike for maximum damage and the spike is returned by the steam buiulding up pressure again. $\endgroup$ – BentNielsen May 21 '18 at 10:01
  • $\begingroup$ could you combine them to make a large hammer that does both? $\endgroup$ – Amoeba May 21 '18 at 20:34
  • $\begingroup$ Also would this technique work against giants like the Entelodont $\endgroup$ – Amoeba May 21 '18 at 23:46
  • $\begingroup$ @Amoeba - Probably - I mean a spiky sledgehammer is a hell of a weapon, let alone one that can dispense super-heated steam at the press of a button. $\endgroup$ – Chromane May 24 '18 at 1:43
  • $\begingroup$ Also - I'm not sure about combining the two concepts - I think that might overcomplicate things $\endgroup$ – Chromane May 24 '18 at 1:44

You can make steam powered hammers that hit harder than humans can hit. Steam has been used to power rockets. See this video as an example. You can make a hammer that is filled with compressed steam. When swinging the hammer, hit a trigger releasing the steam and increasing the hammer's speed greatly. The hammer wielder could be wearing a tank of compressed steam on his back, with a hose going to the hammer, for greater capacity. Obviously, this puts the wielder in danger, as a puncture to the tank would be explosive. But that makes it more interesting, right?

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – James May 22 '18 at 17:45

Use the steam to power the wielder, not the hammer

This is a sort of frame-challenge answer, but using steam within a weapon seems rather limiting and hard to use. Some of the other answers may be better suited to your exact purpose if that's the case.

Rather than powering a single weapon with steam, I argue that powering a person with the steam is a better idea. They would be able to use steam to rocket about through the air, and literally drop onto enemies with incredible force behind their favorite hammer-type weapon. The best visual I have for this comes from the anime/manga Attack on Titan, where the warriors use steam power to fly through the air and, well, attack the titans.

Vertical maneuvering equipment

(Click above image for gif!)

Although this may not be exactly what you had in mind, I'd argue that very few things can stand up to a morningstar descending at the terminal velocity of a human, plus or minus the acceleration from the steam jets. Sadly, it wouldn't necessarily contain many gears so I suppose that's points off.

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    $\begingroup$ Not many gears - but do you get bonus points for steampunk googles? $\endgroup$ – Chromane May 21 '18 at 5:19
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    $\begingroup$ While I agree in principle, your example is flawed. Newton's 3rd Law of Motion. For every action, there is an equal and opposite reaction. You could fly through the air quickly and hit something morning star. You would probably kill the person you hit, not to mention ripping your arms from their sockets and shattering your bones. You would need something to absorb the energy. Dont believe me, try leaning out of a moving car at 60MPH and hit a wall with a bat. $\endgroup$ – Keltari May 21 '18 at 5:21
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    $\begingroup$ @Keltari You dare imply that anime doesn’t follow hard-science physics? :p I agree with your point but would argue that it’s a problem for any hammer-based weapon. You seem to be commenting that my technique would hit too hard, which sounds like a good problem to have for a weapon. $\endgroup$ – Dubukay May 21 '18 at 6:29
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    $\begingroup$ @Dubukay I dont trust any anime that puts so many more teeth than there should be in the mouth of titans. it looks creepy. $\endgroup$ – Keltari May 21 '18 at 15:21
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    $\begingroup$ the gif gave me the idea to have the guy propel himself through the air with the hammers $\endgroup$ – Amoeba May 21 '18 at 23:25

It's not quite a hammer, and definitely fails on 'maintain a hammer shape' but what about a steam powered jack hammer or something similar?

It could definitely break rock / concrete etc. as that's what the tool is used for in real life.

I'm fairly sure it could also do a reasonable amount of damage to a human or animal too and shouldn't be too difficult to adapt to being steam powered.

Otherwise I'm not really sure what you could do with a hammer to make it mechanical or automated.

  • $\begingroup$ It hits like a hammer. It hurts like a hammer. Its a hammer. This is the best answer. $\endgroup$ – kingledion May 22 '18 at 12:23

Your biggest problem isn't the hammer or the steam. It's how to wield it.

A hammer is an exercise in leverage. Handle end travels a short distance slowly, head travels a longer distance fastest. The problem you have, as Archimedes noted, is that you need a lever and a firm place to stand.

There's no way this is human scale, so it's got to be vehicle-mounted. There's no problems in principle with a tracked vehicle (to spread the weight) fitted with a bunch of trip hammers at one end.

My question then is - what's the military use of this? It could be handy for breaking down barricades, I guess. But against infantry it's a bit pointless, isn't it? Humans are pretty squishy, so something like this is overkill. Worse, it's only dangerous in that one direction, so (like tanks generally) it's vulnerable to infantry attacking its blind spots.

  • $\begingroup$ would not a steam powered flail - mounted on a vehicle work better - a steam version of Hobart's funnies in ww2 $\endgroup$ – Neuromancer May 21 '18 at 15:01
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    $\begingroup$ @Neuromancer The OP was pretty specific about it being a hammer, not any other weapon. Even flails aren't really going to be that useful against infantry, when you can just go round the side, or shoot it with an anti-tank weapon. TBH, if you've got live steam then that is your close-range weapon. $\endgroup$ – Graham May 21 '18 at 15:10

I know this isn't exactly a Hammer but is would be suitable for hurting humans, fauna and break things.

This is based from Kabaneri of the Iron Fortress which has a similar setting where everything is mostly powered by steam.

The main character Ikoma has a steam powered weapon:

A combination of high pressured steam injected into a cartridge of gunpowder creates a needle-like explosive reaction that can bore through both cage and heart of a Kabane with ease, although at the cost of its nearly nonexistent range; the gun has to be fired at point blank, something that few people dare attempt and cost Ikoma his humanity.

This is the gun it is linked to a tank held by the hero on his back which send the compressed air:


They also use steam powered guns but that could be too over kill maybe in your setting:


Reference Video:


This could really go well with the previous answer mentioning Attack on Titan

Piercing Gun

enter image description here

  • $\begingroup$ what is a humman? Is that a hybridization of a human and a Hummer? That sounds like a deadly, yet gas inefficient combo. $\endgroup$ – Keltari May 22 '18 at 6:34
  • $\begingroup$ @Keltari didn't see the typo thanks for pointing it out. $\endgroup$ – Mederic May 22 '18 at 7:26
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    $\begingroup$ @Keltari 0.1 miles per sandwich $\endgroup$ – Bilkokuya May 22 '18 at 16:05

There have been real-world efforts to create "power fist" type weapons which used compressed air to drive a piston forward at the end of the wielder's swing to hit substantially more powerfully.

I'm dubious how much this would improve a hammer, but anything compressed air can do, steam can do in principle.

nb: The example given is not the only such device I've seen, there have been a few.

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    $\begingroup$ the problem with devices like this as I mentioned in another answers comments, is Newton's 3rd law. For every action, there is an equal and opposite reaction. While smashing a melon doesnt require a lot of force, smashing a concrete wall does. The force that hits the wall, hits you just as hard. Unless you had a method for solidly planting yourself to the ground and absorbing the energy, punching a wall with such a device would do more damage to your soft body than the hard concrete. In addition to that, that video is bogus. His device doesnt work at all. $\endgroup$ – Keltari May 21 '18 at 23:15
  • $\begingroup$ @Keltari There are two ways to get around the 3rd law (it's more of a guideline than a law really, isn't it?): first, provide the opposite reaction as well. A "power fist"-style weapon would, just before impact, launch the business end of the weapon at the target as well as launching a chunk of metal out the back - the two effects cancel each other out, and you just have to be careful where you point it; the second is to use time to soften the impact. If you have dampeners (pistons, etc.) inside the weapon, then they can be used to distribute the force over time to the bearer. $\endgroup$ – Logan Pickup May 22 '18 at 2:33
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    $\begingroup$ @LoganPickup That is not how physics works. First, a law is most definitely not a guideline, Its a law. It is unbreakable. Secondly, your example and explanation is wrong. If you were to eject a mass out the back, you are increasing the fists forward momentum. At best, by a negligible amount, at worst, much harder. Hitting harder means there is more force for you to overcome. $\endgroup$ – Keltari May 22 '18 at 2:57
  • $\begingroup$ @Keltari Sorry, the quip about it being a guideline was a joke. My point was that you could eject something out both ends, which leave the fists themselves neutral, and use the ejected mass to cause the damage. $\endgroup$ – Logan Pickup May 22 '18 at 3:03
  • $\begingroup$ Yeah, I'm pretty dubious of the physics of this myself, I share it mostly because it's an example of a melee weapon that's supposed to turn gaseous pressure into impact damage $\endgroup$ – Ruadhan May 22 '18 at 10:23

The captive bolt pistol is a pneumatic hammer used to stun or kill livestock. Most use pressurized air but there is no reason pressurized steam could not produce the same effect. The villain in No Country For Old Men used a captive bolt pistol as his preferred weapon. http://www.imfdb.org/wiki/No_Country_for_Old_Men#Captive_Bolt_Pistol

A steam powered captive bolt gun with a large bolt could definitely be a weapon. The force exerted on the target would also be exerted back through the wielder, who must be braced.

But hammer shaped: imagine this. It is a big hammer. The head contains a captive bolt, which is triggered on impact shooting forward from the face of the hammer. The bolt hits with the combined force of the hammer and its own steam impetus, and the hammer head flies backward. The other face of the hammer also has a captive bolt and so the recoil from the first strike is used to prime the second. The hammer wielder might need to spin the hammer 360 degrees either around his head or by turning his entire body.


You don't specify that the hammer need be wielded by a human's hands. I can envision something closer to a siege weapon - a battering ram like object on a wheeled carriage. Trundle it up to your target, hold it in place, and bangbangbang.

I see two directions you could use the power - up or down.

You can use the steam to lift the hammer, allowing it to be far heavier, and let gravity deliver the blow. It'd require some supports like a construction vehicle.

similarly, it could be a lighter hammer that you propel downward. That would likely require supports that grip the ground, to keep the device from flipping backwards on the down-stroke.

Both would be driven by a piston arrangement - the second would require the steam be stored for a compressed blow, like the launch mechanism on an aircraft carrier.

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    $\begingroup$ Your first example (lifting the hammer with steam) is a real thing. That deisgne was used historically in fixed power hammers at rail yards. $\endgroup$ – Austin Hemmelgarn May 21 '18 at 23:31

While steam hammers are a real thing https://en.wikipedia.org/wiki/Steam_hammer using one as a weapon just won't work. The reason basically comes down to Newton's Law: "For every action, there is an equal and opposite reaction". If the business end of your weapon moves in a straight line, hitting the opponent will drive you backward with as much force as the blunt end of your hammer exerts. (That's why swords are thin and pointy.) Then too, if your opponent has strong armor, they will tend to just bounce backwards, just as you will. Bottom line is that the linear "hammer" is likely to do as much damage to you as to your opponent.

Things aren't much better with a swinging hammer. Swinging it much faster than a muscle-powered hammer exerts force on you, so you fall over backwards. (You can actually feel this if you pay attention while e.g. splitting wood or driving fence posts, which about as close to using a war hammer as most of us will get.) So again, your weapon damages you.

That's not even getting into the problems inherent in carrying around a fire, fuel (most of which will be burned to maintain pressure while maneuvering into position), high-pressure lines carrying scalding steam that could be severed by a projectile...

  • $\begingroup$ "hitting the opponent will drive you backward with as much force as the blunt end of your hammer exerts." Only if you're pushing them with a stationary hammer. If you were to throw a hammer, it's going in a straight line and will exert zero force on you when it hits. Using a hammer normally, you throw the head at the nail rather than pushing -momentum invested over the swing is delivered to the target in an instant, massively increasing the force. Powered hand held hammers are common for demolition work and use that fact that you can hold something with more force than you can swing it. $\endgroup$ – Pete Kirkham May 22 '18 at 15:41
  • $\begingroup$ @Pete Kirkham: If you throw a hammer, it's not being used as a hammer, but as a projectile. But you still experience the reaction force, just over a longer time as you swing. WRT powered hammers (which I've used), it's not that they apply a (much) greater force with each strike, but that they can repeat the strikes faster than a human. So if you can get your opponent to hold still while you use your steam powered jackhammer on his armor, you're good :-) $\endgroup$ – jamesqf May 23 '18 at 8:16

Many of the answers here have laid out how enhancing the speed of the hammer risks dealing too much additional damage to the wielder despite progressively flatter victims, and I'd agree this is extremely risky for general usage.

Instead I'd propose adding vents capable of expelling hot steam to the impact face of the weapon, triggered manually, hopefully maintaining the 'steam-powered warhammer' fantasy without the accidental broken bones.

This would allow your soldiers (with a little suspension of disbelief) to:

  • Attempt to dislodge the hammer if it becomes embedded in some of that concrete, mega-fauna or other victims, but not enough force to risk damaging the wielder
  • Blind, disorient, or otherwise force targets to retreat further backwards after a non-lethal hit, reducing the chance of a follow-up blow against the hammer wielder whilst preparing another swing
  • Burn heavily armoured enemies able to tank a warhammer blow. A floored enemy could easily be disabled through a burst of steam, rather than leaving yourself open through additional swings

If the back-end of the hammer was a blade or spike you'd even have the potential to rotate the hammer and propel forwards as originally suggested in the question. This would have to be a high-risk, less common attempt to pierce exceptionally strong or armoured targets, though if it penetrated successfully there'd be greater opportunity to let go of the hammer before it reaches a complete stop, and minimise risk to the wielder.


i'm not quite sure on the subject so don't hesitate to downvote if I'm talking bullshit.

My idea would be some sort of centrifugal hammer. You use your steam to make something rotate really fast in the head of the hammer. When you action the hammer, something block the gears. The "rotator" is blocked instantly and his kinetic energy is used to propulse the hammer in a direction. Like a sort of internal sling, exception the projectile is your whole hammer and the sling himself. I'll try a little drawing :

enter image description here

The advantages is that you can keep a hammer-ish look. You can make the pivotal piece visible, through some grillage or something, in the hammerhead.

Hope you'll like it. Hope it makes sense mechanically speaking, too.

  • $\begingroup$ this is a cool idea, maybe it could be part of a tethered hydraulic system powered by a steam boiler in a backpack $\endgroup$ – beppe9000 May 21 '18 at 14:58
  • $\begingroup$ it looks feasible maybe if you combine with the steam rocket to get the maximum effect. $\endgroup$ – Amoeba May 21 '18 at 23:27
  • $\begingroup$ Definitely wouldn't work mechanically, but I would get on the boat that centripetal force is the best way to do this. $\endgroup$ – theREALyumdub May 21 '18 at 23:43
  • $\begingroup$ would you explain why not ? I'm genuinely curious $\endgroup$ – GlorfSf May 22 '18 at 9:30

Jumping on @jamesqf's answer, this is physically difficult (but not impossible) and what most suggestions have said so far is somewhat incorrect realistically. This is because of Newton's Laws (Specifically the Third here)

  1. For every action, there is an equal and opposite re-action

This means in our example two things:

1) When a mass moves linearly, as in "rocket-firing" it, it also creates an equal force in the opposite direction. So look at the ground here:


That air and fuel is moving with a lot of force! Neglecting the exhaust problem of a steam rocket, a human weight (~62 kilo says google) hammer hitting forwards at fast velocities would hit a human forwards with an imparted force, but the imparted force is equally applied to the wielder backwards, including joints and bones, and in the opposite direction. So hitting forwards with some force would push you backwards with the same force. Breaking concrete? Not useful for a human wielder bluntly, unless you had some sort of intricate counter weight.

2) When a mass moves from a "tether" like a handle, it exerts an opposite rotation force. For example, Mario has some interesting ways of killing megafauna, swinging them by the tail!

So Long Dear Bowser!

He's got some strong legs! Suppose my hammer "jerks" forward from my arm by rotation. Something has to counter-balance that, and it's not going to be my wrist if the force could break bones. Maybe my muscles, but probably not from an arm all the way down...

My conclusion is that a blunt "warhammer" would not work for this with a human wielder holding the force. And about that concrete: it's a fun fact that a human femur, the largest bone in the human body, is about as strong as concrete. Not stronger: you won't do it bluntly.

Needs to be effective in hurting and killing humans, mega-fauna, and break through concrete and steel.

The more gears, the better.

But of course, I neglected two thirds of the important laws.

  1. Force is equal to the change in momentum per change in time: Force is equal to mass times acceleration

Are you familiar with flywheels? You could use a flywheel churned by a steam engine and TONS of gears to do a torque differential - then impart its momentum by having it strike something or "gear stop" suddenly. Say the flywheel is ~150-200lbs, the bullet-shaped hammer head is ~30lbs, that's a lot for the rest of the contraption - but it would be more like a siege weapon.

Something that would break concrete could be sharp, but not steel. The steel would bend under mass but jackhammers are no good, even if it was ultra-hard like Tungsten. It would need to be blunt because steel doesn't chip away to my knowledge, and steam isn't hot enough to do something heat wise to steel (It's at least 212 F, but steel melts > 1000 F, that steam would cut out of pipes and slice people but even water has a hard time cutting steel under pressure - unless they found and rigged up a water-jet).

Another idea is two hammers on a pivot that rev up and hit, maybe on some sort of tank. But that would be a lot bigger, I should think - maybe something you could put on trained mega-fauna or a tank of some sort.

Anyways, this is my mostly realistic answer. But this isn't the Physics SE.

  • $\begingroup$ OOooo Flywheels, a steampunk enthusiast's dream!!! But could the gears be exposed or would they need to be covered? $\endgroup$ – Amoeba May 22 '18 at 2:50
  • $\begingroup$ @Amoeba I have no idea, but I would assume a housing would add too much weight. Seems like the point was to have them all exposed. $\endgroup$ – theREALyumdub May 22 '18 at 12:50
  • $\begingroup$ Also, it appears that there are flywheel engines still in good use today from the 1800s, they look like the oil rigs we would typically think of (probably for good reason). And there are advanced technology flywheels that can store power and output it quickly, mostly for electrical applications (think charging a battery but no chemicals). Those are an active design field. $\endgroup$ – theREALyumdub May 22 '18 at 13:44

A lot of answers are mentioning Newton's third law as a sticking point, but it is not the hard limit that is being implied. The best way of overcoming it so a human can wield steam-powered weaponry, is with dampening.

Personally, I favour nice big pistons, but you could also use gears and springs - and the advantage of springs (or flywheels, but flywheels on their own are probably not going to be able to be large enough) is that they also, for at least a short time, store some of the energy they absorb and so can be used to make the next hit even harder, saving you some steam - or they can be used to "reload" the weapon.

If you're still generating too much force for the human skeleton to withstand, then a metal arm brace that connects to a body and leg brace (with joint locks to prevent them going past the human range of motion) can absorb some force too - possibly knocking the wielder over, but it's better than a broken arm.

Another option is to have the steam weapon push both ways. This takes care of the third law too, but requires twice as much power to deliver the same amount of force in a strike.

The key here, given that the human's own weight and ability to lift is a limiting factor, is that instead of leverage you just go for speed, and let that do all the damage, so your steam weapon is all about getting the head of the hammer to as high a speed as possible. Your brace, backfire, and dampeners absorb what they can to prevent your arm falling off. It doesn't seem practical to have a steam device that can cause the hammer to rotate faster (it would be too limiting to the normal range of motion in your arm), so the next best thing is to use Willk's idea and make the head of the hammer a giant captive bolt pistol.

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    $\begingroup$ A useful rebuttal to my answer to keep in mind, although having a counterweight would not require more energy to my knowledge, and I'd have to think a little more about the physics here (like if falling backwards would indicate force not applied). I think a large captive bolt pistol would push the user back a lot, like firing a shot gun, but it might be effective in melee. Only no way you could break steel, and it would be a lot less like a warhammer $\endgroup$ – theREALyumdub May 22 '18 at 13:09
  • $\begingroup$ And I feel the skeleton is a cool idea, but the question was warhammer, not power suit, and the exoskeleton would likely be too weak or too heavy as asked. $\endgroup$ – theREALyumdub May 22 '18 at 14:06

Have you considered a steam-powered exoskeleton for the human. The exoskeleton could have a larger steam reserve than an unaided human could carry, plus it could absorb the forces that hitting something with the hammer would produce. Oh yes, lots of gears and flywheels.

The hammer would basically be a large hammer with a long handle (for leverage). The handle would have a thin hollow area for steam to go through, and one end of the hammer would have a steam rocket to accelerate this hammer faster than humanly possible.

The human would be protected by the exoskeleton from the forces that would otherwise break his arms. By putting some light armor in there, he would also be protected from concrete chips and pieces of brains that would be thrown back by attacking a concrete wall or a human respectively.

And if swallowed by megafauna, the boiler could be made to explode, at least giving it indigestion.


protected by James May 22 '18 at 17:44

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