# How could the elevator at The Wall be powered?

In the show Game of Thrones there is this thing called The Wall. It is a monstrous, 300 mile (≈ 483 km) long bulwark consisting of a fortified ice wall that is 700 feet (≈ 213 meters) high (check the wiki for more details). There are also castles/forts along the foot of this wall, as garrisons for the soldiers manning it.

Now, quite conveniently, at some of the castles there exists a sort of elevator built to reach the battlements from the castle 700 feet below the top of the wall. We can see the elevator is built from wood and metal and seems to be a fairly simple construction. No actual mechanism is shown. At the bottom is a lever, that when turned either sends the elevator cabin up or down respectively.

Given world like the one presented in Game of Thrones—What could be used to power the elevator?

Assumption:

• No magic
• The tech level is that of an (at most) late-medieval'ish civilisation
• Should work in the cold weather required to preserve an ice wall

Requirements:

• Works with as little work from people and or animals as needed.
• Can be operated by some sort of lever or switch (either at the top or bottom)
• Maintenance needs should be as low as feasible

Note: I'm aware there might be a canon answer in the books (though I don't remember anything too specific). That is not what I'm asking for, and this would be the wrong Stackexchange to do so anyway. I'm wondering for general reality-based solutions for this problem outside of the actual Game of Thrones context.

• I remember seeing people cranking the elevator into action in one episode. – Renan Feb 6 at 15:30
• science based cannot be the only tag in a question. – L.Dutch Feb 6 at 15:34
• @Renan We do see people walking in a big wheel, like the ones they used to use to reload trebuchets. But I don't recall if the elevator is ever brought up in the books. – Ryan_L Feb 6 at 15:40
• @L.Dutch Can you suggest more tags? You might even want to add them directly, or is that not-done on this SE site? – Mast Feb 6 at 17:01
• @ths - It's not an Otis elevator; it's a crane. A 2" manila rope using a 12x safety factor can hold one ton, weighing about a pound per foot. So, at 500' long, you can lift 1500 pounds and still have a 12x safety factor. All the while it has a minimum breaking strength of 27900 lb/f. – Mazura Feb 7 at 0:44

With counterweights it could be possible to have a "self-powered" elevator in these conditions.

The elevator must be counter-weighted by default with a mass that will make it slowly go down if activated (to activate it, it should be sufficient to manually remove some lock).

This will allow the elevator to go down empty.

if we instead want it to go up empty, we should attach a small additional counterweight, to reach a mass higher than the one of the cabin.

if we want to go down, with people or materials, we still need to attach more counterweight, to reach a balance and avoid a too fast descent.

If we want to go up, with people or materials, we need to attach a heavier counterweight, to surpass the cabin (and content) weight.

The problem is. these counterweights (except for the default one, which is always attached) will remain on the ground level once used and we should return them up to use them. Which will require human or animal work and defeats the purpose.

To solve this issue we could simply use blocks of ice/snow, that presumably self-generate at the top of the wall. In fact, imagine that the pathways on the top must be kept clean, and some excess of snow will be found every day.

So, let's say that there is a set amount of mass that can be lifted each day (varying day by day based on weather conditions?), but this could be an efficient solution.

Edit:

The lever could actionate a mechanism that attach the cabin to a heavy or light counterweight, inverting the direction of the elevator. However, manual work will still be needed after the travel to tare and reapply the weights

• It's an ice funicular. – DJClayworth Feb 6 at 20:37
• It might be worth noting that there's a bit more complexity to this - for sufficient differences in height, you must also take into account the weight of the rope suspending the elevator (and how that changes the mass of your elevator-side and your counterweight-side as the thing moves). This is something theatre curtain systems need to account for, even at 100 feet tall. – Delioth Feb 6 at 21:00
• Regarding needing to bring counterweights back to the top, I figured that sometimes the lift would need to be winched up manually, but could run automatically with adequate preparation. It would allow the soldiers to set the lift in their downtime, and run it manpower-free during battles. – Nuclear Wang Feb 6 at 21:11
• @Delioth - The rope can be counterbalanced simply by making it a continuous loop that doesn't quite touch the ground. – chasly from UK Feb 7 at 8:31
• I presume the soldiers need to periodically clear snow from pathways, chip ice from railings, etc. to keep the top of the wall passable and safe. Collecting the snow and ice in buckets and dumping it into a storage tank at the top of the list would ensure a steady supply of conterweight ice/water, as well as a steady supply of menial labour to give to whichever members of the Watch recently irritated their superior officers. Fantasy world or no, tiring and monotonous work as minor punishment is a fine and ancient tradition in many militaries. – anaximander Feb 7 at 10:47

Good old pulleys

A major improvement from the 4th century BC and still in use today, is the compound pulley: a combination of single pulleys in a block. The mechanical advantage equals the amount of pulleys used.

A crane with a triple pulley (a "Trispastos") has two pulleys attached to the crane and a free pulley suspended from them. It offers a mechanical advantage of 3 to 1. A crane with five pulleys in a similar arrangement (dubbed a "Pentaspostos") offers a mechanical advantage of 5 to 1.

Using a compound pulley a man can lift more than he is otherwise able to. If a single man pulling a rope can exert a force of 50 kg, he can raise (or lower) 150 kg using a Trispastos and 250 kg using a Pentaspostos. The same goes for the rope. A rope with a tensile strength of 50 kilograms can be used to lift (or lower) 150 kilograms if 3 pulleys are used, and 250 kilograms if 5 pulleys are used.

And you can pull the rope using winches and capstans

• Aren't the guys in that picture actually pushing the rope? – tobias_k Feb 6 at 17:36
• not the way they are hunched. they look like they are pushing. – ths Feb 6 at 19:28
• @tobias_k A few too many drinks, I guess – Azor Ahai Feb 6 at 19:33
• @NuclearWang They may not reduce the overall energy needed, but they certainly reduce the instantaneous effort required to a level that it becomes possible for a human to act as the energy source. – Joe Bloggs Feb 6 at 22:00
• They're not pushing the rope. There's another rope at the top of the stack which the artist didn't bother to render in detail, they are pulling that. The visible rope is the slack line going off, fair chance it's a loop actually and would have a tensioner to keep the slack out. – Harper Feb 6 at 23:13

Coming down is easy, you just need a braking system, so I won't worry too much about that. Going up is the hard bit.

1. Donkey power

Nice and simple, the horse powered pump or winch is a bit of technology as old as time. In this case you're going to use your donkey/ass/mule/horse to winch a weight up to the top of the wall. When you want to ascend the pulley with the weight is linked to the pulley with the lift. Weight comes down, lift goes up. The equine is then returned to duty winching the weight back up.

2. Water power

A similar system to the horse winch but this time the counter weight is a water tank refilled at the top and emptied when at the bottom. You pour enough water into the tank that the lift starts to rise, you can also use this as part of your braking system by removing only just enough water that the lift starts to fall. Appropriate speed controllers should remain in place.

3. Men in a hamster wheel

This is a very old system for controlling such systems, used in the appropriate period for cranes when building castles. This could also be the equines from method 1 controlling the winch directly.

The lever

Rings a bell to tell whoever is in control to do their job. Control systems aren't worth the hassle in the age of manual labour.

• How about a spring system? – Mast Feb 6 at 17:02
• water power might be tricky (though not impossible) with: "Should work in the cold weather required to preserve an ice wall." – YoungJohn Feb 6 at 17:04
• @Mast, springs aren't particularly good for this sort of thing – Separatrix Feb 6 at 17:06
• #3 is technically called a treadmill. For what it's worth, operating a treadmill was often part of prison life, where appropriate. – WhatRoughBeast Feb 6 at 17:51
• Bells are still used in lifts in modern times for communication, especially in mining. A system of rings similar to morse code is used to issue simple commands. This system can sometimes malfunction and leave people stuck at the bottom of a mine: sudbury.com/local-news/… – Paul Belanger Feb 6 at 19:36

The goto device for heavy lifting in the medieval era is the treadwheel crane. Larger ones can lift some extremely heavy loads even with only one or two operators. If the elevator has an alternating counter weight a single person or animal could move an elevator easily. The largest cranes could lift multiple tons with ease.

Wind power. The ice wall is going to guarantee fairly steady winds, so a windmill or mills at the top will provide plenty of power. For low wind periods, the windmill lifts rocks during windy times. If the wind isn't blowing, a sufficient number of rocks are placed in the "down" cage to act as a counterweight.

It's not going to be a complete answer (at least not yet), but I'll try to explain the idea. I still have to work more strictly on details.

First let me be very specific about one thing. I'm handwaving here the difficulty of building so tall mechanism and probably few other things. This is just an idea how things could be organised.

First of all, as others already mentioned, we need a setup with a counterweight and to make the trip possible the counterweight needs to actually adapt it's weight to the weight of a cargo (be it human, weapons, building materials - doesn't really matter).

As I imagine it, counterweight is liquid. Since the temperature is below water freezing point, the liquid used has to be either some kind of solution or other liquid (e.g. alcohol) in order not to freeze.

At both top and bottom station there would be a mechanism that enables balancing the counterweight. As soon as the counterweight sets itself in the correct position (close to the stop), the fluid starts to flow in/out until it gets exactly even with the weight of the cargo, making the elevator stop. Once stopped the platform and counterweight are locked in their positions (i.e. can move slightly but only within specific very limited range). Whenever the weight of the two becomes unbalanced the shifted position of counterweight causes the flow of liquid in the right direction causing it to automatically balance the counterweight against the platform with cargo. When a lever is activated, it unlocks the movement of elevator and at the same time closes the counterweight liquid tank. Due to a small difference in mass (potentially with some speed limiter) the elevator starts to move in the right direction.

Depending on the design there are two options:

1. The lever activation adds or removes a bit of liquid to the counterweight making the movement possible, or
2. The counterweight filling systems are scaled so that it becomes slightly heavier at the top and slightly lighter at the bottom.

And that's pretty much it.

The system might require from time to time balancing the amount of liquid in top and bottom tanks but it might be scaled so that this maintenance isn't needed too often.