In S07E01 - Dragonstone, the gates of Dragonstone open inwards.
Why? Isn't it easier to ram down when it can be pushed open? The hinges are high enough to be inaccessible, and could easily be reinforced/hardened during wartime.
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26Oh good question! Outward-opening gates would probably be harder to break down.– ObsidiaJul 17, 2017 at 20:17
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42I've had to down-vote because of a lack of research. How would a bartering ram work if you had outward opening gates (here's a clue, it wouldn't) also look at your door, if it was outward opening the hinges would be on the outside. Pop that off, and you might as well start singing Timber by Pitbull– EdlothiadJul 17, 2017 at 20:45
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9I've voted to close this question as off-topic because in essence it has no tie to science fiction or fantasy beyond the show it appears in. We could ask countless question about "Why is XYZ this way in GoT?" that all answers boil down to "that what was done in the real world".– SkoobaJul 18, 2017 at 17:33
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13@Skooba You're saying this question is off-topic because a part of a fictional universe was inspired by real-world things? I don't think it works that way.– GallifreyanJul 18, 2017 at 18:07
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23@Gallifreyan IT would be like asking "Why do they wear armor in GoT?", "Why do ships have sails in GoT?", by adding "in GoT" does not automatically make a question on-topic.– SkoobaJul 18, 2017 at 18:08
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4 Answers
This is an interesting physics problem. Counter intuitively, it looks like opening inward is actually stronger!
From a strength perspective, it doesn't matter whether the doors open inward or outward. What matters is whether an attacker's actions cause tension or compression. If you have the typical doors you see in castles, a battering ram hit causes tension - the wooden beams pull against each other to resist the ram. If you bow the doors out a bit, you can see that they cause compression instead. Trying to ram the doors causes the doors to try to close more, compressing all of the timbers.
Different materials handle tension and compression in different ways. Concrete, for instance, is very good at compression loads but falls apart under tension loads. Accordingly, you'll always see concrete structures in compression. Look at a bridge, and you'll always see an arch to it, ensuring the whole bridge is in compression.
Wood, on the other hand, is much better at tension loads. Compression loading focuses all of the forces on one part of the door, while tension loading lets wood do what it is best at. If you rammed a door in compression, the wood would rapidly splinter, rather than bending to soak up the energy and momentum. (There's more to it, dealing with cross grain and along-the-grain forces, but that's another physics lesson)
So you definitely want a door structured so that battering rams cause tension. If you run the geometry, you see that it's really hard to have a door open outwards and exhibit tension under attack.
answered Jul 18, 2017 at 17:01
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12Does this really matter, given the door isn't bowed but rather plane when closed? There's always tension when it bends inwards at being hit from outside. Regardless whether it's held in place by hinges and locks, or pressed against the frame.– BergiJul 18, 2017 at 17:48
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7@Bergi If the door is a flat pane, then that would work as well, but then you'd have to be really careful with your construction to make sure the hinges are ready to be bent backwards under the force of a strike. The construction of a door that is under tension when attacked and opens inward is a much easier construction problem than one that opens outward. Jul 18, 2017 at 18:15
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8So actually "run the geometry", along with some diagrams. At the moment, this answer as it stands is far inferior to those below it, regardless of the checkmark. You wouldn't "need to make sure hinges [were] ready to be bent backwards": external hinges would simply be destroyed. Similarly, closed concrete doors would chip just the same way wood splinters, without any regard to which way they normally opened.– llyJul 20, 2017 at 1:34
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19tl;dr: At the moment, this answer sounds smarter than it actually is. It's already less on topic than those below it but could still be mostly salvaged, assuming you actually do understand the physics involved, by demonstrating that knowledge in some test cases and comparisons. Start with the fact that none of the doors are bowed and that battering it bows them all in, not out.– llyJul 20, 2017 at 1:36
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3Wood is better than concrete at tension, but tension isn't what wood "does best", it is still considerably stronger in compression than tension. Jul 20, 2017 at 13:31
This is how the castle doors/gates work in real life for various reasons.
- To open outwards, the hinges would need to be on the outside. Not an ideal design.
- It is easier to push gates closed against an enemy than to pull them closed.
- Doors that open inwards are always under the control of the castle and protected by the stonework.
- You can barricade the door from the inside with rubble to prevent access.
- In case of attack, the people closing the door are protected.
- Gates are usually barred, rather than locked, which needs to be inside the door and is easier if the gate opens towards the bar.
Here are some real castle gates for reference
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1Comments are not for extended discussion; this conversation has been moved to chat.– Null ♦Jul 18, 2017 at 18:14
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25Additionally: it's a lot harder to block an inwardly-opening door from the outside. It would be quite the prank to hammer a spike in front of a door and lock the inhabitants inside. Well, the inhabitants might not find it funny...– ArmanXJul 20, 2017 at 18:16
For small doors which are thick relative to their size such as the hatch on an army tank it makes sense to open outwards. Castle doors are very large and relatively thin for their size. Since a battering ram places it's force in the middle of the door it will snap the timbers of both inward and outward opening doors equally well. Most of the strength of these doors comes from the portcullis behind it and/or cross braces and other support timbers put in place during a siege not from which way they swing.
So you might as well have them open inward to protect the edges of the door (which are considered the weakest part) and for the other reasons that amflare mentioned.
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A tank hatch doesn't have the same design goals - firstly, opening inwards means the occupant has to have space to move out of the way, and space inside the hull is limited, secondly it is resisting blast force not attempts to open the hinges. Jul 21, 2017 at 8:57
Others have made good points, but I think the simplest explanation is probably this: large gates like that are usually barred, not (just) locked. You want to be able to bar and unbar the door from the inside, and for that to work, it has to open inward.
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2Technically you can bar a gate from the side it opens away from. You'll just be pulling against the bar rather than pushing against it.– amflareJul 19, 2017 at 20:53
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6Hmm, I suppose you could... it would require having hooks on the side of the door itself that faces the bar, though, strong enough to keep it closed. An awkward engineering problem with a lot of points of failure compared with just pressing relatively-evenly against the whole length of the bar (presumably secured at the ends.) Jul 19, 2017 at 20:56
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1@amflare. Usually you would not take just one bar to reinforce the gate. That's the primary reason for a portcullis, to reinforce the gate against attacks. And it is technically very difficult to use a portcullis in any sensible way if the gate opens to the outside. It is however a lot easier to reinforce the gate with a portcullis when it opens to the inside. Jul 20, 2017 at 7:39