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[usage stuff]

Short version: Crossbows IRL are way easier to make and their users several orders of magnitude easier to train and replace, requirements that are very important in the defensive operations of a fort  but not so much for attackers, immortal people like elves and goblins, and adventurers.

All of that is perfectly relevant and would also be perfect reasons to have them over bows. Especially when one takes into account ranged fighters often having the self-preservation instincts of a sleep-deprived cabbage and seem to have been like that for years and years now.

Ah but quality does not matter as much as rate of fire and when the economy is developed we would be able to reliably buy better quality bows.  That is the point, we have to come up with a reason to have crossbows that isn't rate of fire, of which they are inferior to bows pretty much whatever their quality.

Unless it's changed or mods are applied, the main reason is simple logistics. It just happens that quality of weapons and ammo is currently also one of the few things we have some amount of control over that affects performance.

There's simply no guarantee we can keep a bow squad supplied, especially since merchants often bring large amounts of ammo that because of useless and very expensive decorations on top of the price hike from requesting them specifically, is outside the budget of young (and even some more established) forts without abuse of certain goods or an abundance of high value materials and good craftsmen. If anything, even with rate of fire ignored, a bow squad would (and to a degree currently is,) consequently extremely expensive to have around and a display of wealth for a fortress. They have the stuff to buy all those hideously expensive arrows.

And because of an inability to make/reliably supply training ammo, those very same expensive arrows are going to be expended in training as well as combat, because to keep that squad supplied, you can't turn your nose up at anything that gets brought for sale.

Granted, the above assumes buying bows and arrows, but even then as mentioned previously, supplying from the enemy is a hit-or-miss proposition and almost always turn up stuff worse than what your weaponsmiths and bowyers can make in terms fo crossbows and bolts. This also all assumes dwarves will be kept as not able to produce those weapons themselves, and no mods to allow them to do so are applied.

[Bumber]

IRL, bows require a certain height to be able to use effectively. Dwarves wouldn't be able to use the more powerful English long bow, etc.

[Splint]

IRL, bows require a certain height to be able to use effectively. Dwarves wouldn't be able to use the more powerful English long bow, etc.

That's less of an issue here. Vanilla bows are small and light enough that even kobolds and smaller animal people can wield them comfortably (although they probably look damn-near like longbows on them )

Now obviously, modded in bows might be made too big for a dwarf - and consequently anything their size or smaller - to use. Vanilla ones though seem much closer to a modestly sized hunting or... I guess Skirmish bow? is that term? Rather than one of those big, powerful (and consequently probably much slower to shoot) war bows.

[Atarlost]

IRL, bows require a certain height to be able to use effectively. Dwarves wouldn't be able to use the more powerful English long bow, etc.

That's less of an issue here. Vanilla bows are small and light enough that even kobolds and smaller animal people can wield them comfortably (although they probably look damn-near like longbows on them )

Now obviously, modded in bows might be made too big for a dwarf - and consequently anything their size or smaller - to use. Vanilla ones though seem much closer to a modestly sized hunting or... I guess Skirmish bow? is that term? Rather than one of those big, powerful (and consequently probably much slower to shoot) war bows.

It's not the size of the bow, it's the draw length.  An English warbow with ~100 lbs draw weight is comparable to a crossbow with ~300 lbs draw weight because the bow has a much longer draw length. 

A smaller creature can wield a short recurve bow with potential draw length equal to a longbow, but can not draw it farther than the length of their arm.  This reduces the poundage because spring pressure scales with the square of flex and reduces the distance and thus time that the force is applied over.  Less time and less force means less work which in this context means less kinetic energy. 

This is why I said bow damage should scale with strength and size.  The stronger the archer the higher the draw weight can be and the larger the archer the longer the draw length can be.  We must either implement obscene micromanagement for different draw lengths of bow or abstract that away and assume every archer uses a bow with the correct draw weight and adequate draw length.  To assume bows are so small and weak anyone can draw them to the same distance means that they must also be useless for anything but shooting small game.  Kobolds being able to use bows in a meaningful way is a design oversight. 

Crossbows have a fixed energy capacity, but reload time depends on how much mechanical advantage is needed to draw them back.  If we again abstract out the question of goats foot lever or cranequin or whatever to be whatever is appropriate to the strength of the wielder the stronger a wielder the faster he or she can reload. 

For humans the advantage of a crossbow is that you don't need to ban all non-archery entertainments on Sundays for a generation before you can use them in warfare or give pride and miitary importance to peasants that would be disastrously destabilizing if you didn't have a large population of land owning yeomen rather than being fully feudal with all peasants as serfs.  For dwarves and goblins, though, the advantage of crossbows is that you don't need long human arms to get good effect out of them.  For trolls if they used weapons bows would be a no brainer.  Even if their accuracy was worse (and this is overblown by people who don't realize most crossbowmen were professional mercenaries) they'd get so much more efficiency out of the longer draw length their size allows it would be more than worth the trade off.  Sgt. Detritus only had problems because nobody thought of commissioning a troll sized bow and the draw length limit of the materials at human height was much lower than his arm length. 

[GoblinCookie]

Unless it's changed or mods are applied, the main reason is simple logistics. It just happens that quality of weapons and ammo is currently also one of the few things we have some amount of control over that affects performance.

There's simply no guarantee we can keep a bow squad supplied, especially since merchants often bring large amounts of ammo that because of useless and very expensive decorations on top of the price hike from requesting them specifically, is outside the budget of young (and even some more established) forts without abuse of certain goods or an abundance of high value materials and good craftsmen. If anything, even with rate of fire ignored, a bow squad would (and to a degree currently is,) consequently extremely expensive to have around and a display of wealth for a fortress. They have the stuff to buy all those hideously expensive arrows.

And because of an inability to make/reliably supply training ammo, those very same expensive arrows are going to be expended in training as well as combat, because to keep that squad supplied, you can't turn your nose up at anything that gets brought for sale.

Granted, the above assumes buying bows and arrows, but even then as mentioned previously, supplying from the enemy is a hit-or-miss proposition and almost always turn up stuff worse than what your weaponsmiths and bowyers can make in terms fo crossbows and bolts. This also all assumes dwarves will be kept as not able to produce those weapons themselves, and no mods to allow them to do so are applied.

The economy means that we will likely be able to acquire a large quantity of arrows since the more we buy the more they will make. Buy cheap wooden arrows from the elves to use for training and buy expensive metal arrows from the humans to use in actual combat.   

IRL, bows require a certain height to be able to use effectively. Dwarves wouldn't be able to use the more powerful English long bow, etc.

That's less of an issue here. Vanilla bows are small and light enough that even kobolds and smaller animal people can wield them comfortably (although they probably look damn-near like longbows on them )

Now obviously, modded in bows might be made too big for a dwarf - and consequently anything their size or smaller - to use. Vanilla ones though seem much closer to a modestly sized hunting or... I guess Skirmish bow? is that term? Rather than one of those big, powerful (and consequently probably much slower to shoot) war bows.

It's not the size of the bow, it's the draw length.  An English warbow with ~100 lbs draw weight is comparable to a crossbow with ~300 lbs draw weight because the bow has a much longer draw length. 

A smaller creature can wield a short recurve bow with potential draw length equal to a longbow, but can not draw it farther than the length of their arm.  This reduces the poundage because spring pressure scales with the square of flex and reduces the distance and thus time that the force is applied over.  Less time and less force means less work which in this context means less kinetic energy. 

This is why I said bow damage should scale with strength and size.  The stronger the archer the higher the draw weight can be and the larger the archer the longer the draw length can be.  We must either implement obscene micromanagement for different draw lengths of bow or abstract that away and assume every archer uses a bow with the correct draw weight and adequate draw length.  To assume bows are so small and weak anyone can draw them to the same distance means that they must also be useless for anything but shooting small game.  Kobolds being able to use bows in a meaningful way is a design oversight. 

Crossbows have a fixed energy capacity, but reload time depends on how much mechanical advantage is needed to draw them back.  If we again abstract out the question of goats foot lever or cranequin or whatever to be whatever is appropriate to the strength of the wielder the stronger a wielder the faster he or she can reload. 

For humans the advantage of a crossbow is that you don't need to ban all non-archery entertainments on Sundays for a generation before you can use them in warfare or give pride and miitary importance to peasants that would be disastrously destabilizing if you didn't have a large population of land owning yeomen rather than being fully feudal with all peasants as serfs.  For dwarves and goblins, though, the advantage of crossbows is that you don't need long human arms to get good effect out of them.  For trolls if they used weapons bows would be a no brainer.  Even if their accuracy was worse (and this is overblown by people who don't realize most crossbowmen were professional mercenaries) they'd get so much more efficiency out of the longer draw length their size allows it would be more than worth the trade off.  Sgt. Detritus only had problems because nobody thought of commissioning a troll sized bow and the draw length limit of the materials at human height was much lower than his arm length. 

It is not the length of your arm, it is the force that is used to draw the bow back.  If you use tougher materials then you can easily make a smaller bow that can fire with more power than a stronger one.  The problem with bows is that the materials are not always available to make a bow that can fire with a greater force without the whole thing breaking. 

That means giant bows for giants are not so realistic.  You might have the strength to pull back a bow of that force, but the materials still have to be found that will not just shatter when that much force is applied to them.  Of course in Dwarf Fortress we presently have laughable concepts like iron bows.   

[Splint]

Unless it's changed or mods are applied, the main reason is simple logistics. It just happens that quality of weapons and ammo is currently also one of the few things we have some amount of control over that affects performance.

There's simply no guarantee we can keep a bow squad supplied, especially since merchants often bring large amounts of ammo that because of useless and very expensive decorations on top of the price hike from requesting them specifically, is outside the budget of young (and even some more established) forts without abuse of certain goods or an abundance of high value materials and good craftsmen. If anything, even with rate of fire ignored, a bow squad would (and to a degree currently is,) consequently extremely expensive to have around and a display of wealth for a fortress. They have the stuff to buy all those hideously expensive arrows.

And because of an inability to make/reliably supply training ammo, those very same expensive arrows are going to be expended in training as well as combat, because to keep that squad supplied, you can't turn your nose up at anything that gets brought for sale.

Granted, the above assumes buying bows and arrows, but even then as mentioned previously, supplying from the enemy is a hit-or-miss proposition and almost always turn up stuff worse than what your weaponsmiths and bowyers can make in terms fo crossbows and bolts. This also all assumes dwarves will be kept as not able to produce those weapons themselves, and no mods to allow them to do so are applied.

The economy means that we will likely be able to acquire a large quantity of arrows since the more we buy the more they will make. Buy cheap wooden arrows from the elves to use for training and buy expensive metal arrows from the humans to use in actual combat.   

Read that again. I expressly mentioned merchants as being one of the very things that prevents a steady supply of ammo. A small squad, say 3-5 guys, probably isn't going to be pissing away all their ammo in two seasons. But a full squad very well might, and more than that you'll have more rusty rookie bowmen than experts.

With an increased rate of fire, the ammo gets used up more quickly, often at a rate that can't necessarily be matched by imports depending on the number of bowmen one intends to field.

That means yes, our fort's demand is up, but that doesn't mean they're going to sell affordable ammo. They'll certainly bring more, but because our hypothetical fort's demand is high, they're going to charge high and oftentimes, tack on expensive bling that serves no purpose but to make the arrows in question even more expensive than they already are from the demand for them.

While this isn't necessarily an issue with elves, who simply can't bring hyper expensive arrows because of the nature of what they make theirs from, it is an issue with human caravans, who aside from enemies are our sole supplier of arrows that can actually hurt anything. A supplier who can be disrupted by invaders, werecreatures, or various mega/semi-megabeasts, and that's not including the eventual revamp caravans are likely to receive making them part of the world as well, which further reduces the reliability of importing enough arrows to supply and train more than a handful of archers.

And regardless, this suggestion would still be preferable to what we have now, which not only severely limits the usefulness of ranged weapons both in fort and adventure mode, but also hinders what can be done with modding.

It was only relatively recently, using a 3rd party tool that will be broken next release and likely take significant time to be brought up to speed, that we gained the ability to mod in things like cannons, automatic rifles, terrain deforming explosives, and more fantastical stuff like lightning guns.

All of that is far more comprehensive and "unbalancing" than crossbows not shooting as fast as bows (and suffers from issues of maintaining steady supplies of ammo. Just like bows for civs that can't make them.)

[peasant cretin]

Compressing some of the ideas mentioned in this thread but filtered through the current combat system's mechanics:

I think the easy/intuitive way to model Reload is off the melee combat system's PREPARE:RECOVER. Lowest tick count for melee attack is 2:2 PREPARE:RECOVER, with highest at 5:5.

Spoiler: Tick costs of various offensive actions (click to show/hide)

In unmodded Vanilla, weapons and natural attacks (punches, bites, gores, etc.) are ATTACK_PREPARE_AND_RECOVER:3:3 which is to say 6 ticks long in terms of time. Two exceptions to this, kicks and whip attacks, are ATTACK_PREPARE_AND_RECOVER:4:4.

Aimed (strike) attacks will add or subtract from the PREPARE_AND_RECOVER.

The types of aimed weapon/natural attacks are:
Quick Attack  subtracts 1 tick from both the PREPARE_AND_RECOVER
Standard Attack  does not add or subtract anything from PREPARE_AND_RECOVER
Heavy Attack  will add 1 tick to both the PREPARE_AND_RECOVER
Precise Attack  will add *2* ticks to the PREPARE and 0 ticks to RECOVER
Wild Attack  subtracts 1 tick from the PREPARE, but adds *2* ticks to RECOVER
(The above information can be confirmed by "see-it-yourselfers" by testing this in arena mode, or by readers here in Dwarf Fortress Talk 21.)

So, I'd say the fastest bow PREPARE:RECOVER should be at 2:2, with the fastest xbow PREPARE:RECOVER at 6:2. How you model the slowest PREPARE:RECOVER could be to just triple *only* the PREPARE at 6:2 and 18:2. It seems intuitive to both the relatively simple machine that is the bow and the complex machine that is the xbow, that the skill/attribute issue re:time involve only the PREPARE. Enemy melee or incoming enemy range would interrupt and cancel any PREPARE of whatever speed, of course.

Tick counts could be based not just on bow/xbow skill as it is now...

Spoiler: current guess (click to show/hide)

Tick count reload for Grandmaster bow/xbow (lvl 14) I'd estimate at around say 32-80, and Dabbling (lvl 0) being twice that.

That's my rough guess based on the number of combat messages you get (about 8 if you arena-test with lvl14 bow/xbow;16 if you have lvl0 bow/xbow).

For the arena-test you need Grandmaster Dodger&Shielder, full armor, combat prefs set to Stand Ground/Stand Ground, as you fire from an adjacent tile at a smaller, fully armored target.

Lowest tick count for melee attack would be 2:2 with highest at 5:5 for those roll-to-hit failure messages (NPC misses you). You'd add 1 extra tick for any shield block. Since you're at Stand Ground/Stand Ground, you don't add in any Dodger Jump away message which would be 3 additional ticks.

Something along those lines.

...but the interplay between the Weapon Skill *and* the Agility Stat. Break Agility into tiers: High, Above Average, Average, and everything Below Average. Divide Weapon Skill into similar tiers levels 0-2 (Dabbling/Novice/Adequate), 3-5 (Competent/Skilled/Proficient), 6-8 (Talented/Adept/Expert), 9-11 (Professional/Accomplished/Great+). Pretty much you'd get the real world interplay of technique with physical attribute, and how each modifies the other.

Now to make up for the disparity of PREPARE ticks between the bow and the xbow, you'd add in the distance factor. Xbows will always fire (basing this off NPC viewrange) the full 20 tiles, where as bow distance would be determined by weapon skill + strength stat. High strength and whatever skill bracket gives the full 20 tiles, with Above Average at 15 tiles, Average at 10, and Below Average at 5.

NPC generation in either Fort or Adv would only spawn bow users with Avg or more strength as a result. Really can't have a poor gobbo bow shooting at the 5 tile mark.

All this being said, in order to make this moddable, we'd need a relevant tokens.

[Atarlost]

It is not the length of your arm, it is the force that is used to draw the bow back.  If you use tougher materials then you can easily make a smaller bow that can fire with more power than a stronger one.  The problem with bows is that the materials are not always available to make a bow that can fire with a greater force without the whole thing breaking. 

This is just basic physics.  Kinetic Energy is Energy.  Energy is Work.  Work is the integral of force over distance.  For constant force that's force MULTIPLIED BY DISTANCE. 

The limits to how strong a bow for a giant can be don't matter because you run into problems scaling meat based biology long before you run into trouble scaling wood or steel.  If we're ignoring the square cube law for meat we have to ignore it for wood and metal so they can have any implements of any sort. 

[GoblinCookie]

ULTIPLIED BY DISTANCE. 
The limits to how strong a bow for a giant can be don't matter because you run into problems scaling meat based biology long before you run into trouble scaling wood or steel.  If we're ignoring the square cube law for meat we have to ignore it for wood and metal so they can have any implements of any sort.

We are assuming that the meat scaling problems were already dealt with by the giants own physiology during it's evolution.  Just because giants can exist (up to a certain size), does not mean giant-sized bows can exist, the problem is harder. 

Regular longbows are difficult to make and require special materials like yew wood because the sheer force that is placed upon the bow during firing does not allow bows to be easily scaled up.  The basic nature of a bow maximizes the problems you are describing while creatures are designed to minimize the problems of scaling.   In effect the body part which is most similar to bows is actually the joints and that is the real problem with making giant creatures for the same reason. 

[thompson]

How big is the giant? I'd imagine a wrought iron bow with a sinew string should be fine. The Romans essentially did that for their ballistae.

[Atarlost]

We are assuming that the meat scaling problems were already dealt with by the giants own physiology during it's evolution.  Just because giants can exist (up to a certain size), does not mean giant-sized bows can exist, the problem is harder. 

Trees are larger than giants, or at least larger than trolls, which are the largest creatures to exist in civilizations where they might be provided with bows.  Wood is a far less structurally complicated material and the method of fluid transport used in trees scales far better than the method used in animals and people.  You might eventually run into a limit for draw weight based on material strength, but you do not run into a limit for draw length because you can just make a longer bow that provides proportionately longer draw length for the same amount of flex.  There are bow wood other than yew.  Bamboo for instance grows to around two stories in height and was used historically in India.  Making a bow from two separate limbs held in a rigid frame at the center as modern fiberglass bows often are can double the straight length you can get from a given wood type. 

[thompson]

Right, I've given this some thought and have come up with a scheme of tags for projectile weapons.

[ENERGY_STORAGE]- the means by which energy is stored while drawing the weapon. Allowed values are TENSILE, COMPRESSIVE, SHEAR, CHEMICAL, PNEUMATIC, KINETIC.
[GEARING_RATIO] - value is 1 for bows, higher for crossbows. A high gearing ratio allows a higher ultimate force, but slows reloading.
[DRAW_LENGTH] - the maximum length you can draw the weapon. This is a size normalized value, so doubling the bow size doubles the draw length. Draw length can represent barrel length for blowguns and firearms (useful for modders).

Now, suppose you are about to fire a bow. The game checks the ENERGY_STORAGE tag and learns it needs to use the SHEAR algorithm. The energy of the projectile will then be:

Y*A*D^2/2=E

This is found by integrating over Hooke's law (F=kx), noting that the force constant will be Y*A.

Y is the shear modulus. A is the cross-sectional area. D is the draw length. It will either be the highest draw length a user can support, or the longest length the material can support. By Hooke's law we know how the force changes with draw length. The maximum force for an archer would be:

F_MAX= T*S*k*G

T is the user's strength, S size, and k some constant of proportionality. G is the gearing ratio.

The maximum force the material can support would be:

F_MAX = Y_MAX * A

Y_MAX is the maximum shear modulus, and A the cross sectional area of the bow. This can be estimated from the size, or held constant. There could be an additional optional tag for this.

The draw length used in the kinetic energy equation would be:

D=F_MAX/(Y*A).

And that's about it. This will scale for weapons of any size, and will also lead to optimal sizes for certain materials (where the draw length approaches the ultimate shear strength in most cases.

We are assuming elastic materials here. But weapons will be ruined anyway once plastic deformation sets in, so it's not a bad assumption.

Edit: Oh, right, variable reload times. Well, that should be proportional to D*G / T / S / SKILL, where SKILL is the relevant skill. Strong, large, skilled creatures fire faster, long draw lengths with high gearing ratios are slow. There should be an optional tag for CHEMICAL and PNEUMATIC weapons which could have a constant reload time that governs reload time.

[GoblinCookie]

How big is the giant? I'd imagine a wrought iron bow with a sinew string should be fine. The Romans essentially did that for their ballistae.

Ballistae are not big crossbows. 

Wrought iron?  That is about the worst material you could conceivably use to make a bow.  To make a good bow you not only need a material that requires a suitably large amount of force to draw back but also a material that is elastic enough that it will not just break when you do so.  If you try making a bow of pretty much any size out of iron, the bow will simply snap because that material is inelastic. 

We are assuming that the meat scaling problems were already dealt with by the giants own physiology during it's evolution.  Just because giants can exist (up to a certain size), does not mean giant-sized bows can exist, the problem is harder. 

Trees are larger than giants, or at least larger than trolls, which are the largest creatures to exist in civilizations where they might be provided with bows.  Wood is a far less structurally complicated material and the method of fluid transport used in trees scales far better than the method used in animals and people.  You might eventually run into a limit for draw weight based on material strength, but you do not run into a limit for draw length because you can just make a longer bow that provides proportionately longer draw length for the same amount of flex.  There are bow wood other than yew.  Bamboo for instance grows to around two stories in height and was used historically in India.  Making a bow from two separate limbs held in a rigid frame at the center as modern fiberglass bows often are can double the straight length you can get from a given wood type. 

Yes, the reason wood is useful to make bows is because they face the giant size problem; a giant creature needs to be made of a material that is strong but also flexible, exactly what you need for bows. 

You can make a bow out of a wide variety of woods and other organic materials.  You are not however able to make a bow of *any* size, due to the structural elasticity problems that I talk about above.  The material has to be elastic enough that it does not concentrate all the force of the draw on a single point in the middle of the bow causing the thing to go *crack*.  But you also need a material that is strong enough to pick up a lot of force.  It also has to work after repeated draws, not breaking after one draw is not enough. 

For most of history people did not have access to materials *both* strong and elastic enough to make large bows out of.  This is why warfare ends up being dominated by heavily armoured spearmen and swordsmen, even when you might logically assume that holding back and shooting is a better tactic.  The bows then were too small to reliably penetrate armour, this problem was only solved in medieval times by changing the mechanics (crossbows) or by using better materials (yew longbows). 

At this point people started to deploy archers/crossbowmen in lines to face the enemy head-on when previously archers had only been deployed as skirmishers supplementary to the main battle. 

[thompson]

You might be confusing cast iron (which is not elastic) with wrought iron (which is). If you really want to be pedantic you could say both are elastic to a limit (which is actually in the raws for df materials). Beyond this limit you either have plastic deformation (wrought iron) or brittle fracture (cast iron). The reason people didn't make bows from wrought iron is that elastic potential energy scales with elongation (draw length) squared, while the restoring force scales with elongation. So, a greater draw length in a material with a relatively weak restoring force such as yew wins out over a very strong material like wrought iron that no one could pull back more than a few inches.

The equations I showed above deal with the scalability issue of elastic properties by enforcing a maximum allowable shear stress. It would also allow fantasy materials that have excellent properties for bows, and allow different types of wood to perform differently in-game using values already defined in the raws.

As a final note, you can confirm that many iron-based materials are indeed elastic by compressing a spring. When you release it it will return to its original shape. On the other hand, if you compress it too far for too long plastic deformation will set in and it will not return exactly as it was but may remain permanently shorter. The idea with bows is similar except you're inducing shear stress instead of compressive stress.

[Ninjabread]

I have to say it's quite unusual for me to back GC up, but I'm part of an iron age reenactment group, specifically covering the 1st century Roman invasion of Britain, and we do have access to a ballista, albeit a small one. I'm not so sure about later cultures, but afaik ancient Roman ballistae were made largely of wood, iron was only really used as structural reinforcement, not as a material for the limbs. I have seen crossbows with metallic limbs, not entirely sure exactly what period they were from, but it was definitely post western Rome. You were right about the sinew string though, it was more like rope than string but still.

The ideas on the evolution of warfare on the other hand are definitely off the mark, yew and crossbows seem to have been confused with gunpowder and firearms. We have checked, you need more than a yew longbow or an early medieval crossbow to get through lorica segmentata. We did manage to get a pilum through it but I can't guarantee that'd work on a fresh new set, our test lorica was old and rusty. Still enough to repel arrows and bolts though.

Also, even disregarding eastern Asia because eurocentrism, the crossbow is older than people think.