Livestock space requirements, stampedes, nuisance

[Curmudgeon]

Somewhat off topic, the PCs plan may turn out less brilliantly than first thought. "Medieval Siege Warfare" IIRC was the name of the book that made an interesting point about drawbridges. Drawbridges were built with counterpoised weights to lower the drawbridge. Cutting the chains attached to a drawbridge would leave it up and unable to be lowered, it would not drop the drawbridge as is so often portrayed in the movies. Another side effect of this design was the drawbridge lowered more slowly than it raised. Admittedly, your setting appears to be in the ancient period but counter-poised weights are known to have been in use at least during the period of the Roman Empire. It's just possible that they were is use early enough that your PCs are going to need another fly spell to make a quick escape with.

[Icelander]

Originally Posted by Curmudgeon

Somewhat off topic, the PCs plan may turn out less brilliantly than first thought. "Medieval Siege Warfare" IIRC was the name of the book that made an interesting point about drawbridges. Drawbridges were built with counterpoised weights to lower the drawbridge. Cutting the chains attached to a drawbridge would leave it up and unable to be lowered, it would not drop the drawbridge as is so often portrayed in the movies. Another side effect of this design was the drawbridge lowered more slowly than it raised. Admittedly, your setting appears to be in the ancient period but counter-poised weights are known to have been in use at least during the period of the Roman Empire. It's just possible that they were is use early enough that your PCs are going to need another fly spell to make a quick escape with.

Hmmm, the fort is built very quickly, using epic magic to move the earth arounds to make the earthworks and moat.

I had imagined that the drawbridge and gate were the same massive wooden structure, reinforced with shields on the outer surface. When it was raised, it was held by the chains and four massive bolts. To raise or lower it, sixteen men turn two windlasses, one to each side.

I hadn't actually thought about counterweights, because it seems that this would require much more work to implement than the crude gate I imagined. On the other hand, if you can describe some way this could work that could be built in a few days by reasonably clever soldiers assisted by priests*, I'm all ears.

In any case 'cutting the chains' is shorthand for 'lowering the drawbridge by removing whatever is holding it up and letting gravity do the work'. The PCs have Engineer (Combat) and used magic (Night Vision, Keen Vision, Hawk Vision) to examine the mechanism while the enemy was raising and lowering it for some minutes before their attack. If the drawbridge can be lowered at all, I expect they know how to do it.

*Some of the officers would have Engineer (Combat)/TL2 or TL3 (depending on how old fashioned they are), but no one with Engineer (Civil) is likely to have bothered to come to a forward supply dump close to the fearsome enemy.

[Curmudgeon]

It's been a long time since I read that book but from what I can recall it shouldn't require great engineering skill to get up something that would do the job. The drawing of the counterpoise didn't have a scale but as a rough estimate it was a wooden box about three times the width of the upright beam (to which the chain was attached), maybe twice the upright's width and about waist high. The box was filled with rocks to make up the weight. The book didn't give particulars but I'd guess the individual rocks were in the 10-20 lb. range. The book didn't mention how the rocks were kept in the box when the drawbridge was lowered and the box would be lying on its side. My guess would be a wooden top hinged at the edge closest to the upright and a hasp and hinge on the opposite side (the hasp being on the top when the box is lying on its side). A stick through the hasp should be enough to keep it in place. The windlasses would be used to lower the drawbridge and, if you don't have a pawl action available, will have to held in place to keep the drawbridge lowered. The windlasses would only be used to raise the drawbridge if you need to raise it under control. Otherwise let go of the windlasses and gravity will bring the uprights down and the drawbridge up, probably with a resounding crash (if you're going to do that the box should be made of stout boards and be either a Z- or X-braced on each face).
The two uprights with boxes, are about twice as long as the drawbridge is high and pivot so that the top of the upright is directly above the top of the drawbridge when lowered and the bottom of the upright is the length of the drawbridge inside the walls. The whole point of the system was that all the effort was in lowering the drawbridge, gravity wouldn't lower the drawbridge at all unless you removed the boxes and burning the boxes would still leave a pile of rocks blocking the movement of the uprights that would have to be cleared before the drawbridge could be lowered.
To make sure the drawbridge can't fall down, set the bottom of the drawbridge a few inches closer to the moat than the top (6" should be plenty), so that the whole drawbridge is leaning back, either with its sides against the sides of the wall or the top resting against an upright between the walls or both. In that case, you'll need men on poles to push the drawbridge upright prior to lowering the drawbridge but the extra security would probably make it worthwhile.

[Icelander]

Originally Posted by Curmudgeon

It's been a long time since I read that book but from what I can recall it shouldn't require great engineering skill to get up something that would do the job. The drawing of the counterpoise didn't have a scale but as a rough estimate it was a wooden box about three times the width of the upright beam (to which the chain was attached), maybe twice the upright's width and about waist high. The box was filled with rocks to make up the weight. The book didn't give particulars but I'd guess the individual rocks were in the 10-20 lb. range. The book didn't mention how the rocks were kept in the box when the drawbridge was lowered and the box would be lying on its side. My guess would be a wooden top hinged at the edge closest to the upright and a hasp and hinge on the opposite side (the hasp being on the top when the box is lying on its side). A stick through the hasp should be enough to keep it in place. The windlasses would be used to lower the drawbridge and, if you don't have a pawl action available, will have to held in place to keep the drawbridge lowered. The windlasses would only be used to raise the drawbridge if you need to raise it under control. Otherwise let go of the windlasses and gravity will bring the uprights down and the drawbridge up, probably with a resounding crash (if you're going to do that the box should be made of stout boards and be either a Z- or X-braced on each face).

Ok, to help me understand, on which side of the drawbridge is the box? Is it inside the fort or outside it?

Also, is this drawbridge anchored at the friendly side of the moat and is lowered toward the enemy?

How compatible would this model be with a design where the drawbridge and the gate are one and the same; that is, when the drawbridge is up, it serves to block the 20' wide gap in the earthworks wall that is the main entrance to the fort?

Originally Posted by Curmudgeon

The two uprights with boxes, are about twice as long as the drawbridge is high and pivot so that the top of the upright is directly above the top of the drawbridge when lowered and the bottom of the upright is the length of the drawbridge inside the walls. The whole point of the system was that all the effort was in lowering the drawbridge, gravity wouldn't lower the drawbridge at all unless you removed the boxes and burning the boxes would still leave a pile of rocks blocking the movement of the uprights that would have to be cleared before the drawbridge could be lowered.

Explain these uprights to me better. Where are they located when the drawbridge is up?

Originally Posted by Curmudgeon

To make sure the drawbridge can't fall down, set the bottom of the drawbridge a few inches closer to the moat than the top (6" should be plenty), so that the whole drawbridge is leaning back, either with its sides against the sides of the wall or the top resting against an upright between the walls or both. In that case, you'll need men on poles to push the drawbridge upright prior to lowering the drawbridge but the extra security would probably make it worthwhile.

It seems that this would make the drawbridge much less formiddable in its alternative role as the main gates. If pushing it hard enough from the outside makes it fall into the fort, well, that's no good.

I had imagined that it was some 3' taller than the hole in the earthworks that it covered. That would mean that leaning back shouldn't be a problem.

I'm still not sure how to work counterweights into the design. Where would I put them where they did not block the tunnel through the earthworks? It's a 30' tall and 30' wide rampart and the main gate is basically just a shored-up tunnel through it with a drawbridge at the end. When the drawbridge is up, the tunnel is blocked.

[Curmudgeon]

The uprights are actually large levers made of squared beams of wood. Using your 33' x 30' drawbridge, the uprights would be 66' plus the thickness of the walls long assuming that they rest against the surface of the wall when in the closed position. The top of the wall would be the fulcrum point. The chains on the drawbridge would attach to the uppermost point on the uprights. The only purpose of the drawbridge chains are to act as attachment points to the levers. The drawbridge doesn't actually move under its own power, it's slaved to the motion of the levers, lowering when the levers lower and rising when the levers raise. the levers would be about 8" x 8" if made of greenwood or 12" x 12" if made of seasoned wood.
With a stone wall the levers were housed through the wall so that the upper half was outside the wall and the lower half inside. That obviously isn't going to work as well with an earthen wall. Probably the best suggestion is to put each lever on a wood cradle. Each cradle would consist of of two wooden beams lying on the ground acting as the base with an upright housed at the midpoint of the base and braced with two other beams set so that each brace forms a right angled triangle with the base and upright and the two triangles together forming an isoceles triangle. The levers will need to be bored at their midpoint and a round shaft placed through the hole with the shaft mounting between the two uprights of the cradle. The lever will need to be lengthened to make up the distance between the wall and the cradle upright. The cradle uprights should be placed far enough apart that the box can pass between them.
The box with its rocks is the counterweight. The weight of the drawbridge, drawbridge chains and upper half of the lever is less than the weight of the box, rocks and lower half of the lever.
Each windlass will need two chains or ropes attached to its lever. One is attached to the upper half of the lever to pull the lever down to lower the drawbridge. The other is attached to the lower half of the lever to restrain it when raising the drawbridge.
Tilting the drawbridge inward 6" will have a 33' drawbridge sitting at an 89 degree angle rather than 90 degrees. Since the drawbridge should have its outer side edges and the top 3' resting against the wall, the drawbridge shouldn't fall inward unless the walls behind it crumble. If the wall breaks, the difference in time between it falling because it's tilted as opposed to perfectly vertical would need to be measured in seconds because it's unlikely to take a full minute.
Putting the drawbridge to double use as a gate is a good improvisation but fortifications typically had a gate that was separate from the drawbridge. To maximize what you do have, I'd suggest a couple of tweaks if you haven't already committed yourself to your players. First I'd narrow the drawbridge and tunnel to about 15'. Drawbridges were typically longer than they were wide. Since your forces are outnumbered, you want to channel any attack so that your enemy can't make fullest use of his numbers if he does breach your gate. A 15' wide tunnel would limit the enemy to 10 men shoulder to shoulder entering at a time, fewer if they need elbow room to use their weapons.
You may also want to 'spring' the drawbridge as medieval gates were sprung. The planks are cut with a slight bevel along the length of each edge so that the whole gate bows slightly outward. A sprung gate redirected part of the force from a battering ram out towards the sides of the gates where it was absorbed by the wall. The force that was wasn't redirected had the effect of trying to force the gate shut.
If the opportunity is available raising the wall height to 45' would give them severe problems scaling the walls since scaling ladders had a practical limit of 40' before they became either too heavy to carry or too weak to support their own weight.

[Polydamas]

I'm a bit surprised by the existence of a mechanical drawbridge at all, if the fort was built so quickly, but more surprised that there is a thin hardened-earth roof to the gate tunnel. That's not a very good structural material, and the roof makes it harder to defend the gate tunnel against enemies who have broken through the gate. I would have been more inclined to span the entrance with a lintel and a wooden bridge level with the top of the wall, and continued the crenelations along the sides of the gate tunnel, allowing defenders to hurl down on attackers in the gate tunnel. But then again, I don't know what threats this fort was designed to face.

[Icelander]

Originally Posted by Polydamas

I'm a bit surprised by the existence of a mechanical drawbridge at all, if the fort was built so quickly, but more surprised that there is a thin hardened-earth roof to the gate tunnel. That's not a very good structural material, and the roof makes it harder to defend the gate tunnel against enemies who have broken through the gate. I would have been more inclined to span the entrance with a lintel and a wooden bridge level with the top of the wall, and continued the crenelations along the sides of the gate tunnel, allowing defenders to hurl down on attackers in the gate tunnel. But then again, I don't know what threats this fort was designed to face.

This design feature is dictated by the method of constuction, not by tactical utility. Yes, a wooden bridge and lintel would have been superior. On the other hand, the defenders could use Move Earth to move around what mud and earth was already present on the hilltop, but all good quality building wood would have to be fetched over 50 miles of road by ox-cart and if we were talking proper trees, probably shipping in from a 100 miles off before that. And the fort was built during a period when ox-carts had extreme trouble moving on the roads due to mud.

The existing firestep uses magically shaped earth as much as possible and poor-quality wood only when necessary. That's wood from local bushes and shrubberies, mind you, nothing that could actually stand up to enemy attacks from the outside.

The carefully shaped earthern roof is not at all secure and it is probably not a good place to be standing if people start using trebuchets. On the other hand, a well-placed Move Earth or six might serve to collapse it, which might be a useful last-ditch defence for the defenders. And probably not fun for the PCs.

[Gorkamorka]

I'd love to know how it eventually goes. Feel like letting us know?

[Icelander]

Originally Posted by Gorkamorka

I'd love to know how it eventually goes. Feel like letting us know?

I'll do my best to remember.

I left last session as Sir Michael Carragher*, Abadas 'the Mad'* and their ally, the Northern Wizard Ubarum Bronzehand, had landed inside the tunnel where the winches for the drawbridge are. They flew over the outside walls, taking heavy fire from slings, bows, ballistae, scorpions and war priests with their spells and javelins that transform into bolts of lightning.

Ankhapet Si'Hamet, the Quester for the Unconquered Sun and learned gentleman, horseman and archer from the deserts of Murhom, and his ally, the redoubtable Nuraun Teltree, Ship's Wizard of the Storm Horn and member in good standing of the Inner Circle of the Wizards Guild of Ravens Bluff, had experienced some trouble with their flight spells. More precisely, Teltree was shot down with a bolt of lighting and Ankhapet swooped down to rescue him before he crashed into the spiked moat. Having done that, Ankhapet proceeded to lose his balance and spun out of control. While he was spinning over the defenders on the wall, an enterprising battle priest decided to add to his confusion by subjecting him to a minor stunning spell.

The three who have reached their objective have set the entrance to the tunnel aflame with copious amounts of everburning oil (they are immune to fire for the duration) and slain the guards immediately at the gates. Ubarun Bronzehand had a minor fright when he critically failed a parry and lost his staff, suffering a fair wound in the process, but Sir Michael heroically threw himself between him and his attackers and slew them all in short order.

Now Abadas, whose fascination with fire and destruction combined with his short military career has actually led to him studying military engineering, will use his flame-powers to get the drawbridge down. In the meantime, the other four are meant to hold off the whole garrison.

I suppose that as things are, Sir Michael and the Bronzehand will have to do the work of four for a while. Fortunately, Sir Michael, having drunk potions of giant strength and heroism, has ST 31 and weapon skills around 30. Wearing his dragonscale armour and an array of protective magical items, there are few warriors who could lay him low. And the Bronzehand is a famed combat mage, a savant of spells invoking pure magical force.

*Young, earnest lad from a hilly land far to the West, physique and temperament of a star rugby player and a claymore that will cut stone.
**He prefers 'I just get these headaches'. An orphan whose parentage is clearly something exotic. Feels a strong kinship with fire and can cheerfully stand inside an inferno and be unharmed, even absorbing the heat of the flame to power his innate magical abilities. Has begun to formally learn magic, but is still weak in all areas except those having to do with fire.

[SonofJohn]

Surpluss Animals and epic magic would call for some blood magic, if you simply would get only one point out of every sheep killed you would still have some pretty nasty ****storm headingtowards the PCs.

Some Priest with the right spells on nearly the same power level as the PCs could simply deep impact there army with this kind of raw magic energy.