[LT] Portcullises

[Anthony]

Originally Posted by johndallman

Of course, you don't want to make your portcullis too easy to open; the enemy are not supposed to be able to lift it. That argues for some way of blocking it, and against a counterweight system.

It's not hard to lock a counterweight so it can't be used to help open the door.

[Kromm]

I suspect that the erratum is in the portcullis weight. To be positive about this, though, we'd have to ask the authors. I am not a portcullis weight expert.

[DanHoward]

I used the figures in DF2 because I couldn't get any stats on real portcullises. The weight might be wrong but I have no problem with the amount of ST required to lift it. The lifter has to overcome both the portcullis itself AND the locking mechanism holding it down.

[Kromm]

Aha! The ones in DF 2 are yard-wide gates, not proper castle defenses. Even so, most of those listed there are heavier . . . I think it would be a safe bet to pick a larger weight.

[lexington]

Originally Posted by Kromm

Aha! The ones in DF 2 are yard-wide gates, not proper castle defenses. Even so, most of those listed there are heavier . . . I think it would be a safe bet to pick a larger weight.

It might be worth noting that if you just triple the weight you get almost exactly the answer that a poster on RPGnet calculated for a 10'x10' portcullis:
http://forum.rpg.net/archive/index.php/t-28862.html

[Ze'Manel Cunha]

Originally Posted by lexington

It might be worth noting that if you just triple the weight you get almost exactly the answer that a poster on RPGnet calculated for a 10'x10' portcullis:
http://forum.rpg.net/archive/index.php/t-28862.html

I posted a whole series of different calculations above for different thickness and sizes of metal bars at 1 foot intervals, form 0.5" thick to 2" thick.

I didn't do numbers for oak clad in iron because the section was on metal grilles, though the most common portcullises that I've seen were built that way.

[Figleaf23]

Of course the grate weight of a portcullis is only part of the question -- we still need a properly calculated lifting mechanism.

[Anthony]

Originally Posted by Figleaf23

Of course the grate weight of a portcullis is only part of the question -- we still need a properly calculated lifting mechanism.

That's going to depend on weight. Absent a counterweight, and with no pulley or crank mechanism, the maximum a single lifter can manage is BL*10, but will lift faster than 1' per 3s (BL*10 at 1'/3s is BL*4.5W, or 90W for an average adult, which is a rate an average adult can probably maintain for multiple hours); with a reasonable crank mechanism, the 450 lb portcullis (which is not a side door; 15' x 20' is a large door) can probably be managed at the listed speed with a single person.

[Dunadin777]

Originally Posted by Anthony

That's going to depend on weight. Absent a counterweight, and with no pulley or crank mechanism, the maximum a single lifter can manage is BL*10, but will lift faster than 1' per 3s (BL*10 at 1'/3s is BL*4.5W, or 90W for an average adult, which is a rate an average adult can probably maintain for multiple hours); with a reasonable crank mechanism, the 450 lb portcullis (which is not a side door; 15' x 20' is a large door) can probably be managed at the listed speed with a single person.

Everyone keeps invoking the Extra-heavy encumbrance weight limit, which is wrong. The rules specifically state that X-Hvy encumbrance is more than a person can normally lift--loading one object into a pack at a time, you could carry 10xBL, but there's no way you could realistically lift that much in the first place. The max someone can lift at once is 8xBL (B353) and that takes four seconds and two hands. And even that I'd require a strength roll to do successfully, as it otherwise assumes that an average strength 10 person can bench 160 lbs until the cows come home.

The whole concept of the mechanism, to me, seems like it should be based on one-handed lift limits, though, since I don't imagine a portcullis team of 8 straining and using both hands unless we're looking at an absurdly fantasized mechanism and gate. Plus we want to be fair to one-armed adventurers, right? Or allow them to hold a shield or weapon while operating the mechanism? The one-handed lift limit is 2xBL and takes two seconds. So each average operator contribues 40 lbs to the team's lift, with 8 guys lifting 320 lbs worth of stuff. Now the mechanism itself helps with the rest, which isn't great, but as said before features a safety/locking mechanism or some such. Also there might be track friction to consider as well. Just to make the raise rate fit this explanation's units, though, I'd say it lifts at 1'/two seconds.

[Dunadin777]

And I wouldn't worry about making a portcullis too difficult to lift manually. It was not a passive barrier--that's a proper gate, which would be used in general situations. Instead it was used specifically to slow enemies down in an assault and make it easy for defenders to use pikes to kill any attackers that tried to lift the portcullis. It doesn't matter much if four guys can manually lift it by standing shoulder-to-shoulder and using both hands over the course of about 4 or more seconds--they'll get AoA'd by some nice long spears well before that.