ImmortalVagrant |
So I was DMing a campaign, and the a character fell into a pit with his mount, which was a kangaroo. The character tried to lasso a knob and pull himself (And his kangaroo) out of the pit. He failed, but then another character tried to run over and assist by pulling them up himself.
My question is, how much weight can a rope hold before it breaks? I can't find anything in the rulebook, except for break DC, which is 23, but I don't know how weight would correlate to a break DC.
hewhocaves |
Thats a rough question to answer as the strength of rope depends on the material its made from, the thickness of the rope, the way in which it is made, the braiding and the wear and tear it has already undergone.
Some values for nylon rope, for example, can be found here: http://www.engineeringtoolbox.com/nylon-rope-strength-d_1513.html
I know its not much help, but i guess you could assume that the PCs would buy rope that would be strong enough to hold the whole party at once. Or at least multiple members of the party.
Also keep in mind the kangaroo is not going to keep still. That bouncing will put excess strain on the rope. The excess force will translate as the kangaroo seeming to way much more than he actually does.
Frankthedm |
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I can't find anything in the rulebook, except for break DC, which is 23, but I don't know how weight would correlate to a break DC.
With a feat of strength one can can burst a rope. The same amount of strength should burst the rope whether the situation is good or bad for the character.
Look what STR it takes to break a rope taking 20. DC 23 is a STR of 16. So to me it is reasonable that the load a STR 15 could bear is safe for the rope, while the load a STR 16 could bear might break the rope. Looking at what that STR can lift and stagger around with tells me the danger zone is 400 to 460LB {Double the normal max load for a STR 16]
So a load 400-460 LB has a 5% chance of breaking the DC 23 rope.
Some may say this is too low, so to achieve a happy medium, have the load on the rope take 10 at most times.
However on the round the rope is exposed to a major jarring, roll the STR check. All other times the "taking 10" result is used. Thus a hemp rope has a safe use of 400 LB and if no funny business is going on it can handle 6400 LB.
460 Lbs. has as an effective breaking STR of 16 +3
520 Lbs. has as an effective breaking STR of 17 +3
600 Lbs. has as an effective breaking STR of 18 +4
700 Lbs. has as an effective breaking STR of 19 +4
800 Lbs. has as an effective breaking STR of 20 +5
920 Lbs. has as an effective breaking STR of 21 +5
1040 Lbs. has as an effective breaking STR of 22 +6
1200 Lbs. has as an effective breaking STR of 23 +6
1400 Lbs. has as an effective breaking STR of 24 +7
1600 Lbs. has as an effective breaking STR of 25 +7
1840 Lbs. has as an effective breaking STR of 26 +8
2080 Lbs. has as an effective breaking STR of 27 +8
2400 Lbs. has as an effective breaking STR of 28 +9
2800 Lbs. has as an effective breaking STR of 29 +9
3200 Lbs. has as an effective breaking STR of 30 +10
3680 Lbs. has as an effective breaking STR of 31 +10
4160 Lbs. has as an effective breaking STR of 32 +11
4800 Lbs. has as an effective breaking STR of 33 +11
5600 Lbs. has as an effective breaking STR of 34 +12
6400 Lbs. has as an effective breaking STR of 35 +12
7360 Lbs. has as an effective breaking STR of 36 +13
8320 Lbs. has as an effective breaking STR of 37 +13
9600 Lbs. has as an effective breaking STR of 38 +14
11200 Lbs. has as an effective breaking STR of 39 +14
12800 Lbs. has as an effective breaking STR of 40 +15
14720 Lbs. has as an effective breaking STR of 41 +15
16640 Lbs. has as an effective breaking STR of 42 +16
19200 Lbs. has as an effective breaking STR of 43 +16
22400 Lbs. has as an effective breaking STR of 44 +17
25600 Lbs. has as an effective breaking STR of 45 +17
29440 Lbs. has as an effective breaking STR of 46 +18
33280 Lbs. has as an effective breaking STR of 47 +18
38400 Lbs. has as an effective breaking STR of 48 +19
44800 Lbs. has as an effective breaking STR of 49 +19
In the odd occurrence that a 30000lb load is suddenly forced onto the rope and it holds, remember that is just for a single round, next round when the load starts "taking 10", the ropes is a goner. Assume fate smiled on that moment allowing for the party to have a few seconds to use magic to save the load or to get out of the way.
Kaisoku |
Well, 1 inch hemp rope can have something like 8-10,000 lbs of tensile strength.
A break DC of 23 needs a Strength score of 36 to break on a take 10 (Str +13 modifier). Dragging load of Strength 36 is 18,400 lbs.
I'd go with that.. if it weighs more than 18,400 lbs, it'll break when attempting to drag something.
Silk rope would be over 20,000 lbs.
A kangaroo would likely only be a Medium sized creature, and the largest type of kangaroo weighs around 200lbs. If you have some special one for a mount, it might be "large-sized", in which case it would have 8x the weight, at around 1600 lbs (a horse is 1000-1500 lbs, so I'd go with that).
So a person, with equipment and armor, and a large-sized mount, would likely still be under the tensile strength of the rope involved (going by the break DC info). Even if you don't go with the drag values (such as going by lift instead, etc), it'd still be well within limits.
A quick check on google found an article that had a similar equation, but forgot to factor the 5x drag values. So I'd say it's probably "enough to not matter in most situations".
Edit
@Frankthedm: Lift values are for lifting over your head, which doesn't equate to the action of lifting for purposes of pulling someone along with the rope.
The concern is the ultimate strength (or tensile strength) of the rope before it breaks. The ultimate load of 36 strength (taking 10 on a DC 23), the drag value at 5x the max load.
What the people can actually pull will be dependent on lift weights, because they are lifting the creature into the air.
Now, if they don't have a pulley, then I'd make it so that the rubbing along the edge might reduce this amount a bit, but we are still looking at a ridiculously large number. DM hand-waving time.
Bob_Loblaw |
You can also see some modern day values for hemp rope at this site.
I had written a response very close to Frank's but my computer futzed and it didn't survive. I think Frank has it right.
Happler |
The tensile strength of spidersilk rope would be ridiculously strong, yeah. I'd say there's no reason to worry about the details on this one.
And since it only lists spider silk ropes as :"Spider's silk rope has 6 hit points and can be burst with a DC 25 Strength check."
which is only 2 points higher then a hemp rope, that is either a weak spider silk rope, or really strong hemp.
Another fun fact, is the DC to break rope is 23 (as we know), the DC to bend iron bars is 24.
Yonman |
The problem with everyone's numbers is a rope of climbing says it can carry up to 3,000 lbs.
This value is significantly lower than some of your projected values above. I therefore have used a hemp DC 23 STR check to equal the max load it can carry, i.e. 600 lbs.
Then, just made it simple, I said if you shorten the length of a 50' long rope to 25' by doubling up on the rope you can carry 2*600 = 1200 lbs of weight.
Diego Rossi |
It is an 11-year-old thread.
That said, the easiest solution is to check the internet for the breaking point of hemp rope.
Surprisingly it requires a bit of research (I was really surprised seeing that the hemp ropes sold on Amazon don't list their breaking point), but it is still on the first page of a Google search:
- hemp rope with a diameter of 0.78" weights 1 lb for 7.5' of length and has a breaking load of 4092 lbs;
- hemp rope with a diameter of 1.17" weights 1 lb for 3' of length and has a breaking load of 5840 lbs.
In-game hemp rope weighs 10 lbs for 50', so 1 lb for 5' of rope. It is midway between the two. To make it simple, we can say it has a breaking load of 5,000 lbs.
That is the value of new or well-kept rope, for the often abused adventure's rope we can play safe and say it is about 2,000 lbs. Beyond that, there is a risk of it breaking.
Senko |
It is an 11-year-old thread.
That said, the easiest solution is to check the internet for the breaking point of hemp rope.
Surprisingly it requires a bit of research (I was really surprised seeing that the hemp ropes sold on Amazon don't list their breaking point), but it is still on the first page of a Google search:
- hemp rope with a diameter of 0.78" weights 1 lb for 7.5' of length and has a breaking load of 4092 lbs;
- hemp rope with a diameter of 1.17" weights 1 lb for 3' of length and has a breaking load of 5840 lbs.In-game hemp rope weighs 10 lbs for 50', so 1 lb for 5' of rope. It is midway between the two. To make it simple, we can say it has a breaking load of 5,000 lbs.
That is the value of new or well-kept rope, for the often abused adventure's rope we can play safe and say it is about 2,000 lbs. Beyond that, there is a risk of it breaking.
I'm now inclined to search the breaking point of spider silk.
Azothath |
commentary
there is information out there on various 'strength of materials' engineering sites. You could also try the CRC Handbooks. But that's Real Life info and The Game is a very rough and inaccurate model.
Secondly the tests are for rather static and ideal conditions in a testing rig. The working strength is generally 70-50% of the maximum load. Things like twisting, bouncing, dynamic loads are generally not covered (steel and some building materials have more data as engineers and computer modelling uses that info).
Lastly hemp is a natural product so it is not uniform or consistent and is subject to environmental conditions (like being wet and losing strength as the fibers expand and can move more easily adding stress to the weakpoints, fungal/mold growth eating the lignin & cellulose, insect damage). There is also time; duration of load, wear & tear. So naturally the numbers will vary from the tested value (thus the 'working strength' is generally considered a safe maximum).
Yonman |
Diego Rossi wrote:I'm now inclined to search the breaking point of spider silk.It is an 11-year-old thread.
That said, the easiest solution is to check the internet for the breaking point of hemp rope.
Surprisingly it requires a bit of research (I was really surprised seeing that the hemp ropes sold on Amazon don't list their breaking point), but it is still on the first page of a Google search:
- hemp rope with a diameter of 0.78" weights 1 lb for 7.5' of length and has a breaking load of 4092 lbs;
- hemp rope with a diameter of 1.17" weights 1 lb for 3' of length and has a breaking load of 5840 lbs.In-game hemp rope weighs 10 lbs for 50', so 1 lb for 5' of rope. It is midway between the two. To make it simple, we can say it has a breaking load of 5,000 lbs.
That is the value of new or well-kept rope, for the often abused adventure's rope we can play safe and say it is about 2,000 lbs. Beyond that, there is a risk of it breaking.
Why would you make regular hemp rope a higher weight capacity than a Rope of Climbing which is a magic item?
Diego Rossi |
Why would you make regular hemp rope a higher weight capacity than a Rope of Climbing which is a magic item?
Rope of Climbing
Source Ultimate Equipment pg. 317, PRPG Core Rulebook pg. 529
Aura faint transmutation; CL 3rd
Slot none; Price 3,000 gp; Weight 3 lbs.
Description
A 60-foot-long rope of climbing is no thicker than a wand, but it is strong enough to support 3,000 pounds.
Real-life data say that a hemp rope 1" tick has a breaking point of about 5,000 lbs. As Andy Brown pointed out that is ideal conditions. If you read my post you will see that I said: "for the often abused adventure's rope we can play safe and say it is about 2,000 lbs".
The magical rope weighs less than 1/3 of the 1" hemp rope and probably has a diameter of less than 1/2". It still has a higher weight capacity than a used 1" hemp rope.
I don't see any problem with my numbers.
BTW, unless a magic item says that it is particularly sturdy or resistant, it isn't. A magical cloak has exactly the same hit points as a non-magical cloak. If they are worn they generally use the character save (unless the magical cloak has a high CL), so the only real difference is that the non-magical cloak doesn't get a save against effects while the magical one gets it if the effect gives a save. Trow both into a fire, they both burn.