Hot on the heels of my thread discussing tinderboxes and their ilk, we come to the problem of containers in Low Tech. Namely, their odd scaling in terms of how much weight they can hold. In a previous thread Anthony suggested that the amount of weight a container can hold should realistically scale as weight divided by the cube root of volume.
Anthony's typically got a pretty good handle on physics, so let's go with that. Does anybody have datapoints we could use to determine what the constant is for each of the container types in LT? One of the possibilities mentioned in that thread was that a 3 lb cloth backpack holding 40 lb (dynamic load) probably wasn't too far off. That gives us a dynamic load constant of around 20 for cloth. What sorts of constants would be appropriate for other materials? We might be able to use ropes as a guideline, assuming cloth is comparable to hemp/manilla. A 1" diameter, 10 yard rope of that weighs 9 lb and holds 2,000 lb, so we'll set that as our 20. A 9 lb, 10 yard leather rope holds 1,800 lb, so that's a multiplier of 18. A 9 lb, 10 yard silk rope holds 9,000 lb, so that's a multiplier of 90. An online search indicates a 20 gauge steel wire can hold 30 lb, although there's no clarification of if that's static or dynamic load. That weighs around 0.12 lb for 10 yards, indicating one thick enough to weigh 9 lb for 10 yards would support around 2250 lb, for a multiplier of either 22.5 (if the value given was for static) or 45 (if the value given was for dynamic).
I'm currently thinking of using dynamic load multipliers of 25 for cloth (100 for silk), 20 for pottery/glass, 22 for leather, 30 for metal, wicker, and wood. So, assuming a 3 lb container holding 3 cubic feet of volume (a cloth or leather backpack, or a rather thin urn or box), made of cloth it would hold up to 52 lb, made of silk it would hold up to 208 lb, made of ceramic or glass it would hold up to 41.5 lb, made of leather it would hold up to 45.75 lb, and made of metal/wicker/wood it would hold up to 62.5 lb. For static loads, these containers could manage up to twice these weights. Does this sound feasible?
Anthony's typically got a pretty good handle on physics, so let's go with that. Does anybody have datapoints we could use to determine what the constant is for each of the container types in LT? One of the possibilities mentioned in that thread was that a 3 lb cloth backpack holding 40 lb (dynamic load) probably wasn't too far off. That gives us a dynamic load constant of around 20 for cloth. What sorts of constants would be appropriate for other materials? We might be able to use ropes as a guideline, assuming cloth is comparable to hemp/manilla. A 1" diameter, 10 yard rope of that weighs 9 lb and holds 2,000 lb, so we'll set that as our 20. A 9 lb, 10 yard leather rope holds 1,800 lb, so that's a multiplier of 18. A 9 lb, 10 yard silk rope holds 9,000 lb, so that's a multiplier of 90. An online search indicates a 20 gauge steel wire can hold 30 lb, although there's no clarification of if that's static or dynamic load. That weighs around 0.12 lb for 10 yards, indicating one thick enough to weigh 9 lb for 10 yards would support around 2250 lb, for a multiplier of either 22.5 (if the value given was for static) or 45 (if the value given was for dynamic).
I'm currently thinking of using dynamic load multipliers of 25 for cloth (100 for silk), 20 for pottery/glass, 22 for leather, 30 for metal, wicker, and wood. So, assuming a 3 lb container holding 3 cubic feet of volume (a cloth or leather backpack, or a rather thin urn or box), made of cloth it would hold up to 52 lb, made of silk it would hold up to 208 lb, made of ceramic or glass it would hold up to 41.5 lb, made of leather it would hold up to 45.75 lb, and made of metal/wicker/wood it would hold up to 62.5 lb. For static loads, these containers could manage up to twice these weights. Does this sound feasible?
[Low Tech] Containers
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