Glenn Posted October 4, 2018 Share Posted October 4, 2018 With arc welding the weld is as strong as the parent stock, or the tinsel strength of the rod being used. How strong is a forge weld, or fire weld done by a blacksmith? How do you calculate the WLL working load limit of a forge welded chain? The question came up in a discussion of hand made forge welded chain. Quote Link to comment Share on other sites More sharing options...
SLAG Posted October 4, 2018 Share Posted October 4, 2018 Tensile strength? Quote Link to comment Share on other sites More sharing options...
JHCC Posted October 4, 2018 Share Posted October 4, 2018 Yeah, tinsel doesn't have much strength at all. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted October 4, 2018 Share Posted October 4, 2018 Depends totally on how well the forge weld was done, as anchors and anchor chains were forge welded for centuries they were considered to have a "strong weld". If done to the absolute highest standard it's not as good as the parent metal it *IS* the parent metal. The metal atoms share electrons. If done poorly then there is crud/cold shuts in the weld boundary and an errant blow with a sledge will break the heel off your anvil. Quote Link to comment Share on other sites More sharing options...
dickb Posted October 4, 2018 Share Posted October 4, 2018 ... or your foot. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted October 4, 2018 Share Posted October 4, 2018 If you are forge welding your feet, I have grave doubts as to your future in this craft. Contrary to popular misspellings: anvils have heels not heals! Quote Link to comment Share on other sites More sharing options...
SFC Snuffy Posted October 5, 2018 Share Posted October 5, 2018 As with any hypothetical situation, you must make some assumptions. If the forge weld is perfect, or ideal, then there is no weld seam. The material is homogeneous and strength will be rated according to the cross-section of the material, yes? Mokume-gane techniques can produce solid-state welds even between disparate metallic solids. I don't know enough about modern welding to to know how that compares. My limited experience with a MIG welder leads me to believe that you can't effect a large lap weld in the same way that you can forge weld, but I could easily be mistaken. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted October 5, 2018 Share Posted October 5, 2018 Well, the main difference to me would be the potential for inconsistency. A chain, famously is as weak as it's weakest link. One bad weld, however it was done would make for a weak chain. For calculating working load strength, I suppose you could always do it the same way they used to. Test some to destruction with huge weights. Of course, breaking strain is funny. I was always taught with rope that the longer it is, the less tension it can handle safely. Not sure it applies to chain. And of course working limits are only a fraction of the breaking strain. Quote Link to comment Share on other sites More sharing options...
mcostello Posted October 5, 2018 Share Posted October 5, 2018 Why is a longer rope weaker? Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 5, 2018 Share Posted October 5, 2018 A long rope cable or chain isn't actually weaker, however it's a common term used in error. What is meant is a longer rope cable or chain has less carrying capacity. Eg. 1" manilla with a yield strength of approx 2,700lbs. 3x it's working load can't carry that much at 100'. Two reasons for rope and cable (yarns) is stretch which reduces strength by cramping fibers and it has to carry it's own weight. Stretch crimping in yarns is primarily caused by twisting under load. Counter rotating cables are used in high load applications for a couple reasons: #1 the load doesn't spin and multiple cables don't twist together in a snarl. #2, Length is more predictable for load positioning, you can count turns on a drum and get very close. Chain's capacity is reduced with length because it has to carry it's own weight. If it's stretching measurably you've exceeded it's yield strength. Yield and breaking strength are two different numbers as well. There is a LOT written about cable: strength vs. length, span, etc. position, how it's bent, etc. It's been a long time since I worked with the stuff daily and my memory is too dented for specific details. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Glenn Posted October 5, 2018 Author Share Posted October 5, 2018 19 minutes ago, Frosty said: What is meant is a longer rope cable or chain has less carrying capacity. Eg. 1" manila with a yield strength of approx 2,700lbs. 3x it's working load can't carry that much at 100'. Can we extrapolate that to mean that a 1 inch manila rope if long enough will fail under it's own weight with no load applied? And is the same being true for rope, cable, and chain? Then you have to ask, how long is long? Does this still apply if you link shorter sections of rope, cable, and chain together? Say 5 each 20 foot sections of rope, cable, or chain to make a 100 foot total length? Quote Link to comment Share on other sites More sharing options...
Frosty Posted October 5, 2018 Share Posted October 5, 2018 Of course. #1. Working length for load can be found on charts. If you're pushing the envelop use the chart made by the manufacturer of the line you're using. They all have a significant safety margin, manilla is 300% but don't push it there are too many factors to list even if I had my rope and cable book to hand. Ambient humidity being one. Stretch and twist will be less a factor joining cables but ANY knot weakens it so a bunch of short sections will be significantly weaker. Not just lower load capacity, I mean WEAKER. The only way to joining cable without significantly weakening it is over a thimble or proper splice, eg. untwist and weave the strands or even the fibers together. IIRC the rule of thumb is a splice needs to be 12x the dia. of the cable. Do NOT quote me on that one we never spliced cables, we discarded it if damaged. It wasn't legal for us to splice cable, including rope. We were allowed to splice loops in hollow marine line with a fid. Different thing but no question better than tying knots. Chain is only slightly different. If you use 1/2 links to splice then that is the weak link. If you use chain connection hardware it may or may not effect strength at the join depending on the hardware however it will increase the weight / length. Chain likes being bent over things even less than cable, say wrapping it around something to pull, use a shackle. Shackles are NOT for splicing chain. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
SJS Posted November 30, 2018 Share Posted November 30, 2018 Thomas I thought I remembered that James Nasmyth had done testing that said that even a good weld only had 80% of the strength of the parent material? But of course when I went looking all I found was a Scientific American article where Nasmyth mentioned that eight of ten fractured links were due to "defective" welds where the scoria (oxides) was not ejected properly... Not quite the same thing Quote Link to comment Share on other sites More sharing options...
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