Welding steel cable?
Welding steel cable?
(OP)
I have to go look at a job tomorrow where a client just had a horizontal cable rail installed on his deck. He stepped on one of the cables (I have no idea why) and it broke. He doesn't have confidence in the system anymore and he us bringing me in to look at it. He is saying that the ends of the cable are welded to a nut at each end and I'm wondering if welding steel cable like this is even possible w/o causing a problem? I know they make special adjustable ends for these systems, why one was not used i do not know.
FYI, I did not design the original system and I am being brought in after the face.
FYI, I did not design the original system and I am being brought in after the face.






RE: Welding steel cable?
Old school termination involves threading the rope end through a steel cone, spreading the wires, and pouring molten zinc into the conical cavity.
New school termination, industrial style, involves folding the rope over a thimble and securing the bitter end to the standing part with, typically, two wire rope clips. The thimble is then secured to a shackle or other end fitting.
The assembly is always ugly.
New school termination, sailboat style, involves swaging or threading some sort of end fitting over the bitter end. The wires may or may not be spread during assembly. You will probably want to visit a sailboat rigging shop to see what is possible for a residential installation.
You might consider including some very stiff compression springs in your cable assemblies, to allow enough deflection to limit the force applied by the next adult who steps on the rope.
Mike Halloran
Pembroke Pines, FL, USA
RE: Welding steel cable?
Mike McCann
MMC Engineering
RE: Welding steel cable?
RE: Welding steel cable?
RE: Welding steel cable?
I'd call that a reality check, and the wire failed under a small load.
RE: Welding steel cable?
I understand the customers concerns, however, these systems are not meant to be stepped on. The Building Code requires infill parts of railings to support 50# over a 1 square foot area (not 50psf) with the infill not spaced greater than 4" o.c. My interpretation of this is that the wire can not spread more than 4" apart under a 5# load on a 4" dia sphere. If we were to put springs on the end to allow for flex of the cable we wold be in violation of the building code.
RE: Welding steel cable?
Some building depts. do not allow these types of railing systems, although they do look sexy. The thinking being... instead of providing a safe, properly spaced (balusters), adequately strong railing system; they actually provide the rungs of a ladder for children to climb on, and over the top. You’ll find that when a 200# man stands on one of these cables, he is imparted a far greater (than his weight) tension in the cable, and getting large cable deflections too. When all the cables are properly tensioned, it is almost impossible to design the end posts to take the tension from all of the cables. Then you should also include the code req’rd. loadings on the posts, plus the potential loading your guy applied by stepping on the cable. I believe that most serious installers of these types of cable railing systems, do have swagging equipment as part of their tool kit. They cut the cable to length, thread it through the posts, and apply the last piece of tensioning hardware by swagging it onto the cable.
RE: Welding steel cable?
But, given your customer's experience, it's probably better to just install some seriously fat cables.
Mike Halloran
Pembroke Pines, FL, USA
RE: Welding steel cable?
RE: Welding steel cable?
I am being brought in to look at the existing conditions, whether or not the system is allowed is up to the architect.
The existing system used 1/4" dia bolts that were welded to the cable. The bolts were threaded through the steel angle with a cap nut applied to the finish end. Not much room for adjustment. Plus the cable/weld was ground smooth to fit through the hole in the steel angle. It took minimal effort to pass a softball through the cables. In fact you would easily pull two cables together with on hand. No effort had been made to pretension the cable properly. By my calculations, you would need a pretension force of 300#/cable in order for the system to work properly. Then there is the matter of the support posts which probably do not work.
Now I need to write a report with my findings.
RE: Welding steel cable?
RE: Welding steel cable?
RE: Welding steel cable?
It sounds/looks like you have some sort of a home made system which is supposed to look something like the several, more well developed and tested, cable systems which are on the market. If you used a regular nut first, on the bolt, and then cut the bolt a little long, once the tensioning was achieved, you could still put the cap nut on as a finish and locking device. Of course, you can melt a bolt and some cable together with a welding rod, there is just no way to assure the quality of that bonding (weld?). I have seen the ends of cables welded, or fused together by flame cutting, but this was primarily to prevent them from un-raveling. I would never trust these welds structurally. Neither material is particularly amenable to welding, and you have no way of knowing if you have properly fused each cable wire or just made a stress raiser on it with the welding process.
RE: Welding steel cable?
This is one acceptable solution, http://www.bosunsupplies.com/Machine-Swage-Fitting... but you do need to get your wire lengths right. That is most easily done on site, you'd need someone who can operate one of these correctly http://www.steelwirerope.com/WireRopeEquipment/Ove...
which will not be cheap.
An alternative would be a thimble and then either a crimped swage or a couple of U bolts, aesthetically not a patch on the long ferrules.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Welding steel cable?
RE: Welding steel cable?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Welding steel cable?
The systems I was looking at was produced by feeney and can be found at this link: http://www.feeneyinc.com/Architectural/CableRail-S... there are plenty of others out there for purchase. I don't know why the installer didn't bother doing any research into the subject.
RE: Welding steel cable?
RE: Welding steel cable?
You get what you pay for.
RE: Welding steel cable?
Also, it is possible (probable) that the cable was over-tightened to appear straight, rather than only tightened enough. At low angles of deflection, you need a lot of pre-tension to be straight under load. But above comments are correct, you really do need to start with a reputable "cable-handrail" supplier first.
RE: Welding steel cable?
ZCP
www.phoenix-engineer.com
RE: Welding steel cable?
As a side note, I spoke to the owners rep the other day and they were granted occupancy by the city (a very large city) with the cables in their existing condition. Don't know why the city inspector didn't say anything.
RE: Welding steel cable?
ZCP
www.phoenix-engineer.com
RE: Welding steel cable?
I don’t usually carry the water for the local building officials or code officials, but if it doesn’t look like an absolute piece of junk, they might overlook it, if they don’t have the negative inclinations about these systems that I mentioned in my earlier post. It looked about like the typical installation of this type of product, and that’s as far as they took it. They probably don’t test every connection to just short of failure; they probably don’t check the dia. of all the nails in the building, or the thickness of all the plumbing fittings etc., either. I’m more upset with them, that they think they should have my every calculation, design sketch and project note for their files. Two thirds of those people can’t interpret or understand them anyway, and I’m not in the business of giving plan checkers a short course in Structural Engineering and then answering their questions on minutia; but now they are their in the public domain for some hungry attorney to check and see if I dotted my I’s and crossed my tees, never mind the general correctness and completeness of my design. They don’t have a right to my inter-office memos, e-mails and love letters during the duration of that project either. Most of the time (many times) the project problem is the fault of someone other than the EOR, and it shouldn’t be so easy to fault the engineers because he left a calc. step out during his design, despite the fact that the calc. is basically correct. They are damn sure to keep us (P.E.s) responsible, we are the easiest target, they know they can get something out of our insurance. Other designers get off with a ‘please quit doing that kind of work and getting caught doing it.’ This poor product, intentional deception, should fall right back on the builder and the railing installer. If they provide a cheap product or system which doesn’t work, it is their fault, not mine, not your’s, because I happened to walk by the site one day, and I’m a P.E.