1/4 X 3/4 pickets bowing after welding

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We are fabbing some rails that have 2 1/2" x 3/4" flat bar for the bottom and 1 1/2" round tube for the cap- the pickets are 1/4" X 3/4". The problem is that after tacking everything square and making sure everything is straight when the guys weld them out the pickets seem to grow- we have tried to cut them a 1/4 short to allow for some expansion- but this doesn't work 100%. Anyone had any experience with a set up like this?
Reply:I think 1/4" is too thin for a picket. The precision required to make such a flexible picket not bow will be difficult to achieve.Are all of them bowing? Or are most of them bowing but a few aren't?If it's most but not all, your problem is probably inconsistent length on the pickets, which leads to inconsistent shrinkage when they are welded. The pickets must be cut just right, within less than 1/16" error and fit tight with no gaps before welding to insure even shrinkage.What about manually bending them straight after welding? Or is the bow too much to overcome?Last edited by fortyonethirty; 08-09-2012 at 11:08 AM.Ian TannerKawasaki KX450 and many other fine tools
Reply:I think 1/4" is too thin for a picket. The precision required to make such a flexible picket not bow will be difficult to achieve. This is not my choice- there are landscape architects and the main architects who designed this railing.Are all of them bowing? Or are most of them bowing but a few aren't? Just a few here and there.If it's most but not all, your problem is probably inconsistent length on the pickets, which leads to inconsistent shrinkage when they are welded. The pickets must be cut just right, within less than 1/16" error and fit tight with no gaps before welding to insure even shrinkage.If we make them fit perfect- they grow too much and bowWhat about manually bending them straight after welding? Or is the bow too much to overcome? The ones that are just pulled out of square from welding straighten out pretty nice with a few taps of a rubber mallet- but some "grow" too much and have to be cut and re-welded.We have about 200 feet more of this rail to build and I would like to get a good technique down to eliminate this problem. I hate this design, but this is what they want.
Reply:here's a photo. Attached Images
Reply:What is the wall thickness on the top rail? Could you increase it to help resist the pull? If you've got some straight and some bowed there must be an inconsistency somewhere. Have you tried using a strict pattern for the welding? Like, starting near the posts and working in to the middle of a section?"If we make them fit perfect- they grow too much and bow" When they were fit tight did they all grow too much? If they all grow evenly, or following a pattern like bowing more near the middle of a section, maybe you could try to pull them straight by bowing the top rail up or the bottom rail down with some heat shrinking.What about doing the pickets first and then adding the posts later?What about heat shrinking the bowed ones?Ian TannerKawasaki KX450 and many other fine tools
Reply:Originally Posted by fortyonethirtyWhat is the wall thickness on the top rail? Could you increase it to help resist the pull? If you've got some straight and some bowed there must be an inconsistency somewhere. Have you tried using a strict pattern for the welding? Like, starting near the posts and working in to the middle of a section?"If we make them fit perfect- they grow too much and bow" When they were fit tight did they all grow too much? If they all grow evenly, or following a pattern like bowing more near the middle of a section, maybe you could try to pull them straight by bowing the top rail up or the bottom rail down with some heat shrinking.What about doing the pickets first and then adding the posts later?What about heat shrinking the bowed ones?
Reply:I do railings like these all the time, and yes if i just welded it up as shown in the picture the heat will distort that flat bar and it will bow and twist.What i did was to Use a steel RSJ (Beam) The lenght of one panel and Clamp the Bottom Flat bar to the beam, Not only does that prevent movement but the beam also acts as a heat sink drawing some of the heat away from the work, For the Rounded Top use some heavey 10mm Angle Clamped to the round tube, this will doe just the same as the beam.secondly make sure your welds are not overly hot see if you can turn the amps down a touch and Stagger the welds, ie, weld one miss two, weld one, miss two etc.. This will help spread the heat outbeen doing railings like this for years without problems
Reply:Originally Posted by Gerry1964I do railings like these all the time, and yes if i just welded it up as shown in the picture the heat will distort that flat bar and it will bow and twist.What i did was to Use a steel RSJ (Beam) The lenght of one panel and Clamp the Bottom Flat bar to the beam, Not only does that prevent movement but the beam also acts as a heat sink drawing some of the heat away from the work, For the Rounded Top use some heavey 10mm Angle Clamped to the round tube, this will doe just the same as the beam.secondly make sure your welds are not overly hot see if you can turn the amps down a touch and Stagger the welds, ie, weld one miss two, weld one, miss two etc.. This will help spread the heat outbeen doing railings like this for years without problems
Reply:I see where your coming from Eric, Only thing left to do is as you say do a bit at a time, keep the heat spread out and try not to have the welds too hot,I give it a week after they are fitted for kids to start bending the pickets You did your best you advised the customer for a more appropriate material spec, they chose to ignore your expertise, fair enough, Just make sure you get paid, and they don't use the excuse of the bent pickets not to pay
Reply:I can almost make two pickets touch by squeezing with my pointer finger and my thumb. I even showed the contractor when i dropped off the sample. There is a 43 foot straight run of this rail from a wall to a corner- I'm wondering how much side to side wiggle its going to have with no type of stiffeners anywhere. All I can say is I told you so.
Reply:Ditto what Gerry said. The other thing you could do is notch the bottom rail with a rect. ironworker punch, insert the picket and lightly weld on the bottom. Might not be worth the wait for only 200 feet though.
Reply:Originally Posted by Eric CI can almost make two pickets touch by squeezing with my pointer finger and my thumb. I even showed the contractor when i dropped off the sample. There is a 43 foot straight run of this rail from a wall to a corner- I'm wondering how much side to side wiggle its going to have with no type of stiffeners anywhere. All I can say is I told you so.
Reply:Originally Posted by walkerDitto what Gerry said. The other thing you could do is notch the bottom rail with a rect. ironworker punch, insert the picket and lightly weld on the bottom. Might not be worth the wait for only 200 feet though.
Reply:Originally Posted by BrettDid you put your concerns in writing? You may want to consider it ...Brett
Reply:Originally Posted by Eric CWe have about $150,000 in metal work at this house, plenty of paperwork!
Reply:Are you sure your cap or bottom rail is not bowing, squishing your pickets.  Perhaps try pre bending the cap.Since you said  only a few were bowing is there a pattern, like more pickets bowed further away from the posts.
Reply:Originally Posted by Eric CWe have about $150,000 in metal work at this house, plenty of paperwork!
Reply:Originally Posted by tapwelderAre you sure your cap or bottom rail is not bowing, squishing your pickets.  Perhaps try pre bending the cap.Since you said  only a few were bowing is there a pattern, like more pickets bowed further away from the posts.
Reply:Originally Posted by Gerry1964I can imagine, well i guess the buck will fall with the landscape architects office, you i'm sure have the drawings and material spec, basically you did what was required.Sometimes the landscape architects idea of a job differs greatly from what the customer expects, sad really because for the sake of a few $$$'s more for the bigger material.... Whats the finish on them, Eric, lets hope they are not Galvanised   As i can't imagine any one of those pickets coming out without a bend
Reply:i need to post this before i am banned.   nice looking rail.  have you tried cold rolled material.  that looks like hot roll.
Reply:I did one of those paperless jobs once.    Lasted two weeks before i told them either make me drawings i can print out or im walking from this job and you can sue me.IT was a NIGHTMARE!Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Originally Posted by Eric C  It takes so little to push them out of straight, the smallest amount of force will bow them.
Reply:You want to Put a sign on themBuilt by an expert, Designed by a Donkey
Reply:Whats gonna happen when a kid spreads those pickets far enough to get their head through it but can't get it back out. This design is just nonsense.