By 99205
Date 01-01-2011 01:27
Edited 01-01-2011 06:21
The last time I built a long handrail like that, I fastened the ends of the top, to a I beam and shimmed it every 2 feet until I had about 6" of shims in the middle and left it shimmed until we were finished with the welding. The handrail was 20' long so if you shim your set up may be a little different. We got lucky on the shimming sequence because the handrail turned out perfectly straight. As we reflected on the job we decided on the next handrail we would only put 1/4 long welds on the outside edges of the pickets. Good luck on yours and I hope it doesn't turn into a big shiny banana. One added thing here, I would check the spacing on those pickets to make sure they comply with code.
One of the marine fabricaters in Annapolis Md. built a jig with a bottle jack to unbend the area at each picket, as the distortion You are worried about is an issue.
That is a whole lot of picket welds, the marine stuff the supports are usually feet apart, and on many railings You can see the waves.
KATO, another marine fabricator in Annapolis [and a really good one] uses extremely narrow [5/32"?] welds, they look like they use verry little filler if any at all, .060 wall tube.
You are using a much thicker wall tube than the marine guys usually use, I don't know if that will reduce warpage or not.
I assume You are using pre polished tubing, be sure all Your fixturing is covered with tape, cardboard, wood, plastic etc. to prevent carbon transfer from steel, as well as scratches.
Because it is round it complicates it a bit. On interior railings (square) you can just weld along the direction of the rail and leave the horizontal fillets out...that reduces the distortion greatly. Since you are using round you do not have that option. The thick wall will help quite a bit. If your copes are PERFECT fits, can you get away with only couple small 1/4"-3/8" welds per picket end? If you must weld them solid, mig will help reduce the distortion greatly, GTAW will induce it. I recommend fixturing the entire rail to a table, either tacked down or clamped to dogs. Use some kite string to make sure your top and bottom rail are perfectly straight before you introduce the pickets, get it jigged down well, tack in all the pickets first and use a skip weld pattern.....let the whole thing cool before you flip and repeat. Now remember that the weld on the top of the picket will pull directly against the weld on the bottom of the picket so if you do them together they will draw against each other. If you get some distortion a brazing tip in the torch a little careful pressure should work it out. You can still GTAW if you want small pretty welds, just remember it is really ornamental work and keep the heat to a minimum. Blue scotchbrite is alright for getting your color back if it is a brushed finish.
Hope this and the other advice helps, good luck with it.
Tommy