straighting?

Date 12-22-2007 04:39

Hello all an thanks in advance for help on this one.Heres the deal,stair stringer made of 1/2 plate an 3/4 plate.Each stringer is about 11 feet.The 2 thickness are joined together to make a channel.The leg of the home made channel is 3/4.The face is 1/2.Width of said channel is about 2 feet an the legs are 4 inches.The legs are double beveled at about 30 degrees on one side .That said side connects to the 1/2 plate to make up the channel.During welding 2 stringers are back to back an clamped off to help from bowing.Welds are jumped around until fully welded.Problem-when releasing clamps after cooling period legs look out of square with face.I feel its more of the 1/2 face plate bowing an making the leg look out.Question-How would one go about heat srinking or applying heat to straight them back to pre weld form.There not out by much but enough to notice.Also they are made of mild steel.All opinions welcome.Thanks.

By swsweld (****)

Date 12-22-2007 19:12

That is one stout stair stringer. Is it for elephants? :) We do not know what you have access to in your shop to assist you in straightening the stringers out. I would suggest positioning them back to back with a steel spacer (beam or channel full length or cut several tubes and tack between members) Then apply heat with two or three rosebuds to the web. With three or four sets of clamps or dogs spaced out evenly tighten down.
I would over compensate slightly. If this works duplicate process with the other stringer. If you are fitting treads in shop you can try to pull the bow out and put extra welds on the treads to keep the bow out. Use come a longs on top and bottom flange apply heat if necessary then weld tread to stringer. Slide come a longs from tread to tread to straighten stringers.This is if the web is bowed out and not in.

I've straightened many warped stringers in the field like this but never with home made or stringers that thick.

Just curious; why not standard channels and why such heavy stringers?

Lot of shop fabricators on here with better advice to offer than mine. Good luck with it.

By monsoon12 (**)

Date 12-22-2007 22:14

Thanks swsweld -As for why so heavy-thats what they wanted i was told.Hey there paying right lol.