controlling distortion

[nickk]

i have a 3.6m length of 200x75 channel,& i need to weld 12 pieces of 50mm angle 180mm long, across the web[external] @ equal centres ,by stitch welding, the last time i did this i used screws,but would like to weld this time,i can't remember my technique previously yet thought i clamped down on packing each end [to a hefty beam] to maintain straightness , anyone have ideas on spacer thickness please.

 

[tinman123]

based on no engineering formulas what so ever bar the few times ive needed to do it, personally id try some 20-25mm in the middle and some 10-15 further out to give it somewhat of an even bend, a bit of insurance really and see what it look like, indeed less might do but its 12' long too.
i dont know if there is a formula for it but if there is id say its not simple, trial and error really.

 

[Kent]

Chain stitch and clamps ( lots of them) or similar fixtures / dogs etc
I don't know the dimensions and never can understand such verbal description much prefer a drawing as I could misunderstand and end up spouting pure garbage

 

[tinman123]

ah yeah, your either drawing the line or following it i suppose.
about here i make a lot of it up as i go along, it seems to get the job's done anyways but if your the kind that needs a drawings then its best to have one for sure.

 

[Kent]

The thing is how do we know the inclination of the angle or where it places on the Web without one? Heck yes drawing required

 

[nickk]

problem is can't do drawings or send photos onto this forum,my partner & friends have all tried to help-to no avail,anyway the cleats are to fit across the web @ 42 degrees equally placed widthways,i will plug weld thru angle face.

 

[tinman123]

have you tried plug welding this before and know it will pull or are you afraid it will.
if your welding on 2" angle its only going to be so strong anyways so you would get away with 2 plug holes would you?

if your only plug welding them and not sowing them up i cant see it pulling that much tbh but if it is stringers your making up
try a 10-12mm plate in the middle then so, it might suit that type of weld better
the web of the channel should hold it fairly good id imagine after that.
again, take from this what you will, im only saying the way id chance it, 90% of the time i dont have drawings.

 

[Welderpaul]

It's a dark art. I'd start with 60/80mm and take it from there.

It depends on how quick and hot you weld as to how much pre-bend you need.

 

[nickk]

thanks all,will report back with outcome.

 

[nickk]

result ,i welded the first one today,placed inside the web of a length of 305x165,toes down piece of 25 shs in the centre then ends clamped till they touched the u/b surface,welded the cleats in alternating sequence,left to cool ,unclamped -straight as a straight thing

 

[tinman123]

cool, nice to see it worked.
as paul said, its kind of a black art but the good results are satisfying.

 

[nickk]

2ND one done & straight as a die. no flukes then lol