Steel rolling roof pics.

[ollypenrice]

Here are the mini-girders I made to span the 2.6 metre width of the forthcoming observatory. I couldn't use larger steel section because my welder wouldn't cope but these take a person's weight easily.

I now need to rustle up some muscle to help carry the old roll off to its new site...

Olly

[Leo.A]

With a restrictive welding current available to you (and low duty cycle), the strongest method is to chamfer the edges of the steel with a grinder (both edges) and build up multiple levels of weld. You start with the initial one run in the bottom of the chamfered joint, in the middle of course, then after a slight grind, chip. wire brush (to prevent inclusion of slag unless using a gas assisted MIG welder (gassless leave splatter) you layer the weld over the initial weld in two parallel runs. Then, depending on the thickness of the steel, run 3-4 over the two, not trying to excessively widen each individual weld which could weaken the joint. Not forgetting to grind and clean up between layers.

It may take much longer but it will allow you to use any steel you want for maximum strength regardless of the capacity of your welder.

Don't forget to leave a small root gap at the centre, which is a small gap between both plates for weld penetration. If you have chamfered the plates to have a contact face of, say, 2mm, you would leave an equivalent gap between both plates for the initial weld. You can chamfer one, or both sides of the plate. If you chamfer both sides, do equal, alternative runs on both sides to prevent buckling of the steel. With the first run of weld, also slightly offset the plates so the heat pulls them straight. If you set them both perfectly flat to start, the first run will tend to draw them together and you will have a slightly buckled finish (a V on the surface of the plates instead of them being flat).

Welding is one of those time consuming tasks and even though I have qualifications in the field (never employed as welder though), I always do a couple of practice runs on scrap before I tackle any task. Then again, I don't spend a lot of time welding regularly.

Oh, the cleaner the steel, the better the weld (I see you already know that), and NO, you can't weld over paint despite everyone saying the welder burns it off.

[oldturk]

Excellent welding advice. Was very impressed with what I saw of Olly's previous welding!

[ollypenrice]

Thanks to both, there! Alas rain has stopped play since I now need to finish the roof outside - and MIG voltages, rain and humans are best kept well apart...

Olly

[Leo.A]

Thanks to both, there! Alas rain has stopped play since I now need to finish the roof outside - and MIG voltages, rain and humans are best kept well apart...

Olly

A smart man indeed!

20 years before I decided to undertake an engineering fabrication/welding course (3 year) I purchased a small stick welder and decided to teach myself to weld. I had done small welding jobs at various jobs and had the basics, nearly. I purchased my welder, took it home, organised some steel for a small project, then it started to rain. I waited for the rain to stop, walked out bare footed, plugged welder in, stood one foot in a puddle of water on concrete, other foot on the steel to hold it in case I stuck the rod, and struck up an arc.

I shouldn't have to explain what happened next, needless to say I never did it again, and never welded with bare feet again either.

Good thing I already had qualifications as an electronics engineer and also studied electrical engineering, otherwise I would never have figured out how stupid what I had done was....After the act of course.

You don't need brains to be smart! :Haha::Haha: