Bending metal trunking

[electrospark]

Hello all.

I'm doing steel trunking at work at the mo and to be honest all I have ever really used is manufactured bends. Now I need to do it the proper way and make my own.
I did it at college but that was a long time ago now.
So what i'm doing is running 150x150mm trunking with the lid on the top along a flat surface and then it needs to dog leg up only 40mm and carry on. (Think of it running upto a curb and onto the pavement so you can visulise it) Simple you probably say, but i can't for the life of me do it.
Can anyone remind me please?

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[holmslaw]

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[electrospark]

Thanks holmslaw. Thats great. I thought it was suppose to be a better way of using trunking as the earth continuity would be better due to possiblity of screws coming loose on pre made angles. No its a not a double set, at least I dont think so. This is the kind of what it will look like without drawing pictures. _____/---------- the upright only being 40mm so a very tight set..

 

[holmslaw]

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[JohnW2]

At some point it must revert to being vertical or horizontal thats why its a double set. And if you're doing it any other way sounds like c*** up time.

I think one of the problems here, and perhaps a reason why your suggested method might not be usable without some adapting, is that he has 150x150 trunking but only wants a 40mm 'step' in it - i.e. only just over a quarter of the depth of the trunking. However, whether one calls them bends or sets, you must be right that they are 'double' if one ends up parallel to where one started.

Kind Regards, John.

 

[ban-all-sheds]

When you draw it it does look as if 90° bends would not only be hard to achieve, they could make it difficult to get the cables through.

Guess it depends on what sort/how many there are, but visually it doesn't look as if anything more than about 22.5° would work.

 

[JohnW2]

When you draw it it does look as if 90° bends would not only be hard to achieve, they could make it difficult to get the cables through.

If one could achieve it (and that certainly would be far from simple), I'm not so sure that it would be that difficult to get cables through (easier one way than the other), since there would presumably be about 70mm of 'straight through' ('line of sight') depth common to the trunking on both sides of the dogleg.

Guess it depends on what sort/how many there are, but visually it doesn't look as if anything more than about 22.5° would work.

Indeed. I must say that when I wrote last night, my mind was probably thinking of fairly large angles. As you say, if one gets down to pretty low angles (hence a long length to the dogleg), it gets progressivley easier (and holmslaw's method would presumably work).

Kind Regards, John.

 

[ban-all-sheds]

Mmm.

I actually scribbled it late last night and posted this morning from memory.

Looking back, for some reason I drew it with the horizontal runs only 40mm apart, not 150, i.e. like A rather than B...

C is about 22.5°, BTW.

I did wonder, as you'd need to be pop-riveting in fillets anyway, whether just cutting the two ends at an angle as shown in D would be acceptable.

An earth conductor linking the sections would be a good idea, but even so....

 

[JohnW2]

Looking back, for some reason I drew it with the horizontal runs only 40mm apart, not 150, i.e. like A rather than B...

You're not alone. For whatever reason, 'A' is also what was in my mind - but 'B' would presumably be much easier to fabricate.

I did wonder, as you'd need to be pop-riveting in fillets anyway, whether just cutting the two ends at an angle as shown in D would be acceptable. ... An earth conductor linking the sections would be a good idea, but even so....

I guess you've partially answered your own question there - leaving some metal uncut leaves absolutely no doubt as regards electrical continuity. I suspect that a 'real engineer' would be shaking his/her head at this mention of pop-riveting fillets, and would regard welding as the only 'proper' way of doing it!

Kind Regards, John.

 

[ban-all-sheds]

Welding thin galvanised steel can be tricky.

You could probably spot-weld fillets without too much aggro.

As for joins between separate sections - no run over 3m long or with pre-fabricated bends, tees etc, is without them, and they are neither welded nor riveted.

 

[holmslaw]

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[scousespark]

Holmsalw has given the C&G 2360 method of constructing this double step.
I'd also add that electro could get a couple of short lengths of 3x3 to pack the trunking around the cut, to prevent it distorting while he cuts.

 

[ban-all-sheds]

Talk about dumb and dumber. Neither of you have a clue about site fabrication of trunking or the general requirements for a trunking installation.

I did wonder, as you'd need to be pop-riveting in fillets anyway, whether just cutting the two ends at an angle as shown in D would be acceptable.

"A is correct" - you're fired.

Do you mean incorrect? I'd already realised that wasn't right:

for some reason I drew it with the horizontal runs only 40mm apart, not 150, i.e. like A rather than B...

Welding galvanised metal - you're fired.

Welding thin galvanised steel can be tricky.

Cutting completely through the trunking - you're fired,

Seriously - what's actually wrong with that?

 

[MOGER4]

holmslaw has given the C&G 2360 method of constructing this double step.
I'd also add that electro could get a couple of short lengths of 3x3 to pack the trunking around the cut, to prevent it distorting while he cuts.
holmslaw is correct and to do it any other way would be wrong . the joints should be pop riveted and a copper connector screwed between points , i have always done trunking that way and so has everyone else from the UK , give it to one of our EU friends and you are garenteed a bit of a giggle ...not a lot have seen trunking let alone cut it , like pyro termination ...its a dying art , keep it holms you are now an artisain

 

[ban-all-sheds]

Seriously - it comes in fixed lengths, and manufactured bends and tees etc are available. As are plates for joining lengths together.

The bends and jointing plates are designed to screw on.

So on the one hand we have an entire system based around discrete components designed to be screwed together, and on the other we have people saying that the joins should be riveted.

But even if we ignore that, as soon as you admit the use of a system which has separate sections you are going to have to join them, by whatever method.

So if it's OK to take 2 lengths and join them together, why is it not OK to cut the ends of 2 lengths at an angle as shown in D and join them?

I know that you'd have to do something about the open end of the lower section, but again, trunking has end plates screwed (or riveted) on as a normal feature.

If that run was 30m long, and I drew it smaller, showing 10 lengths all joined together you'd say that that was OK, but if one of the 9 joins was at an angle you'd say it wasn't?