Buying SHS and RHS Steel.

[Wal]

Hi all.

I'm doing a bit of research into the cost and availability of the materials I want to construct my frame from. As this is going in my cellar (and welding is pretty much out of the question) I'm opting for a small squat floor-stander to maximise rigidity and compactness. It'll look something like this:


http://youtu.be/FCSTeJbSA3E

(There will be 8 heavy duty, adjustable, rubberised feet separating the frame and the concrete floor).

I'd like to use the following cold formed SHS and RHS section:

2 off 80 x 160 x 1400mm
4 off 60 x 60 x 220mm
4 off 60 x 60 x 1000mm

All wall thickness's = 6mm

I'm based in the North West and it seems that the only place I can buy the steel from (for under £200) is down in London - they won't deliver as they reckon the cost of delivery will far out-weigh the cost of the metal, which is fair enough.

I don't mind driving down to them, but before I do - am I missing out on a stockholder that would be able to supply these sizes up here in the North West?

Thanks for your help!

Wal.

[birchy]

Try local fabrication companies, they'll often supply you with cut lengths at reasonable prices as they'll have offcuts from bigger jobs. Regarding the cellar workshop, is it a Victorian house with the chimney breasts in the cellar? What I've done in mine is cut a hole into the chimney breast and fitted a 9" extractor fan. When welding, the smoke goes straight up the chimney.

[Wal]

Hello mate,

It's not so much the fumes I'm worried about (although, of course, I'd always guard against 'em) but getting the frame in and out once it's welded together in one piece. In it's current spec it'll weigh in the region of 110kg - not really a viable lift into and out of an awkward and steep cellar entrance..!

I've been in touch with several local fab companies, getting a response from any of 'em seems to be an issue. So far I've been emailing, maybe a call's a better bet...

Cheers.

Wal.

[birchy]

You're better off phoning them or going to see them. If you know anyone who works at a fabrication company, they might be able to get "mate's rates". Have you also tried online suppliers such as metals4u (http://www.metals4u.co.uk/Mild-Steel-Box-Section/49/products.asp), Hub Le Bas (http://www.hublebas.co.uk/products/product-overview.aspx?pid=56611ff5-7b16-4e97-ba92-6e743f4588a5) or one of the many eBay sellers? Another option to consider is your local scrap metal merchants as they'll have "offcuts", sometimes up to 2M in length!

Looks like you have plenty of steel stockists locally: http://www.yell.com/s/steel+stockholders-stockport.html. You should be able to get some prices within half a dozen phone calls.

[Wal]

>You're better off phoning them or going to see them.

Yeah, I'll have to start doing that - trust me, I've emailed loads of 'em (just more convenient that way for me) and I'm not getting anything back...

I think the sizes I'm after (particularly the 6mm wall thickness) aren't helping. Only found 2 companies on-line that list it in their catalogue.

I'll stick at it.

Thanks again.

Wal.

[birchy]

Ahhh, yes...you might struggle to get those sections in 6mm wall thickness. 4mm is probably more readily available. Dunno how critical your sizes are, but perhaps a 150 x 75 channel section (a common size) could be used instead of the 160 x 80 box?

[Wal]

>Dunno how critical your sizes are

Well, I'm probably over-engineering it a bit, but it's 6mm for two reasons - a. weight (as it's a small squat design) and b. thread-engagement for the screws that are holding the bugger together. The chunkier the better, as far as I'm concerned!

Cheers.

Wal.

[birchy]

How about using a thinner wall and reinforcing with either plates or tubes inside the box? The tubes go across the inside faces to prevent the walls collapsing when you tighten the bolts...

9147

[Wal]

Well, that's an option, I guess, but it'll probably be quicker and less hassle to bite the bullet and just drive down and collect the section I want - positioning a plate or a tube deep inside box section sounds like a bit of a ball-ache - especially as it'll have to be a tight fit for it's intended purpose (bracing the walls).

Cheers.

Wal.

[birchy]

Normal practice with the tubes is to saw them to about 0.5mm undersize a tack weld them inside the box. Obviously you can't do that if your holes are not near the ends of the box.

[Wal]

Cheers for that info.

Chances are that it's academic in this case, as the bolts are going through and into (threaded) adjacent walls as opposed to through the entire cross-section, so it's really more a case of thread engagement and being able to apply torque without distorting the walls of the box that are joined. Hence the 6mm.

Thanks for your advice.

Wal.

[GEOFFREY]

If using thinner wall box, you can drill right through enlarge the bottom hole to allow the tube to pass through end extend at the bottom by say 5mm. Bolt up (long bolts) very tightly and then weld the tube extensions to the underside. The use of lighter tubes would certainly make any future move easier. G.

[birchy]

In my honest opinion, I think that 6mm wall thickness on those lengths is way OTT. You'd have to use something like M16 or M20 bolts to match the shear strength of those sections. It is generally poor design to pass a bolt through a box section as it will crush the walls unless you use reinforcing tubes as suggested earlier. The next option is to drill a clearance hole in one face and use short caphead bolts and nuts so that you're tightening face to face rather than across the section. If you insist on having threads in the box section, you could also weld a nut or threaded block inside the box section. Or you could use rivet nuts: How to install a rivet nut (rivnut) and the tools you need - YouTube (http://www.youtube.com/watch?v=KeaMsvai0FA)
http://www.youtube.com/watch?v=KeaMsvai0FA

[Wal]

>The next option is to drill a clearance hole in one face and use short caphead bolts and nuts so that you're tightening face to face rather than across the section.

Indeed, that was the plan all along - fastening the adjacent walls together without having to compress across the section (hence no need for the tubes).

I did wonder how we all got onto the tubes...

Cheers!

[birchy]

Ermmm...so that brings us back to the beginning...why do you need such thick wall box sections? Is the frame going to be supporting several tonnes?

[Wal]

Heh, no, you're right. I'm not going to be supporting a great deal of weight. To re-cap:

The frame needs to be built in situ (in my cellar) and will at some point in the future need to be dismantled, so - welding is not really an option.

Bolting it together is very much an option. To avoid issues with rigidity and to give me a reasonably good starting point in getting the frame square, I have decided to build a squat floor level frame (as in the animation at the top of the thread). This means I'm using less metal, but I still need the frame to have a fair bit of heft to it. In it's current theoretical spec the frame alone weighs 110Kg. That's not super heavy, but it's also not that light. A reasonable compromise, I'd say. Using 6mm wall box section not only adds to the weight of the frame, but it also means that I'll have an ample 6mm of thread for the holes that I'll tap. That, to me, is important.

9168

Yes, I could use a screw and a nut through oversized holes, rather than tap into the box, but for now I'm favouring the former (threaded) approach with the screw passing through an oversized clearance hole.

Because box section has a slight curvature across it's profile (exaggerated in the pic below) using section with a thinner wall there'd be more of a danger of distorting it when torquing up the screws - 6mm wall will help to mitigate this.

9169

So while I am over-engineering this a bit, it's for the right reasons: weight and rigidity.

Anyway, it's all drifted a bit off-topic, I just wanted to buy some hollow section steel...!

Seriously, thanks for your posts and advice - it's all really helpful, but I have thought long and hard (well, for my pea-brain) about this, and I'm at the stage of having to go with the courage of my convictions.

(Guaranteed if I changed my mind to 4mm then someone would be along sucking their teeth and telling me how badly it's going to deflect and knock the earth off its axis etc...)

I've been planning this build for well over a year and I still haven't got a frame. It's embarrassing me now.

Cheers.

Wal.

[birchy]

Ok, no problem. I was only suggesting alternatives as you seemed to be making hard work of a simple job. I guess you could partially weld the frame and bolt the sections together but I can see that you have your heart set on bolting everything. Your best bet for the steel is to spend half an hour on the phone to those local companies I linked to earlier. You'll get something local as most of the steel manufacturers are 'oop North anyway.

[Spedley]

I'm planning on fitting most parts with a 'chemical metal' filling the gap. Once dried it should easily take the compressive load and allow for slight alignment errors.