Material expansion

[TEO]

Hi everyone, I'm looking for some advice please:

Material expansion/contraction:

I have 3m lengths of 6mm mild steel angle that will make a continuous hand rail along the top of the cabin of my narrowboat. The cabin is of 3mm mild steel and roughly 14m long.

My plan is to tack the first 3m length in place in the middle of the cabin top, then fix it permanently with 3 or 4 inch beads (prob. 3 or 4 passes per finished bead) spread at roughly 300mm centres, alternating those beads between the inside and the outside of the angle, if that makes sense. The edge of the angle is prepped with a chamfer to aid penetration but limit the power so that I'm not blowing holes in the cabin. I was thinking of working from the center out.

I'll then butt the second and third lengths to the ends of the first fixed length and so on repeating the process, working towards the ends of the cabin. There'll be a gap of 3 - 5mm between the ends that I'll fill as a route weld once everything's had a chance to cool down.

The question is; will the 3-5mm gap be enough to allow for expansion and contraction? I'm afraid that if I go for a larger gap I'll not be able to fill it.


Many thanks in advance for any thoughts.
T

 

[rtbcomp]

@TEO

I've deleted the 2nd part of this thread because it needs to be put in "Welders and Welding Machines"

http://www.mig-welding.co.uk/forum/forums/welders-and-welding-machines.15/

to keep the thread tidy.

Thanks.

 

[TEO]

@TEO

I've deleted the 2nd part of this thread because it needs to be put in "Welders and Welding Machines"

http://www.mig-welding.co.uk/forum/forums/welders-and-welding-machines.15/

to keep the thread tidy.

Thanks.

Ok, appologies, T

 

[TEO]

Gottcha, thanks.
T

 

[nickk]

you risk causing ripples in the roof,could you weld lugs at 90 deg to the angle [on a bench/against a big piece of box] & then bolt the lugs to the roof.

 

[TEO]

you risk causing ripples in the roof,could you weld lugs at 90 deg to the angle [on a bench/against a big piece of box] & then bolt the lugs to the roof.

Hi nickk, thanks for coming back on the question. Yes, there is a danger of ripples but I'm hoping that any ripple will be limited by the side of the cabin. The hand rail is going on as a continuation of the (not quite) vertical cabin side so any pull will have some resistance from both the top and side. Of course the result could be twist! Fingers crossed going slow, allowing things to cool, lots of small tacks and not so many beads will work.

I'm sure you're right that lugs would eliminate any danger of ripple but then I'd have stacks of extra holes in the roof, points of interruption of the drainage and unless there were lugs going down the side as well, it'd lack the necessary strength. And putting lugs down the outside would be unsightly and involve even more holes, Something I'd rather avoid.

I realise that it'd be far easier if I had a drawing or pictures for you to look at, I'll see what I can do over the next few days.
Thanks again.
T

 

[nickk]

being that the proposed rail is twice that of the roof,the distortion risk increases.

 

[TEO]

Sure does, don't think it can be avoided though. Not in the time I have available anyway.
Cheers,
T

 

[Kent]

It will make a somewhat ugly handrail. If you don't minute saying too much
Why when you could avoid all that by making one up in say nb pipe that will look a lot better and be easier on the hand?

OK if you go the rsa route I should fit the whole thing up tacked - before I started putting in that chain stitch. The tacks should mark the end of each stitch imo.

I think it's unlikely your barge has 3 mm on the roof - most are 5 mm and the issue is getting enough bite Into the roof when your only sticking. I should under the risk of it ever breaking off run hot and get the penetration into the roof the rsa upstanding on am edge should present little risk of under penetration.

Your roof is very likely spray foam backed and will set on fire during the welding process
Under no circumstances should you do this without a guy inside and with the ceiling underdrawn - it's just asking for trouble

No I have to say nb pipe and a number of screwed connections will be easier and safer. Though I haven't seen the job and there is a lot of guessing going on from me

 

[Liquid Metal]

3 or four inch beads?...... 3or 4 passes per finished bead???

If you do go with the angle iron idea, dont bother with any more than one single bead for your stitches, complete waste of time any more than one pass,... why would you want to build up a bigger fillet if you're welding the angle to 3mm sheet!!

 

[TEO]

It will make a somewhat ugly handrail. If you don't minute saying too much
Why when you could avoid all that by making one up in say nb pipe that will look a lot better and be easier on the hand?

OK if you go the rsa route I should fit the whole thing up tacked - before I started putting in that chain stitch. The tacks should mark the end of each stitch imo.

I think it's unlikely your barge has 3 mm on the roof - most are 5 mm and the issue is getting enough bite Into the roof when your only sticking. I should under the risk of it ever breaking off run hot and get the penetration into the roof the rsa upstanding on am edge should present little risk of under penetration.

Your roof is very likely spray foam backed and will set on fire during the welding process
Under no circumstances should you do this without a guy inside and with the ceiling underdrawn - it's just asking for trouble

No I have to say nb pipe and a number of screwed connections will be easier and safer. Though I haven't seen the job and there is a lot of guessing going on from me

Hi Kent,

Thanks for your thoughts and apologies for the delayed reply.

I prefer a slightly more trad style rather than the round tube handrail, each to his own. Also, the new angle iron will help lead the eye away from a v slight kink in the side where the heat of the fire caused a little distortion.

Tacks and stitching, yup that's pretty much the way it happened, penetration wasn't an issue in the end and so far there's been no noticeable distortion.

It's a narrowboat not a barge and perfectly normal for narrowboats to have 3mm cabin sides and roof though in fact this is 1/8th", I've already replaced a 3m length of cabin roof, I've stripped it out to a shell, shot blasted the outside and just finishing the less structural welding.

Good point about the spray foam insulation though this one's of an age where they used expanded polystyrene (V nasty) most of which evaporated in the fire that caused the damage to the steel which is why I'm doing all this work.

Strangely when I've asked about what happens to the spray foam when people replace the sacrificial anodes there doesn't seem to be a problem but suspect that's just about position of the anodes below the waterline and also below the insulation.

Anyway, thanks again, always good to have different thoughts, apologies also for the lack of pics, would have saved a lot of guessing.

Cheers,
T

 

[TEO]

3 or four inch beads?...... 3or 4 passes per finished bead???

If you do go with the angle iron idea, dont bother with any more than one single bead for your stitches, complete waste of time any more than one pass,... why would you want to build up a bigger fillet if you're welding the angle to 3mm sheet!!

Hi LM,

Thanks for your comment.

Ignorance, that's why and why I was asking the question.

You're bang on, it's turned out fine with a single bead between tacks. Initially I was worried about filling the joint as nothing's flat, straight or even on a narrowboat and the gap between the angle and the roof top varies between 1 and 4mm. At the ends where they've added a 10mm strip to the 3mm roof and sides to give a comfortable hand hold, the gap is up to 12mm. So of course rather than many wasteful passes I've welded in bits of rb and strap where the gaps are too big...just took me a while to suss it, Duh!

Of course pics would have helped, I may sort some out later.

Cheers,

T

 

[Kent]

Hi Kent,

Thanks for your thoughts and apologies for the delayed reply.

I prefer a slightly more trad style rather than the round tube handrail, each to his own. Also, the new angle iron will help lead the eye away from a v slight kink in the side where the heat of the fire caused a little distortion.

Tacks and stitching, yup that's pretty much the way it happened, penetration wasn't an issue in the end and so far there's been no noticeable distortion.

It's a narrowboat not a barge and perfectly normal for narrowboats to have 3mm cabin sides and roof though in fact this is 1/8th", I've already replaced a 3m length of cabin roof, I've stripped it out to a shell, shot blasted the outside and just finishing the less structural welding.

Good point about the spray foam insulation though this one's of an age where they used expanded polystyrene (V nasty) most of which evaporated in the fire that caused the damage to the steel which is why I'm doing all this work.

Strangely when I've asked about what happens to the spray foam when people replace the sacrificial anodes there doesn't seem to be a problem but suspect that's just about position of the anodes below the waterline and also below the insulation.

Anyway, thanks again, always good to have different thoughts, apologies also for the lack of pics, would have saved a lot of guessing.

Cheers,
T

To me all the long boats on our waterways are barges. My mate owns a canal boat buisness and he calls them all different but to me and thousands of others they are all simply " barges" lol

The foam is super nasty for fires it must be considered at all stages - likewise derv. Battery banks, inverters and propane tanks!