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to weld or not to weld?
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miles&Jules
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to weld or not to weld?

So welding makes metal weaker but not welding would mean you would have to bolt everything together. So is it just experience that tells you how much to weld?

Im planning to re-weld kojack and give it a new base plate. So should I fully weld up the side joins solidly (like it did last time) but add triangles on the inside or should I just partially weld the outside then weld the hell out of the triangles on the back?…. Its Bizalloy to.

I can't remember if i pre heated the bis last time …maybe that is why the welds didn't hold.
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Post Thu Jan 15, 2015 5:57 pm 
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Nick
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I would grind off the old weld, re-weld the full joint an also add the triangular backing fillets.
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Post Thu Jan 15, 2015 6:30 pm 
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Glen
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The less it gets welded the better for hardness, but having it rip off is much less ideal than it bending some - therefore weld the hell out of it Smile
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Post Thu Jan 15, 2015 7:54 pm 
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miles&Jules
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righto thanks guys….lucky i bought Jules a new welder for christmas. Very Happy
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Post Thu Jan 15, 2015 8:15 pm 
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Glen
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Nice! What one?
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Post Thu Jan 15, 2015 8:18 pm 
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miles&Jules
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an sca inverter model

http://www.supercheapauto.com.au/online-store/products/SCA-Welding-Arc-Inverter-140-Amp.aspx?pid=295861#Recommendations

its actually the cheapest inverter i could find…Jules hasn't tested it yet …i though i better let her have first go he he
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Post Thu Jan 15, 2015 9:04 pm 
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Spockie-Tech
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You can make a nice scratch-start TIG for steel (and Stainless, just not Aluminium) out of inverter-arcs with the addition of a manual-gas valve TIG torch and a bottle (dont bother with the disposable size ones, they last about 5 minutes).

I had one very similair to that one, with the TIG torch, then upgraded to a High-Frequency start TIG, (which makes it easier for welding n00bs to get an arc going without sticking the electrode.), thinking that would make it heaps easier.. It did.. a *bit, but not hugely..

Then I decided to get my stainless steel fuel tank welded by a Pro stainless steel fabrication place (rather than trust my own average welds to contain petrol), and guess what theyre using ? A simple little inverter scratch-start Arc/Tig with manual gas valve TIG torch on it. just like that one and the one I had.. and the guy proceeded to knock out beautiful welds without a single electrode stick. Smart arse Smile

Of course 20 years of experience helps, but it shows you dont need a fancy machine with enough practice.

Stick/Arc Welding is good for building trailers and shelves and big heavy stuff, its fast, cheap (no gas) and portable, but its hard to do precise work on the fairly light weight frames and armour of featherweight or smaller robots with. but add a $90 manual-gas Tig torch and a bottle of gas, and with a bit of scratch-start practice, you can do much finer work..and still flip back to stick/arc mode when you want to glue some big stuff together quickly or have run out of gas Wink

TIG is nicer to work with too, Its quiet, practically smoke free and you dont end up with messy slag everywhere which seems to be a mix of dirt, grit, and dust after you knock it off, it gets everywhere.
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Post Thu Jan 15, 2015 10:29 pm 
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miles&Jules
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ah ..that sounds cool…might try and find some vids on people doing that technique. Very Happy
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Post Fri Jan 16, 2015 1:49 am 
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Valen
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you can buy the gas bottles outright too, rather than rent, for robot peeps like us it works out way cheaper in the long run.
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Post Fri Jan 16, 2015 10:55 am 
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Spockie-Tech
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This guys videos are pretty good.. he has a few on the technique, here are a couple of intros.
https://www.youtube.com/watch?v=CA3w9Wq5mh0

https://www.youtube.com/watch?v=0h5yw-qrl9c


TIG is much slower than Arc, its more like soldering, with the added complexity that you can melt holes in the part youre joining if you dont move along nicely.

and its *much more fussy about what its welding being spotlessly clean. You have to grind the weld areas until its shiny bright or it turns out horrible.. Stick/ARC just burns on through most rust and paint without a problem (probably due to the liquid shielding also acting as a flux (that turns into slag) vs TIG's Gas shielding that doesnt do anything flux-like to displace impurities, it just stops oxygen from getting to the weld while its red hot)

But, ARC just cant do precise fiddly work on thinner gauge stuff (unless you are a real expert and use ultra-thin electrodes.and even then you get just one chance, you cant easily go back over it like you can with TIG. ) so for some applications, its worth the hassle of learning TIG.

Its probably all sounding a bit complex, Dont want to put you off, Smile I just wanted to let you know if you find the Arc welding a bit umm. crude for fiddly stuff, that you do have an option for finer work.
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Post Fri Jan 16, 2015 11:40 am 
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Glen
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I've got the hose with valve from my old welder if you want it, pretty bulky so maybe if you're ever down this way you can grab it Razz

They're only about $80 from recollection brand new.
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Post Fri Jan 16, 2015 12:03 pm 
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miles&Jules
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just got a quote from a rental place in bris….its $350 for a half sized bottle full of argon then when I'm finished they swap it for $122 …whats that price like?
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Post Fri Jan 16, 2015 12:05 pm 
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Glen
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Its usually about $350-400 to buy the bottle outright and $90-130 to refill it. Otherwise it's about $150 a year rental and the same for a refill at most places. That's for an F size cylinder which lasts me about a year and a half. The smaller G ones will still last a long time and be cheaper again.
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Post Fri Jan 16, 2015 12:13 pm 
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miles&Jules
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So your bottle is bigger for the same price Very Happy
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Post Fri Jan 16, 2015 1:36 pm 
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Valen
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Perhaps the rentals have come down, last time we looked it was like $30 or $40 per month.
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Post Fri Jan 16, 2015 2:40 pm 
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