- Thread starter f4hart
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out door man
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Various people have given flow rates of between 10 and 20 ltrs / min for CO2. The instructor on my evening class said " 4 ltrs is enough". The instructions for my Sealey Mightmig 120 XT state 2 - 4 ltrs. Can someone out there HELP a poor Junior. Being a Yorkshire man I have tried 2 ltrs and it seems to work fine with 4 ltrs making no obvious differance to the weld.
Masked Marauder
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My advice is to try without gas. Then turn the gas up as far as it will go. Now compare the two and work your gas so your getting welds like the one you made with the flow fully up, but with the flow actually as low as you can get it to make the welds good.
I wouldn't recommended turning the gas fully up, as this would be as bad as no gas at all, destroying any shrouding effect. Set it at around 12Lpm & then wind it down as low as you can get away with, whilst still maintaining a nice smooth weld.
weldequip
weldequip
malcolm
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What are your feelings on nitrogen embrittlement. It's easy to tell when you have too much oxygen (the weld bubbles and spits), but TechnicAl's mention of smaller precentages of Nitrogen causing problems had me a bit worried about reducing gas flow rate too much.
Masked Marauder
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That is the maximum flow on my (CO2) regulator, I should have been more specific!
I jumped the gun a bit there Malcolm. I was thinking more of the average DIY'ers non critical welding tasks & needs for economy. In pratice, if it's not a structural weld you can get away with a lower gas output than recommended figures. It's always better to stick to recommended figures of course, as the boffins have spent vast amounts of time & resources coming up with those figures for a good reason.
weldequip
The maximum flow on your regulator could be up to 30 or 40LPM which is way too high for common DIY welding tasks.
weldequip
malcolm
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I guess the majority of DIY welders won't have flow gauges at all. Probably a good thing to turn the gas down until you don't see any problems and then turn it up a bit again. It's good to be aware of potential issues, but I'm still trying to get my head around the Nitrogen one (specifically how to tell).
In practice I've never had a weld fail in service, and I've only recently bought the twin gauge reg, so it's not some furry green monster that pops out in the night with a crowbar to break nice looking welds, just another thing together with good technique and joint design that will help reduce chances of fatigue.
Not that my own technique or joint design are any good - I just avoid welding really risky stuff altogether. If I welded a driveshaft together I'm sure it would break, but it's metal all the way along, and I'm sure there are welders here who would make it work. Chassis and suspension I'm happy with, but suspension only after some thought and calcs that prove there is no real load to worry about.
In practice I've never had a weld fail in service, and I've only recently bought the twin gauge reg, so it's not some furry green monster that pops out in the night with a crowbar to break nice looking welds, just another thing together with good technique and joint design that will help reduce chances of fatigue.
Not that my own technique or joint design are any good - I just avoid welding really risky stuff altogether. If I welded a driveshaft together I'm sure it would break, but it's metal all the way along, and I'm sure there are welders here who would make it work. Chassis and suspension I'm happy with, but suspension only after some thought and calcs that prove there is no real load to worry about.
Remember the tragic death of F1 driver Ayrton Senna? The inquest concluded that the cause of the accident was a failed weld on his steering wheel shaft; it had had a shortening modification done. Wouldn't have liked to be the welder responsible for that job!
weldequip
malcolm
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You can imagine the situation the poor welder was placed under. I guess he made the wrong decision, and the guy that asked him to do the job did as well. Should imagine both were under a lot of pressure at the time so the mistake made it through.
Believe it or not my first real job was steering column designer! Everything was belt and braces. The joints to be welded were triangle shaped tube overlapping over triangular bar. If the weld failed there would still be the mechanical location, and hopefully a little rattling to suggest to the driver something was wrong, so that maybe he might ask the dealer to fly over a mechanic. (I was working for Rolls Royce at the time).
It's well worth thinking about what would happen if a weld breaks. For a floorpan probably an edge would come off and wet feet would finally annoy you into fixing it. A single weld failing in most suspension systems would hopefully cause a knocking noise and weird stseering. Broken driveshaft most likely the car stops (unless it wraps itself around the handbrake cable in which case certain death). Steering column - that's one of the things you wouldn't catch me welding.
Believe it or not my first real job was steering column designer! Everything was belt and braces. The joints to be welded were triangle shaped tube overlapping over triangular bar. If the weld failed there would still be the mechanical location, and hopefully a little rattling to suggest to the driver something was wrong, so that maybe he might ask the dealer to fly over a mechanic. (I was working for Rolls Royce at the time).
It's well worth thinking about what would happen if a weld breaks. For a floorpan probably an edge would come off and wet feet would finally annoy you into fixing it. A single weld failing in most suspension systems would hopefully cause a knocking noise and weird stseering. Broken driveshaft most likely the car stops (unless it wraps itself around the handbrake cable in which case certain death). Steering column - that's one of the things you wouldn't catch me welding.
The point was Malcolm that F1 is at the forefront & no doubt welders employed by F1 teams are amongst the best around, using the best equipment & even they can get it wrong!
I supply a company with gear that sub contract to Rolls Royce Aerospace - a smashing company & experts in their field. If you looked at their workshop however, you would think they were almost a back street garage!
Every time I sit on a plane looking out the window at an RR engine I think "part of that was made at X, down the road from me, and they probably still have an outside loo"!!
weldequip
I supply a company with gear that sub contract to Rolls Royce Aerospace - a smashing company & experts in their field. If you looked at their workshop however, you would think they were almost a back street garage!
Every time I sit on a plane looking out the window at an RR engine I think "part of that was made at X, down the road from me, and they probably still have an outside loo"!!
weldequip
I watched a program on tv a while back that concluded Senna's tyres had cooled behind the safety car, sufficiently to lower the ground clearance so that the bottom of his car grounded and took him off the track. Well, I dunno, but it'd make the welder responsible feel a little better.
Really. Havn't seen that one. If you watch the video replay you will see him just shoot straight without any control, which would back up the steering theory. But who knows? I'm a great conspiracy theorist & never really believe what we are told on TV/Newspapers. Consider this, if you were part of the elite club of world leaders & could manipulate TV ( Blair Broadcasting Corperation!) you could tell everybody whatever you wanted and they would 'believe' it! Sheep follow sheep etc.etc.
Read something last year that claims they had a cure for cancer in the 50's! but it was covered up - treating a problem is far more profitable than curing it!
weldequip
Read something last year that claims they had a cure for cancer in the 50's! but it was covered up - treating a problem is far more profitable than curing it!
weldequip
mikeknowle
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floor pan coming off
Good point Malcolm. Can I ask a general question? I was welding in my first floorpan today and was being a good boy by using seam welds on both sides as I don't want my ass sliding down the road. If the weld failed in part (most likely due to my over-grinding) on a floorpan (say the panels came apart for say 3cm) would this be an MOT failure as long as it wasn't within thre suspension zone. Pardon my ignorance.......I'm trying to produce the best I can to my ability, so am probably going a bit over the top......does it really take 2 months to weld a floorpan in!!!
Best Rgds to all....
Good point Malcolm. Can I ask a general question? I was welding in my first floorpan today and was being a good boy by using seam welds on both sides as I don't want my ass sliding down the road. If the weld failed in part (most likely due to my over-grinding) on a floorpan (say the panels came apart for say 3cm) would this be an MOT failure as long as it wasn't within thre suspension zone. Pardon my ignorance.......I'm trying to produce the best I can to my ability, so am probably going a bit over the top......does it really take 2 months to weld a floorpan in!!!
Best Rgds to all....
malcolm
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I believe a broken weld would fail an MOT if the tester saw it. Certainly it should fail the MOT. Should be careful with the grinding as it would be a real pain to weld steel when it's been ground thinner. I tend to just grind the welds if I'm grinding anything.
