I have a cattle truck with 5mm chequer plate floor that needs replacing. It is welded, underneath, to rhs cross members. I'ld like to blow those welds off without removing the tray, if possible, but access is very tight in spots. Never used a plasma before, but thinking it might be an option. Doesn't matter if we make a mess of the floor, it is rooted anyway. Thoughts?
Have you considered using a Arc Air/Carbon Arc?
1/16" cutoff wheels on a small angle grinder, only near painless way to go to zip those welds apart. Air arc or torch for the ones you can't get to. I doubt plasma would be the tool of choice for this kind of job, I could be wrong.
Just curious if laying a new floor over the old one would be a option?
The welds in the photo are about the only ones I could get to with a grinder. I have a 250 amp welder and 20 cfm air.. Is this enough to run an air arc torch? I assume there are different size carbons depending on the job at hand. Not looking forward to using an oxy torch under there. I have a mate who welded new sheeting over the old but it wasn't a real success. Moisture etc. between the two made everything rust out in a few years. The truck in the photos is 14 years old now, so it hasn't lasted too badly.
250 DC is pretty marginal, but then your welds are small, might do.
Do it all the time 'cause I'm limited to 250 amps....use the 1/4" electrodes. Drawback is the electrode is fragile on that big klunky air arc holder, and tends to get snapped off when getting in and out of the area.
I would suggest roughly cutting out square holes from the top with the oxy, then you will have good access to get to the welds with a grinder and slitting disc.
an air arc is a lot more messy than a torch it blows sparks in every direction
You beat me to it Cmark. :drinkup 20 CFM of air is borderline insufficient for running an air arc rod. Yes, it can be done, but with air arc, more air is better than not enough air. Insufficient CFM with an air arc will cause the steel to carburize, only a grinder will remove the weld then.
I'll probably use a combination of all the methods mentioned above. I'am keen to experiment with the air arc, relatively inexpensive to set up. Just remembered...I have two 20 cfm compressors, one mains powered and one engine driven, if I plumbed them together I would have 40cfm, would I not?
Providing both compressors unload at the same pressure, there shouldn't be a problem running them in parallel. As far as the cost goes, carbons are cheap enough, but an air arc torch is going to cost a few hundred dollars. I don't want to discourage you from getting one, it's a great tool in the right application but if you jump straight in and try to gouge those welds from underneath that truck, I predict that you will quickly develop deafness, burns, a bad temper and holes in your RHS.
Gotcha Cmark, I'll go in with eyes wide open. I have seen them in action before so am aware of the fearsome noise/mess they make. Just another tool I would like to try to master....Could save me a 250 km round trip to town one day if I had a desparate need for one.
Wouldn't be my favourite job using an arc air under there. You would need to have the full leather suit. There will be molten metal bouncing off everything. Have fu .
can you take it off the truck and lay it on it's side it would be faster and a lot easier and cheaper because before you get done you will be fixing melted and burnt air lines and wires on the truck it would be much easier and faster to weld the new one back in .
Yes that is true...but a oxy torch is harder to peal off a weld, and I'm not going to stuff a $800 plasma torch in a corner and have it destroyed.
Earplugs and a welding jacket is unobtainable down there ? The air requirements can be lowered by not turning the blast on full. In a pinch, I have used a standard electrode holder, a standard welding electrode (had some rusty 6011 laying around ) and carefully aimed a blow gun to get the job done.
Great idea. Simple is always best.
I do a lot of metal fab including repairs such as this. All tools mentioned above are at my disposal. Removing the bed would be very helpful. On thin material like that with a sacrificial plate, I'd grab a plasma with the proper tip mostly because of controllability. Thin material like you have there is a tricky way to learn how to run an air arc. I hate cut-off wheels. Slow and messy. my $0.02
You could also use a gouging tip on a torch. I would do like has been said cut squares in the floor to access it and then if you would measure over you could cut with plasma right next to support and maybe right thru the weld. I had a coworker that was really efficient with air arc but I havnt caught on to the tricks of it very well.
We run a handful of cattle trailers.. not trucks....and have to do repairs like this on occassion. That being said, I second Twisted's reply. I like the precision of the plasma cutter.
Not the right way to do it but if you're in a hurry or really lazy, you could skin over it with 3/16 plate. Adds about 7 1/2 lbs per square foot.
a plasma does have a gouge attachment. works the same like air arc but the rust on that trailer might make that job unpleasant