Old Newbie, with a question for the gurus.

[BruceK]

Evening all.
I appreciate I'm walking with the experts here and am all ears for advice and suggestions.
After years of making the tea, grinding off rusty surfaces, passing and holding stuff and watching welders at work I've decided to take the plunge myself. At last I'm going to learn how to weld properly. It'll mean buying a decent sized welder to replace my little one and taking it steady but, before I retire in 18 months time I'm going to do it.
For now, with a friend, I'm about to start building my workshop in readiness. It will house all my tools, woodwork and metal work and will shelter me from the elements while I'm working on all my retirement projects. The workshop will be a steel H frame 45ft x 25ft and I can't buy a standard size portal because the roof pitches are too low and I want to keep the eaves low and at the same time have space for an upstairs storage room.
My friend has been great, welding all sorts of stuff for me over the years. He's skilled and has a 230 amp Sealey (230 volt) mig welder but I can't keep relying on him for everything I want to do in the future.
We were going to weld some 10mm thick mild steel footplates onto some old 9" x 4" x 10mm RSJs but last night he tried a sample and kept tripping the RCD on his home electrics. He's worried he might damage his welder if we just upped the ante with cable/larger fuses.
This is where I need the advice please.
What's the best sort of welder for this type of job? We only have single phase power here so I guess we can't go much bigger than 230 amps. Might an inverter be a better idea than a mig and if so what sort of size would that need to be to weld 10mm plate?
Failing all that is there someone out there in the Leics/Northants region who alreadyhas all the kit and would be prepared to do the job for me at a reasonable cost? It would be for 8 footplates and another 8 plates on the ends of the cross members (102 x 230 x 23) to bolt onto the columns.
It won't be for some time yet, since planning permission takes at least 12 weeks and it has to be properly done, so there's plenty of time to weigh up all the alternatives.
Thanks for reading all this. Any/all advice would be gratefully received.

 

[jackjosh]

With 10mm you need a chamfered prep, buy a Portamig, it takes time for delivery but is hewn from solid stuff.

 

[anjum]

Might be worth investing in a second hand arc welder for that thickness. You can then sell it on afterwards.

 

[cumbriasteve]

Considering you are building a retirement 'playroom' I would also suggest an arc welder, it would be an item that you may find future use for and can be very cheap to purchase if you seek out one of the old oil filled Picarc, Oxford or Bantam sets.

This one would be ideal if you could arrange collection/delivery:

http://www.mig-welding.co.uk/forum/showthread.php?t=43590

Failing that it would have to be a cheap £50 buzzbox type that would do the job but will probably need to cool down after each footplate or as you mention an invertor, a bit of an expensive 'nice to own' if you have little future use.

The electrics tripping will continue to be a problem, an invertor will probably manage ok though.

I guess the new workshop will be having a dedicated uprated supply being considered.

 

[tombardier]

Hi Bruce,

In reply to your PM and the thread

I thought I'd list the pros and cons of my own inverter welder vs the oil cooled bantam that I happen to be selling, which cumbriasteve linked to cheers!

my inverter - an r-tech 140 dc arc welder - lovely to weld with, will cope with a bad power supply and will technically give you higher output with lower input (being more efficient) but - it wouldn't might not cope with the duty cycle needed at high amperage

the oil filled bantam 180 - your electric supply might not cope at higher settings (it'll probably trip when trying to strike the arc at the high settings), An AC transformer welder won't be as nice as welding with a DC output inverter but it will weld all day without complaint, at higher outputs too! (also, arc blow isn't a problem with an AC welder - if you have any magnetisation of your metals )

I'm almost convincing myself not to sell it here

Cheers. Tom.

 

[BruceK]

Evening Tom
Sorry not to have got back to you ~ been away! First weekend off since early May.
Unfortunately my pal is not so sure about the old oil-cooled welders; apparently the oil is really nasty & toxic/carcinogenic. I'm reliant on his welding skills so I guess I'll have to pass on this one.
On this occasion it looks like I might have to take all the bits to a local fabricator, who also, happily, has some half price steels lying around. My mate will weld all the cleats and lugs once the frame is complete.
Thanks to everyone for your helpful comments and suggestions. I will make learning to weld properly a top priority once I'm in my man-cave.

 

[tombardier]

Well yes, it's toxic stuff, but then again It's not like you need to come in to contact with it

I looked in to the price of an oil change on it actually, and it was going to cost £90 for the oil :O

 

[Rig Pig]

Shell Diala B is a non PCB oil so unless its been changed for somthing else it isn't to nasty

 

[tombardier]

Could it depends on the year. I've absolutely no idea how old mine is

 

[Jim Davey]

Choose your welder carefully, some are far more efficient tan others. More copper and more iron makes for a better more efficient transformer, sadly copper and steel are pricey commodities these days, add that to the fact that small to medium sized step switched migs are a sold in a hugely competitive market an it's no surprise manufacturers have to make certain sacrifices.
Pay particular attention to the current draw of the machine at maximum output, this will be the determining factor if power supply is restrictive. No point buying a 250 amp machine if your circuit breaker pops at 180 amps. Bang for buck your best bet is a stick set, there are plenty of machines out there that will happily push out between 140-160 amps while only drawing in 13-16 amps from the mains. This means you can comfortably run a 3.25mm rod continuously and 10mm plate is well within the realms of what is feasible.
Mig however is much easier to use but you need more power to get the same weld strength as a good stick weld would achieve at probably not much more than half the current.
Probably left you with more questions than answers but the different processes have various pros and cons so a machine that can do both is often attractive. Many modern inverter migs will do stick too, just make sure you ask the appropriate questions about mains requirements before you part with your hard earned pennies.