welding tractor for bridge - 2 lines railway span

Hi all
Need advice "from zero upwards" about using welding tractors.
We have a bridge to make. Overbridge over a railway. Two lines.
Structurally it's typical steel bridge type - sides / "parapets" form two main load-bearing beams, with connecting floor forming an overall "channel" structure. With the road traffic flowing "through" / largely within the structure.
Lots of fillet welds - but some butt, for seaming plates together.
Wish is to use welding tractor to highly mechanise the weld. Avoid stop/starts, promote extreme consistency of the weld runs, etc. All things to send the fatigue endurance way up.
Don't know what questions to start to ask...
Where do I start? What do we develop? Then moving into production - what's the real deal? Etc.
Rich Smith
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https://www.lincolnelectric.com/en-us/equipment/robotic-automation/Pages/automated-solutions.aspx
I've watched their automatic equipment welding hull plating in a shipyard.
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Hi Jim
Thanks and did enjoy looking at the Lincoln stuff.
That page shows robotic equipment. We are way way down the scale. Web-search shows things like the "Esab Miggytrac B501". Explanation - would never be weaving. Set Amps and Volts and get your fillet in a straight run. So never need the facilities of a good spec. subarc / SAW tractor.
Any thoughts, advice and experience on learning to apply simple basic equipment to mechanise welding? Very open-ended question...
I can set a solid-wire GMAW / MIG with argomix shield to give say 8mm fillet in the 2F/PB (horizontal-vertical) for a manual weld, no problem.
I'm visualising the challenges of converting that into making metres of unbroken smooth fillet for high-fatigue-resistance bridge structure.
Regards, Rich S
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Sorry, my personal experience is building small prototypes by hand, and the local expert welders who taught me weld bridges and nuclear piping manually.
https://www.gullco.com/shipbuilding-automation-aircraft-carrier.html
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On 8/29/2018 4:49 PM, Richard Smith wrote:

Anybody else find it kinda' scary that somebody who is going to be building a _bridge_ is asking that question?
I mean that if I was going to have somebody build me a bridge with a welding tractor, I would expect that he have extensive experience with such a tractor; such experience then be applied to the bridge building.
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The lowest "qualified" bidder gets the job.
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No they don't.
They know the person is both highly qualified and significantly experienced including with bridges - and are made further confident that this person has a confident character and is completely at-ease reaching-out to benefit to the limit of contemporary knowledge from those he respects.
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Come on people. So some of you style yourselves as so knowing and totally up there and so able to look in judgement. Show me there's some basis to that.
Right - we have an "Esab Miggytrac" and we've got an 8mm (5/16th-inch) fillet in the 2F/PB/hori-vert position manually - nicely flowed-in and wetted-in at the edges, etc. Conditions checked by macro-etch, break, etc - all excellent by a wide margin. We put the torch in the tractor. Hints on set-up? Find same angles as manual? Setting the guide-wheels (angle-in a bit, for instance?) Things to look out for? What differs from manual?
Yes I have some experience, but I'm looking to this vast experience you intimate you have...
Regards, Rich Smith
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On Sun, 02 Sep 2018 10:25:07 +0100, Richard Smith wrote:

Posting as a retired old geezer with some decades ago experience with semi-automated welding of different sorts (TIG), things to consider:
Your starting point should definitely be to attempt to duplicate your known good manual weld process as closely as possible.
Next run a series of tests to determine your "process window" on key parameters such as tractor speed, voltage, torch angle, - find the limits on travel speeds (high and low) which produce a satisfactory weld on each of several voltage settings around normal for a manual weld, possibly varying torch angle also.
(You should be able to find the process window for the guide wheel settings before doing any welding.)
Now you can take a conservative approach and run in the middle of the acceptable process window for maximum tolerance to errors, or you can decide to push the fast (economical) end of the window within some reasonable margin of the limits. Typically a mechanized welding process can be pushed faster than manual because the machine is steadier than the hand.
You may run into issues with poor fit-up requiring manual adjustments to accommodate varying groove widths, etc. (Min/max groove width could be part of your process window testing.) You will still need constant monitoring by someone who knows how to do the weld manually and can identify and fix problems as they occur, but this level of automation can definitely up production rates and reduce defects.
Glen
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Much appreciated. Thanks for benefitting me with this concentrated summary of your experience. Rich S
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Hi Glen
That job ended before it even started - I never saw the railway bridge.
I will treasure the advice you gave - because that is what it is worth for sure - and will be ready in the next job where I have long weld-runs and / or requirement to use a "tractor".
Best wishes, Rich Smith
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On Friday, August 31, 2018 at 4:23:21 PM UTC-4, Richard Smith wrote:

Agreed. I am very skilled at what I do, and I often find myself being asked to consult on projects which include elements outside my field(s) of exper tise. If I were less secure in my knowledge and experience, I might be afra id to ask what could sound like very basic questions, and have to pass on o therwise good work opportunities.
For instance, remember a couple of years ago when I was asking (here) some pretty rudimentary refrigeration questions? That system is now running bett er than it has in the 30+ years for which I have logbooks. I am now consult ed by others in the field as an expert.
You don't learn everything in a classroom.
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Yes, most definitely. Totally in agreement with you. There is a type of person who has the ability to make things happen. Rich Smith
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