I am looking for a skilled welder to weld a handful of high-stress points on a P-51 Mustang cockpit mockup I am building. Any suggestions?
@brsims and @HankCowdog—John K. suggested I reach out to you.
@malcolmputer—I recall you saying that your dad was a highly skilled welder.
Also, I don’t know what to look for in a welder. Do I need to find someone with expertise in a specific kind of weld, or just someone who is AWS-certified, or something else?
Ideally, someone AWS certified on the joints you want welded (joints are the mechanical fitment type, so like 2F or 6G etc) and on the type of material you are wanting to have welded.
I can ask him, but he’s not insured so I’m not sure how interested he’ll be since there are humans that could be hurt if it fails.
As a note on your design, instead of having the notched tube as a direct orthogonal for the pivot point, maybe notch the top of the tube and have it rest with some mean on each side. A bad weld at least still has the weight on the meat of the pipe rather than over the air. Would mitigate at least one of the failure modes.
Thanks for the advice!
OK, I’ll try to find someone who is insured first.
Thanks for the suggestion, Jim. I will explore a couple of alternative ways to do the pivot point so that less stress is applied to the weld.
Or a hot glue gun had an accident?
This is the sort of project where the welder might want callouts for weld process, fillet size and other details, so that if it fails, an expert witness can review and determine if the requested welds were adequate to do the job, but not properly done, or if it was a design flaw.
We discussed this in the committee meeting, Jim gave permission for it to stay providing he give us rights to show it off in the tours as well as give us some promo footage.
If this is for a simulator you might want to have an engineer check the design to make sure that it can handle it’s own weight, the weight of someone in it, and the stress of it moving. Because if people are going to be using it besides you then you would want an engineer to sign off on it being safe for other to use.
From there you are going to need blueprints to show the welder what needs to be done. Looking at this I don’t know what exactly needs to be welded, if it needs to be MIG or TIG, fillet or full pen. This is something the engineer will be doing because they will calculate the stress loads this will have. After it gets welded you will want a certified welding inspector check the welds to make sure they will hold up.
Short-term, I am not building a simulator; my only reason for building this is to use it for a few screen tests followed by a 1-day shoot with 1 person in it. It will tilt about 30 degrees forward and back, and maybe 30 or 40 degrees side-to-side to give the appearance of a P-51 Mustang in flight. Rotation will be done by hand.
Refining the design for the support structure has taken more time than I thought it would. For the past few days, I have been running FEM analysis on the design and iterating on a couple of different approaches for attaching the cockpit to the gimbal, which is where the most significant stress concentrations will be. These simulations are imperfect and completely ignore the quality of the welds, but after a couple of days, I was able to attain a minimum safety factor of 2–3 (with around 99% of the design at 8+) and get 1–2 mm maximum displacement while the cockpit is tilted 30 degrees forward. The structurally important side cross braces were excluded from the simulation as a rough compensation for the unrealistic metal joints.
That said, there are a handful of joints I want to be absolutely sure are done properly, and I know I’m not the person to do them. It would also be nice to leave open the possibility of making this into a simulator at some point in the future. Do you have any recommendations for welding inspectors or engineers?
I’m curious what you’re using to do this.
Inventor and, I think, Fusion 360 have FEM built in.
I don’t know anyone up in the DFW area that could help in the engineering/inspection area.
Since it sounds like this is being built for one-time use then the safety issue become less or an issue. This is due to the welds not getting stressed over a long period of time. They need to hold for a few days at most, not for a few years; all the movement is being done by hand and not by motors. They still need to be done well but you only have to worry about one or two people using it and not a large number of people.
