LSPSCAT & Bert2:
I am not suggesting you should not ask here, but I’m saying that it is a sad state of affairs if this is the only place you can go with all your questions and for your guidance. The “face-to-face, meaningful, engineering discussions” and interactions, as you put it, can be very rewarding for both partes in the exchange. And, I am sorry for you fellows and gals if you have not had this experience and type of guidance. Us older fellows and you younger guys have a lot to offer each other, and these forums are one means to do that, but in many respects they are a poor substitute for that more intimate interaction with someone you trust and respect. There aren’t many, real, dumb questions, but you have to have studied the problem deeply enough so as not to ask a dumb question in a dumb way. You should not feel dumb or embarrassed for not knowing the answer to a problem you have never seen before and your advisor has faced a hundred times. But, you should know enough to know how to frame the problem and your questions in a meaningful way so you don’t look silly. If this does happen on occasion, we have a quick exchange (a laugh) and move on, because we’ve come to understand each other. Of course, your own self study is important, it’s part of the game if you care about your profession, we have all had to do that along the way. Certainly the fact that you spend weekends researching and analyzing work problems speaks highly of your interest in bettering yourself and your care for your profession.
Your post and experience are certainly frustrating and disappointing, really a sad commentary if it is universally true. Maybe some companies with an established product line may not be doing much new design and engineering, just doing the same-old, same-old, as long as it continues to sell. Riggers and contractors don’t do real much complicated design and analysis, but have a wealth of experience if they’ve been in the business very long. Maybe some of these people have become bit complacent, from the engineering standpoint, because their particular business relies so heavily on experience and then some seat-of-the-pants engineering. Furthermore, the liability belongs to the company, so they may care a bit less. Maybe the fact that they trusted you to do the right engineering calcs. should be taken as a feather-in-your-cap.
In my office we do engineering for these types of clients and it’s my _it in the wringer if we do something wrong, so we try to do real thorough engineering. Check your calcs., you bet I would on the first few jobs with each different building material, or when I knew you were facing a situation new to you. Then, I would come to trust your judgement, and know that you weren’t bashful about asking when you weren’t sure. If you brought me an 18" WF, when my more experienced gut told me it should be a 24" WF, I’d tell you to go back and look at it again, without a bunch of calcs. on my part. And, at first you’d be amazed, just as I was, how did he know that, and why didn’t I see that? I have had mostly good experiences on both side of the mentoring relationship, but a few bummers too.
Look to professional associations, and join a few; ASCE, ASME come to mind. Look to materials or product specific organizations or associations and their literature, AISC, ACI, ASM, AWS for example. Your company might even pay for some of these. Most of the more experienced people at any of these places are more than willing to share their knowledge and experience. Look to engineers who work for companies other than your own if there is such a dearth of knowledge and experience within your own company. Talk to your old college profs. for help or for ideas of people in your area who might work with and help you. It costs you lunch and a beer once in a while, and may even lead to a more meaningful job, because you’re showing more interest and initiative than most. Maybe you should look for a job with a consulting engineering, structural engineering, office if you want design work. Most of the senior people there are kinda forced to stay current and relevant if they want to continue to practice.
As for FEA, there’s not much doubt that I can’t keep up with you, in fact that’s where I come to you for the same kind of help I have given you in other areas, in fact that’s why I hired you. I actually taught a couple courses in computer applications in structural engineering in about 1966-68, we punched our own cards and carried them over to the main frame computers. I even have several FEA text books from that era. But, I’ve also never had a building fail because I used a slide rule to do the design at that point in time. I know what I want modeled, I may have a better feel for structures at this stage in our development than you do, and can probably give you some ideas on that account. I can tell you where I think we want a tighter mesh, etc., but you know far better than I do, how to actually do it. I just can’t kept up, because I don’t use it often enough, so I’m not nearly as proficient as I assume your are. In that respect, I may be “your manager in over his head.” Just as I should be patient with you, you should be with me, and this is possible if there is a good mentoring exchange going on.
My original post was in the ‘interest of safety’ but also because I didn’t think you asked the right question or were being offered the right answers. And, in good part, that was your fault. I didn’t mean to hurt your feelings, but I most certainly did mean to get your attention and make you think a bit more. The sketch you provided would lead many engineers to assume you were talking about some serious, real world, engineering. If you intended what you now are suggesting, just a simple question about rigid body rollover, your sketch should have looked like desertfox’s sketch with his 26FEB, 5:12 post, not the one you provided; or your question should have clarified that your actual sketch was to be used for dimensions only, and that all else about it was to be assumed to be one big rigid body, with infinitely strong tires. Otherwise, how would we be expected to know that. Then, if you study desertfox’s sketch and calcs. for a minute and see that the weight cancels out of the equation, and if your sketch is to scale, you might come to the conclusion that you could get your angle approximation by drawing the resultant through the C.G. and your tipping point (desertfox assumed the edge of the lowest tire) and measure the angle right on the drawing. 5144 vertical, 2580 lateral, what’s the angle? But, that is not the answer to the real world problem that your sketch shows. Desertfox says “trailers are connected rigidly” and “26.5 degrees to the point of no return.” And, there is a whole bunch of real serious engineering and a trailer operating manual to explain those two statements and where the load resultant can actually fall on the trailer deck.
