on the RPN mentioning sharp pc1211, v.albillo, el506w and recurring topics

12062017, 02:39 PM
Post: #42




RE: on the RPN mentioning sharp pc1211, v.albillo, el506w and recurring topics
(12042017 07:55 PM)franz.b Wrote: you made me think of an important detail: seeing partial results helps a lot in understanding what you are doing and prevents gross errors, as has already been said. This is crucial for engineers. If you do plain math, then there's probably no need. If you are just applying a formula you found in a book (like students do), there's no advantage, but if you are reasoning a problem as you compute it, there's no substitute. A rough example: Have a pressure, need to estimate a tributary area, or measure it from CAD. Just plug the numbers and get the force. Right on you think, uh! 50000 N, I'm going to need some serious steel to support this. Let's try with a 200 mm shape: compute a bending moment, so that force times L/4 if it's simply supported. DUP that in case I need it for a second try. Divide by the section modulus of the trial shape, and boom, too much stress. DROP to get my moment back, and try a slightly thicker shape, now I like it. Just write the selected shape on CAD and move on to the next problem. Somebody might think it's backwards: You can solve the problem in advance algebraically, and get a formula to extract the necessary section modulus, then select the shape from there. But that's how I think and works for me. It allows me to stop in the middle and change a design if I think "oh, there's no way I can have 50000 N here, I'll run beams the other way to send some of this force somewhere else, will be much more efficient". Without seeing those intermediate results, I don't "feel" the forces and can't visualize how things will behave. By the way, the above works so much better on an RPL machine than RPN. Because you get the best of both worlds: You can have algebraic formulas whenever you need them (use the right tool for each job), and you can save as many temporary results as your brain can handle. So the eternal wars of algebraic vs RPx are pointless, just use the tool that integrates best with your workflow. In my case, RPL it is. 

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