Quote:
Originally Posted by jakeru
Now that's very counter-intuitive to me that on a perfectly symmetric looking object, that the lightening relief would be positioned off the line of symmetry. Any explanation as to why, Fred?
Also, I find it interesting that you've modeled a balancing apparatus. Wouldn't it be just as easy to assume the piece is sitting there in space and rotating by some strictly defined (assumed unmoveable) axis? I suppose with your method, you could model flexibility and oscillations of the testing jig, but I'm not sure why that would be useful, unless you were doing real-world testing on the same exact jig and wanted to somehow model very similar predicted results. At some point, the model needs to assume things are fixed. Would this simulation assume the base feet of the testing jig are fixed?
I remember getting some unversity mechanical engineering grad student to help do some FEA simulation work on designing a lightened version of wheel centers for an autocross race car I was running. This was at least 10 years ago, so the tools were a bit more rudimentary to what you seem to have access to. I don't remember using using any solvers, but rather, just manually iterated the design a few times until we were happy. The machined weight of those wheel center came out just as predicted! Very cool and memorable experience for me. So thanks for sharing your fascinating techniques.
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Thanks Jake
RE modern solvers; the owner and its backend software engineers claims that this is what puts on the
Mars Rover (Curiosity) where it is today and also what makes most of today’s jet planes takeoff and land safely. I’d love to challenge these statements but dare lolll
The jig’s base is indeed ‘fixed’ with 9806.65mm/sec2 gravity acting on it – not floating bud. The shaft/bushings also needs mu-static, dynamic and stiction velocity/deformation (aka friction) properly defined and enabled otherwise nothing works…. the shaft will bounce passed the 500rpm. Real-life no, I agree, but certainly real-world multiphysics (well, this world anyway).
RE Center caps, they are ‘visually’ symmetric yes but as you saw in the vid, the center (p badge) is not 100% aligned with the center of mass (taking gravity into account here). That is due to the non-symetric feature/pocket for the badge. Anyhow, it is very unlikely that a perfectly symmetric center cap (center of rot) are going to throw your wheel out of wack however best practices force me to ensure that the design is meeting ‘base line’ quality. I am sure that potential buyer will appreciate this.
OT; a year ago I’ve designed a special tool holder that had to mount into a 40,000RPM spindle. The tool was designed and meant at machining a part within 2micron tolerance using a carbide endmill of 0.2mm diameter – read very (very) small. It was for a medical device/part, something that brother in law here specialize into. Multiphysics balancing in this case greatly help i.e. less material had to be removed once the tool was dynamically balanced (real-life) afterward. We’ve seen ‘dust’ amount of material removal to get it balanced in the 4DOF. That said it does serve a purpose, in some more extreme cases, but perhaps not so much for center caps that only spin <3k rpm lollll
All good fun bud!