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Originally Posted by NextPerception
I've actually modeled up the whole motor gearbox and did some FEA analysis of it in solidworks cosmos. I had to gues what alloy of aluminium the ring gear was but other than that it is dead on accurate. I came to the conclusion that it wasn't strong enough because there is a gear carrying plate that binds and rubs with the other stage of the gearbox ( i think this is why they stopped selling the 3 stage versions of this gearbox) that eventually tears itself apart. The FEA analysis indicated this problem and so I opened up one of the motors that had some running time under its belt and low and behold, stress fractures and deformation already starting at one end of the plate. I slow the process down with a pillow block supporting the opposite side of the shaft but it is still like a ticking time bomb. To tell you the truth, I wouldn't expect anything better at the price they are sold at.
Unfortunatley, Knowing what the problem is only half the battle. I don't have the capabilities to machine a gearbox inhouse or the funds to outsource it and so I am stuck finding an off the shelf part that fits my needs.
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In the combat robot community people have found *some* rather decent drills with gearboxes that are pretty robust; finding one that fits in 1.25" may be an issue, but you have to loosen up your criteria.
I wonder if 7 stories are really necessary, my now dissembled 12 could take a 3 story drop and hits from dead blow hammer to all but the top and bottom.... but I'm not sure it could survive a 7 story drop. If you run the numbers on it, a 7 story drop is a lot of energy, significantly moreso than a 2-3 story, and what kind of forces you would see I imagine (Although, you should probably compare the amount of Kinetic Energy some of the more powerful spinners can unleash to this).
I also imagine that in a drop test such as that, if the gearbox shafts are well supported, it is unlikely the drop that is killing the gearboxes, it is probably something else. Also, the banebots gearboxes really do require shaft support on the other side, but on top of that the shaft support must both be rigid and aligned. If it isn't aligned nicely, it cause premature failure, and if it isn't rigid enough it could allow forces to misalign the shaft and also cause premature failure. What may be potentially good news is banebots is redesigning the gearboxes to be stronger and more robust; Not sure if they'll be available within your time limit.