Quote:
Originally Posted by GeeTwo
Yesterday evening, I verified that the mangled shaft is steel; a magnet sticks to it. I can't see using aluminum of any grade in this capacity. The shaft in question was not used in the drive system; it was used to swing a "hammer" that "kicked" the yoga ball. Despite always supporting the other side of the hammer, somewhere along the way, the shaft deformed, most particularly near the key slot. Curiously, checking the hammer, there is less deformation of the aluminum hub than of the steel shaft.
|
This isn't a reasonable argument against using aluminum shafts at all. There are tons of different ways that a motor driven "hammer" could load a shaft improperly such that any material would bend. For example, shock loading a long, 1/2" keyed shaft could potentially bend any material. You're putting a ton of force on that tiny area of the keyway. I also suspect the shaft was loaded improperly in some other way, but without details on your setup I can't really comment. But this isn't necessarily a part of your robot with less stress on it than the drivetrain.
This just further reinforces Cory's point - you shouldn't use material to compensate for a bad design decision, because the difference in strength is somewhat marginal anyway and you can still screw it up. 7000 series aluminium shafting isn't really that difficult to use, and instead of steering away from a common sense way to save at least 5 pounds per robot (once you add up all the gears, shafts, etc), you should steer away from bad design decisions that load shafts poorly. I guess if you're still convinced, I'll enjoy having 5 more pounds of mechanism than you do, or 5 pounds less mass to accelerate.