Never Do This, and Other Good Ideas Gone Bad

[114Klaatu0x72]

During Overdrive, our team decided on using a pivoting arm with one or two 80lb constant force springs, along with an underpowered gearbox, Chinese cast iron gears and "pwm cables" aka painted string, and a broken anti-back drive mechanism. It worked about once, and then the gears sheared off half their teeth, the anti-back drive pins fell out, and a cim burnt out in the manor of seconds. We switched out all of the motors with pneumatics between two competitions, and some of our problems went away. Later that year it knocked me out twice from a blows to the head, one time during a presentation to a middle school, as well as being just terrifying to be around in general. All of those problems pretty much stemmed from a few simple issues: a lack of prototyping, a love of cheap parts, and miscalculations in math. If we spent another week prototyping and a few hundred more dollars, and double-triple-well-beyond-the-point-of-redundancy checked our math, we could have done great that year. So, pretty much anytime you think something will work, despite how sure you are of it, try it and make sure it works.
Also, large amounts of force absolutely suck to work with, try to avoid designs that use them, as they tend to fail in some way after a sometimes very short while.