[robotguy67]

I was the mentor that helped with the welding of the frame last year. Chromoly can be built very light if done properly. That's why it's commonly used in race car chassis, high stress points in air frames, etc... Given our design goal (killer lift bot), a fully monocoque frame was not appropriate last year. The tube frame could be designed much faster than it would have taken to do it fully monocoque. Aluminum tubing could have been used, but we didn't have the capability to weld it in-house and I'm not sure it would have ended up much, if any, lighter keeping the same strength. The total weight of the tube structure was #25, I believe - and this included the 8 big rollers, 16 bearings and 16 pillow blocks for the main lift. In all but a few small tubes, the wall thickness was only 0.035". This kept the weight down and all the tube triangulation made the entire frame and lift very stiff. The main tubes of the center tower are 1" OD. All the other tubes are either 5/8" OD or 3/8" OD. At one time there was a video on youtube of our bot lifting a 300lb guy on one wing without any showing any flex. As the primary designer of the tube structure I would definately use chromoly again if apprpriate for the application.

Mike