What is a good way to construct a ramp light and strong enough to hold a robot? 1678 had one that was obviously strong enough to withstand competition and I heard (can’t remember where) that it weighed somewhere on the order of 10 lbs. How would you design a ramp to have this kind of strength with this low mass?
A few thoughts on this:
- Define your requirement. How much flex are you willing to allow (both in angle and distance)? How much weight do you need to travel on the ramp? If you insist on <1mm deflection with the heaviest legal robot, your ramp will end up heavier.
- Limit your spans. The more vertical supports you provide, the less stiffness the actual ramp material requires. Vertical supports also have weight, of course! Unless you get fancy with them, cantilevered spans count about 4-8x as much as spans with support at both ends.
- For a ramp or other structure providing vertical support, provide lots of cross section of your stiffest material in vertical planes. As another example of this, note that chassis with rectangular tubing have the long axis oriented vertically. This is also convenient for mounting bearings and chain/belt in tube, but the real reason is that you need cross-section in the vertical planes. If you do square channel, orient it so that the two “flanges” are vertical to maximize stiffness in the direction you need it.
- Unless you have access to serious finite element modeling, or the time and budget to do extensive testing, don’t do aggressive lightening holes, especially in the vertical planes. If you do any lightening, don’t leave any sharp corners (use relatively large radii) because sharp corners and small radii are more likely to develop into cracks and ultimately failure of the ramp.
You need to design within the abilities of the manufacturing processes available to your team.
…and at the end of week 4, you also need to design within the time constraints, today.
Might be that your team’s time could be better spent on other aspects of the robot, such as improving the speed of moving game pieces, and driver practice? I’ve seen several games over the years where ramps were a way to score bonus points, and it seems that teams are wildly overoptimistic about how often other teams will be willing to try to use those ramps, and how often they will have a successful climb. We put ramps on our 2007 robot, and they were never used in two regionals.