Dave Richards
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- 2,930
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- SE Minnesota
This is barely woodworking so bare with me.
I'm volunteering with the local First Robotics team this year. It's a pretty cool thing and I'd recommend it to anyone. The game this year which is sponsored by Star Wars: Force for Change includes a requirement for the robots to reach up and hook onto a trapeze bar and then pull themselves up off the floor. One of the students designed a hook to be made out of thin sheet metal. The robot would have four of them in two pairs. We've really had a problem with the robot being overweight (Max is 125 lbs and our target is 120 lbs.) and have been looking for ways to cut down on the weight. I was curious about the possibility of making the hooks out of something lighter. The hook he designed, which has the same profile as the one in the photo, weighs almost 5-1/2 ounces so more than a pound for all four of them. I modeled his hook in SketchUp to get the volume andcalculated the weight of a 12mm Baltic birch plywood hook at 1.48 ounces. I made one with the exact same dimensions as the student's metal hook. We could get by with only two of them instead of the four they were planning.
We tested this hook to destruction. A couple of the other mentors, each of whom tip the scales at over 200 lbs. took turns hanging from it. It broke after the fifth or sixth loading. The failure occurred where the plywood is 1/2 in. wide. Overall dimensions are 2-1/2 by 6 inches.
I'm not sure if plywood hooks will get used on the robot. Two of them would certainly be more than strong enough and minor changes to the design could improve the strength but this makes me think that I often over build things in my own shop. I imagine I could get away with considerably less than I usually end up using.
I'm volunteering with the local First Robotics team this year. It's a pretty cool thing and I'd recommend it to anyone. The game this year which is sponsored by Star Wars: Force for Change includes a requirement for the robots to reach up and hook onto a trapeze bar and then pull themselves up off the floor. One of the students designed a hook to be made out of thin sheet metal. The robot would have four of them in two pairs. We've really had a problem with the robot being overweight (Max is 125 lbs and our target is 120 lbs.) and have been looking for ways to cut down on the weight. I was curious about the possibility of making the hooks out of something lighter. The hook he designed, which has the same profile as the one in the photo, weighs almost 5-1/2 ounces so more than a pound for all four of them. I modeled his hook in SketchUp to get the volume andcalculated the weight of a 12mm Baltic birch plywood hook at 1.48 ounces. I made one with the exact same dimensions as the student's metal hook. We could get by with only two of them instead of the four they were planning.
We tested this hook to destruction. A couple of the other mentors, each of whom tip the scales at over 200 lbs. took turns hanging from it. It broke after the fifth or sixth loading. The failure occurred where the plywood is 1/2 in. wide. Overall dimensions are 2-1/2 by 6 inches.
I'm not sure if plywood hooks will get used on the robot. Two of them would certainly be more than strong enough and minor changes to the design could improve the strength but this makes me think that I often over build things in my own shop. I imagine I could get away with considerably less than I usually end up using.