Melon Felon was taken out today for a good workout. This was actually the first time that we ever fired with the full designed counterweight of 300 pounds, since the last time we had something heavy to launch was last Spring, when we had 6 Olympic weights, which take up more room than the standards. But we got 6 more standards back in March, bringing our total up to 12 plates, each weighing 25 pounds, for a total counterweight of 300 pounds. We also got a 4 pound medicine ball to launch with, as the Melon Felon was initially designed to launch watermelons weighing between 3 and 5 pounds.
We started off with only 150 pounds of counterweight, just to see what kind of performance we would get. This meant that we were firing with a very low 37.5:1 weight ratio, so limited range was anticipated. Actually, our first shot went almost as far as our best from the RIT Watermelon Launch from the year before, landing 80 feet away. Not too bad for such a low ratio, and the release was way before the arm was able to stall in the optimal vertical position, so more power was available as well. We took another shot after adjusting the release pin, though the sling length was the real problem here. The distance worked out to be roughly the same as the first shot.
We then added another 2 weights, giving us a total of 200 pounds of counterweight, and the distance jumped over 30% to 110 feet! We had finally broken 100 feet with a heavy projectile, and video analysis showed that the release point was still off. Good trajectory, but we were still releasing before arm stall. It was decided that a longer sling was needed to get release to occur at the optimal arm stall point. So, we went from a 5 foot sling to a 6 footer, and launched again. We had a misfire due to a hole opening up in our sling, so we fixed it and launched again. The next 3 shots were all with the 200 pound counterweight and 6 foot sling, with various adjustments to the release pin to control the trajectory. However, all 3 shots attained roughly the same distance, approximately 80 feet. Later analysis of the video footage revealed that the arm was stalling pretty close to the vertical position now, but the sling was too long to catch up and was way behind, completely messing up our potential for greater distances.
For some reason, we reduced counterweight to 125 pounds and fired with the same 6 foot sling. Distance was 50 feet, and release occurred as the arm was moving backwards. The next shot was done back at 200 pounds of counterweight, but with an even longer sling for some reason. Due to changing a couple of things, the release pin was not set nearly steep enough, and so a backwards shot resulted. Cranking up the pin angle resulted in a 65 foot shot. Taking the sling down to 6' 8" yielded pretty much the same distance.
With the day getting late, we decided to move up to the full 300 pound counterweight for the first time ever and see what would happen. With the 6' 8" sling length we got another 65 foot shot, but shortening to 6' got us to shots in the 80 foot range again. And then the day was late and we needed to pack up and go.
Looking at the video footage a few days later, we found that not a single shot was even close to optimal. Either we were releasing before stall, or we were releasing after stall, or releasing at terrible trajectories at stall. For now, it seems that a sling roughly 5' 6" long at the full 300 pound counterweight with a really steep release pin angle should get us a good launch. The sling was just too long at 6 foot, and seemed a bit short at 5 foot. We will test this theory at a later date.
Here is a summary of the 14 shots from today. All were with the 4 pound medicine ball.
|Shot #||Counterweight (Pounds)||Sling Length||Distance (Feet)||Notes|
|8||125||6'||50||Very late release.|
|9||200||7'||backwards||Bad pin angle.|
|10||200||7'||65||Very late release--arm moving backwards.|
|11||200||6' 8"||~65||Very late release--arm moving backwards.|
|12||300||6' 8"||~65||Very late release--arm moving backwards.|
|13||300||6'||~80||Late release--arm moving backwards.|
|14||300||6'||~80||Late release--arm moving backwards.|