Today we took out Jeckyl and Hyde once again for some launching as a King Arthur-style trebuchet. The arm had been completely rebuilt after last month's failure, though nothing had been done to smooth out the ribbed secondary release pin. However, it looked early on as if this was not a problem. Once again, we launched baseballs with 50 pounds of counterweight, since we are not willing to up the counterweight until we get a day of good launches were we do not break anything. Only then will we feel comfortable upping the counterweight.
The first shot roared downrange at about 80 miles per hour at a roughly 25 degree trajectory, landing 275 feet downrange. The secondary trigger released a bit early, but not by a lot, but the arm had a ton of residual energy left in it, as the tip of the arm rotated so far forward that the pin behind it that holds it in the secondary trigger hit the ground. Still, the frame did not rock at all, and the counterweight did not hit the frame as we had switched to a shorter counterweight axle.
It looked like we were in business. The second shot was virtually a carbon copy of the first, though it picked up a little distance in landing 280 feet away. The angle of launch was a little bit higher on this one, but everything else looked the same, with the secondary triggering a tad early and the arm tip hitting the ground. All was looking great.
Then the third shot came, and disaster struck. The secondary once again failed to release at the proper time, and the counterweight smashed into the arm. In the process of the arm whipping around after busting free of the secondary trigger, the sling lines somehow got caught on the arm, halting its movement briefly until the pouch ripped. This was our newest baseball pouch, and one that was designed to be very tough to rip. Well, it happened anyway. Aside from the pouch, however, there was no damage suffered by the trebuchet. So we whipped together a quick unisling-type pouch and fired once again.
This shot was better in some ways, but the secondary still failed to open in time and the counterweight smashed into the arm, sending it spinning around until it came to a rest against the center cross brace of the frame. The baseball, in the meantime, had shot straight out backwards and rolled some 150 feet away. And we were not so lucky as to once again avoid damage to the machine, as the center hanger arm, since it was forced against the arm in a position it was not meant to be, split right down from the hanger axle hole through its top end.
Since the center hanger is what keeps the machine stationary when cocked as a King Arthur, we could not fire anymore today. And once again we had to pack up early due to breaking something. 3 full days of launches, plus the initial test shot back in February, and we broke something all four times. Not a good track record for our first venture into the world of super-propping. And we haven't even gotten around to firing as a whipper yet.
After some analysis of the videos from today and lots of thought, the problem with our failing secondary may not lie in the eyebolt pin as we had previously thought, but with the route of the cable. It is not guided along the very end of the short arm, and it seems that the cable may be slipping between the short arm and the hanger arm on that side instead of running along the length of the short arm as can be seen in video of the good shots. Some more experiments in the shop are due before this can be pronounced the cure, but the addition of a tubular guide along the end of the short arms should eliminate this problem for good, and then we can hopefully start to attain the long distances we hope for from this machine. From what we have seen, 500 feet does not seem unreasonable with 50 pounds of counterweight powering the baseball. We're close, and can feel it.
|Shot #||Counterweight (Pounds)||Sling Length||Distance (Feet)||Notes|
|1||50||5' 8"||275||Nice smooth shot, low launch angle, slightly early secondary, arm tip hit ground in front.|
|2||50||5' 8"||280||Nice smooth shot, high launch angle, slightly early secondary, arm tip hit ground in front.|
|3||50||5' 8"||backwards||Secondary failed, arm caught on sling and ripped pouch. To quote Chris' notation in the log that he kept for us, "CRAP!"|
|4||50||5' 8"||backwards||Secondary failed, center hanger split.|
There is also video from today in the Jeckyl and Hyde Video Gallery.