Monday, October 5, 2009

Yankee Siege Update - September 27, 2009

This spring and summer have been a very busy time for Yankee Siege. I haven't had the time to update our progress. We have been visited by four TV shows. Time Warp (Discovery Channel), Lock and Load (History Channel), All Jacked Up (Country Music TV), and The Science Channel following teams to Punkin Chunkin (more about the shows later).

This year's Punkin Chunkin will almost surely see the two thousand foot barrier broken by a trebuchet. Yankee Siege's goal is to break the 2500 foot barrier! We have fabbed a brand new throwing arm and unveiled it for the first time in front of the cameras for Discovery Channel. The arm is very light and fast! We have reduce the weight of the arm to a mere 600 pounds, down from our previous arm of 800 pounds, down from the original arm of 1200 pounds. Not only have we reduce the weight but we have moved some of the mass of the throwing arm considerably closer to the axle, with the effect of significantly lowering its moment of inertia (resistance to a change in rotational velocity). We are still running 12,000 pounds in the counterweight (94,000 foot-pounds of torque, max). We have only done two throws at the time of this posting. I don't know if the arm can take the stress. If the arm holds up, we could potentially break 2500 feet this year. The cable stayed throwing arm has remained straight as an arrow with these first two throws.

We are unable to accurately measure the distance of the throw. At the 1700 to 1800 foot range the pumpkin disappears into some pine trees on the far side of a ten acre wetland. We can only estimate how far into the pines the pumpkin has flown. The first two throws were very far. They were also very low. Almost a line drive. They left the machine at tremendous speed. We will have to adjust the pin angle or sling length to get a higher path. The second throw appeared to rise about halfway through its flight and just kept climbing and didn't reach a peak till somewhere around the 1500 mark.

The extremely low trajectory would seem to indicate that the throwing arm is rotating significantly faster (higher angular velocity) than our previous throwing arm (the throwing arm is able to "get ahead" of the sling causing the sling to release a little later (similar to the effect of adding more counterweight).

We will be doing public demos at the farm stand for the next five weekends. These demos serve as our practice sessions for Punkin Chunkin.

P.S. Lumina pumpkins are very hard to find in New England, we had a very wet and cold June and July. We will have to practice with orange pumpkins. Does anyone have a souce for Lumina's? If you have a source please e-mail us, Thanks.

P.S.S. A special note to Merlin and Pumpkin Hammer, Good Luck in your practice sessions, stay safe and hope nothing breaks. See you in November.

Steve Seigars, YS

1 comment:

Deane said...

Just a thought on increasing the performance. Don't forget the aerodynamics of the rotating arm. If it is covered with an airfoil fairing it will GREATLY reduce the air resistance. The drag goes up by the square of the speed so your faster arm will benefit even more.
Deane