Statement of the Problem     

The purpose of this investigation is to determine the effect of the counterweight has on the overall traveling distance of the projectile.

Review of Related Literature

Researching the history of how trebuchets were created is as important as knowing how to build, operate, and evaluate the results. Since there are so many variables involved with these medieval siege weapons, we limited our research to the topics the most dealt with counterweight mass and its effect on range of the projectile. Talbot's information served as a great source. He analyzed that "there are many important areas of conservation that the trebuchet uses, ranging from energy, torque, and Newton's laws of motion"(Talbot).  On Dan Becker's Trebuchet Page, we found the most helpful in the actual construction and understanding of trebuchet mechanics. He points out that the counter-weight arm is should also be hinged. Basically this allows the weight to fall more vertically than a non-hinged arm.

The other sources served as basic information on how to successfully fire a trebuchet and that a heavier load will fire a lighter objects farther if the firing pin releases the sling at the correct moment. All this assessment of the background information allowed us to plan out, construct, and properly fire a trebuchet.

Hypothesis

We believe that as the counterweight mass is increased the range efficiency will also increase. While leaving the firing pin at a constant angle and the launching arm a constant length, we can create a hypothesis. When the heaviest counterweight mass is used, then the projectile (golf ball) will travel the farthest distance.

 

Method

Materials

Trebuchet (for throwing projectiles)

Golf Balls

Measuring Tape

Different Weighted Counterweights

Procedure

The first step taken was the construction of the trebuchet. Using online constructions and personal calculations, we were able to construct a trebuchet with a hinged counterweight and sling fore the projecting a golf ball. Once the trebuchet was painted with Optimus Prime, we then set up a space where the launching would take place. We laid out a tape measure 140 feet out from our trebuchet; we hoped it would go at least this far. Starting with a five-pound counterweight, we drew back the arm, released, and watched the ball fly. We performed 10 tests total with this weight and recorded how far the golf ball traveled. Since we were in a wet grass field, the ball stuck in the ground, so we didn't have to worry about wondering if it had rolled or not. We performed 20 more trials total, 10 test at 10 pounds and 10 tests at 11 pounds. Repeating the same exact procedure for all and recording the data, we gathered the information and created tables and graphs.

Results  

Raw Data (in excel spreadsheet)   Raw Data (text)

Data File: excel .:. text

Conclusion

In examining the results that were collected, it is apparent that, the data favored our hypothesis. There was a distinct difference of how far the golf ball went as the counterweight mass increased. The heaviest weight used was 11 pounds, and flung the golf ball over at least 115 feet every time. We found that this counterweight mass did indeed launch the ball the farthest compared to the other counterweights. As we tested each mass, the trebuchet showed a stunning accuracy as far as how far the projectile went. By looking at Distance Vs. Trial graph, we can see how the line for each separate weight is fairly steady, meaning there are no sudden drops or increases. This proves how accurate "Prime" trebuchet really is. At 5 pounds, the range had an average of 66.3 feet. This is accurate because there weren't any outliers that would corrupt the data. This proves true for the following weights as well, with the 10-pound mass averaging around 105 feet, as the 11-pound average toss is 119 feet. Studying the second graph we notice the two major raises in distance, showing were the changes in mass took place. It shows how when more weight is added, the farther the projectile will go. Looking at the highest point in trial number 29, we can see its max range at 124 feet with 11 pounds as the counterweight.

In conclusion, our hypothesis was proven correct, because the heaviest counterweight produced the farthest distance. Unfortunately our trebuchet couldn't hold much more weight because the axel pin stated to bend, so we only could get up a little bit past 10 pounds. We suspect id the pin didn't start to bend. There would be a point at which more weight wouldn't help the distance because there would be a max trajectory angle. We weren't able to discover this point. We used the same type of golf ball, the Nike Mojo (mass of 42 grams). We tested with six balls. There could be some error with how clean the golf balls were. Dirt on them could've added some excessive air friction, which would have affected the distance. We used free weights as our counterweights, so we were sure on the accuracies of those. This research project was a success, because we built a working trebuchet that proved our hypothesis correct.

Sources

Becker, Dan. Feb. 2007. "Dan Becker's Trebuchet Page," Trebuchet <http://www.io.com/~beckerdo/other/trebuchet.html>

Bullock, Tom. Jan. 2005. "Trebuchets" Grey Company, The. April 2004. "The Grey Company Trebuchet Page," Counterweight Trebuchets, Soedel, Werner. July 1995.

"The Trebuchet," Scientific American, 66-71. Talbot, Paul E. 2000. "The Invention of the Counterweight Trebuchet: A Study in Cultural Diffusion," Dumbarton Oaks Papers, No. 54, 72-116.

Links

            http://www.io.com/~beckerdo/other/trebuchet.html  -  Plans and directions for building a small trebuchet

http://www.tbullock.com/trebuchet.html  -  History behind the trebuchet 

            http://www.ripcord.ws/theory.html  -  Theory and mathematics of trebuchets

            http://www.algobeautytreb.com/ -  Algorithms of a trebuchet

            http://www.legionxxiv.org/trebuchetpage/  -  History and details of the trebuchet