<p>D came home Thursday, she is taking Physics this summer, full year in 6 weeks. Anyway, she and two classmates had this weekend to build a working trebuchet (kind of like a catapult) that could throw a tennis ball 45 YARDS…needless to say, after numerous trips to the hardware store, it can throw em 45 feet. Argghhh. 15 dollar budget, weekend plans shot, and I have broken my nails…</p>
<p>Anyway, anyone have any ideas for making the sling?</p>
<p>No.</p>
<p>But three things that appear key upon summary reflection are 1) the length of the throwing arm and 2) the amount of stored energy in the propelling system and 3) how fast that stored energy is released, e.g., if the arm isn’t whipped fast enough, you won’t get much range.</p>
<p>how do you whip the arm? the weight, and should the weight be in a bucket and we can’t get the sling shape right- ie balls falls out or gets stuck, and we can not determine length of string to attach sling, we are working from scratch, there was no time to really pull together a great machine…how do we determine the ratios? teacher is no help, and what we find online is for ginormous machines…we can only go 1/2m by 1/2 m by 1m (with arm lenght whatever we can make work</p>
<p>…what a nightmare, all weekend…we missed a graduation party, and cancelled our plans</p>
<p>Ever read Dave Barry on the Trebuchet? Not much practical help, but hilarious.</p>
<p>I wonder if whether the throwing arm throws it upwards or downwards matters? like a overhand or underhand pitch?</p>
<p>I saw something on PBS where people reenact these ancient battles; building catapults etc (for fun!) in England. Maybe you can find out what they did to be successful. </p>
<p>Of course everything had to be completely low tech as it would have been at the time-- in their case I recall it was finding a counterweight system that was sufficient to get enough force to throw a basketball sized stone at a castle wall and create a hole in it.</p>
<p>here is a link to the show I saw</p>
<p><a href=“http://www.pbs.org/wgbh/nova/lostempires/trebuchet/builds.html[/url]”>http://www.pbs.org/wgbh/nova/lostempires/trebuchet/builds.html</a></p>
<p>looks like it contains a few good hints</p>
<p>Try some of these</p>
<p><a href=“ripcord.ws”>ripcord.ws;
<a href=“http://www.trebuchet.com/index.html[/url]”>http://www.trebuchet.com/index.html</a>
<a href=“http://64.233.187.104/search?q=cache:-bcJhnsFXmIJ:www.soinc.org/stormc/+science+olympiad+trebuchet&hl=en&client=firefox-a[/url]”>http://64.233.187.104/search?q=cache:-bcJhnsFXmIJ:www.soinc.org/stormc/+science+olympiad+trebuchet&hl=en&client=firefox-a</a></p>
<p>We built a trebuchet in AP Physics. How big is your counter-weight?
Our’s was a 45 gallon bucket filled with cement. Our distances (tennis ball) were in the 35 metre range. The throwing arm was perhaps a metre and a half, and the sling from that was another half metre, I would guess.</p>
<p>Wish I had read this earlier.</p>
<p>This is the site I used, it goes through pretty thoroughly what you need.</p>
<p><a href=“http://www.io.com/~beckerdo/other/trebuchet.html[/url]”>http://www.io.com/~beckerdo/other/trebuchet.html</a></p>
<p>Of course that’s on a smaller scale but just up the scale to what you need.</p>
<p>I’m a hobby timber framer. Many of my friends have worked on treb projects including the one on NOVA. They are tricky to tune. Go to the Timber Framer’s Guild website <a href=“http://www.tfguild.org%5B/url%5D”>www.tfguild.org</a> and post a question or two. Some of the guys will respond most likely.</p>
<p>My son had to build one that would throw a pumpkin 50 to 100 yards… they do this in October, with the performance test the 1st wk in November and they hurl all the discarded or unused pumkins… I agree that it was extremely tedious for the entire family…rides to the dump for the lumber… we cut up an older Bean’s bag to form the sling… you might want to see if you have a lightweight nylon mesh bag? The handles usually are reinforced well… if you have a filing cabinet or two, see if it has metal plate weights in the bottom to keep the cabinet in place when a file draw is pulled out? if so, you can use those metal weights for the project also… I have 3 or 4 of the 3 drawer cabinets and the kids used a bunch of those for the project… and definitely search the web… there is still time to do a good job on this, because by now you have started to understand how it all works and what you need to do to be successful…if I remember correctly it was about 4:30 on Sun pm when my son’s came together… try not to focus on all the other things you could be doing this weekend…and just know you will always have the Trebuchet project to look back on with your daughter… there are definitely funny shows on TV about trebuchets, one where they were throwing old washing machines… and of course there is always Monty Python and the Holy Grail where they launch cows over the castle walls… have FUN with this… it is kind of neat.</p>
<p>thanks for all the advice…I know I should be excited, but we had to cancell ALL our previous plans- graduation lunches, dinner with friends, to work on this because we had Friday, Saturday and Sunday to do this with a budget of 15dollars</p>
<p>So, we are a bit peeved at the teacher. And the teacher is grading on distance, 1/2 a football field!!! </p>
<p>Did anyones go that far with a meter high trebuchet? ARGGHHHH</p>
<p>This is from my DH:</p>
<p>Is the meter high the height of the pivot?</p>
<p>You already have some good answers about the sling material, etc. </p>
<p>You can bend/adjust the release pin for the sling to change the angle of release. This is somewhat trial and error, but your D is going for as close to a 45 degree angle as possible. </p>
<p>Good pivots bearings - WELL-LUBRICATED - will help. </p>
<p>The counterweight should be as heavy as possible with the longest drop possible - will give you the most energy. DS used barbell weights on his SO trebuchet for testing. KEEP ALL FINGERS CLEAR OF ALL PINCH POINTS WHEN YOU JACK UP THE WEIGHTS. </p>
<p>Do not stand behind the trebuchet. </p>
<p>Try searching on the science olympiad storm the castle events. </p>
<p>Good look to your D!</p>
<p>These kinds of projects are fun; I did one in woodshop back in the day. Having shop facilities makes them much easier. I don’t remember the exact distance my projectile traveled, but it was probably something like 100 feet. Just make sure to get good weights for it - I used a bucket of old lead type and old steel bars, which was quite heavy. Generally, the heavier the weights, the farther it throws.</p>
<p>On the Nova site, having wheels on the base of the trebuchet dramatically increased distance.</p>
<p>Ha. I went around the block with my daughter’s physics teacher on the trebuchet project.</p>
<p>He handed out the assignment out of the blue with one week’s notice on a Friday to be completed by the following Friday – the same week as ED college apps were due and long after it was too cold and too dark at night to be setting up the saw in the driveway. His rules, the weight of the ball being thrown versus the dimensions made no sense (it was going to be able to achieve a theoretical max throw of about 2 feet!)</p>
<p>I e-mailed him and asked him if he had really thought through the contest. Like, how in the world kids without indoor workshops were supposed to do this project when it gets dark at 4:30 after school and it’s 32 degrees outside?</p>
<p>Were parents expected to just hand over the skil saws and drills to teenage girls, unsupervised? Had he researched the requirements for throwing a ball of the weight he had in mind? Were the top kids in his class supposed to drop their ED college apps due that week to build a tebuchet with one week’s notice? I told him that my daughter had two college apps due that week (she had gotten an early start, but there’s still a lot of last minute work in a good application) and that I would probably tell her to just forget the trebuchet project and take an “F” on the assignment</p>
<p>He said that he really hadn’t thought about it at all. It just seemed like a fun project (I agree) and that there was no pressing reason it had to be done that week!</p>
<p>i actually made a trebuchet for physics. make sure the base is stable so that the heavy arm wont tip the trebuchet. make several adjustments with the arm and see at what pt it is the most efficient.
i actually filmed the projected arm, put it on my computer and put it on slow motion. there i could see where the ball was being released and it helped overall.</p>
<p>I love all the advice, but remember, we had a budget of 15 dollars- we spent 9 hours yesterday and so far 6 today and its due tomorrow- they were given assignment Thursday!!!..</p>
<p>what if you live in an apartment and don’t have room for buckets, and cement, and saws and drills…</p>
<p>as well, they were not allowed to download plans…</p>
<p>We would have loved wheels, but that would have been close to the whole budget. Same goes for all the mechancals, which they weren’t supposed to use. The arm and the axel thing all had to be wood only.</p>
<p>Here’s what teacher said</p>
<p>45 YARDS an A
40-45 YARDS an A-
35-40 YARDS a B
and so on</p>
<p>so even after spending our whole weekend, cancelling plans, borrowing tools, husband cancelling golf, the girls will most likely get a C. While some kids who cheated, downloaded plans, and engineers for fathers or mothers will get A’s</p>
<p>And what did they learn? Nothing. Only that the sling is the hardest thing to make because either the ball releases too soon or not at all. Some lesson. </p>
<p>I am having girls type of notes for the trials and adjustments they had to make, so if teacher is a (*&$^&% head, and we parents need to talk to him, we have some ammuntion.</p>
<p>Want to here the teachers excuse for gibing them one weekend: that most kids do it on the last weekend anyway!!! Argghhh</p>
<p>One girl was supposed to go to Yosemite, parents rented cabin and everything- they cancelled. Another missed brother’s graduation bbq.</p>
<p>Oh yeah, and Ds partner had a free ticket to Minn. to visit an Aunt and go to mall of America!!! Okay, I have gotten it out of my system so if DH and I need to talk to teacher, I will be CALM AND RATIONAL!!!</p>
<p>Thank goodness for you guys!!! Good suggestions, just wish we had time!!! and good support!!!</p>
<p>I heart you all!!!</p>
<p>At the magnet school that I attended, we had to do a trebuchet project as freshmen for a project in physics (which, for me, would be going on four years ago now). Instead of making the trebuchet, we had to accurately calculate where we wanted the projectile to land. Anyway, before they get a smaller trebuchet that created more accurate results (with much less risk of hitting someone or a passing car which was what my class used), they used a huge sling that would hurl projectiles several yards I believe. I believe it was made out of a large rubber cord and some sort of holding space for the projectile in the center. You could use a baseball mit or something. I’m just giving out ideas based off of what I’ve seen in the past off of which you could create new ideas and twists for the project.</p>
<p>(I remember that a few years ago on the last day of school, we got to play with the old sling. We played a game in which we used the sling to shoot water balloons at each other. I believe it was supposed to be a modified game of baseball. ;))</p>