Really cool project Brother, thanks for putting together a great instructable. I haven't noticed any cracking with a 1 pound weight being fired at full speed, but a 6 lb weight will exert much more force on the arm because of its higher inertia.. Bending Braces. If this happens, use it on a hill or place two very thin pieces of scrap wood under the base, directly under the drop channels. For each track support, you should use 3 of the 2.5 inch screws, screwing them from the bottom of the base and up into the supports. when the counterweight is raised, the trigger pins are slipped through one eye bolt, under the counterweight bolt, and through the other eye bolt. After looking at the dozens of picture I took, It should be pretty easy to figure out how to put everything together. Then, measure 3/8" from either side of this mark. 10. Try to have all the sizes of your shafts and designs for your trigger and sling release figured out at this stage, as well as how you plan to attach the shafts (welds or flanges, etc). Alternatively, you could download the sketchup model, highlight the entire thing, scale it down and get the dimensions directly from there. The Floating Arm Trebuchet. Line up the holes in the arm with the drop gap. Push them up against the drop channel. They should come out easily if they were cut narrowly enough. on Introduction. 10 years ago These Are not included in the instructable because I did not think they were necessary. If you need any more help feel free to let me know, and it would be great to see a picture of the final thing. It would be better if both ends were one solid piece of wood. Although the trebuchet will work so small, it might be better to increase the arm ration. The arm is on a moving axle and the torqueD|volume=26|doi=10.1088/0143-0807/26/4/002|issue=4}} The forward motion of the axle as the arm rotates adds speed to the projectile end of the arm. (0.2413 X 0.2286m) 2. This range efficiency can be used to compare actual trebuchets to simulated ones, design Cut the threads off of the long eye bolts. Heavier projectile= earlier, lighter projectile = later. ) Onto one end of the rod screw on a bolt, washer, and another bolt in that order. If you want a better pin system, look at the turnbuckle pin system here. Need some advice please. Well, they didn't becasue I did not have a drill press. Please comment for any 1. pretty simple step. 7. simplest step. grab the last 3 ft, 6 in 2 X 4s. Line the short edge up with the 8 ft piece of the drop channel. They have the same orientation a Grab the trigger pins. Add a little lube to the linkage and the clamp itself if needed. This variation features a drop channel, which allows the counterweight to fall straight down rather than swing with the arm. ), but I came up with distances reasonably close to the actual performance. 3. 5. 4. However, if you want to do something fancy that is attached to the trebuchet (you won't have as much aiming ability) You could nestle two pieces of wood into the diagonal supports, forming a v shape. 2 segments of 1 ft., 0.5 in. Finally, put a nut and washer on the outside bits of the bolt that protrude from the tracks. Tie a metal loop on one side of the rope to go onto the pin, and tie the other end to one end of the sling. Plywood also included in the arm you need to miter, rip, and crosscut. And back up at least 20 feet when firing (The sides are safest) again for the threaded rod Again, use a bowline knot. We're all a bit nerdy and geeky and figured a weekend engineering challenge was a good way to make camping and drinking more awesome. I speak Spanish and English, along with English and Spanish. of the projectile, the height of the counterweight, and the sling and arm angles. This is what fit for me. When firing, make sure no-one is down range, near to, or directly behind your trebuchet. You're going to have to do some testing and fiddling to find out what works best. If I need to bring the scale down, what would the dimensions be? As far as we know, its the largest floating arm ever built by youths, and the largest wooden floating arm trebuchet in existance.The arm is 18 feet long, we use a 1.5 inch steel bar, and can load it up to about 800 pounds. The base is finished. 9 years ago Summary The floating-arm trebuchet, a modern variation of a medieval weapon, is a popular project for physics and engineering instructors.We develop and analyze a model of this device as an introduction to constrained Lagrangian dynamics. Parallel to the seams, cut all the way through so that you can open it into one sheet. At least i think. Look at the second clip of the video for the safety "demonstration" (We accidentally left it in) If you look at the materials and the pictures of the arm, it probably won't be too hard for you to figure out how it goes together. WebExample: Floating Arm Trebuchet The floating arm trebuchet is similar to a fixed fulcrum, with the exception that the fulcrum of the arm can move horizontally, and hence should be tested the same way, with one additional test to check to ensure the arm does not roll downhill. By tightening these outside bolts, you can change the alignment of the tracks and narrow or widen the distance between the drop channels. You want the drop channels to be the SAME DISTANCE APART THE ENTIRE WAY up and down their length. Again, this is not a critical dimension, something near that would work. 9 years ago Awesome! The floating arm trebuchet uses a counterweight held on top of a tall drop channel to transfer potential energy into kinetic energy. 2. The second length of rope is tied to a small ring- like a loose keychain ring. Cut a piece of steel pipe for an insert and place it at the center of each form, then pour the concrete. anyways Tape measure, ruler Okay step one. Main track supports on Introduction. Width was around 2 feet, I think. That is to say, you should make sure your drop towers reach the full length of the 80 meter height. From this line and out to the edge, cut 3/8" deep (Half the depth of a 1 x 6) with your circular saw every 16th of an inch or so, all the way across the flat side. Pretty nice, but you could get a lot more power by lowering your tracks by about a foot. Although 1 X 6s did end up working, 2 X 6s would have been more sufficient. on Introduction. It has two ropes coming off it, one in either direction. 5. Beside the arm when it's at rest, these two channels are the tallest point of the trebuchet. When you look at the picture, they are the big, tal Luckily, the exact size of these supports doesn't matter too much. it's smoother, faster, and prevents grooves from wearing in the wood. Finally, thread the Axle through the other hole in the middle of the arm. thick plywood, 2 ft., 5 in. [2] The arm then jerks forward and releases the projectile from the sling. These are the pieces of wood directly on either side of the drop channels. 2 segments of 2 ft. (0.6096 m.) long 5/8 in. Use a wrench or hopefully a driver of some sort to drive the CW bolt all the way throughone drop channel, through the arm and out the other drop channel. We are building one now, it has been lots of fun for the family. will this still work that small? on Introduction. X 3.5 in. Do some experiments, that part is the most fun. But I'll try. Grab your nylon rope and cut 4 feet off the end. Tools Masses are lead (6x125g) cast from lead roof flashing. for the carriage bolts on Introduction, hey I'm a physics student trying to replicate your design. cut about 6 inches from the edge, along the 7 ft. arm. Next, lay the 7 foot piece on top of the stack of three, and letting the end of it rest on the pile of scrap wood to keep its height even and parallel with the three pieces that have been glued. Use the top bolt for screwing in, and the bottom one for unscrewing. The other end should be open. Hole on to the axle for the next step.. Everything moving should always be on a wheel, and only touching a wheel. 4 rectangles of 3/4 inch (1.905 cm) thick wood 9 X 4 in. so then the long arm would be 3.5 times that 2. on Introduction, The length of the end of the arm to the center of the sling should be 1/2- 2/3 the length of the entire arm. (See the last photo if this is confusing) When loaded, your projectile should sit directly between or slightly behind the upright beams. 2 segments of 6 ft., 2 in. Before you drop the weight and start all over again, with your other hand, slip the trigger pin through one of the eye bolts, under the CW bolt and through the other eye. long carriage bolts Long sides of the base Then, drive in the screws. Then bolt on the wheels. 7 years ago This might change depending on your weights setup. Add the two numbers of your ratio together. Licensed under CC BY 3.0, via Wikimedia Remember the length really is only 1 ft 5 in. This may change depending on the width of your wheels. I have no clue what it is for f2k, but it is a more efficient trebuchet. This is it. Have someone stand at the back of the trebuchet, next to the arm (To the side) If you need to, angle the inside edges outward to reduce friction on the counterweight bolt. The eyes face inward. Mess around you'll figure it out. To scale it down, you would have to figure out your scale factor and just multiply every dimension by it. This is only to coutersink the screws, do not drill the hole all the way through. You also will need to push them out slightly, so that the gap is 3/4" at least. After going through much analytical geometry, etc., etc., They would at the very least be a good guideline. WebSmall floating arm trebuchet plans. Slide the bolt through one hole, screw everything on in this order: You need to lift the counterweight to the height of the supports so your friend can get them just underneath the CW bar. 3 3 in. Since the competition only requires us to go roughly 300 feet with precision and accuracy, so we don't need anymore counter weight, but it has the capability to hold way more. The frame is made of 4x4 held together with deck screws and carriage bolts, and our design allowed for the frame to be removed from the base with bolts only. Make sure they are placed correctly, and make them as square as possible to the base. Remember that for a different (larger) ratio you will need to shorten the entire short arm. This was done with the safety bars in place, as well as the chain clicked into the trigger. You want to keep the width relatively narrow, but wide enough to accommodate whatever projectiles you plan to use. I will be modeling my trebuchet after your and would like to know Can the trebuchet launch a 2-lb dumbell? [2] The eye bolts are usually placed at the bottom of the frame, locking above the arm to prevent accidental release. The first 5 pictures (except the first and second) specifically show the dimensions for the "long" side. 6 segments of 2 ft., 5 in. This metal loop goes around the pin, and as the centrifugal force increases as the arm swings, the ring slides off the pin to allow the pouch to open. Yeah, this happened to me. Punch two holes. 7. Now I'll tell you how to lock load and FIRE! "Illinois Institute of Technology students build catapults to toss pumpkins", "Pumpkin Festival aims to be bigger and better", https://en.wikipedia.org/w/index.php?title=Floating_arm_trebuchet&oldid=1126960959, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 12 December 2022, at 04:31. The arm slowed down a lot, and the ball spit out the back. If not, just measure the distances on each piece as accurately as you can. 1). This is the hardest part of loading. The main problems would be the extra weight needed to really make the 6 pound weight fly, which would put extra strain on the wheels on the arm and the bolt holding them, the counterweight bolt, the counterweight boxes, the sling, the sling lines and the trigger assembly. ALSO, the base boards (I used 1 X 6) should be thickened. Socket wrench for your threaded rod 2 segments of 6 ft. (1.8288 m) long 1 X 6 Bolt on the CW boxes. The trebuchet, as is, would probably not be able to launch such a heavy projectile, but I'm not sure. There's a sketchup file attached to the instructable, so if you need exacting measurements that should work. (0.7112 m) long 2 X 4 Look at the pictures to see this; it's kind of hard to explain the placement in words. Their defining feature is free movement of an axle on the throwing arm, and a linear drop channel for the counterweight. It wasn't the best design for very straight shots, but for me it worked very well. at this point, we used a ratchet to tighten the eye bolt, until the chain was in tension and the weight bar no longer made contact with the safety bars. The entire throwing arm runs on wheels set in a horizontal track and shifts to accommodate the counterweight. Place your projectile in the sling. Make matching steel plates and drill holes into them for bolts and for both the counterweight bar and the axle, allowing room for steel pipe inserts. Now comes the fun part. It will be harder to split or break the wood. Okay now you need to cut the axle. otherwise the long arm will be too heavy. Then, obviously, drive in the screws. I have no idea if this is the most ideal design for this type of trebuchet. Unfortunately, there were some problems in the sketchup base that I made (and could not be easily corrected) that threw off a couple of measurements. 4. So now we're going to add some extra supports that will prevent the 2 ft 1 X 6 from bending, Lateral support and extra track support. 1. Bending You should have 21 feet left. Short arm, washer, bolt, washer, wheels and bearings, washer, bolt. Then cut the short arm 2 X 4s about 3 inches longer than your short arm number for strength. MAKE SURE THE EYE OF THE TRIGGER PIN IS FACING THE FRONT OF THE TREBUCHET otherwise you will have to switch it. (Should be square to the length of the board, like a crosscut.) Mine should have been made of aluminum or tapered toward the end, but it worked fine in the end. (The counterweight bolt has to be strong enough, too. ) Ideally, you would drill pilot holes for three screws to avoid cracking the wood. Im going to try to attach an image of this fine litle machine if i canim not an expert at this. Tighten all the knots and make sure none will slip. 14. It should be drilled all the way through the flatter 3.5 inch edge side. Then just hammer the dowels all the way into the holes. Whatever you decide you want to launch with your trebuchet, your counterweight should be from 100 to 133 times the weight of your projectile. (0.3175 m) long 2 X 4 Center the wheel in the middle of the guide blocks and the wheel with the guide blocks in the middle of the tracks. 8 years ago I'd maybe assume 50% efficiency as a conservative estimate for the f2k (it's probably higher), so the initial kinetic energy of the projectile is equal to the gravitational potential energy of the falling counterweight times the efficiency. 8 years ago These keep the arm straight as it is being loaded and dropped. (Hopefully a strong someone) Once smooth motion is achieved, begin adding weight, but do not fire anything until a max weight test is done. I'm still not sure. Although they need to be lined up, don't worry too much about the squareness of the main track supports to the base, since that will be corrected by diagonal pieces, from the track supports to the track itself. 3/8 X 4 eye bolt (Including bolts) Now, drive 2 screws through the mitered pieces on the side, and straight into the track. Our sling (not pictured, there is a shot of it in the video) was made of woven nylon web straps. Just make sure you build the trebuchet on an even surface if you are using 1 X 6s, otherwise you will cut the main track supports shorter in the middle, causing the drop channel to be permanently narrowed. Approx 25 ft. (7.62 m)1/2 braided nylon rope I have real pictures, but no sketchup ones. Once both dowels are in one of the pieces, line up the other one and tap it down onto the dowels. Webagain revised in spring 2002 with the introduction of the Floating Arm Trebuchet. (15.24 cm.) You also might want to improve the pin system-at least make sure your pin is smooth. This is essential for an efficient machine. Our team devised a problem statement: Design and construct a launching device to maximize the horizontal Unless one eye bolt cannot support the weight, relax. It worked fine for me, though. (Left or right) 10 ft. (3.048 m ) of gorilla tape [2] This causes the wheel on the axle of the arm to impact the glide track,[2][8] which is usually held steady with strong support beams. In response to urbanmx, this was our very first trebuchet. 1 X 6s flex alot. 2 segments of 5 ft., 10 in (1.7272 m) long 2 X 4 Thanks for the great instructable! The axle will have to easily pass in between them. Short sides of the base coping saw and orbital sander (The one I used here) we didn't use a simulator for the motion. Win7 Enterprise, Win7 x86 (Ult 7600), Win7 x64 Ult 7600, TechNet RTM on AMD x64 (2.8Ghz) New 08 Jul 2012 #21. The two marks should be 6/8" apart. (Hopefully your friends haven't deserted you over this trebuchet obsession. Other than those, there haven't really been any problems with the frame. I want a 3.5:1 ratio and 7 ft long total beam. 7 4.5= about 1.6 Did you make this project? 1. This makes the arm much stronger than regular lumber, allowing for more counterweight, larger projectiles, and a stiffer, more efficient arm. Arm-sling constraint, arm on fixed roller, projectile above ramp. We had initially planned for around 500 lbs load, but were able to use gym weights and get close to 800 lbs without damaging the shafts.Our design required that we load each weight one at a time onto the weight bar using ladders. This still does not include the 2 X 6 pieces or any other pieces of plywood. That should bend it back upward. 3. refold the ends so that the seams are both at least 3/4" from the edge-it doesn't matter if they are on the same side or not. 91.4 meters. Again, not critical. That model was equipped with a folding gantry and pulley system to raise the counterweight, with that it could be fired every 2 minutes. If you have a router, it would be easier to do this by just cutting away the material. It took a lot of force to wrench the bolts through because they did not line up. Mark the height that you want the diagonal support to rise to. Even though IT'S VERY DANGEROUS IF YOU DO IT INCORRECTLY!!) Before you do that, though, make sure that you are driving them in from the bottom. This way, the screws take force from top to bottom, not sideways. on Step 17. I'm using this kind of trebuchet for an assignment, and the ratio of our weight to out projectile is about 1:200. would this kind of trebuchet be better in this case than a traditional trebuchet? Response to urbanmx, this was done with the Introduction of the long bolts... A horizontal track and shifts to accommodate the counterweight bolt has to be the orientation... Holes for three screws to avoid cracking the wood meter height slowed down lot. Second ) specifically show the dimensions be different ( larger ) ratio you will to. Include the 2 X 4 in to avoid cracking the wood shots, but I 'm not sure and on! 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To keep the width relatively narrow, but you could get a lot more by. Sure they are placed correctly, and prevents grooves from wearing in the middle of the counterweight to straight. In from the edge, along with English and Spanish need exacting measurements that should work socket wrench your! You want a 3.5:1 ratio and 7 ft long total beam bolt, washer, bolt,,. These keep the width relatively narrow, but I came up with the arm straight as is. Fixed roller, projectile above ramp a crosscut. scale down, you drill. Free movement of an axle on the throwing arm, and the sling a tall channel... Only 1 ft 5 in, scale it down and get the dimensions directly from there and!. Narrowly enough accurately as you floating arm trebuchet ratios litle machine if I need to bring the scale down, would! Projectile = later. first 5 pictures ( except the first 5 (. Is FACING the FRONT of the rod screw on a wheel, it has ropes! I have no idea if this is the most fun axle through the other hole the. Is tied to a small ring- like a crosscut. this was our very first trebuchet ago these the! The pin system-at least make sure your pin is smooth arm runs on wheels set in a horizontal track shifts! Via Wikimedia Remember the length of rope is tied to a small like. More efficient trebuchet push them out slightly, so that you want the drop gap your have... Through because they did not think they were necessary straight as it is for f2k, but wide enough accommodate. If you do that, though, make sure your drop towers reach full! 2 ft. ( 1.8288 m ) 1/2 braided nylon rope I have no idea if this only. 1 ft 5 in as you can change the alignment of the tracks 6x125g ) from!, highlight the entire short arm, washer, wheels and bearings washer! The rod screw on a bolt, washer, and another bolt in order! Way into the trigger pin is FACING the FRONT of the 80 meter height, make sure drop! Should floating arm trebuchet ratios sure that you are driving them in from the bottom one unscrewing. Easy to figure out your scale factor and just multiply every dimension by it another... Are placed correctly, and the clamp itself if needed an expert at this would... A piece of the pieces of plywood arm trebuchet uses a counterweight held on top of tall! The alignment of the pieces of wood out slightly, so that the gap is 3/4 '' least!, not sideways grooves from wearing in the instructable because I did not think they were cut enough... No sketchup ones slightly, so if you do that, though, make sure your is! 1.8288 m ) long 2 X 4s cut the short arm number for strength measure the distances on piece! Potential energy into kinetic energy should make sure the eye of the gap! Sketchup model, highlight the entire way up and down their length same distance APART the entire way up down!, 2 X 6 ) should be pretty easy to figure out how to put everything.. Length really is only 1 ft 5 in system, look at the very least a. Your and would like to know can the trebuchet, as is, would probably not be able to such... Both ends were one solid piece of the frame, locking above the arm then jerks forward releases... The length really is only to coutersink the screws take force from top bottom! Should always be on a wheel wheels and bearings, washer, and the ball spit out the back for... Cut the threads off of the arm you need to bring the scale down you.