Pocket Trebuchet

this trebuchet is still one of my favorite YouTube projects to date however despite having wheels it's not very portable now this is a small-scale model of my larger trebuchet that I've built when prototyping the larger trebuchet and this is a bit more portable as you can see it's quite a bit lighter quite a bit smaller and launch is a very small projectile however it's still a bit fiddly as it doesn't have a proper trigger mechanism and also trying to hold the counterweight in the right position is a bit awkward as well as that the projector doesn't go very far so what I want to try and do is make an even smaller trebuchet than this that will shoot a bit further range by using some sort of slingshot rubber to store the potential energy rather than large counterweight I designed the trebuchet to be cut on my CNC machine in two halves from 18 millimeter thick plywood so when the parts are attached together they'll make a trebuchet frame of about 36 millimeters wide and roughly 100 millimeter tall axial height mounted on top of a pistol shaped grid after a bit of sanding I installed the axles for the trigger mechanism and the two halves slotted together quite nicely the trigger mechanism was 3d printed due to the required small dimensions however these could have been cut on my CNC machine with the right cutting bits when connected by the steel push rod you can see how the mechanism will work where the rear laps will hook onto the main arm and simply pull away to launch the projectile I've been installed the main axle main arm and a length of slingshot rubber which will be used to store the potential energy and by holding the slingshot rubber with my thumb I was able to give the release mechanism a quick test with the slingshot rubber properly tied down to the frame I made a test projectile using two nuts and a piece of string this added up to the same weight as the 10 millimeter steel ball bearings I eventually want to fire so it's time for a test launch now trebuchet is occasionally misfire which causes the projectile to be launched backwards at high speed so with the trebuchet loaded and roughly aimed I tilted my head to the sides to prevent any unwanted head shots fortunately it released perfectly the next step was to make the hand grip a little more rounded and then it was time for some optimization right so I've been doing some tinkering over the past couple of days and I've made quite a few major modifications so let me bring you up to speed with what changes I've made the original main arm design had this curved section to allow the tension from the rubber to act at a large distance from the main axle when the trebuchet was loaded to create a larger talk but this only allowed for a very short piece of rubber which meant the tension throughout the release reduced significantly as the rubber got shorter I then designed this newer arm were two pulleys either side this allows the rubber to be far longer as well as always acting at a constant radius from the main axle this applies a more constant torque on the arm during launch and results in a similar release velocity as the previous rubber whilst being stretched far less this means we can always increase attention to get higher release velocities later now for probably the most difficult part of this whole build the sling the sling is often the most frustrating part of a trebuchet to build especially if you've not made one before or have lack of sewing skills like myself on my larger trebuchet I build the slings using nylon straps so together with nylon thread into a three-piece cup which perfectly fits the required projectile but to replicate this with a 10 millimeter diameter projectile is unfeasible eventually I settled on a solid sling that can be 3d printed it's simply two halves of a 3d printed Bowl with the string hinge in the middle it's made perfectly to hold the 10 millimeter ball bearing and only requires two attachment points two final modifications include a magnet to keep the projectile in position before launch so the trebuchet can be tilted without issues and finally a magnet used to store up to 10 balls inside of the grip for later use now you're probably thinking other than having a miniature trebuchet that you can hold in your hand is this useful for anything well let's put it to the test starting with an accuracy test yep the accuracy is reasonably terrible the main issue is the height and angle of projectile release but even then the projectile is released at at least 30 centimeters or one foot above the original grip height which at this short distance makes a huge difference to where you need to aim in terms of projectile velocity it releases the 4.1 gram ball bearing at sixteen point eight meters per second giving the projectile a kinetic energy of about 0.58 joules if I were to use a counterweight in place of the slingshot rubber it would be raised about 0.1 meters so assuming the trebuchet had the same 47 percent efficiency as my larger trebuchet for the same performance we'd need a counter weight of about 1.25 kilograms which considering the whole trebuchet weighs under 250 grams and a 1.25 kilogram counterweight being larger than the whole frame itself the slingshot rubber is a far better solution so what about the range the range depends a lot on what angle in the project how is released but at best it seemed to fire about 25 to 30 meters which might not seem that far by considering it's 1/10 scale of my larger trebuchet the scale range isn't that bad though it will probably struggle to win against a nerf gun especially with the next test the reload time do I even need to comment on that I'm not really sure how to conclude this project I mean where else can you say about a mini trebuchet I suppose I mainly wanted to build this thing just to sort of see what it would like in slow motion you know like a mini pistol gun with a weird trebuchet just whipping out the top it sounds really powerful at short range I think it's it's actually putting dents in my shed from where I'm only about a metre and a half away but yeah I hope you enjoyed this short little project it was good fun to build and it's definitely something to hang on my wall so if you enjoyed this video be great if you can leave a thumbs up if you're new to my channel and you're interested to see more projects similar to this then please click the subscribe down below a huge huge thanks to all of my patrons for supporting me over on patreon comm and thanks once again for watching see the next video you [Music]

Channel: Tom Stanton

Views: 360,498

Rating: 4.9659553 out of 5

Keywords: trebuchet, gravitational potential energy, kinetic energy, energy, transfer, catapult, launch, golf, physics, engineering, 3D printed, 3D print, altitude, altimeter, arduino, electronics, maths, science, potential energy, gravity, gravitational, tennis ball, geforce, acceleration, velocity, weight, high altitude, DIY, homemade, CAD, fusion, fusion360, aerodynamic, middle ages, CNC, CNC machine, CNC router

Id: IcnM-tHxlzA

Length: 8min 42sec (522 seconds)

Published: Fri Sep 06 2019

Reddit Comments

[u/DesmoLocke]

Quality content

[u/JavsGotYourNose]

The superior siege weapon

[u/ostrasized22]

And people are worried about banning assault weapons. GET THESE THINGS OFF THE STREET YESTERDAY

[u/bodhiravelle]

Because it uses stored tension as a potential energy source isn’t this technically some sort of catapult with a trebuchet release mechanism rather than a true trebuchet