Trebuchet Physics Tutorial: Make Your Trebuchet Throw Farther
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- čas přidán 17. 03. 2014
- This is a brief tutorial on trebuchet physics and useful tricks to make your trebuchet throw farther. Much of this isn't obvious if you're new to trebuchets and I overlooked many of the key energy transfer methods when I was starting out. Hopefully, this will help you optimize your trebuchet
In this tutorial, I discuss how to use sling stalls and CW-arm stalls to your advantage. Having a basic understanding of both is necessary when designing an efficient trebuchet.
For the purposes of the tutorial, I made a tabletop hanging counterweight trebuchet. This means that the tutorial will primarily focus on Hanging Counterweight trebuchets, but the concepts also apply to floating arm trebuchets (once you have the rail gaps worked out, a floating arm trebuchet is like a hanging counterweight trebuchet with greater fall distance and a vertical CW-arm stall point... hence, it is far more forgiving...)
Also briefly mentioned is the multiple rotations trebuchet, where a link is included.... - Věda a technologie
Handwriting of an engineer right there.
This video definitely taught me a lot about how a trebuchet really works. I always thought it was just a whip effect, but this shows how and where the energy transfer occurs and it makes a lot more sense. I've been thinking about building my own trebuchet and now I know I'll be able to build a great one with this new understanding of the principles behind it.
can't be any happier by spending time watching and learning off of your videos. Please make more.
The British crazies that built a trebuchet for fun found something really amazing. Trebuchets have wheels, and the Medieval siege masters dind't remove them before firing like we assume! If you let the carriage move, the ball goes a LOT farther!
There are actually many ways to design a trebuchet. The hanging counterweight trebuchet discussed would not get much benefit from wheels, provided you release the projectile near the CW stall point. The trebuchet frame wouldn't move very far forward or backwards before then. The trade off is fall distance for efficiency, which is OK if you can load the trebuchet with massive weights like they did in the middle ages. If you are unwilling to make the trade off, wheels are the way to go.
If you are doing a something with limited weight and dimensions, a floating arm trebuchet (very similar idea to the wheeled trebuchets) is hard to beat. It doesn't sacrifice a large amount of fall distance for efficiency and it has a vertical CW stall point, making it easier to tune than a hanging counterweight trebuchet. The problem? The rail interfaces are sort of clunky.
+Rabbit on Da Moon There is quite a significant advantage to wheels with the hanging CW. When the CW reaches its stall point (and on the fixed model begins to move backwards) in a wheeled model the lighter frame and fulcrum would be moved forward instead of the heavier weight backwards thus accelerating the tip of the arm forward (basically wheels turn a fixed fulcrum trebuchet into a floating arm trebuchet)
browndyt
If the release happens reasonably close to the CW stall point (within 10 degrees of arm rotation of the stall point), the advantage is minor (the CW remains fairly still).
If the release happens long after the CW stall point, the hanging counterweight isn't doing its job and wheels would be a big benefit.
Great video! But background music make me very dificult to understood wath you where saying. I'm not an english speaker thow. TAHNKS ANYWAY!!!
This helped a ton with my science project. AWESOME!!!!!!
wow, this is incredibly helpful! It definitely helped me with a physics project of mine. I learned a lot, thanks!
The important thing that I learnt was the counterweight that drops down to give the arm its momentum actually stops the arm when it drops, something I never knew until I saw the thing actually work. I thought the arm would swing back the other way. Duh! Of course the weight now works with a dual purpose. It's neat to see these things in movies but with the camera angles you don't see this kind of stuff and you don't understand the way it works until you see the whole thing right in front of you. Thanx!!!
You better not have any problems in your life... You smart. Great Video!
One factor in performance of these trebuchets that seems entirely overlooked in modern reconstructions is that the Medieval builders appear to have made the throwing arm flexible rather than stiff [as modern makers typically do!]. In medieval images, the throwing arm is generally a group of smaller-diameter shafts bound together. I tried this and found it worked like one arm of a bow, i.e., bending first as the counter weight descended and, as the shaft moved upward, slowly accelerating the sling & projectile, and reached full height, the compressed throwing arms increasingly accelerated the projectile like a spring. The projectile left the sling faster & went farther than a stiff throwing arm allows. Think like a Medieval engineer based on what they knew.
Looks sweet! I'm going to have to build one of these.
Hi. Thanks for the video. Got here straight from the episode of Marco Polo (on Netflix), where they discuss trebuchets.
Karthikeyan M LOL me too, like i understood how it worked but just wanted to see it in more details xD
Omg me too!
Thanks man! You helped me with my science project!
Ha Ha same
Great video! I use it with my physics classes. Videos are hard to follow, very grainy. It would be great if you would redo it using most recent generation iPhone or Samsung S10 or S10+ with super slo-mo.
Crusade anyone?
if the most usual fulcrum ratio is 1:4, how about the usual length of the counterweight line, and of the sling itself - are there optimal ratios of these as well?
I would love you to help me with surf casting fishing rod theory. I bet you could tell me exactly what to try to achieve
Good stuff and well presented! All the fine folks with “suggestions” in the comments are free to make their own, better, video (not).
Tnq for giving me. The easiest solution
JUST BRILLIANT ♥♥🏆🏆
Hello everyone that is building a trebuchet for their project, I am too. Good luck!
My trebuchet is 4ft tall
Thank you
Thank
i tried to make a formula for counterweight stall point and i came up with this:
Lsa = short arm length
Lcw = counterweight length
y = starting angle
z = stall point angle
Stall point: Lsa x Cos(y) = Lsa x Cos(z) + Lcw x Cos(z)
and you can solve for either Lcw if you have the desired stall point angle, or you can solve for the stall point angle if you have the desired counterweight length.
I dont have anyway to experimentally check this but the math seems right to me. tell me what you think. thanks
It's a decent approximation, assuming minimalhorizontal motion. The CW does move forward a little, though.
ok thanks. i just wanted to make a calculation for the counterweight length so i have a good basis for adjusting it.
how do you attach the ammo?
I'm fairly new to trebuchets. When does the sling release the load? Is it during the stall he mentioned.
Sleepy Jean you should tune it to release at the stall point. It's the most effecient energy transfer
How many times you try to make good trebuchet ?
Building a medium scale trebuchet at the moment. If the length of the sling controls the stall point then what does the angle of the pin that the loose end of the sling attaches to control?
The stall point is when most of the energy is in the projectile (a good time to release). The pin angle determines when you actually release. Usually, you have to fire a few shots to find a good pin angle.
MilleniumHare Thanks. One more quick question. I also plan on tapering the throwing arm (a 2x4) to reduce the inertia. Any tips on where to begin the taper and how much to taper by the end?
Unfortunately, I don't have any tips. Do something that seems reasonable. If the arm is too big and clunky, shave some weight off. If it looks like it's going to break in two, you've gone too far.
Also, make sure that whatever's going on at your fulcrum isn't going to weaken your arm.
what software/program did you use to make projectile in 2:45 ?
That was done using C (to get the coordinates vs time) and adobe flash (vector animation). The result is pretty, but it's a tedious way of doing things. If you have matlab, you can do the whole thing there and use Matlab's graphics library to spit the movie file out (much easier, but not as pretty... Note: A lot of people hate Matlab, but the language is actually very well suited to numerical simulations.).
The numerical simulation itself ( use C or Matlab) was done by finding the Euler-Lagrange equations of the system and numerically solving them (I used a 4th order Runge-Kutta Method, which is probably way overkill. en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods).
While it's nice to have these tools, you can actually draw a lot of physical intuition from things you learn in high school or 1st year of college physics. While it's not said in the video, you can justify things like the CW-arm stall point using free-body diagrams.
MilleniumHare
Awesome. Thank you for the info. I'm currently building one ( sketch it using Solidworks which I have experience with) but the stimulation you did is just rocks. Thanks again
Now, put the trebuchet back on it's wheels like it's supposed to be and explain why it works a LOT better.
A floating arm trebuchet (FAT) doesnt need wheels, the F2K is hard to beat.
So, this is the same physics being used here?
www.seaangler.co.uk/fishing-tips/casting/articles/how-to-beach-cast-part-1
Note the rod tip almost touch the ground at the start, the line is layed out from the tip back toward the caster and loads the rod from the start flying, arching out and rolling over the tip.
This is different then the line layed out straight off the tip, the rod dragging it off the sand in a straight line, up and over, which is what you commonly see a lot in surf fishing. It would seem this method loses a lot of loading and speed.
180-200 plus yards is quite the accomplishment.
what branch of physics studies these things? can you recommend an introductory book?
Pier Bover Classical Mechanics: A decent understanding of force and torque (being able to do free body diagrams can give you an idea why there is a CW-Arm stall point) and understanding conservation of energy will give you a lot of intuition on these types of systems. My gut reaction is Haliday& Resnick Vol 1 ($31 used... Absurdly expensive new). The Feynman lectures are also a possibility (Vol 1 is surprisingly affordable), but he is very verbose (possibly bogging down first time readers). If you want to do a simulation and have a decent math background (differential equations and linear algebra), read several sections of Landau-Lifshitz Volume 1 after the intro textbook (teach you how to do eqs of motion from principle of least action... ~$15) and then read a numerical methods book.
the ideal proportion of long arm to short arm is 1/3
False. It all depends on what you intend to throw, and how far. A 3:1 ratio has power, but not much speed. A 7:1 beam ratio has speed, but not much power. It's all about gear ratios, and purpose built...
music too loud. can't hear you
You sound like T.V. from Adventure TIme :)
good info, too bad the audio sucks
Doesn't help solve the fact mine won't release
Gosh! You have so much information to offer but somehow it doesn't seem to come across as well as maybe it should. Tremendous effort but you might ponder getting some assistance with the presentation as you are doing yourself injustice. Thanks. Best of luck.
Hi Millenium, you were linked on reddit.com/r/physics
Can you do a video on how compound bows work?
I am no expert at making bows, but here's what I know about bow physics:
1. When firing, the straightening of the bow string is an incredibly efficient energy transfer mechanism. So, unlike with trebuchets, most of the efficiency concerns are already taken care of with bows.
2. Most of the curving with recurve bows and the wheels on compound bows deals with the force-draw length curves. Humans can only handle a certain maximum draw weight. Recurve bows and compound bows attempt to maximize the energy stored for a given maximum draw weight. To do this, both designs have the force rise quickly and flatten out after a certain draw length (larger area underneath -> larger energy).
Note: The force on compound bows actually peaks and decreases, allowing the shooter to hold a drawn compound bow fairly easily.
3. Adding stabilizer rods increases the moment of inertia of the bow, stabilizing it... That's useful if you're into target shooting.
4. Penetration depth (see newton's method): If you want to down something big or heavily armored, use a heavy arrow. What did the Manchu bowman, the Samurai, and the English longbowman have in common? They all fired really heavy arrows and they dealt with armored targets... In contrast, the Saracens fired much lighter flight arrows, which traveled really far, but couldn't pierce the cloth armor of the crusaders.
5. The thin and flat profile of the AFB is better than the longbow's D profile, which is hell on the materials...
...and that's all I know....
MilleniumHare
Just wondering, what does AFB stand for? I'm guessing the B is for bow...
CaptainFluffy6644 American Flat Bow
What
Easy nerd, I just need the dimensions
It would be much easier to follow the spoken word without the unnecessary noise behind it
Great physics and video. Narration, not so much. Please speak more loudly. And thanks!
Please next time cut the annoying music. It does nothing useful.
how about you stop whining? its been seven years...
boring voice cool tutorial x)
Good tutorial, but this dude could suck all the fun out of a wake
Nobody's perfect.
Bad handwriting and me too
You should have recorded this in your own voice instead of using text-to-speech
Forget the scientific equation bullshit and just get to the point.
Your losing me...