The science of trebuchets...
Discussion
Anyone know any thing about trebuchets?
I built one with my son over half term and it releases too late so the projectile smacks into the ground about 6m away. The arm is about 1.5m long and the weight is a bit of a mix (bit of an old boat engine, an axe head and a lump hammer...) that weighs about 2.5kg. I didn't use plans, which might have been an error.
I built one with my son over half term and it releases too late so the projectile smacks into the ground about 6m away. The arm is about 1.5m long and the weight is a bit of a mix (bit of an old boat engine, an axe head and a lump hammer...) that weighs about 2.5kg. I didn't use plans, which might have been an error.
Edited by Bill on Sunday 18th February 17:16
https://youtu.be/Dp7XoUrqMQA
Don't know, but filmed this at Corfe Castle this week in 2x slow mo... 14lbs of football was the projectile, landed at the top of the "green" grass bank!
Don't know, but filmed this at Corfe Castle this week in 2x slow mo... 14lbs of football was the projectile, landed at the top of the "green" grass bank!
Lynchie999 said:
https://youtu.be/Dp7XoUrqMQA
Don't know, but filmed this at Corfe Castle this week in 2x slow mo... 14lbs of football was the projectile, landed at the top of the "green" grass bank!
That's what inspired it, we live just down the road.Don't know, but filmed this at Corfe Castle this week in 2x slow mo... 14lbs of football was the projectile, landed at the top of the "green" grass bank!
JonChalk said:
It sounds like it's slowly down too late in the swing. Or maybe the rope is too long.
In other words, it's still trying to accelerate the missile right through it's arc, until it's too late a release.
We've made a better sling since that picture which is shorter. If it's much longer than the pivot point it doesn't accelerate the projectile along the base and just lifts it.In other words, it's still trying to accelerate the missile right through it's arc, until it's too late a release.
I'm wondering if the uprights need to be taller.
227bhp said:
That's cheating! But more effective than my search, thanks. It looks like it's the pin angle. Shame it's dark now. 
Bill said:
227bhp said:
That's cheating! But more effective than my search, thanks. It looks like it's the pin angle. Shame it's dark now. I built one
There are some medieval pictures on the internet and there is also a mathematical study of the optimum dimensions.
For the best results you need:
main pivot to where the weight hangs = 1 unit of length
main pivot to where the sling attaches = 4 units of length
length of sling = 4 units of length
weight hanging point to centre of weight = 1 unit of length
Wheels on the carriage
The wheels and the articulated weight help the weight to fall vertically.
You will need to adjust the sling release to optimise the release timing.
There are some medieval pictures on the internet and there is also a mathematical study of the optimum dimensions.
For the best results you need:
main pivot to where the weight hangs = 1 unit of length
main pivot to where the sling attaches = 4 units of length
length of sling = 4 units of length
weight hanging point to centre of weight = 1 unit of length
Wheels on the carriage
The wheels and the articulated weight help the weight to fall vertically.
You will need to adjust the sling release to optimise the release timing.
Gassing Station | Science! | Top of Page | What's New | My Stuff