A fully functional replica of the greatest medieval siege engine.
Since the day I used them in Age Of Empires II, I have loved the way trebuchets (counterweight catapults) work.
This time, I did a little research on the net and tried building a working replica: as always, out of LEGO bricks. This page describes my creation and the way it works.
Some facts
OK, so a trebuchet works by first raising a (heavy) counterweight on an arm, therefore storing energy. The projectile lies in a sling attached to the other end of the arm. When the trigger is pulled, the counterweight arm falls down and the throwing arm goes up. The sling accelerates and its pouch releases the projectile at high speed.
Take a look at this factsheet with some data regarding my LEGO treb.
Height:
27 cm (ground to axle)
Width:
14 cm
Length:
43 cm
Projectile mass:
6.5 g
Counterweight:
875 g
Mass ratio:
134:1
Throwing arm:
29 cm
Counterweight arm:
7.5 cm
Arm ratio:
1:3.87
CW hanger:
12 cm
Sling:
23 cm
Firing distane:
10 - 15 m
Scale distance: (for Technic minifig)
180 - 270 m
The counterweight consists of coins arranged inside a Technic structure. It has a value of MXP $695.
Next, meet the crew that makes this thing work.
These guys know exactly what they're doing. Following are the stages they must follow before firing this beast.
Securing the lines
When they've arrived at the scene, the first thing they must do is haul the arm down to the cocking position. So Red climbs up the throwing arm and attaches the haul down line to its tip.
Cocking the arm
Using a complex gearing mechanism and a winch, the throwing arm is lowered (and the counterweight raised) to the optimum cocking angle.
Look at the pictures: Blue is pulling on the lever conencted to the winch and then grabs the release line.
Loading the trigger
Blue is now inserting the trigger pin to lock the trebuchet in its cocked position. The haul down line can now be detached and stowed away, as it would only slow down the hurling process.
Placing the payload
Now everything is in its place; except the payload. The sling pouch is carefully placed on the trough and a projectile is placed inside.
LEGO tires and small lemons make for great ammo.
Pulling the trigger
It's Red's turn to pull the trigger. And off the payload goes. As it's hard to get a still picture of a firing trebuchet, I recommend you watch this video that explains the entire process of setting up and firing the treb.
Red