Siege Storing Energy in a Machine

Treatises Engines Of War Engineering Battles Spare Parts Plunder
Storing Energy in a Machine      
Share this page

Siege engines that store energy and use a throwing arm typically need some sort of winch. There are many forms of winch, and they are actually somewhat uninteresting. Of greater interest is how to use them most effectively. Tricks for tall trebuchets can greatly enhance cocking time. Often, an in line trigger is quite useful, though we haven't used one.


A boat trailer winch is a mighty fine thing if you are in a hurry. You can get them at any marine hardware store, they are cheap, and can handle vast loads. Be very careful when picking out a winch. They are typically rated in terms of how big a boat you can haul out of the water with it. If a winch can haul a 5000 lb boat out of the water, it cannot handle a 5000 lb torsion load. This is because the winch isn't suspending the boat in the air. Most of the weight is on the trailer wheels, or floating in the water.

This image is from Juggernaut 2.

You could also roll your own winch with a gear and pawl. This image from Baby Treb shows a gear and pawl scavenged from U-Mass. I don't know what it's previous life purpose was. The dowel it is attached to runs through the frame of the machine, and a rope wraps around it as the dowel is turned.

You could also just rely on manly prowess as does Roger here pulling back on Ballista Jr. We had lots of issues with Ballista Jr, but getting the bowstring pulled back wasn't one of them (Unless you were Kevin, and you were holding the bowstring in place while someone else tried to use our totally sucky trigger.)

Trebuchet Adjusting Linkage

On Juggernaut 2 we had a cable that ran down the length of the arm. Over this cable we had a pulley with a hook. We attached the winch to the hook, and as the arm came down, the pulley would move from near the fulcrum, to the other end of the arm. When the arm is vertical, we had little leverage, but this is ok since the counterweight is being pulled left to right more than up and down. As the arm came down, and the pulley slid out toward the hook, we gained more leverage. This is also when you need the most leverage as the wieght started to tilt itself.

In the below image sequence, you can see how the pulley slowly moves from one end of the arm to the other.

Onager Winch

We recycled the Juggernaut 2 winch on Onager Jr. In order to get enough leverage, we added a 2-1 pulley system. We hid the winch inside the frame so it wouldn't get in the way while traveling. A pulley at the base of the trigger is then used to keep the line straight while feeding into the winch.

The observant may notice that the handle has moved on this winch. It is fortunate that most boat winches can have their gear system reversed or transposed with ease.

Here you can see the additional pulley attached to the arm.

[an error occurred while processing this directive]
Buy a Trebuchet
Buy a Ballista
In The News
Contact Us
Engines Of War
Micro Treb
Baby Trebuchet
Treb Jr
Juggernaut 2
Pumpkin Putter
Baby Ballista
Ballista Jr
Mista Ballista
Baby Hatra Ballista
Hatra Jr
Baby Onager
Onager Jr
Cardan Treb
Scissor Treb
Vacuum Bazooka
Air Cannon Jr
Extreme Chunk 2018
Extreme Chunk 2017
Extreme Chunk 2016
Extreme Chunk 2015
Punkin Chunk 2013
Higgins Siege The Day 2013
Punkin Chunk 2012
Punkin Chunk 2011
Punkin Chunk 2010
MathWorks 2010
Punkin Chunk 2009
Zukapult 2009
History Chunk 2009
Punkin Chunk 2008
Zukapult 2008
Punkin Chunk 2007
Flying Chunk 2007
Punkin Chunk 2006
Zukapult 2006
History Chunk 2006
Punkin Chunk 2005
Zukapult 2005
Punkin Chunk 2004
Punkin Chunk 2003
Bennington HS 2002
Punkin Chunk 2002
Mohonk 2002
Mt. Snow 2002
Bennington HS 2001
Punkin Chunk 2001
Busti Hurl 2001
History Chunk 2001
Punkin Chunk 2000
Punkin Chunk 1999
Punkin Chunk 1998
Spare Parts
Random Picture
All Videos
Seuss Trebuchet
Seuss Onager
Night Before Chunk
Pillsbury Cartoons
Dave Gets Married
Roger Gets Married
Geek Calculator
Browser Hurling
Catapult Kits
Catapult Plans
Contact: Team Tormentum
Copyright © 2000-2022 Eric M. Ludlam All rights reserved.
Twas' brillig, and the slithy toves did gyre and gimble in the wabe...
Last Modified: 05/10/09