Knight's Trebuchet - a simple, quick, Scout trebuchet

I designed this simple trebuchet  as a more stable, robust small trebuchet. The two opposite side frames are braced against each other so it doesn't need guy lines, which is the main problem with the older trebuchet design on Ropes and Poles. The Troop Scouters of the recent Gauteng Scout Wood Badge course at Arrowe Park tested it out and verified that it works (two of the patrols promptly ganged up on the third to send a shower of over-ripe tomatoes across to them). The theme of the Wood Badge weekend was 'the Knights of Gauteng' so this is the Knight's Trebuchet.

Two patrols used a traction rope as per the drawing below, while the third patrol used a rubber tube, pictured above. All three worked successfully.

Here are the sequence drawings for assembling this trebuchet:

1. Build one 'A frame'- make sure there is enough space at the top for the throwing arm to rest.

2. Tie the base lashings of the second (yellow) 'A frame'/triangle and attach it to the first A frame

3. Lash the top of the yellow A-frame, making sure the crossing lines up with the green A-frame

4. Lash the two base poles on to the two frames.

5. Attach the throwing arm, which is lashed onto it's axle. Rest the axle in the forks on the top of the a frames, and 'mouse' the top of the fork to prevent the arm jumping out.




This trebuchet was tested with and without a sling.

The SketchUp model is available for download HERE.

Two Scout Trebuchets

One year ago today I posted the first project on Ropes and Poles- a small trebuchet (you can get the SketchUp model here).


This week I received photographs of two trebuchets built by Scout troops. The first is built by 9th Irene Scout troop from Pretoria. This trebuchet has a throwing arm around 10m long, and a counterweight (made from barrels filled with water) of about 50kg. It throws projectiles 60m and was built at Cornwall Hill College's Carnival. You can see more photos and some videos at the Troop website.

The second trebuchet is from Montevideo in Uruguay. The 45th Scout Group 'Juan de Cordoba' won the 'Bauen' pioneering competition with this 3m trebuchet that throws a basketball 120m (that's more than the length of a football field). There are some photos of the construction here,they are worth taking a look at- this trebuchet won the 'best trebuchet' prize and also had the best distance and won a 'best technique' award (apparently this design is based on the 3m trebuchet I posted here- if so it is a great improvement, the best we managed is around 30 metres)

Many people who visit Ropes and Poles have searched for 'trebuchet sling' and the best way I can recommend to understand how a sling works is to watch a trebuchet in action- like this video from 'Juan de Cordoba' Troop's trebuchet:

William Gurstelle was also written a a good book on catapults, trebuchets and other siege weapons)

Trebuchet Slings- release points

My very first post to this blog was a trebuchet, and it still attracts a lot of traffic. Our troop has learnt that the difficulty of a trebuchet isn't in the construction, but in the fine adjustment of the sling to get the right release point. The drawing above shows how the sling whips around, and then SLIDES OFF THE END OF THE TREBUCHET ARM. You want the projectile (water balloon, rotten potato, flour bomb etc.) to fly out of the trebuchet when the angle of the arm is close to 45 degrees. A quote from my earlier posting about the sling:

The crucial component here is the sling- made from a diamond of leather stitched to two cords. One end of the sling is tied to the end of the throwing arm, the other has a loop tied around it which is slipped over the throwing arm. When you release the trebuchet, the arm swings around and flicks the sling around.

This photograph captures a moment just after the arm has reached the end of it's arc- the lst frame of the drawing above. This release was too early, you can see that the balloon (small green object to the upper right of the image) is directly above the trebuchet, instead of flying forwards. This image also shows the sling clearly- in this case made from an old leather handbag I persuaded my mother to donate to this worthy cause.

This small trebuchet is a good design to learn about siege engines with, being lightweight and easy to load. For more exotic designs, I can recommend William Gurstelle's Trebuchet book at Amazon.com.

Remember that siege engines can be dangerous. Ensure that the field you are working in has been cleared of people. Clear the areas immediately in front of AND BEHIND your trebuchet before firing. Note that building a trebuchet may be illegal in your area- investigate the law BEFORE building one.

Trebuchet

 UPDATE: download this as a SketchUp model here.

This Trebuchet is a small (10ft/3m throwing arm) version that uses a bucket filled with bricks/stones for the counterweight. The crucial component here is the sling- made from a diamond of leather stitched to two cords. One end of the sling is tied to the end of the throwing arm, the other has a loop tied around it which is slipped over the throwing arm. When you release the trebuchet, the arm swings around and flicks the sling around. At some point, the loop slides of the end of the arm, and the object you are throwing (rubber chicken, rotten lettuce,water balloon, tennis ball etc..) is released. Not much else to say that is not obvous from the picture, besides this: make sure that your entire supporting structure is very solidly braced or guyed, otherwise you may find the entire thing collapsing after a few shots. Also, if the sling releases early, the projectile can either go straight up, or backwards, so make sure that you have cleared a safe area behind and in front of your position. anything to the left or right is generally safe.

WARNING
This is a projectile weapon, with a potential range of 100m/300ft. DO NOT aim this at anything you do not want to hit. DO NOT load any hard objects (bricks etc.) into it. REMEMBER your cone of danger extends in front of and behind your trebuchet

Catapults, Trebuchets and Ballistas

Scout constructed siege engines- catapults, trebuchets etc.

 

Simple scout trebuchet

 

Release timing - optimum sling release point on a trebuchet

William Gurstelle's Trebuchet book at Amazon.com.

 

Ballistic weapons are potentially dangerous. Some of these projects can fire projectiles hundreds of feet. Ensure that safety procedures are followed at all times- make sure your firing range is clear and that the projectiles used are not likely to cause damage (water balloons or flour bombs are recommended)