On the trebuchet

In addition to my plans to build a cho-ko-nu this summer, I plan to build a small-scale trebuchet. I have some questions and I was wondering if anyone here can help me.



This image has two circles. A shows one of two wooden blocks attached to the counter-weight. I believe they are meant to interrupt the movement of the counter-weight as it makes contact with the main frame. Perhaps this sudden stop provides the arm with more momentum. The frame is protected by the angled spar.

B shows a rope and a pulley. The rope seems to pass past the first winch and is wound around the second winch and upwards toward the arm and the pulleys.

So, my questions:
Did the engineers construct this type of trebuchet so that the counter-weight would hit the frame thus increasing its range (or affecting the arc of the projectile)?

And do the two ropes, from the forked branches on the end of the frame, pass under the first winch (the one farthest from the frame)?

Edited by Zheng-ru - 26-Jun-2007 at 20:55

Hello Hugoestr

I studied gravitational potential energy. I built a Roman ballista (posted on this forum). I modified it for greater range and historical accuracy (it is a much more complex design than any trebuchet). Therefore, I will not try a simpler model because it will not interest me. I have seen many of the videos as well (thank you for your link). I also spoke to someone who helped build a large-scale trebuchet. I realize that trebuchets are usually depicted and constructed so that the counter-weight falls in between the columns of the frame. However, if you examine the image closely, you will see that the image can be interpreted to show that the wooden blocks do hit the frame. Otherwise, do you have an explanation why they are there?

Also, I know that I do not need a winch (my ballista did not need a winch or a ratchet to function as a model, but rather for completeness as a replica).

I may seem ungrateful for your help, but I do appreciate it very much.

Truly,

Zheng-ru

Edited by Zheng-ru - 26-Jun-2007 at 22:22

It seems entirely logical what you say, but then why would the engineers even construct those wooden blocks? Yes, the frame would be stressed, but perhaps not too stressed if the diagonal spars supporting the main columns are strong enough.

Oh, darn you, Zheng-ru. Now I am going to obsess about those pieces of wood

It was a joke. I find the whole thing enjoyable

Maybe the blocks are weights to adjust balance/alignment?

Originally posted by Zheng-ru I know it was a joke Hugoestr! I think you may be right Edgewaters, but how?

Don't ask me ... you're the engineer.

I'm just looking at it and thinking that the arm would have to traverse well past the perpendicular before the blocks could hit the frame, so I don't think they did that - I would guess the projectile would have left the arm before then.

The only other thing that came to mind was that they could be used to hold weights, which might be useful to align the moving parts (the arm and the counterweight). Also I figure that whatever was being used to provide weight - in such a huge counterweight container, it would probably become poorly distributed after a few shots, so you might need some separate containers on left and right to adjust the balance every so often.