Monday, 4 June 2012

Large scale Test trebuchet.

In an attempt to learn a bit more, overcome any design faults etc  before I try to build a small scale working version ( and have a bit of fun) I´ve built a large scale working trebuchet.
I´ve learnt a couple of things. The counter weight. It needs to be quite heavy...my first attempt I filled it with stones like they would have, but it threw very slowly, so I re-filled it with lead. I could also have moved the counterweight further away from the fulcrum point, but as there is only a couple of cm´s between underside and the running board, especially when the counterweight swings back and forwards after firing,  this was impossible. The only solution to increase the distance of the counterweight along the arm would be to increase the height of the middle section..which is now too late.
Also..the range can be altered by lengthening or shortening the strings to the sling as does slightly altering the angle of the pin that the loose line is attached to. Bend it a slight bit more away from the direction of throw and it increases the release time..which alters the flight..making it flatter, less of a high arc.
Set up as it is at the moment,  it throws a 4-5 cm´ds wide stone 20-25 meters.
Not far considering it´s size, but this is due to the positioning of the fulcrum and the weight of the counterweight,
No claims to historical accuracy....it´s missing a lot of supports and the actual body length is way to short at the front. I also left any winding gear off..it just seemed (at the moment) impracticle.
The axles for the arm and the counter weight proved difficult. I used metal tubes inserted into the arm, then other slightly longer thinner tubes held in place with washers were pushed through them. The bolts were then inserted. This made sure that no wood was touching moving metal and decreased the friction, which would have slowed the firing action down.
The trigger. I added this type of trigger, one using a pull cord after the one that was more historcally accurate, a pin that was knocked out, got me a whack on the ear from the arm releasing.

A couple of mini videos showing it in action




Hello to Marzio from Fog´s Soldiers. blog. In his own words " Fog' s Soldiers is a professional miniature painting service and a producer of high quality, handcrafted, scenery and model trains services."
Hello to Punkreaper from G+
Hello to Ralph Ashdown..I´ve seen your name mentioned on sean´s Blog..but no link from here?

Mike Whitaker has Just given a link to a site that works out the statistics of a trebuchet for you....
Virtual Trebuchet    Excellent..just what I was looking for. :-D