The Treb Files - Grey Company's Trebuchets

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The Treb Files

Part 5:

Jake

Name:	Jake
Class:	Single Post Traction Trebuchet
Size:	Throwing arm 1.90m, hauling arm 0.45m, axle approx 2.5m high
Power Unit:	one or two humans using one or both hands.
Projectiles:	Tennis balls, juggling balls, stones slightly heavier than those for poleslings.
Range:	60m for tennis balls, approx 100m with juggling balls, further for stones.
Based upon:	Mostly based upon the illustrations in the Chronicle of Petrus de Eboli and made to be light, simple and portable (and a prototype for something bigger).
Status:	in active use.

Jake began as a modest project to make a small and not particularly historic "minimal" traction treb (it never acquired the rake-like spreader seen on the pulling end of bigger machines) but, since the effort was going to be put in anyway, it changed into an experiment to test a few ideas about single-upright traction trebuchets.

We had seen our friend Sven's ill-fated attempt to build a heavy one some time earlier. Thinking about this and comparing it to the thin whippy-looking machine shown in the Chronicles of Petrus de Eboli, I wondered whether the answer might be to make the machine lighter, more flexible and to take as much impact as possible out of stopping the beam by using the pullers' ropes as brakes. Jake is the result.

Why "Jake"?.. well I suspect you have to be Australian (or British) and familiar with Rolf Harris to understand, but it's something to do with the frame's pegged construction.
Plans are already in place for making at least one and possibly two larger relatives for Jake.

John, Russell and Jake.... photo by Dick Stein

Jake hurls a stone. This shot was made on Jake's first day out when he was shown to the rest of Grey Co during an archery session at our friends' farm. No tennis balls or juggling bean-bags here... this projectile is an egg-sized stone and is moving down-range fast. Not bad for a very small and basic "minimal treb."


	On the same first day out, we experimented with using the classic crew arrangement of pulling crew and sling handler. It's a bit of a bend for Dick to work the sling, but even with this little machine the effect was noticeable - the projectile "popping" from Dick's hand with the beam slightly flexed and the pullers already coordinated and up to power. (It does give you a slight worry about the load you are placing on the beam though...)


	Here (left and below) is a pair of photos showing Jake's construction, in particular the top frame. This one shows the tapered end of the single base support pole pushed up into conical holes in the horizontal timbers of the frame. Having settled on a historic design, I tried to work out the simplest way of making it all fit together (and be able to pull it apart again easily) while making it strong enough for normal treb use. The solution was, surprisingly enough, to use medieval joinery on a medieval machine. This may be the beginning of a trend in Grey Co machines...


	This is a close-up of Jake's frame construction. The side frame timbers are fixed in place with wedged tenons. The axle (fixed permanently to the beam) has hand-carved ends and fits through holes in the side frames. Jake being so small, we didn't bother to grease the bearing surfaces.


	Jake, when pulled down into its parts, is very compact. Here I'm carrying the beam and frame pieces. The only other part is the single pole support, not shown here - although we usually also make use of a pointed length of pipe hammered into the ground to give a firm anchorage for the bottom end of the upright and to keep Jake standing when not in use. (In the background you can see a couple of Grey Co's female archers peppering a cardboard cut-out of Ricky Martin with arrows. No comment.)


	Jake in action at Past Times 2000, an interclub gathering sponsored by Grey Co. Here we are throwing a tennis ball, although the range is still reasonable. With a slightly heavier and smaller projectile (like soft juggling balls) we were pumping out distances of around 80-100m. Jake did very well at Past Times where its simplicity and efficiency might have actually inspired some members of other groups to try their hands at trebuchets. We shall see...


	Jake stands at rest while Magog slings a shot. Something we learned from Quasimodo the old traction trebuchet, Jake has a short length of rope that joins the pulling end of the beam to the upright. The rope holds the beam in the position shown by this photo when Jake is unattended, but it is also a safety rope - there for the unlikely event that it needs to stop a run-away beam from hitting the pullers. Less important with Jake, it becomes a real reassurance with a large machine. (you can see the rope here.)

John lies sprawled on the sheep-dropping infested ground with a broken Jake beside him.... photo by Kate

Why do we always break something on every machine's first session? In this photo John lies sprawled on the sheep-dropping strewn ground with a slightly broken Jake beside him...

I've included this photo as a safety warning. Unnoticed by us, the dowelling used for Jake's first upright was a very flawed bit of wood - brittle and with an odd grain.
John, trying a two-hand-one-man technique, hauled with a larger forward motion than usual and the wood broke.

Grey Co members rushed forward to offer their usual brand of sympathy - ie they took photos and added props (such as the arrow) to "improve" the pose.

The replacement upright (later used all through Past Times) was checked carefully before being put into service, and any larger machines we make in future are likely to have a safety rope lashed along the length of the upright.

Last Edited: November 2000

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