[Loch-ruadh] Trebuchet project(long)

[Adam Harrison]

Greetings Loch Ruadh,

Now war is behind us and the spring sememster of
school is coming to a close.  As we prepare for
Lugnasad, I believe we should also complete a project
we discussed well over a year ago.  Last year it was
decided that we would build a trebuchet for combat
use. I think it is high time we actually build one.

I have been researching trebuchets since the beginning
of my SCA career.  It is my belief that the best
trebuchet for SCA purposes is a hanging counterweight
trebuchet with a 12 ft throwing arm.  This will put
the shoulder of the trebuchet at approximately 6.5'.

I have secured a 16' long arm made from 3 2x8's.  This
will be cut down, tapered, and reinforced and the end
result will be our throwing arm.

There are two basic designs for the framework to
support the throwing arm, and both have their merits.
Now is the time we need to decide which of these
frames we will use.  It has been proven that both work
well, so performance need not be an issue in choosing
the base and uprights.  Cost, time, ease of
construction, and ease of assembly/takedown should be
looked at.  I have drawn up plans for both type of
bases, so we have basic designs to go from.

The next issue we need to discuss is how the frame
will be assembled.  I want to have the trebuchet look
as period as possible, but at the same time
incorporating as many mundane safety factors as
possible.  To accomplish this I have
devised/researched two methods.  One involves using
several smaller pieces of wood laminated together to
simulate a large piece of wood.  The other involves
large pieces of wood that have been Dado cut to fit
together.  Both assemblies require precision cuts in
order to work correctly and look good.  In both
methods, bolts in countersunk holes will secure the
structure, and dowel pegs will be used to disguise the
bolts.  due to the massive forces involved, I am
confident that nothing less than 4"x6" is required for
each frame piece.  Steel bracing must be used in some
sections to provide the required amount of strength.
Unfortunately, these must be placed in a way such that
we cannot hide the mudane bolts that lock them in
place.  I am sure that more issues of frame
construction will come up over time, but these are
enough to get us started.

Next we need to discuss projectiles.  The design I am
shooting for will be able to throw all projectiles to
the maximum distance(100 yds at Gulf War).  Trebuchets
have 4 basic types of ammo:  1Lb cloth/foam rocks,
Tennis ball clusters, single tennis balls, and Novelty
ammo(cows, anvils, harpsicords, Trojan bunny rabbits,
etc).  If all goes as planned, the trebuchet will
throw 5 1lb rocks, 8-10 tennis ball clusters, 25-30
single TBs, or one novelty ammo to the maximum range
each shot.  Loading more rocks into the sling will
produce shorter ranges, but more stuff will be flying
through the air.

Slings should be discussed next.  I am designing this
trebuchet to have interchangeable slings to vary the
range and height of the shot.  in some situations we
want a very high arc with a short range(such as
shooting the area in front of the gate or sally port
at Gulf Wars).  In other situations we want a
trebuchet with a low arc and very long range, like
shooting fighters coming over the wall of the fort.
We also want a combination of the two so we can shoot
to maximum range with a relatively high arc.  This
will allow us to pepper the enemy reserves before they
assault the fort.  We will also need different sling
basket sizes to accomodate the various types and
amounts of ammo.

Next on the agenda is the counterweight.  I am
shooting for a weight of 300-450lbs and have designed
a box that will meet the requirements if filled with
lead(easily attainable as scrap or scuba weights).
Also a framework will need to be built to hoist the
counterweight into position on the throwing arm.

We must also devise a way of locking the machine.  I
have not yet figured out a completely reliable way of
doing this, but there are several plans in the
works...

The final thing that needs to be discussed is
transportation.  We will need a substantial amount of
space to carry this engine.  We will also need some
sort of period looking wagon to carry the pieces of
the engine around at events.


So as to not clutter the Loch Ruadh email list with
this discussion, I have created a Yahoogroup
specifically for this purpose.  It can be emailed at
LR-Treb-Project at yahoo.com

It's web address is
http://groups.yahoo.com/groups/LR-Treb-Project

Go to this address and follow the instructions to
subscribe to the list or send an email to
LR-Treb-Project-subscribe at yahoogroups.com


With a combined effort, we can make this the best
looking trebuchet on the field.

-Ld Bjorn inn Kvensami
Siege Marshal of Loch Ruadh and Elfsea


__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - buy the things you want at great prices
http://auctions.yahoo.com/