		|==============================|
		|---------SIEGELORD VII--------|
		|==============================|

		-by Paul Sountsov (SiegeLord)

Table Of Contents:

I: Contents of the ZipFile

II: General Instructions

III: Theoretical Considerations

IV: Some Specific Problems

V: Other Thoughts

VI: Legalese

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I: Contents of the ZipFile:

-3 Principal views of the catapult (Front.png, Side.png, Top.png)
-Detailed view of the Release Mechanism (Release.png)
-Detailed view of the trigger system (Trigger.png)
-3 Reference views (View1.png, View2.png, View3.png)
-2 "Down-The-Barrel" views (DTBf.png, DTBb.png)
-3d Rendering (Render.tga)
-This file (ReadMe.txt)

II: General Instructions

Congratulations! You have just received the plans of the latest(by number) of the SiegeLord series catapults. This particular design was seen only at 2006 nationals competition.

This design was originially thought up during the Massachussets state tournament of 2004, but was not built for various reasons until 2006. It is of a cannon design, due to the fact that it contains various enclosures for the projectile and in general resembling a cannon barrel. This design uses an improved release mechanism of the previous SiegeLords and the Hatra Ballista.

As the last of the SiegeLors designed by me it represented the pinnacle
of SO cannon technology. Unfortunately this is a WKFD(Well Known Failed Design) and represented the error of design commited with the construction of SiegeLords III, VI and VII. Its performance near the lower counterweights is very good, easily in the top 5% in the nation, however its efficiency takes a sharp fall as the counterweights increase in mass, making it completely useless in any competition higher that reginals. It is however an interesting excersise in getting it to work in the first place, and as such its construction still represents a useful project.

The construction itself is relatively simple. Choice of wood is up to you, I used pine quite succesfully, but harder woods like poplar will work even better. Always use screws with predrilled holes. Avoid glue unless you are convinced that this design will be your final, add more screws if you feel that it is too wobbly. You will note that on all of the blueprints I have neglected to put any locations of the screws. Use your own judgement in screw placement, aethetics do not matter much - all that matters is that they hold.

The blueprints themselves were generated from the SiegeLord VII itself, as I still retain the catapult. You will note that not every possible dimension is made in the blueprints, and that is deliberate. The final form of the SLVII was made both by the design considerations and the availability of raw materials, as such some connections may seem wasteful and arbitrary to you. And they are, but they represent the materials I had to work with. As such all of the designated measurements are the ones that are critical for the design's workings. All of the measurements omitted are irrelevant and will vary depending on the individuals who are constructing it.

III: Theoretical Considerations

This cannon is a 100% theoretical efficiency device. The force diagram in the input direction is identical to the force diagram in the release direction. The physics of this design are relatively simple, they can be readily approached with simple energy conservation tricks. By design all of the energy of the counterweight is transfered to the rubber bands, and all of that energy is transfered to the projectile. Obviously in real world there is friction and also the rubber bands the pouch are not massless, so any residual motion in them is considered lost and is not transfered to the projectile. Still given light materials in both this can be reduced quite a bit.

IV: Some Specific Problems

If constructed well, and if checked thoroughly before every launch SLVII launches perfectly and consistently. However flukes aside there are some permanent issues with this design.

First, rubber bands do not like to contract rapidly. Thus the maximum range stops increasing after a certain point, and no addition of rubber bands will increase the range any more. Unfortunately this happens at around 1.5 kg for this design, resulting in a maximum range of 25 meters with a golfball. This could possibly be alleviated by the use of metal springs, but their weight could be of a hindrance, and no spring I know can stretch the required ammount (400% at least).

Second, the plague of all of the ballistas and the SiegeLords is the stretchiness of the string. I used ice fishing line for most of my designs and it stretched quite a bit. Since any sretching in the string between the release cart and the ring for the counterweight never gets transfered to the projectile it is especially bad in terms of efficiency. Also the release mechanism does not travel the same distance with the different counterweights due to this stretching. If it triggers fine with 1kg it will not trigger at all with 3kg, since the string will stretch and the release mechanism will never hit the launch bar. I have recently found some fishing line of the SpiderWire brand that does not stretch as much, but it has low tensile strength. Also I have found some sources of Kevlar fiber on the internet but I have never took advantage of them, so I am not sure of their strength etc.

V: Other Thoughts

While I will be very pleased if anyone does indeed build this device, I warn you that this device is TERRIBLE and I see NO improvement that can be done with this specific configuration. Other configurations exist, but I consider the question of feasibility of cannons in SO to be answered. 

IT IS NOT FEASIBLE.

I shall be building one more ballista(namely SiegeLord I) during this summer(2006). So if you feel that you will learn a significant ammount by buiding SLVII do so, but there is a significant chance that you will waste your time, as determined by my testing of it and its brethren.

I purposely left out some of the more specific instructions on its construction
as to stimulate your brains, and also I may have forgot some stuff. In any case
if you are stumped and/or curious at the construction feel free to contact me
through a PM at www.scioly.org (SiegeLord), or through email @ psuntsov@hotmail.com.

VI: Legalese

In the Event Rules of the 2006 Coaches Manual for Division C is says on page 3:

"Team members are expected to be the builders of all the devices used in the
events."

Thus it is perfectly legal to use this design verbatim in the competition
since you will be the actual builders of it. The fact that you will have
to design the components I have omitted reinforces that fact even more.

These plans are now considered your property and you may use in any way you
wish for both Science Olympiad and for profit or any other way you may choose.
I will require no mention of my name to be located on its manifestations, but
I will appreciate if the true source of the design is aknowledged during 
the inevitable questioning. I will doubly appreciate if you write its name on its
side - "SiegeLord VII". Regardless of the way you end up using it I wish you
the best of luck with it, and thanks for showing interest in my designs.