Page 42 - 15 Dangerously Mad Projects for the Evil Genius

Chapter 2 ■ Trebuchet 23

So: ■ Decrease the weight of the throwing arm by

E 1 mdg reducing the amount of wood at the sling-end,
2 or cutting it into a wedge shape.
The tennis ball weighs about 60 g and a good ■ Vary the pin angle.
throw will send it 25m. Just in terms of increasing the range, without

E ½ * 0.06 * 25 * 9.8 changing the efficiency, increasing the weight is an
7.35 joules easy win. You could use a bigger container, or use
gym weights. You will, however, quickly need a
From this, we can calculate the efficiency of our
stronger frame and throwing arm as you increase
trebuchet at 7.35/40 18%.
the weight.
This figure of 18% neglects the fact that the
tennis ball has to travel through air and is probably
not launched at the optimum angle. So, the real Summary
figure is probably closer to 25%.
If you want to see what happens when you scale
This does not sound great, but actually is quite
up a design like this, take a look at YouTube. It
typical for a homemade trebuchet. These very
shows some truly enormous trebuchets, which can
rarely exceed 30%.
throw people, pianos, barrels of flaming gasoline,
The following are a few things you can do to even cars. Now that’s evil!
improve the efficiency of the trebuchet:
In the next chapter, we will continue with the
■ Vary the length of the sling; start by making it theme of weapons and make ourselves a ferocious
longer. minigun.