Unique Chinese weapon — Pai Gan (拍竿)

Scale model of a Sui Dynasty capital warship equipped with six V-shape Pai Gan. Source: Wikimedia Commons.

Pai Gan (拍竿, lit. 'Swatting pole') was an ancient Chinese weapon fitted to various warships to pulverise enemy ship at close range. Said to be able to outright sink a ship in one tremendous downward smash, it was in many ways an omni-directional alternative to naval ram. 

Pai Gan was first recorded in use during the uprising against Western Jin Dynasty led by Du Tao (杜弢) in 311 A.D. and quickly grew in popularity in the subsequent dynasties. Before long, this potent weapon had become one of the most common naval weapons in China, so much so specialised warships designed to use Pai Gan as their primary armament became a staple in the Chinese navy and were given descriptive names such as Pai Jian (拍艦, lit.'Swatting ship') and Jin Chi Jian (金翅艦, lit. 'Golden wings ship', likely named after raised Pai Gan mounted at the port and starboard of said ship). Pai Gan gradually fell out of popularity after Song period due to the advent of firearms, although it continued to see limited use during Ming period.

Theoretical operation

Illustration of a Lou Chuan (樓舡), or tower ship, from 'Wu Jing Zong Yao (《武經總要》)'. Historians are yet undecided about whether the crane-like device mounted on the top of the ship is an indigenous form of counterweight trebuchet, or a Pai Gan.

Although its exact nature is unclear, written records describe Pai Gan as being similar to a ship's mast, as well as compare it to a Jie Gao (桔槔), or shadoof. In fact, the weapon was simply called Jie Gao initially before acquiring a unique name to distinguish it from the irrigation tool. 

Based on written descriptions, it is no hard to imagine Pai Gan as a giant boulder or wrecking ball mounted on a striking arm, or essentially a crane-operated hammer. Historians proposed a few designs as possible candidates for Pai Gan, although each comes with their own pros and cons. The first candidate, a "T-shape" Pai Gan, most closely resembles a Jie Gao/shadoof, but has abysmal reach and is mechanically inefficient, not to mention its hammer has a high chance of smashing into the ship it is mounted on. On the other hand, the second candidate, a "V-shape" Pai Gan, operates on a similar principle as Greek Sambuca and Roman Corvus which is far more mechanically sound, although its design certainly does not evoke the image of a Jie Gan/shadoof.

Given that both proposed designs have their own drawbacks, I would also like to give my own take on this weapon. My own proposed design is a modified version of "T-shape" Pai Gan mounted on a much shorter pole, both to prevent the hammer from smashing into the ship, and to minimise its negative effect on the ship's stability. I also changed the initial position of the hammer from facing away from the ship to facing towards the ship, so that the rope must be manually pulled (instead of simply being released from a winch) for the weapon to work. For all intents and purposes, my proposed Pai Gan is a close combat version of traction trebuchet.