Medieval Physics - Jousting

In a previous blog entry, I gave a short summary of the physics and history of the bow and arrow (thanks to all you CR4 users who shared your insight and knowledge on the subject). Today I'd like to delve a little bit into the "Sport of Kings": jousting.

The most vivid picture I have of jousting is from the movie A Knight's Tale, in which a squire (Heath Ledger) takes up the sport in order to "change his stars" and become a knight. Jousting was (and still is) a sport involving a horse, a rider (knight), and a lance (the knight's weapon). In jousting competitions, two knights would draw their lances, ride at each other, and attempt to knock the other off their horse. In earlier (more brutal) versions of jousting, hand-to-hand combat often followed, the objective being to incapacitate the opponent in order to win his horse and equipment.

The sport of jousting came about as a result of the popularity of the lance in medieval warfare. The combat lance was the primary weapon used by mounted soldiers, especially those leading a charge. It is a long spear-like weapon, ranging from 9 to 15 feet in length. It was made of wood, with a metal (typically iron or steel) tip on the end. Its shape and length made it unsuitable for throwing or repeated thrusting, but was instead an impact weapon meant to utilize the force of the horse and rider. The circular handguard on the lance (called a vamplate) was meant to keep the rider's hand from sliding upon impact.

In this spirit of combat, the joust was a show of a knight's ability to utilize his lance to transfer his and his horse's momentum into his opponent, all while deflecting the blow of his opponent to remain on his horse. The knight who could break more lances on his opponent (i.e. score more points) and/or dehorse him was the victor. To reduce the chance of death or severe injury, lances used in the jousting sport were made with coronals (crown shaped metal caps with three blunted prongs) instead of metal blades. The prongs allowed the lance to more easily catch the knight's shield or armor.

So how much force was a jouster actually able to generate through his lance? One might think that a simple force equation of mass times acceleration (F=ma) would suffice. Sure, it is true that a larger knight with heavier armor and a bigger and faster horse with be able to generate more momentum and force. Unfortunately, this generic force equation is an oversimplification that incorporates some faulty assumptions, the first being that the lance, knight, and horse are all one mass. This is not true, as the lance is held by the rider's hand/arm which is connected to the rider's torso, which is connected to the rider's lower body, which is on top of the horse. All of these are separate pieces which have the potential to move and give upon impact and reduce the force from and to the riders. Thus it is the skill of the knight that determines how effectively he can incorporate all of these parts together to generate more force.

Another misplaced assumption is that all the force in the equation translates to the tip of lance. In reality, other factors will reduce the force of the blow, such as the lance's point of attack (i.e. if the opponent is not directly in line with the rider's acceleration, the lance will be hitting at an angle). Also, any deflection of the lance off the opponent's armor will reduce the force of the blow. Because the upper and lower and lower body can move separately (the torso can rotate left and right), a knight that deflects will experience torque when hit more than a force that pushes him backward off the saddle.

Ultimately, the true limiting factor on force is the strength of the lance. Because the lance is made of wood, the lance will often break and shatter from a good hit. Thus the strength of the lance is a limit on the maximum force that can be transferred to the victim's body from the hit.

There are other factors to consider as well, such as return force. Assuming the lance is well gripped or attached to the knight, the knight must be ready to resist the return force generated when hitting his opponent, else he be dehorsed himself. Also, since both knights will be armed in the contest, there is added complexity of who hits first and what movement occurs in between hits.

Obviously this is not an exhaustive analysis, and I don't have any numbers on what forces generated by jousters would actually be (any takers?). Safe to say, if it's enough force to cause severe injury and knock a heavily armored man off his horse, it's quite a bit of force! Because of this, jousting today has moved away from direct physical combat to a skill sport of hitting targets and catching rings. In 1962, this evolved form of jousting was made the official sport of the state of Maryland, and it is still alive and well today.

Other sources

myarmoury.com

Lordsandladies.org