According to an 1860s account of developments in naval artillery during the Age of Sail (specifically the American Revolutionary War & Napoleonic Wars), a reliable method was devised more than 200 years ago to measure cannon ball velocities.
In the 1700s, French artilleryists designed a mechanical contraption to measure projectile speed. Spies working for the English eventually spilt the beans to the outside world.
Here's the gizmo:
Imagine a large but lightweight cylinder, say 6' diameter and 40' long. This cylinder rotates at a steady speed within a support cradle, by means of a geared flywheel. The no. of revolutions per second is known and constant.
Each end of this cylinder is fitted with a stout paper disk, divided and marked into 360 degrees. The disks are indexed to each other so their degree readings correspond.
How the gizmo works:
Now fire a cannon ball through the steadily rotating cylinder. Note the degree at which the ball pierces each disk at it travels through the rotating cylinder.
We now have enough data to compute distance travelled in a given time = velocity.
Like with modern day chronys, it was important to figure out how far back the muzzle needed to be. As now, it was also important to aim so the ball exactly transits the cylinder's longitudinal dimension, i.e. straight through.
Pretty ingenious.
In the 1700s, French artilleryists designed a mechanical contraption to measure projectile speed. Spies working for the English eventually spilt the beans to the outside world.
Here's the gizmo:
Imagine a large but lightweight cylinder, say 6' diameter and 40' long. This cylinder rotates at a steady speed within a support cradle, by means of a geared flywheel. The no. of revolutions per second is known and constant.
Each end of this cylinder is fitted with a stout paper disk, divided and marked into 360 degrees. The disks are indexed to each other so their degree readings correspond.
How the gizmo works:
Now fire a cannon ball through the steadily rotating cylinder. Note the degree at which the ball pierces each disk at it travels through the rotating cylinder.
We now have enough data to compute distance travelled in a given time = velocity.
Like with modern day chronys, it was important to figure out how far back the muzzle needed to be. As now, it was also important to aim so the ball exactly transits the cylinder's longitudinal dimension, i.e. straight through.
Pretty ingenious.
