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Crossbows - Spanning Methods

Hand spanned bows were initially the norm, but the strength of the archer limits the power of the bow. From around 1200 onward devices were invented to help span more and more powerful bows for the military and moneyed classes.

These started as simple belts with hooks, so that the power of your trunk muscles could be used to help span the last part of the stroke. Doubler pulleys followed on quickly and then goats foot levers were employed that quickly spanned powerful bows, however the eternal arms race between projectiles and armour carried on meaning that stronger methods of spanning were required for the stronger bows and so the windlass and the cranequin were invented.

There were of course side shoots of development such as the lever action latchet bow and the screw action balestrino.


Single Hook Spanning Belt

A strong belt is worn around the waist with the buckle at the back and the strap with the hook hanging down with the hook pointing outward. The archer turns the bow so that the top face is facing his body and catches the hook onto the centre of the string.
As the archer squats slightly and pushes down with his leg into the stirrup and then straightens, the bow is spanned. A single hook was the most common.

img - simgle hook spanning belt

DATES: 1200 onward
MECHANICAL ADVANTAGE: 1:1, but uses trunk muscles as well as leg muscles
POUNDAGE SPANNED: 300lb maximum


Double Hook Spanning Belt

A strong belt is worn around the waist with the buckle at the back and the strap with the hook hanging down with the hook pointing outward. The archer turns the bow so that the top face is facing his body and catches the hooks onto the string on each side of the stock.
The archer squats slightly and pushes down with his leg into the stirrup and then straightens, spanning the bow. Double hooks were less common, but easier to use.

img - spanning belt double hook

DATES: 1200 onward
MECHANICAL ADVANTAGE: 1:1, but uses trunk muscles as well as leg muscles
POUNDAGE SPANNED: 300lb maximum


Spanning Belt with Doubler Pulley

A strong belt is worn around the waist with the buckle at the back and the strap with the hook and pulley hanging down with the hook pointing outward. The archer turns the bow so that the top face is facing his body and catches the hooks onto the string on each side of the stock.
The end of the cords terminate in a fitting and this is attached to the bow, the bow is lifted up and the hooks caught on the string. The archer squats slightly and pushes down with his leg into the stirrup and then straightens, spanning the bow.

img - spanning belt

DATES: 1250 onward
MECHANICAL ADVANTAGE: 2:1, but uses trunk muscles as well as leg muscles
POUNDAGE SPANNED: 450lb maximum


Goats Foot Lever

Two pegs protrude out from the bow near the trigger pivot. A lever is attached to the bow that hooks onto the string and the two curved legs fit over the pegs and the handle drawn back so that the string is pulled back to the nut. This can be done with smaller levers with the bow in the shooters hands, but larger levers for stronger bows often require other positions which bear the users weight down onto the mechanism. Once the string is drawn back, the lever is removed.

img - goats foot lever

DATES: 1300 onward
MECHANICAL ADVANTAGE: constantly changes during the lever movement and dependent on lever design, but up to 30:1
POUNDAGE SPANNED: 450lb maximum


Windlass

The archer places the cap of the mechanism on the butt of the bow and latches the hooks onto the string. The archers' foot is placed in the stirrup with the upper face of the bow facing outward and turns the cranks on the side of the cap. This rotates a spindle that winds a cord that passes through two sets of pulleys attached to the hook and another pulley on the side of the cap, to draw the string back. Once engaged the windlass is removed.

img - windlass

DATES: 1400 onward
MECHANICAL ADVANTAGE: constant advantage through each rotation, but around 160:1 (from hand grips)
POUNDAGE SPANNED: 1200lb maximum


15thC and 16thC Cranequin

The cranequin is slipped over the stock of the bow and the loop catches on the pegs that stick out from either side of the stock well behind the trigger. The hooks on the rack are latched onto the string and whilst the bow is held in the hands, the handle is rotated to turn the compound gearbox and draw the string back. Once the string is engaged the cranequin is removed.

img - cranequin

DATES: 1400 onward
MECHANICAL ADVANTAGE: constant advantage through each rotation, but around 600:1 (from hand grip)
POUNDAGE SPANNED: 1200lb maximum


16thC and 17thC Cranequin

The cranequin is slipped over the stock of the bow and the loop catches on the pegs that stick out from either side of the stock well behind the trigger. The hooks on the rack are latched onto the string and whilst the bow is held in the hands, the handle is rotated to turn the compound gearbox and draw the string back. Once the string is engaged the cranequin is removed. Larger primary gears meant that later cranequins can span heavier bowsimg - cranequin.

DATES: 1500 onward
MECHANICAL ADVANTAGE: constant advantage through each rotation, but around 840:1(from hand grip)
POUNDAGE SPANNED: 1800lb maximum


Lever Action

An inbuilt lever is rotated forward the trigger is caught onto the string; the trigger is attached to the lever. The lever is then rotated back down and latched shut. The trigger is on top of the bow and is now released. The mechanical advantage is good, but it complicates bow construction hugely.

img - lever action

DATES: 1560 onward
MECHANICAL ADVANTAGE: constantly changes during the lever movement and dependent on lever design, but up to 25:1
POUNDAGE SPANNED: 300lb maximum