Figure 2 Turning the windlass
the need to shift the handspike by using a ratchet wheel was a great step forward。
Let us start by considering the use of pawls to prevent backslip, as described by Sir Henry Mainwaring:
4‘Gladstone’s patent’, Mechanics’ Magazine, XXX, 434。
Figure 3 (left) A, sliding pawls, and B, hanging pawls
Figure 4 (above)A, drop pawls
[Windlasses] are never used in our great ships, but the Flemings do use them in good ships。 The reason is for that they go very slightly manned, and the windlass doth purchase more than the capstan, and with no danger to the men。 For the windlass they heave about with handspikes put into holes made at either end; and though they cannot heave forward, or should one fail, the windlass will pawl itself。 But at the capstan, if any fail, it may be the rest will be thrown from the capstan and their brains beaten out against the ship’s sides, if they weigh in a sea- gate; but the capstan doth purchase faster by much, [and therefore we (having men enough to man it), do use that]。5
This passage is interesting for two reasons。 It explains why great vessels of the mid- seventeenth century were fitted with capstans and smaller ones with windlasses, and specifically underlines that windlasses pawled themselves, and were for this reason safer, if slower, than capstans。
Capstan pawls and windlass pawls
The sliding pawls of a capstan in the fifteenth to eighteenth century, as in figure 3 (A), rotated in the horizontal plane, were not ‘self-pawling’, and had to be kicked into place between the capstan whelps when needed。 Spring-loaded pawls were used in other applications, but never with capstans。 The earliest self-acting pawls for capstans (hanging pawls) appear some time in the late eighteenth century and took the form shown in figure 3(B)。 They depended from the deck-beams and engaged with teeth on the drumhead of the lower capstan, there being one for each direction of rotation。 A second type of hinged reversible drop pawl, shown at (A) in figure 4, was invented by A。 G。 Eckhardt, and installed aboard HMS Defiance in 1772。6 These were secured to the lower rim of the capstan-barrel and engaged a circular ratchet plate fastened to the deck。 This type of pawl was later universally adopted, but surprisingly not when originally proposed by Eckhardt。 The idea was forgotten, until reinvented in France by Étienne de Lalande about 20 years later。7 Windlasses, on the other hand, had been self-pawling, since at least the seventeenth century, and likely earlier。 Falconer explains how and these early windlass pawls worked:
5Manwaring and Perrin, Life & Works of Sir Henry Mainwaring, II, 257。
6Harland, ‘Eckhardt’, 19–24。
7Montucia, des Mathématiques, 588。
Figure 5 (left) A toothed-rack windlass with three pawls
Figure 6 (below) A ratchet wheel with both driving and retaining pawls
It is furnished 。 。 。 with strong pawls
。 。 。 formed of wood or iron, [which] fall into notches cutinthe surface of the windlass and lined with plates of iron。 Each of the pawls 。 。 。 falls eight times into the notches at every revolution 。 。 。, because there are eight notches placed on its circumference under the pawls。 So if the windlass is 20 inches in diameter, and purchases five feet of cable at every revolution, it will be prevented from turning back, or losing any part thereof, at every seven inches nearly, which is heaved in upon its surface。8
Because the windlass barrel is horizontal, gravity causes the pawls to drop into the notches, and they work well enough if made of wood, but even more effectively if made of iron。 In the latter half of the eighteenth century, effectiveness was improved and safety increased by having three or more pawls working in tandem, and by replacing the mortises with a toothed rack with more teeth, usually multiples of eight。 Figure 5 is based on a contemporary drawing from the 1780s。 十九世纪锚机的发展英文文献和中文翻译(2):http://www.youerw.com/fanyi/lunwen_96310.html