The Oxford University Press encyclopedia says that a capstan is “a revolving cylinder with a vertical axis used for winding a rope or cable, powered by motor or pushed around by levers.”<![if !supportFootnotes]><![endif]> Sailing ships in the 1800s had one or more capstans that were used to pull ropes to raise yards and tighten sails. A rope is wound around the barrel of the capstan and the capstan is rotated by sailors pushing on poles stuck in the square holes around the top (see figure below). The capstan is prevented from rotating backward by iron pawls at the base that drop into slots in an iron ring fixed to the deck. See the Paasch drawing below.
The Boucher 1916 model in the MFA and most plans that I have seen show the Flying Cloud with 4 capstans. Two on the ship's centerline, one on the forecastle deck and one just aft of the main mast and two side by side on the poop deck. The 1926 plans by Magoun<![if !supportFootnotes]><![endif]> say that the centerline capstans were double acting and the poop deck capstans were singe acting. Single acting capstans worked as described above with the poles directly connected to the capstan’s barrel. In double-acting capstans the top ring of holes is connected to a shaft with a gear on it that, in turn, drives planetary gears that rotate the capstan’s barrel at a slower, and this a more powerful, rate. See, for example, see the discussion of improved capstans in the American Magazine of Useful and Entertaining Knowledge.<![if !supportFootnotes]><![endif]>
I have not found any direct information on the design of the Flying Cloud's capstans. Most of the plans for the ship show the same general from of capstan - the form that shown in Paasch<![if !supportFootnotes]><![endif]> (and copied by Magoun). The same form is shown on figure 6 of Duncan McLean’s booklet<![if !supportFootnotes]><![endif]> on the McKay ship Great Republic, so it is clear that McKay used this style of capstan and, thus, it seems safe to assume that the Flying Cloud had this style of capstan when she was launched.
Paasch Plate 67
Portion of Figure 6 of McLean’s booklet on the Great Republic
Double acting capstans had two rows of holes at the top as described in Crothers<![if !supportFootnotes]><![endif]> and as can be seen in the following photo, with the top set of holes being the geared ones for higher power.
Tourists trying out the capstan on the ship Balclutha (National Park Service)
I also have found no direct information on the construction of the capstans on the Flying Cloud when she was launched but there is some circumstantial evidence that they may have been made of brass and mahogany. Donald McKay launched 8 extreme clipper ships between 1850 and 1852. Duncan McLean wrote stories in the Boston Daily Atlas about the launching of a number of them. His reports on the Stag Hound and the Flying Fish say that the capstans were of mahogany and either mounted on or inlayed with brass. For the Westward Ho and the Bald Eagle he says that they each had two of Perley's patent capstans. His other stories do not mention capstans or they just say how many capstans each ship had, without describing them.
The Monthly Nautical Magazine of May 1855 says that Allyn's patent power capstans<![if !supportFootnotes]><![endif]> had been furnished to the Flying Cloud within “the past year”<![if !supportFootnotes]><![endif]>, implying that the original capstans had been replaced. That leaves mahogany and brass, something McKay was using around the time he built the Flying Cloud, as the likely materials for the Flying Cloud’s original capstans.
Capstans are not all that large, as can be seen in the above photograph. The height of the holes for the capstan bars needs to be between hip and waist high for a sailor and sailors were about 5’ 5” tall in the mid 1850s.<![if !supportFootnotes]><![endif]> Thus the holes in a capstan should be between 30 and 40 inches off the deck (based on the average proportions of adult males). The capstan depicted in the McLean booklet on the McKay ship Great Republic was in the high end of this range, if not slightly taller, but as the photo shows, many capstans were quite a bit shorter.
<![if !supportFootnotes]><![endif]> Plans for the Flying Cloud by F. Alexander Magoun, 1926, in Clarke materials at the MIT museum, also in F. Alexander Magoun, Frigate Constitution and other historic ships (1928), page 127
<![if !supportFootnotes]><![endif]> Nathaniel Hawthorne & Elizabeth Manning Hawthorne editors, American Magazine of Useful and Entertaining Knowledge, 1837, page 204 & 5
<![if !supportFootnotes]><![endif]> Heinrich Paasch, Illustrated marine Encyclopedia (1890), plate 67
<![if !supportFootnotes]><![endif]> Duncan McLean, Description of the Largest Ship in the World, The New Clipper Great Republic of Boston, Designed, Built and Owned by Donald McKay, 1853
<![if !supportFootnotes]><![endif]> William L. Crothers, American-Built Packets and Freighters of the 1850s, (2013), page 311
<![if !supportFootnotes]><![endif]> US Patent no. 6,396 to J.E. Andrews assigned to Edwin Allyn, April 24, 1849
<![if !supportFootnotes]><![endif]> Monthly Nautical Magazine and Quarterly Review, May 1855 volume 2, page 161
<![if !supportFootnotes]><![endif]> Average height of men by year of birth, 1810 to 1980, Our World in Data