Making a Working Model of Eli Whitney's Cotton Gin

    My wife's consuming interest in history rivals mine at times and her latest endeavor is a good case in point. She is currently raising a mini-crop of naturally colored organic cotton to learn about the plant and its product.

Some of Lindy's Cotton, Day 67
Photo by Lindy Miller 2013

     Further along into this project she hopes to become a good cotton spinner as well. Since cotton comes with seeds mixed in the fibers, my part in all this is to build her a working model of Eli Whitney's Cotton Gin .That way, she can process her anticipated cotton bolls with historic flair and eventually do demonstrations as well.

 Patent Drawing for Eli Whitney's
Cotton Gin
Image Courtesy en.wikipedia.org

    Patented in 1794, the Cotton Gin in retrospect has a dark side to its history. Before its invention, cotton seeds had to be laboriously removed from the fiber by hand. In general, this time-consuming process held back any large scale production of cotton until Whitney's revolutionary machine arrived.

    Once mechanical ginning was established, cotton production soared in the South. Some historians today name the Cotton Gin as the root cause of the Civil War. I think that's a bit of a stretch but it did play a part in the expansion of slavery even though it was intended to reduce labor.

    In order to build a working model, I had to understand the basic function of the Gin. The three key elements in Whitney's design are the rotating claw-like hooks (that grab the cotton fiber), the slotted comb that they rotate through (the narrow width of the comb's spacing keeps the seeds from being pulled through by the hooks) and the rotating brushes that remove the seedless (ginned) fiber from the hooks.

               

Original Patent Model
Note the Ginned Seeds in the Lower Front and
the Cleaned Cotton in the Upper Rear
Image Courtesy history.com

    I started by studying the 1794 patent drawing but was disappointed to learn that the accompanying description is unavailable. Two original models of the Gin have survived, one is the patent model and the other a later version used in the court battles against infringement. After studying the few pictures of the models online, I finally figured out the mysterious curved, springy comb that allows the ginned seeds to fall through.

Close-up View of Another Early Model
Note the Hooks, Slotted Comb and Springy Wire Comb
Image Courtesy of newsdesk.si.edu

    My first attempt at making a wooden drum with hooks was a dismal failure. I drove wire nails into a large dowel and cut them to length. After bending them all into directional hooks, it started to look pretty good. What I discovered was, the hooks tended to rotate, which doomed their chances of proper alignment with the all important comb. Whitney had used flat metal hooks but I didn't see myself cutting out a bazillion of those little things.

My Version of the Hook Drum
Photos Courtesy Lindy Miller
2013

     Instead, I created little circular saws in sheet steel similar to what was used in a later patent improvement by Hogden Holmes. In order to build up a cylinder, I sandwiched my little sawblades between discs of 3/8" plywood. Once stacked, I ran two small steel rods through on either side of center and riveted their ends over washers. I squared the center shaft hole by driving a piece of 1/4" square stock through the existing 1/4" round hole. The finished drum turned out to be about 4  3/4" long by 3" in diameter.

View From the Top
Showing Hook Drum in Place, Spring Comb
and One Brush Section

    The rotating drum is the heart of the machine and everything else is built around it. I constructed the housing box of 1" x 6" #2 pine and sized the inside to accomodate the length of the drum. I could only guess at the overall size of the box as this was quickly becoming a design as-you-go project. Next came cutting out the steel comb, which had to be curved to hug the drum but still allow the free motion of the hooks.

    The rotating brush drum was created using a 2" dowel and four sawed out sections of a new scrub brush. Little by little, it was starting to come together. The previously mentioned curved, spring comb thingy had to angle into the rotating hook drum at such a degree to cradle the raw cotton. I made mine removable as that's what the orignal model appears to have.

The Finished Model Cotton Gin
Showing the Completed Brush Drum and Pulleys

   Last but not least was the crank handle (mounted on the hook drum shaft) on one side and the two pulleys on the other.  The ratio of my pulleys is approximately 2.5 to 1. For a belt, I used a rubber band and twisted it in the middle to reverse the direction of the brush drum pulley as per the orignal design.

View From the Other Side
Showing the Crank and Slotted Comb

    Now came the test. Luckily, my wife had some unginned cotton bolls so we didn't have to wait months for her crop to mature. Cranking away,  it made this great primitive machine noise and the best part was.....................the darn thing WORKED and................. my wife is happy. Mission accomplished !

            To see a demonstration of the model, use the link below to go to Youtube:

                                  https://www.youtube.com/watch?v=QPPfFHF7nvg

 If you would like to build this working model, you can purchase a complete plan from us on Ebay. Just search Ebay for Cotton Gin Plan.