Student Activity Packet

Activity #2: Fixing a Gin: Math and History at Your Desk


In order to complete the activity worksheet, you will read a one-page introduction, look closely at a bill from an actual gin repairer, and study a diagram of how a cotton gin works.


April Ellison was born in 1790, one of perhaps a dozen slaves on a plantation in South Carolina. His owner trained him as a cotton gin builder and repairer, apprenticing him at age 10 to William McCreight, a gin maker in Winnsboro, South Carolina. He worked as an apprentice in McCreight's gin building shop for about six years, learning how to work iron at the blacksmith's forge, how to use the tools of the machinist to turn and shape metal, and how to work wood at the carpenter's workbench.

Ellison stayed at the shop for another eight or so years, working as a craftsman there. He married at age 21 or so, and at age 26 was given his freedom by his master. One of the first things he did was to change his name (April was a slave name) to William, the name of his former owner (and possibly, his father). And before long he went into business for himself, as a master cotton gin builder and fixer.

Ellison was a successful businessman and mechanic. By 1860 he owned, in addition to his gin shop, a large plantation, and as many as 60 slaves. (It was unusual, but not impossible, for Africans in America to own slaves; some 3,800 black slave owners were registered in the 1840 Census.) Ellison is an example of a slave who, because of his technological and business skills, was able to earn his freedom and enjoy substantial financial success.

The attached repair bill indicates that Ellison completely dissembled, rebuilt, and reassembled Waites' gin. The work was complicated and intricate, both delicate and heavy, and required all the skills of a gin maker. It involved hundreds of parts fitted snugly into a compact, sturdy machine that had to run smoothly from sunup to sundown during the ginning season. It probably took about 12 days for Ellison to do this work.

Click to view larger image of Ellison's
bill to Judge Waite

Following is one page from the account books of William Ellison, an African American gin fixer. The bill for gin repairs was sent to a local plantation owner.

October the 6th 1817: Judge Waite's Debt to April Ellison

Cylinder made new and wood tran $8.00
7 new saws @4/8 7.00
37 Saws cut deeper in the teeth @ 25 c.a.p. 8.25
New brush @$12 12.00
Taking off 41 ribs and hamering them wider
and polishing them @20 c p
Mending frames and putting in new (illegible) 1.25
New brush nut and stuff and covered
with leather
New band nut and collers ribbed 1.25
Brush bearer .62 1/2
Cylinder bearer .50
Englabing Screw 1.00
1 Bench 1.00
4 dozen of wood screws @ 1/2 .50
2 hooks for hinges .50
1 crest hook and stapel .25
Hopper board and hanging 4.50
Facing and checks 1.00
TOTAL $58.325


Drawing by William Rahr, Sammamish High School,Bellevue, WA. Used by permission.

The cylinder is the main piece of the gin which has the saws fastened to it. The saws look like circular saw blades, about 45 blades on each saw, spaced at intervals of about 3/4" along the cylinder. Saws were typically about 8" in diameter, made of iron, with about 160 teeth spaced evenly around the edge.

Saw blades wore out quickly from the hard work they did tearing apart the cotton. To cut the saws deeper meant filing all 160 points to the same angle, each about 1/4" deep. This was tedious, painstaking, and painful work. "c.a.p." means (we think) cents a piece, so there is a multiplication mistake here -- the total should be $9.25.

The brush was a hollow, leather-sheathed cylinder covered by rows of pig-bristle brushes. It rotated in the opposite direction of the saws, and pulled the ginned cotton off of the saw blades. As might be expected, the brushes wore out very quickly.

The ribs were the wooden supports between the brushes. As the gin was used, the ribs became rough, and the cotton would catch, and then choke or clog the gin. The "20 c-p" is probably 20 cents per, that is for each of the 41 ribs. These are more repairs for the brush.

A "bearer" is what we would call a "bearing," the metal piece on which the brush turns.

The hopper board fits on top of the gin, above the saws; this is where the seed cotton was dropped.

Drawing by William Rahr, Sammamish High School, Bellevue, WA. Used by permission.

What to do


  1. Go through William Ellison's bill and re-calculate his charge.

    William Ellison's Total ____________________

    Your Calculated Total ____________________

    Difference, if any ________________________

  2. Calculate the hourly wage that William earned for this job. Figure that he probably worked about 10 hours a day (the average for this period) for about 12 days.

    Number of hours worked (hours per day multiplied by the number of days) _______________________

    Total amount of bill (use Ellison's total) ________

    Wage earned per Hour (total of bill divided by number of hours) _____________________________

  3. Is this calculated wage an accurate number? Why or why not?

  4. What types of materials do you think Mr. Ellison used to repair the cotton gin? What kinds of tools?

  5. List the manufacturing processes Mr. Ellison used to make the new parts for the cotton gin. List with each process the tools used to accomplish this task.

  6. What are the differences between Mr. Ellison's bill and the one from the car repair shop?

  7. What are similarities between the bill for fixing the cotton gin and the one for fixing the car?

See a video clip about the saw gin from the Hands-On-History Room at the National Museum of American History

Copyright © 1998 The Lemelson Center for the Study of Invention and Innovation, National Museum of American History, Smithsonian Institution. All rights reserved.

Comments and questions to the Lemelson

Last Revision: 6/5/98