Thomas Jefferson Papers

Enclosure: Drawing of a Threshing Machine, 6 April 1798

Drawing of a Threshing Machine

a.a.a.a. is the axis of the great spur wheel, and is at the same time the upper of the two cylinders for drawing in the grain. these cylinders are fluted

b.b.b.b. is the under cylinder. they are fluted, and the under one has a small cast iron wheel toothed on the edge (like those in a wheat fan) having a broken joint in it’s axis (like those in Martin’s drills) which permits the under cylinder to approach or recede from the upper one, without displacing the toothed wheel, which is moved by it’s taking in a similar toothed wheel on the upper cylinder or axis.

c.c.c.c. is the great spur wheel.

d.d.d.d. is an iron toothed or pinion wheel, the number of whose teeth is one tenth of those of the great spur wheel. it is fixed on the axis of the drum wheel which is

e.e.e.e. of such a radius as with it’s beater f. to pass the cylinders nearly by brushing them.

f.f.f.f. are 4. beaters mortised on the arms of the Drum wheel.

g.g. is an inclined plane for spreading the sheaf on and sliding it in between the cylinders.

h.h.h. are two sills made in the form of those of a sleigh for drawing the machine. they serve at the same time as sills for the frame which will be readily understood by the above drawing without particular explanation.

this drawing is strictly in the proportions of the model from which it is taken.

PrC (DLC).

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