The
original shipper fork carriage was improved by separating the original
bearings to a greater distance, and eliminating one of the two bearings
on one end. This permitted a smooth and free operation of the small
sliding carriage.

In August 1893, possibly as a result of indoor experiments, Frank
discovered that the chains running from the small 5-tooth[22] jackshaft
sprockets to the large, bronze, wheel sprockets were tight at some times
and loose at others. This caused considerable unnecessary noise. The
difficulty apparently was the result of the sprockets being cast and not
machined. The patternmaker had said he believed he could make the
pattern accurately enough so that no machining of the castings would be
necessary. Nice castings were produced, but "these sprockets were the
reason why an unusual construction was put on the crankshaft [meaning
jackshaft]," explained Frank Duryea during an interview at the National
Museum on November 9, 1956. Elaborating further, in reply to the queries
of E. A. Battison, of the Museum's division of engineering, Duryea told
of the problem and the solution when he explained that the sprockets had
places where the shrinkage was not even. The hot metal, contracting as
it cooled, did not seem to contract uniformly, creating slightly unequal
distances between teeth. This resulted in the chain hanging quite loose
in some places and in others the tightness prevented adjustment. He
contacted Will Russell, foreman of the Russell shop, where the
automobile was made, and Russell showed him a device, built by George
Warwick, who had made the Warwick bicycle. It was an internal-cut gear,
according to Duryea's description, with sprocket teeth on its periphery.
With sprockets outside and normal teeth inside, the wheels were about 6
inches in diameter, externally.

These little internal-gear sprockets were hung on double-shrouded
pinions secured to each end of the jackshaft. A solid disc or housing
fitted against both ends of the pinion to prevent the internal gear
from working off sideways. Duryea explained the function of these
unique little parts: "as soon as tension came on that ring gear that we
talked about, it not only tightened the chain hanging on this sprocket
on the upper side, but it tightened it on both sides. [The sprocket]
rocks right out: both sides of the chain are tight."

This feature is one rarely encountered elsewhere, and Duryea, later in
the interview said, "To tell y