Many changes, some minor and some major, were incorporated in the _John Bull_ during the next few years. The most noticeable was the addition of a 2-wheeled pilot, suggested in 1832 by Robert L. Stevens to guide the locomotive around the sharp curves common in the tracks of that era. In order to attach the pilot to the front axle, the outside rods and cranks connecting the front and back axles had to be permanently removed, thus reducing the number of drivers from four to two. The _John Bull_ has ever since been driven by only the two rear wheels (figure 30). The wheels of the pilot are 29 inches in diameter. Another early permanent change was the replacement of the wooden-spoked wheels with those of cast iron. The old wooden carriage-type wheels could not stand up under service in America, where sharp curves in the tracks prevailed. A wheel, said to be one of the originals (figure 31) but lacking the flanged metal tire, was presented to the National Museum (USNM 181194) by the Pennsylvania Railroad Co. in 1894. An inch or so less in diameter than 54 inches, the wheel would certainly be of the original size if the tire were in place. The 14 spokes and the felloe are of wood. Metal bands, similar to the crank rings of the _America_ (now affixed to the reconstructed wheels of the restored _Stourbridge Lion_, see p. 20), are included in the construction of this old wheel of the _John Bull_. [Illustration: Figure 31.—Original wooden-spoked wheel of _John Bull_, in National Museum.] Whether or not it is one of the original wheels applied to the locomotive by Stephenson can not at this time be definitely proved. Possibly it is an early wooden-spoked wheel built and tried by the Camden and Amboy prior to the adoption of the all-metal wheels now on the locomotive. Another similar wheel, until recently located in the Pennsylvania’s library in its Suburban Station Building in Philadelphia, is now in storage. These two wheels were included in that railroad’s exhibit at the World’s Columbian Exposition in 1893. Among the many other changes to the _John Bull_ were the addition of a bell, a whistle, and a headlight, as well as a dial-type steam pressure gauge (figure 32), and the relocation of the axle springs, the water cocks, the safety valve, and the steam dome. At one time a cab was installed at the rear of the locomotive, and an 8-wheeled tender was in use (figure 33). The tender as seen today is basically original, but much of the woodwork was in such poor repair that it was completely disassembled in 1910 and stored, the rotted pieces of wood being discarded. In 1930 the tender was completely restored at the Altoona shops of the Pennsylvania Railroad Co., and since that time has been exhibited constantly with the locomotive. [Illustration: Figure 32.—_John Bull_ on display in National Museum. Note controls and modern steam pressure gauge.]