Si 



Figure 4. — A 4-wheel safety truck fitted with A. F. Smith's swing-bolter centering device. Built by the 

 Hinkley Locomotive Works. From Gustavus Weissenborn, American Locomotive Engineering and Railway 

 Mechanism, New York, 1871, pi. 88. 



neously lifted ofT the track, the truck could pass over 

 "quite a considerable obstruction." ^ Bissell further 

 claimed: 



In running on either a straight or curved track one of the 

 truck wheels often breaks off, and the truck swivels around 

 on its center pin in consequence, and throws the engine 

 off the track, but with my device one wheel, or even the 

 two wheels on the opposite sides diagonally of the truck 

 might break off and still the truck would not run off, 

 because its position is set and it has no a.xis of motion around 

 which it could swing. . . . 



The other problem Bissell wished to correct was 

 the oscillation and chatter of the leading truck. 

 This was accomplished by a simple centering device 

 in the form of a pair of V-shaped double incline 

 planes (D on fig. 3) situated at the center of the truck 

 frame (A) . The lower planes of the pair were fastened 

 to the truck frame and the upper, cast in the form of 

 a bridge, were attached to the locomotive frame (C) 

 by a center plate. But while the portion of the 

 locomotive's weight assigned to the leading wheels 



was borne at the center of the truck, as in the 

 conventional design, the center plate was no longer 

 the point of rotation. On a straight track the V's 

 would be at their bottom position and thus prevent 

 the truck from vibrating.'' When the locomotive 

 entered a curve the planes allowed its forward weight 

 to bear continuously on all four wheels, and at the 

 same time controlled any exaggerated swing caused 

 by centrifugal force. 



The centering device is thus explained in the patent 

 specification (figure numbers are omitted) : 



I therefore obviate this difficulty [the oscillation of the 

 truck] by providing two inclined planes . . . formed double 

 as shown and of an angle proportioned to the weight of 

 the forward part of the locomotive and the velocity of the 

 same, . . . The position of the inclines is such that the 

 blocks [v's] rest in the lowest part of the double inclines 

 when the engine is on a straight track, and on coming" onto 

 a curve the inertia of the engine ... is expended in going 

 up the inclines, as the truck moves laterally toward the 

 inner part of the curve; and on coming onto a straight line 



3 Connecting both truck axles with an equalizing lever so that 

 they acted in sympathy with each other also did much to pre- 

 vent derailments on rough trackage. 



* Bissell states in the patent specification that inclined planes 

 had been previously applied to railroad car trucks. His claim 

 rested on the application of this device to locomotive trucksl 



122 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY .A.ND TECHNOLOGY 



