Franklin Self-Adjusting Spring-Loaded Wedges Self-adjusting spring-loaded wedges, supplied by the Franklin corporation, were designed to maintain zero clearance between axleboxes and horn guides, thereby preventing the shock loads or “knocks” that were once commonly heard from run-down locomotives as the clearances between axle boxes and hornguides were taken up with reversal of piston thrust. In […]
Franklin-type Engine-Tender Buffer Mechanism A Franklin-type radial buffer provides a rigid connection between a locomotive and tender, allowing no relative movement in the fore-and-aft direction but allowing relative radial movement for negotiating curves. The diagram of a Franklin radial buffer (below) illustrates the basic principle where two wedges are pressed towards each other by coil […]
A locomotive must be designed so that its tractive effort is not so high that it “loses its feet” on starting. Equally importantly, its tractive effort should be limited so that it does not slip at speed. This latter becomes a much more important consideration for Second Generation Steam locomotives like the 5AT which maintain a high tractive effort at […]
The multiple element Piston Rod Packings fitted to The Red Devil are described on page 176 of his book as follows: Fully floating five-element metallic piston rod packings replaced the single element Paxton-Mitchell type which did not guarantee steam tightness over long periods without attention. Some time previously Porta had sent me a drawing made […]
This page covers briefly a number of topics related to the enhancement of valve events to improve a locomotive’s performance. These come under the following headings: Valve events Valve travel Porta’s view on lead Fixed lead Variable lead Ring-controlled events A separate page covering valves and valve gear can be found in the Technical Terms […]
Various other pages of this website are devoted to specific aspects of piston valve design including: An explanation of terminology relating to valves and valve gear; A discussion of the principles of tribology and lubrication with particular emphasis on piston valves; A discussion on the enhancement of valve events to improve steamflows and reduce losses; […]
The Oxford Dictionary defines tribology as the branch of science and technology concerned with surfaces in relative motion, as in bearings. It is therefore inseparably associated with the subject of lubrication. Ing. L.D. Porta was the first engineer to apply the science of tribology to the design of steam locomotives, seeing it as an essential […]
It may seem counterintuitive that locomotives with smaller driving wheels should achieve higher efficiency than those with larger driving wheels, but it is a fact that high engine rotation rates offer a number of technalogical benefits. It may also seem counterintuitive that long strokes (such as used on GWR 2-cylinder locos) also offer advantages […]