Side rods.

[Lone Cat]

While side rods are classic transmission systems for steam locomotives and steam railcars. certain models of Electric and Diesel locomotives also have it.
1. By 1910-1930s. isn't there a better transmission systems available unto Electric and Diesel units?
2. What is an advantage of side rods over axels and hydraulics transmissions? if the danger of side rods hitting crews and passengers are the BIG disadvantages of Side rods.
3. What is the use of a set of smaller rods connecting to a bigger siderods and a pair of pistons located on top of the main (and bigger) pistons. seen in 1900s era steamers? is there any 4-4-0 stearmers have this kind of secondary rods?

[arop]

1: Electric locos:
The reason side rods were used on early electric locomotives is the size of electric motors in the beginning. Later when it was possible to build the motors smaller, they were placed between the driving wheels.

2: Diesel locos:
Side rods on smaller diesel locos are usually used, when transmission is either mechanical or hydraulic instead of using cogwheels/chains between drivers.

3: Steam locos:
On compound locos, system Vauclain, there are two sets of cylinders: First the steam goes to the upper high pressure cylinders, then being used twice, it goes to the lower low pressure cylinders with a common inside valve gear. This fuel saving system was mostly used in the US. In Europe the high pressure cylinders were usually placed between the frames, and the valve gear was placed outside the frames, utilizing easier maintenance. Generally these fuel saving, but rather complicated arrangements proved to be heavy on maintenance, and later most steam engines were built as simples with 2 or 3 cylinders, exept in France, where compound locomotives were very popular until the end of steam.