Booster (steam locomotive)
In the US railways, a small two-cylinder steam engine was called a booster , and it drove the rear axle or the first axle of the tender on steam locomotives .
This steam engine could be switched on with a clutch at low vehicle speeds below 15 mph (miles per hour, about 24 km / h) and disengaged itself automatically at speeds of about 30 mph (about 45 km / h).
They were installed to make it easier to start particularly heavy trains or to run at very low speeds . The gain in power was around 300 HP, corresponding to around 224 kW , and the gain in tractive power was around 50 kN (corresponds to around 5 tons).
Tender boosters included wheels coupled to the bogies with coupling rods , which, however, limited the maximum speed of the locomotive. They were therefore attached less frequently and mainly to shunting locomotives .
The use of boosters was particularly widespread on the New York Central Railroad , but otherwise rather rare.