Throttle Lock

Updated: 10/21/2023


The purpose of the throttle lock is to hold a specific throttle position so that it does not drift further open due to the force of the steam pressure flowing through the throttle valve. It enables the driver to let go of the throttle handel and have faith that he will not need to pay constant attention to it or make minor adjustments to correct drift.


The position of an unlocked throttle is continuously variable within the range set by the full open and shut positions. The number of possible locked positions is constrained by the teeth or notches of the locking plate. Most locking plates have teeth covering the entire edge of the plate enabling the throttle to be locked in many desired positions. Others do not to force the driver to operate in either full or cracked throttle possitions.

Mountain King's Throttle Lock:

Roof Mounted Throttle Lever Schematic:

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Ⓒ 2023 Odinny

Video Demonstration courtesy of
The C16 Locomotive Society