in the new FRA boiler code, tri cocks are nolonger required on steam locomotives. The boiling action of water around the firebox creates a higher reading of the water level by the tri cock than what is actualy in the boiler. This becomes more apparent as the intensity of the fire increases. Water glasses are not affected by this and give a more accurate reading if they are maintained properly. A variation on the water glass is the water collum. This type of measurung device uses a water glass attached to a water reservoir that takes some of the motion out of the water activity. When sitting still the water in a boiler does not typically move around a lot unless an injector, feed water system or water glass drain is used. Going down the road the water level in the boiler can vibrate an inch or more. The water collum design is to limit this motion.
Braking a train down hill depends upon a lot of factors including the type of equipment you are using. The K class engines at the C&TS have what is called a drifting throttle which can be used in the steam locomotive to break the locomotive and cars. This puts a lot of wear on running gear parts. If you have a train it is est for the steam engine to keep a little steam in the cylinders to keep lubrication flowing propertly and with the engine air brakes released on the locomotive, use the train to control your speed. If you get too much heat into a locomotive tire you can cause a tire to expand and move or come off on the wheel. This can be very dangerous as a friend doing a roll by found out on the SP durring the days of steam. The last tire hit him on a 2-10-2 during a roll by. It is always a good idea to stay away from the tracks.
