The subject came up in another thread.
I have frequently heard or seen mention of chaining steam locos to the rail in roundhouses to prevent accidental movement.
I always wondered how well that worked. Yes a chain even just laying across the rail at the wheel will stop a locomotive (steam or diesel) from _rolling_ because the loco actually has to climb up over the chain which means lifting a wheel with maybe 35,000 lbs on it. So a chain suffices to protect against roll-aways.
But if a chain is wrapped around the rail and thru the spokes for a steam engine with a leaky throttle I don't get it. A constant, tho small, throttle leak should be able to eventually put full boiler pressure on the piston. Since the loco might have 50,000 to 100,000 lbs starting tractive effort I kind of think that would break the chain? So how does that work? I can see how it would hold an engine if the throttle leak was small and the loco had leaky piston packing or the cylinder cocks were left open so that little to no cylinder pressure builds up. But otherwise it seems to me that chaining a driver would not work to hold a loco? How about it, steam experts.
