Re: Crane Underside Detail
John C. La Rue, Jr. <MOFWCABOOSE@...>
From what can be seen of it, this crane is technically a "bridge derrick" which had the self-propulsion feature mainly as a means of positioning itself. A true "locomotive crane" was also expected to switch and move additional cars. Locomotive cranes went to gears rather then chains for their transmission drives very early, by 1895 for most makes, partly because both axles (on a four-wheeled crane) and both inside axles (on an eight-wheeled crane) were powered to add to the tractive effort.
The pictures show this derrick in a very precarious position and the wreckmaster is going to have to be very careful when planning to roll it upright again to prevent it from slipping off the edge and suffering additional damage. It is entirely possible that if the derrick was railroad-owned, it might have ended up being scrapped rather then repaired, because of its age and the availability of better cranes to do the work.
John C. La Rue, Jr.
Bonita Springs, FL
From: destorzek@... [STMFC]
Sent: Sun, Jan 25, 2015 12:48 pm
Subject: Re: [STMFC] Crane Underside Detail
You realize the chain has to twist as the truck swivels. The chains that form the speed reduction, that run on sprockets on fixed shafts, are roller chain, similar to bicycle chain. But the last chain in the drive, which runs at the slowest speed, is round link chain which is better at dealing with the misalignment.
Typically, this last drive chain was taken down if the crane was to be handled in a train. The speed restrictions were due more to the poor riding characteristics of cranes in general; they tend to bounce, even if the boom is supported by a cradle on the idler car.