View single post by Salada
 Posted: Fri Oct 14th, 2016 01:14 am
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Salada



Joined: Mon Nov 4th, 2013
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Si,

To give you an idea on bridge weights don't forget these "spindly" prototypes are from what Woodie would call a 'heavy' NG line, the D&RGW main line. That should give you a comparative guide as to what an MMM bridge would have been like, much lighter & designed on a fag packet.

If you omitted the top level transverse struts you would have a 'through truss' bridge, but I've never seen a full height through truss design. Removing these upper struts & reducing the side truss height would give a 'pony truss' but altering your kit would be almost impossible.

Pneumatic rivet guns came into shipyard use c. 1880s -1890s on; railway shops usually used hydraulic rivet guns(I don't know why the difference).
You are correct that portable riveting only started about 1910 onwards. Rivet guns need at least c. 110-120 psi & a good cfm rate - I've done my share of rivet driving. Air is also a must for the rivet heating coke stove, Any rivet less than white hot in the hole won't be any good.

Your best bet might be No 3, bought second hand when the line was at its peak. A lot of bridges, grades & railroad infrastructure were washed away by torrential floods in, I think, 1908 in Colorado and New Mexico, resulting in steel truss bridges replacing previous trestles.

Funny you should comment on Pagosa Junction as a prototype inspiration, I spent damn near a year researching it as an actual location for myself - the problem was that the depot area was separated from the passing sidings by that ¥$€# bridge - I could not fit it all in along a 11' 8" wall. Chavez Junction is based on Pagosa Junction without the bridge and flipped east-west to make better use of the available space.

Ken - unusual 4 truck wellcar; typical MMM shop build with the outer trucks mounted on inner frame extensions; inspiration for Si ?.

Regards, Michael

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