Steam & Excursion > The 611’s relatively Rigid Axles and frame ... Loco C&O614....

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The 611’s relatively Rigid Axles and frame ...

Loco C&O614....
You will find the the main rods are removed, and temporary spacers are in their place.
Also, the valve gear parts, attached to driver-powered levers, are removed.

‘Modern Side-Rod Rollers’ are precision devices.  However, Timken built-in ways to accommodate varying axle lateral displacements.   They used short rods, 2 holes per rod,  and a lot of independent joints—— so that the cumulative ‘free-play’ of the all the assemblies accommodated the lateral displacement of the axles.

Allowing Lateral displacement is important to recognize:  as engines slide through curves and get through a series of multiple double slip switches,  the axles try to slide,
left and right.  The distances between the crankpins “lengthens”.
... you need a “stretch-able” series of side rods, OR, plenty of ‘slop’ in the fit of the bearing pieces.  During the shift, the displaced rods for the ( longer) hypotenuse of a triangle....even if only by a few thousandths of an inch...the rods are whirling and fighting the changes in length that being strained.

Side Rods:  On plain bearing locos, they clank the loudest when all in a straight-line.    Upon entering curves, they quiet-down through curves —-they are ‘stretched’ and quiet.

That’s why we always want plenty of free-play with plain-bearing siderods, even on their most recent orders for new construction locos.

It’s Why many railroads...including SP & UP stayed with plain bearing siderods—- SP adoption of oil-filled driving box lubricating boxes —- replacing the old grease cellars —- that needed constant replacing....with hundreds of locos and thousands of grease cellars, the maintenance costs were immense. The adoption of oil cellars, across the whole fleet, allowed inspectors to simply replenish the oil in the cellars that needed it.
You could replenish ALL the cellars ( on a loco)  in less time than it took to change-out one grease block...

Intersetingly, U.P. bought recent loco orders equipped with roller axles.   A very wise approach. 
Because of the superior ability to control the lateral forces, by ‘rolling the later forces’, rather than the simple slamming and pounding of  free end-wise slapping.  Tapered Rollers handle both ‘radial loading’  ( handling the vertical engine weights) AND they handle the lateral thrusts (end-to-end)  by rollingthe vectors to the frame. 

Plain Bearing Side Rods....
The main advantage is lower reciprocating weights, easily changed brass crankpin inserts, lower initial cost and greater lateral flexibility for the axles.

Rollers on crankpins are effective across a whole class of locos, but too costly for the many one-offs, etc.
Roller axles, however, are always to be preferred over play n bearings.  

In today’s world , existing locos riding on plain bearings ( for the drivers) would find the costs to convert the axles is cost-prohibitive...  The truck’s axles sought to be up-graded to today’s AP class axle roller bearings (rotating en-caps).

I recommend continuing the use of plain bearing driver axles... when fitted with separate “electronic temperature-reading monitoring”,  accessible  to the engineer.    There are many affordable schemes to provide temperature monitoring*.     

You want to monitor not the individual axle temperatures, but compare all the axles to ensure that they are reading similar temperatures —— pay attention to axles that are running at markedly higher temperatures than the rest of the drivers on the engine......   the mains often run hotter than the other driver axles...

For  Plsin Bearings:  A crucial lubricant-starved area is the driver hubs and the, fixed, hub-liners (brass) of the driving boxes.   There are many ways to get adequate lubrication to that vital area....

Roller Axles can be made to accommodate lateral shifting of the axles by the inclusion of “lateral motion devices”.... these are ‘surrounds’ with greater free-play between frame and the axle housing.  The unrestricted free motion can exceed the FRA (ICC) allowable un-controlled free-lateral  —— the patented device solution is the use of devices that have springs bearing on the inside faces of the frames.

The centering-springs, on certain axles, control the lateral travel of the axles and 
re-center the axles ( in the frame) upon entering tangent tracks.

As far as I know, certain engines, like the modified J class, do not use lateral-motion devices account the rods cannot accept the necessary slop at the crankpins....they are confined to a very rigid in-line tolerance, which makes for a very long ‘rigid’ wheel base...

Hope this helps...

Wes.

*  Typically,  electronic thermo-couples are fitted to individual axle crown-brasses, then connected to various display schemes...lap-tops, etc...