Rural Retreat Depot is open today

[NW Mailing List]

Thanks for the “larger rod hub on #3” comment, Dave - I hadn’t noticed that detail before. I figured the shorter #4 pin was in some way the impetus for the change. And now that’s been clarified as well. 

Time to re-read Giant and see what else I’ve missed / forgotten. 

Matt Goodman
Columbus, Ohio

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On Oct 15, 2022, at 11:31 AM, NW Mailing List <nw-mailing-list at nwhs.org> wrote:


Gordon,
 
Dave explained this in detail. I covered this on page 247 in the Giant book revised edition. With this change, the rod between #3 and #4 wheels were the same as the front single rods. Louis Newton was the one I got this information from and only four J’s were changed. They were change only if stress fractures appeared on #4 four crank pins.
 
Bud Jeffries
 
From: NW-Mailing-List <nw-mailing-list-bounces at nwhs.org> On Behalf Of NW Mailing List via NW-Mailing-List
Sent: Saturday, October 15, 2022 6:19 AM
To: NW Mailing List <nw-mailing-list at nwhs.org>
Cc: NW Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: Rural Retreat Depot is open today
 
Initially, all modern 4-8-4's in the 1940 era that were equipped with roller bearing rods using the so-called tandem rod connection between #2 and #3 axles. In addition, because of this configuration, all of them had relatively long crankpins on #4 axle.  Because all railroads used the same method (tandem rods), this was likely the industry standard for handling the forces that had to be distributed through the running gear, particularly between axles #2 and #3 of a 4-axle engine set.

N&W revised the Class J rods to do away with the tandem rod setup between #2 and #3 driving axle on four locomotives  from about 1952 to 1956.  From a side view, the change can be seen in a much larger rod hub on #3 axle, because one rod bearing must carry the same load that two smaller bearings carried before.  Also the hub on #4 axle is much shorter (the rod is closer to the driver face) which reduced the stresses that were present in the longer crankpin
 
Dave Stephenson
 
 
 
On Friday, October 14, 2022 at 10:41:35 PM EDT, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
 
 
Dave,

Pardon my ignorance, but what is the modification of rods on these four Js?

Gordon Hamilton
 
 
On 10/14/2022 10:29 AM, NW Mailing List via NW-Mailing-List wrote:
The four J's that I have for modified rods were 600, 605, 610, 611.  So with your photo, we've narrowed that to two.  Really does look like 611 in the negative enlargement, but the top part of the second "1" does look a little different  from the top part of the first "1"............  Thanks for posting!!
 
Dave Stephenson
 
 
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