Virginian Elect., Photo 5

[NW Mailing List]

Robb is exactly right about there being a number of variations on what I'll chose to refer to as the "so-called AAR type B" truck; for example, what was?under a Baldwin (or early FM) versus what went under an Alco.? I confess I was under the impression there was an AAR recommended praction describing both the switcher truck and the road truck, but my reference materials are at home in the States, while I'm currently "down under."



However, without boring everyone?wth the gory details of clearances under a traction motor, the TM very definitely can define the required wheel diameter.? A certain clearance must be maintained under the TM, as well as under?the gear case.? Sometimes it's the TM that governs and sometimes it's the gear case.? Higher speed gearing causes the bull gear to be smaller, which is why E-series locos could be found with 38 in. wheels rather than 40.? But, with the axle-hung "wheelbarrow" way of suspending traction motors, a bigger (i.e. larger diameter) TM could and did define wheel diameter as often as not.

Dave Phelps

-----Original Message-----
From: NW Mailing List <nw-mailing-list at nwhs.org>
To: nw-mailing-list at nwhs.org
Sent: Mon, 31 Mar 2008 6:30 am
Subject: RE: Re: Virginian Elect., Photo 5







> Gordon et all

>  

> These definitely were not standard diesel trucks, they were a GE  design.  

> The standard AAR Type B truck would not take the GE746 traction  motor used on 



> these locomotives.  (The FM "Erie-built" locos used the same  motor in an A1A 

> truck.)  Among other things, the 746 required a 42 in.  (new) diameter wheel.  



> That's one of the reasons the 752 was designed, to  fit a 40 in. wheel which 

> the EMD locos used.  The Alco S-series switchers  and RS-1 used the smaller 

731 

> traction motor, but it would not rate the  horsepower/motor needed for road 

> locomotives that competed with the F-3.   Other earlier road locomotives with 

> GE electrical equipment requiring more  HP/axle had used a predecessor of the 

> 752, but I don't remember (and am not sure  I ever knew) its model number.

>  

> GE also used a smaller version of this B truck on its switching &  industrial 

> locomotives.  The easiest distinguishing spotting feature is the  absence of 

> the elliptical springs used on the AAR Type B truck.

>  

> Dave Phelps




A few notes... there's no such thing as an AAR Type-B (or Type-A) truck, let 
alone a standard one... just like 'Blomberg', they're railfan references to 
various commercial truck builder designs.  There's at least three wheelbase 
variations on the 'standard AAR Type-B', depending on traction motor used, 9' 
4", 9' 6" and 9' 10".  

IIRC, the predecessor to the 752 was the 726... also, 746s didn't require 42" 
wheels (since traction motors drive their respective axle via a gear set, it's 
hard to see how any would require a wheel of a specific diameter)...


 
Robb Fisher
RFDI
________________________________________
NW-Mailing-List at nwhs.org
To change your subscription go to
http://list.nwhs.org/mailman/options/nw-mailing-list
Browse the NW-Mailing-List archives at
http://list.nwhs.org/pipermail/nw-mailing-list/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://six.pairlist.net/pipermail/nw-mailing-list/attachments/20080330/bf895f2b/attachment.html>