Balancing, Counterbalancing and Dynamics

[NW Mailing List]

Gary, did you mean the  ACL  R-1 4-8-4's built by Baldwin that had severe counterbalancing problems?  I don't recall any of the RF&P classes of 4-8-4's (never referred to as Northerns - they were Generals, Governors and Statesmen from Virginia) having such problems.   ??

Ed Painter - Narrows, VA currently living in Russellville, AR

From: nw-mailing-list-bounces at nwhs.org [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Wednesday, March 25, 2009 7:06 PM
To: 'NW Mailing List'
Subject: Balancing, Counterbalancing and Dynamics

Remember that the counterbalancing is not for a STATIC case but a DYNAMIC case with the mass of the drivers and rods included and rotating at different speeds.  In addition there are first mode, second mode, third mode and so on, that is, different dynamic loading per frequency at multiples of the running rpm.  Depending on a bunch of different things, the second, third fourth or other modes might be the most significant loading comparing a dynamic loading situation to a strictly static one.  In reality, you have the rotating drivers plus the oscillating rods moving back and forth and going around the driver pin so those loads are part rotating and part horizontal and vertical loads. Plus the loads from one side are transmitted to the other side and vice-versa.

Thinking about the situation in 'common sense' static balance thinking is pretty far off from what actually happens in a dynamic situation.

In physics or vibration calculations/modeling, this is a complex system requiring some pretty sophisticated analysis.  The Roanoke engineers would have loved to have had a computer to model what they had to estimate with a slide rule.

Part of the issue with the RF&P 4-8-4's and their poor high speed balancing problems were that the published state-of-the-art calculation methods didn't work (1927).  The N&W didn't do the calculations that way for the A and the J.  (The AT&SF engineers didn't follow the published methods either for their high speed locomotives.)

Gary Rolih
Cincinnati ( and a Mechanical Engineer)


________________________________
From: nw-mailing-list-bounces at nwhs.org [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Wednesday, March 25, 2009 3:54 PM
To: NW Mailing List
Subject: Re: Wheel spokes

Very interesting.  I had always assumed that counterweights were centered exactly opposite the pin holding the rods.  While that appears true for the front and middle A drivers, it is obvious from the drawing that it is not true for the main driver.  Would this be because the added weight of the main rod throws the balance off-center?

Sam Putney

----- Original Message -----
From: NW Mailing List<mailto:nw-mailing-list at nwhs.org>
To: NW Mailing List<mailto:nw-mailing-list at nwhs.org>
Sent: Monday, March 23, 2009 8:20 PM
Subject: Re: Wheel spokes

Richard,

I'm surprised no one else has answered this yet. The number is 15.

You can see drawings of the drivers at the following addresses:

Front Driving Wheel http://www.nwhs.org/archivesdb/detail.php?ID=23293
Intermediate Driving Wheel http://www.nwhs.org/archivesdb/detail.php?ID=23187
Main Driving Wheel http://www.nwhs.org/archivesdb/detail.php?ID=23192

Listing of more Class A wheel drawings is at http://www.nwhs.org/archivesdb/listdocs.php?index=rs&id=161&Searchword=wheel

Ron Davis

At 03:15 PM 3/20/2009, you wrote:
Hi chaps
Can somebody tell me the exact number of spokes on a Class A driving wheel, thanks in advance

Regards Richard in UK
________________________________________
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/
________________________________
________________________________________
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/20090326/c87b2d1d/attachment.htm>