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Steam Locomotive Driver Quatering
165thspc
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Posted: Tuesday, September 24, 2019 - 12:40 AM UTC
I am currently working on a static model of a steam locomotive and came to the question of quartering the drivers. No information was given in the instructions as to this question but I already knew the the drivers on one side would be a quarter revolution (90 degrees) out of sync with the opposite side. However which side would "lead" in this arrangement I did not know.

What follows are excerpts from various other blogs that I observed online.

Cheers
165thspc
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Posted: Tuesday, September 24, 2019 - 12:43 AM UTC
From a blog sponsored by TRAINS Magazine:

[quote] I am curious about a few aspects of steam locos and the way their drivers were quartered. I understand that the left and right drivers were out of sync, usually by 90 degrees. Was there any preference or rule of thumb for which side led - was 90 degrees ahead of the other? I have heard that some locos were run with a closer quartering - I have heard 80 degrees was used. What are the potential or imagined benefits of such an arangement? Finally, was there any effort to synchronize the quartering of the front and rear drivers on a Mallet? I can't imagine that there was due to the possibility of slipping one set but not the other, but I have been wrong before.

Thanks in advance for any replies! [quote]
165thspc
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Posted: Tuesday, September 24, 2019 - 12:44 AM UTC
Again from TRAINS Magazine:

[quote] Two cylinder locomotives always used 90-degree quartering; with this arrangement, the power pulses were more even than they would be with any other setting. They weren't perfect, but as good as could be gotten.

Most railroads had the right side crankpins leading the left. In other words, when the right rods were at their lowest point (the "bottom quarter") the left side was on front dead center. The Pennsylvania was the biggest user of left-hand lead locomotives. Someone theorized that it was because PRR had so much multiple-track territory; the most solid part of a multiple-track roadbed is toward the center, and since the side of a locomotive that has the lead is the side that pounds the track hardest, PRR wanted the locomotive to pound the most solid part of the roadbed - the left hand side.

Three-cylinder simple locomotives had the crankpins 120 degrees apart; the setting of the inside cylinder couldn't be seen, but the two outside cranks were 120 degrees apart and the inside one 120 degrees from each.

Baldwin built an experimental three-cylinder compound 4-10-2 in which the driving wheels were quartered with left-hand lead. The center cylinder was the high-pressure cylinder and its crank was 135 degrees from the outside cranks. This locomotive exists today at the Franklin Institute in Philadelphia.

There was never any effort made to synchronize the two engines of either a Mallet or a Simple Articulated or a Duplex-drive locomotive. In simple articulateds and duplexes it was thought beneficial in some quarters if the drivers of one engine were a fraction of an inch different from those of the other so the engines wouldn't get into synch.

Old Timer [quote]
165thspc
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Posted: Tuesday, September 24, 2019 - 12:46 AM UTC
Again from TRAINS Magazine:

[quote] On compounds, they tended to stay reasonably close to sync because the exhaust from one engine fed the other engines. If the rear engine slipped, the back pressure from exhausting steam faster than the lead engine could use it would stop the slipping. If the lead engine slipped, the lack of steam from the rear engine would do the same.[quote]
165thspc
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Posted: Tuesday, September 24, 2019 - 01:12 AM UTC
From Portlines Hobbies:

The original A.C. Gilbert service manual instructions for quartering repaired model locomotives.

http://www.portlines.com/portlinesclinic29.htm
165thspc
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Posted: Tuesday, September 24, 2019 - 01:29 AM UTC
Some images that may offer clarity (or may simply add to the confusion!)

Images reproduced here fo discussion purposes only.



__________________________________________


165thspc
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Posted: Wednesday, September 25, 2019 - 12:10 AM UTC
That second drawing does illustrate quartering but primarily speaks to an aspect I never realized regarding locomotive design: Namely that the counterweights on steam locomotive drivers appear to be slightly advanced beyond strictly 180 degrees opposite the dynamic load they are intended to offset.

I would assume this was only done on large high speed road engines. It seems to me that switchers and any engine intended to regularly operate in both directions and at slow speeds would have their counterweights set at exactly 180 degrees.
JClapp
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Posted: Wednesday, September 25, 2019 - 05:17 AM UTC

Quoted Text

That second drawing does illustrate quartering but primarily speaks to an aspect I never realized regarding locomotive design: Namely that the counterweights on steam locomotive drivers appear to be slightly advanced beyond strictly 180 degrees opposite the dynamic load they are intended to offset.

I would assume this was only done on large high speed road engines. It seems to me that switchers and any engine intended to regularly operate in both directions and at slow speeds would have their counterweights set at exactly 180 degrees.



not necessarily, counterweighting the drivers is quite complicated - good insight in this discussion.
165thspc
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Posted: Wednesday, September 25, 2019 - 04:24 PM UTC
Very interesting blog exchange on the subject, thanks Jonathan.

Never saw drivers with holes drilled in the front face before (or at least never noticed before) but I always assumed there might be shallow holes drilled or gouged in the rear face to fine tune the balance of the drivers. Much like the the small counterweights used to balance auto tires.
JPTRR
Staff MemberManaging Editor
RAILROAD MODELING
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Posted: Tuesday, October 08, 2019 - 01:26 PM UTC
Mike,

Thanks for starting this. I am trying to learn about quartering.
165thspc
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Posted: Tuesday, October 08, 2019 - 03:42 PM UTC
As I say I am building a static model and while I know a fair amount about quartering I had wondered which side would be in the "lead". The Trains article I came across, I think, gives us all the information a model builder might need on the subject.
165thspc
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Posted: Wednesday, October 09, 2019 - 11:03 AM UTC
Interesting animation on a related topic: Steam Locomotive Reversing & Adjusting the Cut-Off.

http://trumpetb.net/loco/rodsr.html

165thspc
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Posted: Thursday, October 10, 2019 - 02:48 AM UTC
Engineer's (Right) Side of locomotive, shown with "rods full down". This is the leading side of most steam engines.



Fireman's (Left) Side of Locomotive, shown "following" the right side by 90 degrees: