Track gauge of Washington Metro 4' 8 1/4"--why?

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Track gauge of Washington Metro 4' 8 1/4"--why?
Posted by 7j43k on Sunday, June 18, 2017 3:44 PM

That about sums up my question.  I have taken a bit of time to find an answer, and can't.  So I thought I'd ask here.

 

Thanks,

 

Ed

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Posted by Firelock76 on Sunday, June 18, 2017 3:56 PM

I can't think of a logical reason, so I'll take a wild guess...

In the old days some trolley and interurban lines used oddball gauges to keep conventional railroads from trying to interchange or run their freight cars on them.  Remember, some of those trolley and interurbans ran some freight themselves.  Aside from that I can't think of a reason for 4' 81/4' inches instead of 4' 81/2".  Maybe DC Metro was carrying on the tradition?

Depending on what part of the country you were in "way back when" quite often there was bad blood between the steam railroads and the trolley/interurban lines.  The steam roads didn't like the upstart competition, especially from the interurbans.

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Posted by 7j43k on Sunday, June 18, 2017 4:10 PM

Just kinda staring up at the ceiling, I thought of this possibility:

 

They wanted to use standard gauge wheel sets.  Off the shelf stuff.  Get it anywhere.

BUT.

They figured they would be running a tighter, more precise operation.  So they could squeeze the rails in 1/8" per side, and standard sets would still work.  They'd just run to tighter tolerances.  And I presume there would be some benefit to that.  Maybe less noise, maybe less truck hunting.........

Keep in mind that 4' 8 1/2" track gauge all over North America is designed to accept just about ANY railroad car from anywhere.  Hence tolerances might need to be a wee bit loose.  But Metro controls all the rolling stock on their railroad.  And they don't have to interchange cars.

It's a thought.  Might even be right.  Is it?

 

Ed

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Posted by Firelock76 on Sunday, June 18, 2017 4:15 PM

Hey, your guess is as good as mine!  Maybe someone out there knows.

Lab
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Posted by Lab on Sunday, June 18, 2017 6:40 PM

Just guessing also, but maybe it was so interchange rail cars would not fit.

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Posted by 7j43k on Sunday, June 18, 2017 7:05 PM

Everyone knows what track gauge is.  But tracking down wheel gauge is a bit tougher.  For me.

I did find this chart:

 

 

It is obviously for large scale models.  But there is a Prototype dimension line at the top, which should be kinda close.  I hope.

Anyway, the wheel gauge is 55.69".  Standard track gauge is 56.5".  And Metro track gauge is 56.25".

It looks to me that shrinking the track gauge by a quarter-inch would still allow standard gauge wheels to fit the slightly narrower gauge.

Again, I'm kind of new at this.  I hope someone "who knows stuff" will contribute.

 

 

Ed

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Posted by blue streak 1 on Sunday, June 18, 2017 7:58 PM

Any chance that the difference in track guage could have inadvertenly had RR standard wheel guage causing some derailments ?  That in case the wider wheel guage on narrower WASH Metro ?

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Posted by DSchmitt on Sunday, June 18, 2017 9:16 PM

Two ideas, both probably wrongWink

Speculation1Geeked

With wear the track gage will widen overtime requiring regaging. In Railway Track and Maintenance by Tratman it says that widening by 1/4" on tangents and 1/2" on curves is acceptable before regaging is necessary.  On 4'8-1/2 gage track reguaging would be need on tangents at 4'8-3/4"and curves at 4'9".  

I doubt 4'8-1/4" gage would preclude the use of wheel components  which could run on the widened standard gage.  Perhaps by starting with a slightly narrower gage they increase the time interval between regaging. 

Speculation2Big Smile

The designers intended the system to be standard gage and goofed. 

I tried to sell my two cents worth, but no one would give me a plug nickel for it.

I don't have a leg to stand on.

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Posted by erikem on Sunday, June 18, 2017 10:45 PM

Back in the late 60's there were a few reports of RR's tightening track gauge to 4"8-1/4" as steam locomotives were no longer being operated. Claimed benefit was better riding as the gauge faces of the track were closer to the fillets on the wheel.

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Posted by daveklepper on Monday, June 19, 2017 3:29 AM

Remember that on well-maintained track with well-maintaned rolling-stock, the wheel taper is supposed to prevent hunting and prevent the flanges from scraping against the inside rail face.  So the wheel gauge, between the flanges' outside faces adjoing the tread, has always been narrorer than the rail gauge. But the North Shore and some othe interurban and many transit properties used and use wheels with little or no taper.  Be interesting to know what taper if any this system uses. 

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Posted by DS4-4-1000 on Monday, June 19, 2017 7:26 AM

The PRR used two track gauges depending on what was the primary traffic on that set of rails.  For track that was heavily used by passenger trains the gauge of 4' 8 1/4" was used to give a smoother ride.  For track that was primarily freight the gauge of 4' 9" was used to reduce friction.

So I expect that the Metro selected its gauge to give a smoother ride.

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Posted by blue streak 1 on Monday, June 19, 2017 1:00 PM

What are the guages for the NEC, NJT, MNRR, Albany, Michigan, CHI - STL ?

Then what are the freight RRs doing ?

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Posted by CandOforprogress2 on Monday, June 19, 2017 1:16 PM

Cleveland RTA used MOW equipement that is interchanged with Norfolk Southern at there yard on E 55. The problem here with Pennsyvania Trolley Gauge and the Metro is how do you retrofit contract MOW maintace equipment?

 

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Posted by NittanyLion on Monday, June 19, 2017 1:49 PM

Lab

Just guessing also, but maybe it was so interchange rail cars would not fit.

 

Zero percent chance of that.  Why? Because Metro *did* have an interchange with the Southern in Alexandria during construction.  The remains of connection are still there in the weeds and bushes, but long ago severed. 

I don't know for a fact, but I'm reasonably sure The Great Society Subway would have an answer, if there even is one.

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Posted by 7j43k on Monday, June 19, 2017 3:19 PM

Thank you, all, for you answers.

I was exposed many years ago to "gauge conspiracy", wherein non-standard track gauges are chose to limit interchangeability.  In that early case, the reason BART chose wide gauge was to preclude any standard/typical rolling stock from using their trackage.  True or not, I don't know.  Just reporting what someone else firmly believed.

So I've been a bit sensitive to that possiblity ever since.  Which thus came up as a possible explanation for the Metro 1/4" variation.

What appears to be the true reason for the Metro-quarter came to me after posting the question here--a little meditation time.

So I've had a chance to learn a little bit more about the workings of flanged wheels on rails.  A VERY clever invention.

 

Thanks again,

 

Ed

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Posted by bartman-tn on Monday, June 19, 2017 5:05 PM

1/4" makes no real difference in the gage of a railroad. The track gage for railroads start with a minimum of 4' 8", and then have a maximum based upon the track class. Track classes 4 and 5 have a maximum gage of 4' 9-1/2",  class 2 and 3 is 4' 9-3/4", and class 1 is 4' 10". As long as the gage is between the minimum and maximum, it is fine.

Some railroads go with a slight narrower gage than the design gage (4' 8-1/2") to prevent wheel hunting. This can provide a slightly smoother ride if the alinement is correct.

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Posted by MidlandMike on Monday, June 19, 2017 7:47 PM

blue streak 1

What are the guages for the NEC, NJT, MNRR, Albany, Michigan, CHI - STL ?

Then what are the freight RRs doing ?

 

CHI-STL is owned by UP, and they expressed the possibility of using the line more now that it is improved.

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Posted by Deggesty on Monday, June 19, 2017 9:15 PM

MidlandMike

 

 
blue streak 1

What are the guages for the NEC, NJT, MNRR, Albany, Michigan, CHI - STL ?

Then what are the freight RRs doing ?

 

 

 

CHI-STL is owned by UP, and they expressed the possibility of using the line more now that it is improved.

 

You do refer to the former Alton and not the former C&EI-Big Four, do you not?

Johnny

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Posted by CSSHEGEWISCH on Tuesday, June 20, 2017 6:52 AM

The Joliet-Alton portion is owned by UP, the Chicago-Joliet portion is owned by CN, the Alton-St. Louis section may be TRRA trackage, I'm not sure about that.  The jumbled ownership is fallout from the sale of that line by IC to Chicago, Missouri & Western.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by oltmannd on Tuesday, June 20, 2017 8:30 AM

From a practical standpoint, you can still use standard axles and wheels, you'd just press them on a fraction more.

The real mystery question is why DC Metro didn't use standard platform height. It keeps them from buying industry standard undercar equipment.

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by daveklepper on Tuesday, June 20, 2017 3:12 PM

I can answer the last question.  Lower tunnel height and less construction cost than has been standard for North American subways.  Russ Jackson said:

The cement pourers designed the cars.

Lower floors also mean lower ceilings.  The lower construction costs have meant higher equipment first costs and maintenance costs.

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Posted by Firelock76 on Tuesday, June 20, 2017 5:58 PM

If anyone knew I figured David would know!

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Posted by MidlandMike on Tuesday, June 20, 2017 6:52 PM

Deggesty

 

 

 

CHI-STL is owned by UP, and they expressed the possibility of using the line more now that it is improved.

 

 

 

You do refer to the former Alton and not the former C&EI-Big Four, do you not?

 

Yes, the former Alton that is being upgraded by ATK.

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Posted by Buslist on Wednesday, June 21, 2017 11:25 AM

MidlandMike

 

 
Deggesty

 

 

 

CHI-STL is owned by UP, and they expressed the possibility of using the line more now that it is improved.

 

 

 

You do refer to the former Alton and not the former C&EI-Big Four, do you not?

 

 

 

Yes, the former Alton that is being upgraded by ATK.

 

Actually it's being upgraded at IDOTs expense by UP forces.

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Posted by oltmannd on Wednesday, June 21, 2017 5:35 PM

daveklepper

I can answer the last question.  Lower tunnel height and less construction cost than has been standard for North American subways.  Russ Jackson said:

The cement pourers designed the cars.

Lower floors also mean lower ceilings.  The lower construction costs have meant higher equipment first costs and maintenance costs.

 

Ugh!  I guess they thought a large fleet of cars would be enough to smear the equipment design costs out.  

 

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by feltonhill on Thursday, June 22, 2017 2:58 PM

I worked for Metro's engineering consulting firm (DeLeuw Cather) in the late 1970s, and the reason of the gauge difference was to complement the cylindrical wheel profile used on the subway cars.  They didn't have the conventional 1:20 or 1:40 taper.  The tighter gauge would reduce the amount of truck "hunting" with this configuration.   It seemed to work OK, but the cars were noisy going around sharp curves, and I don't mean flange squeal!  There was a lower pitch sound that could have been caused by microslip of the inside wheels.  Normal wheel taper takes care of this problem.

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Posted by Firelock76 on Thursday, June 22, 2017 6:05 PM

Hey Feltonhill, you're back!  Don't stay away so long!  Lady Firestorm says "hi" as well!

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Posted by richg1998 on Friday, June 23, 2017 1:50 PM

I did find a discussion in railroad.net and someone said, The gauge broadens in curves slightly based on the radii.

Alittle more info if you go look. There was something about rail grinding.

Rich

N

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Posted by feltonhill on Friday, June 23, 2017 4:57 PM

Firelock,

I've just been lurking more than contributing lately.  The DC subway was one area that I had some first-hand experience that may help answer the initial question.

Thanks for noticing!!

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Posted by oltmannd on Friday, June 23, 2017 7:59 PM

feltonhill

I worked for Metro's engineering consulting firm (DeLeuw Cather) in the late 1970s, and the reason of the gauge difference was to complement the cylindrical wheel profile used on the subway cars.  They didn't have the conventional 1:20 or 1:40 taper.  The tighter gauge would reduce the amount of truck "hunting" with this configuration.   It seemed to work OK, but the cars were noisy going around sharp curves, and I don't mean flange squeal!  There was a lower pitch sound that could have been caused by microslip of the inside wheels.  Normal wheel taper takes care of this problem.

 

Wow.  Great info!  Cylindrical wheels for only 75 mph operation.  I would have though 1:40 would be okay.  The cars are long enough they shouldn't have had hunting problems...

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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