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
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.
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
Hey, your guess is as good as mine! Maybe someone out there knows.
Just guessing also, but maybe it was so interchange rail cars would not fit.
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
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 ?
Two ideas, both probably wrong[;)]
Speculation1[8-|]
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.
Speculation2[:D]
The designers intended the system to be standard gage and goofed.
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.
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.
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.
What are the guages for the NEC, NJT, MNRR, Albany, Michigan, CHI - STL ?
Then what are the freight RRs doing ?
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?
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.
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
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.
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?
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.
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.