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Super elevation on s curves?

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  • From: somerset, nj
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Posted by gregc on Tuesday, August 20, 2019 4:06 PM

Don't flanges rubbing create additional resistance?   doesn't this cost fuel if every wheel on a long freight train is rubbing?   

isn't it more diffcult to get a long train started if the flanges are rubbing?

greg - Philadelphia & Reading / Reading

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Posted by rrinker on Wednesday, August 21, 2019 12:10 PM

 Part of what flange greasers are for.

And as a couple of real railroaders are sayiong - stopping the train short of striking another train is WAY WAY further up the priority list than any extra difficulty of starting it on a curve.

With exaggerated superelevation and far tighter than typical prototype curves in our models, it's far more likely for models to have issues starting on curves. However, saying that, short of REALLY coars handling of the throttle or sudden power failures and then having the power come back on before being able to turn the throttle down, I have never had a problem with stringlining trains starting them on curves, even with light (under NMRA weight) cars in the middle. 

 The tilt to the track makes the cars want to slide down the hill, but the conical section of the wheels makes this also need to lift the car to happen - I'd postulate there's more side thrust on the axle bearings than there is on the flange against the inside rail. Picturing it in your head, and also photos taken with long lenses, make the real track seem to curve much sharper than it really is. On a rela mainline curve, it's unlikley you can even see the deflection over a typical truck wheelbase - probably not even over a full car length, so the force of a flange against the rail should be minimal, if it even strikes the rail. On a really tight cirve on a siding, where it might evn be difficult to push a single car due to coupler swing issues, there the rails may be curved so sharply that the flanges are rubbing the inside of the rail.

                              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by gregc on Wednesday, August 21, 2019 1:50 PM

rrinker
And as a couple of real railroaders are sayiong - stopping the train short of striking another train is WAY WAY further up the priority list than any extra difficulty of starting it on a curve.

airplanes are expected to land on a runway, but are designed to land on farm fields (at least general aviation aircrafts).  of course you don't design trains to only do what is expected. 

rrinker
I'd postulate there's more side thrust on the axle bearings than there is on the flange against the inside rail.

forces need to balance

rrinker
so the force of a flange against the rail should be minimal, if it even strikes the rail.

is "minimal" less than typical rolling resistance (2.3lb/ton at 10mph)?

i think the force is proportional to the elevation / Gauge.   Then you need to account for the coef of friction of steel on steel (~25%).  

 

 

Since a train traversing a heavily superelevated curve at a relatively slow speed tends to cause excessive wear on the low rail, many railroads reduced curve superelevation when their passenger trains disappeared. This practice has worked against the reinstatement or speeding up of passenger service. 

sounds like it's undersirable to run slow or stop on superelevated curves, but not unexpected.

greg - Philadelphia & Reading / Reading

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Posted by dehusman on Wednesday, August 21, 2019 4:08 PM

The superelevation is a fixed amount, its set for one speed.

The trains may be going different speeds.  A piggyback or perishable train might have a top speed of 70 mph, a regular freight train 60 mph and a coal train 50 mph.  Whatever speed you pick it will be non-optimal for some or all of them.  Somebody's going to have to brake to go through the curve or will be going through slower than the superelevation speed.  Any way you cut it, its going to cost time, fuel, and extra wear on brakes or rail on some of the trains.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by riogrande5761 on Thursday, August 22, 2019 7:36 AM

doctorwayne

 

 

 

Eek, no guard rails and a long drop adjacent to the track.  You are much braver than I.

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by doctorwayne on Thursday, August 22, 2019 11:06 AM

riogrande5761
Eek, no guard rails and a long drop adjacent to the track. You are much braver than I.

Yeah, but once I get the landforms for the scenery in place, it'll halve the risk.  I finally have the material on-hand, just need to find time to put it in place.

riogrande5761
....If my track is near the edge, I try to create some sort of barrier to prevent trains from going over the edge, either by landscape or a wall using hardbard (yard).....

From the photos in your post in the "Close to the Edge" thread in General Discussion, it looks as if you've got all the safety measures needed using the same excellent scenery method that Rob Spangler uses.

In my case, I lost much of my semi-planned layout room (about 1200 sq.ft.) to "other family considerations", resulting in a "what-will-fit-in-this-space?"....

...type of layout.

The peninsula between South Cayuga and the town now above Elfrida was the best way to add a partial second level, with the close-to-the-edge-track the method to gain the needed height.

In use, it's not all that scary, as train speed is quite low (the grade, uncompensated, is 2.8%) and I use a walk-around throttle so that I can follow alongside the loco(s). 

It's also my opinion that pretty-well anything used on the layout can be repaired.

The only incident of any consequence on that track occurred on the high bridge in the photo below...

It's near the start of the grade, on the outskirts of South Cayuga, and involved a fairly long train - perhaps 40 or 50 cars...much more than is usual.  As far as I could tell, a low coupler caught on something, perhaps the guardrail on the bridge, causing some of the cars between it and the locos to stringline.

Here's the aftermath...

Clean-up and repairs were quickly accomplished and the train re-run, just to ensure it could be done safely.  At that time, the partial upper level hadn't been built, so the train had to stop at the top of the grade, then back down.

Wayne

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Posted by riogrande5761 on Friday, August 23, 2019 12:21 PM

doctorwayne
doctorwayne wrote the following post yesterday:

Yeah, but once I get the landforms for the scenery in place, it'll halve the risk.  I finally have the material on-hand, just need to find time to put it in place.

I resisted running trains until enough things like scenery was in place or other safeguards.  In some cases, a scenery shell may not be such that will block rolling stock from going over, depending on the terrain and landscape.

From the photos in your post in the "Close to the Edge" thread in General Discussion, it looks as if you've got all the safety measures needed using the same excellent scenery method that Rob Spangler uses.

I do not on Rob's layout, there appeared to be areas that rolling stock could dive off the edge.  As far as scenery methods, I like to follow much of what Rob does because of a couple of reasons, it looks nice and it is somewhat similar (vegetation wise) to parts of the D&RGW on the west end.  And D&RGW and WP interchanged freight trains too.

Rio Grande.  The Action Road  - Focus 1977-1983

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