Track Standards

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STRR
Posts: 336
Joined: Thu May 24, 2007 9:01 pm
Location: Westminster, CO

Re: Track Standards

Post by STRR » Wed Aug 01, 2018 6:59 pm

When in doubt, seek professional assistance. Doug VanVeelen was a Civil Engineer and authored books on building railroads, particularly hobby sized.

A professional's perspective was mentioned above as the super elevation amount requires careful calculation based on Speed, radius, and weight of loads. This means the super elevation you put in your curves will REQUIRE the same speed and the same load weight every trip. If the super elevation is correct, the load will NOT feel "thrown" out NOR feeling like tipping over inward. Hobby railroads, I say HOBBY as this covers all gauges, do not travel fast enough to warrant super elevation. As discussed above, super elevation without proper speed will cause the riders to lean outward to counteract the tipping inward feeling. This is a natural reaction. When passengers lean because they are uncomfortable, it makes the ride less enjoyable.

Thus, a Civil Engineer recommends little to NO super elevation, based on our speeds, variable load weight, and level of enjoyment.

Good Luck,
Terry

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johnpenn74
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Joined: Tue May 04, 2010 12:54 pm
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Re: Track Standards

Post by johnpenn74 » Thu Aug 02, 2018 11:25 pm

STRR,

True, superelevation is designed with 3 degrees of freedom; speed, radius, mass. Any designed curve (level or superelevated) will have an interelation between speed and mass as the radius is fixed for a given location. The prototype fights this same problem as you can hear speed detectors that will advise trains that they are proceeding too slow for a given curve. My point being that you can't design a curve (level or superelevated) perfect for all situations; little engines, big engine, empty cars, loaded cars, slim passengers, full width passengers... There is NEVER a perfect match up in any circumstance whether the track is level or superelevated. One could look at it statistically and say, this is the best design based on the mean load and mean speed.

Level track is not a solution to this problem as level track in a curve still puts more force on the outer rail than the inside no matter what speed the train is going. This is just simple physics / centripetal acceleration. If built level it WILL deteriorate to negative, its just a matter of how long it takes based on contruction of the track and speeds/forces applied to the rail.

"A centripetal force is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous center of curvature of the path." Wikipedia

Another item to ponder is the verticle height of the center of mass of the rider. I totally agree you COULD build all the track level and the loco and cars will probably handle it just fine. But the riders center of mass, even on a T style riding car is probably 30" from the rail (chest height for males in a sitting position). This really scales the torquing moment of the rider when being accelerated out of the curve. Again, level track does not fix/eliminate this at any speed.

Another way of thinking of it is, the superelevation is there for the rider not the equipment.

I will disagree with Dougs conclusion that superelevation is unnecessary. Based on a little bit of physics and a lot of practical application at the old NGLS track in Atlanta, we had the best running track around because we understood and applied solutions like the prototype. Which, by the way Myself, Rich D and Doug V were all members.

John Pennington
BSIE Georgia Institute of Technology 1999
I have had the thermo, statics, dynamics, physics, deformable bodies, differntial equations, - I can do the math...
John Pennington

Project
2 Mich-Cal Shays
Allen 4-4-0 Narrow Gauge Conversion
Reading A5a Camelback 0-4-0
USRA 0-6-0
Clishay
4 Western Wheeled Scraper NG Dump Cars
N&W 4-8-2
ICM 2-10-2
4 Modern Stake Cars
L&N Caboose
4 Big Four Conversion Gondolas

Like I'm actually gonna build all this stuff :-P

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johnpenn74
Posts: 337
Joined: Tue May 04, 2010 12:54 pm
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Re: Track Standards

Post by johnpenn74 » Thu Aug 02, 2018 11:40 pm

To tell you the truth, I would put in the super elevation because it just looks cool.

JP
John Pennington

Project
2 Mich-Cal Shays
Allen 4-4-0 Narrow Gauge Conversion
Reading A5a Camelback 0-4-0
USRA 0-6-0
Clishay
4 Western Wheeled Scraper NG Dump Cars
N&W 4-8-2
ICM 2-10-2
4 Modern Stake Cars
L&N Caboose
4 Big Four Conversion Gondolas

Like I'm actually gonna build all this stuff :-P

STRR
Posts: 336
Joined: Thu May 24, 2007 9:01 pm
Location: Westminster, CO

Re: Track Standards

Post by STRR » Fri Aug 03, 2018 6:51 pm

John,

You are 100% correct. If a person was to engineer a super elevation for a specific curve (train loaded with passengers), he would have a lot to consider. The end result would be a perfect ride for the passengers under the exact design conditions. Under any other condition, the riders would not get a perfect ride. Good? Maybe, Poor? More likely.

I have read Doug's comments about the NGLS in Atlanta. Very impressive to say the least. A lot of work went into that set up BEFORE it was built. Just as much work went into it as it was being built and continuing upkeep. We'll never know how many people want a ride like you can get there. Are they willing and able to put in the amount of learning and effort to get it? Now's there's the $10,000 question.

Thanks for your input,
Terry

R Paul Carey
Posts: 13
Joined: Sun Sep 06, 2009 7:28 am
Location: Reedville, VA

Re: Track Standards

Post by R Paul Carey » Sun Aug 05, 2018 7:37 am

I have followed this discussion with interest and submit this link, which illustrates a ride taken over my 1-1/2" scale live steam RR through an old-growth forest at my home in Reedville, VA. Track gauge is 7-1/4" and curves are elevated for a scale speed of 45 mph. I am retired from the railroad industry. I typically describe my live steam RR as a "dirt-road" RR "as it was" in the early post-war years - before the ill effects of deferred track maintenance had become apparent (and widespread). It is no coincidence this RR offers a faint resemblance to the geometry of a much-beloved branch line of a certain Eastern Class I road.

The rail is scale 80# and 115# and the ties are cedar, ballast is crusher run and hand tamped. Joints are staggered. The curves have easements (spirals) with appropriate runoff of elevation. At the time of this video, the maximum elevation was 1/2" on one curve. I have since found that a maximum elevation of 1/4" to be entirely satisfactory. The road is not open to the public, although guests are briefed on how to safely enjoy the ride. Elderly or infirm passengers are carried at reduced speed, with no problems or complaints.

My principal reason for introducing elevation is to prevent the undiscovered appearance of reverse elevation in service, an ill effect to which others in this thread allude. Elevation is maintained by use of a truck-mounted clinometer.

The engine in this video is DL&W 988, as she was rebuilt in 1920 with piston valves and Baker valve gear. The video was taken in 2009 with a phone and therefore offers only marginal resolution, but you can readily get the "feel" of the line. In this video, 988, a 4-4-0 (built by the late Frank Desantis) is running in reverse, which was the practice on alternate trips pending completion of a turning loop at the terminal (in 2010) and addition of a 65' (scale) armstrong turntable (in 2012).

https://www.youtube.com/watch?v=WTiWVs_T1Fg

Paul Carey, Reedville, VA.

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