Steam & Excursion > Minimum radius curve for Emma Nevada with 144" wheelbase?

What would be the minimum radius curve for a locomotive like 36" gauge 2-6-0 Nevada Central #2 / Emma Nevada with a 144" wheelbase (measured from the centers of the flanged drivers)?

Would those on the forum familiar with narrow gauge operations please weigh in? This is also post on the Narrow Gauge Discussion Forum site.

For comparison of NG minimum radius curves, based on Google Earth measurements:
Durango & Silverton has 220’ balloon track around roundhouse.
Huckleberry RR has 250’ turnaround on their main line west end running Baldwin 4-6-0 and K-27 2-8-2.
Colorado Railroad Museum has 260’ narrow gauge loop.
Knott’s Berry Farm has 190’ curve on main for 2-8-0.
US Gypsum has 250’ radius on wye for modern hoppers and diesels.

Specifically, would 200' minimum radius be sufficient for an operational loop for a 2-6-0 with 144" wheelbase? Why or why not? Thanks.

Tank engine or tender equipped...?

In general, loco builders made tender-equipped locos so that the front corners of the tender would crunch into the cab’s rear wall —-
( startled crew: “ What’s THAT noise??” ) as warning about being in too tight curves, so the crew would avoid derailing BEFORE the flanges popped off the rails.

So, your actual minimum radius is the point at which the tender/loco
combo binds up...

Your results may vary...

W.

Note:
A typical engine,less it’s tender, might take a 25-degree curve easily... but, with tender it may be rated on the spec sheets as “maximum curvature 20-degrees”.

Posted from iPhone

Remember....

As I understand it...

The curve is identified by two points, on the centerline (between the rails) separated by 100ft.

The points are where a cross line to the centerline is drawn, will be the radius when the rails are bent out of line.

If the two 100-ft points (tangent points) have their vertical centerlines equidistance, with no convergence, that straight section of track is called ‘tangent track’.

Now, if the track curves, those vertical lines at the point of tangency (radius lines), have a straight line, at 90-degrees to the vertical line, two tangent-lines will meet halfway between the two tangent points, generally between the rails.

At that mid-point, the included angle ( the most acute) is measured in degrees, as in: a 10-degree curve, a 15-degree curve would be shorter radius, or tighter curve.

To summarize: the tangents, separated by 100 ft., are measured at the point ( between the 100-ft marks) and the acute angle formed by the tangents, is the number of degrees of the curve.

Narrow gauge tracks typically allow much tighter curves, than do standard gauge tracks.

W,

Posted from iPhone

Oooops...duplicated, in error..,w.

Remember....

As I understand it...

The curve is identified by two points, on the centerline (between the rails) separated by 100ft.

The points are where a cross line to the centerline is drawn, will be the radius when the rails are bent out of line.

If the two 100-ft points (tangent points) have their vertical centerlines equidistance, with no convergence, that straight section of track is called ‘tangent track’.

Now, if the track curves, those vertical lines at the point of tangency (radius lines), have a straight line, at 90-degrees to the vertical line, two tangent-lines will meet halfway between the two tangent points, generally between the rails.

At that mid-point, the included angle ( the most acute) is measured in degrees, as in: a 10-degree curve, a 15-degree curve would be shorter radius, or tighter curve.

To summarize: the tangents, separated by 100 ft., are measured at the point ( between the 100-ft marks) and the acute angle formed by the tangents, is the number of degrees of the curve.

Narrow gauge tracks typically allow much tighter curves, than do standard gauge tracks.

W.

Posted from iPhone



Edited 1 time(s). Last edit at 05/21/18 06:34 by wcamp1472.

In other words: on a 20-degree curve the centerline of the track curves thru 20 degrees (is a 20-degree arc of a circle) between two points that are 100 straight-line feet apart.

So curve radius in feet is roughly 5730 divided by the degree of curve.

That works for me!

But out in the field, tromping thru swamps & snakes & off mountainsides to find the center point of a radius.
Could be a real pain in the keister!

W.

Posted from iPhone

Another aspect....
Widening the track gauge, was a common cure for tight curves & longer wheel- bases...

So, if after all your number crunching, you can get more comfortable, by loosening the gauge, a bit.

Remember, too, the wheel treads
are very wide, compared to the rail head. More safety.

W.

Posted from iPhone

You can ask Mike Whistler who is the lead on the restoration of the Emma Nevada at The Orange Empire RR museum. Mike may chime in here on the mimimum Radius for the Emma Nevada. Interesting that this is posted here, as there was a gentle man measuring the wheel base of the Emma a few weeks ago when I was out there.



Edited 2 time(s). Last edit at 05/21/18 08:35 by czuleget.

I've never crunched the tender and cab together on 1522 but was going through a tight curve in KC at an interchange and the safety chain in the gangway snapped. Sounded like a 12 GA shotgun and scared the crap out of us. If we got into a really tight curve situation, the inside of the trailing truck would actually rub the tail of the frame. Diagram says she will do a 20 degree curve. I wouldn't want to try that.

My 1921 Field Manual for Railroad Engineers offers many solutions to laying out curves, tangents and spirals. While building a 1/3 mile railroad for "310 to Yuma" I used the offset method to lay out the RR.

After walking the general location the Director and Production Designer wanted the railroad to be in I worked with a construction crew member who set up a transit at the endpoint of a selected tangent. I became the field man and took the 100' chain to extend the tangent and drove a stake. The transit was then swung 13 degrees to the right and I lined the rod and chain with the transit and drove another stake. This process was repeated to the end of the curve. where another tangent was established.
I created a poorman's spiral by starting the curves with an 18 inch offset.

Pic 1 shows the finished grade at the east end of the RR. This is a 16 degree curve.

Pic 2 shows the finished grade and track laying in process on the 13 degree curve by the station and water tank. Both curves had the gauge relieved by 1/2 inch.

Pic 3 1/18/2007, the day after filming wrapped we made one last run before dropping the fire, draining the boiler and loading everything up to go back to Reader, Arkansas.
The movie is supposed to take place during a drought. It's obvious from the snow that we were in anything but. The reason the railroad was placed where it was, was to create a visual for a scene where the train's arrival could be seen from the hotel room where the hero's were staying. The 38 inch snow fall from December 28 to January 1 forced the Director to completely change his shots. Instead of a big view from a crane everything had to be shot from the ground with any remaining now hauled off or covered up.

If you watch the end of the movie you can see snow in some of the shots. After the storm it became very cold. It was -13F during several nights while we were shooting. The night hostler had is hands full keeping the engine hot.

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I should have mentioned the maximum grade was 1.5%.

Degree of Curvature is the angle the track changes in direction over the length of track measured by a 100 foot chord along the track route.

The angle may be measured either at the point of intersection of the two tangent tracks at each end of the chord, or as the central angle of the radius lines at each end of the chord.

The actual centerpoint of the tracks curve, and the radius lines, are never actually located and staked, it is entirely theoretical.

The drawing below illustrates a 30 degree curve.

px320 wrote:
> After walking the general location the Director and Production Designer wanted the railroad to be in I worked with a construction crew member who set up a transit at the endpoint of a selected tangent. I became the field man and took the 100' chain to extend the tangent and drove a stake. The transit was then swung 13 degrees to the right and I lined the rod and chain with the transit and drove another stake. This process was repeated to the end of the curve. where another tangent was established.
>

This would give you a 26 degree curve.


-John



Edited 1 time(s). Last edit at 05/21/18 15:23 by LarryDoyle.

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Per above....

“At that mid-point, the included angle ( the most
> acute) is measured in degrees, as in: a 10-degree
> curve, a 15-degree curve would be shorter radius,
> or tighter curve.”
W. Camp

Angle PC, PI, PT. = Angle PC, C, PT

Q.E.D.


W.

I love the third photo! Thanks for sharing. It looks so wild west.

Victor A. Baird
http://www.erstwhilepublications.com



Edited 1 time(s). Last edit at 05/22/18 14:01 by wabash2800.

Given the movie was set in the 1870's. the track was laid without tie plates, with dirt ballast peaked in the center to the top of the tie, then tapered to half the height of the tie at the tie ends. The Art Dept. wanted to use hewn ties for greater realism, but the cost per tie would have blown the budget.

Pic 1- this is what the station set looked like 3 days after the big snow. We spent 5 days digging everything out. I had trucks with locomotive and cars stuck in truck stops across Texas and New Mexico because of icy road conditions.

Pic 2 = the Production Co. had built and were rebuilding 44 buildings on Roed Ranch, near Galisteo, NM. This was the movie set that was burnt down during the filming of Wild Wild West a few years earlier. The unfinished buildings were left that way because the snow cleanup caused production delays that added $20 million to the cost of the film.

It was still a good movie.

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To get back to the original question in this thread, Reader 2-6-0 No. 2 is a 1913 Baldwin product with almost identical stats as 1875 V. & T. 2-6-0 No. 13 Empire.
The V. & T. had curves as sharp as 22 degrees. The Reader has a wye nearly as sharp. I would expect a narrow gauge engine would have a similar capability.

For what it's worth, all Amtrak approved passenger cars must demonstrate the ability to negotiate a 22 degree curve.

Let's look at curvature from a slightly different point of view. Laying out a curve involves the deflection angle from tangent along a 100 foot chord. I'll leave that one alone for now and discuss measuring an existing curve and how it may relate to minimum curvature for a rigid wheelbase locomotive.

A simple, and rather accurate method of determining degree of curvature is to measure the mid-ordinate of a 62 foot chord. In other words, take a string 62 feet long and stretch it along the inside of the low rail 5/8" below the head of the rail (you could use the high rail, but it may be a bit worn). At the mid-point, or 31 feet, measure the distance from the string (chord) to the rail. The distance in inches equals the degree of curvature.

How does this apply to minimum curvature for a locomotive? You'll need to take into account the rigid wheelbase (in this case 144") and the lateral motion of the drivers as well as the wheel tread width and the rail head width.

Breaking it down, for a 144" wheelbase on a 20 degree curve (287.94' radius)you're looking at about 3/4 of an inch (0.0625 feet) at the mid-point of the chord for the wheelbase. In other words, the middle driver will be about 1 inch inside the other two drivers on the curve. For a 30 degree curve (193.19 feet radius), the distance is about 1 1/8 inches (0.932 feet). 1 inch equals 0.083 feet.

I don't know the mechanical details of the Emma Nevada, you'll have to field check the numbers, but hopefully this gives you a starting point.

Tim