Old Fat RobertThe track charts you mentioned in your reply would not generally be available to the public, would they?
The ones I was refering to are in the book "N&W Clinch Valley Line".
You can find it here:
http://www.nwhs.org/commissary/Books-Others.html
The track charts are available here:
http://www.multimodalways.org/archives/rrs/NS/NS%20Track%20Charts/NS%20Track%20Charts.html
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
Carl425: I asked the question in an attempt to learn more about (model) railroading. For me, it is a 2.5% grade. And when a casual visitor inquires about the grade that would be the answer. If you or Tony Koester visited my layout, I would hope to be able to supply you with a more complete answer. Thank you for your response. The track charts you mentioned in your reply would not generally be available to the public, would they?
Thanks again
Old Fat Robert
Old Fat Robert So, here is the question that comes to my mind. Do we "report" the effective grade on these curves to include the 32/R figure or merely go with the rise/run mathmatics. I have some 26 in. radius curves that by rise/run figures are at 2.5% grade . Should I be explaining to visitors that on those curves we are really looking at 3.73%? This is a significant difference and it would (it seems) matter greatly to those among us that are really in to the details of the hobby.
So, here is the question that comes to my mind. Do we "report" the effective grade on these curves to include the 32/R figure or merely go with the rise/run mathmatics. I have some 26 in. radius curves that by rise/run figures are at 2.5% grade . Should I be explaining to visitors that on those curves we are really looking at 3.73%? This is a significant difference and it would (it seems) matter greatly to those among us that are really in to the details of the hobby.
Why not report both the actual physical grade and the effective grade? Could be a learning opportunity for your guests. Model railroaders will recognize the difference right off. But before you print signs/labels and whatnot, you might want to wait just a little while. As reported eariler in this thread (and perhaps elsewhere as well), the LDSIG is conducting experiments to gather some data to see if the 32/R number still holds up.
Robert (Middle Age and a Little Plump)
LINK to SNSR Blog
If you are worried about stringlining, why would you add super elevation and compound the problem?
Old Fat RobertDo we "report" the effective grade on these curves to include the 32/R figure or merely go with the rise/run mathmatics.
The N&W track charts that are printed in the books I have account for the grade and degree of curvature for every foot of track on the line. Since the railroad (at least the one I know about) reports them separately, why wouldn't we do the same? So you have a 2.5% grade on a 26" radius curve - unless you want to convert the radius to degrees like the prototype.
Grades plus a curve can be a problem. The LDSig 32/R is very good. I have a railway engineering book that states that every 'degree' of curveature adds another .05% effective grade. A 22" radius curve in HO is about a 40 degree curve. This adds another 2% to the effective grade - for a total of 5%! I think the 'bite' of our soft metal wheels/rail provide a little extra traction.
My old layout had a 2.7% grade that ended with about 270 degrees(3/4ths of a complete circle) of curvature at the summit. A P2K GP9 was limited to about 7-8 NMRA weighted cars on the 'hill'. Double heading a 12-15 car train was standard practice.
At our club, we have a 4.5 turn helix that is double tracked(33"/36" radius). My BLI USRA Heavy 2-8-2's will pull 15-20 cars up that 2.2% curving grade.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Hello all,
On my pike I have a 3% grade on a curve that begins with a 22-inch radius and ends with an 18-inch radius.
The only problems I have encountered are the transitions from flat to grade on both ends.
The smoother the transition the better running.
As far as super elevation, this grade is flat (no super elevation) where the other curves on my pike are super elevated.
Because of the tight curves on my pike; minimum 15-inch radius and #2 turnouts, I only run 4-axle diesels, 0-6-0 steamers and rolling stock limited to 50-feet.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
I want to thank each of you for your reply. I appreciate each of you taking the time and making the effort. I have learned a lot! Now my son and I will digest all of your comments and make a decissionas as to what we will do.
carl425 ROBERT PETRICK I hope you interpret this as a friendly discussion.
ROBERT PETRICK I hope you interpret this as a friendly discussion.
Okay, good. Agreed.
Here's a link to what looks like a general power-point sort of presentation. I found it quickly online and haven't verified the contents, but I have no reason to believe any of it is wrong or out-of-date. Lot of stuff regarding horizontal and vertical geometry, including superelevation. Interesting to me, but I realize others might not get so excited about it.
Robert
http://www.engr.uky.edu/~jrose/RailwayIntro/Modules/Module%206%20Railway%20Alignment%20Design%20and%20Geometry%20REES%202010.pdf
ROBERT PETRICKI hope you interpret this as a friendly discussion.
Absolutely.
I'm looking at a track chart for the locations where these pictures were taken. "Authorized Freight Speed" per the chart is 20 MPH through most of this area. A few short sections are 25. I have no idea how to reconcile the rules of physics with the rules of the railroad.
BTW, these pictures are linked from railpictures.net. In case you're not familiar with it, t's an awsome site.
Hey Carl
First off, nice photos.
Second off, I hate doing math when I don't have to.
Third off, photos are hard to interpret.
Fourth off, we need to make some assumptions.
Superelevation depends on the degree of curvature of the track and the suspension of the equipment travelling. Assuming that is a 2 degree curve, then the required superelevation of the outer rail for 25 MPH would be about 5/8". Assuming that the actual elevation of the outer rail is 3" above the inner rail (based on eyeball estimation from photo), then the maximum speed would work out to about 57 or 58 MPH. Of course, photos and eyeballs can be innacurate.
I hope you interpret this as a friendly discussion. I don't want to seem like a smart ass. Plus, I could be wrong entirely.
ROBERT PETRICKIf your speed limit is low (and 30 MPH could be considered low), then super-elevation is not necessary.
This track has a 20 MPH limit
This one too
doctorwayne I superelevated all of my mainline curves (mostly 34" or larger radii and mostly on 2.5% grades), but it's strictly cosmetic. Most speed limits are under 30mph, and the highest, even on straightaways, is 45mph. Never a problem with stringlining, even on trains much longer than those normally run. Wayne
I superelevated all of my mainline curves (mostly 34" or larger radii and mostly on 2.5% grades), but it's strictly cosmetic. Most speed limits are under 30mph, and the highest, even on straightaways, is 45mph. Never a problem with stringlining, even on trains much longer than those normally run.
Wayne
The reason tracks (or highways) are super-elevated is to counter the effect of centrifugal forces experienced on curves at higher speeds. If your speed limit is low (and 30 MPH could be considered low), then super-elevation is not necessary.
jlehnertAny rule of thumb when to/when not to superelevate? I'm modeling modern times, which means longer trains with longer cars. After meditating on your comment, I'm thinking that I probably should NOT superelevate.
Based on the results from experienced modelers, superelevation seems to have a neutral or negative effect on model performance, certainly in HO scale and smaller and in tighter curves. It's purely cosmetic.
A small amount of cosmetic superelevation (with room allowed for a gentle transition from level to to banked) can be fine. But if curves are tight, grades are steep, and the equipment is long, derailments across the center of the curve ("stringlining") may occur more often.
Layout Design GalleryLayout Design Special Interest Group
As often happens around here, we will be talking amongst ourselves, spinning our wheels, until the OP comes back in and clarifies some details on what he is after.
Rio Grande. The Action Road - Focus 1977-1983
cuyama Lone Wolf and Santa Fe 22" radius is pretty tight so make sure that you make it banked. Super-elevating (banking) the outside rail actually makes the tendency to stringline worse in sharp curves on a model railroad. Model railroad physics isn't the same as the forces that act on the real thing.
Lone Wolf and Santa Fe 22" radius is pretty tight so make sure that you make it banked.
Super-elevating (banking) the outside rail actually makes the tendency to stringline worse in sharp curves on a model railroad. Model railroad physics isn't the same as the forces that act on the real thing.
Any rule of thumb when to/when not to superelevate? I'm modeling modern times, which means longer trains with longer cars. After meditating on your comment, I'm thinking that I probably should NOT superelevate.
Lone Wolf and Santa Fe22" radius is pretty tight so make sure that you make it banked.
22" radius is pretty tight so make sure that you make it banked. You should be ok with most equipment but shorter cars and shorter trains will run better. Some new passenger cars require 24" radius, some steam locos maybe more.
My answer?
If in doubt, build a test fixture. It doesn't have to be fancy. a few lengths of flex quick-nailed to a hunk of plywood propped on stacked telephone books will do just fine. That way you KNOW exactly what YOUR rolling stock will (and will not) put up with.
In my own work I always include spiral easements into curves and hyperbolic easements between stretches of constant gradient. Makes the transitions much easier on the couplers, and looks good, too...
Chuck (Modeling Central Japan in September, 1964 - grades up to 4%, compensated curves)
Empirical works. I can keep the memories of sine and cotangent in the memory locker.
Henry
COB Potomac & Northern
Shenandoah Valley
CG is correct, that's an empirical estimate by John Allen. There is some ongoing testing of actual models, I hope that we can report on the results in the Layout Design Journal in 2017. Early results suggest that 32/R is roughly correct for radii from about 28" and up in HO. But smaller radii might turn out to be a little higher effective grade than the 32/R rule-of-thumb.
BigDaddy I took too many math courses, so I have to ask, where does the 32 come from?
I took too many math courses, so I have to ask, where does the 32 come from?
I presume you mean 32/R.
Empirical testing conducted by John Allen and other modellers.
It is also said to match prototype railway engineering data when translated to model railroad values. Note: I have no reference to the latter. It is just something I have come across in reading threads on the subject.
CG
If the grade levels out in the curve be careful of the transition. Other than that have at it. I have 3.75 grade, running 6 axles on a 22" radious curve. No problems. Except stalls. But that a different story.
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
cuyamaThe general rule-of-thumb for added effective grade in HO is 32/R
RR_MelI have remotored my locomotives and added 8 to 10 ounces to most of them. I don’t think you would have any problems at 22” and 3%.
But if the Original Poster has not modified locos in the same way, that curved grade may be more troublesome. Of course, the issue will be less pronounced with short trains of short cars.
The general rule-of-thumb for added effective grade in HO is 32/R. For a 22" radius curve, the additional grade is 1.45%. That would make the OP's total effective grade 4.45%. That's an effective grade where some combinations of engines and rolling stock may be problematic.
This would be fairly easy for the OP to mock up and try with his or her own equipment
In figuring your grade, be sure also to allow for transitions from level-to-grade and back. I usually start with one longest car length for each per cent grade.
Good luck with your layout.
From a math standpoint the 22" curve will add about 1% to the effective grade, so the grade will be about 4%. As has been stated, it is doeable but type of equipment, train length and, pulling power of the locos become more of a factor.