Depends....Total track length of the grade? How many locos? How much/how heavy rolling stock those locos pulling? How long are the rolling stock? Longer rolling stock or 6 axle diesels might have more of an issue with the 22" radius and not much of an issue with the 3% grade.
Terry
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How long are the trains you plan to run? Long trains on curves, any curves even on flats, may sometimes "stringline" and fall to the inside of the curve. This is a much worse problem when you throw in a grade.
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To me, 22" radius is a very sharp curve. As others said, it depends. If you are running short trains with short rolling stock, you can probably get away with it and be ok. Long rolling stock and longer trains might not like your plans too much, so it depends.
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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.
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.
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cuyamaThe general rule-of-thumb for added effective grade in HO is 32/R
I took too many math courses, so I have to ask, where does the 32 come from?
Henry
COB Potomac & Northern
Shenandoah Valley
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.
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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
BigDaddy 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
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.
Empirical works. I can keep the memories of sine and cotangent in the memory locker.
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)
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.
Lone Wolf and Santa Fe22" 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.
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.
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.
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.
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.
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
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
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.
Robert
LINK to SNSR Blog
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
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.
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 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.
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.
http://www.engr.uky.edu/~jrose/RailwayIntro/Modules/Module%206%20Railway%20Alignment%20Design%20and%20Geometry%20REES%202010.pdf
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.
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"
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
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.
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.