The prototype railroads are very concerned about stringlining in mountainous territory as well. The Norfolk Souther ETT for the Piedmont Division's Asheville District lists maximum trailing tonnage behind light weight cars. See page 118 of the ETT at:
www.rtprailfan.com/NS_Piedmont.pdf
Similiar restrictions aren't listed for more "flatland" districts.
Ray
SpaceMouseAll in all, by looking at your "Tendencies," I couldn't be in better shape.
Maybe. But you'd still be well-advised to test it. Light cars stringline more easily than heavy, and that's a tight curve. If you are pulling empty log cars uphill, you may discover some challenges. Hopefully not.
Layout Design GalleryLayout Design Special Interest Group
LOL. My whole train will fit inside 2 of your 80 ft/ cars. I haven't built my log jimmies yet. Their still in the box but will be 4". I'll be scratch building the ore cars, but they will be around 26 scale feet.
All in all, by looking at your "Tendencies," I couldn't be in better shape.
Nice slides by the way.
Chip
Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.
SpaceMouseIf by chance it does appear to be a problem, I guess the solution would be a reverse superelevation.
Nope. That adds friction and potentially makes stringlining worse.
@ Bruntonpretty thorough
@SpaceMountainI'm going to be interested in your testing of a logging loco in tight turns, and big grades. I may (hope) want to do a little of this on a small logging scene on my new layout.
Brian
My Layout Plan
Interesting new Plan Consideration
Speed isn't really much of a factor in stringlining. It's more a function of rolling resistance, the angle of the longituinal axis between adjacent cars (which is driven by car length and radius of curve), number of cars in the train and, to an extent, the height of the cg of the cars above the rails. Track irregularities, like a local tightening of the curvature or bumps at rail joints can trigger a stringlining "event" if the train is already close to the limit anyway.
Higher speed may actually help resist stringlining, as the inertia of the train tends to push it outwards from the curve. For that to have any significant effect, though, I think your train would have to be moving at a substantial clip.
These Powerpoint slides I put together about stringlining some time ago might help:
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
While I have no problem envisioning stringing as a problem, I'm finding it difficult so see it as a problem for geared steam pulling at 10 scale miles per hour around a 16.9 inch curve, when on my previous layout I was pulling up a 4.3 % grade with 18 inch curves at normal frieght speeds.
If by chance it does appear to be a problem, I guess the solution would be a reverse superelevation.
cuyamaThe tendency for cars (especially light cars) to be pulled to the center of tight and/or steeply graded curves, derailing them.
Got it. Thanks.
SpaceMouse stringing
Stringlining. The tendency for cars (especially light cars) to be pulled to the center of tight and/or steeply graded curves, derailing them.
SpaceMouseI did a few searches on this topic but was unable to come up with a clear definition or impression of what exactly stringing is or what conditions would create it.
Take a piece of string, lay it on a table in a curved position. Take each end of the string, and pull it tight, the string straightens out.
Imagine this on a train, taking a tight curve, with heavy cars on the end.
http://www.railpictures.net/photo/564522
Mike.
My You Tube
BruntonBut watch out for stringlining on such a small radius.
I did a few searches on this topic but was unable to come up with a clear definition or impression of what exactly stringing is or what conditions would create it.
I will say that the cars will be very short. They will either be log jimmies or ore cars 2 1/2 to 3". If anything, the empties might be too light.
Here's what I can tell you. It's a 2 1/2 turn from lower level to upper level which is a 12" separation, top of plywood to top of plywood. Inside radius is 29.75 "outside radius is 32". This was custom built for me, uses wood supports. Total footprint is 67"x67"
SpaceMouseShort hijack here. I want to test my geared steam to see if they can make a 4% grade up my mountain. It's mostly straight, but I do have a few turns. The smallest radius is 16.9 inches. Would I be wanting to test at CG=4 +28/16.9 5.66%?
Would I be wanting to test at
CG=4 +28/16.9
5.66%?
But watch out for stringlining on such a small radius.
32/R is actually the long-accepted rule-of-thumb for HO. Preliminary testing suggests it may be a little low for tight radii.
32/16.9 = 1.89
1.89 + 4 = 5.89% effective grade
And may be a little worse in practice.
Easy enough to mock up the graded curve and try it with the desired equipment.
railandsail18 3.5 5.05 565" (47', 3/4 mile HO) *LDSIG-Modified John Allen Formula – CG = G+28/Radius
*LDSIG-Modified John Allen Formula – CG = G+28/Radius
Short hijack here. I want to test my geared steam to see if they can make a 4% grade up my mountain. It's mostly straight, but I do have a few turns. The smallest radius is 16.9 inches.
Neal,
What are the basic dimensions and geometry of that helix? Inner and outer diameter and rise per turn?
Rio Grande. The Action Road - Focus 1977-1983
I can run two trains in the helix at the same time including both auto racks and full length modern passenger cars. I had my helix custom made in a 'kit' as I know my limitations. Just so happens I'm building this exact same helix in our snowbird house. This one is a little bit higher 16" instead of the one home 12" Pictures available if you want to see them..
Neal
cuyama railandsail Neil is saying he has an outer radius of 32 inches,....that would work out pretty close to 2% grade if he was not including compensation? It's all about clearance and what compromises one is willing to make. If you have a GG1 with pantograph and want it to use the helix, for example, you need more clearance than others might. 2% nominal grade at 29.75” radius is 3.75” railhead-to-railhead. Once allowing for subroadbed, subroadbed supports (if any cross the track), track height, and finger access, that’s tighter than I would recommend or build in HO, but others might be willing to go that tight.
railandsail Neil is saying he has an outer radius of 32 inches,....that would work out pretty close to 2% grade if he was not including compensation?
It's all about clearance and what compromises one is willing to make. If you have a GG1 with pantograph and want it to use the helix, for example, you need more clearance than others might. 2% nominal grade at 29.75” radius is 3.75” railhead-to-railhead. Once allowing for subroadbed, subroadbed supports (if any cross the track), track height, and finger access, that’s tighter than I would recommend or build in HO, but others might be willing to go that tight.
I have 3.75" railhead to railhead. Yes, it is tight when you are trying to re-rail cars. I have only had to do that a few times in my 10 years of running trains in the helix. If the rolling stock is in good shape and you make sure the track is as bullet proof as you can muster, there should be very few derailments in the helix as there are no turnouts or other trackwork that might cause problems.
My helix is also accessible from the inside, so I really haven't had a big problem with getting to the cars if I need to to remove or or rerail them. I would have liked to have built more clearance between levels, but I chose other priorities in this instance and compromised. It worked out well for me.
Guy
see stuff at: the Willoughby Line Site
railandsailNeil is saying he has an outer radius of 32 inches,....that would work out pretty close to 2% grade if he was not including compensation?
Neil is saying he has an outer radius of 32 inches,....that would work out pretty close to 2% grade if he was not including compensation?
Brunton,...back eariler in this threadRadius Grade Compensated Grade* Run Length 18 3.5 5.05 565" (47', 3/4 mile HO) 24 2.7 3.87 754" (63', 1 mile HO) 30 2.1 3.03 942" (79', 1.3 miles HO) 36 1.8 2.58 1131" (94', 1.6 miles HO) *LDSIG-Modified John Allen Formula – CG = G+28/Radius
18 3.5 5.05 565" (47', 3/4 mile HO)
24 2.7 3.87 754" (63', 1 mile HO)
30 2.1 3.03 942" (79', 1.3 miles HO)
36 1.8 2.58 1131" (94', 1.6 miles HO)
I'm having a lot of trouble accepting that Neil's helix manages a mere 2% grade with such small radii and still manages to have overhead clearance sufficient to allow his fingers to get in between the spiral layers to fix things. Maybe he's in N scale?
Double Track Helix Radius(s)
Neal M Mine is a two track helix. Inside radius 29.75 outside radius 32.00. It has a 2% grade with a height of 12" This was the biggest I could have due to space restrictions. I'm sure a wider helix with a lesser degree of grade would be better. I've run 2 diesel engines, both 4 and 6 axle engines and anywhere from 20-28 cars with no issue. However, with my 89' auto racks, I usually have 2 6 axle engines with 12 auto racks. I don't see any type of drag or issue running them up the helix.
Lonehawk,
I have a pdf on helix design and ideas. If you or anyone else are interested, PM me and I will send you a copy
mbinsewi Have you hijacked the OP's thread? Mike.
Have you hijacked the OP's thread?
Frak, I don't care. If this leads to good info for someone else as well, so much the better. I've pretty much figured out what I need to do, based on the input I've gotten.
I'm going to go with the 30" round helix, and plan it for 3.5" vertical clearance, which will give me a nominal grade a bit above 2%. (2.2, I believe), and a compensated grade a bit above 3. It's a bit steep but being that I plan to run short trains of 40' or smaller cars with heavier power, I'm pretty confident I can get away with it. I still plan to test with what stock I have presently, and I'll adjust as necessary, but that's a project for another weekend. So, while I wouldn't say the plans are concrete yet, I know which way to go.
The whole helix thing is going to be a while in coming though anyway. I just came up with what I consider my "finalized" plan yesterday, which will actually allow me to build in stages. I'll start with the lower deck, and use a balloon track temporarily where the helix will eventually be, which will keep me in a loop-to-loop configuration. That way, I'll be able to actually be running trains while I work on the helix and level two. I figure with a new baby on the way and funds not exactly pouring from heaven, it'll take me 3-5 years to finish it all.
I'll leave the eventual helix site unsenicked, so I'm not wasting time, materials and, more importantly, money. (Or maybe I should use that as my test site, since any mistakes would be ripped out anyway...?)
The upper deck will come second, and the helix last. Again, that will keep me able to run trains while I build. That was the big thing with my last attempt, not being able to run something while I built. Lost interest.
I'm also going to design the whole thing to be able to break down and move with a minimum of fuss. I figure I'll probably be moving sometime after I finish, and having all that work go to waste would really be intellectually malodorous.
Thanks everyone for your input on this though, it was a big help in figuring it all out! I'll post my plans once I have them transferred from paper to CAD.
- Adam
When all else fails, wing it!
Just made a quick trip down to my storage trailer and discovered a few tall cars I had forgotten I had,....these Genesis articulated Auto-Max cars. I think I have 2 sets of 2 cars each set. Wonderful detail. I just have to have enough clearance to run a few of these. I did quick measurement without removing them from their packaging and it appears they are about 2 7/8 inches high. Their website says 20 ft tall protoypically, which would be 2 3/4 inches high.
I just measured the height of a well car with stacked containers. From the rail head to the top of the containers was 2 3/4". Take it from there.
I have a panograph GG1, and dbl stacks, so you figure I should use a 4+1/4" figure??Here is a dbl stack photo that was sent to me,...
For clearance in a helix. The pic below shows 97 mm clearance from memory. With a Kato HO double stack car and two containers. Phil
Phil
Regretably most all of my rolling stock and locos are still stored away in my cargo trailer (just yearning for the light of day)....ha...ha
railandsail selector ....I added 1/4" for cheap insurance, and that figure became my minimum overhead clearance throughout my track system on my current build. So far, so good. You HAVE TO know that figure. So what is that figure you currently utilize?
selector ....I added 1/4" for cheap insurance, and that figure became my minimum overhead clearance throughout my track system on my current build. So far, so good. You HAVE TO know that figure.
....I added 1/4" for cheap insurance, and that figure became my minimum overhead clearance throughout my track system on my current build. So far, so good. You HAVE TO know that figure.
So what is that figure you currently utilize?
Sorry, a little late to rejoin the discussion here on the Left Coast. I ended up deciding that, in the absence of ever trying to run doublestacks in a futuristic way (I'm in the transition era), my maximum clearance was determined by the extended pantograph, that that came to almost exactly 4", a hair under. So, I opted for an absolute minimum of 4.25" (4 1/4").
I ended up doing the same thing on my last layout, the one with a nearly-six-feet diameter helix. I decided, later, that while I didn't regret my decision, or the fun I had building it, the guys who described them as space hogs and almost always a LOT of hidden running were right. So, no more helices for me.
Last comment...I knew I'd have to reach between the layers a few times during the layout's life to retrieve items or to attempt to rerail them, or if a loco died or dropped electrical contact, to reach in and nudge them along. In that respect 4" was about right, but also not terribly generous. Not for fat fingers, anyway.
railandsailSo let me ask for clarity. For a 30" R helix with 4" between railheads
That seems a little tight to me for modern-era equipment, but I am conservative in this regard. Here's how I would calculate:
Modern-era clearance from NMRA S-7: 3 5/32”Helix roadbed (2X 1/8” Masonite): 8/32”Track + adhesive: 6/32”Metal bar or strap below roadbed: ?Subtotal: 3 19/32"Amount left for construction variance, finger access, etc.: 13/32” at best
The wild card here is an additional loss of clearance if your helix roadbed support is a strap or bar below the subroadbed.
Given this, I’d suggest at least 4¼” railhead-to-railhead elevations. But again, I am conservative, since I design for others to build and, for most modelers, some construction variance is inevitable.
Byron