Helix question

[railandsail]

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

 

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

[mbinsewi]

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.

Have you hijacked the OP's thread? 

Mike.

[railandsail]

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.

[Lonehawk]

mbinsewi

Have you hijacked the OP's thread? 

Mike.

 

 

  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.

[trainnut1250]

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

 

Guy

[railandsail]

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.

I'm assuming those radius quotes are dimensions to the center of the tracks?

So on your double track helix you have 2 1/4" between the tracks.
1) Can you run your long auto racks up the outer track while running another train passing it on the inner track?
2) What sort of minimum clearance do you find necessary for those auto racks to clear any fixed obstacles (structures) outboard  of the outboard radius.

I am planning a double track helix in as big of a diameter helix as possible, but I am limited to probably a 31" outer radius. I also want to run those long auto racks and long passenger cars (and sometimes possible a passing situation on the helix). So my concerns are, the clearances needed for the ends of those cars around the outer helix structure components,....and the minimum distance I might allow between the inner and outer helix tacks to allow for those 'inadvertent' passing situations that might occur when running multiple trains.

[selector]

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?

[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?

Brunton,...back eariler in this thread
Radius   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

[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.

[trainnut1250]

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.

 

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

[nealknows]

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

[riogrande5761]

Neal,

What are the basic dimensions and geometry of that helix?  Inner and outer diameter and rise per turn?

[SpaceMouse]

railandsail

18          3.5                5.05                  565" (47', 3/4 mile HO) 

*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. 

Would I be wanting to test at 

CG=4 +28/16.9

5.66%?

[cuyama]

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.

[Pruitt]

SpaceMouse

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. 

Would I be wanting to test at 

CG=4 +28/16.9

5.66%?

That should give you a good idea. It would most likely represent the worst case. Operation on the helix, if constructed, should be equal or maybe a bit better.

But watch out for stringlining on such a small radius.

[nealknows]

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"

[SpaceMouse]

Brunton

But 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. 

[mbinsewi]

SpaceMouse

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.

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.

[cuyama]

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.

 

[SpaceMouse]

cuyama

The 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]

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. 

[Pruitt]

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:

[railandsail]

@ Brunton
pretty thorough

@SpaceMountain
I'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.

[cuyama]

SpaceMouse

If 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.

[SpaceMouse]

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. 

[cuyama]

SpaceMouse

All 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.

[Colorado Ray]

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