Flex Track Exactness

WEll first S-curves can be very prone to derailments.    I think you should be carefull using them.

As for laying them the rule of them I read some years ago was to put a straight section about 1 car length between the two curves.    That can all be part of the same piece of Flex track

@prrjim posted:

WEll first S-curves can be very prone to derailments.    I think you should be carefull using them.

As for laying them the rule of them I read some years ago was to put a straight section about 1 car length between the two curves.    That can all be part of the same piece of Flex track

Do you think that shimmy-ing 2" over 27" or so is too big of an s-curve? I took my mismatched/misaligned ends and moved them back from each other to fit a bigger section to try to spread it out.

I appreciate the tip. I definitely was thinking that two flowing curves meeting each other would be better. I wouldn't have thought to put a straight between them.

the straight section , should be as long as your longest piece of equipment, be it a car or engine

Noted. That's gonna be a challenge. I'll go back to the drawing board.

@Dave Koehler posted:

the straight section , should be as long as your longest piece of equipment, be it a car or engine

This is good advise if you run scale cars with the couplers body mounted.

However, 3 rail trucks with the couplers truck mounted do not need as much straight track between the curves.  Maybe even none depending on the type of cars you have.

Since you run 3 rail I would recommend as long a straight track as you can fit in to help operation and it will definitely look better.

I don't know what you mean by shimmy-ing 2 inches in 27 inches?    So I can't comment.   Perhaps a different explanation of what you mean.

I don't have much experience with S curves beyond O 31 and even with talgo mount couplers, keeping them on the track was hard.     I did have a layout with broader curves on Gargraves that when through a crossover and then curved the other way across a 4 ft width.    The crossing was maybe 6-8 inches of straight, and I don't remember that it was too bad for tracking.

@CAPPilot posted:

This is good advise if you run scale cars with the couplers body mounted.

However, 3 rail trucks with the couplers truck mounted do not need as much straight track between the curves.  Maybe even none depending on the type of cars you have.

Since you run 3 rail I would recommend as long a straight track as you can fit in to help operation and it will definitely look better.

I was in 3 rail for long time, and the physics are the same . if a car is going through too tight of S curve  The draw on the front, and the weight io the train behind it, can cause  the car going through the S to derail.  This is in any scale or gauge and any coupler configuration.  The longer or lighter the car the lager the potential for a problem!

As long as you put the 2 gentle curves (probably less than 15 degrees of curvature, one at each end of your 27" stretch) to join your 2" misaligned straight sections, I think it will be highly unlikely to have S-curve issues.  However, despite how easy that would be, it may not be esthetically pleasing.  Isn't there some other way to fix the misalignment in your track plan?

Chuck

@prrjim posted:

I don't know what you mean by shimmy-ing 2 inches in 27 inches?    So I can't comment.   Perhaps a different explanation of what you mean.

Meaning that I'm moving 2" left (or right if you're coming from the other way) over a 27" length.

I thought making the left/right movement small over a great distance would help minimize problems. I'm going to be pulling coal trains through there with live loads so any weight-related derailments will be a major problem. 

@PRR1950 posted:

As long as you put the 2 gentle curves (probably less than 15 degrees of curvature, one at each end of your 27" stretch) to join your 2" misaligned straight sections, I think it will be highly unlikely to have S-curve issues.  However, despite how easy that would be, it may not be esthetically pleasing.  Isn't there some other way to fix the misalignment in your track plan?

I suppose we can argue esthetics all day long, but I had to do something similar for my yard due the way the switches worked out on the entry to the 10-track yard and the angles involved.  I had offsets that I couldn't easily eliminate, so I resorted to the S-curve.  It has caused zero issue derailing anything from the Big Boy or Challenger, and anything smaller.  Personally, I doesn't think it looks all that bad.

I actually used two Ross O72 curves for one section and Gargraves flex for the other.

@Dave Koehler posted:

the straight section , should be as long as your longest piece of equipment, be it a car or engine

That would be optimal... but, given my limited options, I've had success with a straight in the middle of the S that is the length of the longest truck/driver set that you have in inventory.  For me that's a 5.75" - 6" straight in the middle of the S (no. 5 crossover).  You should be able to finagle 2" if you've got 27" to work with.

That's some very nice Finagling John

Remember, this is all opinion, and everyone has one.    But I don't think  you will have a problem with that.   And it seems like you could get almost a hopper length of straight,   But only moving that distance, your original idea of a large radius S seems like it should work.

@BillYo414 posted:

... how to make S bends. It seems like it would be tough to get it correct.

In addition to the preceding helpful information, I would suggest one of the other important things to get right is tangential alignment of the flex with the abutting tracks, so that there isn't an abrupt change in the angle of the mating tracks at the joints.

To accomplish this, here's what I do:

With the fixed curves and/or straights held in place, bend and overlay the flex track on top of the fixed tracks so that the overlapping ends of the flex rails are completely in line with the pieces underneath.  Partially tack the flex in place (supported in the midsection at the same height as it's ends), and with a Dremel cut-off wheel, trim both ends of the flex flush with the ends of the fixed rails below it.  Slide the support shims out from the sides and lower the flex into place and finish securing it to the bench.  These temporary support shims could just be extra pieces of the same type of track.

Bill,

Check out John Armstrong's TRACK PLANNING FOR REALISTIC OPERATION.  He goes into a whole chapter on the problems and solutions for S curves, both horizontal and vertical S curves (elevations. )

I appreciate the suggestions. I'm feeling a bit more confident now. I put my order in for my track to get my two loops done. I was considering restarting the track plan to try to get rid of the s-bend flex track part.

I do some have concerns that this is on a mainline and the speed I could carry on the mainline combined with the weight of a full coal train could be a problem. Based on what everyone said here, I'll just have to spread the bend out further still if that ends up being the case. That'll move some switches but it would be worth it to be able to thunder down the straight away.

@SteveH posted:

In addition to the preceding helpful information, I would suggest one of the other important things to get right is tangential alignment of the flex with the abutting tracks, so that there isn't an abrupt change in the angle of the mating tracks at the joints.

Sharp S curves are what should be avoided. Here's a main-line S curve, albeit 5 feet in length. It sounds like I use a similar approach to Steve's. For the 080 and larger curves I use plywood forms but for the few 072 curves I use a section of Atlas 0 and use the rails for the patterns.

This took three sections of GG to complete this curve, there will be a siding track along side. Three feet of this is located on a hinged section of bench work. It is being held in place with clamps until I can get some locks to complete the drop down.

My mainline has several "S-curves", as Dan states, they're a number of feet in length.  It's the short S-curves that bite you bad as a rule.