Calling all Heli-Cats

[PAL_Houston]

I've been giving more detailed consideration to how I would go about installing a helix to a lower level staging area on my C&I Sub.  Previous iterations that were shown in the "Burlington C&I Sub" Layout Engineering thread were conceptual at best, and had some limitations, like encroaching too far on aisle space and like ignoring the actual positions of existing layout supports, etc. 

That is where you come in: I would like comments from those of you have have built, installed, and/or operated helices on the following helix design.  The helix appears in the southeast corner of this diagram of the C&I  Sub.  This design is based on Ashlin N-scale helix parts 2015 and 2008, which combined should give a 21-inch drop using 8.5 turns from the main layout level.




down to a staging level



The helix would lead  clockwise downward to the lower level, in order to put the staging level approach ramp closer to the aisle, and within relatively easy reach.  Inner and outer track radii are 15 and 16.25 inches, which are significantly smaller than my original notional design.   But using the Ashlin products has the advantage of being commercially available and reliable (n'est-ce pas?).  Some questions I have are:

1.  Can I really combine the 2 Ashlin kits and subtract a half-turn?

The main layout is Atlas C-55 on cork on insulating foam on plywood.

2.  Code 80 or Code 55 on the helix?  If Code 80, where to make the transition from C-55 on the main layout to the C-80 on the layout?

3.  What kind of roadbed on the helix?  Cork or WS foam or ?? 

4.  How about the vertical transitions from the main level onto the helix, and from the helix onto the staging level ---  How do you achieve a smooth vertical transition onto the helix?  (I was only kidding about Fibonacci numbers in that other thread, honest!  )

5.  how does one align and maintain alignment between the helix and the 2 levels, both laterally and vertically?  I guess I was thinking of the helix as a solid module that could be mounted solidly, but with adjustable screws, somehow?

5.  Any tips on wiring the staging and helix?  The layout is Digitrax DCC with a PM42 power management card.  Currently the main level has Red/Black and Green/Black for the east- and west-bound mains, white-black for spurs and yard tracks, and blue/blue-black for the reversing sections.  I was thinking the best approach would be to wire Flag Center wye track as a reversing section, and maintain the same assignments to the mains and yards on the helix and staging levels. 

6.  There is a lot of trackage in staging, but pretty closely spaced.  Fat fingers make for derailed cars.  Also, what about re-railers in key locations?

7.  What didn't I ask you that I should have?

Thanks in advance!

[mmagliaro]

I read your layout design thread.  It looks like you are running mostly 4-axle short
wheelbase diesels?  What about train length?  25 cars?  100 cars?

First, I have some observations about the helix.   

I am assuming this helix is hidden, by the way.


Grade:
8.5 turns at 16.25 inch radius is 867".  A 21" drop in 867" = a 2.5% grade.    Something doesn't add up here.
    The Ashlin kits say they are 2%.
    If it is 2.5%, I think that is pushing it.
    I would be shooting for 2%.  1.5% is better
 
The radius:
Again, how long are you trains?    Pulling a long train up that long hill is going to really put heavy tension on it.   
If you can expand the radius to 18 or 19" that helps a lot.

Time inside the helix:
867" = 2.18 scale miles of track!    At 50 mph,  that will take a train 2.6 minutes to traverse the helix.  Is that okay with you to have the train hidden in there for that long?

--------
I can't answer all your questions, but here are some experiences I've had relative to some of them.

I would not use WS foam roadbed.  I have used it before.  Appearance is nice and it was easy enough to work with, but
it is "squishy".  Helix trackage needs to be firm, rock-solid, and bullet proof.  I'd go with the cork, or no roadbed at all if you
don't mind the noise.  The track needs to be as dead-flat as is can possibly be.

I have used code 80 in a helix before, thinking I wanted sturdier, more reliable track.   The Atlas code 80
always gave me gauge fits.  Be sure to put the sliding rail toward the outside, so that you never have any tight spots
in the gauge (important).  I didn't always do that, and over time, the inner rail pushed toward the outside, narrowing the gauge
enough to cause derailments.    Again, I was probably more susceptible to this because I run long steam.   

I would use SweepSticks or some other serious radius gauge to make sure those curves
are absolutely uniform, and I would glue and spike them down.   This is a big helix.  It has to be perfect and it has to stay put.

 If I were doing it again, I would look at ME code 70, or even consider Unitrack, believe it or not, joints and all, because you will
have perfectly uniform radii all the way through and rock-solid track with it.   

[daniel_leavitt2000]

Heli-cat to the rescue!

...Oh that heli-cat

[bill pearce]

I thought I was being smart using Atlas code 80 in my helix transitioning to ME code55 visible, but what a mistake! I had nothig but problems at the joins, and I don't care how good you are at laying track, the price difference isn't worth it. Since there is no actual advvantage in reliablilty with code 80, why bother. And anyway, I had to look through stacks of code 80 to get some that was in gauge.

Bill Pearce

[mmagliaro]

I thought I was being smart using Atlas code 80 in my helix transitioning to ME code55 visible, but what a mistake! I had nothig but problems at the joins, and I don't care how good you are at laying track, the price difference isn't worth it. Since there is no actual advvantage in reliablilty with code 80, why bother. And anyway, I had to look through stacks of code 80 to get some that was in gauge.

Bill Pearce

That was my sad experience as well (with the gauge).   
Regarding your plight of finding some that was in gauge, I will dredge up something a friend of mine
discovered back in the 90s, which I have seen for myself (and posted before over on Atlas). On the back of those code 80 sections, there was a letter code "A", "B" or "C".  (I don't know if there still is.  I haven't used the stuff in years).   We found that the "A" pieces were all too narrow.  "C" were marginal, and "B" were the best.  We wondered if they were coded by which of 3 dies they came out of, but who knows.

[PAL_Houston]

I read your layout design thread.  It looks like you are running mostly 4-axle short
wheelbase diesels?  What about train length?  25 cars?  100 cars?

First, I have some observations about the helix.   

I am assuming this helix is hidden, by the way.


Grade:
8.5 turns at 16.25 inch radius is 867".  A 21" drop in 867" = a 2.5% grade.    Something doesn't add up here.
    The Ashlin kits say they are 2%.
    If it is 2.5%, I think that is pushing it.
    I would be shooting for 2%.  1.5% is better
 
The radius:
Again, how long are you trains?    Pulling a long train up that long hill is going to really put heavy tension on it.   
If you can expand the radius to 18 or 19" that helps a lot.

Time inside the helix:
867" = 2.18 scale miles of track!    At 50 mph,  that will take a train 2.6 minutes to traverse the helix.  Is that okay with you to have the train hidden in there for that long?

--------
I can't answer all your questions, but here are some experiences I've had relative to some of them.

I would not use WS foam roadbed.  I have used it before.  Appearance is nice and it was easy enough to work with, but
it is "squishy".  Helix trackage needs to be firm, rock-solid, and bullet proof.  I'd go with the cork, or no roadbed at all if you
don't mind the noise.  The track needs to be as dead-flat as is can possibly be.

I have used code 80 in a helix before, thinking I wanted sturdier, more reliable track.   The Atlas code 80
always gave me gauge fits.  Be sure to put the sliding rail toward the outside, so that you never have any tight spots
in the gauge (important).  I didn't always do that, and over time, the inner rail pushed toward the outside, narrowing the gauge
enough to cause derailments.    Again, I was probably more susceptible to this because I run long steam.   

I would use SweepSticks or some other serious radius gauge to make sure those curves
are absolutely uniform, and I would glue and spike them down.   This is a big helix.  It has to be perfect and it has to stay put.

 If I were doing it again, I would look at ME code 70, or even consider Unitrack, believe it or not, joints and all, because you will
have perfectly uniform radii all the way through and rock-solid track with it.   

Max:  thanks for your comments.  To respond to some of your questions:

Yes, mostly 4-axle diesels, but also some SD-7s and SD-24s.  Through-freights, such as I would hope to originate in staging representing Chicago (Eola) or Minn/St.Paul could be quite long, but I'd settle for the 25-40 range with multiple units.  Also, E-units, probably MU'ed pulled 8-10 80 to 85 scale-feet passenger cars  (Zephyrs, Empire Builders, North Coast Limited).

I did the same math you did on the Ashlin products and came up with 2.5% grade also.  I have not contacted them yet, pending input from you guys on this thread.  I gather that foam roadbed and C-80 are not as good as cork and C-55 or possibly the Kato unitrack, although that'd be expensive.  I probably could go larger on the helix radius and make it fit, but I have never built one and would be a bit concerned about making acceptable tolerances that would give a smooth run-of-dip.  This is why I was considering Ashlin, but I get your point about fewer, wider-radius turns.  The Ashlin HO helices are too big (the smaller one is 20- and 22-inch radii with a 47.5 inch max dimension.

Daniel Leavitt has provided some unique ideas about substituting a vertical translation mechanism in place of the helix.  However, my wife would probably not approve of his solution, since it would involve flying fur -- (probably mine.  )

Nobody has told me anything yet about the vertical transitions and how to get them smooth?   I kind of envision some sort of metal plates that allow the helix and the approach ramp to be firmly screwed together to assure the correct angle.  I am also still interested in hearing ideas for adjusting/assuring alignment of the helix with the 2 levels.

[mmagliaro]

Well, here's what I did for my vertical transitions.  It's not rocket science.

If you have a 2.5% grade, the transition areas have to be shallower than that.  You obviously can't come in with
a level track and jump to a 2.5% incline immediately, or you'll have a vertical "kink" right there.
The first 8" of mine were only 0.5% grade.  The next 8" were 1%, then 1.5% and finally 2%.
Yes, that means it took about 32" to get to the full grade.
Also, realize this wasn't in nasty discrete "steps" or 0.5%, 1.0%, 1.5%, 2.0%.   Those are guidelines.
I was just gradually increasing the steepness over that initial stretch.
 
The bottom of my helix was actually cookie-cuttered out of the plywood base, so I just gently jacked it up
on shims off the base level, and the vertical surface was therefore very smooth.    The top of my helix
was affixed to the outgoing track with a plywood splice block glued and screwed under the 1/4" plywood
helix end and under the piece of 1/4" plywood track base that met up with it on the way out of the helix.

You'll also notice that the first turn at the bottom of the helix is a much broader radius than the rest of the turns
above it.  They were all 18".  That first half-turn was 20 or 22.  I can't remember.  That gave me the extra length
to make that gradual transition in grade from 0 up to 2%, and it also eased that transition more by placing it on
a more gradual curve. 

Note the large square access hole inside the helix, allowing me to sit in there with me head
inside, so I could observe trains running through the helix.  This was for testing during construction,
retrieval of a derailed train during operation, and for repairs and track realignment after construction,
which sadly turned out to be necessary because of the code 80 flex track.   In some places,
I put the sliding rail on the inside, and it forced the gauge too narrow over time.  In some places where the
sliding rail was on the outside, the gauge actually opened up wide enough over time that wheelsets
would just drop in between the rails.  Never again will I put that stuff in a helix.

[PAL_Houston]

Very informative, Max.  Thank you.

In your photo it looks like the threaded-rod you used to support and align the helix are bent....I bet there is a story there.  You want to share it?

[mmagliaro]

Very informative, Max.  Thank you.

In your photo it looks like the threaded-rod you used to support and align the helix are bent....I bet there is a story there.  You want to share it?

Heh heh,
... not too much of a story, except that they are only 10-24 threaded rod, so they bend fairly easily. 

On the tops of the rods
sticking up above the top turn of the helix, where it doesn't matter, those were most likely caused by me just
accidentally leaning against them.  I left them on a the top as convenient anchor points for wire and screen
to support the mountain that went over the whole thing later.

On the parts in between the decks where you see some bent rods,
those bends happened because when I drilled all the holes in the curved plywood sections, I didn't get everything lined
up quite right, so I had to cheat and force the rods over a bit to get them through the deck holes in some places.

But in the end, it didn't matter.  Each stretch of threaded rod from one deck to the next was only about 2" long.
So once those decks had nuts and bolts above and below every anchor point where the rods went through,
it all got incredibly rigid.   

Part of it was that I was trying to keep the right-of-way as narrow as possible so that I could fit it all within
the benchwork hard limits that I had, and still keep an 18" minimum radius.  If I had wider roadbed area, I would
have drilled bigger holes and used larger diameter threaded rod, at least 1/4" and maybe even 5/16.

After I got everything loosely slipped together, I measured with a steel straight edge off the base, going at 12" intervals
around each curve, and hand-calculating exactly what the height should be at that point given a 2% grade and
the length along the curve.  I just set each pair of nuts to get that exact height at each point.

It all worked great, with the exception of the Atlas code 80 track that turned out to be variable on its gauge
enough to cause problems, as we've already discussed.

If I were to do this again,  I would not use 1/4" plywood again.  There were
several places where I had to insert extra supports to keep it flat because even at 12" support intervals, it is just
not rigid enough.  It will dip.   Cabinet-grade plywood, or bite the bullet and support it every 6" if you really want
it to stay dead level.  Thicker stock is always an option, but you can't use 3/8" and still keep a 2% grade and an
18" radius.  Either the radius has to go up or the grade does, in order to fit it all in there with
a base that thick, and still have 1-7/8" clearance for the trains.

I really can't say enough good about the idea of using threaded rod and nuts.  That made it very easy to get
the whole thing on a perfectly uniform grade, and make fine adjustments as I put it all together.

Oh... and I'd ditch the cork roadbed too, and put the track right on the plywood.  It might be a little noiser, but
so what?  It would just make it easier to keep everything completely flat, which is crucial.
I would also use spikes in addition to glue.   A helix is no place to fool around and it needs to be made
as impervious to future maintenance as possible.