Why the Buss Line?

George, if the entire length of track in the helix is soldered rail why the need for the buss through the helix? The resistance of the nickel, silver, and zinc rail alloy for the total run of your helix is an almost unmeasurable small number.

Why the track buss?

The resistance of nickle silver rail is not insignificant, according to all that I read on DCC forums.  The rule of thumb is to have a feeder for every three foot section of track - for every piece of track for that matter. The major reason for the rule is to avoid depending on rail joiners to pass current.  But I think there can be significant loss along the rails when you are drawing an amp or more.

I strip 12 gauge Romex for the normnal track bus (white and black wires) and I had lots of bare copper ground wire left over. It took a little extra time to staple down the wire and put a feeder on every three foot section but that was a very little time compared to the overall helix construction time. 

The total length of the helix is 75 feet. I feel pretty good about the power in the helix. It's definitly overkill since there will be at most two engines on the helix at any one time (double headed trains). But should a solder joint fail, I am well covered electrically.   

Better safe than sorry?   

Helix

That is one nice looking helix, George. The way you finished it for scenerey andblending in with the upper level is very nice. Most people hide the helix in mountains, etc. Well done.

Roy

Why the Buss Line?

I did a quick Google search and found an excerpt from a DCC book by Mike Polsgrove. He measured code 83 nickel silver rail resistance at 0.057 ohms per foot. This is compared to 0.0025 ohms per foot for 14 gauge solid copper wire (I’m using 12 gauge). The resistance of my 75 foot helix track would be about 4.25 ohms, 8.5 ohms across both rails. If a pair of engines were drawing 1 amp of current, this would give a voltage drop of 8.5 volts at the end of the helix. This is quite significant and would definitely corrupt, if not kill, the DCC signal.

Three dimensional art

A model railroad helix has appeal because of its construction and its shape.  It shoud be in a sculpture collection.  If we were boy-scouts there would be a merit badge for helix building as it has to be one of the most difficult design and construction projects in the hobby.  Thanks for sharing.

Art Armstrong

I've built similar helices

Your method is very similar to one used on the Sudbury Division (we've tried several.)  Ours use half inch plywood as well, preferably poplar plywood.  Our vertical spacing is 3.5" per turn, no roadbed.  This allows us to get Walthers enclosed trilevels up with millimeters of clearance to spare--double stacks weren't invented yet in the 70's.  We used shorter laps, only about 1/2", since there's no benefit to making them longer.  The weakest point in the ramp on this sort of helix is at the beginning and end of each lap joint, where the wood is only half thickness; the plywood bends easily here, since it's only 1/4" thick.  We try to put spacer blocks above and below the joints to stablize them.  

One question, though:  why would you want to have superelevation on a helix?  That's the last thing I would want to do, since superelevation is purely cosmetic on a model railroad, and in fact makes it easier to stringline long trains on a curve.  We have one helix on our Soo branch which is 28 1/2" radius, and we manage to get 40 car trains up it.  If it was superelevated, I guarantee trains that size would tip over on it.  I've thought about putting a reverse superelevation (contra-elevation?) on a helix since that would actually help keep the cars on the track, but wasn't certain what that would do to coupler dynamics, so I haven't tried it so far.

Much ado about very little

I guess no one likes my helix wiring. 

I left out one aspect of the helix wiring because I didn't think it was of great interest. The power to the helix is split between two circuits.  The lower half of the helix is fed from the lower level track buss and the upper level is fed from the separate upper level track buss so the buss lengths involved are about 1/2 of what it appears.  

And the feed for the upper half is run vertically through the laps.

Back to the issue of voltage drop.  12 gauge solid copper has a resistance of 0.00187 ohms per foot. A 75 foot run would have 0.l4 ohms. With a 1 amp draw, the voltage drop is 0.14 volts. Or if you consider both conductors, 0.28 volts. I really don't see a problem with this. 

I Have No Issues With Your Wiring

George, my comment was not that I didn't like how you wired your helix. My question was about the conductivity of nickel silver track. When I first saw your copper wiring following the helix spiral it made me think "Why did he do that when silver is a better electrical conductor than copper and nickel isn't far behind?" Then I followed the link to the video of the fellow showing voltage drop on his layout due to lack of feeders in his helix. This further confused me since by all normal standards nickel silver rail should be an excellent conductor given its composition and large cross section. I am anxious to do a bit of measuring myself but assuming all of this information is true then I can only come to the conclusion that nickel silver railroad rail must be chock full of impurities in its manufacture.

Table taken from CRC Handbook of Chemistry & Physics:

  Silver

  Copper

  Gold

  Aluminum

  Iridium

  Brass

  Nickel

  Iron

  Platinum

  Steel

Helix Types

 If it works for you, then your helix wiring is fine!

I have 3 helixes on my HO/HOn3 layout.  One is a "standard" one of about 5 turns in HOn3 only.  The other two actually are "stacks" of helixes.  One stack consists of a 1/2 turn dual gauge helix approached by a long grade. The second multiple turn helix in this stack is HOn3 only, with separate entry and exit points not related to the dual gauge one below.  It also is of smaller radius than the one below.  The third stack consists of a dual gauge helix twisting downward to a staging yard underneath the main yard, where the main entry is.  This main entry also leads to a single twist dual gauge helix on top of the lower one with the exit leading off to a long down grade.  This main entry also leads to a  third HOn3 only helix of several twists on top of the other two which leads to an HOn3 "high line".  All of these helixes are of the same radii.

All the helixes are built of 1/8" tempered Masonite laminated together with carpenter's glue and precut to various diameters.  This thinness is needed to minimize the grades.  All are supported by threaded rod material using washers and nuts, which allows fine tuning of the grades as needed.  To hold the track in place (all track in the helixes is ME flex track), I first tried glue which didn't work because of the plastic ties.  I ended up using AMI "Instant Roadbed" which both held the track firmly in place and deadened the sound.  The Instant Roadbed is  very flexible  and the plastic-tied flex track can be pressed into it, usually easily, depending upon e temperature of the room.  I have used a low wattage hair blower to soften the Instant Roadbed without softening the ties.

I assembled the roadbed, complete with the track and Instant Roadbed, before putting them in place on the layout.  That way, I could drill through the layers of Masonite and thus save time and make sure the holes were all aligned properly for the vertical threaded rods.  This helix setup has worked fine for the past ten years or so.

I use Digitraxx DCC and I ran the wiring busses but inside the edges of the helixes, following the turns, so the busses then could enter and exit the helixes at the proper places.  I elected to use horizontal power districts on the whole layout, rather than vertical ones, in order to make trouble shooting a lot easier because of the layout's various levels (there are 3) and geography.

AMI went out of the roadbed business in 2007, unfortunately.  The material is uncured butyl rubber and I understand that similar material can be gotten at auto supply stores that specialize in air conditioning parts (it's used to wrap a/c piping).  I haven't tried since I still have some AMI material left.  Somebody also found similar material at:

   http://www.trains.com/trccs/forums/1056223/ShowPost.aspx

Someone else has suggested trying plumbing supply stores; the material, or similar stuff, used to wrap pipes.

Hart Corbett

Novato, CA

Nickel silver has no silver in it!

According to various Internet sites, "nickel silver" is an alloy of copper, zinc, and nickel, often in the proportions 5:2:2. It does not contain silver.  You were lead astray by clever marketing
 

I Should Have Known

I work in Marketing! We have a phrase around the office "Marketing, not to be confused with reality". I should have known better. Feeders, feeders, everywhere feeders!

German Silver

What we call nickel silver is one of various alloys called "german silver". 

Typically, they are 60% Copper, 20% +/- 5% Nickel, and 20% +/-5% Zinc.  (Sorry, no silver).

My CRC tables indicate a 60/15/25 % composition, with a resistance for 10 gauge wire of .0191 ohms/foot.  That is not good for us.   You start binding up those electrons on an alloy, and you lose conductivity quickly.

So, don't rely on nickel silver for distance conduction of electricity.  That rule of thumb we've seen repeated so often on the model rail forums is prudent:  "every piece of rail is connected to a feeder or soldered to something that is connected to a feeder".

Hope this helps.

George, great helix article, there. Thanks!  I just may build one for the challenge and experience, that, and for my real hobby, which is making sawdust in my driveway on weekends.

George I think its neat.I

George I think its neat.I like the idea of trackaround the outside it gets rid of the bald blob look.I'm havin a look at mine to see if i can do it now that I'm redoing one of my helixes

Cheers

Did mine a little differently, but not much

 Well known Australian Modeller Roger Lloyd, without whose help, I would still be installing my Helix, searches for another piece of track which advances as the glue dries.

My three track Helix is about 1.0m radius allows trains to rise about 10.5 cm per level about 55 cm in all at 1.5% grade. Over all I can run normal length trains up the helix without adding extra engines.

The area I model uses two different gauges, and both lines are bidirectional. The Helix will act as a storage area where trains will stack to add time to time tables, and on the SG helix a long passing loop makes up the third track.

I use the same joining technique but I place droppers on every meter of track and run them straight down to a heavy duty power ring main below the bench tops. I suspect now , after seeing the wiring in this article, I may have done it differently. Although I believe my system is probably going to show less voltage drop.

The uprights were cut out of 14mm 3 ply and the slots (1/3 through) are machined so that every upright is identical.
Where possible they were placed equal distance apart, their position accurately marked. The first level was then calculated and a section of the bottom of the risers was cut off and the baseboard was glued together for that level. It was then placed in its slot, glued and screwed, ensuring the 10.5 cm space was maintained.  The track was then marked out and glued in place using a quick acting caulking glue.
Then the next level was laid.
Because the first level was accurately cut and placed, each new level is now automatically in position.
This was a real time saver. The six pairs of uprights failed to hold the helix, and some sag developed between them. This was eliminated by glueing another single upright on the inside between the double risers.
A pair of weighted bogie vehicles let go on the top, now roll at a medium speed all the way to the bottom without picking up speed. I am very pleased with this system which I designed myself after looking at the many systems from Lyn Wescotts to many others I saw when I searched the internet.
Eack track is 37 m long. It takes a fair while to climb, but it does the job magnificently.In recognition of the amount of work put in, Roger brings the first train to the top! Two engines haul 40 vehicles without slipping. I am pleased with that!
Cheers
Rod Young
If you have time to spare see the Railroad grow here
http://tinyurl.com/yfmhstp

Sorry, there's no silver

Sorry, there's no silver in nickel silver. It's an alloy of copper, nickel, and zinc, sometimes also containing lead and tin:

To us old-timers in the hobby, it's generally known the stuff has an electrical resistance that's about 20 times that of copper wire. Brass rail is a far better conductor than nickel silver rail.

However, brass oxidizes readily and the oxidation is an insulator. The oxidation on nickel silver is semi-conductive, and of course the color of nickel silver rail is much more correct than brass.

Long runs of nickel silver track have a significant voltage drop, so you want to use a copper bus wire and rail feeders at least every 10 feet to eliminate the voltage drop of nickel silver rail. I personally prefer feeders every 3 feet (every flex track section) to eliminate all voltage drop - the DCC signal does not do well when the voltage drop becomes significant.

Very nice helix

Rod and Roger,  great job on that helix.  What kind of tool did you use to cut the slots on the uprights? Having the right tool is 90% of the job.  

Helix

George thats a very nice helix!

There is no silver in nickel silver

As Joe mentions it is an alloy, usually formulated as 60% copper, 20% nickel and 20% zinc. And I'd be shocked if it were especially pure as delivered to model railroad manufacturers. And rail joiners provide a far smaller electrical cross section every 3 feet.  So this is a classical case where we put away the charts and rely on empirical measurement, as in the DCC book referenced above.

As for George's helix wiring, it's fine, the important thing was getting feeders to every rail section.  True enough that some wire can be saved with a "vertical strategy", sending vertical buses up every 3 feet or so around the circumference of the helix.  That's what I've done on mine.

Regarding lap joints I took a different approach, using two layers of thin plywood and lapping them alternately so each lap is about 18" long.  Extremely strong throughout, and no routing or milling required.  For support I used 1/8" threaded rods with small-diameter PVC pipe (plus washers) around them.  There's a nut/washer pair securing the rod at bottom, plus a nut/washer below the lowest helix level, and another on top.  You set the grade on the lowest level and the additional levels fall into place automatically thanks to the PVC supports, all precut to same length.  And it's infinitely adjustable/tweakable via the nuts.

Vertical Clearnace VS Grade...

As I look at the photo's of the 3 Track Helix (which is what I plan on doing for the Interim P&A) a question comes to mind of where's the "line" between vertical clearance vs grade.  This decision is CRITICAL since with a 3 track helix, there is the issue of dealing with derailments, and having enough space to fix any mess.  I know the goal is ZERO derailments, but if one doesn't plan or a visit from Uncle Murphy, he will most certainly come over more than once during each op session!  With a 30" inside, radius and that one going from an 18" level to 69" level, having the smallest grade is desirable but if I only have say 3.5" from top of subroadbed to bottom of subroadbed for next course in the helix, if there is a derailment I fear of a massive headache disentangling the mess.    With the 30" radius, 4.25" total rise (I plan on using 3/4" MDF since my experience with 1/2" material has been nothing but trouble when it comes to subrodbed) that would make the "uncompensated for curve" grade 2.25 %! Add in the theoretical effect curves have on a grade from Johhn Allen's Calculations, and we're pushing almost 3%! YIKES! Increasing the radius isn't an option because the blob the helix is located is as wide as it can go.  And for the 3 Tracks, they are spaced 2" O.C., which is find for most equipment, though for the 2-6-6-2's and 2-6-6-6's and 85' passenger cars will probably have issues already!!  UGH!

Any thoughts?.

Ken L.

I too am having trouble 1/2"

I too am having trouble 1/2" ply road bed bowing and I am going to rebuild with 16mm chipboard that is a new product from a mill I cart from and have had discussions with them about usage so it will be interesting.                   Track will be on 2 1/2"centres so i can get fingers in between if Mr Murphy rears his ugly head and for clearance of those 85 footers.I'm using 1 x 4 for between layers although the threaded bar and pvc pipe sounds interesting Hmmmm

The secret to keeping any ply from sagging is support.

Galen, who posts here as Ocaliecreek, built a small timesaver module with a harbor scene on it and brought it to the modular club one night before he moved to Washington State.  He used 1/8 inch luan for the top of the module, and just supported it every 12 inches or so with 1x2 dimensional lumber.  It was solid with no evidence of sagging anywhere.  If your chosen plywood tends to sag between supports, just add more support between the existing supports.  If you are using threaded rod with nuts and washers to support the helix on the inside and outside, just drill holes and add another threaded rod support halfway between every set of existing support rods.  To add the extra support, cut some small pieces of plywood that can be glued and/or screwed to the existing helix.  You put the rod through the small pieces of ply (one for each level on the helix) and then set the space with your nuts and washers after fastening them to the helix.

Very nice helix, kudos! But

Very nice helix, kudos! But I'm curious why you didn't just run the power buses vertically? It would have served the same purpose and used less wire...

John

Nickel-Silver contains no

Nickel-Silver contains no Silver. It's a Copper-Zinc alloy.

Very Nicely built Helix But

I pitty the pore Dispacher stuck in that pit. I can see it now:

:and watch your elbows.