"I would run them in the 6 gage size for up to 200 feet, no need to worry about voltage drop,"
I have some 00 cable left over from running the under ground line out to my shop maybe that will work even better! You won't have to worry about voltage drop just your bench work collapsing.had email correspondence with Cliff Power of the MA&G who built one of the nicest looking double track helix's you've ever seen and now where did he mention running feeder wires as part of the helix. We duplicated his helix on my friends layout and all we did was have a pair of feeders at the top and a pair at the bottom of the helix and he hasn't experienced a single problem in almost two years now.
As well as the loop thing being very over rated and beaten to death like a dead horse is the issue of running drops. Some guys in our club feel you absolutely have to run a pair of drops on ever 3' section of flex track others think you have to connect each section of flex track by soldering a connector wire from one to the other instead of soldering rail joiners other still insist that you only need to solder every other rail joiner alternating sides.
The bottom lie is do what ever you feel comfortable doing. You have one not commonly talked about benefit of a helix, it doesn't have to look pretty all it has to do is work and work well. So if you want to add more work and solder feeders to buss wires under each turn of the helix then knock your socks off If you want to solder rail joiners or connectors wires on the outside webs that show then do that too. The thing is more then likely your never going to have a single problem with an electrical issue if you just do the same things that you do with regular track work, it's just that if you don't do what makes you comfortable it's going to bug you every time a train enters that helix.
My apologies for adding to the confusion in an already confusing discussion. Now that the big day is over, perhaps I'm thinking more clearly.
Hopefully, the bugaboos of loop wiring causing signal interference have been sufficiently put to bed. Also, the question of NS rail conductivity is really not part of the problem - the discussion is about bus wires, not rail. Presumably gaps will be cut (or left) in the rails to allow for thermal expansion/contraction. Thus jumpers will be needed at intervals from the bus wire.
The question was: what kind of bus system to use for a track section of 10 ft out, 1.5 turns of a 34-in rad helix, and 10 ft. back.
The helix length is pi*D*1.5 = approx 17.8 ft. The max voltage drop would occur in the vicinity of the helix, if both ends of the bus wires are connected to the booster. Whether there is a 'gap' in the bus wires near the helix or not is really immaterial (see previous discussions). So the total bus wire length to the point of max voltage drop is approximately 10 ft + 9 ft = 19 ft, if the bus wire follows the 1.5 loops of the helix.
The 2 % voltage drop length for #14 copper wire is about 22 ft, and about 35 ft for #12 wire, assuming a 2 amp load at 12 vdc (ref: http://www.solarseller.com/dc_wire_loss_chart___.htm). Two percent of 12 volts is about a quarter of a volt. Our 2-amp engines would be running at about 11.76 volts - not a terrible situation, nor a significant loss.
Upshot: the choice of wiring methods here is immaterial, from an electrical standpoint. The installation of bus wires should be made as convenient as possible for the builder / maintainer.
Again - sorry about the confusion.
How are the levels of your helix supported? Usually there are vertical members spaced evenly 4x (or more) around the perimeter (and/or up the middle), so run the wire there - it wouldn't interfere anymore than running around the edge.
Let's assume #12 wire for the bus. 0.00817 ohms per foot resistance. With a load of 4 amps total.
1.5 feet (total of 3 feet of wire) = .00561 ohms. E=IR, so 0.022 volt drop - barely measurable by 'consumer' multimeters.
vs 70.65 feet followign the helix. 141.3 feet. .264 ohms, 1.05 volt drop. Significant.
ANd remember, that's just the rest of the bus. Say there was 20 feet of linear layout on the top level and bottom level. Vertical run up the helix, total would be .61 volts dropped vs 1.66 volts dropped following the helix.
It DOES make a difference.
ALso, 1.5 turns of 32" radius at 2% grade will only generate a rise of 6" - that's not too practical for a double deck layotu unless the lower level is ONLY staging, even even then I'd want some sort of drawer to be able to easily reach cars on said tracks. That assumes all vertical transitions are off the helix.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
No, actually any difference would be miniscule. Even in your hypothetical 4.5 turn helix (which we DO understand has the length you calculate..) the difference would be tiny.
However, the gentleman asked about a helix of 1.5 turns.
I would run the wire along the helix baseboard (the spiral) for simplicity's sake. The electrical difference is not worth discussing. Thinking about climbing in to re-rail derailed trains - do you want a light-cord like wire hanging down to interfere with? Not hardly.
Don't believe it? How about some measured data ???
We would do well to deal with empirical (and theoretical) realities - not the hyped guesses frequently used on here. For example, why not lay out some actual NS rail, gaps soldered, and a parallel piece of unbroken #14 or whatever 'bus' wire, and check the difference in voltage drop - if you can measure it? Such a set of data would be a great help to us all. I would do it but it's not worth the time and I don't have the kind of precision test gear required. Even most semi-expensive meters are not terribly precise.
Merry Christmas from snowy Montana, where sunshine was predicted only a few hours ago. People here are all in favor of Global Warming....
It's quite a big difference, actually. Say you have a 4.5 turn, 30" radius helix that rises 18".
Run the bus stright up, it's 18" of wire. But follow along the helix:
Diameter of each circle = pi * diameter, 3.14x60 (30" radius x 2) = 188 inches
188 inches per loop x 4.5 loops = 847.5 inches
WHich is 70.65 FEET. Versus 1.5 feet.
We often don't realize just how much linear trackage is involved in a helix.
Randy is right - there will be less voltage drop (but negligibly different) in a shorter piece of wire than in your (short) helix rails. Probably several millivolts.
The "loop" question is approximately equivalent to the fluff about sitting under pyramids. If you get a short connecting a loop, you have wired it incorrectly, period. Think of out-and-back as two wires in parallel. No short there.
If the much-feared and much-ballyhooed 'data collisions' actually occured, our DCC layouts would almost all come to a very quick halt. There are already so many paths around most layouts that 'data collisons' would be all but inevitable.
And no, there would be no harm whatever in connecting a house-power line in a 'loop' - slightly more cost, depending on length. And some extra reliability. It's done in aerospace quite frequently - and with signal / control circuits, too. Called 'redundancy', and quite valuable in risky operations.
So much for the 'loop' ballyhoo. We'd be well-served to avoid it as a serious topic. It's not.
#6 SOLID wire? What do you attach the feeders with, a torch? ANd #16 feeders - I can only assume this is O scale or larger, trying to attach #16 wire to HO or smaller track is going to look ugly no matter how good you soldering skills.
Granted, there should be no detectable voltage drop in extremely long runs of #6....
In all reality all you need is one positive bus wire and one negative wire, I would run them in the 6 gage size for up to 200 feet, no need to worry about voltage drop, and dead end them. solid copper wire not stranded. run your feeder wires 16 gage every 3-6 feet and you should have no problems at all, you can put circuit breakers in every so often to isolate sections, but as any one knows you still have to have gaps in your rails to prevent shorts. I run at my local train club with over 1300 feet of track and we have no problems with are system and we run a didgitrack dcc system for the whole layout with full automation.
Cheers
thanks for everyones input. I decided to just run two bus wires, no loop. Will work best.
In theory, a loop could cause signal problems. In practice, it's not very likely unless it was a very long loop. Like hundreds of feet long.
If one got a short by making a loop, they hooked the wrong wires together. In practicality, the rails may even be completing the loop for us, inadvertantly.
A loop actually could decrease the voltage drop, as there are two paths (at least) to any point on the layout.
All of that said, given the choice, I would not loop... it's just the engineer in me, though.
Jeff But it's a dry heat!
The whole 'loop' ting is way overdiscussed. My previous layout was basically a glorified double track oval plus a lot of extra stuff. I DID cut my bus wires but that was because I was planning to install a breaker to divide the layout into 4 power districts - basically each quarter of the oval. But the TRACK was not gapped - so there was a loop anyway! Plus what I did to power it all was run all the bus wires to a terminal strip where I installed jumpers to take the place of the breaker. To install the breaker (which I never ended up doing), I would have removed the jumpers and connected each section to one of the breaker outputs. With the jumpers in place, the bus technically looped as well as the track. No problems.
Now, if you run 20 feet left and 20 feet right out of your booster, it's pretty silly to run ANOTHER 40 feet of wire to loop the ends.
When it comes to the command bus, where you plug your thtorrles into, for most systems you should NOT create a loop there. The actual topology of the bus is system specific.
Allegheny2-6-6-6 This questions come up regularly, there is no valid reason to have the DCC buss wire connect back to itself to create a loop it serves no purpose other then to great a short.
This questions come up regularly, there is no valid reason to have the DCC buss wire connect back to itself to create a loop it serves no purpose other then to great a short.
Actually in some cases it reduces voltage drop.
In simple terms think of your DCC buss wire like the wire running through your house. It doesn't come back and make a loop does it?
That's because it's not needed but more important- it's cheaper.
I'm not an electrical engineer so I can't give you the technical explanation but when I connected the buss wire back on it s self it tripped the circuit breaker. I tried it just to see what would happen
Nothing should happen unless you connect the outer rail wire to the inner rail wire. Connecting each bus wire into a loop will not cause a short. Think of a simple oval of track. Two metal loops, no short.
I also would suggest avoiding the helix. It doesn't sound like it's going to be very big so soldering the rail joiners should prove sufficient enough for good electrical contact.
Run your bus wires right up the center as Randy suggested. Voltage drop through 25+ feet of soldered nickel/silver rail will be much greater than through a short length of copper wire.
Martin Myers
In simple terms think of your DCC buss wire like the wire running through your house. It doesn't come back and make a loop does it? So you run your buss wire under your track the entire length of your main line. connect drop from the rails to the buss wires you shouldn't go much more then 3 or 4 inches in length. keep the color coding consistent. No need to go out and buy two different color spools of wire for your buss. one roll of #14 Gage wire and the colored rolls of electrical tape. That is exactly why they make it, electricians use it to mark the main lugs on the service lines of your house.
Think of each separate district as a separate circuit breaker in your home electrical panel.All generating from the same source but going to separate parts of the house/layout.
Think of the dcc locomotive as the appliance you plug into the receptacle in your home. Until you turn on the light or the TV or call up the locomotive it just sits there with the power in the lines. Just as the electricity goes form your panel box through the wires to the outlets and there it waits till you plug something in.
What completes the circuit between the two wires or rails is the appliance or locomotive
We have something like 24 separate districts at the club and this is how it is wired and the guy doing it is a retired electrical engineer so I'll take his word for it when he tells me it's not how you do it.
I have seen the wiring on some of these large club layouts and it boggles one's mind how much is involved. I believe in keeping it as simple as possible to avoid problems. I do highly recommend putting a circuit breaker in line. I choose CVP products but there are a lot of others to choose form. I will make breaking thing up into districts a lot simpler not to mention protecting your expensive locomotives
If I were in your position, I'd check what the manufacturer of the DCC system reccommends. The key thing to remember is that you're sending a signal in DCC, as opposed to voltage in DC. If you've got a loop topology, the signals going in each direction around the loop will most likely interfere with each other ('collide') when they reach the other end of the loop. The result of this would be unpredictable behaviour from your DCC system and locos. This same principle applies in computer networks.
The Location: Forests of the Pacific Northwest, OregonThe Year: 1948The Scale: On30The Blog: http://bvlcorr.tumblr.com
DOesn't matter, but for the helix, don;t run the bus wire around completely parallel to the track. Run a set of bus wires straight up one edge of the helix and connect feeders as needed.
I am in the process of building a three deck layout 12 x 27. will be DCC (just running DC now)
I have 3 digatrax DB150' that I am going to use with 4 subdistricts each.I plan on using dcc specialties PSX4.
Here is my question: i am running one district as the double main line comming up (2% grade) from level one, about 10 feet straight, then going into a 1-1/2 turn heilx (32/34 radius) & back 10 feet starting 2nd level. I like to soder each piece of track. should i run the wire around and the connect back to itsself creating a loop or should i cut at the far end and make two runs out.
thanks