# Power drops



## vette-kid (May 2, 2020)

Ok, I know what most on here recommend and what the books say. Here's my experience so far. 4'x12' (ish) layout. Double oval with two interchanges in HO scale. At the furthest point I get a 0.02 amp drop across either loop. That is with one single power connection with 22ga from the power supply, about a 5" lead. I had planned several connection points using a bus wire, but it just doesn't seem necessary. We ran 3 locos on it full speed with no noticable performance loss.

So convince me why I should run a power bus? Since I already put several leads on real joiners, I plan to just hide them for future use should it be necessary for some reason. But convince me why.










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## Aard D'Vaark (Aug 1, 2019)

i run a 10 gauge bus, with 20?? gauge drops every [roughly] six feet .. why ?? i don't want to go back under there again for something so trivial and silly ...and the cost difference is very little ..my layout is fifteen feet by sixteen feet ..


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## mesenteria (Oct 29, 2015)

You won’t benefit much from a bus. Larger layouts will, but not because of amperage loss. It is voltage loss that causes an increase in signal to noise problem, and that’s an issue only with digital, not analog. A bus minimizes voltage loss over much longer distances than you have.


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## vette-kid (May 2, 2020)

Meant to say voltage drop, not amps. 

So with this size layout, if I switch to DCC will it be a bigger factor? I estimate there is about 60-70ft of track and could add maybe another 20ft in the future.

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## mesenteria (Oct 29, 2015)

I would think that a pair of feeders on ether side of what you show in the photo would serve you well, provided they aren’t less (thinner) than 22 gauge, and not more than maybe 3’ in length. Longer and thinner feeders means voltage loss. Even a short bus 5-7 feet long of 14 gauge wire would help to keep feeders short, and would be useful extended when you grow your track system in the future.


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## gregc (Apr 25, 2015)

while you said a 0.02V drop, you didn't say at what current. the voltage drop is proportional to the current being drawn

small gauge wire is ok for short distances. 22g wire has ~0.02 Ohm / ft. but i've read that nickle silver track is the equivalent to 26g wire (despite being so thick) which has ~0.04 Ohm/ft resistance. 12' of rail is ~0.5 Ohm or ~1 Ohm for 2 rails, but it's an oval so 2 rails reaching the same point (i.e. ~0.5 Ohm total).

if the loco draws 1A, there will be a ~0.5V drop which may not be noticeable especially since a loco us more likely to draw closer to ~0.5A.

so it's up to you. if it's an issue, add another feeder on the opposite side of the oval (use 18g wire).


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## vette-kid (May 2, 2020)

gregc said:


> while you said a 0.02V drop, you didn't say at what current. the voltage drop is proportional to the current being drawn
> 
> small gauge wire is ok for short distances. 22g wire has ~0.02 Ohm / ft. but i've read that nickle silver track is the equivalent to 26g wire (despite being so thick) which has ~0.04 Ohm/ft resistance. 12' of rail is ~0.5 Ohm or ~1 Ohm for 2 rails, but it's an oval so 2 rails reaching the same point (i.e. ~0.5 Ohm total).
> 
> ...


Thanks for that, I should have tested under load. I'll try that later and see what it does out of curiosity.

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## flyboy2610 (Jan 20, 2010)

One reason for feeders is short circuit protection. If the system cannot detect the short, it will not shut down. It will just keep pumping amperage through the metal object causing the short. If the amperage of the system is high enough, you could wind up with one of these:









Wire is cheap. Locomotives aren't. Knowhutimean, Vern?


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## CTValleyRR (Jul 26, 2014)

I have always been of the opinion that power feeds to layouts are very over engineered. My son also runs a layout with a size comparable to yours (an 8x8 L shape) with only a single pair of AWG22 feeders.

Extra feeders aren't necessary, they're just insurance. To avoid the situation flyboy shows above, donthe quarter test: go to the farthest point from your feeders (traced along the rails) and deliberately short the track using a quarter, a washer, or some other metallic object. If the breaker trips, all is well. If not, add a feeder or two.


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## gregc (Apr 25, 2015)

i'm not sure how reliable rail joiners are for power over time. i think soldering a feeder to every other rail joiner as well as soldering that rail joiner to both rails guarantees a solid connection to every rail. track/layout expansion is still possible since every other rail joiner isn't soldered


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## Lemonhawk (Sep 24, 2013)

Did the OP mean 0.02 volts rather than amps? Also to me, the main reason for feeders is to avoid reliance on joiners to carry power, at some point in time they will fail at this. It's also nice not to have to solder every joiner, hence I solder 2 3' rails together and use a power drop to the section. All easy the during the build to do, but can be torture to do afterwards. I use 16 gauge for the buss and 20 gauge for the feeders as the layout is only 5x9+


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