# Terminal Track Wiring



## Grandcheapskate (Jan 5, 2006)

Hi Guys,
I am going to redo my terminal/jumper tracks to hopefully make a better undertrack connection. The current terminals/jumpers use a solid wire soldered to the rails under the track - as most of you have probably done, although standed wire may be the better choice.

But my question is not about the various methods used (there are other older threads on that subject), but rather about wire size. It's pretty obvious that you can't solder a very large diameter wire to the underside of plastic track.

So let's say you wired your track with some pretty good size wire to handle a decent amount of current - even if you don't plan on putting that much current through the wires. Let's say you went with 14 or 16 guage wire. That wire is too heavy to solder to the underside of plastic track, so you have to use something smaller here and connect it to the larger wire.

Doesn't this negate the advantage of having the heavier wire?

Thanks...Joe


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## FLASH (Nov 7, 2006)

Joe,

Just picture water flowing through a fire hose that suddenly reduces to a garden hose. That is what happens when going from a larger wire to a smaller. The current will flow but you lose a lot of efficiency. Depending on what cars you run, 14 gauge will be fine but 12 is a little better. I know you didn't want to know a method but I would really suggest at your taps to drill a hole against the rail all the way through the track and then the table. Run your wire up through the hole and solder directly to the side of the rail. You can then clip or grind down the excess wire to make it flush with the rail. I can take pics of mine if you need. Hope this helps.

FLASH


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## SwamperGene (Dec 1, 2003)

Grandcheapskate said:


> Hi Guys,
> I am going to redo my terminal/jumper tracks to hopefully make a better undertrack connection. The current terminals/jumpers use a solid wire soldered to the rails under the track - as most of you have probably done, although standed wire may be the better choice.
> 
> But my question is not about the various methods used (there are other older threads on that subject), but rather about wire size. It's pretty obvious that you can't solder a very large diameter wire to the underside of plastic track.
> ...


 
Joe I solder 14 AWG stranded to the bottoms of the rails _all_ the time. 

Also current capacity is related to length as well, and since shorter lengths induce less resistance the differences in voltage drops (thus current capacity) between say an 8" or so piece of either 12, 14, or in most cases even 16 AWG are negligible. Just look at fuses for an example...you don't see a big ol' chunk of 12AWG inside a 10 amp fuse.

:thumbsup:


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## Rolls (Jan 1, 2010)

Gene makes an important point about the length of the smaller gauge wire. The resistance of any wire is proportional to its length, so, within reason, smaller gauge wires in short runs are generally not significant. The wiring to and inside a Parma controller is a good example. Small wires, but short lengths.

On the other hand, you might not even care to use smaller gauge jumpers. As long as the the wire is stranded copper, I've had very good experience soldering 14 and 16 AWG to Tomy rails. Good luck!


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## Grandcheapskate (Jan 5, 2006)

Thanks guys.

I don't know why it didn't occur to me before that the wires soldered to the terminal track should be at least the gauge of the rest of the wiring.

I had soldered short lengths of wire to each terminal track and put a plug at the end so that I could simply "plug" my terminal track into the existing wiring. Plus, should anything happen to a terminal track or the soldered connection, I could "unplug" it from the rest of the wiring and fix it. But those short wires are of a different type (solid verses stranded) and probably a different gauge from the main wiring.

So it's off to the store for some 14 or 16 gauge stranded wire to be used for both the terminal tracks and main wiring (yes, I think I will rewire the track as the exisiting wire is 20 gauge speaker wire). I haven't had any real power issues (nothing other than stock cars here), but I do want to hook up a real power supply, so I'm going to want sturdier wiring.

Just an aside. I experimented today with soldering a piece of rail (removed from another piece of track) to the underside of a jumper track. I am trying to test whether I can solder in a piece of rail at a 90 degree angle to the track rail (exposed on the underside of the track) and then use that as my solder point for the wiring. Once you can get the solder point away from the plastic, it becomes easier to work with. It was easy enough to get rail to solder to rail, although I used a piece of track which already had some of the plastic ground away, providing easier access to the track rail. Is it worth it? Maybe not. I'll have to see.

Thanks...Joe


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## Dyno Dom (May 26, 2007)

I have #12 wire from power supply, thru track switch to terminal barrier
that is common for 6 lanes. Each individual power line to driver station is #14.
The smaller wire would make a difference if the power taps for each lane
are in series. (Power tap to power tap) You could have smaller wire for each power tap independent to a common terminal barrier or larger common supply
line. The smaller drop tap lines for soldering ease would be adequate for that
portion of track per lane.


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## AfxToo (Aug 29, 2003)

Re: current capacity is related to length as well...

Not really. If we are talking about true *current capacity* this is not true. The wire cross sectional area and conductivity of the wire affects current carrying capacity. So does frequency, but since we are at DC we don't care. This is a raw characteristic of the wire. The wire length most definitely affects the _effective current_ that is able to flow through the wire. It's very important to look at both factors, capacity and effectiveness, when wiring your track. The raw current capacity is something you will use to size your track wiring and to design a protection/safety strategy. At the same time you must also look at wiring size and wiring lengths to decide on how to wire your track for best effectiveness. 

The Current Capacity Perspective:

If you look at the current carrying capacities of various gauge wire like here:
http://www.powerstream.com/Wire_Size.htm you will see that the current capacity increases with lower wire gauge numbers (AWG) because the wire has more cross sectional area. The number we really care about from the chart is the max amps for chassis wiring. If we attempt to run more current through a wire than it can handle, the wire melts and becomes an open fuse or causes some heat related damage to the track and/or your house. 

For the sake of argument, say we are sizing our track wiring to handle 10 amps per lane for a 4 lane track. If we have a single feeder from the power supply or battery feeding into 4 lanes that are split out individually then the main feed must handle 40 amps. This means that you had better not use anything lighter than 12 AWG (41 amp capacity) for the main feed, and you'd be better off with a 10 AWG (55 amp capacity) main to feed 4 lanes at 10 amps each. Likewise, if each lane and its taps are going to be handling 10 amps then you'd better not use anything lighter than 20 AWG for the lane wiring and lane taps. 

So what does this tell us? It tells us that if don't want to melt our main feeder line or our lane/tap wiring and still get the required current to the lanes we'd better put at least 20 AWG wire and 10 amp protection on every lane feed and 12 AWG wire and 40 amp protection on the main line. This assumes we need to provide 10 amps per lane and don't want to melt our wiring. Note that this is just looking at numbers and wire sizing based on capacity. Few slot car tracks require 10 amps per lane continuous. In any case, apply some sound judgement and size your wire according to capacity, with margin, to meet your needs and also enforce the capacity limits (again with margin) using protection devices like fuses and circuit breakers designed for this electrical application (for example use DC circuit breakers and read their spec sheets to understand their trip characteristics). 

The Effectiveness Perspective:

If you look at the various wire sizes (gauges) you'll see another characteristic called resistance per unit length, say in ohms per 1000 feet. This tells you how effective the wire is at transferring power. An ideal wire would pass all of the power as you put into it. In reality, some power is lost along the way. The amount of power lost is proportional to the per-length resistance of the wire. For the same conductor material a lower gauge number wire will lose less due to resistance. The web link above provides a handy calculator to compute the losses for each wire size. For example:

According to the calculator, at 12 volts, a 12 AWG wire will drop about 33 millivolts per foot while a 14 AWG wire will drop 52 millivolts per foot. What does this tell us? It tells us that once we have decided on a wire size to handle the required capacity, and applied the proper protection on top of this so we don't melt our wiring and catch the house on fire, we should also look at our wiring and tap lengths and make sure the wire size we pick is effective from a voltage drop standpoint. Can we trade off shorter lengths of a lighter gauge wire for a longer length of heavier gauge wire? To a point, yes as long as we are not violating the capacity limits. In any case, I'd recommend the following:

1) Size and protect your wiring based on the current capacity of the wire and the needs of your application. How much current do you need to handle?
2) Design your taps so they use identical wire size and length at every tap point. You want to equalize the voltage drops to all lanes.
3) Do not undersize the wire used for the taps to the point where they compromise the protection of your track.
4) If you have a variable power supply and if you must run races at a certain voltage and current, you should check the voltage at the reference point (like at the drivers stations) and make adjustments to the power supply to establish this reference voltage and compensate for the voltage drops in the wiring. If you didn't equalize your per lane wiring and taps then you may have differences between lanes. Lane rotation takes care of this.
5) If you cannot compensate for the voltage drops, do everything you can to make all drops the same at the same tap point for each lane. 

The water pipe analogy, going from a heavy gauge feeder to a lighter gauge tap, is going to reduce the effective current flowing to the tap because of the higher voltage drop in the lighter gauge wire. But the biggest thing to watch out for when you go to a lighter gauge wire for the taps is that you don't go so small that you exceed the current carrying capacity of the tap wire at the required maximum operating voltage.


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## SwamperGene (Dec 1, 2003)

> The wire length most definitely affects the _effective current_ that is able to flow through the wire


This is what I was getting at, and why I specified 12, 14, or 16 AWG as an example. 

And you're right, it _very_ important to use a heavier gauge from PS to the "breakout" point where the lane wires go separate....I use 8AWG myself. :thumbsup:


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## Grandcheapskate (Jan 5, 2006)

If I am reading that chart correctly, AWG 20 gauge wire can carry 11 amps. So if my track uses one Aurora power pack per lane, and each lane is wired seperately, AWG 20 wire is more than enough for the power I have in the track. In fact, it would be sufficient for a 10 amp power supply if all four lanes were wired directly (and seperately) to the power supply.

Correct?

Thanks...Joe


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## Rolls (Jan 1, 2010)

Yes, that's correct, but it's correct from a current capacity standpoint (given the wire stays at the temperature specified and it fits the margin of safety that you're comfortable with). But AfxToo points out that the current capacity standpoint is really answering a pretty limited question - can a wire of the specified material and diameter move the specified amount of current through it or will it burn up trying, like the little wire in a fuse burns up?

Given the wire gauge passes the current capacity hurdle, I think AfxToo is saying that then its useful to look at how effectively it can carry a given amount of current over the lengths of wire of interest to you. Simplifying a tiny bit, that boils down, in our context of track building, to how much voltage voltage will it drop per foot as it carries current to your car at that power tap (I'm specifically ignoring any effects of power dissipation heating the wire as negligible for simplicity). 

If you have a 12 foot length of wire and the gauge you chose drops a tenth of a volt per foot per the calculator, can you live with the 1.2 volt drop just from that wire? Maybe you want to go to a thicker wire which drops only 0.25 volts over the 12 foot length under the load conditions you care about. The thicker wire will carry the current more effectively because that thicker wire offers less resistance per foot (so it drops less voltage per foot when its carrying current). Even though the thinner wire can carry the desired current w/o vaporizing, it doesn't carry it as effectively as the thicker wire. 

That's why I think it makes a lot of sense to break it down into two questions as AfxToo has above.


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## AfxToo (Aug 29, 2003)

Joe - yes, it would work, but look at the voltage drop at the higher current levels to see why you wouldn't want to use 20 AWG wire if you really need 10 amps to the track. You'd be losing about 200 mV (0.2 V) per foot of wiring. That would add up. Plus, a 1 amp margin is pretty thin. However, with a typical 500 mA or less stock HO car and reasonable power supply to track distance a 10 mV (0.01 V) drop per foot is acceptable and 20 AWG would work just fine. A ten foot wiring run would lose 0.1 volt.

Note that if you have multiple power taps the effective resistance of the wiring goes down dramatically, to less than one half of the base value without multiple taps. 

Note also that the resistance in the track rails, resistance in the controller wiring, and contact resistance for all connections are typically much greater than the resistance of the track wiring unless you have the power supply very far away from the track. 

Like anything else in the hobby, you need to decide how far you want to go to design your track for all possible contingencies and how you handle inherent and emerging limitations. It's obvious that you can run a snap together plastic track with the wall wart power supplies and thin gauge wiring that comes with the set. It will work and you'll have a lot of fun. As you add more track length you may want to add a jumper to reduce the voltage fall off that occurs when you get further away from the power supply. As you run hotter cars you may want to beef up the power supply and/or isolate the lanes to reduce or remove the power surge effect. Taking a wait & see, or observe & correct, approach is perfectly fine. Another approach is to design your track going-in for all possible contingencies. You may want to be able to run cars that draw high current continuously, or design your wiring such that the voltage and current at the drivers stations is very steady and does not drop off at all under load. It's all a matter of how far you want to go with it, but within a fairly wide tolerance, it is pretty hard to get it totally wrong.


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## Crimnick (May 28, 2006)

10 to 14 to 18 to rail...

I used 18 solid for the last leg from the terminal strips to the rails...no problems what so ever...


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## Grandcheapskate (Jan 5, 2006)

This electrical stuff always gives me a headache. This one isn't as bad as some of the others however.

If I understand correctly, the problem with 20 AWG wire may not be with it's ability to handle the max current produced by the power supply, but rather how much of a voltage drop will occur over a given distance.

I am currently using one Aurora MM power pack per lane (22v) and no car hotter than a stock Tomy, Tyco, etc. The table is only 7.5' x 5', so the longest run is well under 10'. I am going to assume that none of these cars will call for more than 2 (maybe 3) amps max at startup, which I understand is the point of the largest current draw. Since these power packs can't put out very many amps (probably less than 3), I won't approach anywhere near the 11 amp capacity of 20 AWG wire.

So, can I then conclude that for my particular setup, AT THIS TIME, 20 AWG wire is not a problem and I do not need to rewire?

Thanks...Joe


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## AfxToo (Aug 29, 2003)

You're fine Joe.


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## Hornet (Dec 1, 2005)

Hokay you engineers.
What happens to stranded wire when you solder it,it becomes solid wire right.
Unless you got the patience of Jobe and more time on your hands then God,and actually separate and individually solder each strand by itself,there's not much advantage to stranded wire for wiring a slotcar track,as each solder joint effectively acts as a restricter plate,especially if the joint is in the middle of your wire run.
Build some welding cables,or high amp draw starter cables boys,you don't solder them,you crimp them,and if your daddy taught you to fill the crimp joint with solder he's wrong.
Also if Joe's running a 1 or 2 amp fuse inline with the track and his controller,doesn't the fuse become the limiting factor,you can feed one side of that fuse with a 00 welding cable and there's still only a certain amount of amps it'll pass before it blows,as it act like a shock absorber in the electrical system.
I'm no engineer,but i do have some experience with building high draw welding and electrical cables,and i'd like you pair of engineers to explain how soldering a wire doesn't turn it into a solid core wire:wave:


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## Rolls (Jan 1, 2010)

Good questions, Hornet. I'll answer, but others might want to add/change argue...

You're right - soldering stranded wire does pretty much make it solid at the point it's soldered. But that's ok. 

The first reason I'd use stranded on a track is because it's more flexible. It bends easier and you can pull it through a small hole for strain relief easier if you choose to. Stranded will also tolerate your bending it a few times where a solid cable kinda hardens up after you bend it and gets more brittle at the bend point. 

Second, when you're soldering to a rail for a power tap, the stranded wire can sort of absorb the rail and get a good solder joint on both sides of the rail at once. No biggie, though, solid can still do the job, too. I just find stranded to be better suited for flexibility and solderability.

Now you're also dead right on your fuse observation. The fuse vaporizes when you exceed is it current capacity. But there's a reason you don't want to use that tiny thread of wire in the fuse for the whole length of your wire run - it has too much resistance *per unit length.* (The fuse has a small resistance (like a tenth of an ohm) when it's not blown, but its tiny wire has a very high resistance per unit length.) 

In normal operation, that is, when you're below the current level that the fuse will "shut down" your wire, you want the wire to have as little resistance as practical, so you don't drop too much voltage per foot in your wire run. So you want a thicker gauge wire which has a low resistance per foot. You want the voltage that you meter out with the controller to get through the wire to the rail at the power tap. If you drop too much voltage from resistance in the wire, it's like you never really get full throttle from your controller. Thicker gauge / lower resistance wire matters less the less current you're asking it to carry. 

So for box stock, less than an amp cars, you're pulling less current through any wire you choose, and with less current through any resistance, you'll drop less voltage. So it doesn't matter as much. That's why Joe's a-ok with his 20AWG wire. But if your car might draw 5 amps, it's 5 times the voltage drop from the wire and 5 times as big a deal. (It'll also blow that 1-2 amp fuse if you left it in place, too.)

Power taps also make a big difference. That's because you're asking each wire to carry only a fraction of the total current the car needs. With 5 taps, each wire run from the power supply to the tap is carrying (roughly) a fifth of the current that it'd have to if you had only one power terminal for the track. All 5 taps are sharing the current-carrying duties (assuming you don't have 2 or more bad track joints in a given lane - it gets a little messy there because the "sharing" goes all outta whack).

So even though I'm on board with both of your points, for track wiring, I'd still recommend stranded wire over solid, and wire of a reasonable thickness rather than runs of phone wire. But as you can see peeking in the back backside of my timing gantry, I've got nothing against skinny solid wires in some places:











Anyway, hope that reasoning makes it clearer or at least helps insomniacs quickly doze off to a good night's sleep. 

Hope it helps!


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## Hornet (Dec 1, 2005)

LOL touche'.
I agree with you on the stranded wire being easier to work with,but i disagree on using an AWG wire guide on stranded wire after it's been solder'd,as it's no longer AWG wire.
Rolls my track is total overkill on wiring,10g from power supply to drivers stations,then a 12g main wire frame,that get this feeds each and every piece of track on my table,yes "every" section is drop wired,not jusy a 1/2 doz power taps,i got 90 power taps,and you know something,upgrading to that wire scenerio didn't make a damn bit of differance in lap times or heat from my cars,and i run nothing but drop-in-neo cars.
Yes i agree,run as big a wire as you can,but more importantly,drop wire many more sections then just a couple,as the wire size usually isn't the limit,the track connections are as you've stated.
BTW,i run 2 amp fuses with drop-in-neo cars,no problem,that milli-second high amp draw isn't long enough to blow my 2 amp fuses,so i highly doubt it's putting strain on the wire.
Also once you've solder'd stranded,i disagree with your theory on it's flexability,it becomes very prone to breaking at the solder joint,compared to a solder'd solid core wire.Ever seen a solder'd electrical joint in your automobile from the factory,there's a reason the big automobile manufactures don't solder wires,and it's the life expectancy of the solder'd joint,it's very poor:wave:
I'm not saying don't use as big a wire as you can,just that it's not as big a factor in the equation as most guys think,the bigger factor is the amount of power taps,more is better


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## SwamperGene (Dec 1, 2003)

Can't back you up on this one Rick, I don't think the soldering issue makes a difference either way. Actually, I know it doesn't as I've run plenty of load tests across soldered joints and they exhibit no voltage drop at all under more than our typical loads. I can't say the same about crimped connections - which can expand and contract, allowing corrosion to form inside the crimp. I've seen crimped connections fail during races, never a soldered connection if they're done right. 



> Ever seen a solder'd electrical joint in your automobile from the factory,there's a reason the big automobile manufactures don't solder wires


Coming from 25 years in the industry....yes. Like even your run of the mill cheapo crimp connectors, many times the connectors used in the automotive field are pre-tinned and heated after they are crimped. Take a soldering iron to just about any typical crimp connector you have laying around and you will likely see it change from pale gray to shiny silver as the solder melts.


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## AfxToo (Aug 29, 2003)

Not sure where the solid versus stranded controversy is coming from. Yes, tinning your wire ends and soldering them to solder terminal lugs will stiffen them up. If you are using this technique on your boat, Baja racer, or other such shaky, stressful, high vibration environment then you had better have some sort of strain relief in the design. For the most part, the decision to use solder versus crimped connections in manufactured products and assemblies comes down to the quality of the job and the adequacy of the tools being used. 

Soldering well requires knowledge, preparation, proper tools, proper handling, and skill. If done correctly it's a highly effective and reliable means of making electrical connections and terminations. In high stress applications soldered connections must be accompanied by proper mechanical design, wire supports and stress relief, and joint sealing to keep out moisture, especially in corrosive environments like chemical and salt water spray. 

Crimping well requires exactly the same things stated above for soldering. However, with the proper crimping tools the skill required to produce a reliable connection is somewhat reduced versus soldering. These tools don't come cheap: http://www.etool.ca/RENDER/1/56/500/4646.html for an example. Proper crimping - something that will produce soldered joint performance - does not involve a pair of pliers or one of those multipurpose wire cutter/stripper/crimper/screw trimmer tools. Crimping requires skill and knowledge, things like not twisting the wire strands that you are going to crimp, not touching the bare wire with your fingers, and applying the exact right amount of pressure. Having a crimping tool designed especially for the wire and connectors you are using is absolutely critical. In high volume manufacturing applications the crimping is often down using fully-automated or semi-automated machinery. In high stress applications crimped connections must be accompanied by proper mechanical design, wire supports and stress relief, and joint sealing to keep out moisture, especially in corrosive environments like chemical and salt water spray.

A crap crimp job is no better than a crap solder job. I've encountered both kinds over the course of my career.

I've already made the case for jumpers. They work. How many? As many as you need. There is nothing wrong with the "observe & correct" approach. Is one spot of your layout a little soft? Adding another tap there may work wonders.


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## Grandcheapskate (Jan 5, 2006)

Rolls said:


> Power taps also make a big difference. That's because you're asking each wire to carry only a fraction of the total current the car needs. With 5 taps, each wire run from the power supply to the tap is carrying (roughly) a fifth of the current that it'd have to if you had only one power terminal for the track. All 5 taps are sharing the current-carrying duties (assuming you don't have 2 or more bad track joints in a given lane - it gets a little messy there because the "sharing" goes all outta whack).


 I think I'm going to hate myself for asking this, so before I read the responses, I'll take two aspirin.

Assume a power supply capable of producing 10 amps, your track has 5 power taps and all track connections are good. Also assume we are only talking about a one lane track. Based on the above statement, are you saying that the wiring only needs to be capable of handling 2 amps (okay, maybe 3 for safety) because the current load is shared five ways?

Thanks...Joe


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## Hornet (Dec 1, 2005)

Yes basically Joe,if you got enough power taps,it doesn't make much differance if the tracks wired with 20G or 12G and it doesn't make much differance if you use solid core or stranded wire,so if you've got a pile of 20G laying around don't roar out and spend a bunch of money on wire that won't make any damn differance in how your car performs.
That's what i was trying to get across,if you've got lots of light duty wire laying around,use it,it'll work just fine.
The wire size in our hobby won't make any damn differance in the laptimes the car will turn or it's heat factor,as long as you got enough power taps:wave:


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## Rolls (Jan 1, 2010)

Grandcheapskate said:


> I think I'm going to hate myself for asking this, so before I read the responses, I'll take two aspirin.
> 
> Assume a power supply capable of producing 10 amps, your track has 5 power taps and *all track connections are good*. Also assume we are only talking about a one lane track. Based on the above statement, are you saying that the wiring only needs to be capable of handling 2 amps (okay, maybe 3 for safety) because the current load is shared five ways?
> 
> Thanks...Joe


Yep! As long as your well-chosen assumptions hold true, that's what the current-sharing aspect of having multiple taps buys you. Put that aspirin bottle back on the shelf! :thumbsup:


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## Hornet (Dec 1, 2005)

I kinda like beating a dead horse:thumbsup:
Lets take 2 identically built tracks,i know won't happen,in the real world,but hypothetically.
Both are say 60 ft long,one is wired with (3) 12G power taps,one apprx every 20 ft,the other track is wired with 20G,and it's wired with the conversion factor to make it equal to the voltage drops and amps supplied by the (3) 12G power taps,i'm not sure what the conversion number would give,i'll leave that to the experts,but it's probably gonna give you at least 3 or 4 times the number of power taps.
Both tracks are now identically fed the same power and amps utilizing voltage drop conversions,only thing is the track wired with 20G has say a dozen power taps,compared to the 12G's 3 power taps,which track is gonna be the one with the most voltage drop at the farthest point away from it's power taps at the rails,doubtful it'll be the track with the dozen power taps that's only got a 5ft barrier of rail to power,i'd think it'd be the track with only 3 power taps and a 20 ft spread between powertaps.
Also know which track i'd rather race on:wave:
Wire size ain't as important as number of power taps,don't upgrade to bigger wire,upgrade to more power taps.
The size of your wire ain't that important,it's the quality of the job,just ask your better half:wave:
The fuse is still the final link in the equation, you can have it tied directly to General Electric's High Tension line,and it's still only gonna pass so much power before it lets go.
So for you guys who think upgrading from 18 or 20G to 12G is gonna make your cars run faster and cooler,you could be slightly disappointed as you might not find as big a benefit as you'd probably like ,you'll get a bigger benefit,by adding more power taps


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## jensen b (Nov 3, 2009)

stranded wire every time:thumbsup:


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