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Author Topic: Power Loss Going 'round the Bend  (Read 5730 times)
ChugaChoo

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« on: May 25, 2011, 11:59:22 PM »

I have an oval track (approx 8 feet by 4.5 feet, 22" radius, steel EZ track) using an MRC 280 Tech4 transformer running a Bachmann Steam Engine Class with Tender (J 4-8-4) pulling four cars.  I have decent speed except going around the far turn when the engine slows down noticably.  I've checked track connections, keep it clean but still have the speed loss.  Anything I can do to remedy my problem? 
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ACY


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« Reply #1 on: May 26, 2011, 12:04:39 AM »

Yes you can try replacing the steel track with nickel silver or adding an extra feeder by the curve, but make sure your track and wheels are actually clean, they can appear to be clean but that does not mean they are in fact clean.
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jward


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« Reply #2 on: May 26, 2011, 04:53:23 AM »

adding a second set of feeder wires near the turn should help. rail joiners can't always be relied upon to conduct electricity. that's one of the reasons i solder mine.

for reliable electrical pickup it is a good idea to provide more than one path for electricity to reach the rails.

if you do add a second set of feeder wires, make sure you don't get them crossed before you turn the power back on. your tech 4 is a good power pack, you don't want to have a short and damage it.
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Jeffery S Ward Sr
Pittsburgh, PA
ChrisS

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« Reply #3 on: May 26, 2011, 11:06:47 AM »

is the speed reduction due to power loss, or the fixed driver wheelbase binding in the curves?
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Doneldon

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« Reply #4 on: May 26, 2011, 04:29:14 PM »

Chug and Chris-

I agree that extra feeders and close attention to track and wheel cleanliness are key here. I'm not so sure that the rail material matters much as steel is an excellent conductor and light surface oxidation won't affect electrical transmission much with steel rail. Gunk on the rails and wheels will interfere, however. If you do add a feeder or two, use at least 16 ga stranded or 14 ga solid copper wire for the busses and 20 ga or 22 ga feeders. There's no point in sending a boy to do a man's job.

I expect curve binding to affect speed somewhat. Twenty-two inch curves seem pretty broad compared to the skimpy 18-inch curves in train sets, but they are still pretty tight for something like an eight-coupled locomotive. And it's not just that the loco wheels bind a little. Closely watch and listen to any of your trains as they move into and out of curves of almost any size and you'll notice changes attributable only to the curved track. This even affects the 12 inches to the foot railroads. In addition to elevation profiles, they also consider curves when setting tonnage limits for locomotives. Put a curve on a grade and you get an even greater effect than just adding the effects of grade and curve.
                                                                                                         -- D
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #5 on: May 26, 2011, 07:26:19 PM »

... use at least 16 ga stranded or 14 ga solid copper wire for the busses and 20 ga or 22 ga feeders..

Why the difference?

Jim
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jward


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« Reply #6 on: May 26, 2011, 08:53:36 PM »

that is the dcc way of wiring things. the larger wire size has less resistance, the smaller wire size is easier to solder to the rails. however, we are talking steel rail here, which is very difficult to solder to, and using any kind of flux to help with the job will cause the track to rust where the flux was applied. this is one of the big reasons i don't like steel track.
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Jeffery S Ward Sr
Pittsburgh, PA
Doneldon

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« Reply #7 on: May 26, 2011, 11:05:53 PM »

Jim-

The ampacity of stranded wire is equal to that of solid wire one size larger.

                                                                -- D
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ChugaChoo

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« Reply #8 on: May 27, 2011, 12:24:47 AM »

Adding the secondary feeder line did the trick.  Thanks for everyone's input.  First time I've used the forum and had some great comments and suggestions.  Happy rails!
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ACY


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« Reply #9 on: May 27, 2011, 12:44:57 AM »

Good to hear the suggestions were beneficial.
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #10 on: May 27, 2011, 12:51:49 AM »

Jim-

The ampacity of stranded wire is equal to that of solid wire one size larger.

                                                                -- D


But the resistance and therefore the voltage drop is not.  In fact the resistance of stranded wire may be several percent higher than solid wire of the same gauge.  If ampacity were the only consideration, 22 gauge wire would be large enough even for a 5 amp booster.  But at about 16 ohms/1000 ft. it would drop about 8 volts on a 50 ft. run.  On a typical one or two sheet layout, 18 gauge would normally limit voltage loss to less than one volt.  But having said all that, 14 gauge Romex house wire is cheaper, can be easily stripped out of its outer casing, and you get a free 14 gauge bare wire to use as a common return for lighting and other accessories.  We are both making similar recommendations but are coming at it from a different direction.

Jim
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railsider

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« Reply #11 on: June 17, 2011, 01:42:01 PM »

Good point about using Romex cable, Jim. Or you can use 14-ga. "building wire," which is the single-strand (Romex cable is usually two or three wires in a single cable, like household zip-cord only bigger).

The advantage, I suggest, to building wire is that you can get two rolls in two different insulation colors, and always use one for the positive track buss and the other for the return. Keep it the same everywhere, and you're less likely to get crossed wires and short circuits.

Bare wire for a common return isn't a bad idea if you have to solder to it at odd intervals, but you can just scrape a half-in of insulation back and do the connection that way if you prefer.
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Doneldon

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« Reply #12 on: June 17, 2011, 02:53:58 PM »

railsider-

Romex or non-metalic sheathed cable as they call it, also has different colored wires inside. You'll find black, white and green or bare in two-conductor Romex and black, white, bare and red in three-conductor Romex. Keep in mind that you don't have to solder to a bare ground wire. You can still use suitcase connectors or wire nuts. And if you do solder the ground joints, it's nice to have a new, recently uncovered copper wire which is all set for you. All you need is a little flux and you're in business.

Bear (npi) in mind that three-conductor cable can be very useful in model railroading. I wouldn't try to wire DCC or even DC blocks with it because of possible polarity conflicts with the common "return" wire, but it is very useful for accessory circuits. Since our low voltage lighting and animation circuits don't have separate ground wires, you can use black and white for one circuit and red and bare (or green) for another. I haven't done it myself, but I'll bet you could run three circuits on the black, white and red wires and use the bare or green wire for a common return. You will, of course, still have to use small gauge wire up through your train board and into your buildings or whatever.

And don't forget the economics. When you compare the price per foot of a spool of Romex with a spool of one conductor wire you'll find that the Romex is a pretty good deal. The only down side is that Romex is pretty stiff and you have to open the cable to get at the wires.
                                                                                                                 -- D
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