# reducing power in one of the rails



## mymodeltrain (May 14, 2013)

I have two rails that share one power box. The question is how to reduce the voltage in one rail. Since each train runs with different voltage as a consequence different speed. When I increase the voltage for the USA train to run with decent speed, on the other rail the LGB train runs too fast.


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## Bill Swindell (Jan 2, 2008)

One trick is to insert Silicone diodes in series with one lead to the train that runs faster. If that's the LGB engine, use 3amp diedes. Each diode will cause 0.7volt voltage drop. If you wanted to drop 1.5 volts, put 2 diodes in seri=es. You will need 2 more valves facing in the other direction. If you don't do that, you will not be able to reverse your engine. 

You could also use a heavy adjustable resistor instead of the diodes. The problem is that any change of grade will cause the engine to slow down quite a bit.


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## mymodeltrain (May 14, 2013)

"One trick is to insert Silicone diodes in series with one lead to the train that runs faster. If that's the LGB engine, use 3amp diedes. Each diode will cause 0.7volt voltage drop. If you wanted to drop 1.5 volts, put 2 diodes in seri=es. You will need 2 more valves facing in the other direction. If you don't do that, you will not be able to reverse your engine". 

Do you know if we could buy a ready-to-use kit with the design you just mentioned somewhere?


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## dbodnar (Jan 2, 2008)

Posted By mymodeltrain on 08 Dec 2013 10:36 PM 
"One trick is to insert Silicone diodes in series with one lead to the train that runs faster. If that's the LGB engine, use 3amp diedes. Each diode will cause 0.7volt voltage drop. If you wanted to drop 1.5 volts, put 2 diodes in seri=es. You will need 2 more valves facing in the other direction. If you don't do that, you will not be able to reverse your engine". 

Do you know if we could buy a ready-to-use kit with the design you just mentioned somewhere? 

Good day - the process of building such a diode speed reduction circuit is pretty straight-forward if you have access to a soldering iron - details on how to put it all together are on my web page here:

Diode Speed Control 

Please let me know if you have any questions.

thanks!

dave


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## mymodeltrain (May 14, 2013)

"Good day - the process of building such a diode speed reduction circuit is pretty straight-forward if you have access to a soldering iron - details on how to put it all together are on my web page here: 

Diode Speed Control 

Please let me know if you have any questions." 



Thanks Dave for the instruction. I think I can do it after learning from your sketches.


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## Pete Thornton (Jan 2, 2008)

pretty straight-forward if you have access to a soldering iron 
I suspect that this simple diode group could be made without soldering. You do have to keep the wires separate and tightly wound to each other (the ones supposed to be touching, that is.) Use a piece of cardboard as a base, and punch holes in it so the diodes are on one side and the other side has the wires. Twist the ones you want to join with pliers.


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## John J (Dec 29, 2007)

You could use Butt Splices. If you cut the leads of the Diodes short enough that when inserted int he Butt Splice the Splice is up against the housing of the diode. Then crimp them real tight. 

The only draw back would be Corrosion between the Butt Splice and the Diode lead. 


JJ


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## Dan Pierce (Jan 2, 2008)

While twisting leads together will work, in time corrosion will win and a bad connection will occur.

I was taught that soldering wires together is not for conduction, it is really to keep the joint of 2 wires twisted together from corroding.

Note that all metals will corrode in time, even gold!!


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## cape cod Todd (Jan 3, 2008)

Why not use this little annoyance as a feature. When I mix up my trains, LGB, USAT, Bachmann they all run at different speeds and I use this as an excuse to bring one into a siding to let the other pass. I have 3 spots on my RR where I can let a train pull in, kill the track power and wait for the other train to pass then let the slower train proceed. Sometimes I will hold the faster train on the siding depending on what it is hauling. Fun times and it keeps it interesting.


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## mymodeltrain (May 14, 2013)

"Why not use this little annoyance as a feature. When I mix up my trains, LGB, USAT, Bachmann they all run at different speeds and I use this as an excuse to bring one into a siding to let the other pass. I have 3 spots on my RR where I can let a train pull in, kill the track power and wait for the other train to pass then let the slower train proceed. Sometimes I will hold the faster train on the siding depending on what it is hauling. Fun times and it keeps it interesting." 

It's a good idea, but these are two different rails; I think that design is not applicable since one rail is on the ground and the other is elevated and they are not connected.


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## Pete Thornton (Jan 2, 2008)

even gold!! 
Dan - how long do we have to wait ? 20,000 years?


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## mymodeltrain (May 14, 2013)

"Dan - how long do we have to wait ? 20,000 years?" 

I think it can be right or wrong since Dan did not specify what types of gold. I was trained as a jeweler when I was young and I also worked in chemistry so I think am qualified to answer this. Pure gold is inert to the environment so even million years of exposure to environment is fine. Even strong acid like nitric acid has no effect on pure gold. That's why jeweler use nitric acid to test pure gold against other grades. But 20, 22, 18, 10 K will be affected by environment since those are an alloy of pure gold and a mixture of silver and copper. Depending on the taste of each jeweler you can add more silver than copper or other way around to generate a unique color. And as we know silver and copper can be oxidized very easily under normal environmental conditions such as acidicity, basicity and even humidity. Usually, chemists use those characteristics to separate silver and copper from pure gold. For instance, if you have an alloy of 18K gold. You treat this alloy in nitric acid, the chemical will "eat" up copper and silver in the solution and leave pure gold in a brown powder. Then if you treat the solution with a clean piece of copper, silver will be precipitated out to leave you a solution of copper nitrate. Since alloy has a mixture of other metal which can be oxidized easily, jeweler can use a flame to quickly assess the quality of pure gold. 
Sorry for too lengthy, I just enjoyed doing jewelry when I was young, but no more nowadays.


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## DKRickman (Mar 25, 2008)

There have been some good suggestions on how to solve your problem, but I want to point out something which may help when asking questions in the future. A rail is the long metal piece (typically shaped like an inverted "T") which the wheel runs on. The assembly of two rails and the crossties (whether wood, metal, plastic, or masonry) to connect them is called track. Thus, you are not asking about putting resistance on one rail vs. the other (which sounds to me like it concerns the two rails of a single section of track), but rather on the feeders for one track vs. the other. 

Obviously, people got around the confusion, but it might help to avoid the confusion in the future.


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## Dan Pierce (Jan 2, 2008)

Pete, gold will tarnish in less than a year. 
What keeps contacts clean is the pressure of the connection, or solder to keep the joint from rusting/corroding.


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## mymodeltrain (May 14, 2013)

"There have been some good suggestions on how to solve your problem, but I want to point out something which may help when asking questions in the future. A rail is the long metal piece (typically shaped like an inverted "T") which the wheel runs on. The assembly of two rails and the crossties (whether wood, metal, plastic, or masonry) to connect them is called track. Thus, you are not asking about putting resistance on one rail vs. the other (which sounds to me like it concerns the two rails of a single section of track), but rather on the feeders for one track vs. the other. 

Obviously, people got around the confusion, but it might help to avoid the confusion in the future." 

Thanks for the explanation to distinguish between rail and track. I still need to learn a lot about this hobby, particularly its terminology.


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## mymodeltrain (May 14, 2013)

I want to update the track power issue. Dave Bodnar made me a diode control system and I connected it to the track today. It works perfectly. Now, I have two trains (USA train Virginia dockside versus LGB Stainz) from two tracks running at the same time with nearly equal speed. 
Dave, thanks for great help.


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