Voltage drop problem in one block.

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#1
I have a problem: My layout is divided into blocks for either DC or DCC operation. There is one block, with a curve leading into a 3-1/2 percent grade. Because of the long grade, I haven't paid much attention to any slowing on the straightaway grade. But on the curve leading into the grade, I see notable slowing as the train enters the curve. I have checked rail joiners and have soldered a few. Yet, when I finally started checking voltages, I find there is a 0.2 DC drop at 6 v. between adjacent blocks! Can't quite figure it, but am going to do voltage check from the control panel to the block. I think the next thing would be to compare voltages on DCC. As the wires are the same for both power sources to the block, if I see a comparable drop exists. If so, then I may need to add heavier gage wire from the control panel to the track. The wire run is about 8 feet, but I don't seem to have the problem with other blocks that are further away. Any comments, suggestions? The meter is a standard analog type.
 

Iron Horseman

Well-Known Member
#2
Any comments, suggestions?
Several I hope I can write them up. I cannot imagine an 8 foot wire itself would be a problem. It could be a bad connection be it a solder joint somewhere: track attachment, at a terminal, or at an electrical switch, a screw that tightened to tight and cut some of the strands of a stranded wire. Then I would check the block selection switch itself, it could have a bad internal contact. As perhaps the solder has become the conductor rather than just holding the conductors together.

How did you check the voltage drop between the blocks? Are you comparing one side of the gaps/insulated joiners to the other side? If so did you also check across the gaps? That is inside rail from the one block to outside rail of the other block and vice versa. That might identify the single wire that has the problem.
 
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#3
I measured the voltage across the two rails of one block, which showed 6.0 v DC, and then measured the voltage across the block in question, which showed 5.8 v DC. It is this block that has engines slowing when they enter the block. I have checked and soldered rail joiners, and checked voltages on both sides of rail joiners within the block in question, but haven't found the problem yet. Will start checking voltages inside the control panel. I may run temporary wires from the panel connections to the track, using larger gage wire to see what happens.
Thanks for the suggestions.
Merry Christmas and Happy New Year!
 

Selector

Well-Known Member
#4
On a 3.5% grade, a typical HO layout curve between 18-30" is going to impart a serious impediment to a locomotive hauling more than six passenger cars of proper weight and state of rolling repair, and maybe 12-15 freight cars. In any case, a meter reading should let you know very shortly how robust the voltage is to the block in question. Also, even if the voltage appears to be robust, pushing down on the probes with about one pound of force may reveal a weak solder or a poor connection with a joiner. Try this in several places along the block. You may be surprised.
 

Iron Horseman

Well-Known Member
#5
I measured the voltage across the two rails of one block, which showed 6.0 v DC, and then measured the voltage across the block in question, which showed 5.8 v DC.
I assume this is an unloaded voltage, right? No train running when the measurement it taken?

meterreadings.jpg


Is it possible this (below) could cause a 0.2 voltage drop? I doubt it, I would guess off the top of my head more like 0.02, but could be a contributing factor. One solution to this would be to use sliver solder which is a better conductor than copper.
solderjoints.jpg
 
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#6
I measured the voltage across the two rails of one block, which showed 6.0 v DC, and then measured the voltage across the block in question, which showed 5.8 v DC. It is this block that has engines slowing when they enter the block. I have checked and soldered rail joiners, and checked voltages on both sides of rail joiners within the block in question, but haven't found the problem yet. Will start checking voltages inside the control panel. I may run temporary wires from the panel connections to the track, using larger gage wire to see what happens.
Thanks for the suggestions.
Merry Christmas and Happy New Year!
Started checking all the rail joiners between the feed wires and the area where the voltage drop was noticed. Turns out a couple of joiners were loose or oxidized. Soldered the connections. Took care of the problem! Ya just never know!
 



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