A non model railroader person asked a question that I could not answer to his satisfaction.
His question :
“Wouldn’t metal wheels cause electricity to flow thru intentionally placed Gaps in the rails, or otherwise cause more short circuits ?”
It’s not really a problem because you normally switch the block the train is going into to the same power pack the train is currently running on. Even if you didn’t, this would normally not cause a short, but might cause a train to surge if picking up power from two packs at the same time (you would need to have all wheel pick up for this) or lose power if the pick ups are split because the front wheels pick up from one side and the rear wheels form the other. In dcc the layout is usally all wired as a big block (although you may have power district on large layouts).
Reversing sections could be a problem, but if wired properly and the power is switched properly it won’t be because as the train passes from one block to the next the two blocks will be in the same polarity and connected to the same pack. For dcc you can automatically handle reversing sections.
Turnouts can be a cause of shorts depending on how they are made. It is possible with some turnouts and some wheelsets for wheels to make contact with two rails of opposite charge. This is a bigger issue with dcc because of its need to react quickly to shorts - see this site http://www.wiringfordcc.com/ for more details and what to do about it. For dc the shorts are momentary and not a problem.
Enjoy
Paul
namron,
Metal wheels can cause shorts if they are out of gauge and contact rails of opposite polarity in turnouts (point rails, especially). Note the trend to “DCC Friendly” turnouts, where the rails nearest each other are all the same polarity.
Metal wheels add weight, lower the center of gravity, and help keep the track clean (they don’t generate static charge like plastic wheels do). Benefits outweigh the problems when they are installed correctly.
Mark C.
We’ve only encountered one situation on our HO-scale club’s 20x40 foot layout, where practically everything has metal wheels, with a short being caused by a wheelset.
In the one instance mentioned, one end of an axle dropped out of a metal sideframe on a Kadee truck and shorted. This caused the wheelset to get so hot that the insulation around one of the wheels melted and shorted out the track, thereby causing the DCC system to shut down.
When the car was removed from the track, the truck and wheels were so hot you couldn’t touch them.
That one Kadee truck is the only one we have ever had a problem with.