We talk about devices such as in-line fuses, TVS, etc. to help protect equipment. But I am still surprised at the damage to rails, wheels, and car bodies the voltages and amp loads we use can do in a very short time.
When I first started running 3 rail O gauge I had some derailments that caused pitting to the wheels and the track. I also burned a smoke unit on one derailment when in a panic I accidently threw the throttle the wrong way. As I learned more about 3 rail operation I added 7 amp in-line fuses between the center rail and transformer, phased transformers, etc. Even with a 7 amp in-line fuse, a dirty joint was able to create pitting on the pickup rollers on one of my engines before the 7 amp fuse blew.
Can one eliminate the pitting of wheels, rails, and rollers by using protective devices, and if so how?
Birds… I’m about ready to try a product, Performix’s Plasti Dip (A multi-purpose rubber coating) and coat those specific small areas, <1/2" in length where I am seeing pitting at switches. I purchased it at HD. The Chief has been placing electrical tape in specific locations with success.
I know of Plasti Dip (keep it off of your hair). That may be a good solution for spots on a couple engines I have.
The other night I had a bad derailing of a 13 year old Lionel Alco A-A at a switch. It is a light engine and it went sideways across the track. All the power got shut down very quickly, but I was still surprised to see that a center rail on the switch had a couple rough spots (buffed out fine), and one of the side wheels had a couple small pits.
It seems that no matter how fast a circuit is broken there is still time for this to happen when that initial short takes place. So this started me wondering if there really is a way to prevent it, or if it is just a part of running trains.
Birds, I am no expert on this, but have some thoughts. Anywhere that you have arching will cause pitting. Doesn’t even have to be a short/derailment. From the information I have read over the years, good maintanence is the best thing to do. Keep rollers clean and make sure you have good solder joints to the pickup rollers and everywhere on the layout. Also make sure you have good springs on the pick ups. Check your equipment on a regular schedule for any signs of pitting, or other deterioration. even with the best care, I am sure pitting can still occur.
I agree, maintenance is the biggest way to slow down pitting on wheels and rails.
Even light dust on the rails will cause arcing, and as we know, arcing causes pitting. The other culpret is ANY oil or lubricant on the wheels, rollers or track.
I wipe down all my track with track cleaner before any running. Also regularly check that lubricant has not found its way from axles to wheel surfaces.
Clean up any pitting when you find it. Pitting causes even more pitting due to the poor conductivity and increased arcing.
Even with all that, I get pitting on the control rails of switches using the non-derailing function. Many of my switches are tied to others to auto-route the train around the layout, so in some cases that control rail is handling the switching of three switch motors and arcing occurs. Sintered metal (wheels) and tin plated steel (rails) are not the best material for switching contacts…
When I have suggested that the short circuit that occurs as a train runs between separately powered blocks might cause pitting of the pickups or rails, I am usually assured by someone that he and everyone he knows have been doing this all their lives and never experienced any arcing or pitting whatsoever.
Keep the track/wheels/rollers clean. Don’t force track so it aligns properly. Keeping track level and properly installed will help to minimize roller bounce. Use hard plated rollers if possible. Only use the current you need to run the trains.
Thanks for the replies, and I agree about track maintenance.
Pitting during normal running is not a problem now because of both track maintenance and how the layout is wired. It is pits caused during a derailment that I’m wondering if it’s possible to completely eliminate.
I’ve had a couple bad derailments where even with fuse protection there is an initial spark as the wheels (not the rollers) on engines and/or cars make contact with the center rail, and then the fuses blow. This brief contact has been enough to cause some pits.
Fuses and breakers are a benefit, but they are still reacting to something causing a short. They minimize the length of time of the short, but they don’t absorb the energy released (don’t know any other word to use) during a short.
It’s that brief initial contact of the short that seems to cause some damage.
As an extreme example, (in our youth) a friend of mine briefly touched two stripped wires to a metal pen resting on a porcelain sink. The breaker to the outlet tripped, but the initial contact was enough to melt some aluminum on the pen and permanently fuse it to the sink (partially electroplated sink).
“Dr, my arm hurts whenever I do this? What should I do?”
“Stop doing this for starters”
If you eliminate derailments than this isn’t an issue. If you want to stop the wheels from pitting switch to plastic wheels and/or plastic truck frames/side castings.
The real problem is the current being used in this environement is pretty heavy even though the votage is low. A TPC-400 with multiple bricks is throwing up to 20 amps on a section of track. The breaker doesn’t trip and the fuse doesn’t blow until something goes wrong. You can increase the sensitivity of the breakers or go to fast blow fuses but you may wind up running through the fuses or having to reset breakers on false triggers. If you run strictly modern equipment with modern supplies this may not be as much of an issue. I don’t know if anyone makes GFI style breakers for toy train use.
Unfortunately plastic wheels aren’t an option on an engine… [;)]
I have a 6 amp auto resetting breaker in-line with the HOT wire from the transformer. Just to see what would happen to some track, I attached a 20 volt bidirectional TVS to a lock-on (20 V operating, 22.2 V breakdown, 32.4 V clamping, 15.4 A surge), and then attached that to a section of track. Then I applied 12 volts to the rails of that track section, and then shorted across the middle and outside rail with an old piece of metal.
There was a spark before the breaker tripped, and that spark was enough to pit the rail.
I doubt the TVS provided much (if any) protection in this situation because it’s ratings are higher than the breaker’s.
So maybe one approach is to use a more conservatively rated TVS. One where the amp surge equals the rating of the breaker/fuse, and the operating voltage equals the maximum voltage used for running trains on that layout. I am thinking that such an approach would set both a voltage and amp limits to what currents could exist across the tracks.
This might seem like a silly exercise to some; but even with the most careful train operation there are times where our trains do collide, and there are times they unexpectedly derail. In these situations damage can occur even with conservatively rated fuses and breakers.
Have you tried using 10 amp fast blow circuit breakers instead of fuses? Even 7 amp fuses take a fraction of a second to burn out the fusible link, circuit breakers work just a little faster. I use 10 amp circuit breakers from Scott’s Odds and Ends with a post war 275 watt ZW.
As far as pitting from a derailment, I have had it happen once when an engine dragged a quad hopper that derailed the back set of wheels and it really sparked going around for a few feet.
Byrds; a TVS unit is not there to do the job of a fuse or circuit breaker, it works more like the voltage surge protection in an outlet strip for your electronic devices. A TVS is supposed to clip the higher voltage(keep from going over a set voltage) not interupt voltage or current flow.
I’ve always thought that fast blow fuses were faster than breakers. I’ve always been of the impression that one uses fuses when you need speed, and breakers when you want convenience.
I am using Bussman CBU-6, 6 amp, Type 1 (auto resetting) automotive fuses listed under their Consumer/Aftermarket, “heavy duty” fuses and breakers, section. Unfortunately they don’t provide specs for their breakers in terms of speeds, etc.
The “fast blow” fuses that Scotts Odds and Ends advertises are Bussman Type III panel mounts listed under the same section, and they also don’t have a speed listed.
I do realize that a TVS is not there do the job of a fuse or breaker, and that it is there to clamp surges.
I brought up the TVS because I was pondering if a short caused by derailing might also have a spike in either voltage associated with it. A fuse/breaker doesn’t protect from voltage. So if a derailment has a spike in voltage associated with it, then I was thinking that a properly rated TVS used in conjuction with a fuse/breaker might be a way to add an additional layer of protection at the rails.
I’m no electronic expert by any means, but in my opinion there is to way to stop the sparks-arcing in a derailment other then not derailing. It takes “X” amount of amps to operate our trains. In a derailment and metal crosses the rails it completes a circuit just as a switch does. It is going to arc because it is drawing all the amps the power source is putting out until the breaker or fuse trips. Even touching two leads from a 1.5 light bulb to the ends of a D cell battery will spark. We’ve been living with sparks ever since I can remember. Every time there is a spark or arcing it is like an arc welder. When the train sparks while running it’s only drawing the amps required by the motor which doesn’t reach near the breaker or fuse rateing. However, in a drailment this short is trying to use the full amps of the power source, but the breaker or fuse will trip or blow before damage to that power source is damaged. Hope I’ve made sense here
As for TVSs, they should be rated to withstand the maximum track voltage, with appropriate allowance for the tolerances of the TVS and the transformer. However, don’t forget that the instantaneous maximum voltage is not the RMS voltage that we normally talk about, but rather that voltage multiplied by the square-root of two, or about 1.41. Also keep in mind that a whistle controller adds 5 or 6 volts to the RMS voltage. So, for example, a ZW putting out 21 volts RMS with the whistle blowing has a peak around 36 volts.