sparking/electrical problem with Peco points

Hi all
Here's a baffling little problem for us to chew over. We have had Soberton
out at the TRPS Show in Ferneham Hall yesterday and the fiddle yard was
right at the back of the stage which was dimly lit. This allowed me to see
the full extent of a problem we have known about for a couple of months, but
has obviously been going on for quite a while.
The problem we are seeing is that when trains cross any pointwork (the
throats of the fiddle yard are probably the best example) we are seeing
sparking, almost as if we were looking at electrical units sparking over
gaps in the third rail. The points are all Peco Streamline. The stock
involved seems to be almost anything and everything; Bachmann, Hornby, the
odd re-wheeled Lima, steam and diesel outline.
To begin with people were blaming old style metal tension lock couplers
shorting from live chassis to frog, but in the dim light yesterday I was
able to see the true nature and full extent of the problem (and examine the
damage that is being done). This sparking seems to be happening towards the
tips of the point blades and frankly a couple of the blades I looked at
ought to be changed so this has obviously been going on for a long time. I
am guessing that there is corresponding damage to the wheels as well but so
far I have not been able to find any on my stock.
As far as I am aware the points are all insulfrog and the wiring of the
points is totally "standard" but the evidence seems to suggest that somehow
the point blades are actually at a different potential to the adjoining
stock rails, and that the inner flange face of any slightly out of gauge
wheels are managing to bridge the gap thus causing the sparks to fly (no, I
didn't have a chance to get the meter out and check but I plan to the next
time the layout is out). Also, we are not using any fancy electronics such
as HF track cleaners.
Question: has anyone encountered similar problems and can they point me in
the right direction to find a cause?
Thanks in advance.
Elliott
Reply to
Elliott Cowton
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There is a bonding wire which joins each switch rail to the frog rails, when the switch is open it makes it rail the opposite polarity from the running rail it is next to, the sparks are caused by wheelsets touching the swtich and running rails at the same time (probably bogie stock).
If you can lift the points then simply remove the bonding wire (its underneath and impossible to remove without lifiting), if you can't lift the points then you either have to live with it or cut a new gap with a slitting disc or similar tool.
This then introduces the problem that your switch rails then rely on mechanical contact to work so you can solder some bonding wires from the each switch to its relevant running rail.
hth,
Reply to
Dave Skipsey
"Dave Skipsey" wrote
Thanks Dave, but I have always understood that this only applied to live frog points. We had deliberately chosen insulfrog for use in the yard in order to "keep it simple". Can you confirm/deny?
Elliott
Reply to
Elliott Cowton
In message , Dave Skipsey writes
I'd like to query that.
We are talking insulfrog points aren't we? The points on my layout have a bonding wire connecting the switch rail to the appropriate frog rail, so there are two bonding wires.
This means that if there is no feed at the frog end, and the points are set straight, then the curved switch rail should be at zero volts. If this is not the case, what is being fed at the toe end of the points?
On my garden layout I have bonded the switch rails to the adjoining stock rails without the necessity of cutting any connections already existing.
Reply to
Jane Sullivan
I don't hae a lot of experience of stuff like this, but could the rail that moves (to select the track) be wobbling as the train goes across. Said wobbling could make and break contact with an energised rail and if there are wheels on the blades it would make a circuit.
Unlikely to be anything as complicated as that but you never know!
peter
Reply to
naked_draughtsman
Electrically, the point rails are separate from the through rails and provide switching of the two rails extending from the frog. There are two bonding wires to connect the point rails to the rails beyond the dead frog. The point blades make contact with the through rails to electrify the points and the rails beyond the frog. under the point blades are spring sheet contacts which slide under the through rails to provide positive electrical connection. These are prone to damage during ballasting as watered PVA glue gets in and stops the springiness. Also ballast glue can lodge on the underside of the through rails and isolate the contact. We won't even think about ballast! As the spring strips/contacts are dependant on the tension they have with the underside of each point blade, they can't be retensioned if damaged.
The result of the contacts being damaged is that the current has to pass between rail and point for the entire time that the loco etc is drawing current beyond the frog and sparking does occur because this connection is subject to dirt etc.
Regards, Greg.P.
Elliott Cowt>
Reply to
Greg Procter
Are all your points definitely Insulfrog ??? - I have had this proble with live frog, with dead frog I cannot see how you can get sparks aside from dirt - or someone has bonded the switch rails to the frog (well just beyond) ....
Reply to
Dave Skipsey
Then I'll answer it.
I am trying to find a solution to the OPs problem, I have not attempted to dicuss the merits of the alternatives to wiring a layout. I can only assume that either the problem is not exactly as described or points are actually live frog.
The OP can of course bond the switch to the stock rails as you suggest and get a dead short if the points are live frog and still bonded underneath - might be a useful way of confirming if they are live or dead frog, personally I wouldn't do it.
Rather than (incorrectly) criticising my response why don't you suggest a dead frog reason why the OP has the sparking problem.
Reply to
Dave Skipsey
Hi Elliott,
Taking a step back here, there are only three reasons I can think of as to why you would be observing sparking:
1/ There is a short circuit 2/ There is a broken circuit 3/ You have an HF track 'cleaner' trying to rectify (2)
Applying some basic principals, (2) can be discounted if you haven't got (3) because the current/voltage isn't high enough to cause a spark, which leaves only (1). However, I cannot see how you can get a short circuit like this with a dead-frog turnout, even if you do back-feed it - the rails exhibiting the short would have the same polarity unless they are being supplied from different controllers. Which all leads me on to say.....are you really sure this is a dead frog turnout ? All the symptoms you describe are characteristic of live frog turnouts, not deadfrog. If you need help with wiring live frog turnouts, have a look at
formatting link
- this is the only way to properly wire live frog turnouts.
Hope this helps,
Graham Plowman
Elliott Cowt> Hi all
Reply to
gppsoftware
Any loco sitting beyond the frog is going to draw current when the turnout is aligned to that loco (or lighted train ...)
The spring conact under the point should be carrying the current, not the stockrail to point touching.
I disagree. If the traction current to a loco beyond the frog passes between stock rail and point, there will be (small) sparks.
No problem - feed the rail beyond the frog with the opposite polarity to the stock rail and you get BIG sparks - however, in the description the train keeps running so that isn't it.
Reply to
Greg Procter
In message , Dave Skipsey writes
Maybe you ought to go to the opticians to get your eyes tested. I can tell the difference between live and dead frog points just by looking at the frog.
Because your response was wrong.
Maybe the contact that is fixed underneath the switch blade and connects it to the stock rail has bent out of position, and the only electrical contact is between the touching rails.
Reply to
Jane Sullivan
So can you see the OPs layout from where you are then ? and you can confirm that the points are dead frog ? - I'll take that as a "no" shall I ?
No it wasn't - it was correct if he had mistaken dead/live frog points (as others have questioned) and was far more helpful than your suggestion .... oh you didn't make one.
Go and score points elsewhere - reply to the OP with your solution.
Reply to
Dave Skipsey
In message , Dave Skipsey writes
I refer the honourable gentleman to the original poster's original post:
As far as I am aware the points are all insulfrog and the wiring of the points is totally "standard"
Reply to
Jane Sullivan
In message , Dave Skipsey writes
OK, In that case, and to stop you from further bullying me:
Elliott,
How easy would it be for you to confirm that the points are in fact insulfrog, as suggested in your first post?
The answer to your follow-up question to Dave is that, yes, this only applies to live-frog points. However, you say in your first post that this sparking occurs when trains cross _any_ pointwork, but then you only mention the points in the fiddle yard. Does it happen on points in the main part of the layout? If so, this would seem to suggest that, as Dave implies, the points in the fiddle-yard are actually live frog and not the insulfrog that you thought they were.
If this is the case, I can give you a suggestion for how to get rid of the phenomenon: paint the back of the switch blades with some insulating paint to prevent them from shorting on any passing wheels. This should not affect the way the points switch current to the frog if you ensure that the paint does not get on the spring contacts that contact the underside of the running rails to do the current-switching.
There is a way this could happen with insulfrog points, but it is most unlikely. If, at the frog, a wheel were to bridge both frog rails, while at the same time a wheel were to bridge the gap between the switch blade and the stock rail, you would get a short. In my experience the only wheels that bridge both frog rails are original Lima, but you say that you are getting the sparking with all sorts of wheels, so as I say this is most unlikely.
Reply to
Jane Sullivan
Greg,
turnout is aligned to that loco (or lighted train ...)
Yes, but the voltage and current is not sufficient to cause sparking in general use. There must either be a short or a broken circuit. I merely pointed out that an HF track 'cleaner' highlights this problem.
stockrail to point touching.
This is wrong. Both can and do carry the current in a Peco turnout.
between stock rail and point, there will be (small) sparks.
I'm not sure what you are describing here, but I would contend that if there is any sparking at all, then there is some kind of electrical problem such as a short or a broken circuit or perhaps: dirty wheels and rails.
the stock rail and you get BIG sparks - however, in the description the
train keeps running so that isn't it.
This sounds like a live frog to me, not a dead frog.
I fear that like Jane, my suggestions are being 'bullied'.
I have built several very large layouts over the years and have hand-built track on a number of occasions as well as used both live and dead frogs, so I can assure you that I have plenty of experience of how turnouts are constructed and wired, including Peco turnouts!
Peco turnouts are made in such a way that there are only a limited number of things that can cause shorts or sparking. Dead frogs are pretty much fool-proof unless steam roller wheels are being used which bridge the frog and the other track is being back fed with opposite polarity. As I pointed out, there is only one way to wire live frog turnouts:
formatting link
and providing this method is used, live frogs will not cause a problem.
Based, on the information provided by Elliot, the symptoms he describes suggest that the turnout may not be a dead frog. Like Jane, I can also identify a live frog turnout just by looking at the crossing V (frog). Elliot: Is there any possibility you could post a picture of the crossing V ?
In the mean time, may I suggest to Elliot that he fits insulated joints to the crossing V as indicated in
formatting link
and ensure that the turnout is only fed from the toe (switch blade) end.
Graham Plowman
Reply to
gppsoftware
Just when I thought you had said something useful you demean yourself with such a comment - disagreeing with you is not bullying.
Reply to
David Skipsey
Certainly an HF track/wheel dirtier could cause the problem.
The original poster said the sparking was evident in darkness/low light - a short circuit should cause the overload cut-out to trip = no sparking ;-)
stockrail to point touching.
No, I'm right, otherwise why would Peco bother to put the spring contact there, and why do Peco turnouts misbehave electrically when the contact is damaged.
We're basically agreeing! If the rail beyond the frog gets its current from the stock-rail/point connection and there is a load (loco, lighted coach ...) on that track, as there is when a train passes through and beyond said turnout, then the point blade/stock rail contact is passing that current. Given poor contact, there will be sparking. (or no go)
Not from me, I hope.
What you are suggesting would overload the cut-out whenever the turnout was aligned. Elliot was describing the sparking when trains were passing which is either a wheel intermittently connecting + to - or poor connection of the traction current to one of the relevant rails. As the train keeps going and the overload doesn't cut out it is _not_ a direct short circuit.
I disagree here. Doing so would eliminate the self-switching function of the Peco turnout to the following tracks and still leave the poor traction current connection within the turnout.
Reply to
Greg Procter
If the turnouts in question were live frog wrongly wired then there would be a dead short 'CRACK' each time the turnout was thrown and the overload cut-out would cut out - 'BANG'. That's not the symptom described.
Regards, Greg.P.
Reply to
Greg Procter
Greg,
No! It doesn't cause the problem. It is a tool which simply highlights the presence of an already existing problem!
- a short circuit should cause the overload cut-out to trip = no sparking ;-)
Well since I don't recall DCC being mentioned, then I assume DC is involved, in which case, the cut out trip is quite slow and it is possible that a momentary short is not enough to cause the cut out to drop. This is one of the problems people blame DCC for because it has a cut out system far in advance of any DC system and threfore, it drops out due to momentary shorts caused by poor wiring. You can't get away with this dodgy wiring in DCC.
stockrail to point touching.
there, and why do Peco turnouts misbehave electrically when the contact
is damaged.
No Greg, I am sorry, but you are wrong. Not all Peco turnouts (eg code 75, 009) have the spring contact (I am assuming you mean the little tabs on the switch blades which tuck under the stock rails and make contact) and they certainly don't always misbehave without them. So how do they work ? They work in exactly the same way as the code 100 turnouts do if you remove the tabs. The tabs are an insurance policy, not an absolute requirement. The turnouts will work without them, but I will conceed that their absense can make Peco turnouts unreliable when dirt gets on the sides of the stock rails. With live frogs, we simply bond the switch rails to the stock rails and therefore, never have this problem.
was aligned. Elliot was describing the sparking when trains were passing which is either a wheel intermittently connecting + to - or poor connection of the traction current to one of the relevant rails. As the train keeps going and the overload doesn't cut out it is _not_ a
direct short circuit.
See above. DC controllers will tollerate momentary shorts.
the Peco turnout to the following tracks and still leave the poor traction current connection within the turnout.
We are speculating about a turnout which we haven't seen and we don't know what the wiring is around it. All sparking is caused by either a short or a broken circuit. In the case of a dead-frog turnout, the number of ways a short can occur are very limited, however, if the problem is a short, evidently the turnout is being back fed with an opposing current, probably bridged by wheels on the frog - a case for checking wheel standards and back-to-backs. If you are relying on switch blades to do your switching for you then you are asking for trouble in the future. All switching should be done by point motor switches/relays for turnouts themselves and isolating switches for the lines they service - anything but switch blades. And since there appears to be a short situation, the only way to stop it is to fit insulated joints and look at/rearrange the feeds involved. Since neither of us is fully cogniscent with Elliot's situation, until we see a close-up photo of the frog and get an idea of the electrical feeds involved, there is little point in us arguing about it.
Graham Plowman
Reply to
gppsoftware

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