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Possible/probable shorting Peco insulfrog diamond crossing.


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I never even knew about it until I fitted a DCC Specialists PSX-AR (circuit breaker). I'd read about issues with crossings but until now I'd shrugged them off. Even now it seems that only one crossing is occasionally a problem. Unfortunately sod's law strikes and it's the crossing in a tunnel. It's accessible for cleaning and rerailing (I'm not that stupid, lol) but removing or working on the crossing is out of the question.

 

So my question is - if locomotives will cross the diamond quite happily in the absence of a faster, more sensitive circuit breaker than my Powercab is it something I can just ignore? The layout is going to be torn down in a year or so anyway to make way for a house move and a second longer term layout.

Edited by AndrueC
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  • AndrueC changed the title to Possible/probable shorting Peco insulfrog diamond crossing.
2 hours ago, AndrueC said:

I never even knew about it until I fitted a DCC Concepts PSX-AR (circuit breaker). I'd read about issues with crossings but until now I'd shrugged them off. Even now it seems that only one crossing is occasionally a problem.

I wired my Peco Code-100 double-slips (& single slips) as if they were electrofrog, cutting the factory fitted wires as necessary and using a microswitch on the servo to provide correct polarity to the frog. I realise that's not an option to you now, but something to bear in mind for the future.

 

Secondly, when I retro-fitted MERG kit#57 short circuit detection (SCD) modules, I found that they were intermittently detecting shorts as some of my locos passed through electrofrog turnouts (I have a lot of old Lima & Hornby locos with wide and/or 'pizza cutter' wheels). This I obviated by setting the SCD to a slightly 'slower' detection time, a feature built into the board. I set it to 6ms, and the problem went away. If the PSX-AR has such a feature, that may be a viable solution.

 

Ian

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  • RMweb Gold

If you have the latest version of the PSX-AR (which is made by DCC Specialities not DCC Concepts) then you have the option of increasing the trip time via CVs, but you need to ensure this doesn't allow the Powercab to trip instead.

 

I did have endless problems with a couple of Insulfrog crossings caused by transient shorts as wheels bridge the tiny plastic inserts, and in the end replaced them with Electrofrog ones. 

 

Like ISW I have also had a problem with a couple of locos causing shorts on Electrofrog slips, these being early China-made locos with the 14.2mm back-to-back wheels. Fixing these to 14.5mm width cured the problems. 

 

 

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Posted (edited)
12 hours ago, HLT 0109 said:

Since you're looking for a short-term solution, why not just remove the DCC Concepts circuit breaker and keep it for the new projext?

 

Harold.

Yup, done that. Was just wondering if that meant I was ignoring something serious.

 

I'll have a look at adjusting the CVs. Given that the shorts have no noticeable affect it seems possible that will work.

 

Thank you all very much.

Edited by AndrueC
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12 hours ago, RFS said:

If you have the latest version of the PSX-AR (which is made by DCC Specialities not DCC Concepts) then you have the option of increasing the trip time via CVs, but you need to ensure this doesn't allow the Powercab to trip instead.

I too have the NCE PowerCab, and with my MERG kit#57 SCDs set at 6ms they are still more sensitive (quicker reacting) than the PowerCab.

 

Ian

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If i understand correctly, the short happens when the wheel bridges the insulfrog

The drawing shows the coarse of the wheel & where the short can occur

A fix is to paint the area of the insulfrog (highlighted) with fingernail varnish (I use clear nail varnish)

This fix can last for years depending on the use & is easy to reapply

One disadvantage is short wheelbase locos could stall due to the length of the dead section at the frog being lengthened 

 

931381747_insulfrogshorting.png.e165943d77676380ea2985aa851d7c4f.png

John

 

 

 

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Posted (edited)

To solve this particular issue I isolate the frog of the diamond and switch them using a relay. Also the back to back can cause the same type of short

Edited by Andymsa
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Thanks for the replies. Last weekend I discovered that the problem was worse than I thought (no idea why it's changed) but it became so bad that locos were stuttering and my NCE was buzzing. I put some liquid skin on the centre section of the diamond and all is fine now. I've even put the PSX-AR back in circuit.

 

Unfortunately the diamond is in a tunnel with track on top (Sod's law, the other diamond which is in the open is of course just fine) so whilst I can reach it for cleaning my options for serious adjustment are limited.

 

This layout probably only has a couple of years left before I move house (don't worry - another layout will follow) so for now I'll just keep painting the problem away.

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Posted (edited)
On 25/04/2021 at 20:39, ISW said:

I wired my Peco Code-100 double-slips (& single slips) as if they were electrofrog, cutting the factory fitted wires as necessary and using a microswitch on the servo to provide correct polarity to the frog. I realise that's not an option to you now, but something to bear in mind for the future.

 

Secondly, when I retro-fitted MERG kit#57 short circuit detection (SCD) modules, I found that they were intermittently detecting shorts as some of my locos passed through electrofrog turnouts (I have a lot of old Lima & Hornby locos with wide and/or 'pizza cutter' wheels). This I obviated by setting the SCD to a slightly 'slower' detection time, a feature built into the board. I set it to 6ms, and the problem went away. If the PSX-AR has such a feature, that may be a viable solution.

 

Ian

 

Ian.

Thanks for mentioning this.

I had forgotten the 'delay' available with the MERG units.

I had a problem with the wide tires fitted to Hornby Class 31s.

Now set to 6ms delay and that beats the Power Cab, so all good.

 

Thanks again.

 

Dave

Edited by dasatcopthorne
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4 hours ago, dasatcopthorne said:

I had a problem with the wide tires fitted to Hornby Class 31s.

Now set to 6ms delay and that beats the Power Cab, so all good.

Dave,

 

I can't remember which of my old Lima / Hornby locos that caused my shoring problem. I have so many with 'wide' wheels ...:resent: I was pleasantly surprised that the MERG, when set to 6ms, was still quicker reacting than the PowerCab. It's really nice to have trains continue operation on non-affected power districts when a short does occur elsewhere, which was always my 'plan'.

 

Ian

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Posted (edited)

This is more of ponder that a request for help. I do like a technical puzzle so I'm trying to work out what/how might be shorting on that crossing. The crossing is used to form a figure of eight so the phase will be this:

Crossing.png.e9b7e35afb8e53fe9a3862ade10bb586.png

That explains why it's the centre that I had to paint at any rate. The short occurs (only with some locos - both my Class 68s, not my Class 43) when traversing right to left.

 

I can't easily get a photo of the central frog but this is the frog from my other crossing for reference:

 

20210511_154037.jpg.d80d3b3e09477f4cc3ac3b1d091decc3.jpg

 

I can't see what could cause a short about that centre frog. I mean, sure, the frogs at either end (not visible above) have a very small gap between the rails like turnouts but the line drawing shows that they are the same phase anyway so nothing to short out. FYI the central metal guide rails do not have power, I assume they are only metal because it would look better than having an entirely plastic centre frog.

 

The frog that doesn't have problems has different phases so if it were to short it'd be at the ends, not the centre.

 

As I wrote earlier it's just curiosity really but I'm a software developer and have long since learnt that getting to the bottom of something can sometimes reveal a simple solution. Right now painting the centre frog seems like all I can do due to location:

20210511_155804.jpg.b543b5ba10f1652c8a741b5a5131a6e4.jpg

Edited by AndrueC
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I Have had a similar problem with a long crossing  & I fixed it by painting the rails with clear nail varnish

The rails will need to be painted in four places, 2 are shown in the drawing

 

I would think that the shape of the wheel will determine how bad the problem will be

A conical section wheel should be less prone to shorts as only the flange side of the tread touches the  (red) rail, the outside of  the tread will ride above  the black rail & there is no short

a cylindrical section wheel is more likely to touch both red & black rails & short

You may think that as the wheel goes from the red rail onto the plastic section it only shorts to the black rail while it either on the plastic rail or in the crossing gap, but in a loco that wheel is connected to all the other wheels on that side by pickups

Hope this all makes sense & is helpful

 

998389556_pecoshorts.png.990d58b61f915fff25a718b96b948708.png

7 hours ago, AndrueC said:

FYI the central metal guide rails do not have power, I assume they are only metal because it would look better than having an entirely plastic centre frog

I think those rails are there for strength & rigidity 

If they were plastic it would be easy to snap the crossing in half

& if the plastic deformed for any reason then the crossing could go banana shape

John

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19 hours ago, AndrueC said:

As I wrote earlier it's just curiosity really but I'm a software developer and have long since learnt that getting to the bottom of something can sometimes reveal a simple solution.

John,

 

Looking at your photo, it seems to me that a wheel is 'bridging' at one (or both) of the obtuse crossings. Rather than try to describe / explain I've marked up your photo with some 'wheels':

diamond.jpg.8d9a07f0cf6afda4993efc8b50995279.jpg

 

Yes, I have exaggerated the width of the wheels somewhat (more like Lima pizza cutters, or which I have plenty), but you should get the idea. Depending how serious the 'overlap' is, you might be able to get away with a very thin shim of plastic on the inside of the metal wing rails (to reduce the lateral 'slop' in the arrangement). If that works, it would be a more permanent solution than painting / insulating the top of the offending rails.

 

Ian

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36 minutes ago, ISW said:

John,

 

Looking at your photo, it seems to me that a wheel is 'bridging' at one (or both) of the obtuse crossings. Rather than try to describe / explain I've marked up your photo with some 'wheels':

Ah, that makes sense, I couldn't figure out how until you drew that picture. Interesting that the Class 68s are the only ones apparently suffering. They are very new Dapol locos (using their new non-removable bogie arrangement) so I wonder if they have an issue with the wheels?

 

That does give me something to think about (I've already thought about never burying track in a tunnel where the roof can't be removed again :) ).

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Posted (edited)

I wonder if it is due to the new design? The bogies on Dapol's older models clip into the chassis with sufficient force to engage the bogie cogs with a worm drive and (mostly, lol) keep two vertical bogie pickups pressing into two horizontal chassis pickups. The class 68s use a cardan shaft for each bogie and the only thing stopping the bogie falling off is that shaft. The bogies droop quite alarmingly when the loco is lifted off the track. This could mean that the bogies tilt more when one of their wheels is inside the rail gap where the two opposing rails 'meet'.

Edited by AndrueC
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Posted (edited)

I think I've found it and you were almost right :)

 

20210512_153339.jpg.a559b130ec8a0714b57d035aee09accf.jpg

 

It's not that one wheel is shorting across two tracks, I think it's two wheels on the same side of the bogie. There's a closer view of that front bogie here:

wheel.png.a56e0c8624b05d991e76d52eea6fe295.png

If Peco had cut the end of that rail on the right at an angle to match the rails the loco is currently sat on the problem might not be occurring. I can't get a clear enough view to confirm that there is contact but that image looks like there is. If the wheels had the 'correct' conical shape it shouldn't be a problem. I thought all modern models followed the NMRA guidelines?

Edited by AndrueC
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3 hours ago, AndrueC said:

I think I've found it and you were almost right :)

 

Looks like you have a couple of solutions open to you. The 'shim' idea on the inside of the obtuse crossing wing rail, and to simply 'file off' a fraction of a millimetre from the head of the obtuse crossing vee rail to 'lower it' below the Class 68 wheel. The latter should be possible even with your restricted tunnel access. The only problem with the latter is that it's probably permanent, so don't take off too much.

 

Ian

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1 hour ago, ISW said:

Looks like you have a couple of solutions open to you. The 'shim' idea on the inside of the obtuse crossing wing rail, and to simply 'file off' a fraction of a millimetre from the head of the obtuse crossing vee rail to 'lower it' below the Class 68 wheel. The latter should be possible even with your restricted tunnel access. The only problem with the latter is that it's probably permanent, so don't take off too much.

 

Ian

 

I think that filing a bit off would be best.

 

I've been doing some research on wheels and track standards since getting to the bottom of this and it all seems like a sad state of affairs (particularly in the UK it seems). It would appear that UK suppliers are no better at adhering to standards than us software developers.

 

Oh well, now that I'm more aware of it it's just another thing to be careful of. Another reason to take more care when laying track and ensure I always have good access.

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52 minutes ago, AndrueC said:

Another reason to take more care when laying track and ensure I always have good access.

Most definitely. That's why I built my layout with baseboard sections bolted together, so that I can lift them out to gain access to the lower levels of the layout. A recent example occurred in the following posting:

That 'repair' would have been next to impossible without the lift-out baseboards.

 

Ian

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On 13/05/2021 at 04:57, AndrueC said:

 

. It would appear that UK suppliers are no better at adhering to standards than us software developers.

 

 

 

I could ask  "what UK standards?" :scratchhead:

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  • 2 weeks later...
  • RMweb Gold

The option I use is to completely isolate any diamond crossing be it long or short from any adjoining track. As I use Peco streamline crossings then to control the feeds, I use the Peco DPDT switch that connects straight to the point motor that controls the route through the diamond crossing. I wire it so that when the point is set through the diamond [reversed] only that route has power, when the point is reset [normal] the other route through the diamond has power. This ensures no shorts even when shunting at crawling pace.

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