Stuttering while going over points - Spark

[lardenr]

Hi, I have uploaded a video of the issue that I'm having with my locos going over one particular point.

If you look carefully you will see it does spark in a couple of places near the frog. This is on an inner track, the outer track is fine.

Not sure if I need to replace the point, or if the gap perhaps between the rail is too much or what. If anyone has got any advice, I will be grateful. I have been over it also with a Voltmeter and the Restastance/Continuity test, and that appears ok.

https://youtu.be/1XODGhqKWFc

Thanks in Advance!

Richard

[Walkingthedog]

Are the points perfectly flat? They do tend to bow.

[RFS]

The spark is indicating a momentary short circuit. It is likely caused by the wheels touching both rails as they pass through the frog. Check the back-to-back measurements of the wheels as this is the likely where the problem lies.

[lardenr]

Tracks appear to be flat ok, will double check. I have a small Spirit level.

Will also check the wheel spacing as well thanks.

Thanks for the replies

[Walkingthedog]

A track pin near the centre of the points will get rid of any bow. A steel rule on edge is good to check flatness.

[RFS]

Had another close look at your video. You can see that when the stutter occurs there is an axle precisely on the frog. The momentum of the loco carries it past the spot so the DCC command station does not trip.

I would try running the loco through the point very slowly which should result in a DCC short stopping the loco. You will then be able to see exactly where the problem occurs.

Some DCC systems are very sensitive to shorts and you are perhaps lucky that yours is not tripping when the momwentary short occurs.

[lardenr]

Thanks again both.

I think I have got a pin in the track there, but will certainly check that out.

And will check by running it slow over the frog as well. If I do find that it's touch 2 parts of the track, is there a way you would recommend that a little bit of track could be insulated? A touch of glue perhaps?

Will get up there at the weekend to have a look.

Richard

[jed10]

Ok, so you are immediately in a challenging situation because that's an Insulfrog point which is never ideal on dcc. Also I can't see signs of any droppers soldered directly to the stock rails or frog rails. Are you relying upon fishplates for electrical continuity? Are you relying upon the switch rail physical contact for electrical continuity? If the answer to those questions is yes then that's your problem I'm afraid.

If you look at the top left frog rail there is quite a big gap in the fishplate join so you may not be getting a back power feed from this. If the switch rail isn't making a good connection then this could be where the problem is. If there is no power, or maybe reduced power / corrupt dcc signal due to high impedance from the start of the frog rail to the end of the frog then that would explain the behaviour.

As to what you can do to fix it, that depends on how far you want to go and where your power feeds are. The best solution is to replace the point with an Electrofrog point including appropriate droppers, wiring modifications as necessary, insulated rail joiners on the V and switchable frog power. If you want to try an Elastoplast option then, assuming you have droppers feeding power into the track beyond the point, you could try soldering the fishplate across that frog joint directly to the the rail. You'll need quite a hot iron to do that successfully.

Good luck.

[RFS]

Nothing wrong with Insulfrogs with DCC. The problem is being caused because a metal wheel is touching both frog rails, or both closure rails, as it passes through. Simple solution here would be to put insulated rail joiners on the two frog rails, and make sure there is a DCC feed downstream of the frog. This will prevent both rails of the frog, and the closure rails, being live with opposite ploarity at the same time.

[Brian]

RFS is correct on both counts! A pair of IRJs and new rail feeds will solve the problem if the wheel B2B are correct = 14.45mm +/-0.5mm
This shows the problem on Insulated frog points and a fix, if B2B is correct. https://www.brian-lambert.co.uk/DCC-Pag ... l#problems