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Offline trainbuff  
#1 Posted : 10 April 2022 00:32:52(UTC)
trainbuff


Joined: 26/11/2006(UTC)
Posts: 507
Location: Atlanta, Georgia
Hi,

I had an intermittent contact track problem and this is how I think I will fix it and retrofit existing contact tracks as needed. I'm happy for any replies of suggestions or improvements.

offending track connection.jpg
In the above picture the unmodified c-track isolated contact rail is intermittently touching the next track and making contact. I searched the internet for this problem and only found it mentioned on this YouTube video by Model Train Fun starting at 37:21 minutes (https://www.youtube.com/watch?v=2FMWxEPm__Y ). Model Train Fun suggested trying different track sections. I will do that moving forward, however for track already soldered to wires, I don't want to switch out different track sections. My c-track is not screwed down to the layout, but is sitting on top of a sound deadening carpet underlay (Ikea Stopp Filt), which allows a little bit of movement. I wonder if there would be intermittent contact if the track were firmly attached to the layout?

sliding insulation under rail.jpg
What ended up working was gluing a piece of paper between the track ends. In the picture above I'm about to slide a paper under the rail.

glued dried and paper trimmed.jpg
Here is after the glue dried and paper is trimmed back.

As an improvements I want to 1) find material other than paper that will hold up to isopropyl alcohol used to clean the track and 2) trim a better track profile into the insulator.

As an example of the variability in the gap between rails here is another unmodified joint with a generous gap.
non-offending track connection.jpg

I guess what caught me off guard was assuming that all c-track joints always have a gap between the rails, so I wasn't looking at the rail gap when trying to find source of problem.

Take Care,
Chris




thanks 3 users liked this useful post by trainbuff
Offline kiwiAlan  
#2 Posted : 10 April 2022 01:00:27(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 6,855
Location: ENGLAND, Didcot
Originally Posted by: trainbuff Go to Quoted Post

As an improvements I want to 1) find material other than paper that will hold up to isopropyl alcohol used to clean the track and 2) trim a better track profile into the insulator.


I would use some Kapton tape. This is a teflon type tape with very good wear resistance, and extremely good insulation capability/

Originally Posted by: trainbuff Go to Quoted Post

As an example of the variability in the gap between rails here is another unmodified joint with a generous gap.
non-offending track connection.jpg

I guess what caught me off guard was assuming that all c-track joints always have a gap between the rails, so I wasn't looking at the rail gap when trying to find source of problem.


I wonder if you are being caught out by temperature variations causing the metal rail to expand and contract. That would certainly explain the intermittent contact you see with a rail that is almost making contact as per your first picture. I don't know how much the rails can move relative to the electrical contacts under the track bed, but it wouldn't be impossible to get a gap like the last picture when things are really cold.

I have been surprised at how much rails can move for seemly small temperature variations, leading to tracks going out of gauge when a layout is taken to an exhibition. a hall full of people is surprisingly warm, even if you don't think the temperature has changed that much. We also tend to think of metal as being a stable material, but the co-efficient of temperature expansion can be surprising. I don't know just what it is for the rails that marklin use, but it would be an interesting thing to find out.
thanks 1 user liked this useful post by kiwiAlan
Offline roberts  
#3 Posted : 10 April 2022 07:53:21(UTC)
roberts

Sweden   
Joined: 06/05/2020(UTC)
Posts: 34
Location: Göteborg
Originally Posted by: trainbuff Go to Quoted Post


As an improvements I want to 1) find material other than paper that will hold up to isopropyl alcohol used to clean the track and 2) trim a better track profile into the insulator.



I cut a small piece of electric tape and put between, I had to do this in several places on my layout.

All my 15 degree R3 pieces have this problem, and also a couple of straight tracks.
thanks 1 user liked this useful post by roberts
Offline pederbc  
#4 Posted : 10 April 2022 09:59:24(UTC)
pederbc

Sweden   
Joined: 11/06/2007(UTC)
Posts: 142
Location: Eslöv, Sweden
I have used clear nail lacquer painted thin on the rail end.

Br, Peder
thanks 2 users liked this useful post by pederbc
Offline Toosmall  
#5 Posted : 10 April 2022 12:11:03(UTC)
Toosmall

Australia   
Joined: 26/07/2021(UTC)
Posts: 186
Location: Sydney
Originally Posted by: kiwiAlan Go to Quoted Post
...but the co-efficient of temperature expansion can be surprising. I don't know just what it is for the rails that marklin use, but it would be an interesting thing to find out.


For those who can't do it on the back of an envelope!

https://goodcalculators....al-expansion-calculator/


A few common metals with their coefficient. Z gauge is nickel but I don't know what HO uses. If it is stainless there are different coefficients for different alloys. It most likely will be a 400 series alloy.

https://amesweb.info/Mat...-Coefficient-Metals.aspx


Don't forget to calculate the track base. The plastic will have a higher coefficient than the rail. Also factor in your layout base material. Probably lower. It's most likely the track base plastic which has the greatest coefficient.
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Offline rbw993  
#6 Posted : 10 April 2022 13:50:21(UTC)
rbw993

United States   
Joined: 19/08/2008(UTC)
Posts: 885
Or you could just file the rail end down. That will increase the air gap.
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Offline trainbuff  
#7 Posted : 10 April 2022 17:37:14(UTC)
trainbuff


Joined: 26/11/2006(UTC)
Posts: 507
Location: Atlanta, Georgia
Hi,

Thanks for all the great ideas. I tried one more thing, cut from Marklin c-track insulators, that seems pretty stable but is a lot of work cutting and trimming. I think I will try the idea of painting the track ends with something like varnish or liquid electrical tape. I tried filing and a rotary tool first, but I was not able to make a smooth cut nor was I able to control the depth of cut very well.
trimmed and ready to insert.jpg
I was able to get two of these L-shaped insulators from one c-track insulator.
inserted.jpg
Offline PacoM  
#8 Posted : 10 April 2022 21:49:47(UTC)
PacoM

Spain   
Joined: 20/08/2020(UTC)
Posts: 36
In case the gap is different at each end of the track, you could just push the rail. It is not fixed to the plastic bed, so that applying pressure to the end of the rail will make it slide back and increase the gap.
Offline nzrailfan  
#9 Posted : 11 June 2022 05:44:26(UTC)
nzrailfan

New Zealand   
Joined: 07/06/2022(UTC)
Posts: 6
Location: Otago, Dunedin
Had the same problem , just gently shaved the edge off the end of the rail with a Dremel cutting disc , problem solved , a file could also be used as stated in the thread earlier.
Offline JohnjeanB  
#10 Posted : 11 June 2022 12:00:40(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 2,080
Location: Paris, France
Hi
This is a common problem with C track. When brand new, the rails are kept a fraction of mm away but after a few years and temperature cycles:
- the rails expand and contract differently from the ballast (plastic)
- the plastic contracts and become less elastic with the solvant evaporation

This makes the rail to come into contact and then trigger a false detection.
So filing with a Proxxon / Dremel or with a file can correct the issue permanently.
Cheers
Jean
My layout videos
latest vid
hump yard
thanks 4 users liked this useful post by JohnjeanB
Offline Minok  
#11 Posted : 14 June 2022 20:46:13(UTC)
Minok

United States   
Joined: 15/10/2006(UTC)
Posts: 2,255
Location: Washington, Pacific Northwest
Feels like a good approach is to paint on an insulating lacquer on the ends where you have the contact tracks.
Then in the future, if and only when you find a false positive problem, then remember to look at the joints between track pieces and if needed cut the joint open again with a rotary and maybe insert a thin styrene piece which can then be painted and glue in place.
Toys of tin and wood rule!
---
My Layout Thread on marklin-users.net: InterCity 1-3-4
My YouTube Channel: https://www.youtube.com/user/Minok1217/
thanks 1 user liked this useful post by Minok
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