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Offline efel  
#1 Posted : 29 July 2008 18:45:59(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Hi all,

I've noticed that the contact tracks are widely used by the members of this forum, including myself.

What surprises me is that there is no (or few) problem related to bad running of locos on those tracks.

In my case, my E69 loco had erratic running, or even stopped, on contact track, and the reason is the following: The E69 has only 4 wheels whose 1 rubber tyre. That means that, depending on the direction of travel, only 1 conductive wheel is on the grounded rail, the other 2 are on the sensing rail. Then, if the track is not perfectly plane, the conductive wheel may not contact the ground, and the return current of the loco motor (or decoder) is "sent" to the contact rail that is not grounded. That means that the motor is no longer fed and the loco stops, at least for a while (inertia). That appears also of course if the track is perfectly clean. I personally solved the problem with some electronic.

But I am curious to know why this problem has not been reported?
Could be:

1- No use of "4 wheels only" loco with traction tyre?
2- Track perfectly plane?
3- problem appears only occasionally?
4- No use of contact track?
5- ...

I would appreciate your answer, even with no comment giving only the case# above. Of course comments are more than welcome!

Fred
Offline Hajime  
#2 Posted : 29 July 2008 19:07:42(UTC)
Hajime

Japan   
Joined: 29/01/2002(UTC)
Posts: 88
Location: ,
Hi, Fred-san,
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by efel
<br />
But I am curious to know why this problem has not been reported?


My case is;

1- No use of "4 wheels only" loco with traction tyre.
Offline David Dewar  
#3 Posted : 29 July 2008 22:11:15(UTC)
David Dewar

Scotland   
Joined: 01/02/2004(UTC)
Posts: 6,983
Location: Scotland
I use several contact tracks with no bother. I think as you say the track must be laid properly. I use C track and it is laid flat. I would not use a contact track or turnout etc as the start of a gradient.

David
Take care I like Marklin and will defend the worlds greatest model rail manufacturer.
Offline perz  
#4 Posted : 30 July 2008 01:01:14(UTC)
perz

Sweden   
Joined: 12/01/2002(UTC)
Posts: 2,577
Location: Sweden
The problem has been discussed before, but it is a long time ago. On our company layout which we run unattended we wanted to be on the safe side, so we use current sensing on the center rail instead of contact tracks. I know that some people have proposed a solution where you short the isolated section to common ground with a pair of diodes, and use a more elaborated read electronics which can distingwish between a track directly shorted with wheels and one which is shorted with diodes.
Offline efel  
#5 Posted : 30 July 2008 23:11:28(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by Hajime
<br />Hi, Fred-san,
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by efel
<br />
But I am curious to know why this problem has not been reported?


My case is;

1- No use of "4 wheels only" loco with traction tyre.


Hi Hajime-san,

Thanks for your answer.

regards,
Fred
Offline efel  
#6 Posted : 30 July 2008 23:17:22(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by David Dewar
<br />I use several contact tracks with no bother. I think as you say the track must be laid properly. I use C track and it is laid flat. I would not use a contact track or turnout etc as the start of a gradient.

David


Thanks for your answer, David.
Did you have the opportunity to run on your layout an E69 or a Glaskasten or other 4 wheels/1 tyre loco?
Regards

Fred
Offline efel  
#7 Posted : 30 July 2008 23:30:14(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by perz
<br />The problem has been discussed before, but it is a long time ago. On our company layout which we run unattended we wanted to be on the safe side, so we use current sensing on the center rail instead of contact tracks. I know that some people have proposed a solution where you short the isolated section to common ground with a pair of diodes, and use a more elaborated read electronics which can distingwish between a track directly shorted with wheels and one which is shorted with diodes.


Thanks for answering, Perz.
I tested several solution that all works very well, and have used one of them on my layout for 3 years now.
I also use current sensing of the center track to detect locos occupancy, but in my case, contact tracks are complementary to detect occupancy of wagons.

Regards

Fred
Offline David Dewar  
#8 Posted : 31 July 2008 01:03:32(UTC)
David Dewar

Scotland   
Joined: 01/02/2004(UTC)
Posts: 6,983
Location: Scotland
Hi Fred I have run 4 wheel locos and they have been OK.

I have not run a loco without a traction tyre but if you removed it and did not have inclines or many coaches to haul would this help.

What about adding extra weight to the loco. Looking again at my contact tracks they are all very level and this maybe why I do not have a problem.

David
Take care I like Marklin and will defend the worlds greatest model rail manufacturer.
Offline efel  
#9 Posted : 01 August 2008 00:07:10(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by David Dewar
<br /> Looking again at my contact tracks they are all very level and this maybe why I do not have a problem.


Very good layout work, David. Congratulations!

Fred
Offline kbvrod  
#10 Posted : 01 August 2008 06:55:45(UTC)
kbvrod

United States   
Joined: 23/08/2006(UTC)
Posts: 2,597
Location: Beverly, MA
Hi all,
Fred-sama,.....please.

Dr Domo
Offline efel  
#11 Posted : 01 August 2008 10:55:11(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Hi Dr Domo-sensei,

Do you use contact tracks and run 4 wheels locos?

Fred
Offline Goofy  
#12 Posted : 01 August 2008 12:19:33(UTC)
Goofy


Joined: 12/08/2006(UTC)
Posts: 8,427
Why only using contact-track...?

You can also using Opto-contacts too like from Uhlenbrock.

Goofy
Offline Lars Westerlind  
#13 Posted : 01 August 2008 13:09:50(UTC)
Lars Westerlind


Joined: 19/10/2001(UTC)
Posts: 2,379
Location: Lindome, Sweden
Well,
I have had problems like this in the past:
A. very poor M-track; cleaning was the obvious cure.
B. poorly laid curves.

Now I use C-track in better condition, and I do think I'm better in laying track. And I also avoid two axled vehicles, for just this reason. But not completely.

/Lars
Offline renevoorburg  
#14 Posted : 02 August 2008 18:22:10(UTC)
renevoorburg


Joined: 16/10/2005(UTC)
Posts: 382
Location: Planet Earth (mostly)
Quote:
[size=1" face="Verdana" id="quote]quote:
5- ...


Maybe this solution for number 5: http://www.stayathome.ch/Rueckmeldemodul.htm
(or try http://translate.google.com/ and use your favorite translation). I wonder how it works... Anyone tried it yet?

René
Offline efel  
#15 Posted : 02 August 2008 19:59:31(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by Lars Westerlind
<br />
... And I also avoid two axled vehicles, for just this reason. But not completely.

/Lars


Lars,

Thanks for answering. I see the problem with 2 axles locos was not only mine.
I'm not sure to fully understand what you mean by "not completely". Is there another reason for which you avoid small locos?

Fred
Offline efel  
#16 Posted : 02 August 2008 20:05:26(UTC)
efel

France   
Joined: 23/02/2005(UTC)
Posts: 800
Quote:
[size=1" face="Verdana" id="quote]quote:Originally posted by renevoorburg
<br />
Quote:
[size=1" face="Verdana" id="quote]quote:
5- ...


Maybe this solution for number 5: http://www.stayathome.ch/Rueckmeldemodul.htm
(or try http://translate.google.com/ and use your favorite translation). I wonder how it works...
René


René,

Thanks for this link. I did not know this interface.
Stress the fact that the problem is real.

I have not found the electrical diagram, but it seems (seeing the PCB picture) that the loco decoder is fed through 2 diodes in anteparallel, that allow a small 0.8V drop voltage.
Operational amplifier detects shorts and current in the diodes, i.e. if there is a loco with good or bad contact between track and wheels, or a wagon. Optocoupler drives the S88 input.
(see also Perz comment above)
I personally don't see the need for such a luxurious solution, if S88 is used. May be for very sensitive mfx locos (I don't have mfx!)?

Fred
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