Isolating loops

[Bino]

I've created an isolated section for my fiddle yard loops with two rail breaks. The isolated section is big enough to accommodate my largest loco.

 

Ok so far, however when testing my Heljan class 26 sails through the isolated section.

 

So, have I missed something or is there something unique about this loco that means I need to try something different?

[Brian]

Both rail breaks need to be in the same sides rail and placed further apart than the longest loco. This will stop any loco when it enters the section, so long as the Isolating switch is Off (See next line).

You will need to feed track power via a suitable switch e.g. On-Off type to the isolated rail section,  the feed to the switch coming from the same controllers terminal that feeds the rail before the break or the switches feed comes from the rail before the gap / insulated rail joiner. i.e. it links out one ends IRJ or rail gap.   

 

This shows the basic idea on DC layouts  http://www.brian-lambert.co.uk/Electrical.html#Isolating

[Bino]

Thanks Brian,

 

this is exactly what I have done (althoughat the moment it is unswitched) and it works for most of my locos but ths Heljan 26 seems to defy logic.

 

Could the class 26 have a unique pick-up system?

[SwissRailPassion]

If you are running at speed or even a moderate pace Heljan locos run on. Try one one a normal stretch and cut the power, it will glide on twice its own length.

[cliff park]

Flywheels maybe?

[34theletterbetweenB&D]

...my Heljan class 26 sails through the isolated section.

 

So, have I missed something or is there something unique about this loco that means I need to try something different?

 Is the intention of the isolated section to create an 'auto stop' in the fiddle yard by the loco coasting or skidding to rest on the dead section?

 

If so you probably do need to  think again, and not just for free running flywheel equipped locos like the Heljan 26. If you have metal wheels on your stock and run significant train weights, then between the complete train's inertia and metal wheels momentarily bridging the isolating gap and giving the motor brief bursts of current, you may find trains 'coming on through'; even if the dead section will stop the loco alone.

 

One solution is a slow approach section, another permanently isolated section ahead of the switchable isolated section, but with a permanent supply from the supplying controller with diodes in line to reduce the current supply so that the train slows enough in this section for a reliable stop when the loco enters the isolated section. (The obvious 'extend the dead section' solution typically eats that bit more space than we have available!)

[Brian]

It's has to caused by a fly wheel in the loco, if only the loco is used and doesn't stop in the section which is longer than the loco plus 50mm or so.

[Bino]

If you are running at speed or even a moderate pace Heljan locos run on. Try one one a normal stretch and cut the power, it will glide on twice its own length.

Thank you all for your help and suggestions. I've had another look at this and the loco in question (even at moderate speed) is indeed 'running on' sufficiently to pass through this section.

 

I like the idea of a slowing section but to keep things simple I will just impose a speed restriction in the loops.

[Memphis32]

The alternative is to use the section switch to short the rails together - ie use a changeover switch - common to the isolated rail, one throw to the controller (or the next bit of track), the other throw to the opposing rail in the isolated section. That will give it an electronic brake...