Espee99 Wrote:
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> Thanks for the information, but I am still a bit
> confused. In an area with lightweight equipment
> that operates frequently the rails should be clean
> and conductivity good, so why do they have issues
> if they have cleaned the rail(ground the
> surface)to get a good connection, and the daily
> freight train has no issues even when a single
> loco?

Espee99-- There is no real reason to be confused. Weight has nothing to do with it.
It could be (notice I said "could"_ that your lightweight equipment was designed incorrectly with insulated wheels like Speeders and Track Maintenance equipment.
My Uncle Roy was the Signal Maintainer in West Oakland. A basic track circuit, at least several years ago, was a set of caustic soda batteries connected in parallel across one end of a track block (let's say 1400 feet)... A DC Relay was connected in parallel across the opposite end of the same block. With NO trains present, the Relay is energized 24-hours a day... In so doing, it makes one or more sets of contacts which "may" operate certain wayside block signals. But 'NOT' crossing gates !!

When a rail car or locomotive enters the block at "either" end, the wheels SHUNT the track circuit causing the appropriate relay to RELEASE.

When the RELAY "releases" it makes another set of contacts and drops the original set, which will operate wayside block signals and "possibly" a set of "crossing gates"...

The primary reason for having the RELAY energized 24-hours a day is for full protection in case of a "brokern rail" situation !! A broken rail would be the same as a SHUNT by the wheels, causing the multi-contact RELAY to change state !!

My Uncle Roy told me long ago that the voltage on long track circit loops, supplied by Caustic Soda batteries was only about "EIGHT VOLTS" ... (8)...

Hope this helps sum !!

KRK