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| After a number of years of dormant expansion, the Colorado & Southern finally reached the mining
town of Central City this winter. Only 3 years behind schedule. Lack of available resources to perform the
work was the official explanation. |
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Central City is the final stop on the Blackhawk & Central City branch whose yard is comprised of a run-around
and a stub siding with the branch feed from the left side.
After the track was in, the electricians appeared and spent some time unraveling the mystery of how to wire the
yard. Figure 1 illustrates the dilemma..
Figure 1 |
Block 'A' has it's own power feed (the C&S uses traditional two cab block control), but the question is, how do
we power blocks 'B', 'C' and 'D' for the simplest of operability?
| Option 1. |
Following traditional MMR philosophy, Block A would feed blocks B & C through
selective routing of the adjacent turnout. How do we power Block D then? |
| Option 2. |
Allow Block D to feed Block B & C instead of using Block A. The problem here
is if you 'park' a train in D, no other trains can enter or leave Blocks B & C. |
| Option 3. |
Use separate power feeds for each of the blocks. It'd work but require four
separate toggle switches on the control panel. There's got to be a simpler way! |
| Option 4. |
Use separate power feeds for Blocks A, B & C and allow Block D to be powered
by the adjacent block which the turnout is facing. e.g. Block B powers Block D
when the right hand turnout is routed to Block B. |
The Electricians felt Option 4 would support all operation scenarios and be
simplest to operate. The tortoise switch machines did not have enough contacts to handle
routing of the power so an additional DPDT 5vDC relay was added. Figure 2 is the
schematic for what was ultimately implemented.
Figure 2 |
The tortoise switch machine provides three functions; i) the physical movement of the
turnout's points, ii) power routing for the non insulated frog (the turnouts are handlaid),
and iii) powers the 5vDC relay. The 5vDC relay connects Block D rails the to appropriate
Block (B or C) for power.
Yes this solution did require the addition of a relay, but ultimately, it resulted in one
less toggle switch on the control panel that has to be managed. Of course, if this was
DCC Command Control, it would be even simpler still!
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