Tunnel Motors

[Kootenay Central]

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[THE.RR]

The Tunnel Motors worked so well even the Cotton Belt (SSW) bought them. Those tunnels in Texas and Arkansas must be murder.

[caldreamer]

SP had problems with engines overheating in the tunnels and snow sheds on Donner pass between Colfax and Norden.  They asked EMD to come up with a solution.  It was to make the intake radiators larger and move then just above the walkway.  This brought in cooler air from below, instead of the hot air near the top of the tunnel given off by the exhaust of  the engines.   Worked quite well.  UP still uses the tunnel motors they aquired from SP & D&RGW..

[daveklepper]

Note also that most mainline locomotives today have air-conditioned cabs, that metalurgy has improved, insulation allows motors and alternators/generators to operate at higher temperatures, etc., all of which mitigate the problem to some extent.  As regards loosing power, the reduction in the number of snowsheds allows more recovery time.

[Railway Man]

After all these years, maybe it was finally cheaper to improve the tunnel ventilation then it was to purchase locomotives with a more "specialty" design?

There are only a handful of ventilated tunnels in North America -- Moffat, Mount Macdonald, Cascade, and Flathead are the only western tunnels I can think of with active ventilation plants. None of these tunnels would be operable using any type of diesel-electric motive power without ventilation plants.  These ventilation plants are to remove exhaust and provide clean air for human respiration and engine combustion, not to remove heat.  The tunnel motor variant was not designed for these very long tunnels. 

The relative location of cooling air intakes on EMD and GE locomotives has no relationship with market share now or in the past. 

Improvements in locomotive emissions under Tier 1 and Tier 2 actually place a greater demand on cooling.  

RWM 

[ericsp]

There have been several threads about this. EMD improved the cooling on its locomotives.

[stmtrolleyguy]

After all these years, maybe it was finally cheaper to improve the tunnel ventilation then it was to purchase locomotives with a more "specialty" design?

[Anonymous]

there a couple of changes EMD made to their units as the newer models have come on line. One is that the radiators themselves are considerably larger, as well as the water tank is bigger. more water and larger surface area mean better cooling. also, if you notice on the SD70M's there is a third smaller radiator intake below the 2 big primary intakes on each side. also, although i don't know this for sure, i believe the fans themselves are bigger on the new units. as for the SD90MAC's, it's pretty obvious EMD at least somewhat, studied GE's intakes, although the entire design is a completely different principle than GE's. as a little side note, the 90MAC's and the AC6000's both use antifreeze instead of plain water with some treatment.

[Anonymous]

I would have to agree with Dan...tho i dont know very much about the engines themselves. if you look at most of the GE units, all the air intakes are on the bottom rear of the long hood. that does not explain the EMD units though. they still have the air intakes in the same place.

[Anonymous]

Today there is less then one mile of Snow Sheds remaining. However the problem that lead to the design of the "Tunnel Motor"is still present. Tunnel 41, known at "The Big Hole" is two miles long. Also the present speed limit for Amtrak on the Donner Pass Route is 30 MPH. That puts you in The Big Hole (Tunnel 41) for 4 minutes. I have heard of problems with smme of the UP units stalling in the tunnel.

[Anonymous]

Just an observation, the GE units all ways had a design like the tunnel motors and now that GE is the dominant maker now days it stand to reason that you would not be seeing as many EMD's with the tunnel design. Just an observation.

[Anonymous]

I recently rewatched several videos that included both older SP and newer UP/SP in the Donner Pass area. In the older videos nearly all trains were pulled by pure sets of "Tunnel Motors". In the newer videos what tunnel motors were included in the consists were in the minority, and could be seen anywhere in the consists. Even though some tunnels and snowsheds have been removed, it seems like many of the conditions that led to designing tunnel motors in the first place still exist. Have the newer locomotive designs cleaned up the exhaust and improved engine cooling (One of the main reasons for tunnel motors in the first place)to such an extent that the tunnel motor design is no longer required? Ron