SP5103 Wrote:
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> SP bought the EMD TR6 demonstrator and three more
> sets. They ran on the NWP for a while as road
> units, not sure where else. At some point the
> calves where split from their mothers and assigned
> to dynamic brake equipped SW8's for the Roseville
> Hump.

Dynamic brake-equipped SW8's replaced the TR6A's while the units were on the NWP and SP's Schellville Branch, long before they were ever assigned to the Roseville hump. The only change made for hump service was the installiation of Hump Control, then later the removal of the train indicator boxes (which tended to block the view of the hump signals).

> My questions:
>
> Why did the the original sets get split up? I
> assume there was an advantage to having dynamic
> brakes on the hump? Parts lists show this as a
> 540a DB system - probably wouldn't develop more
> tha 20,000 pounds at 10 mph. Did these get 65:12
> motors and earin for hump service?

Mostly answered above. Don't know if they were delivered with a different gear ratio, but in the 11/67 roster book they all show as having 62:15.

> Were the SW8-TR6B hump sets connected by drawbars
> or couplers?

No.

> Were SP's TR6 sets built with full mu?

MU on the rear ends only.

> Portola has TR6A #1100 ex #4600 exEMD demo. Is it
> still missing the lower rear cab windows that TR A
> units did not have compared to a regular SW.


My guess is that the window was blanked on units equipped with two control stands like SP's, because that's where the air brake gauges had to be placed (similar to where they are on single control stand units).