Nudge Wrote:
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> The 3200's on the SP had a gearing of 70 mph max.
> When they were using them on the commutes, they
> had a switch that allowed faster transitions and
> other electrical switching getting up to to 70 at
> much faster rate like the FMs.
>
> A lot of the old SP F units still had 79 mph
> gearing until they were sold off or scrapped. The
> ones that went to ATK were 79 mph.
>
> Some of the early SDP's may have had gearing for
> 79 mph By 1969 I think all the old 79 territory
> had been lowered and the max on the SP was 70 mph.
>
>
> Nudge

SP's SDP45's were deliversed with 62:15 gearing for a maximum speed of 70 MPH (many other railroads permitted a maximum speed of 65 MPH with this gearing). The train overspeed was set to trip at 72 MPH, initiating a Penalty brake application.

This precluded the units from maintaining the schedule in 79 MPH territory, so SP changed the gearing to 60:17, permitting 79 MPH operation. The overspeed was set to trip at 83 MPH.

After the units came off lease to Amtrak and were assigned to the Commute Pool, all exept 3201 and 3207 were converted back to 62:15 (which is why those two units were commonly used on company Officer's Specials).

At the same time, all 10 were modified with a toggle switch in the electrical cabinet marked COMMUTE, which would cause the locomotive to start moving in Parallel instead of Series. It was similar in function to the Passenger Start feature on Amtrak's SDP40F's. The toggle switch was supposed to be in COMMUTE when the unit was in Commute service, and PASS/FRT at all other times. Unfortunately, the modification tended to be a source of trouble when the units were used in freight service; they wouldn't always make backward transition from Parallel to Series, and would stop loading.