View source for ALCO S-5

{{Infobox locomotive
|name=ALCO S-5
|image=B&M 864 in North Station yards, September 1965.jpg
|alt=A red locomotive in a freight yard
|caption=B&M S-5 #864 in Boston in September 1965
|powertype       = [[Diesel-electric]]
|builder=[[American Locomotive Company|ALCO]]
|buildmodel=S-5 (Specification DL421 and DL421A)
|builddate=June 1954
|serialnumber=80915–80921
|totalproduction=7
|gauge={{RailGauge|ussg}}
|aarwheels=B-B
|primemover=[[American Locomotive Company|ALCO]] [[ALCO 251|6-251]]
|cylindercount=[[Straight 6]]
|poweroutput={{convert|800|hp|abbr=on|lk=in}}
|operator        = [[Boston and Maine Railroad]]
|locale          = [[United States]]
|fleetnumbers    = 860-865, 909
|disposition     = 1 preserved, remainder scrapped
}}
The '''Alco S-5''' (DL 421A) was a [[diesel-electric powertrain|diesel-electric]] [[switcher locomotive]] rated at {{convert|800|hp}}, that rode on two-axle [[bogie|trucks]], having a [[AAR wheel arrangement#B-B|B-B]] wheel arrangement.

This was Alco's second attempt to build a replacement [[ALCO 251|251]]-engined switcher to replace the [[ALCO 539T|539]]-engined [[ALCO S-1 and S-3|S-3]] and [[ALCO S-2 and S-4|S-4]]. Only seven were sold. The demonstrator unit was ALCO specification DL421 and the six production units were ALCO specification DL421A. Alco fitted the 251A engine in its replacement, the [[ALCO S-6|S-6]] with power output raised by {{convert|100|hp}}.

==Original owners==
{|class="wikitable"
! Railroad !! Quantity !! Road numbers !! Notes
|-
| [[American Locomotive Company|Alco]] (demonstrator) ||style="text-align:center;" |1 || 909 || to Island Creek Fuel and Transportation Company #102
|-
| [[Boston and Maine Railroad]] ||style="text-align:center;" |6 || 860–865 || 
|-
|}

== See also ==
* [[List of ALCO diesel locomotives]]
* [[List of MLW diesel locomotives]]

==External links==
{{commons category-inline}}
* Sarberenyi, Robert. ''[http://www.trainweb.org/jaydeet/s6.htm Alco S5, S6, and SSB9 Original Owners]''.

{{ALCO diesels}}
{{Diesel_Switchers}}

[[Category:B-B locomotives]]
[[Category:ALCO locomotives|S5]]
[[Category:Diesel–electric locomotives of the United States]]
[[Category:Railway locomotives introduced in 1954]]
[[Category:Standard-gauge locomotives of the United States]]
[[Category:Shunting locomotives]]

{{diesel-loco-stub}}