The Cab Forward, synonymous with the Southern Pacific, was the distict type of locomotive created by the necessity to solve a problem.
The Sierra grades had a lot of curves and long sheds to protect the track fron snow. Conventional steam locomotives with the cab next to the tender showed to be not suitable. The crew had poor visibility to the track adead and they suffered in the sheds due to the hot and toxic exhaust gases of the locomotive.
The solution was very simple - the locomotive itself was turned around and coupled to the tender on the smokebox side. The visibility now was perfect and the stack far behind the cab.
The external look of the locomotive changed drastically. But technically a Cab Forward is very similar to any normal steam locomotive. The Cab Forward fascinates me - I'm a real fan of Cab Forwards.
Southern Pacific liked them. From 1910 on to 1944 they bought many series of Cab Forwards from Baldwin. The first versions look quite "tinkered", later versions had a more constructed look.
SP #4010 AC-1
The AC-1 was the first series of Cab Forwards that SP bought. When put into service they were compound locomotives of the Class MC-1.
Later SP rebuilt the 2-8-8-2 to single expansion.
The model shows a locomotice freshly out of the shop - shiny new tires, clean external look.
The Class AM-2 had a different axle configuration - they were 4-6-6-2.
SP used them first for passenger service. SP bought them as 2-6-6-2 "Malets", later they were rebuilt to single expansion.
Also this type of Cab Forward had a flat face.
The Cab Forwards were successful, thus SP went to Baldwin to improve the design and purchase more locomotives.
The AC-4 came in 1928 - they were bigger than there precessors, they had a wheel configuration 4-8-8-2 and were delivered as single expansion articulated locomotives.
They had a round cab-roof but still a flat cab-front. The model shows the mountain configuration with a large snow plow at the pilot.
I like the snow plow versions - they look so handsome!
The AC-5 look very the same as their precessor the AC-4.
SP took them into their roster in 1929.
The #4116 has a conventional pilot.
When delivered the AC-6 had on the cabside the same appearence as their precessors. #4138 was involved in a collision and SP repaired the locomotive to look like later versions of the Cab Forwards. The repaired cab looks more streamlined than the original version.
This locomotive has also a snow plow installed.
The AC-6 was improved in many technical features - this is visible in the external look when closely examined. As first series the AC-6 had the air-pumps installed at the smokebox-front - a typical look of later Cab Forwards.
In 1944 SP went back to Baldwin to order the last series of Cab Forwards. Due to the war restrictions the railways were obiged to buy proven existing types - so SP took the last batch of Cab Forwards into their rooster. #4294 is the last locomotive of the Calss AC-12. It is the only Cab Forward saved from scrapping - tody it can be examined in the Sacramento Rail Museum.
SP Cab Forward Tender Class 120 with booster
Early Cab Forwards were equiped with the whaleback-tender.
This specific tender had a booster truck to encrease the starting tractive effort of the locomotive.
"Southern Pacific Lines" was the early lettering version.
SP Cab Forward Tender Class 120
A standard whaleback tender with the later lettering "Southern Pacific"
SP Cab Forward Tender Class 160
The AC-4 to AC-6 Cab Forwards had the six axle round tender.
This version is lettered with the early style.
All tenders for Cab Forwards had pressurized fuel tanks to force the oil to the firebox at the front end of the locomotive.
From outside this is visible on the top of the oil tank at the oil cap and its fixations.
SP Cab Forward Tender Class 160
This foto shows the later version of the round tender.
All tenders of this class had Commonwealth 6 wheel trucks.
SP Cab Forward Tenders Class 220
All modern Cab Forwards of the Class AC-7 to AC-12 had the large rectangular tender of the Class 220.
They where equipped with Buckeye-6 wheel trucks.
Typical smoke box configuration of a cab forward