One of the locomotive curiosities that caught my attention after my recent trip out west was the oil burning steam locos of California. Most of us steam lovers across the east and Midwest understand the firebox of coal fueled steamers. But I wasn’t exactly sure about those oil burners of the west. My curiosity was first stoked by the following pic. This is AT&SF #5035, a 5011 class Texas, 2-10-4 in the PRR yard at Columbus OH, 1956. This is probably the last steam loco Santa Fe had built. – Built by Baldwin in 1944, it was the last of the 5011 class of 25 locos numbered 5011 through 5035. All 25 of the class 5011 were retired by 1959 with 4 of them currently preserved.
So the pic has #5035 sitting in the Columbus yard, surrounded by several PRR steamers with typical coal filled tenders. The Santa Fe tender isn’t shaped much differently except the top is sealed by a set of continuous plates. Notice how the sides rise higher all the way to the back – pretty much level with the coal bins of the PRR locos. AT&SF commissioned these tenders specifically for their oil fueled locos. With the raised sides they held a bit more water than the similar sized tender – I believe these were the 20,000 gallon “square” tenders. The fuel bin of the Santa Fe tenders was shaped just like a coal bin except that the top and front were sealed with steel plates. Many of the early AT&SF commissioned tenders were dual purpose – they had a typical coal bin where an oil tank was inserted for the oil-burners. These “square” tenders were built similar with the bin shaped like a coal bin, but the bin was sealed for the oil storage. Note the oil spills around the front hatch.
In the very early days of oil fueled steamers – post 1890 – the AT&SF used a lighter oil. But as the automobile industry started a demand for gas in the early 20th century, they switched to a heavy oil, similar to home fuel oil. The oil was gravity fed to the lower part of the fire box where a steam jet sprayed the fuel into the box as an aerosol.
One of the interesting points about oil-burners is that you need steam to spray the oil into the fire box. Most oil-burners were lit in the shop where they could fill the boiler with shop provided pressurized steam so that the fuel jets would work. Some trains carried an extra steam car such that if the fire went out, it could be relit with the spare steam.
Here’s a modern pic of a restored AT&SF oil-burner – #3751, a Northern 4-8-4, class 3751 (first of this class). While the front view hides most of the tender, you can again see the “square” tender behind the loco. This is the same 20,000 gallon tender, but some of the tenders, such as this one, were equipped with roller bearing trucks for passenger service. The rivet pattern reveals the front fuel bin from the water tank.
This modern pic of #3751 gives us a better look at the tender
Frisco (St. Louis – San Fransisco) had some Northern 4-8-4 locos built as oil-burners. #4500 was the first of three in a series, 4500 – 4502, built by Baldwin in 1943. These three locos pulled the Frisco Meteor, a passenger train from Oklahoma City to St. Louis via Tulsa. This is a modern pic that shows #4500 with a long haul tender that appears to have an oil tank insert in the coal bin. The oil tank insert could carry 6,500 gallons of oil along with the 18,000 gallons of water in the standard water tank.
Southern Pacific introduced “whaleback” tenders for oil-burners. The “whaleback” tender had two tanks, the rear for water and the front for oil.
The SP cab-forwards were oil-burners (with the firebox at the front of the locomotive, there was no convenient way to fire it with coal). #4207 was provided with a “whaleback” tender which was made with larger capacities for both oil and water.
These two SP articulated cab-forwards (#3905 in the lead) have “whaleback” tenders.
When SP got to the later class AC-4s, 4-8-8-2s, they used Vanderbuilt tenders modified with an oil bin.
The larger, more modern cab forwards stuck with the oil-bin Vanderbuilt tenders for a while.
The last and largest of the cab-forwards went to a more standard long-haul style tender with an oil-bin.
I’m not sure if these were standard tenders with coal bins and oil inserts were added, or whether they were built with the bin modified for the oil storage specifically for the cab-forwards.
A point not made yet was that with a heavy oil, temperature could make the oil almost as thick as tar. Almost all of these oil-bin tenders had oil heaters. And some, like the SP cab-forwards, pressurized the oil-bin to assist in the flow (and get the oil all the way to the front end firebox). But more common than a pressurized fuel bin, once the oil was heated, gravity alone was typically enough to get the oil to the steam jets which sprayed it into the firebox (when the firebox was in the rear next to the tender). And the firebox grate was replaced by a flat surface of fire bricks. Once the bricks heated up, even if a draft blew out the flame, the heat of the bricks would restart the fire as the jets sprayed the atomized oil into the box. From the outside, the firebox didn’t look much different. But with the flat surface of fire bricks, there were draft vents that controlled the air intake. I don’t think the ash pan was needed, but I’m not sure it was replaced by anything related to the oil burning.
One of the important aspects of the oil-burners was controlling the spray of oil. Too much oil, and the fire became inefficient – lotsa black smoke. Not enough oil, and the heat dropped, inefficient burn, lotsa black smoke, and loss of power. When idling, steam was conserved, the oil spray could be minimized to control the heat. But when the engineer changed the throttle setting, the spray had to increase before the heat was lost. The fireman was in charge of spray – he had to coordinate closely with the engineer as the engineer moved the throttle. The fireman also had to control the heaters in the tender to keep the oil flowing. And on top of that, he had to control the draft into the firebox to keep the burn clean. The fireman on an oil-burner had a little different job than the old days when he shoveled coal and adjusted the distribution on the grate.
Unfortunately, my research didn’t take me to any pics or diagrams of the firebox and oil heaters. …I guess I’ll have to return to this topic sometime in the future!