Naturally, as things progress – engines got bigger. For Fairbanks-Morse, the 31A18/31AD18 was the largest production engine they made…at least until the 1960’s…but we will get to that later. Fairbanks-Morse introduced their line of 31A engines around 1945 or so, calling them the new “En-bloc” engines, meaning “as a whole” in the dictionary. While previous FM engines were made of various castings, bases, liners, air box, exhaust belt, etc., the new 31A line used a one-piece cast block, in which the cylinder liners went into (not on top of like earlier models). The cam and main bearing pockets were cast right into the block, ensuring perfect alignment every time (or so they touted), as well as featuring an integral oscillating scavenging blower. The 31A series was offered in a 6 ¼” and an 8 ½” bore for marine and stationary service, as well as a giant 18” bore engine for stationary power generating service, and thus the 31A18 was born.
The 31A18 used an 18” bore, with a 27” stroke, rated at 277 RPM. FM also offered the 31A18 in a dual fuel model, the 31AD18 – which used diesel as a pilot fuel for natural gas operation. The engines were offered in the following configurations:
– 6 Cylinder, 2100HP, 140,000lb/143,000lb (31AD18)
– 8 Cylinder, 2800HP, 193,000lb/197,000lb (31AD18)
– 10 Cylinder, 3500HP, 247,000lb/251,000lb (31AD18)
One of the few options offered was in way of the scavenging blower – The engine could be equipped with an oscillating vane blower, or none at all, with the scavenging air being supplied by a separate motor driven blower in the plant. It appears most applications went with the separate motor driven unit. Lubricating oil was supplied by a duplex system with an engine driven gear pump handling piston cooling, main bearings, crankpins, camshaft, injection pumps and blower (if equipped). A separate pair of Madison-Kipp lubricators driven off the main camshaft supplied oil to each cylinder liner wall by means of 6 lines going to each. The camshaft also chain drives the fuel oil service pump. Jacket water cooling is handled off a main header (remember, there is no internal water passages in the cast block) on the lower potion of the block, up through the liners and heads, and out through an upper header. The engine has no water pumps of its own (common in large stationary engines), with separate motor driven pumps for the closed loop soft water in the engine, and a raw water system for the heat exchangers.
The 31A/31AD18 were essentially the same engine except for the dual fuel equipment. In addition to the standard equipment, the 31AD18 used an additional chain driven upper camshaft to control the gas admission valves, supplied by a separate header on the top end of the engine.
Around 1955, Fairbanks Morse added to the 31A18 line, by introducing a 12-cylinder option, putting out 4200HP. Production of the 31A18 lasted until the late 1960’s – well past the production of all of the other FM engines that were not model opposed Piston models. While FM does not support the 31A18 line anymore, there are still numerous examples of these engines still in service in various municipal power plants. While the 31A18 family was the largest production Fairbanks Morse engine, it was not the largest. That honor would go to the 38A20 Opposed Piston engine.
Midway Island, part of the Midway Atoll in the Pacific is home to a small power plant with a single FM 38AD18. Check out this link for photos of the Midway power plant. Note that this engine has the attached engine driven blower.
Midway Island Power Plant Photos
As always, I welcome and and all comments, additions, corrections and anything else.
7 thoughts on “Fairbanks-Morse 31A18”
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There is four big fm engines located in camfield ohio along with a cooperbessember thzt ive never seen listed among their engines,the mechanics had it apart to change it from diesel go natural gas the pitons were as big zs 55gallon oil drums i shit you not!!This was back in 1987 i was with a guy deliveringa resaw machine to this outfit that made furnature molding and trim,they also owned these six enormous engines 2 weree 2 cylinder fm 2 were 4cylinder fm 2were 6 cylinder fm and the last was this big cooperbesember engine,thzt was far bigger than the six cylinder fairbanks engines ive not been able to find anything on ghem since ,it was my understanding at that time this company had over 4400 acres of land and gas was found on it so they decided to run the factory on generatec power from these monster engines then sale electric back to the power company,at leastes thats what the shop foreman told me and mybuddy at that time.
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We still have two of these units in operation. 10 cyl. 3500HP. They still run great. Ours have large flywheels between the generator and the outboard bearing. I would be happy to get you pics if ever needed. We also have a Nordberg from ’61 I think, its counter rotating and quirky to say the least.
The 31a18s that you don’t know about, are in Goodland power plant in Goodland Kansas https://www.facebook.com/cityofgoodland/videos/goodland-power-plant-capacity-testing-2018/10155425247750843/
The 2 31AD18s are in Goodland power plant in Goodland kansas. They also have a few Colt Pielsticks, 38 8 1/8s and 33s.
Anyone ever find any info on that power plant located in camfield ohio?I’d really like to go get some.pics of that enormous Cooper Bessemer they say they never made!Joln thompson a fellow I worked.with said his dad was a welder for Cooper,Bessemer and when he was only 15 his dad took him to a site where according to joln his dad worked on one(cracked block)