Fairbanks-Morse Y-V

Details and Tribulations

We are fortunate to have the Fairbanks-Morse Y-V's original nameplate, which indicates that the engine produces 150 HP at 257 RPM. Built sometime in mid-1922, the Y-V bears serial number 501191. This engine has been a good runner for us and is a very popular attraction at our spring and fall shows. It has a 28-pole generator and should actually run at 257.143 RPM to produce 60 Hz power. 

We have no instruments accurate enough to measure the RPM to determine whether we are really running at the right speed, and for our operation it makes no difference as we are not generating electricity. We do light a bulb with the exciter, though. The governor is on the opposite end of the engine from the flywheel and is a very conventional spring fly weight arrangement. Spring tension (and speed) are adjusted by turning a nut, which changes the tension on the spring. Lubrication is total loss; the cylinders have oil pumped to them with a Madison-Kipp oiler. The main bearings are lubed with slinger rings and the rods with banjo rings. We probably over-oil the engine, but it is best to err on the side of safety.

We do not know the total number of hours on our Y-V, but based on what history we do know it must be many thousands of hours. To the best of our knowledge, the engine is still running with all its original babbitt bearings and piston rings.

The Fairbanks-Morse Y-V is started by lighting a propane burner on each head. The flame is directed at a hollow stud that protrudes from the precombustion chamber. When the studs are bright orange, the engine is ready to start. The method used here is really nothing more than a nonelectrical glow plug. This feature causes some people to refer to the engine as a semidiesel, but it is really just as much a diesel engine as any modern engine. There is a Run/Start handle on each head. When in the "Start" position, some of the diesel fuel from the injector is directed at a small plate and redirected onto the hot stud, which starts the combustion cycle. This small plate is sometimes called a spoon but technically is known as a splatter plate. When the engine is running, the spoon is moved to the "Run" position, which simply puts it to one side, allowing the injected fuel to be directed downward at the top of the piston. 

A little cooling water needs to be running through the engine prior to starting as the head heats up quite quickly and causes static water to boil and make steam. This in turn prevents water flow, and in such a situation things can go to pieces quite quickly. 

The Y-V is an air-start engine and operates only on the number one cylinder. This requires that the compression releases be opened and the engine barred around to the right place. We have found that 125 PSI air pressure is plenty to turn the engine fast enough to start. It helps to give the number one cylinder a few priming squirts. 

Our biggest starting fiascos have involved forgetting to close the compression release valves. This results in a big whoosh and a small rotation of the flywheel. It also results in our having to get the bar out and then rotating the engine back into position again. After warmup to about 150 degree water temperature, the Y-V will run with an almost clear stack, which is pretty good for a diesel engine in its nineties.

A Fairbanks-Morse Y-V needs some maintenance every 40 years or so, and we recently performed some fairly heavy maintenance on ours as follows. First, we replaced the gasket in the precombustion chamber, which had begun to leak. The head has to be removed to do this; we hoisted ours off with a forklift. We then had a new gasket made and put it back together. That sounds simple except that it is held together with one-inch studs. Standing on the platform and on ladders, we were not able to pull hard enough to get any reasonable torque on the studs. We have a torque multiplier but could not use it because there is not enough clearance around the nuts to allow a socket to be used. It must be done with an open-end wrench. We finally hooked a come-along onto the wrench and chained the other end to some of the roof supports and thereby managed to get the nuts tight. Not a very elegant method, but it worked!

Our next problem was algae that had invaded the fuel system. This filled a good bit of the fuel piping with a whitish-yellow glop. Getting this out and clean involved taking all of the plumbing apart and cleaning it out, which was a pretty good job. While we had this all apart, it seemed like a good time to reseat and lap all the check valves, which we did. We now use a biocide additive in the fuel to keep such a mess from accumulating again.

Since we were fixing things, it seemed like a good idea to repair one of the air valve housings that had a piece broken off the casting. (This was probably caused by someone's not tightening it evenly.) We took the housing to a shop in Riverside that has an expert in cast iron brazing on board. He did a beautiful repair job.

While this housing was off, we decided to take a good look at the air valves. This engine is crankcase-scavenged. It contains a set of check valves for each cylinder that let it take in air on the upstroke and then compress it slightly on the downstroke. When the piston is all the way down, it uncovers a port that allows this air to flow into the cylinder and provide a fresh start for the next combustion cycle. The valves as originally made by by Fairbanks-Morse consisted of thin steel rings with a leather facing for a seal. We found that they were in pretty bad shape with leather having come off of the backing in many places. 72 small compression springs (per cylinder) hold the valves rings closed. Many of these were badly rusted. We theorize that the leather retains moisture and that that moisture caused the rusting. We found a company that will make any kind of spring you want, very friendly and helpful but not at all bashful about its price. 

While everything was apart, we refaced the valve faces in our machine shop, which made them flat and clean again. We also had three brand-new sets of stainless steel valve rings installed by a shop that specializes in water jet cutting and that kindly said "No Charge" when they found out we were a museum. 

We went through a lengthly discussion about whether the valves should be refaced with leather again or perhaps with thin rubber. One of our people pointed out that compressors have been running for years with metal-to-metal seals and said he thought we ought to try it that way. The escape here was that if it did not work, we could always take it apart and go back to one of the other plans. The metal-to-metal arrangement has worked great, and so far it looks to be a long-term solution.

We plan to take the propane burners apart and clean the insides of them in the near future as well as to make sure all the crankcase bolts are tight and get a new belt made for the exciter. Something else is sure come up by the time we get this done, probably a day before the show.

Link here for information about the Fairbanks-Morse Y-V's AGSEM history.

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