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Diesel Service Updates

Diesel Service Report – July 11, 2020

By July 11, 2020January 26th, 2022No Comments

Diesel Service Report, July 11th, 2020

USAF 1601

When 1601 arrived at the museum several years ago, there were two traction motors that were not functional. Both had been electrically disconnected from the locomotive but were still part of the trucks. The locomotive was then operated using the two remaining good traction motors.

Recently we were able to purchase a spare truck for the locomotive and that included the two traction motors that we needed. However, it is easier to change the complete motor and wheels/gear set rather than just the traction motor.

Two weeks ago, Carl Pickus and Doug Newberry removed the new (to us) wheel assemblies from under the truck and prepared to install them into the trucks from under USAF 1601.

This past week, Carl, Frank Kunsaitis, and Doug, worked Monday, Wed, and Friday, installing the new wheel assemblies, called combos, into the trucks from under 1601.

The first task was to remove the faulty combos from the old trucks. This photo (left )shows it as Carl used his deck crane to lift the truck frame off of the first old combo.

Once that was completed, the new combo was rolled under the truck and the crane then carefully lowered the truck down onto the journal boxes which keep the axles in place. This next picture shows the truck being lowered onto the journal boxes as Frank keeps them rotated so they line up correctly. Notice the new gray motor compared to the old black truck frame. Frank also installed the journal box oil wicks at that time. That was much easier to do than later when the axles were totally down. The journal boxes on 1601 appear to be smaller than the journal boxes on full size locomotives and getting the brass bearings and wedges in place was very difficult.

By the end of Friday, they had both combos installed into the original trucks from under 1601. That was a marathon effort in extremely hot weather.

Saturday, Doug and Carl started to reinstall the brake rigging that had been removed to make room for replacing the combos.

When the original brake rigging was removed from 1601’s trucks, one piece was found broken and another bent. That forced one of the brake shoes to ride off center on one of the wheels.

That resulted in ruining one of the original brake shoes. The left side of the shoe in the picture (right), should be totally flat with the rest of the shoe. Note the ridge on the left side. That shows how much of the shoe was displaced due to the broken and bent brake rigging.

When ever possible, it is always best to match used brake shoes with the same wheels they had been mated with previously. That ensures an excellent fit and the best possible braking. This (below) shows how a good shoe from the new truck fits the same wheel from the new truck after both were installed into one of the old trucks from under 1601.

This, however, brings up an interesting question. The locomotive was originally designed and built with what are called “clasp” brakes. That means there were two brake shoes pressing against a wheel when the brakes were applied. Some time prior to the locomotive coming to the museum, someone removed the clasp brake rigging and modified the locomotive for single brake shoes per wheel. A simple analysis of that change would imply that the braking ability would be reduced by 50%. But we do not actually know if that is the case because braking is also a function of levers and how they apply force. But what we do know is that 1601 has been reported to not have had particularly good braking prior to now. That kind of corresponds to a reduction of braking ability caused by removing half of the brake shoes.

For now, we will operate the locomotive with its original old shoes on the old wheel sets and the matched shoes and wheel sets that were just installed. In addition, we will start to investigate if those cast-iron shoes should have been replaced with modern composite shoes that have about twice the friction as cast iron. If that were the case, then installing composite replacement shoes could possibly return the correct braking ability to the locomotive.

Unfortunately, finding brake shoes for this locomotive may be difficult.

Especially if we want modern composite shoes. This all must be researched.

But for now, we will operate the locomotive with properly fitted cast iron shoes. And there is also the possibility that having brakes that are too good could result in sliding the wheels and causing flat spots if someone applied the brakes too hard. That however, is controllable by adjusting the air brake reducing valve pressure.

The faulty traction motor combos from under 1601, were hoisted onto flat cars for long term storage. The axle journals will be carefully wrapped with thick plumbing tape to ensure that they remain in good shape for a long time. The only problem with these combos is the traction motors. The gear cases and wheel sets are in excellent condition and will be especially important long term in support of 1601 for spare parts.



SF560 is our 1956 Fairbanks Morse H12-44M locomotive. Our effort now, is to attempt to get the Diesel engine operational. If we are successful doing that, then the next step will be to define a total restoration plan.

A lot of progress has been made toward getting the Diesel engine running but Fairbanks Morse parts, tools, and expertise, are expensive and exceedingly difficult to find.

Our main on-going effort is to find and install functional injection pumps. The existing pumps on the locomotive were gummed up and stuck solid. They need to be overhauled or replaced with known functional pumps. We should know more about this in the next couple of weeks. John Salvini prepared the pumps for shipping in case we can arrange for some type of trade or purchase of working pumps.

The injection nozzles for the locomotive are presenting a serious problem. We sent one out to an injection shop for analysis and were told that it did not have a good spray pattern and that it dribbled. What that really means is that the fuel going into the cylinder would still burn but not as efficiently as it would if the injector spray pattern were perfect.

We have also now been told that our injector nozzles are very obsolete and not available from anyone anywhere. Obviously, that is not good news. Our approach will be to design and test a nozzle tester and test them ourselves. If each of them sprays adequately, even with a little dribble, then they will be functional but not perfect. The overhaul manual shows how to refurbish the nozzles but that assumes you have the correct tools. The other major risk is that if a nozzle is accidentally ruined, we have no spares. So, for now, we will test them and use them, almost regardless of how the spray pattern looks.

The Fairbanks Morse engine has a unique air filtering system. It rotates the incoming air, then reverses the direction of that rotating air using small reversing vanes. While it reverses for just a short time, the air actually stops moving for just a fraction of a second and any collected dirt in the air falls downward into a collection chamber. The bottom of that chamber is connected through a long tube to the exhaust stack. At the exhaust stack, a pipe, called an eductor, is installed at an angle so that exhaust from the engine causes a suction that is supposed to vacuum the dirt out from the air cleaners and shoot that dirt up and out the exhaust stack.

That’s great if the system is working correctly. In our case, it wasn’t working as planned. The air cleaners were totally plugged which caused the engine blower to suck exhaust gases backwards through the air cleaners. That meant that oily dirty exhaust fumes were being sucked into the blower. As a result, the air cleaner box and inlet to the blower were full of thick oily dirt. Those areas are supposed to be almost spotless. Apparently, the locomotive ran this way for many years.

As a result, the eduction system, as its called, filled up with burnt carbon chunks that were sucked in from the exhaust stack. During this past week, John Salvini removed the eduction pipes and cleaned them plus some of the inputs to the blower. He removed about 5 gallons of burnt oily carbon. Some of the educator pipes were over 50% plugged.

Of course, most of this problem was caused by plugged air cleaners. Carl had the air filters cleaned at a commercial radiator shop, but they could only clean the outside of the filters. Their caustic solution also cleaned out the oily residue inside of the air cleaner panels but nothing can dissolve pure carbon particles. As a result, all four air cleaner panels came back clean externally but still full of carbon particles. By bumping the panels on concrete and then tipping them back and forth, the carbon bits can be removed to some degree. This next picture shows how bad the problem is. Carl worked over and over loosening and dumping the carbon out from the bottom of the air cleaner collection tank.

We aren’t sure yet if it actually poses a problem. If the exhaust eductor system is working properly, these carbon particles would get vacuumed out into the exhaust stack and be shot upward above the locomotive. We think that’s what will happen but will still try to manually get as much of the carbon out of the air cleaners as possible

Everything about a Fairbanks Morse Diesel engine is unique. The injector nozzles are just as odd as the rest of the parts. We need a way to test cylinder pressures but have no tools to do that with. A normal way to measure compression is to put a pressure gauge in place of an injector and then roll the engine over without starting it.

The cylinder pressure should be somewhere between 150 and 250 psi. Our problem is that we don’t have any spare injectors to modify for a compression gauge. A phone call to a friend in Texas resulted in him sending us an old injector of a slightly different type.But the body is the same so it should work for us. It just needs a little cleaning and some machining.

After a little work, our new compression gauge is ready to use. The spare parts from inside the injector are along side the reworked body. That shows how complex an injector is internally.

Load Bank for Diesel Locomotives

Locomotive Diesel engines were designed to be operated under heavy loads for long periods of time. That meant the engine would get up to full temperature with maximum exhaust flow a lot of the time. That kept the “carbon burned out”, as we used to say. In museum operation, we never get a chance to burn out the carbon. As a result, the carbon can build up in the exhaust system and even in the cylinders. That results in poor operation of the locomotive.

To solve that problem, the locomotive needs a way to be operated under load for long periods of time, but with out going anywhere. That is done by disconnecting the main electrical generator from the traction motors and instead, connecting it to a bank of very heavy-duty resistors. The engine can then be operated under heavy load and the result is a lot of heat that is generated by those resistors.

Those resistors are part of what is called a load bank. It can be built into a locomotive like in our SF108, or it can be a stand-alone device that can be connected to with heavy duty copper cables.

Two cycle engines are especially prone to this problem. Of course, this includes SF560, SF108, SP1006, and UP942. Four cycle engines can also benefit from load bank operation to help keep their exhaust systems clean.

We are in the process of rebuilding a load bank to use with all our locomotives. It will be designed to handle up to 2 million watts of heat which is about 2680 horsepower. At that full load, there will be about 2000 amps of current flowing through the resistors and have about 1000 volts across the load bank which will have approximately ½ an ohm of resistance.

There are 16 resistor grids mounted above the cooling blower motor. Each of those grids’ measures ¼ of an ohm. They will be connected in a series/parallel combination for a total series resistance of ½ an ohm when fully wired.

This project shows the value of scrounging parts for the museum. The resistor grids were removed from a U28 locomotive about 15 years ago, and the load bank carcass was salvaged from Taylor yard when it was closed about ten years ago. Now, the combination for the two can play a particularly important role at the museum.

Dave Althaus

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