What's that generator, behind the Pabst engine?

[DMahalko]

Behind the Pabst engine is a machine awaiting rebuilding, and I was having a really hard time figuring out what it is supposed to be used for. There's no signage around it, and so I'm left to making guesses at its operation.

http://i284.photobucket.com/albums/ll9/DMahalko/IMG_0911.jpg

It's got a commutator and a set of four ring brushes, which leads me to believe it's a rotary converter. Four rings tells me it most likely is an old two-phase alternating current machine.

http://i284.photobucket.com/albums/ll9/DMahalko/IMG_0914.jpg

But while most rotary converters were stand-alone with AC making DC or DC making AC, this one has got steam pistons attached to it, so I assume it was a dual purpose generator, producing either two-phase AC or DC, or both at the same time.

The fine wire on the field coils would be high-voltage, low-amp series wound, while the heavy coils are low-voltage, high-amp shunt wound. From my old Hawkins Electrical Guide, I know that these secondary shunt coils can be used to regulate the voltage output without the need for external power controls.

http://i284.photobucket.com/albums/ll9/DMahalko/IMG_0917.jpg

I suppose a person could disassemble the coils and rewrap the wire since they were usually just insulated with cotton thread, but if the metal is brittle they'll crack apart, and reinsulating old wire sounds really difficult. What is the planned rebuild process for these coils? Just rewind them completely with new plastic-insulated wire?


Ah good it has an adjustable brush-gear ring. Just what I need for the Wikipedia commutator article. :thumb:

http://i284.photobucket.com/albums/ll9/DMahalko/IMG_0913.jpg

- Dale Mahalko

[40avery]

Dale,

Someone else will have to fill in technical details on what type of current this unit produced. I only know that it is a generator that was used to produce power at the Shorham Yard shops for the Soo Line Railroad.

It is a compound engine as is the Allis-Chalmers (Pabst) engine.

There is no intention of producing power with either of these units.

[CaseyD]

But that doesn't mean that there is no use for a rebuilt generator! If you have the ability and skills to do so, don't hold back! If you can use some unskilled help, post your need on the forum. I would love to come out and learn how to fix these and help out. Sounds like you know what you are talking about, Dale; you would make a great teacher!

[DMahalko]

Well, I wouldn't want to step on anyone else's plans for rebuilding this machine. Someone had to go through the trouble of getting it to WMSTR, building the concrete foundation it is now sitting on, getting it assembled to the current state, etc.

So perhaps there is already a plan to install new wire on the field and rotor coils, resurface/flatten the commutator, refurbish the brush holders, install new carbon brushes, etc. (Or is the plan to primarily rebuild the steam mechanics side of it and leave the generator hardware as-is?)

I realize these "big iron" rebuilding projects could span many years, and I just do not know what sort of rebuilding plan may already be in the works for this.

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I would like to talk about the potential rebuilding methods, though I am mainly wanting to do this "for informational purposes only" and not to take over from what may be already planned.

- Dale

[CaseyD]

From what I've seen with with dynamos out at Rollag is that the steam engine gets maintenance but the electric parts get left alone. As far as I know, the generators on the Pabst and Villaume engines are in the same condition they were in when they were assembled on site...probably due to a lack of funding or expertise. Luckily, you have the latter resource, all thats left is double-checking with the guys that maintain those engines already to get the background info. No one is going to refuse help! =) Jerry Christiansen would be a good person to network with for this project.

[M Kerkvliet]

From what I've seen with with dynamos out at Rollag is that the steam engine gets maintenance but the electric parts get left alone. As far as I know, the generators on the Pabst and Villaume engines are in the same condition they were in when they were assembled on site...probably due to a lack of funding or expertise. Luckily, you have the latter resource, all thats left is double-checking with the guys that maintain those engines already to get the background info. No one is going to refuse help! =) Jerry Christiansen would be a good person to network with for this project.

The generator in the Villaume building does make electricity. It powers a few rows of incandescent bulbs down the center of the building, for demonstration purposes only.

The reason why they are not hooked into the "grid" is a practicality issue. I am not even certain they generate the correct power for that use, but if they did, and something went wrong, we could cause expensive electronic equipment all over the grounds to go up in smoke... everything from somebody's microwave oven in their camper, to the computers in the ad building! It would also require the operators of said engines to be sure they are run at the correct speed at all times, and the folks firing the Montana boiler to work their tails off firing to provide the steam necessary. We cut back on coal this year because it is $245 / ton!

Then there is the infrastructure (wiring and switching) that would be needed to make the connection! Cost would be insane! The cost to wire the roundhouse ran into 5 figures, and that was very straight forward!

You guys are all missing the point with these displays. They are some very BIG steam engines. Very unique and rare steam engines. We have them running, and are able to demonstrate what they were used for. In my opinion, we don't need to make practical use of the power from the generators for the public to appreciate the exhibit. If someone wants to hook up some light bulbs to the generator, as was done with the Villaume engine, that would be a nice addition to the display, but that is as far as it should go.

[Spencer M]

I agree with Mark. The pabst engine only runs at a fraction of its normal speed, (30 RPM vs 125 rpm) With increased speed comes increased mechanical wear. The steam consumption would be enormous if both engines were running at governing speed, the Montana would have problems keeping up. I feel lucky that we even have these engines put together and moving! The Pabst engine generates 400 somthing volts of AC at 25 hertz, somthing that is difficult to change into our more usable 60 cycle for todays appliances and lightbulbs.

[Jerry Christiansen]

I agree with Mark. The pabst engine only runs at a fraction of its normal speed, (30 RPM vs 125 rpm)

The Pabst engine generates 400 somthing volts of AC at 25 hertz, somthing that is difficult to change into our more usable 60 cycle for todays appliances and lightbulbs.


Spencer,

You have learned the data very well! 480V to be exact. The25Hz would be produced if the engine runs at 125rpm. At 25rpm, 1/5 of goverened speed, the alternator would produce 5Hz electricity. Some guests that know alot more about electricity than I know have told me that we could re-wire so it produces single phase electricity instead of three phase and/or use a different frequency of electricity to excite the altenator we could get 60Hz out.

After all that discussion the decision has been to just keep engine at idle speed as it is. We are more interested in talking with the guests about the engine than producing electricity.

We could look into getting the brush holder in place to help the guests see how the alternator did work.

Later,
Jerry Christiansen

[DMahalko]

I don't think the energy usage would increase too much the Pabst were run at full speed. The alternator is not being excited so it's not producing any power, which reduces the engine load to bearing resistance and air viscosity around the large spinning alternator rotor.

So the Pabst is basically coasting the same as a vehicle engine with the shifter in neutral, and as with a car in neutral you don't need to apply too much more fuel to rev up the engine to cruising speed.

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Steam volume isn't really the issue. It's cylinder pressure vs the work the machine needs to perform. If the load is high and constant then the Corliss has to inject a bigger "dose" of steam to keep it spinning constantly. With minimal load, yes it will take a little more steam to get up to speed but then the governor fall back to nearly where it is right now because there's no load other than the bearings.

To me the real issue would be how well balanced the Pabst rotor is after all these years. If it's gotten somewhat out of balance, you may not notice that when it is running slowly, but it would become more pronounced as it spins up. Any loose wire or parts on the alternator rotor will want to fly off more readily at full speed, and if it's slightly off balance then any unequal concentric gapping between the alternator rotor and the field housing would lead to rubbing, and that would be Bad.

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The Villaume is a different issue because higher RPM means higher operating voltage, and it seems possible that if the alternator coil insulation is not in good shape, the full operating voltage could cause sparking and shorting of the almost century-old wire insulation. So there I can see running it at a low speed to avoid that.

Re-wiring the alternator with brand-new plastic wire would eliminate any concerns about full-speed sparking, but then you lose that "antiquey look" of the old cotton-wrapped wire, soaked in linseed oil and varnish, and baked in an oven:


Example of old-style alternator coil construction, page 1225, Volume 4:
http://books.google.com/books?id=CENWAAAAMAAJ&printsec=titlepage#PPT225,M1

- Dale

[Spencer M]

Dale it seems that you have been to places where they have large stationary steam engines providing power to light buildings.
The engine is equipped with self aligning water cooled main bearings and the crosshead slippers are also water cooled. Neither of these are plumed for cooling there is no need given the slow operating speed.

Thanks for the link dale I've scrolled through it and I think I figured out how to make my antique dynamo/alternator science display work.

[DMahalko]

Heh, I do understand that the main goal for the Big Iron is preservation and not full operation. Keeping stuff moving slowly with lubrication will preserve it far better than letting it sit idle, and there's much less risk of damage with a slow speed that just ticks it over rather than rated speed.

I'm just talking about the practical issues of achieving full speed operation. Obviously that is not anyone's goal, but we can talk about theoreticals, can't we? :)

- Dale

[M Kirschenman]

For what its worth, we've run the Murray Corliss in the Freeport building at full speed (100 rpm) - The cutoff barely increased, of course there was no load. I think she actually ran smoother than the 50rpm we usually run at. Also, the guys at the Menno SD show, that have another Murray Corliss, also like to periodically open up their engine - same thing, it spins like a sewing machine, only less vibration.

An important point to keep in mind is that any machine with solid, liquid lubricated bearings (which is about everything on the grounds) operates on the principle of hydrodynamic lubrication. This is a $50 term for the idea that the shearing pressure of the oil creates a pressurized oil film that actually suspends the shaft above the bearing, eliminating metal to metal contact. This oil film thickness is proportional to speed (and load); the higher the speed, the thicker the film (too a point, and it is not a linear relationship).

Engineers knew, understood, and designed for this over 100 years ago (Osborne Reynolds described it in 1883).

My point is that it’s the starring and stopping (and overloading) that wears bearings, not continuous running. Also, since speed controls oil film thickness, excessively slow speed can be harder on a bearing than a faster speed.

-MK

[M Kerkvliet]

I know most of you reading this understand what I was saying here...

It would also require the operators of said engines to be sure they are run at the correct speed at all times, and the folks firing the Montana boiler to work their tails off firing to provide the steam necessary. We cut back on coal this year because it is $245 / ton!

But for those who may not... a steam engine running at governed speed (much faster than we run the stationaries mentioned in this thread) will not take any appreciable more steam than they do idling along like they do, but IF we were to load them, i.e. put a big electrical load on the generators, then they would take a lot more steam, (hard work and fuel) to fire the boilers. My point was to the load of the engine, not the speed.

I would like to see the engines running full speed sometime. I wonder if it could be part of a demonstration that is done a few times a day, on schedule. I would sure make it over to see that!

[CaseyD]

I'm glad I 'sparked' this conversation, but the intentions of my last message were not to wire the generators into the showgrounds. What I meant was that if someone knows how to fix something, that piece of machinery will better off once its fixed up, even if there is no intentions of putting it back to 100% mainline service. I was taught by people much wiser than me that if you are going to spend the time to fix something, you should try to finish the job completely. I'm sure a lot of 2-cyl John Deere guys agree with that mindset to some degree--just because they spent $2,000 for engine rebuild, not many intend to work the tractor 10 hours a day like the owners did in 1945. Besides the loss antiquity, which is valuable, I don't see any disadvantage of having a completely restored generator belted up to the completely restored steam engine! =)

[DMahalko]

Just as with the rebuilt steam engines, I would not expect full service operation out of a rebuilt/rewired motor or generator, because the old equipment is nowhere near as efficient as modern technology and it is not fully automated.

Real-time operating power for Things That Matter like office computers and outdoor lighting would practically require a boiler/stoker with automatic fuel feed, automatic flue regulation, automatic this and that with safety systems all over the place. I don't think that is anyone's interest to pursue.

An electric machine rebuilt with modern PVC insulated wire is going to be a lot more reliable than a machine with century old cracking and rotting wire, and it will handle full-voltage operation without any worries, but there is no need to run it at the fully rated wattage input or output.

Rebuilding that Soo Line rotary converter so it can supply two-phase AC or high-voltage DC for other demonstration electric machines would not create much boiler load, if the devices it is driving are also just coasting.

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Heh, I wanted to talk about the potential rebuilding process for the electric machine that started this thread but at this point I should probably start a new thread. ;)

http://img239.imageshack.us/img239/6253/ridingsunkualalumpurtrary7.jpg

- Dale