To pump or not to pump that is the question

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Re: To pump or not to pump that is the question

Post by gwerhart0800 » Wed Apr 14, 2021 8:01 am

Rich Ulin went all in on injectors for his last engine. Two EEs. I am planning on 2 EEs for my Fitchburg Northern, but it will also have an axle pump. One thing I have seen on full size traction engines that use 2 injectors is one is larger capacity than the other. I don't know if they were trying to save money on a backup injector or if there was some logic to having two different capacities.
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Re: To pump or not to pump that is the question

Post by Bill Shields » Wed Apr 14, 2021 8:30 am

Marty_Knox wrote:
Wed Apr 14, 2021 7:57 am
The usual cause of an Allen axle pump not working is the suction ball stuck to the seat. This usually happens if the locomotive has sat for a while.
which is one reason why many folks (present company included) design the hand pump to push THROUGH the axle pump....
Too many things going on to bother listing them.

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Re: To pump or not to pump that is the question

Post by 10 Wheeler Rob » Wed Apr 14, 2021 9:03 am

If you decide to let a new engineer in training to operate your locomotive an axle pump is nice to have since the operation is much less intimidating than having to learn operation of an injector immediately.


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Re: To pump or not to pump that is the question

Post by Greg_Lewis » Wed Apr 14, 2021 11:05 am

I think it's personal preference. I like axle pumps for their set-it-and-forget-it nature. I don't care to be constantly fiddling with an injector. OTOH some folks like to do that. But if you're not moving, you do need something like an injector or hand pump. And if the fire is just a little high when you're sitting and the safety pops the injector will take care of that.
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Re: To pump or not to pump that is the question

Post by Gra2472 » Wed Apr 14, 2021 11:12 am

These are some great arguments to keep the axle pump. More than I expected. Of course none of the full size locomotives I ran ever had boiler water pumps, so the idea of not having an axle pump does not bother me much. However, there are some great points here. Why disconnect something that works!? That’s a good point. I like the idea of pushing water from the hand pump through the axle pump. That would simplify things, particularly priming the axle pump.
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Re: To pump or not to pump that is the question

Post by tsph6500 » Thu Apr 15, 2021 5:32 am

I too run full-size locomotives beginning around 1999 or 2000 and I still haven't found one with an axle pump bypass valve on the cab floor or tender top. :lol:

I am surprised no one mentioned running their axle pump in the more "prototypical" manner, similar to an injector, of only adding water on the downgrades. I fire just before upgrades so the hard draft gets the green coal well lit while the bypass is open (returning water to the tank). At the summit, I'll give the coal bed a quick rake the break it up. Then on the downhill side I add water to the boiler while the steam production is the highest to keep the safeties from lifting. This way you keep the pressure in that sweet spot about 5 psi below pop-off and a good reserve of water. The demands for steam, coal, and water are not constant unless your track is dead nuts flat so how can you have a constant input of water?

All this "work" keeps the engineer/fireman busy and entertained but my mother did often say I was easily amused. :wink:

On the subject of feedwater pre-heating on live steam models, I've had both and found that the maintenance was a non-issue while any heat recovered from the firebox is a bonus.
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Re: To pump or not to pump that is the question

Post by PeterCraymer » Thu Apr 15, 2021 7:11 am

I did the same as Marty except my bypass valve is in the cab. This eliminates the need for the high pressure line back to the tender. I have a return bend that stick out above the water level so you can always open the hatch for the hand pump and see if the axle pump is pumping. I have found that most of the time that the axle pump will not prime itself. I have the hand pump in the tender plumbed into the same line which may affect that priming, but it also allows me to use the hand pump to actually prime the axle pump. Once primed, it is a great method to keep the boiler topped off for "free". It does rob a fair amount of power and I can feel the cogging action when going up a grade so I usually let it bypass back to the tender when going up.

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Re: To pump or not to pump that is the question

Post by Gra2472 » Thu Apr 15, 2021 10:01 am

That’s another argument that I’ve been considering too. I have also noticed a loss of power when the pump is running. I’ve only used the pump a few times, and that was just for amusement really. I generally rely on the injectors. I can fire hard enough to steam against the injector while running with no problem.

Here’s a story just for fun.

A few years ago I was called off the fireman’s extra board for an excursion train. Typically this is a 2-8-2 and 6 car passenger train. When I climbed up on the engine, the engineer though I was a green horn (I’ve only got 15 years in the seat, still pretty green I guess). He went on to tell me how the locomotive was a dog. She wouldn’t steam and they had to stop at the top of the hill to build water before heading down into town. The regular fireman was riding as my “pilot”. He was a young guy who thought he knew everything. That didn’t last. Before we even left the yard we had a bunch of switching to do, and it was clear that I knew what I was doing.

(I should probably note here that I was already a certified engineer on that railroad, but I hadn’t caught the steam locomotive yet. My regular assignment was on a freight job in Sacramento.)

But she was a big sluggish making steam. Ok, I like a challenge. Come on baby, let’s fight it out. Well the trip was routine until the big hill which is about a mile of 3.5%. She steamed great, and injectors works well the whole time. As any fireman with experience will tell you, you have to plan ahead. About 3 miles out from the grade up the creek to town I was set. We had been drifting down grade and loping along level track for about 16 miles. My boiler wasn’t hot enough for the grade ahead and I knew it. The hogger was off in a daydream.

My fire was a medium spot fire, and I was low on water as I had planned for. I bumped my fire up to big spot fire, like one I use when switching. It’s pretty hot fire, but not blowing the safeties off just yet.

As we cleared the tunnel and approached the hill I had the boiler hot. The hogger was awake and looking my steam and water. He was concerned that I was still a bit low on water but I gave him the highball sign and we went for the hill. At the bottom I gave her one last drink and ramped up my fire to a big running fire. We hit the hill with the safeties sizzling and the water spot on.

The hogger opened up and looked at me. I gave him the “let’s go!” Sign and he smirked and ripped the throttle out by the roots. Halfway up the hill I hadn’t lost a pound, my gun was running and I was building pressure. I signaled to the engineer to turn his gun on. He looked at me like I had just asked for money. “Turn your damn injector on or I will” I shouted across the roaring locomotive. He turned it on, and I cut mine back to meter the water. The firebox door was starting to glow. I cut my fire back as we crested the grade, killed the engineers injector, and roiled into town without a problem.

Not only did we make the hill at speed, we rolled right into the station with half a glass of water and ready to go again. He was shocked and never questioned my firing skill again.

The regular fireman was pissed when he found out that issue was between the seat box and the firing valve, not with the engine.

The next week I caught another run. This time with an 8 car train and a GP7 on the rear as a helper. I had a different engineer this time too. He was aggressive with the locomotive, so we were determined to drag everything with the steam engine. When we got back after a similar, blow the stack off, melt the firebox door kind of trip, the helper engineer came up the cab. I asked how much he was helping up the grade to town. He said “Helping!? Hell, I was just trying to keep up!”

That was fun.

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Re: To pump or not to pump that is the question

Post by James Powell » Thu Apr 15, 2021 10:31 am

From an energy prospective, injectors are better than axle pumps. From a reliability prospective, axle pumps are more reliable (in small sizes here... 3/4" scale...not 1 1/2" scale !).

Pumps were often fitted to UK traction engines, and as I started with them in 1 1/2", that's what we had. The traction had a 11 oz injector, and an engine driven pump. The injector was basically for ornamentation, it worked if you had between about 80-100 psi, and with a rather small water capacity on the boiler, even the 11 oz/min injector was too big really. So, I got good at driving with the pump only...

Later on, with the Hudson, it only had an axle pump- it was unfinished, and didn't have anything fancy like a 2nd way of getting water into the boiler. This leads to the early on practice of making sure one can get water into the boiler before going very far...and before the pressure got high enough to be a huge worry if one had to drop the fire. It was a fair sized pump- we'd run about 4:1 laps without water/with, and keep up just fine. (tender was the 1 gal windshield washer jug on the back of the riding car...strapped there if you were lucky, gravity if not...water came from the pond...). The pump had a bypass, but it was when at TSME, just straight to the ground, not really a bypass. When at COALS for OMLET, we'd add a 2nd hose so that you had enough water for the run.

Robin Hood has hand pump, injector & axle pump. I rely on the axle pump, as the injector is a homemade one that is a bit of a swine at the best of times. For quite considerable periods of time, the hand pump has not been plumbed in, as the pipework on the loco is a bit sharp and tends to break off. (between backhead and drag beam). It's not normally a problem for the testing of the axle pump, as if the boiler is empty like I usually stored it, then you connect the tender, fill it, and go for a stroll with the engine around the track to fill the boiler- way easier than using the hand pump. That tells you that the axle pump is working, and alexander keith's your uncle, away you go. Caribou is similar. I have a new injector on it, but it has been rather less than a steller performer, so axle pump is important.

Again, these are 3/4" models, so much smaller than a 1 1/2".

The 3.75" scale/5" gauge garret here- that's going to have 3 injectors, and no axle pumps. The current outline is 2 EE medium injectors, and a LSM 16 oz (I think it is, it's not the smallest anyway) injector. Intent is to run with the small injector on most of the time, and then if required use the EE injectors to top up.
At work, we had 3 Cofflin CG Steam Turbine pumps, set for 600 HP, and 230 000 lb/hr flow with 600 PSI of boost. They used about 8000 lb/hr of steam to do so. They were supplied via the boost pumps, which worked from 33- ~80 PSI, and were electric driven, from the deairator to the feed pumps. Main Engine Extraction worked from -28.3" or less (condenser) to the 33-38 PSI of the deairator. (as did the TA extraction pumps on the two Turbo-Alternators).

Rated full flow was 214 000 lb/hr (107 000 lb/hr/boiler), but that wasn't something we'd ever hit, we always found one of the other limits first. That was measured using an orifice plate in the water flow to the economizer on each of the boilers, calibrated back against fuel flow at full power on one boiler. The fuel flow was the most accurate that we had, so we'd set steam and water flows backwards against it. ("full" fuel flow = "full" steam flow = "full" water flow). You couldn't beat the fuel flow by much, the boilers would max out at about 7500 lb/hr fuel vs the 7050 lb/hr rated before Lt (Army) Doohan could be heard yelling at the captain :)
And here now, I have 2 electric driven pumps, which are run at 48 Hz (vs 60) because that provides us with enough water for the 600 hp boiler that we normally have in use. I think that they were "supposed" to be run at variable frequency, but someone forgot to include that somewhere, so they run at 48 Hz setpoint which provides all the water we need with minimal bypassing back to the De Airator via the PCV.


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Re: To pump or not to pump that is the question

Post by cbrew » Thu Apr 15, 2021 12:04 pm

pair of injectors is all i have for my water source. been this way for a better part of 18 years, the first two years of steaming, i ran only one. (i had a hand pump in the tender but that is like pissing out the back door with a 8 inch boiler) only had a handful of times I had issues, when that happens, kill the fire if you can not get the issue resolved in a timely manner.
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Re: To pump or not to pump that is the question

Post by LVRR2095 » Thu Apr 15, 2021 12:15 pm

The initial question was whether it was a good idea to REMOVE and already existing and working axle pump.
I still feel that it is not worth the effort to remove it. If you don’t like using it....don’t! It doesn’t hurt anything if you leave it in place. And another thing to consider is the chances are really good that you will not be the last owner of the locomotive. I have in my collection locomotives built between the 1930’s and up through the 1980’s. All of the original builders are long gone. Live steam locomotives if cared for can last for many decades. A future caretaker of that locomotive may well wish to have that pump. I have a locomotive that formerly had a VanBrocklin twin cylinder pump. Prior to my acquisition of the locomotive it was removed to be “serviced.” Well it was never to be seen again. That locomotive is still a great has a tender pump, an axle pump and a temperamental British injector that is totally unreliable. I am really happy that the axle pump is still there!

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Re: To pump or not to pump that is the question

Post by ChipsAhoy » Thu Apr 15, 2021 1:18 pm

Just curious, why would an injector be more efficient than an axle pump? Where is the wasted energy in the axle pump?

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