New member, old train fan.
What purpose do the domes on a steam engine serve? I know one is for sand but all the pictures of steam engines I've seen display at least two and sometimes three domes.
D. Bernie
The most important dome on the steam engine is the steam dome. That is the location in the boiler where the steam is collected and distributed to use points on the engine. It is the highest location on the boiler for that reason. Generally the steam dome components include the throttle, the safety valves, and the whistle. The whistle is generally visible but the other components may be hidden. Some locomotives used 2 steam domes and some locomotives used 2 sand domes. So the 3rd dome you have seen could be either.
dd
Also, the steam dome will be as close to the front-to-back center of the boiler as possible, measured from the back of the smokebox to the backhead. This is to minimize the possibility of spashing water into the throttle valve when going up or down hill.
"Also, the steam dome will be as close to the front-to-back center of the boiler as possible, measured from the back of the smokebox to the backhead."
False. Just take a look at different locomotives of different roads and you will clearly see that this is not true. BTW, the NYC Niagara has no steam dome!
.
Steam dome location depends on the configuration of the boiler and the designed engine applications. For example, the classic position of the steam dome on the 4-4-0 with a stepped boiler is directly above the firebox portion of the boiler.
BigJim wrote: "Also, the steam dome will be as close to the front-to-back center of the boiler as possible, measured from the back of the smokebox to the backhead."False. Just take a look at different locomotives of different roads and you will clearly see that this is not true. BTW, the NYC Niagara has no steam dome!
did the Niagara's use a perforated dry pipe?......most English engines are domeless for this reason....i think
Yes J.E. That's the way it worked.
Let's see one.
not the best shot....but notice the large sand dome mid-boiler and the large turrent area ahead of the cab for appliance steam supply
Not to be short with you, but, just go to the the library. You may accidentally learn something. Here just one (of many) hint, Berkshire.
From "The Illustrated Encyclopedia of North American Locomotives" by Brian Hollingsworth; Entry concerning the Niagara Class 4-8-4:
The American Locomotive Company at Schenectady, proposed what was to be the last really new design of passenger locomotive to be produced in the USA. It owed something to the Union Pacific's "800" Class; dimensionally the two designs were very close, and in addition, the design of the 14-wheel centipede tender was certainly based on the UP one. The NYC engines had something else unusual for America, in common with the "800's", a smooth and uncluttered appearance, but with no false streamlining or air-smoothing.
Because the NYC structure gauge allowed rolling stock to be 15 ft 2 in tall instead of 16 ft 2 in as on the UP, the smokestack had to be vestigial, and the dome little but a manhole cover.
End quote
The dome, burried for clearance, but still there, and just about where I said it should be.
"BTW, the NYC Niagara has no steam dome"
What seems to be the problem Tom?
Have you found those numerous other steam domes that don't happen to be where you said they were?
BigJim wrote: "BTW, the NYC Niagara has no steam dome"What seems to be the problem Tom?Have you found those numerous other steam domes that don't happen to be where you said they were?
So, what is that thing in the top center of your diagram that looks like a manhole cover?
Since you like drawings, let's look at a side view of the locomotive in question, without being a low angle:
Note at the top center of the boiler, at the high spot there is (surprisingly) something that looks like a manhole cover, just as described in my earlier post.
To answer your other question, every steam locomotive that I've worked on (the real ones), had a steam dome, or whatever you want to call the high spot that the dry pipe collects the steam for the cylinders.
I'll add to this discussion, I helped restore NKP 765 and have been inside its boiler.
I was suprised as others here maybe, the main steam pickup is at the firebox end, just a pipe with an angled fitting pointed up. Why? The steam is drier and hotter at this point. The berk had the steam dome but whistle and fittings only. From there the steam went thru the superheaters then to the pistons. As long as the fireman kept the water level right, there wouldnt be splashing.
BTW most steamers had an insulated covering shell, you could easily disguise a dome, but steamers could get along without a dome, more a matter of design.
and BTW, the squarelike box at the front of the berk on the smokebox is a cover where the superheaters are supported and the distributor of the steam is.
TomDiehl wrote: BigJim wrote: "BTW, the NYC Niagara has no steam dome"What seems to be the problem Tom?Have you found those numerous other steam domes that don't happen to be where you said they were?So, what is that thing in the top center of your diagram that looks like a manhole cover?
looking between the drawing and full pic, theres something that might be an access cover, prolly at the "manhole" spot. If true that would make getting into the boiler a snap without removing the shrouding. That puts the steam intake about the middle.
Actually Tom, you didn't answer my other question. The one that got this whole thing started. I was asking if you found the picture of the steam engines that didn't have their steam dome half way between the front of the engine and the cab. Remember that I gave you a clue where to start your quest?
You have confused the second part of my original post to go with the first part. The NYC part was just some additional information for those who didn't know that the Niagara didn't have a steam dome.
Quick touchstone for identifying a sand dome - it will have a quick-lift hatch or two (or four) where the sand is delivered. The latch will be simple - it doesn't have to contain steam pressure.
If a locomotive has three domes and there is a whistle mounted on the center one, it's a safe bet that the other two are sand domes. However, a lot of Santa Fe locos had two sand domes forward - easily spotted as such by the presence of the aforementioned hatches. (If your railroad stands on end, you use a lot of sand for traction.)
The exact location of certain fittings was frequently driven by aesthetics or clearance issues. The Niagara's whistle was mounted in a horizontal position to the (engineer's) right of the stack, its turbogenerator was mounted alongside the ashpan and the bell was under the pilot. The safety valves were mounted in a hole in the boiler top (an inside-out steam dome,) slanted inward at a 45 degree angle to minimize vertical clearance. The N&W J class hid the turbogenerator under the running board behind a valance, and put the bell under the pilot like the Niagara's, but the purpose was to avoid breaks in the streamlining.
Chuck
The N&W J class hid the turbogenerator under the running board behind a valance, and put the bell under the pilot like the Niagara's, but the purpose was to avoid breaks in the streamlining.
Chuck, The bell on the N&W Class J was originally mounted on top hidden by the streamlining. There was plenty of room up there to hide the dynamo, however, I suspect that it was mounted low for ease of maintenance. If you can find a very late picture of the J's, you will find that most of the upper cowling has been cut away for ease of maintenance. BTW, on the only recording that I have of a NYC Niagara, I was most disappointed to hear that when the loco approached a road crossing, instead of blowing a "Whistle" it blew of all things a lousy "Horn"! Yuck!
BigJim wrote: To answer your other question, every steam locomotive that I've worked on (the real ones), had a steam dome, or whatever you want to call the high spot that the dry pipe collects the steam for the cylinders.Actually Tom, you didn't answer my other question. The one that got this whole thing started. I was asking if you found the picture of the steam engines that didn't have their steam dome half way between the front of the engine and the cab. Remember that I gave you a clue where to start your quest?You have confused the second part of my original post to go with the first part. The NYC part was just some additional information for those who didn't know that the Niagara didn't have a steam dome.
Your clue of where to start was the NYC Niagara that supposedly had no steam dome, and that was refutted, it has a low profile dome, for clearance purposes, at the top center of the boiler.
You're also the one that decided my original statement was an absolute. If you go back in history far enough, steam locomotives had upright boilers, which required no dome because the top of the boiler was small enough. When you lay the boiler on its side, you bring in a whole different set of design and operation considerations, far beyond the scope of this forum.
A steam dome may or may not have a whistle attached. On modern steam locos, safety valves are almost always mounted directly on the boiler, not the steam dome. The position of a steam dome can vary.
Examples of forward position about 5-6 ft from front tube sheet:
NKP, PM, W&LE 2-8-4s
C&O T1 2-10-4s
C&O first 4-8-4s
There are others
Examples of perforated dry pipe, no steam dome:
NYC 4-8-4s
some CP 4-6-2s, 4-6-4s, 4-4-4s
All the necessary information to resolve this discussion can be found in various locomotive cyclopedias. Big Jim posted an example earlier in this thread. The internal arrangement of the steam dome and its ell-shaped entry pipe or the perf dry pipe are usually shown in the assembly drawings for the locomotive (overall side elevation and various cross sections).
We need to look no further than Ohio Central to find current examples of all three general configurations:
Conventional, approximately mid-point - GTW 4-8-4 6325
Forward - soon to arrive NKP 2-8-4 763 and nearby 765
Perforated dry pipe, CP 4-6-2 1293
The Niagara rendering in Brian Hollingworth's book doesn't prove anything. The Niagara drawing posted above tells the entire story - The Niagara has no steam dome. It has an access hatch back of the dry pipe. This general arrangement is repeated for the CP 4-6-2s and 4-6-4s based on the 1941 Locomotive Cyclopedia I have here.
Railroads had different preferences and their designs reflected this.
feltonhill, Please drop me an e-mail, I had a bad crash and lost your address.
Tom, You obviously can't read words or drawings.
BigJim wrote: feltonhill, Please drop me an e-mail, I had a bad crash and lost your address.Your clue of where to start was the NYC Niagara that supposedly had no steam dome, and that was refutted, it has a low profile dome, for clearance purposes, at the top center of the boiler.Tom, You obviously can't read words or drawings.
I can read drawings just fine. If you're talking about the words that titled the drawing as "domeless," remember this is also the era that gave us "smokeless coal."
Tom,
the thing atop the boiler you are referring to is NOT a dome. It is nothing more than the seat (actually an angeled plate) for 4 safety valves. The function of a steam dome is to "provide" the driest possible steam to the throttle, a dry pipe as used on the Niagaras did that job equally well that one could avoid the dome. In the case of the Niagaras only clearence problems were the issue, because without the steam dome the boiler could move higher and get a larger diameter - thus more volume for more power.
VAPEURCHAPELON wrote: Tom,the thing atop the boiler you are referring to is NOT a dome. It is nothing more than the seat (actually an angeled plate) for 4 safety valves. The function of a steam dome is to "provide" the driest possible steam to the throttle, a dry pipe as used on the Niagaras did that job equally well that one could avoid the dome. In the case of the Niagaras only clearence problems were the issue, because without the steam dome the boiler could move higher and get a larger diameter - thus more volume for more power.
The drawing posted shows a raised portion of the boiler where the end of the dry pipe is, covered by an access plate. A steam dome is simply this, and if you've ever seen a traditional one with the sheet metal cover removed, they also have the same type cover plate. Design of steam domes, like the rest of the locomotive, varied widely over the years in all dimensions. You can call this "domeless" or a "low profile dome," although "domeless" has a better PR ring to it, it follows the basic design and performs the same basic function.
Our community is FREE to join. To participate you must either login or register for an account.