7mm US model dabblings

mickoo

Western Thunderer
A dome type throttle (regulator in the UK) is usually gated (limited clearance inside dome) and they can jam or be heavy to operate, there being boiler pressure on one side of the gate, in additional all of the moving parts are inside the boiler making maintenance/lubrication difficult, the throttle rod passes through the inside of the boiler to a gland at the back head (if that gland fails there is no way to isolate it as far as I know) and is connected to the regulator.

The dome throttle uses wet steam from the boiler which then heads to the superheater and then the cylinders, quite a long run so can be slow to respond.

A front end throttle is often of the port type, I don't know of any other types truth be told so there maybe gated ones, all of the linkage is outside of the boiler, easier to maintain, less risk of high pressure glands failing inside the cab. The ports are at the superheater end so the steam is now dry-er and only has a short run to the cylinders, therefore they are quicker to respond.

That's my playmobile/lego way of understanding the two types.

Front end regulators were not common in the UK, primarily I suppose because we didn't build many new classes after the war. Britannia's and Clans had them (as did a handful (five) of Peppercorn's A2's), the rest of the BR classes retained the dome regulator but moved the linkage outside of the boiler. I cannot find any in German steam, even post war Neubauloks but I've not checked every class, just the most likely.
 

michael080

Western Thunderer
I cannot find any in German steam, even post war Neubauloks but I've not checked every class, just the most likely.
German Steam engines usually used "Nassdampfregler" which is the equivalent to "wet steam regulator". As you describe, the regulator and its operating mechanism is inside the pressurized boiler. Reaction is slow because steam will have to pass through the superheater tubes after the regulator was opened.
Most (if not all) "Neubau"-engines that were built after WW2 were actually using "Heissdampfegler" which was located after the super heater. As you write, response is quicker and the mechanism is outside of the boiler, but the disadvantage is that the valve is operated with superheated steam which caused blockage of the regulator because of poor lubrication.
Here is a picture of 01 220. The regulator mechanism enters the smokebox at the red arrow. The superheater block with its regulator is accessible through the cover on top of the smoke box.
Deutsche_Bundesbahn_01_220_heissdampfregler.jpg
(Copyright: Benreis auf wikivoyage shared, CC BY-SA 3.0, File:Deutsche Bundesbahn 01 220.jpg - Wikimedia Commons)

(sorry for posting pictures of German engines in a US-thread)

Michael
 

mickoo

Western Thunderer
That's interesting, I couldn't find that fitting on most Neubau engines, but I can find it on the Nuebaukessel 01 and it appears to be something similar on the 03.10. It also appears in the 41 class but not all engines.

I would have expected it to have been on the 23 class but I cannot find any evidence there, it does appear to be only a select few engines, maybe only those fitted with replacement boilers?

Don't worry about German engines in a US thread, I like both equally as much, it's just that American brass is cheaper to buy than German RTR :))
 

Dog Star

Western Thunderer
Front end regulators were not common in the UK.
Well that is a red rag to a bull kind of statement.

All GWR locomotives with a safety valve on a boiler ring had the regulator in the smokebox so qualify as "front end throttle" designs. Such designs when superheated had the regulator between the main steam pipe and the superheater elements. Lubrication of the regulator was by a heavy oil through an atomiser included in the front face of the regulator cover.

Or have I missed the point of the discussion?

regards, Graham
 

mickoo

Western Thunderer
Well that is a red rag to a bull kind of statement.
Why so much aggression.

Dome less boilers are a different kettle of fish, which includes GWR and those few LMS engines without domes, there will obviously be others but those I'm immediately aware of.

Domeless boilers collect wet steam from the firebox crown and as far as I'm aware, have wet gated regulators at the front of the boiler before it becomes superheated.

When ever and where ever I have seen the phrase or term 'front end throttle' written, it pertains to those engines fitted with valves/ports to control the dry super heated steam, (a frequent term in the UK for the Britannia's, Clans and A2's is 'multi valve regulator') and where the control linkage is outside of the pressure vessel.
 
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Dog Star

Western Thunderer
I have missed or mis-understood, some significant comment in the posts before mine such that my comment above relates to a different boiler considerations.

Mick, please accept my apology for the tongue in cheek way in which I started the post.

regards, Graham
 

mickoo

Western Thunderer
Graham, you have always been economical with your words :p which often leads me to misunderstand :cool:

Moving on.

It's a fair comment/observation, why isn't the dome less boiler considered a front end throttle, technically it is, but then that depends on how you define the technical aspect.

On US engines it's always called a front end throttle when it meets the criteria I mentioned previously, it's in the drawings as such and any technical write ups. It's also called the same in Germany, I wasn't sure last night, but it was only a brief check I did of a select few new build (neubau) engines and couldn't see them. If anyone in Europe would have them then Germany was a sure bet.

I've seen the phrase used occasionally in the UK but usually it's written as multi valve regulator, I suspect if you went to the NRM archives you'd find drawings for multi valve regulators but not front end throttles, conversely if you trawl through the Union Pacific Big Boy, Challenger and FEF engine drawings you find dozens of references to front end throttle but few, if any, mention the phrase regulator.

They are popular in the US from the mid 30's onward, less so elsewhere, perhaps there is a licence issue like there was for Giesel exhausts and the Gresley conjugated valve gear (UP and SP ....actually it was Alco on the railroads behalf but UP and SP officials were involved......I think had some sort of connection from the LNER to fit said valve gear, whether it was legal or fiscal I've yet to determine).
 

mickoo

Western Thunderer
WDYT? Was that linkage added after the factory finish? Is that solder? Or crazed lacquer?
Jason
View attachment 149217
It's a nickel silver etched cover plate and the rods are nickel silver, as are the support posts. The rest of the model (sans running gear and motion) is brass.

IMG_0427-2.jpg

It could well be an aftermarket addition. I don't know how many runs (if more than one) Sunset did with Samhongsa for this particular model or indeed if there were different variants within those production run/s.

They seem to pop up regularly from several sellers so there must be quite a few of them kicking around. As far as I know, none were factory painted and all came as unpainted semi kits to get around US tax import laws.
 

michael080

Western Thunderer
Gentlemen,

it appears there are three type of regulators:
1. traditional style with the assembly inside the pressurised boiler located between the saturated steam compartment and the superheater tubes. Called "Nassdampfregler" in german.
2. front end throttle as in GWR machines which were located in the smoke box in ambient pressure and also upstream of the superheater. Would be also called "Nassdampfregler" in german.
3. front end throttle as in US and some greman engines which are located downstream of the superheater directly in front of the cylindes. German designation "Heissdampfregler".

:) That's what it is like to be a german engineer.

I had some more reading, most older german steam engines that received new boilers after the war (class 1/3/10/18.6/41), but not class 44/45/50/52 had Heissdampfregler that can be identified because they have the same distinct mechanism as above on the US 9000s.
All new built engines in the west had the same regulator. East german new engines had the traditional design. The performance of the new regulators was so poor that most class 23 engines were modified with a Nassdampfregler after some time. This may be why you couldn't find pictures. More info on Die Bundesbahnzeit - Baureihe 23
German language, but a lot of pictures.

And now back to my prussian T18...

Michael
 

Jordan

Mid-Western Thunderer
So, it has to be asked... :oops:
How does a front end throttle work, & what difference or advantage is there to it being fitted?
Now those look like questions from the front of the class!!!!!!!!! Step up Jordan and take a bow.

regards, Graham
The questions might've been worthy of the Front of the Class - attempting to understand the answers has returned me firmly to the Back again. :confused:
It would probably help if I knew more about how a steam loco actually works, of course!! :oops:
 

mickoo

Western Thunderer
The questions might've been worthy of the Front of the Class - attempting to understand the answers has returned me firmly to the Back again. :confused:
It would probably help if I knew more about how a steam loco actually works, of course!! :oops:
Okay, in real basic terms follow the drawing.

It's an LNER A3 with vertical gated regulator within the dome.

Image1.jpg

The regulator gate sits vertically within the dome, the best way to describe the gate is like a wood burner vent, there are slots in the fixed part and slots in the moving plate, when the slots align, steam flows, when they are not, steam doesn't.

On the drawing you can see the bell crank that operates the gate and the rod that travels back to the regulator in the cab. On LNER engines it is a rod that moves backward and forward, on most other engines it is a shaft that rotates, in which case the bell crank is turned 90° and converted to a simple lever arm.

At this point the steam is considered 'wet' as it has a high moisture content and travels down the main stem pipe (red line). If an engine brakes heavily and the water in the boiler is at a high level then there is the risk of water passing through the regulator if it is open, there are often baffles and labyrinths to prevent this but it can happen in some situations. Water inside cylinders is bad news, more on that later.

At the end of the red pipe is the green super heater header, the wet steam enters one chamber here and is diverted down the green tubes which go in and back out of the flues inside the boiler, this drys the steam but also raises it's temperature and thus energy, however some moisture is retained but cannot escape (condensate) due to the high temperature.

Once dried and super heated it flows back to the second chamber in the header and travels down to the cylinders in the blue pipes. As the steam travels down the blue pipes it begins to cool and allow the moisture to potentially escape and eventually you end up with puddles inside the cylinders if left to cool too much. This is what cylinder steam cocks are for, they are opened before setting off and the regulator often cracked open, as hot steam passes through it warms all the pipes up and vents any water or moisture through the bottom of the cylinders.

That's a conventional domed boiler operation in a nut shell, as can be seen once the regulator is opened then the steam has a long way to travel before it does any work in the cylinder.

A front end throttle removes the regulator in the dome and fills the wet pipe and superheaters with steam all the time, this collects in the second chamber inside the superheater header, it is at this point valves are added; sometimes a round shaft with a slot cut in it inside a valve body, sometimes cams with sprung lifting valves and ports like a vehicle engine. The mechanism to drive said valves is all outside of the main pressure vessel.

For domeless boilers like the GWR and LMS then the gated regulator is moved from the red oval to the green/blue oval area. The control mechanism for those boilers does not travel outside the pressure vessel but remains inside like a conventional domed boiler.

Right now I do not know if the domeless gate is in the primary 'wet' (green) superheater chamber or secondary (blue) 'dry' side, my gut feeling is that given it's a transposition from a wet dome area then it will be on the wet side within the superheater, similar mechanism, similar environment, similar lubrication, similar technology etc. GWR and LMS GA drawings seem to show the regulator may not even be a flat gate type but maybe a rotary barrel with slots cut in, I don't know as all my parts drawings are for domed boilers, UK, US, SAR, DB etc. A rotary one would make more mechanical sense being as the control shaft is rotary back inside the cab.
 

michael080

Western Thunderer
perfect description,
only a minor and probably obvious extension. A long rod connects the regulator with a lever on the footplate. The engine driver operates this lever and the valve to control the amount of steam going to the cylinders. Just like the gas pedal in a car.
Michael
 

mickoo

Western Thunderer
Picked this little beauty up from Mr Pat and his cat early doors this morning, he'd held it back for customs duties, I don't mind as he missed the real whopper earlier in the week :eek:

It's a Union Pacific 9C tender (9 for 9000 gallons and C for cylindrical.....imaginative.....not, but it keeps the catalogue simple I suppose) from OMI (Overland). Considering it's possibly near 40 years old it's condition is rather good as is the level of detail.

Only 95 9C tenders were procured for the UP and I think there are some very similar ones for the SP, but, with tenders this small they preferred the whale back (a whole new and bigger can of worms) variety

UP used them on a variety of classes, one being the MK (MacArthur) that I'm interested in. Even with such a small number there are numerous variants, coal fired (hand and stoker...this one is stoker fitted), oil fired and bunker shapes, add the usual swap around's UP did over the years it's a bit of a challenge picking your subject matter.

The recent and much newer, and, I have to say less detailed 3rd rail MK I picked up has one with a sloped coal space, the boxed ones appear to be more commonly converted to oil burners but that's not a given.

From above it's all pretty good but from below it lacks a lot of detail, especially around the trucks and brakes....there being none. I need to check the drawings as I think the trucks are too wide on both the OMI and 3rd rail versions. I may just bin (store safely) them and make new ones up from the drawings for both tenders.

The brass OMI will eventually go behind another MK I'm planning (long term project), like the 9C there are several variants of the MK so again it's a research task to find one with a box coal space tender (preferably an oil burner) and work from there.

IMG_1443.jpg

IMG_1444.jpg

IMG_1446.jpg

IMG_1447.jpg

IMG_1224.jpg
 

Yorkshire Dave

Western Thunderer
Only 95 9C tenders were procured for the UP and I think there are some very similar ones for the SP, but, with tenders this small they preferred the whale back (a whole new and bigger can of worms) variety

SP had similar ones to the UP variety, as well as whaleback (or turtle) as you've alluded to, together with barrel, Vanderbilt or 'Vandy' - which I think was the most common and of course the standard oblong shape tender. Almost all SP variants I've seen have an oil tank instead of the coal hopper.

....and of course not forgetting the DRG, DB and DR with the Wannen tender :D.
 

mickoo

Western Thunderer
SP had similar ones to the UP variety, as well as whaleback (or turtle) as you've alluded to, together with barrel, Vanderbilt or 'Vandy' - which I think was the most common and of course the standard oblong shape tender. Almost all SP variants I've seen have an oil tank instead of the coal hopper.

....and of course not forgetting the DRG, DB and DR with the Wannen tender :D.
Due to the Californian emissions regulations, we often think of them as recent, before WWII then all engines in CA had to be oil fired, ATSF and SP had massive oil burning fleets, UP only converted those engines based in the area, usually with a drop min tank and a reasonably simple burner installation. Outside of CA then coal was preferred and a lot of the SP subsidiary T&NO was coal fired.

I don't think Oregon was mandated as oil burning for emissions but most UP and SP engines were oil burners up there from what I can tell, possibly due to the fire risks in the high dry season. SP had dedicated fire trains with water cannons on the engine and following stock.

I'm not sure of the distinction between barrel and Vandy comes into play, technically the UP 9C and 12C (SP 120C) are vandys but not being built by Vanderbilt are not named as such.
 

Yorkshire Dave

Western Thunderer
'm not sure of the distinction between barrel and Vandy comes into play,

The SP barrel tenders may well have been built by Vanderbilt however those without the square oil tank were referred to as barrel (or sausage) tenders. They were generally, but not always, attached to switchers due to their all round visibility.

Due to the Californian emissions regulations, we often think of them as recent, before WWII then all engines in CA had to be oil fired, ATSF and SP had massive oil burning fleets, UP only converted those engines based in the area, usually with a drop min tank and a reasonably simple burner installation. Outside of CA then coal was preferred and a lot of the SP subsidiary T&NO was coal fired.

Their SSW (Cotton Belt) subsidiary prior to SP ownership was experimenting with oil as a fuel for steam locomotives as early as 1898. Then shortly afterwards became the first south western railroad to use oil as a fuel for all of their steam locomotives.
 
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