# Uintah 2-6-6-2 Questions



## Jerry McColgan (Feb 8, 2008)

I've been reading an interesting article by Frolin Marek about the Uintah Railway in the Winter 1994 LGB Telegram Vol. 5, No. 4 page 10. 

While reading it two questions came to mind. 

Frolin mentioned that due to the water leaving the crown sheet dry on a 7 1/2% grade, they added a 2nd steam dome (and lowered the crown sheet) to address the problem. 

Apparently I do not know what a steam dome does because I have no idea how a 2nd steam dome would help. Can anyone tell me how it worked to reduce the problem? 

My second question is about the coal supply of the Uintah 2-6-6-2. 

The loco has huge water tanks on both sides of the boiler yet the coal supply behind the cab seems (to me anyway) to be far too small for the size of the loco. 

Am I missing something? Why so much water and so little coal? 

Thanks, 

Jerry


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## Semper Vaporo (Jan 2, 2008)

The second dome would probably be toward the rear (cab) of the loco. This would allow more water to be put in the boiler to keep water over the crown scheet on a downhill course and not have water up in the steam dome to carry over into the cylinders. I assume this means they may have had two throttles, one in each dome, and only one opened, depending on whether they were going up or down hill. 

As to the amount of water vs the amount of coal...I can only assume that the fuel space is adequate for the distance between refuelling stations and it is better to run out of fuel than to run out of water. Maybe the engine was ineffecient (relatively) in the use of water and thus extra had to be carried.


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## samevans (Jan 3, 2008)

All steam locos use more water than fuel for a given work out. If i remember correctly the Mallets usually worked over the Baxter Pass section only, with fairly large rigid frame locos bringing the trains to either foot of the pass, so a relatively short trip. The work rate going up the pass would have been heavy on water. 

I have to plead ignorance on the two domes question. 

Sam E


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## peter bunce (Dec 29, 2007)

Hi Jerry, 

Water is heavy so it would give the loco extra traction, the grades on the Unitah were somewhat steep, 7.5% and 5%, in addition some of the curves were 60 degrees, so that would be a very useful aid. There was also some both cylindrical, and rectangular water tanks as well, though these may have been used for general transport of water, so possibly the length of the locos was the maximum that could be allowed for. They were designed by the Railway staff. 

A steam dome would allow the steam pipe, which is hidden inside it, which has the throttle or regulator valve there as well, to get steam from the boiler without the addition of water (which would damage the cylinders and can if fact blow the end off them, water being non compressible). 
Water being drawn off and expleed through the blastpipe is 'priming' 

The second steam dome, that was added the front one of the 3, would be to allow for dry(ish) steam to be drawn off, the original (due to the gradients) not doing its job. The crown sheet is the top of the firebox, if that gets dry is will collapse, generally there is also a 'fusible plug (of lead) to allow that to melt first and give warning, and put out the fire. The engineer is likely to also be sacked for negligence! 
The steep gradients and the position of the new steam dome was to get just steam. The three domes were very close together in the center of the boiler, with what looks like two steam domes with a single sand dome betyween them. A the back is a turret for the safety valves etc. 
The line was short at 53 miles long, so they did not require much coal space. 

When the line shut it was reoplaced by a pipeline! 

The locos lived on - on the Sumpter Valley, as tender engines, and then wandered off the South America.


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## silverstatespecialties (Jan 2, 2008)

As it was explained to me a couple of times, steam rises so the easiest way to capture the hottest steam is to place a steam dome on the boiler; then the steam pipe captures this "fresh" steam and takes it to the cylinders for power. 



If this is not entirely correct, someone please smack me upside my head and set the explanation right!


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## Jerry McColgan (Feb 8, 2008)

Thanks guys. I knew you would know the answer to anything. 

Jerry


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## samevans (Jan 3, 2008)

Hottest AND driest, water in the cylinders and valves can have dire consequences. That said I believe the Uintah locos were superheated, ie the 'wet' steam is passed through a form of extra heating before reaching the cylinders, making it even hotter and drier. As a general rule if the loco has piston valves then it is most likely superheated. The cylinder lubricants used in superheated locos are very different from those used in 'saturated' steam locos. Note that the Uintah locos were NOT compounds 

A Slide (D) valve relies on an emulsion of lubricant and water for its lubrication so some wetness in the steam is desirable. If you look at compound mallets the HP cylinders usually have piston valves and the low pressure D valves. The steam is superheated and passes through the HP cylinders but it then looses pressure and temperature resulting in 'wet' steam arriving at the LP cylinders. D valves are better at coping with 'wet' steam. It is possible that some Mallets had reheaters, as do most steam turbine power stations, to dry the steam before it gets to the LP stage, any one know? Water is a BIG no no in a turbine. 

Some compound mallets (usually smaller ones) are all D valve and use only 'wet' (saturated) steam. I believe this is the case with some of the Portuguese metre ga mallets. 


















that .


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## pfdx (Jan 2, 2008)

There is a good description of the problem on the "Unitah Railway" book by Bender (I belive the correct name and author). This is from my somewhat rusty memory. 
The original location of the steam dome, traditionally placed at the mid point of the boiler, caused a serious problem decending the steap grades on baxter pass. When the water level was kept in lower portion of the glass, as is practice, the steam dome was low enough that the water level was in the dome and as the engine used steam is sucked the water up through the throttle and into the cylinders. Known as priming and very bad for the machinery. 
The crews compensated by running the water level lower. later at the shop they measured and discovered that preventing the priming by lowering the water level also uncovered the crownsheet. Even worse for the boiler and crews. 
The ICC became involved and red-tagged the 50, and rightly so, until the solution was found. 
The solution was the addition of the second steam dome at the rear of the barrel, dirrectly in front of the fire box, and relocating the throttle to that dome. this allowed the fireman to maintain a safe waterlevel over the crown sheet, but reducing the effect the grades had on the water level at the throttle. 
51 was delivered from Baldwin with the modifications and never had a problem. 
pd


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## Jerry McColgan (Feb 8, 2008)

I really enjoy reading and learning about the real locomotives and railroads but unfortunately if I bought and read all the books I would like to read I would not have any funds left to buy and build model train layouts. 

I did manage to buy one book lately - "The Dardanelle and Russellville Railroad" (Arkansas) by Clifton E. Hull and Bill Pollard and better yet I was able to buy it direct from Clifton E. Hull. Its a great book. 

My thanks again. 

Jerry


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