.G.N.R. No.279 technical specifications

[DonasterPlant]

I'm sorry if this has already been asked but there are aspects of .G.N.R. Class C1 Atlantic's 1915 rebuild technical specifications that I have found contradictary or no information about for my two research papers. Any help would be appreciated.

Was the increased traction effort 21,260lb or 21,735lb?
What was the heating surfaces of the: firebox, superheater, tubes, and the flues, and the size of the grate area?

[Atlantic 3279]

I'm only offering a thought or two here, so forgive me if these are points that you have already considered and ruled out. The "true" TE figure might not be a matter of "black or white":

1. The discrepancy between those TE figures isn't big enough for it to be a simple matter of one being based on 80% of boiler pressure and the other on 85%.

2. In the days of manual calculation and checking, could the answer depend upon who had worked it out and how carefully the working had been checked? A small variation might for instance arise depending upon whether the area occupied by the piston rod had been subtracted from the area of the piston when calculating the force created by the steam pressure. Unless tail rods were used, the areas would not be the same for fore and aft strokes of the piston. Would the figure for the cylinder bore be taken from the drawings, or based upon what had actually been achieved in the workshop (though these should presumably agree in a loco with new cylinders). You might have to do the calculation yourself in order to start to see what had been done.

I don't remember whether it was said that 279 at that stage had anything other than a standard large boiler, but was it run at the (then) standard pressure, and which superheater was in use? Which sources have you used so far? I only have what I imagine are the typical books but I'll try to check one or more for you if it turns out that I have something that you've not consulted.

[Bill Bedford]

These figures are from RTCS Vol3A taken from the LNER engine diagram.

Firebox.........................140.3 sq.ft
Tubes (156 x 2")..........1305.0 sq.ft
Flues (42 x 4")...............703.0 sq.ft
-------------------------------
Toral evaporative.........2148.3 sq.ft
Superheater
.........(21 x 1.25)............410.0 sq.ft
-------------------------------
Total...........................2558.3 sq.ft
Grate area.......................30.9 sq.ft

Tractive effort .............21,128 lb

[DonasterPlant]

Thankyou Bill Belford for the information. Locomotives of the .L.N.E.R. Volume 3a is probably the only relevant book I haven't been able to find.
So the superheater heating surface= 427sq.ft or, (21x 1.25) 410sq.ft.
Atlantic 3279. Which one of the stated traction effort and surperheater heating surface values should I use in this simple LNER.info style technical specifications table?

From what I have found out it used a second hand 24 element Robinson superheater and the boiler was parrallel.

Below is a list of the twelve sources I have used so far, if you do have anything I have not used could you please tell me as I am trying to included every possible reference source I can so as to create a fully detailed description.
1."British Atlantic Locomotives Revised edition", by Cecil J.Allen and G. Freeman Allen.
2."British Pacific Locomotives", by Cecil J. Allen.
3."Great Northern Locomotive History Volume 3B", by Norman Groves.
4."Great Northern Locomotives, 1847 to 1947", by .R.A.H. Wreight.
5."The Gresley Pacifics, Combined Omnibus, 2nd edition", by .O.S.Nock.
6."Gresley Locomotives, A Pictorial History", by Brian Haresnape.
7."Nigel Gresley, Locomotive Engineer", by .F.A.S. Brown.
8."From Stirling to Gresley, 1882~1922", by .F.A.S. Brown.
9.".L.N.E.R. Locomotive Development", by Jim Armstrong.
10.http://www.lner.info/locos/C/c1.htm
11.ivatt-large-atlantics-t4047.html-st=0&sk=t&sd=a
12.http://www.steamindex.com/locotype/gresloco.htm#C1

[Atlantic 3279]

As Bill points out RCTS 3A gives the TE as 21,128. This appears to me to be precisely the figure given in Groves 3A, and much of the text on No 279 in the two books matches word for word so perhaps Groves wrote all or most of the No 279 section in the RCTS book too!

I'm not competent to do the TE calculation, I merely understand some of the factors that influence it. Unless proven wrong, I believe the RCTS books are usually regarded as the highest authority. I cannot at present think of any books I have other than RCTS3A that do not appear on your list. If not from Groves, from where do your two other TE figures come?

[Pebbles]

In his book - British Steam Horses - George Dow gives a Formula for calculating Tractive Effort for a two cylinder engine as :-
(DxDxSxP) / W = T

D=diameter of cylinder in inches, S=piston stroke in inches, P=85% of maximum boiler pressure in lbs per sq inch, W=diameter of driving wheels in inches, Tractive Effort in lbs.

In the case of three or more cylinders the result has to be accordingly adjusted, I'm syre you will follow.

There are three possible combinations for 279.
79.5 inch wheels (original C2 Wheel diameter) with a boiler pressure of 170 gives 21,266 or 21,892 with a boiler pressure of 175.
80.0 inch wheels give corresponding figures of 21,133 for 170 and 21.755 for 175.

Make of it what you will.

[Bill Bedford]

Thankyou Bill Belford for the information. Locomotives of the .L.N.E.R. Volume 3a is probably the only relevant book I haven't been able to find.
So the superheater heating surface= 427sq.ft or, (21x 1.25) 410sq.ft.
Atlantic 3279. Which one of the stated traction effort and surperheater heating surface values should I use in this simple LNER.info style technical specifications table?

From what I have found out it used a second hand 24 element Robinson superheater and the boiler was parrallel.

Below is a list of the twelve sources I have used so far, if you do have anything I have not used could you please tell me as I am trying to included every possible reference source I can so as to create a fully detailed description.

All the sources you quote are secondary ones. The primary source, i.e. the engine diagrams give a lot more information and, with some caveats, are more likely to be correct. This is the only C1 diagram I have, and it just happens to be for 3279, but after its 1938 rebuild.

[Atlantic 3279]

I fully agree with Bill's point about the books being secondary sources, and the engine diagrams being more like the primary source. I wasn't sure if any C1 diagrams still existed, so did not suggest that you look for them - I'm glad to see that at least one does still exist. Note however that in several places, the carefully researched RCTS books identify points on which the supposedly "known facts" are or were at odds with certain engine diagrams, the latter in some cases never being amended.

[DonasterPlant]

Bill Bedford I have this line diagram of No.279's 1915 rebuild, (from, "The Gresley Pacifics" mentioned above) but the traction effort isn't mentioned.


Atlantic 3279 the other two traction effort values are from: British Atlantic locomotives, "Increased the tractive effort at 85lb% of the working pressure to 21,260lb.- that is, by 38%". and .L.N.E.R. locomotive Development, "and resulted in a 35% increase in tractive effort to 21,735lb".

So the RCTS traction effort= 21,128lb is the correct one?

[Eightpot]

In his book - British Steam Horses - George Dow gives a Formula for calculating Tractive Effort for a two cylinder engine as :-
(DxDxSxP) / W = T

D=diameter of cylinder in inches, S=piston stroke in inches, P=85% of maximum boiler pressure in lbs per sq inch, W=diameter of driving wheels in inches, Tractive Effort in lbs.

In the case of three or more cylinders the result has to be accordingly adjusted, I'm syre you will follow.

There are three possible combinations for 279.
79.5 inch wheels (original C2 Wheel diameter) with a boiler pressure of 170 gives 21,266 or 21,892 with a boiler pressure of 175.
80.0 inch wheels give corresponding figures of 21,133 for 170 and 21.755 for 175.

Make of it what you will.

The 'D x D' part of the formula suggests square bored cylinders - difficult to do without specialised machinery!. My experience is that they are normally round, often worn oversize as well.

How this error has become established as fact in a formula is a mystery when it gives an end result some 30% larger than is possible.

[Bill Bedford]

Bill Bedford I have this line diagram of No.279's 1915 rebuild, (from, "The Gresley Pacifics" mentioned above) but the traction effort isn't mentioned.


Atlantic 3279 the other two traction effort values are from: British Atlantic locomotives, "Increased the tractive effort at 85lb% of the working pressure to 21,260lb.- that is, by 38%". and .L.N.E.R. locomotive Development, "and resulted in a 35% increase in tractive effort to 21,735lb".

That image show that the engine diagram existed when the book was published. It is very likely the diagram book is at the NRM.

So the RCTS traction effort= 21,128lb is the correct one?

Very likely, but a trip to York is will confirm it.

[Atlantic 3279]

Having studied the quoted formula now, taking into account Eighpot's comments, the question of whether one of the quoted figures is "correct" becomes rather amusing to me! Explanatory PMs sent to Eightpot and 'Plant.