Caledonian Railway 721 Class

Caledonian Railway 721 Class
"Dunalastair"
For variations see Table 1 below
Type and origin
Power type Steam
Designer John F. McIntosh
Builder St. Rollox railway works
Build date 1896
Total produced 15
Specifications
Configuration 4-4-0
Gauge 4 ft 8 1⁄2 in (1,435 mm)
Driver diameter 6 ft 6 in (1.98 m)
Locomotive weight 47 long tons (48 t)
Boiler pressure 160 psi (1,100 kPa)
Cylinders Two, inside
Cylinder size 18.25 in × 26 in (464 mm × 660 mm)
Valve gear Stephenson
Valve type Slide valves
Performance figures
Tractive effort 15,100 lbf (67 kN)
Career
Operator(s) CR • LMS • British Railways
Class CR: 721
Power class LMS: 2P
Withdrawn 1930–35
Disposition all scrapped

The Caledonian Railway 721 Class (known as the "Dunalastair" class) was a class of 4-4-0 steam locomotives designed by John F. McIntosh for the Caledonian Railway (CR) and introduced in 1896.[1] All survived to be absorbed by the London, Midland and Scottish Railway (LMS) in 1923 and a few survived into British Railways (BR) ownership in 1948.

Development

The "Dunalastair" class was very successful and developed in four different versions:[2]

The rebuilding with superheaters was accompanied by a reduction in boiler pressure and an increase in cylinder diameter.

There are two further classes of McIntosh 4-4-0 locomotives which some authors have included in the Dunalastair series. These are:

Classes 766 and 900 were built with eight-wheel bogie tenders with capacities for 4,125 imperial gallons (18,750 l) of water and 4.5 tons of coal. In the 1930s newer and more powerful LMS locomotives took over their most long-distance duties and the company cascaded the 900 Class to other work. This made eight-wheel tenders superfluous so the company substituted smaller, lighter and simpler six-wheel tenders from scrapped Caledonian locomotives. Most members of the class received McIntosh tenders that had been built for classes 179, 600, 908 and 918. The six-wheel tenders had the same 4.5 ton coal capacity but carried only 3,570 imperial gallons (16,200 l) of water.[3]

Accidents and incidents

Dimensions

Table 1
Class Weight Boiler
pressure		 Cylinders Driving
wheels		 Tractive
effort		 LMS
power
class
Dunalastair I 47 tons 160 psi 18.25" × 26" 6' 6" 15,100 lbf 2P
Dunalastair II 49 tons 175 psi 19" × 26" 6' 6" 17,900 lbf 2P
Dunalastair III 51.7 tons 180 psi 19" × 26" 6' 6" 18,411 lbf 2P
Dunalastair IV 56.5 tons 180 psi 19" × 26" 6' 6" 18,411 lbf 2P
Rebuilt II 52 tons 170 psi 19.5" × 26" 6' 6" 18,315 lbf 3P
Rebuilt III 54.5 tons 170 psi 19.5" × 26" 6' 6" 18,315 lbf 3P
Rebuilt IV 56.5 tons 170 psi 20.25" × 26" 6' 6" 19,751 lbf 3P
139 and 43 59 tons 170 psi 20.25" × 26" 6' 6" 19,751 lbf 3P

Numbering

Table 2
Class CR no. LMS no. BR no.
(Note 1)		 Withdrawal
dates
Dunalastair I 721–735 14311–14325 – 1930–35
Dunalastair II 766–780 14326–14336 – 1936–47
Dunalastair III 900–902, 887–899 14337–14348 – 1932–47
Dunalastair IV 140–150, 923–927, 137, 138, 136 14349–14365 54363 1937–48
Rebuilt II various 14430–14433 – 1935–37
Rebuilt III various 14434–14437 54434 1928–48
Rebuilt IV various 14438–14439 54438–54439 1955–58
139 Class 139, 132–135, 117–122 14440–14449 54440–54449 1915–57 (2)
43 Class 43–48, 39–42, 123 14450–14460 54450–54460 1954–57

The 139 Class and 43 Class are included in the Dunalastair series by some authors. Some locomotives survived into British Railways (BR) ownership in 1948.[7][8][9][10]

Notes

  1. BR renumbered the engines by adding 40000 to the LMS numbers. The BR number series are not continuous because some engines were withdrawn before 1948.
  2. CR number 121 was withdrawn in 1915 after the Quintinshill disaster so did not receive an LMS number.

Belgian derivatives

SNCB-NMBS Class 16

Belgian State Railways (SNCB-NMBS) derived six series of steam locs (424 units) from the Dunalastair design between 1899 and 1913:[11]

Two of them are preserved in cosmetic state by SNCB: tender locomotive 16.042 and express locomotive 18.051.

Withdrawal

The first Dunalastair to be withdrawn from service, other than for accident damage, was 14343 in 1933. The reason for its withdrawal is unclear. The next withdrawal was not until 1937. By 1944 only five members of the 900 Class remained. The last 900 Class survivor received the British Railways number 54434 and was based at Aviemore until it was withdrawn in 1948.[12]

See also

References

  1. ↑ "Caledonian Railway locomotives". Steamindex.com. Retrieved 20 June 2012.
  2. ↑ Casserley & Johnston 1966, pp. 138–144.
  3. ↑ Smellie, p. 9.
  4. ↑ Nock & Cooper 1966, pp. 88–90, 92.
  5. ↑ Earnshaw 1991, p. 21.
  6. ↑ Smellie, p. 4.
  7. ↑ "Dunalastair IV". Steam Loco Class Information. Rail UK. Retrieved 21 June 2012.
  8. ↑ "Dunalastair III". Steam Loco Class Information. Rail UK. Retrieved 21 June 2012.
  9. ↑ "Superheated Dunalastair IV". Steam Loco Class Information. Rail UK. Retrieved 21 June 2012.
  10. ↑ Baxter & Baxter 1984, pp. 85–87.
  11. ↑ 4-4-0 Dunalastairs in Belgium
  12. ↑ Smellie, p. 5.

Sources and further reading

External links