class 24 and 25 detail variations
Detail Differences
More to follow as time permits

Boiler Room Grille
Cab Roofs
Radiator Frost Screens
Fuel/Water Tanks
Battery Isolating Switch Cover

With a production run of 478 Class 24 & 25's it is not surprising to find that there are a number of variations featured on the locomotives. These differences resulted from changing conditions on BR, for example the discontinuance of train identification by lamps & discs, replaced by four digit alpha/numeric headcodes, and the correction of errors found in the early designs, in the case of the BR Type 2's it would be the repositioning of the air filters from the body sides to the cantrail area.

Cab Roof Development (Class 24/25).

This view of 24001 at Doncaster reveals the original roof applied to the Class 24's. This early style was found on D5000 - D5113, later 24001 - 24113.

From a photograph courtesy Tony Sayer.

This aeriel view of 5117 at Kyle of Lochalsh reveals the first change to the cab roof with the addition of a rectangular housing to accomodate the headcode blinds. This style would be carried by D5114 - D5175 (later 24115 - 24150 & 25001 - 25025)

From a photograph courtesy Tony Sayer.

When the horns were moved from their original position near the buffer beam to the location either side of the headcode housing on the cab roof, the roof moulding was modified to accommodate the two horns. D5176 - D5232 & D7568 - D7597 (25026 - 25082 & 25218 - 25247) sported the cab roof with longer sloping flat panels with the horn moulding being slightly below the edge of the sloping flat panel, creating a shadow line, visible in this early view of 7581.
The remainder of the locomotives, D5233 - D5299, D7500 - D7567, D7598 - D7677 (25083 - 25217 & 25248 - 25327) were fitted with a slightly modified cab roof with shorter sloped panels and part of the horn moulding being flush with the sloping roof panel, no visible shadow line, as seen in this view of 25279.

From a photograph courtesy Tony Sayer.

Looking down on the cab roof of 25147 reveals more of the detail of the moulding that incorporated the 'box' to contain the headcode display and the circular mouldings to contain the repositioned horns. Close examination of many photographs reveal minor differences in the roof mouldings, presumably Derby & Darlington had several moulds which were perhaps the source of the minor variations.

From a photograph courtesy Steve Jones.

Close examination of the Class 25 cab roofs indicate there are distinctive differences with regard to the height of the horn moulding and the length of the sloping flat panel coming down from the top of the headcode box and as it ends how it interacts with the curves of the cab roof moulding.

Left to right
25054 Stockport;
25056 Derby Works, October 7th 1979 Graham Turner;
25064 Glasgow Works, February 17th 1978 by Tony Sayer.
Class 25/1 The three views above all show the original type of styling applied to the Class 25/1 roof mouldings. The horn moulding is not flush with the sloping roof at any point, there is a distinct shadow line between the horn molding and the sloping roof moulding. Secondly the sloping flat panel meets the curving roof above the cab windows at a lower point than the later Class 25/2 & Class 25/3 models.

Of course there are always exceptions to the rules. Here is 25072 at Carlisle on July 29th 1985. It should have the same style of cab roof as the three views above, but it does not. Presumably at some point the cab roof has been replaced with a later variant from a Class 25/2 or 25/3 (see images and notes below).
Photograph courtesy Richard Howatt

25108 Glasgow Works, May 13th 1984 Phillip Moore
25119 Doncaster Works, July 13th 1986 Ian Hammond
25192 Derby Works Martin Bray

Class 25/2 & 25/3 Three views above showing the revised cab roof moulding carried on the Class 25/2 and Class 25/3's with certain exceptions. The top of the horn moulding is now flush with the sloping flat panel (there is no shadow line). The sloping flat panel does not extend as far down the roof as in the Class 25/1 variant causing less of a curve in the line created by the change of direction from the side of the headcode box out to the the point where the sloping panel joins the curved roof.

25220 cabs Derby Works, March 18th 1978 Tony Sayer
25226 Doncaster Works, April 27th 1986 Paul Bettany
25246 Glasgow Works, June 5th 1976 Tony Sayer.

Class 25/2 with Class 25/1 cab roof style Although 25218 - 25247 (7568 - 7597) were designated Class 25/2's they carried the cab roof style from the Class 25/1's - see information above. Again there are inconsistancies in this group, close scrutiny of the locomotives coming out of Darlington D7578 - D7597 (25228 - 25247) reveal that both types of the later mouldings were used.

25271 Derby Works, September 29th 1982
25295 Derby Works, August 1979 Martin Bray
Cabs at Derby Works Ian Jenkins.

25271 in the process of scrapping at Derby Works, at some point the cab caught fire, exposing the steelwork that was used to support the cab roof moulding. Also at Derby Works is 25295 which appears to be displaying a very thin shadow line between the top of the horn moulding and the sloping flat panel. And finally five cabs at Derby Works awaiting.............

The above views clearly indicate a distinct cab roof variant between the Class 25/1 and early Class 25/2 builds when compared with the later Class 25/2 and 25/3 builds. Presumably moulds were used to form the cab roofs, very minor differences in these moulds could explain the very thin shadow line on 25295 above, or is it a trick of the light?

Cab Roof Variants.
Outside of the three styles shown above there was only one post-production variation:

An interesting offshoot can be seen here on 24134. This moulding incorporates the later styling found on 5176 (25026) onwards, but does not include the receptacles for the air horns, these were still retained in the buffer beam location for the locomotives that carried this one-off roof.
This style of cab roof was only applied to locomotives within the 5114 - 5175 (24114 - 24150 & 25001 - 25025) series, presumably following accident damage or those suffering from severe corrosion. They were applied only to certain locomotives, frequently at one end only. Locomotives so identified include 24133, 24134, 24147 (both cabs), 24148, 25008, 25009.

This same batch of locomotives can also be found fitted with the cab roof styles carried by 5176 (25026) onwards. Presumably when this occurred the air horns remained at their buffer beam location. Locomotives that carried the later roofs include 24134, 24142, 25006, 25008, 25010, 25015.

Cab Roof/Headcode Oddities.

Whilst not strictly cab roof related, Inverness changed the front panel on the headcode indicator box on their fleet of Class 24's (5114 - 5132). This was probably a winterisation idea to reduce water/snow egress into the cab roof area. Once the use of train identification by headcodes ceased the panels quickly became opaque from layers of dirt!

From a photograph courtesy Tony Sayer.

Not a structural change, but on occasion the headcode panel revealed only the internal light bulbs and dividers.

From a photograph courtesy Steve Jones.

Radiator Frost Screen Variations (Class 24).

The first five Class 24's (5000 - 5004, 24001 - 24005) differed from all the others in regards to the radiator frost screens. In light of the planned livery of the Class 24's, with a waist high stripe along the side, the stripe was to be carried across the frost screen by running a metal band across the panel. As is now well known only 5000 carried this pin-striping, all later Class 24's carried a wider white band at frame level.
Once the split level frost screen was discontinued after 5004 (24004) all following locomotives carried the single piece frost screen. However during overhauls the screens from 5000 - 5004 were occaisonally transferred to other locomotives. At least 24006, 24025 & 24134 ended their days carrying at least one split screen.

Boiler Room Grille (Class 24).

Just under half of the Class 24/25's built carried a steam heating boiler. To ventilate the boiler room mesh grilles were provided on each side of the locomotive, as seen here in this view of 5230. Originally all locomotives received this feature, even for those not equipped with a train heating boiler.

From a photograph courtesy Tony Sayer.

Over time the original mesh grilles were frequently replaced by a solid metal blanking plate, as seen here on 25015.

From a photograph courtesy Tony Sayer.

Boiler Room Grille Variants.

The Inverness allocated locomotives encountered climate conditions that frequently created freezing conditions within the boiler compartment. To reduce entry of cold air a solid blanking plate was later fitted, but modified with five air vents. Seen here are views from 24116, 24117 & 5132.

From photographs courtesy Tony Sayer.

Condition of the ex-Inverness (5114 - 5132) Class 24's at time of withdrawal.

The harsh Highland winters led to the original boiler room grill being covered with a solid blanking plate with either four or five slats to allow a reduced airflow.

Five slat blanking plate: 5114, 24115, 24116, 24117, 24118, 24119, 24121, 5122, 24125, 24126, 24130, 24132

Four slat blanking plate: 24127

Solid blanking plate: 24120, 24124, 24128, 24129

Original style grill: 24123

Glasgow Works modified the roof level water filler access by sheeting it over. This method of filling had become redundant following the dismantling of the platform end water fillers used by the steam locomotives. It would also be one less maintenance headache for the locomotives operating in the harsh Highland winters. Picture evidence suggests this modification began about 1967/1968.

Cantrail water level filler sheeted over: 5114, 24115, 24116, 24117, 24118, 24119, 24120, 24121, 5122, 24123, 24124, 24125, 24126, 24128, 24129 :

Not sheeted over: 24127 & 24130 (as of scrapping?), 24132 (as of Aug 1972)

Boiler Room Grille (Class 25).

With the end of the Class 24 build the production lines at Derby & Darlington moved on to the production of the Class 25's. As they came off the production line there were no external changes to the boiler room grills throughout the entire run of the Class 25s, despite the fact that boilers were not fitted to many of these locomotives!

Over time, and similar to many of the Class 24's, a solid blanking plate was fitted over the grills to minimise the intake of dust and water into the locomotive. At a date unknown Derby Works began removing the grills and sheeting over the opening as the locomotives came through the Works. In some cases the entire panel from the frame level to the roof line was replaced. It is not known when this practice stopped and it appears that it was only carried out at Derby Works.

Three examples of the modification are shown below.

(L) 25161 date unknown - Colln Ian Mawson
(M) 25177 Manchester Victoria - Colln Ian Mawson
(R) 25214 at Swindon - Ian Hammond.

In the above views it appears that 25161 & 25214 have had the whole panel replaced, whilst 25177 has only had the aperture skinned over, the location of the former grill is clearly visible.

Class 25's known to have had the boiler room grill sheeted over - date in brackets indicates modification date (list may be incomplete):

25100, 25101, 25102, 25104, 25105, 25107
25110, 25112, 25114, 25115, 25116, 25118, 25119
25123, 25124, 25126, 25127, 25129
25131, 25132, 25133, 25134, 25136, 25137, 25138, 25139
25141, 25142, 25143, 25146, 25148
25150, 25152 (6/78), 25158
25160, 25161, 25163, 25164, 25166, 25167, 25168, 25169 (1/79)
25170, 25177
25180, 25186, 25187
25211, 25214, 25215
25270, 25274
25280, 25281
25292, 25294

Fuel/Water Tanks (Class 24)

The fuel and water tanks carried by the Class 24's, at first glance appeared to be all the same, in fact they are not. Because these locomotives were over their designed weight when built various changes were made to reduce the weight. These changes included reducing the fuel and water tank capacity, consequently minor design changes took place as the locomotives were built.

All the views immediately below unless otherwise indicated feature the locomotive photographed with the radiator end nearest the camera, the nearest tank to the camera will be the fuel tank.

D5000 - D5049 (24001 - 24049)

The first fifty Class 24's (thirty from Derby & twenty from Crewe) carried the first version of the fuel/water tanks. As can be seen from the views below these, with the batteries gave a solid appearance to the underframe area between the bogies. But because of the locomotives being over their design weight it was necessary to resort to weight saving schemes for the later build, and to take steps for weight saving refinements retroactively for these first fifty machines.

Retro-actively for D5000 - D5049 it was the water tank that was altered by shortening the tank at the end nearest the centerline of the locomotive (see view below of 5025). Not all of the locomotives were retrofitted, at least 24012/16/38/41/42/44/45 carried the full size tanks to the end.

Some tanks gained a circular gauge class usually only on the fuel tank, locomotives so fitted include 5028, 24006/25/34/38/, exceptions include 24046/49 which had the circular gauges on both fuel and water tanks!

Locomotives which had their water tanks removed in this group are 24032/34/35/39.

D5000 early 1960's. This is the original type of tanks installed on the earliest class 24's. Interestingly there is some writing on the fuel tank. There is a sight glass on the end facing the camera.
Photograph collection Transport Treasury.
D5004 early 1960's. Similar to the view above this is taken from the other side of the locomotive. There appear to be no sight glasses on this side.
D5017 June 1960. As delivered from Derby, there appear to be no sight glasses on this view.
Photograph collection Rex Conway.
5025 June 1969. The original water tank has been replaced by one of the smaller capacity tanks and the fuel tank now has a circular gauge on the tank side. This machine is worthy of more photographic study.
D5050 - D5120 (24050 - 24120)

Weight saving measures regarding the fuel tanks went into production beginning with D5050 - where the tank wrapped round the battery box it no longer reached upto the frame level, the modified designed created a shallower end section. This production change affected all the locomotives up to D5120 which included those produced by Crewe, Darlington & Derby.

This batch of locomotives included the Gateshead allocated machines which were later designated for the Tyne Dock - Consett iron ore services - for this their steam heating boilers and water tanks were removed permanently.

Over time some members of this group received the lighter water tank, this was shortened and created a gap between the fuel & water tanks under the battery boxes. Locomotives receiving the lighter tank included 24054/73/76-84/86/87/89/90/92, 24113/118/119.

Other machines saw the circular gauges added to the tanks:
Those with circular gauges on both tanks: 24054/78/80/84/86/99, 24113/115/116/117/120.

Some machines late in their careers had the water tank removed these include 24063/81/86/91.

D5053 new. The fuel tank end section is no longer as tall as the original design. This would be the production standard through D5120.
Photograph collection Rex Conway.
D5096 early 1960's. An example of one of the Darlington built machines, with the smaller fuel tank and original sized water tank.
Photograph collection Rex Conway.
D5117 mid 1960's. One of the Derby built locomotives for the Scottish Region, with the smaller fuel tank.
24076 after withdrawal showing the shortened water tank retrofitted to many of this batch.
24111 after withdrawal, an example showing the water tank removed - 24111 was one of the dedicated Tyne Dock - Consett locomotives.
D5121 - D5150 (24121 - 24150)

In the middle of the Derby build for the Scottish Region the design of the water tank was changed. To reduce its size the length was reduced creating a gap between it and the fuel tank beneath the battery boxes. For the Class 24's, after this third production change there were no others. All changes after this point for the Class 24's were done retro-actively.

Many of this group would later be fitted with circular gauges for both the fuel & water tanks, particularly true for the Scottish examples. Those so treated were 24121/123/124/125/128/129/137/146/148.

Several locomotives only had the circular gauge added to the fuel tank, these included 24126/127/130/132/141. Also in this group were a number of locomotives that had the water tank removed, included in this group is 24134.

D5125 new (taken from boiler room end). Starting from D5121 (I think) Derby switched to a smaller boiler water tank as shown here by the shorter water tank (tank nearest to camera).
Photograph collection Rex Conway.
24128 mid 1970's. The tank sizes are as one might expect, however both tanks have been fitted with circular fuel gauges, which were fitted on boths sides of the tanks.
Photograph courtesy Ian Mawson.
24141 circa 1976. One of the final Derby batch with the smaller versions of the fuel and water tanks. The fuel tank has gained a circular gauge at some point.
Photograph courtesy Ian Mawson.

Battery Isolating Switch Cover.

The battery isolating switch was situated behind a hinged two piece cover midway along the side of the locomotive, close to the handholds that provided access to the cantrail level water filler. The cover remained unchanged throughout the build of the Class 24/25's. In service the lower part of the cover would often appear in the open position, revealing the isolating switch.

Modifications to the access cover to the battery isolating switch were not that common, these changes appear to be mostly the work of the Scottish Region.

24066 awaits scrapping at Doncaster Works. For this locomotive the two piece isolating switch cover has been sheeted over and three small circular covers provide access to the switch area. Presumably these are hinged at the top.
Photograph collection of webmaster.
Class 24's with this modification include 24066, 24071.

Further research shows that this modification was done to the Class 25's, at least 25005 was so treated as seen here at Edge Hill carriage sidings on November 29th 1974. A 1980 view of the locomotive shows the cover has reverted back to its original condition.
Photograph courtesy Tom Sutch.

Class 25's with this modification include 7578 (25228), 25005, 25037 & 25087.

This January 1972 view of 5132 at Inverness shows quite well another modification of the battery isolating covers. In this case the two hinged pieces have been replaced by one access door hinged on the left hand side with a locking mechanism on the right. The footsteps to the roof level water filler have also been plated over, and the footsteps on the rear of the bogie have been removed. Other features shown are the perforated boiler room blanking plate and the tablet catcher.
Photograph courtesy Alisdair Taylor.
Locomotives with this modification include 24119, 24120, 24126, 24128, 24132.

24129 has the modification but is hinged on the opposite side to the above locomotives.

Builders Plates.

Each locomotive carried builders plates, initially fitted to the cabside but later many were moved to the cab door. In later years many locomotives ran without the plates.

Although only a small item there were variations within the styling of the builders plate.

For the Class 25's the plate styles were similar in 1963, 1964 and early 1965, but later in 1965 the 'D' in 'associated' was no longer capitalised.

Temporary Modifications & Experiments.

From time to time locomotives were temporarily modified in order to test a variety of experiments. Many of these experiments were not of a visible nature apart from a small modification plate usually located somewhere near the cab door.

7500 (25150) carried a cab ventilation modification - a ventilation opening the width of the cab door and about 8 inches tall was located above the door in the roof panel, whilst there was a 6.5 inch square aperture cut into the lower part of the cab door. It is not known how long the locomotive ran with this modification.

Page added June 6th 2001
Last updated August 21st 2011

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