Written by: GWR5029
South African Railways ordered a batch of truly outstanding, magnificent and unique locomotives from 2 well known companies between 1953 and 1955, however neither had ever built anything like them before. These magnificent locos were the Class 25 Condensers. Built for the long journey across the Great Karoo between Johannesburg and Cape Town, these engines had massive tenders each with 5 cooling fans to condense steam back into water for reuse on this long and arid stretch.
Following the drying up of water holes in places such as De Aar and Kimberley trials were begun with the converted class 20, 2485. After the trials’ success, L.C. Grubb of SAR designed the Class 25 4-8-4, a loco with a tender 9 feet longer than the engine itself. Henschel built the first prototype class 25, 3451. It was sent off to the North British Locomotive Co. in Glasgow which built the remaining 89 condensers as well as 11 non-condensing variants. Henschel and Son built 60 more tenders, to which they held the patent, each of which bore its own Henschel works plate. Following that, NBL took over building everything, making the last 29 tenders which were delivered with the final 29 engines in 1954. SAR built one last condensing tender on a spare frame at its own Salt River Shops in 1963.
The mighty locomotives and tenders were equipped with a mechanical stoker (6,000 tonnes per hour), oil separator to remove oil from the steam as it was condensed, and the 5 giant fans. The tender held a total of 5,000 gallons. 4,400 of these were kept in tanks between the radiators, and 600 heated gallons (for feedwater) more underneath the condenser’s “belly”. The fans reclaimed up to 90% of water and could do so 8 times. This saving allowed the locos to travel up to 500 miles between refills, and since the water was warmer as it entered the boiler, it drastically reduced coal consumption. These were truly remarkable and modern engines.
The Class 25’s most notable feature however, was it’s turbine whine. Being a condenser there was no exhaust steam to draw up the chimney for draught, so a large fan was mounted in the front of the smokebox (which gave the locos their “banjo” face smokeboxes) which whined louder as the loco accelerated. The locos had a hallow sounding, feeble chuff, which was joined by the whine as the loco worked. These engines truly did sound like an aeroplane getting ready to take off.
Sadly however, particles of char would be drawn into the fan too, chipping its blades and requiring regular maintenance the non-condensing 25 NCs did not require. After an unsuccessful fix of doubling the blades’ thickness (from 7mm to 14mm) was unsuccessful, and more modern diesel and electric traction arrived, all but 3 of the class 25 condensers were rebuilt into 25NC’s. Many of these could still be distinguished by their long “Worshound” tenders, which looked something like giant Vanderbuilt tenders, only much longer, still retaining their massive frame but without the condensing apparatus and tank in middle. After the first conversion, which was the first NBL loco, 3452, was done at De Aar successfully, all but 3 (3511 “Frieda”, 3451 (the first condenser), and 3540 (the last condenser)) were rebuilt at the SAR Salt River Shops in Cape Town. Of these, 3511 “Frieda”, has been the most active, running specials in the 1980s and early 1990s (1992 was the last recorded run). With the Transnet’s “frown” upon steam in the 21st century sadly 3511 has been stilled, but there are rumours of 3511 “Frieda” and 3450 “Red Devil”, a class 26 (originally a 25NC rebuilt with technology that could have fixed the condensers char problems) returning to service.
Yet another factor is that to operate 3511 is said to run like no other, having steam pumps rather than injectors which pump water from the smaller condensate tank and can “trip” if too much pressure is used and have to be reset by a button at the cab bottom. The condensate tank warmed the water first (it was filled from the 4,400 gallon main tank) and condensed through it until eventually it leaked or couldn’t be reused anymore and then it would be filled up again from the main tank. The loco had no safety valves to be heard, they exhausted into the fans which would spin faster, and the water overflowed into the auxiliary tanks and radiators if overfilled. This is a loco that from a firing stand-point is very different, and had just one dark plume when stoking and ran fine provided the fire wasn’t allowed to clinker badly. When she was operating rather than light and dark puffs with the beat of the exhaust it was 1 black plume, which was another problem the class 26 rebuild could have solved. The driver had a different experience too, not being able to base the cutoff on the exhaust, but on the rumble of the pipes to the tender condenser.
This fabulous class of locos would make a wonderful and unique add-on DLC for Train Simulator. Following the announcement of the cape gauge (3ft 6″/42″) SAR Outeniqua Choo Tjoe route , and the fabulous, but currently electric only Cape Gauge KwaZulu-Natal Corridor, the mighty Class 25 would have 2 routes to show its strength, speed, and savings on. The Outeniqua Choo Tjoe was well known for its steam tourist runs, which a preserved Frieda would be right at home on. The KwaZulu-Natal has almost 200 kilometres of route, a condenser would have plenty of time to really get at it, representing the changeover from steam to electric with freight runs in the early 1970s, final steam runs in the 1980s, and special runs with 3511 in the late 1980s and early 1990s, or a hypothetical return to steam in the future if the rumours come true.
This is a fabulous loco which is like no other that I think many would enjoy and I would love to see made, to hopefully draw some attention to the 2 survivors with a future that does not appear as secure as 3511’s. I have seen several people request these beasts in the comments.
Below is a video shot in the late 1980s showing the class 26 rebuilt 3450 “Red Devil” (at the time painted blue for use on “The Blue Train” and then multiple shots of 3511 showing her whine and smoking.