NZR RM class (88 seater)

NZR RM class Articulated 88-seater
Blue Streak 88-seater RM 125 at Feilding in 1974
In service	1955 - 1978
Manufacturer	Drewry Car Co, England
Built at	Birmingham Railway Carriage & Wagon Co, Smethwick, UK
Entered service	1955 - 1958
Scrapped	1978
Number built	35
Number in service	0
Number scrapped	33.5
Formation	No 1 end (36 passengers & luggage compartment) articulated over a Jacobs bogie with No 2 end (52 passengers)
Fleet numbers	RM 100 - RM 134
Capacity	88 passengers
Operator(s)	New Zealand Railways
Line(s) served	Many main and branch lines
Specifications
Train length	105 ft (32.00 m) total
Width	8 ft 10 in (2.69 m)
Maximum speed	65 mph (105 km/h)
Weight	63.1 long tons (64.1 t; 70.7 short tons)
Prime mover(s)	Two Fiat 700.040, six cylinder, horizontal underfloor, 1500 rpm naturally aspirated
Power output	420 hp (310 kW) total (original) 370 hp (280 kW) (derated)
Transmission	Wilson 5-speed gearbox (per engine)
UIC classification	Bo–2–Bo
Track gauge	3 ft 6 in (1,067 mm)

The NZR RM class 88-seaters were a class of railcar used in New Zealand, known unofficially as 'Articulateds', 'Twinsets', 'Drewrys' or 'Fiats'. They were purchased to replace steam-hauled provincial passenger trains and mixed trains. New Zealand Government Railways (NZR) classed them RM (Rail Motor), the notation used for all railcars, numbering the 35 sets from RM100 to RM134.

In the early 1950s, New Zealand Railways were in the process of replacing steam traction with diesel and modernising the railways to cope with vastly increased traffic, the after-effects of wartime stringency, and increasing competition from motor vehicles and aeroplanes.

As part of this modernisation process, it was decided to upgrade provincial passenger services, which were provided by a combination of steam-hauled passenger trains that operated several times a week, and "mixed" trains that carried both freight and passengers. An order was placed with the Drewry Car Company in the United Kingdom, which had supplied some smaller diesel shunters previously. They presented a design for an articulated railcar with seating for 88 passengers. The use of horizontal underfloor diesel engines allowed increased passenger capacity and a large parcels/baggage compartment. Fiat 210 hp (160 kW) units were selected.

The design offered the promise of fast intercity and provincial services with high curve speed and were somewhat marginally engineered, with lightweight steel, seats and fittings and everything done to keep down weight, which at about ll tons on the loaded bogies could only support about 1.5 tons of luggage and 20 standing passengers, without stressing and wearing lightweight NZR track. The 88-seaters were constructed by the Birmingham Railway, Carriage and Wagon Company Ltd under contract from Drewry.

The first was delivered in January 1955 and the last in mid 1957. The bogie and running gear design had been closely supervised by NZR CME J.Black and were excellent, and while there was significant sway at speed, it was nowhere as bad as the ugly movement of the older Vulcan and Standard railcars cornering at speed. Unfortunately the design of the power train could not be supervised and while initially in 1955, the Fiat engines were not considered a problem, by early 1957 it was obvious that the Fiat engines were flawed and unsuited to the fast intercity and steeply graded New Zealand routes.