The history of the RM actually follows the pre war cars in both design and concept  via a missing link  often unknown as just pre war the Riley 12hp and 16hp  were introduced as a replacement  for the best selling Adelphi and ended up being the little known transitional car to the RMA hence this article for the magazine. They used the Merlin chassis and initially intended as an upgrade but produced a lumpy  faux Adelphi style saloon  due to a few money saving/standardisation   efforts by the Nuffield group after the takeover. They then  added a totally different beastie as a full Drop Head Coupe    available as a 12hp (1.5) and 16hp (2.5) with tweaked styling from the saloon. This is the only pre war Riley produced in two specific body styles of saloon and coupe. Production  of the both models  ended in 1941 with  few made probably after the  remaining  large parts were used and the model was not revived after the war.

The drop head design had a  starkly different chequered past originating with  the 25HP  Wolseley DHC   design that had been created and constructed as a  Christmas gift for Lord Nuffield and paid for by subscription by the Wolseley workforce. The car  was  presented  to Lord Nuffield in December 1937 with similar cars  later put into limited series production and  approximately 154 Wolseleys being built. (The Wolseley Register knows of just 18 survivors). This design was then transferred to other chassis within the new Nuffield organisation  being diluted from the super six engine and top quality fittings as it dropped down the differing marques. The next financially was the  Tickford bodied MG VA then to  the Riley where up to 100 were built as drop-head coupé (including a few  bare chassis and NKD) hence the ‘not a real Riley ' comments by a certain  Mr A .Farrar.  This became the models death knell with them  being butchered for specials or ignored in passing decades. Sold  initially from early  1939 although it was not  formally announced by The Motor magazine as a new car until July 1939. When war was declared  in September  cars of any marque soon  became available only to certain trades and professions. With only a few bodies  produced prior to the onset of war  the company turned over to 'war work'  meaning only those already constructed could be sold with many of the 12hp  still being sold in 1942 until the war office intervened with requisistioning

The saloon had been  based on the Adelphi  superficially resembling a  Wolseley 12/48 with an  almost upright  Riley radiator shell. However  internally it used a modified version of the "Light Nine"  Merlin  chassis  and  except for gearbox box & the rear axle the rest had already been used by Riley or were the  logical development and included prospective RM internal parts. Visually the car featured  helmet-style front mudguards and a bigger curved boot with a shell body over an ash frame as in the later RM's. Springs were semi-elliptic fore and aft with RM drop links. Brakes were by Girling with the handbrake only on the back. Steering was by bishop cam /bishops peg,  with the steering column adjustable for length. The wheels were changed from the 'knock ons' to  bolt on disc wheels with hubcaps design later re-used in the post war RM's but of smaller size and cheaper pressed steel. The engine was an updated version of the one previously seen in the 1935 Riley 12/4 model but now with a belt driven dynamo. This resulted in them  using Riley parts to construct a car 'more standardised Nuffield' and the design when compared   between these and the RM. Many parts are also common to other Nuffield models are :-Steering box (Bishop peg), back axle (same as MG VA and Wolseley), and front stub axles ( Morris Minor  with mowog cast in to spacer) Gearbox and Radiator core  also have mowog  cast in them. Riley parts  used were the front axle  from the Merlin;  a modified 1935 9hp  ie Merlin wide track  chassis redesigned to take a flat petrol tank plus  inboard flat spare wheel. The 16 hp engine used a Sprite type cross flow and water pump based on the 16hp which resulted in the sales leaflets labelling all as Riley 12 or 16hp Sprites when few had the Sprite eninge . (Those that did are 29SD for a Sprite Drophead and 29SS for the Saloon). The single timing chain used on RM's although meant for this car waited until post war  due to penny pinching. Running board strips replaced mats as in the RM's. Harry Rush had all the parts ready for the finished design of the RM on the earlier wide track chassis except  for the IFS which was left with the shelved design due to WW2 until after 'hostilites' ceased

Both 12 and 16hp models  incorporated a number of non Riley mechanical alterations mainly the Nuffield synchromesh gearbox  with one specific   spring holding the gearstick in place solely for the Riley. (I had some made so yell if needed as driving a few miles in a car luckily stuck in 1st to turn and return was not fun made even worse as the gear stick was on the passenger seat grinning). New 'management'  at Riley responded to the concerns of the marque's buyers  and low sales  by re-introducing the Kestrel 2.5 litre Sports Saloon in updated form, but as the factory was turned over to wartime production this was a short-lived development.

This model  suffered considerably as historically the Register covered cars until 1938 and the RM club from 1945 rendering them on their own with few spares and both clubs often making uninformed derogatory comments. Although designed by Riley as an Adelphi upgrade then adapted  to use some pre-existing spares both from Nuffield and Riley resulting in what is  now one of the rarest models with more Imps surviving than Nuffield 12's and 16's. If nothing else they are the transition between pre war bespoke Rileys that bankrupted the company and mass produced RM's with many common design features. They are now only kept on the road due to the spares produced by the RM club as the other clus do not cover items needed . I purchased mine due to owning EVE570 a 1945/1946 Estate prototype initially including many (broken) 12hp parts so thought it would be a cheaper DHC and super easy. It meant that after rebuilding EVE I had to  use her as a donor engine to offer the parts to the DHC and then buy them from the RM club and eventually sort out the car that at that point nobody had any data on or interest in.

Parts re-used on the RM series:- Hub cap design but sizing different as larger wheels; boot hinges on 1945/1946 cars and some estates; strong similarity to radiator grille and running boards; hood irons as used on the RM Roadster are identical and missing on fakes/specials; back wings as the RM front although similar have a cowl to hold a cheaper Lucas headlamp; torpedo lights of course; D lights as on the very early RM's  as the later ones used split lenses; the 1½ engines are interesting being 85% similar to the postwar RM engine but with a sightly different sump,  particularly with a timing gears instead of a chain.  One anomaly is the UV joint accessible from a removable plate inside the car which means if the plate is left off the shopping and car cushion descend into minced morsels liberally sprayed over the local high street ( I kept driving and disowned them). If buying watch the hot spot tubes as thin wartime steel on this model also if it has the hot spot tube it is a 12/4 . The Sprite option had a different head, twin SU’s and no hot spot tube so another item to check for.One serious problem sorted on the Rm was the idiot decision to use a version of the Bishop Peg steering box which needed to have shims adjusted at the first major service. As on mine it would have been 1943 and the country was busy playing planes not cars it was left until 2022 so did not steer its entire life. The engines  used to turn up in RM cars occasionally, and were a straight swap (thanks to Alec for that info). . . . any more ?

Most   unsold  cars were exported for the services in WW2 as a cheap deal with Nuffield and most being sent to the old ‘colonies’. The DHC  appear in early war reels as staff cars with ribbon coated generals standing and waving. This resulted in many being rendered into a crispy or squashed format and only a handful now surviving. The most mint one survives in Australia. Of the seventy seven known 12hp saloons  exported records  have turned up 11 in Oz ( of the twenty known to have gone there), twelve in India, twenty one in Singapore, nine in S Africa, four in Uraguay (?), eleven in Ireland and Channel Isles plus Europe and one in Thailand . Twenty four were also sent to Oz as NKD or rolling chassis ( different sources state different formats).

In recent years many of those  remaining  have been chopped due to the 'Sprite' description to be turned into a two seater special with the turning skills of a Chieftan tank unless the shims are done. The car then suffered from the same heavy chassis as the RM and stunning build quality ie overengineered,  heavy  vulnerable doors  on the DHC  and lack of a fifth gear. As a missing link a fascinating, comfortable four seater  car and should never ever have been discounted to the point less than a dozen survive of both versions  worldwide

Riley  then introduced the  entirely new  post-war model in September 1945. Announced to the public via the motoring press in August 1945 it was  referred to as the “New Riley Twelve” in 'The Motor '. The engine was internally not much different from that of the pre-war 1½-Litre unit giving 54 bhp and a top speed of 75 mph. The new chassis featured Torsionic IFS with torsion bars. Rear suspension was by semi elliptics with a torque tube axle, and brakes were hydro mechanical.

Many parts due to Nuffield takeover were changed to be common with the Wolsely 12/48 and the  MG VA  hence the ‘not a real Riley comments by Mr A .Farrar. The engine chassis etc are Riley and the body design adapted with a few  cheaper parts. Interestingly I have adverts of the RM advertised as the ‘New 12hp’

Chassis Used ‘Light Nine’  ie a Merlin chassis redesigned to take a flat petrol tank and a  inboard flat spare wheel as in RM’s

Body Style sold  1.6-light saloon  2.2-door drophead coupé  3.chassis only some exported as knockdowns. Most unsold exported for the services in WW2 as a cheap deal hence most being sent to the old ‘colonies’. The most mint one survives in Australia

Body frame Ash  then a a shell body  with a bigger boot. The body has all the panels attached to the chassis and each other NOT the standard loose panels bolted together as in the RM or 12/4

Power 1496 cm3 (Sprite engine £25 extra).  Engine was an updated version of the one previously seen in the 1935 Riley 12/4 model but now with a belt driven dynamo as used as an extra on export 12/4’s from 1937. Fans were added on export cars

Transmission 4 speed synchromesh (except on 1st) and torque tube. Gearbox housing has mowog/Morris  cast in them. UV joint accessible from a removable plate inside the car

Suspension Springs were semi-elliptic fore and aft

Brakes  Girling with the handbrake only on the back (park in gear)

Wheelbase   2,743.2 mm (108 in)   track 1,308.1 mm (51.5 in)

Steering was by Bishop cam/Bishops Peg , the column adjustable for length,  so MG suppliers or change to VW as in MG club data. ***This was again a model weak point as the shims were adjusted at the two year major service GGT was not done (it was due 1943) so steering box had to be rebuilt + adjusted***

Back Axle (same as MG VA and Wolseley)  Rear Drop Arm  flat pressed steel and model specific Buy from Bearings  kit RM club fitted by Keith @ Lunegaards

Front axle was from the Merlin;  a modified 1935 9hp

Front Stub Axles  are Morris (mowog cast in to spacer)

Length 4,343.4 mm (171 in)

Width 1,600.2 mm (63 in)

Kerb Weight (Saloon as Drophead is heavier) 1,219 kg (2,688 lb)… for MOT

Engine 1496 cc  Riley This  used a Sprite type cross flow and water pump based on the 16hp but not the single timing chain as on RM’s.  Engine parts 12/4 Riley Register . Watch the hot spot tubes as thin steel on this model also if it has the hot spot tube = 12/4 . The Sprite option had a different head, twin SU’s and no hot spot tube and many later cars had the Sprite option without the S prefix causing the demise of most of the 12hp cars

1½ engines are very similar to the postwar RM engine but with a sightly different sump, but particularly with a timing gears instead of a chain. They used to turn up in RM cars occasionally, and were a straight swap some are still running in this format

Rockers 12/4      Source  Riley Register  crack if overtightened as wartime metal so a weak point for this model

Sump Gasket 12/4 looks like RM but not quite

Head Gasket  Early pre 1949 RMA Source  RM club

Rocker Gasket  Early pre 1949 RMA Source  RM club The Rocker cover will fit with a bolt hole added for the crossflow tube

Exhaust gaskets RM

Assorted Gaskets   bag RM05A RM club

Cylinder Bore 69mm (2.72in) Pistons common or RM club

Piston Stroke 100mm  (3.94in)

Valvetrain  overhead valves set at 90 degrees operated by twin camshafts (Timing  do with stick for tic or electronically. . .  mark stick and chopsticks work a treat )

Points 0.15 inch  5degrees before TDC

TDC 7/8 to the top of the spark plug OR 1.12mm flush

Fuel  SU carburetter SU HV3  Source Burlen Services Part No: CRK 203 . Others have also fitted HV1 and HV2 so they really were clearing stock and all similar outer design ( I live near Burlen)

Cooling water by pump and thermostat  Early pre 1949 RMA  Source  RM club

Radiator core has mowog/Morris  cast in them. The shell design is specific and pure Riley

Top Water hose = specific so online two parts  with short pipe between to join  https://www.siliconhoses.com/ do not order red as default

Power Output 51 bhp (38 kW; 52 PS) @4800 rpm

Boot Hinges flat not ‘handed’  can be modified  as per pre 1947 RM  use RM club and machine flat

Running board strips replaced mats as in the RM’s yet to discover if RM ones fit

Hood Irons Wilmott Breedon same as the RM Roadster/Drophead and many other cars:-

This although sold as a drop head is in fact a three position  drop head canvas roof as in Bentley, Delage, Wolseley,  and many other 1939 cars. The canvas can be moved to behind the drivers seat and fixed like a Sedanca de Ville . If the rear windows are wound down and the hood irons unlocked the roof will fold back on to the boot/behind the seat ( messy and not as neat as they Lynx etc). The roof unlike other canvas roofed Rileys does not flap and is pretty silent

This part has yet to be achieved properly due to some seized irons

Torpedo Lights RM

Rear lights =  Duolamps  from Paul Beck

Dynamo Brushes etc early RM  RM club

HT cable RM club or ebay single core copper

Points RM club

Petrol Pump SU /Burlen Services change internal filter to brass as way more reliable than the mechanical

Tyres RM size  Black Circles or Longstone   5.75x16

Brakes Girling   Mechanical rod with wedge operated shoes  13" Drums

Known  Nuffield 12 hp Cars  so far :- Check the numbers on the chassis plate:-  June 1939- 29D/or/S 8001-8650? Nuffield 12hp Rileys 1939 onwards; June 1939- 49D/or/K/or/S 1501-1613? Nuffield 16hp Rileys 1939 onwards.  Build figures are 650 known to be sold of the 1939 saloon  no known figures for 1940 so possibly already constructed cars were sold . Also 100 total of Dropheads making a known record of 750 but a caveat recent research has located ones NOT on Vernon's list

**Export data shows 76 saloons,12 dropheads and 24 rolling chassis were exported and on present information many went to 'the commonwealth' as military staff vehicles on a deal between Nuffield and the govt to shift 'old' stock cheaply. Twenty are documented as going to the Royal Australian Air Force alone with the one below surviving in stunning condition** Two dropheads out of fifteen are known  to survive postwar  oddly six survive and are on the list below.

 Harry Rush  (designer ) had all the parts ready for the finished design of the RM on the earlier wide track chassis except  for the IFS which was left with the shelved design due to WW2 until after 'hostilies' ceased ie the IFS although intended for the 12hp was not used.