Ariel Singles 1945 to 1958

As the 2nd World War came to an end, Ariel was so desperate to establish its position once again as a leading maker of affordable civilian transport that it didn't see the need to delay the resurrection by creating any new offerings. The first post-war models were pretty much the same as the pre-war models except that the smallest model, the 250cc Hunter, was dropped.

The range comprised five models: the basic “Deluxe” 350cc and 500cc bikes (designated NG and VG, respectively) and the slightly more sporty, and slightly more expensive, 350cc and 500cc “Red Hunter” (designated NH and VH). To complete the set, the 600cc side-valve VB. All had rigid frames and girder forks, exactly like the pre-war range. The retention of the rather archaic VB model was to appeal to sidecar drivers who were happy to trade a bit of top-end performance for ample low-end torque.

The mechanical differences between the Deluxe models and the Red Hunters were not great. The Red Hunters had a slightly higher compression ratio and steel flywheels, rather than iron, to make them more resilient to sustained hard use. The basic design of all of the OHV engines was much the same and had remained largely unchanged for many years. There were also some differences in the frames and bodywork, which were strangely inconsistent. The use of valanced or non-valanced mudguards and lozenge or cylindrical shaped silencers varied between models, to create the appearance of differentiation between the models. There were also some options available to the customer to choose between single-port and dual-port heads and high-level and low-level exhaust systems.

The frames all had a single front down tube and the same dimensions in all cases except that the basic (Deluxe) 350 used the frame from the war-time military model., which had more ground clearance and less height between the top and bottom of the frame. That is why the 500cc engine can't be fitted to a Deluxe 350 or WN/G frame. In effect, the post-war NG was a civilianised version of the military bike, probably to use up a stock of military frames.

All of the singles had the same bottom-end, comprising a pair of heavy disc flywheels with a roller big-end between them and a short shaft on each side, supported in the crank-case by ball and roller races. The configuration of the main bearing races differed slightly between models but they all had a single bearing on the timing side and double bearings on the drive side.

Primary drive was via a face-cam type spring loaded shock absorber and employed a single-width primary chain, connecting the crank to a sprocket bolted to the outer basket of the dry clutch. Ariel's unique design of primary chaincase allowed the primary chain to run in an enclosed oil bath while the clutch ran dry in a separate compartment with a domed inspection cover. The oil seals between the clutch compartment and the oil bath and between the oil bath and the outside world were not 100% effective and some oil leakage was normal. Ariels had this in common with many of its competitors of the time. Also in common with a number of its competitors, all Ariel models used Burman gearboxes. The 350s used the CP gearbox and the others used the BA gearbox.

All of the singles used a reciprocating piston-type oil pump to provide lubrication to the main bearings and to the bigend. The lubrication system was based on the dry sump principal so the pump had two separate pistons, operated by the same eccentric pin on the end of the cam shaft. One piston delivered oil to the bearings in the bottom end and the other, slightly larger diameter piston scavenged the spent oil from the bottom of the sump and returned it to the oil tank. The piston and bores were lubricated by the oil shed from the bigend bearing. The oil passed from the pump to the timing-side main bearing and through drillings in the crankshaft to the bigend bearing and then to the drive-side main bearing races before draining into the bottom of the crankcase.

On the OHV models, the valve gear was lubricated via a thin external tube T'd off the oil return pipe, which gave a low-pressure feed to avoid over-oiling around the valve guides. This gave rise to one of the singles' less attractive features. The camshaft and cam followers were lubricated by gravity feed as the oil descended down the push rod tubes from the valve gear, in the case of the OHV models, and by oil mist from the crankcase, in the case of the VB. This meant that the avoidance of over-oiling at the top-end led to under-oiling in the timing chest, a well known shortcoming of this simple design.

In all cases the barrel and cylinder head were made of iron and the valve gear for both the OHV and the side-valve engines was driven by the same camshaft and follower arrangement.

During 1946, the girder forks on the Red Hunters were replaced by Ariel's own design of telescopic forks and, for 1947 all models were equipped with the telescopic forks. Anstey's design for rear plunger suspension, employing the stirrup and link mechanism, was available from 1947 as an option on all models. 1948 brought nothing new except the introduction of the Smiths Chronometric speedometer to all models and a slight increase in the standard compression ratio for the 350s and 500s. The 7.5:1 compression pistons were still available for the more sporting minded rider.

The Smiths Chronometric speedometer was already popular among Ariels competitors. It had a very pleasing incremental display, driven by an ingenious mechanical integrator. It counted the number of revolutions of the cable in a fixed time increment and set the needle position accordingly. If the cable were to break then the display would freeze at the last known value, which gave the impression that the gauge had broken. However, a replacement cable would see it spring back into life.

For 1949, a number of changes were introduced. Improvements were made to the forks, finned exhaust clamps were added and a slightly higher output dynamo was fitted to all models. The side-stand, which has been an option, became standard and a Burgess air filter was offered as a new option. The existing options for the twin-port head and upswept pipes were withdrawn for the 500 models. Also during this year, an all-alloy off-road competition model was announced, designated VCH. It came in two variants, for trials or scrambles.

Apart from having both barrel and head in alloy, the push-rod tubes were integral to the barrel casting, a preview of the later singles. The alloy barrel had an iron liner and the alloy head, like the later alloy-head models, had an iron “skull cap” to reinforce the area around the valve seats and the spark plug hole. This allowed Ariel to avoid the cracking issues that some competitors suffered with their alloy heads. The frame provided more ground clearance than standard and was offered in the rigid form only. The VCH models continued for 1950.

In 1951, the speedometer was moved from the tank panel and built into a new design of top yoke on the forks. A new Lucas headlamp shell was adopted for all models, with the headlight switch and ammeter incorporated. The tank panel was no longer needed, which allowed the capacity of the fuel tank to be increased slightly. The twin-lobe cam was replaced with a new single-lobe cam and new followers to suit. The change was introduced to reduce mechanical noise and reduce wear. The new larger fuel tanks were now finished with an all painted surface. The Deluxe models (NG and VG) were dropped from the range from this year.

In 1952, the VCH was replaced with a new all alloy-engined model called the VHA, which lacked many of the special sporting features of the previous model. All of the others now used the Burman GB gearbox instead of the CP and BA boxes. The cylinder head on the VB 600 was replaced with an alloy head and its lozenge-shaped silencer was replaced with the cylindrical one fitted to the other models. A larger oil tank was fitted to the VH in 1952 but the NH didn't get it until 1953. Also in 1953, a dual seat option was offered and an external and rather feeble pilot light was added to the bottom of the headlamp shell on all models.

In 1954 all of the OHV models had a new duplex cradle frame with swinging arm rear suspension. The swing-arm models all had a dual seat and a new oil tank and tool box, to fit the new frame shape. The iron barrel on the VH had integral push-rod tubes, just like the previous alloy barrels, and the alloy cylinder head was fitted. The NH engines continued as before. In this year a new four-gallon fuel tank was fitted to all of the models, with chrome panels and a distinctive fluted design on the top.

In the same year, the VHA was discontinued but replaced with a 500 scrambles model (HS) and a 500 trials model (HT), both with the all alloy engine. The HT engine had a much softer state of tune that the HS engine and there were differences between the two models in the configuration of the frame, fittings, exhaust and tyres.

The VB continued to be available in the rigid-framed model for 1955 but it was also offered in a swing arm model, which shared all of the cycle parts with the VH. In this year, some changes were made to the OHV models, including a 19” front wheel and a change to the Amal Monoblock carburettor. The front rocker box cover was fitted with a small inspection plug to make it easier to insert a feeler gauge in the tappet. The HS and HT models were unchanged for 1955.

1956 saw the introduction of the alloy full-width hubs on the front and rear of all of the singles. Apart from their appearance, these were not an improvement on the single-sided brakes fitted to all models up to that time. They performed poorly and the new cast aluminium torque arm was too weak.

A number of other changes were made to the range at that time. The fully enclosed rear chain (FERC) was offered as an option and the cable-operated rear brake mechanism was replaced with a rod-operated alternative. A rather ugly head lamp cowl was fitted, to follow the trend started by competitors such as Triumph and Royal Enfield and the pilot lamp was moved to the headlight reflector. Also in this year, the NH engine acquired the integral pushrod tubes and alloy head like the VH. The rigid-framed VB was dropped.

In 1957 came the introduction of the single central bolt fixing fuel tank. It no longer had flutes and the shape of it was rather bulbous and ugly compared with the earlier incarnations. For some reason, Ariel chose to throw away the advantages of a single bolt fixing by adding an elaborate and unsightly chrome-plated metal band to cover the bolt hole. Why they didn't copy BSA's neat and effective method of covering the bolt with a simple rubber plug is a mystery. Equally inexplicably, they also continued with the ugly and impractical headlamp cowl, although the small instrument panel above it was a more useful feature. At least, it would have been if they has implemented it more thoughtfully. Some other cosmetic changes also appeared, the most obvious of which was the deeply valanced front mudguard and the removal of the front stay.

A smaller version of the HT5 was introduced in 1957, with an all alloy 350cc engine and christened the HT3.

During 1958, the VB was dropped, as were all of the competition models but the NH and the VH continued unchanged from the previous year. This was the end of the line for the four-stroke Ariels since 1958 was the final year of production.