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Corvette Road Test

Mark Daniels

Devoted Buzzers need not become concerned that the last refuge of motorised eccentricity has defected to mainstream glamour articles on classic American muscle cars, since this report does not cover the pretentious V8 Chevrolet sports car, but the far more exotic Hercules Corvette moped as made by the Birmingham Cycle Company.

Hercules Corvette

Regular readers may well have picked up a periodic mention of this machine in items over the last year, but few will probably have much idea what one is since they are rare creatures indeed and only some seven examples are currently believed to survive.

Though Hercules was among the oldest and largest of British cycle companies, it only occasionally dabbled in small capacity motorised transport.  From 1912, the first machines used Precision and Sarolea single cylinder side-valve engines, up to 1914 when a 211cc belt driven two-stroke was offered.  WW1 presumably interrupted motorised manufacture, which was not resumed until late 1955 when the Grey Wolf moped was launched at the Earls Court Show.  Soon renamed the Her-cu-motor, the model ran on till 1958, when the JAP engine supply was turned off by the hand of Villiers.  This left Hercules with nowhere to go, since the in-line motor and shaft-drive arrangement meant that no other installation was suitable for the frame.  Launched in 1960, the Corvette became Hercules's parting shot as the TI Raleigh Group's decision to factor Motobécane products killed it off in 1961.

The simple T-form welded frame was made up from an unusual oval section tube and on it was mounted a petrol tank, carried over from the Her-cu-motor.  Being part of the British Cycle Corporation, forks, heavily valanced mudguards, rack and stand seemed to have been borrowed from Phillips and were common to their Mk2 Panda, but the Hercules assemblage was then disgraced by large and unsympathetically styled side-panels in composite steel and aluminium.  The light blue and white paint job with pinstriped dream topping suggested the rider could be an aspiring ice-cream vendor and the Corvette didn't look set to give the competition much cause for concern.  Early models were supplied with half-width hubs at both ends, phased through a full width rear, and finally to full width at the front as well, which helps accurate dating.  The cast aluminium belt flywheel and 6.1:1 compression × 1.8bhp engine were of AML Lavalette origin.  Breathing through the D12 Gurtner carb, it claimed a reasonable maximum of 37mph.  Motor layout was a conventional fore and aft porting in a cast iron barrel with a typically continental aluminium head finning pattern suited to accommodate a fan cool shroud location for scooter applications, for which variants of the motor were also used.  Lavalette's own VM flywheel magneto generates sparks and the usual 18W electrical output to Miller front & rear lighting, while the two stage automatic clutch transmits power back from an outboard pulley. The exhaust system is quite quaint with the down-pipe appearing like an inflated banana and ending in a cylindrical silencer beneath the motor.  Brake operation is orthodox cycle hand levers, so with all conventional controls there are no peculiar considerations to deter the novice rider - fine, so off we go!

The dainty little centre stand was very clearly never intended to take any stationary starting efforts so this is a machine that really should be pedalled off down the road.  Fuel on, and the choke clicks down to spring release when the throttle is opened.  There's no decompressor facility to the engine so it takes a fair bit more effort to get the motor spinning and requires just enough delicate take-up on the throttle to start firing without tripping the choke, then allowing the motor to warm for a few seconds before opening up.  Right from the outset, this is not a very user-friendly start!  According to the engine makers, the centrifugal locking clutch isn't supposed to come in until 9mph is reached, but on the test machine this occurred almost immediately, so required pedal assistance to pick up working revs.  The clutching spring position does not appear to be adjustable so the spring tension may be considered suspect.  The motor begins to perform better once well warmed up and, with its moderate intake surge and roaring exhaust, feels strong enough to suggest the 1.8bhp claim is pretty fair.  The claimed 37mph maximum would take a pretty insensitive pilot to achieve for more than brief bursts since holding constant speeds much above 30 seems to induce vigorous bouts of four-stroking (over large main jet?) resulting in a fair number of mechanical protestations emanating from within the engine.  Pulsing the twist-grip helps to regulate this condition, though the "throttle-on" sound produced from the motor could be misinterpreted as a 'race challenge' to any accompanying rider.  This trick obviously can't be worked when holding full throttle and it comes down to a trial of the rider's nerve against the engine noise, so you tend to back off to a comfortable cruising speed around 25-30mph on the bouncy needle Huret approxometer.

The cable operated rear brake is pretty weak and wouldn't be anyone's choice of emergency equipment, though these same British Hub Co units seem to be quite effective on back pedal set-ups with their better leverage and solid rod linkages.  The long cable and hand operated lever appears to be to blame and is not an uncommon problem for similar arrangements on other makes of machine.  It has to be said that the front brake is nothing to enthuse about either, so a think ahead riding technique is recommended.  The unshielded outboard belt drive pulley unsurprisingly turns out to be as vulnerable to rain water ingress as it looks, and under wet conditions will readily slip however tightly the belt is tensioned.  Despite its many foibles though, the Corvette proved totally reliable in operation and required no service attention to even a single item over many miles, quite a number of which were performed in particularly inclement weather.  Even for a rider of average build, it just doesn't seem possible to find a happy riding position since the frame appears to pitch the seat too far forward.  With the handlebars set back for an upright stance they come too close and low for comfortable turning control, and the grossly over hard fork springing gives a harsh ride.  To negate these effects the bars are adjusted to a forward hunched position to put more weight onto the forks which, feeling more stable and 'sporty' than an upright position, can become quite tiring on the arms over moderate distances.  Coupled with the rigid tail, this can't recommend one of these as a coast-to-coast machine.  Whatever the set-up, handling on corners feels quite uncertain, though I couldn't be sure whether this was due to the design geometry or the fact that the frame had required re-aligning and welding back together after being sawn in half by its last owner to fit in the boot of a car with the intention of taking for scrap.

Considering the sad history and a reconstruction process over some 20 years to acquire all the missing original parts (and there were a lot of parts missing), it's probably surprising to anyone this unusual machine even exists at all.  Currently it campaigns occasional rallies in unrestored condition, having been assembled as a working 'pre-build' to progress re-registration prior to eventual renovation, which goes to explain its current cosmetic appearance.  The styling may appear somewhat 'odd' today, though was not too untypical of the period and the machine adequately complied with the primary requirements of a moped: cheap reliable transport over short distances.  The automatic clutch was probably a reasonable sales feature at the time, but overall there was little to recommend the Hercules over any other basic machine in a fiercely competitive market place.   

If the test bike can be considered representative of the model, it's hardly surprising the Corvette didn't find much of a market in its short span of life; nor that it seemingly failed to endear itself to many owners for few examples survive from the limited numbers made.  Forty years on and it's easy to see that the obscure Corvette is unlikely ever to become one of the great classic mopeds, and the handful of machines left are just rare oddities for eccentrics to ride and the moped spotters to look out for.  Now if you've actually decided you want one of these machines - forget it!  Hercules Corvettes were made out of unobtanium, it's like metal but you just can't get the stuff!

First published, April 2001

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