Thursday evening at Foxhall Stadium, Ipswich, and the crowds are flooding in. Floodlights illuminate the oval stage, the tape drops, a thrilling roar of mighty engines as the spinning rear wheels throw out a plume of cinders in their wake.  Four riders bank into the first bend and power through the turn with their bikes at a jaunty angle, wrestling the bars to point the wheel down the track.  A deafening blast as the bikes hammer by on the back straight, while the scent of Castrol R hangs heavily in the air.

Captain Louis cruises round his lap of honour, arm aloft - Ipswich Witches win again!

This was speedway racing at its zenith in the early '70s, at which time Peter Cornish was living in Bradfield St George and running Mustang Tools in partnership with Jeremy Woodhouse.  The Woodhouse-Cornish duo initially came together as Woodhouse had a plastering business, and Peter Cornish developed a cutter for him to do some tile work.  They started making the tile cutters together, registered a patent, and selling them to builders' merchants as Mustang Tools.  The range of equipment progressively extended to fencing tools, then design, development, patent and manufacture of a specialist pipe cutter that was subsequently taken up by Hepworth Building Products of Sheffield.

Our interest in this business joins at the point where Peter Cornish purchases five Anker Laura motors out of Exchange & Mart in 1973, and within a week has created a garden/track bike for use by his sons Nick (7) and Mark (9).  The frame was built using square box section tube, including the petrol tank formed between gusset plates welded into the frame headstock, mounted 1" diameter rigid tubular forks, and ran on Raleigh Wisp wheels.

From its appearance in July 1970, these Anker Laura moped engines were coming as leftovers from BSA's Ariel 3 debacle, the market being flooded with surplus parts once the infernal granny-killer tricycle was abandoned.  Though the Ariel 3 was officially de-listed in December 1974 when the last of the stocks finally became cleared, the project was written off somewhat before this time when BSA realised their marketing vision of future mopeding would not be riding on 3-wheels. We're not quite sure of the formal cancellation date of the Ariel 3, but Euro-Equipment Supplies were certainly advertising 'surplus' Anker Laura engines in Model Engineer as early as 1st June 1973.

Adapting the Ariel 3 Anker engine for application in the bike involved machining the toothed belt pinion on the clutch drum down to a locational boss, and welding on a 12T Mobylette front sprocket to convert to primary chain drive, then covering the dangerous whirling bits by a fabricated steel chaincase.  With the intermediate sprocket shaft located from a fixed-point boss welded to the frame, the primary chain is tensioned from the engine mountings, and final drive chain by conventional cam adjusters at the rear wheel.

Paul Hunt riding the very first SIM

Painted red, this prototype had a low mounted carburettor out the left hand side, proving a less than ideal location since the air filter, adjacent to the footpeg, was vulnerable to being knocked off.  Also recognisable by the half-width hub Wisp front wheel, Paul Hunt is pictured riding this very first SIM, since it wasn't long before a number of youngsters about Bradfield became micro-bike riders around their back gardens, or in sunny summer holidays, where 20-30 kids would queue patiently for their turn on the bike for laps around the village green.

With neighbouring youngsters showing much interest in the mini-cycle, enquiries came in from other parents for further machines, so another four bikes were built around the remaining engines and all sold locally.  Their carburettors were now relocated above the engine on a U-form manifold, fabricated from the same square section tube that made the frame.

It was becoming apparent that this little garden bike had some potential, and Woodhouse Cornish were considering the prospect of larger manufacture.

At this time, many ex-trade motorcycle parts were being advertised for clearance through Motorcycle News, by Harris of Watery Lane, Birmingham, including considerable stocks of surplus new Anker Laura engines.  Peter Cornish purchased their first batch of 500 engines at just £3 each, along with quantities of hubs, sprockets, spokes, and 2×12" Dunlop 36 hole back rims (surplus Raleigh Wisp), tyres, tubes, cables, brake levers, and throttle twistgrips, all bought in job lots by the pallet load.

Production commenced at Bradfield St George with the building of around 100 machines to the original (Mk1) square-tube frame design with rigid fork, and badged by a simple black & white SIM50 logo on an oval decal.  These early machines were further characterised by matching full width alloy hubs front and rear, built up from rear hubs laced into 36 hole rims with a 44T sprocket fitted at the back, and individual exhaust arrangements as the concept developed.

Mark I SIM

Having no kickstart or pedals prescribes push starting as the most suitable method for our Mk1 SIM.  Fuel on, but there's no choke mechanism fitted on this Encarwi 12mm carb, so we need to put a left-hand thumb over the air intake tube just ahead of the seat, while decompressing on the twistgrip with the other hand. With the motor being ratchet driven as the bike moves forward, weight needs to be placed on the frame to prevent the wheel skidding, so sit on saddle and 'paddle' away, then turn on the throttle to fire up the engine, which starts pretty easily so you can readily take your hand away from its intake tube.  The motor gives out an aggressive crackle through its straight-through exhaust, and after warming the engine, the automatic clutch keenly snatches as the throttle is opened.  Torque afforded by Anker's reed-valve induction strongly overcomes the snappy drive engagement, and offers useful acceleration without lots of dramatic revving or clutch slipping.  Followed by the pace bike, we burn up the track to top out at 27mph with a loud droning racket blaring from the unsilenced pipe.

With the establishment of initial orders, the original square tube, welded assembly frame was succeeded by a ¾" diameter tubular loop design, more suited to volume build as production relocated to a larger unit at Station Hill, Bury St Edmunds.

The frame was now mounting own-make telescopic forks, and a fabricated steel petrol tank with SIM50 badges on a union flag background.  Instead of mounting a front mudguard, a speedway-style alloy stone guard bolted to brackets on the frame downtube.

"Despite only standing to
knee height against an adult..."

The presence of a front brake became deemed unnecessary and discarded during the transition, to be replaced by a plain cycle hub.  Arguably in the spirit of speedway bikes having no front brake, this decision may also have been influenced by the further purchase from Harris of a large batch of cheap 28 spoke cycle wheels built with 16×1.75 MW Italian rims.

The straight pipe exhaust of the illustrated brochure subsequently received the addition of a silencer barrel, and an alloy plate was included on the right side to further shield the reduction drive for production models.

Since the SIM bikes were never intended for road use, none were ever formally identified by any frame serialisation.  It therefore seems most logical to qualify the sequence of models by their different frames, so for purpose of identification, this model is defined as the Mk2.

The trade introductory letter describes the SIM50 as a "small speedway motorbike designed for children between 5 and 10 years old, and strong enough for an adult to ride".  Despite only standing to knee height against an adult, this tiny bike certainly was substantially constructed, with the main forks comprising 1" diameter × 1/8" section tubular legs welded into steel yokes flamecut from ¼" gauge plate.  No ball race sets in the SIM steering head either, which reflected speedway practice to pivot on phosphor bronze shouldered plain bushes.

Television features appeared on the BBC Look East and ITV's About Anglia programmes, an entry found its way into the On Two Wheels magazine, and Motor Cycle News included a 2-page feature.

Though dealer interest in the SIM50 was quite encouraging, this really only represented a minor sideline of the company's main business, which was making significant quantities of building trade equipment at this time, such as brick lifters, brick profiles, paving slab cutters, and ceramic pipe cutters.

"SIM50 advert featuring John Louis

Sales shortly went national as SIM promotions began appearing in the motorcycling press, and during the run up toward the festive season, "Order now for Christmas" advertisements appearing in Motor Cycle News, carried a 'Footnote to the trade: owing to the heavy demand for SIM50, we need more notice on orders'.  Re-costing the new the Mk2 had also now increased the RRP to £120 + VAT.

As a typical example of parents across the country, speedway fan Errol Bristow purchased a new Mk2 SIM from Andy Lee Motorcycles of Cambridge, as a late birthday present for his son to ride. He still has the bike, and the original invoice dated 15th May 1976, showing a price already increased to £132.26p, which starkly illustrates these inflationary times!

As the scene of youngsters riding Nigel Bristow's new toy around Watton Village Green in Norfolk came to reflect the activity at Bradfield, other customers included the famous store of Harrods at Knightsbridge, where Peter Cornish recalled personally delivering five machines - all purchased to go to the Middle East, while stunt rider Eddie Kidd was also reported to have had a SIM50 as his first bike!

Mark 2 SIM50

Starting our Mk2, simply turn on the fuel, raise choke lever below the seat at the right hand side, twist the throttle grip ahead to decompress, with one knee on the seat to put weight on the frame and prevent the real wheel skidding, scoot down the drive, turn on the throttle and the automatic clutch takes over the moment it fires.  For smaller youngsters, it's just as easy to 'paddle' the bike off - they quickly get the hang of the starting procedure.

The exhaust gives out a pleasant flat burbling tone as we warm the motor and switch off the choke.  Initial acceleration on this Mk2 might be slightly stunted by the fitment of a Dural 38T rear sprocket that became installed to spoke-wheel versions of this model once stocks of the 44T sprockets ran out, though expectation of any higher top speed proves limited as the motor enters a rage of four-stroking at 25mph (not an unfamiliar effect to many Ariel 3 riders).

As the first batch of 500 engines began to run down, a second lot of 1,000 motors was purchased from Harris to continue production.  SIM bikes were typically built in batches to fit in between the commercial building equipment, generally employing a couple of fitters, and at peak assembly times they could reportedly have up to ten operators working on their manufacture.

With the ongoing production, features of the SIM continued to evolve, though there was no distinction between the introduction of specific changes to the Mk2.  The machine simply developed as a series of modifications came through, so a number of bikes can be identified progressively incorporating the various phases.

Changes to the SIM were as often driven by supply of materials as engineering initiatives, not least among such situations being the running out of all suitable wheel component stock at Harris!  To resolve the spoke-wheels crisis, new alloy wheels were sand-cast by neighbouring Haldo Developments of Bury St Edmunds, then finish-machined by Cornish themselves.  While the front remained a brakeless wheel, the rear now sported SIM's own made 42T sprocket and disc, with the cable-operated calliper bought-in from Talon Eng.  The cast aluminium wheels were smaller diameter than the preceding 12" Dunlop rims and, although fitting slightly fatter 2.50×10 tyres, the outside diameter was reduced from 16" to 15".  This reduction in circumference technically dropped the final drive ratio by 6.5%, and was effectively compensated by two fewer teeth on the new rear sprocket (returning the ratio by 4.5%).  This 2% ratio reduction to a sub-30mph bike represented barely ½mph, and was of little real consequence, since a SIM's top speed was of no significance under the conditions it would generally be used.

Mark 3 SIM50

It's often presumed that the later models utilised market standard alloy speedway tanks to further emulate the track bikes.  Not so!  These were actually uniquely produced for the SIM, as Peter Cornish invested a great deal of time in personally making a press tool to form their own petrol tank halves from aluminium sheet, which were then welded together with all fittings within the business.

Moulds were also created now to produce the chaincase and rear mudguard in fibreglass.  Handlebar clamps changed from the earlier alloy block types machined as numbered pairs, to a steel fabricated assembly.  The stone guard switched from alloy plate to steel sheet, as did the reduction drive shield, while the fabricated, square-tube inlet manifold became replaced by a curved form, round pipe.

By the time the last changes to the frame and footrest assembly were in place, replacing the bottom tubes and adjustment brackets by an engine plate arrangement, and a different exhaust system that ran its pipe down between the engine plates and beneath the frame; so much had altered that the SIM50 was a completely different bike and had effectively now entered its Mk3 form.

The choke is now a rotary motor cycle lever, tucked away on a frame plate beneath the saddle.  Fuel on, decompress, and simply wheel the bike down the drive with the engine spinning, then just turn on the throttle and Anker's M-48 fires right up. Our easiest starting machine doesn't even need any weight on the saddle!

The motor warms to a deep and mellow burble from the exhaust, and produces a pleasantly silenced tone as we run down the track at 27mph.

The first SIMs powered by motors other than Anker Laura, were specials for speedway rider Olle Nygren, who supplied ten Sachs 50cc, 7-speed, foot change engines.  Built for Junior Speedway in Sweden, these high revving sports machines demanded bigger, stronger frames than the standard version.

Impressed by these motors, a batch of 50 Sachs Automatic engines was purchased, and built into a completely new (Mk4) chassis to suit, the main frame formed from 1¼" tube, with ¾" loops for the secondary sections.  Welded-in engine plates made up the lower section, and the headstock mounted with a rigid fork set in a seemingly regressive return to the original design, though with a longer yoke.  The luxury of the padded seat on previous models was now succeeded by the Spartan minimalism of a bare steel pan welded across the sub-frame tubes - yes, the Mk4 was made for real men!

Mark 4 SIM50

It appears that the great majority (if not all) of these Sachs SIMs went to entertainment centres, 12 were delivered to the Kursaal Amusement Park at Southend, and a number more went to Charles Manning's at Felixstowe, where they replaced the decrepit go-carts that used to run around on the seafront circuit.

It was here that the author suffered a free ride around a wet and battered concrete track on one at the end of a summer season, but to be fair, the potholed condition of this surface was never going to be sympathetic to any rigid framed machine.  Though the Sachs engine seemed to pull well enough when opened up, the vibrations rattled the loose petrol tank enough to drive any man to madness, while the bare metal pan caused the rider to slide off on corners, and imparted so much discomfort that it seemed a better option to stand up on the pegs instead!  All the while being bombarded by loose stones on the track, and a fountain of spray thrown up from the mudguardless front wheel - just one lap was quite enough to form an opinion!

Perhaps the amusement park's idea was to ensure a constant turnover of punters by discouraging people being on the bikes too long, but that theory seemed to be working a little too efficiently!  The service garage for the Seafront Ride was reportedly packed with SIM bikes, so it appears that most of the Mk4 production ended up here, and was the origin of our Mk4 feature machine after the ride closed.

So how much would we like to relive the Mk4 experience 30 years on?

Still requiring a push start, the Sachs engine in the Mk4 SIM is a slightly different operation.  Fuel on, push down the choke rod on the Bing carb, with one knee on the seat pan putting weight on the frame to prevent the real wheel skidding, scoot down the drive and pull in the clutch lock lever under the left handlegrip.  The engine fires up pretty much as soon as it spins, release the lock lever, allow the engine to warm, and the choke lifts off automatically as the throttle is opened.

Initial acceleration is quite enthusiastic, but soon breaks into a sharp crackle of four-stroking as the engine reaches its rev peak at a paced 22mph, on a 42T rear sprocket. Our private test strip is obviously smoother than the old go-cart track, so the ride didn't seem too bad despite the all-rigid frame.

The Mk4 was built at the same time as Mk3s were still being produced from the dwindling supply of Anker Laura motors.  Peter Cornish reported that reliability of the Sachs Auto proved quite a disappointment, and felt that an increase in the sales price to cover the high purchase cost of these engines would render the SIM50 unviable, subsequently, no more Sachs engines were ordered.

Manufacture of SIM bikes effectively finished when the last stocks of Anker Laura engines ran out around 1986, by which time other imported miniature motor cycles had also appeared on the British market.

All four of our SIM50s

It's unclear how many SIM50s were actually built, since Peter Cornish reported that up to a couple of hundred Anker engines were broken up to supply enquiries after parts, so a final figure around some 1,300 completed machines might be considered a reasonable estimate.

As Jeremy Woodhouse retired and faded from the scene, the business continued as SC Engineering, relocating to larger premises at Rougham Industrial Estate, making manhole lifters for British Telecom, and securing orders to make massive thermal ovens.

Following the SIM50, Cornish also made some 20 trikes using 3½hp recoil-start, industrial engines, for off road/track use.

Now, in the 21st Century, it's pretty well accepted that there are all manner of powered pit-bikes that kids can ride, but back in the early 1970s, the Cornish project was a pretty original idea.

1974 Italjet Mini Bambino

Miniature motor cycles certainly existed before the SIM, but most such earlier examples generally tended to be one-off specials, and not really produced on any commercial basis. Italjet appear to be claiming credit for the first commercially-produced machine design specifically built for children to ride, with their 'Mini Bambino' of 1968.

Although Italjet didn't seem to have any agents appointed to handle distribution of their general motor cycle products in the UK, archive material postmarked October 22nd 1974 promotes Italjet Junior Motorcycles by ACNI Distributors Ltd of Leatherhead, who had established their business on importing white goods, particularly Super SER appliances from Spain.

For the UK, the SIM50 and Italjet Mini Bambino would appear to have been market contemporaries in 1974.  Parents found this choice of available minibikes further doubled from 1978, with introduction of the Puch Magnum and NVT Ranger (that became re-titled the BSA Junior from August 1979.

Just like the mighty JAP and Jawa speedway 500s from which it was spawned, the little SIM50 was also destined to spend its life riding Round in Circles, not by heroes on the oval cinders track, but by children in the back garden.

Now 72, Peter Cornish still enthusiastically maintains his engineering interests, manufacturing his own design of the specialist MPC30 air rifle in low volumes.  Now having sales exceeding 50,000 pipe cutters to Hepworth Building Products of Sheffield, this successful device remains in on-going production at around 1,000 units per annum, as SC Engineering continues, now under the auspices of youngest son Alex.