jw4 Smokey's JW4 Formula Four Rebuild Thread

[Mark (smokey mow)]

JW4 Mark 2

With the loss of Peers from the project, for 1966 Stan Gray of Marcos cars was recruited as a full time manager and Verney Montague was promoted from machining to designer.

 

The Mk2 was as much an evolution of the Mk1 as it was a completely new car. Carrying over the suspension uprights from its predecessor the Mk2 feature an all new square tube chassis with a longer cockpit and a new 3-piece body by Specialist Mouldings. Taking on board the feedback received from potential customers at the Motorsports Show a new rack an pinion steering system was designed by Montague. With no experience of designing steering racks he copied the ratio and design from his own Riley. To aid the balance of the car which was otherwise rear heavy and also cooling of the engine the fuel tank was relocated to the nose just in front of the drivers feet.

 

 

The early cars were again all to be fitted with the 250cc Villiers Starmarker and to aid development of the car Walker recruited ex motorcycle GP rider Derek Minter who had recently retired from motorcycle racing.

 

After persevering with the Starmaker engine for the majority of the 1966 season by the time of the 1967 Motorsports show Minters car was to be sporting a Ducati engine and this show was to also herald the first showing of the new Mk3 developed for the 650cc class.

 

The Mk2 had proved itself to be a very capable and versatile chassis and a notable mention should be made to the Vincent Engined Mk2. This assessment car was a private development by Peter Gerrish using a 1-litre Vincent (Black Lightning) Picador Engine originally designed of unmanned aircraft. The installation of the air cooled V-twin necessitated additionally cooling ducts on the rear bodywork and anticipating that braking might me a problem the rear uprights incorporated brake drum flanges as opposed to the single inboard rear drum more usually adopted.

 

Derek Minters JW4 Mark2 at the 1967 Motorsports Show

[BLiNK Motorsport]

Thoroughly enjoying this thread Mark - it is a real credit to your painstaking research as well. This and StephenH's eleven build are quite superb!

[Yanto]

8 hours ago, BLiNK Motorsport said:

Thoroughly enjoying this thread Mark - it is a real credit to your painstaking research as well. This and StephenH's eleven build are quite superb!

agree 100%.

 

Ian

[Rory's Dad]

...me too!

[Mark (smokey mow)]

11 hours ago, BLiNK Motorsport said:

Thoroughly enjoying this thread Mark - it is a real credit to your painstaking research as well. This and StephenH's eleven build are quite superb!

 

3 hours ago, Yanto said:

agree 100%.

 

Ian

 

2 hours ago, Rory's Dad said:

...me too!

Thanks guys, there's still plenty more to come as yet.  The photos and detail on this thready really only amount to about 10% of what I actually have.  The idea of writing a book has been mooted in the past and all I will say is watch this space

[Dave Eastwood (Gadgetman) - Club Chairman]

1 hour ago, Mark Wendon (smokey mow) - WSCC Club Secretary said:

Thanks guys, there's still plenty more to come as yet.  The photos and detail on this thready really only amount to about 10% of what I actually have.  The idea of writing a book has been mooted in the past and all I will say is watch this space

Yeah, if ever a book was called for this has got to be it, it's just such a fascinating story and rich in the sort of twists and human interest that prevents these sort of coffee table times being dry and boring.

Its a microcosm of the fascinating world of racing from that era.

[BLiNK Motorsport]

16 hours ago, Mark Wendon (smokey mow) - WSCC Club Secretary said:

 

She suits the car better than you though Mark 

[Dave Eastwood (Gadgetman) - Club Chairman]

1 hour ago, BLiNK Motorsport said:

She suits the car better than you though Mark 

I'm still getting my head round Mark deliberately buying a car designed for a midget. 

[Mark (smokey mow)]

43 minutes ago, Dave Eastwood (Gadgetman) - WSCC AO Rep said:

I'm still getting my head round Mark deliberately buying a car designed for a midget. 

I fit the car just fine  but many others might find it to be pretty snug.

I know the comment was said in jest but one prolific owner and racer of JW4's was a midget.  The car in question had two sets of pedals which were positioned both in front and also behind the master cylinders.

[Mark (smokey mow)]

JW4 Mark3

1967 brought changes to the Formula IV regulations with the introduction of a 675cc class for 2-cylinder 4-stroke engines. The 250cc cars were found to be slow in comparison to the fastest Karts so the 675cc class came about in an effort to tempt more Kart racers into the series.

 

To the untrained eye the Mk3 JW4 was visually similar to the Mk2 but with a few subtle design changes. The majority of the changes were made to accommodate the larger capacity engines which involved re profiling and raising the height of the rear engine cover.

 

Suspension was all carried over from the Mark2 and remained unchanged but the chassis design was revisited so as to remove unnecessary weight. Some early developments with a "lightweight" chassis failed to make production after negative press and concerns about chassis rigidity, but even the production Mk3's had much less triangulation and bracing than it's predecessor.

 

The more powerful engines required a stronger drive train. To the rear axle the bearings were held in machined housings as the pressed steel pollard units carried over from Karting had a tendency to distort, but with no differential the hookes joints remained the week link. Trials were carried out with a differential unit from a Berkeley sports car but ultimately it was decided not to adopt this.

 

Walker was keen to promote Formula IV and encourage new manufacturers. He did this by making available for sale to prospective car builders and completion all the JW4's suspension and driveline components. Alex Bottoms Vixen VB1 was one such car to be launched using JW4 parts. The 675cc class was more appreciated by the spectators but the greater power and stickier tyres made for a bigger disparity between the two motorcycle engined F4 classes to the extent that may 250cc Mk2 owners felt obliged to exchange their engines for larger units or return to Karting.

 

The JW4 Mark 3

[Mark (smokey mow)]

Walker Special (Winsmore) - Class 4 Kart

Time for something a bit different.... Penned towards the end of 1966 as an infill project the Winsmore took Walker back to his roots in Class 4 Karts.

 

Almost unique in its construction compared to its competition the backbone of the Kart was an L72 18 and 24gauge aluminium "torque box" monocoque chassis.

 

Suspension at the front was provided by steel tubular unequal length wishbones with swing axle and radius rods for the rear and the rear axle also features a small lightweight differential unit. Engine mountings provided for either Villiers or Bultaco.

 

Other than the prototype shown on the sales literature I am not aware of any others being built or indeed surviving to this day.

 

 

[Mark (smokey mow)]

JW4 Mk3 Imp

A car very well known to me as for a time I owned the original prototype and the only Mk3 JW4 to be built.

 

Along with the 650cc motorcycle engined class the 1967 Formula IV season introduced a further class for car engines of up to 875cc. In competition to Vixen's Imp engined VB4 Walker also chose the Hillman Imp engine for the first of his car engined JW4's.

 

To accommodate the Imp engine and inverted gearbox within the JW4's diminutive frame the engine bay had to be lengthened my 2.5 inches. Other changes to the chassis included an adjustable pedal box and master cylinder assembly which removed the unwanted play in the earlier linkage system. The fuel tank was relocated behind the driver seat and the space under the drivers knees was taken by the batter for the Imp's starter motor. This was also the first JW4 to be fitted with a differential which necessitated modifying the rear uprights to relocate the brake drums.

 

 

Early development with a central mid mounted radiator found this struggled to cool the imp engine so a front mounted radiator was fitted into a modified Mark 3 body. The new nosecone-cockpit surround was again commissioned from Specialist Mouldings with a 'mouth' feeding air to to the radiator but as money problems starting to bedevil the factory they never got paid for their work.

 

This bodywork remains unique as it was not adopted for any of the later cars. Before the Mark 3 imp was ever finished work was halted as the ever enterprising Walker had found an irresistible alternative and new business prospect in Saab. 

 

[Mark (smokey mow)]

JW4 Mark 4 SAAB

During his worldwide travels Walker had received interest from Saab of Sweden who at the time were having considerable rally success. These cars had the Sport 875cc 3-cylinder triple carb 2-stroke engine and Saab calculated that a move into circuit racing with a single make formula would improve their worldwide image.

 

The Imp engined Mark3 was shipped to Sweden for evaluation and an order of 250cars was mooted if the car could be shown to be competitive. Saab were persuaded to pay for the construction of the car in the UK with the engine being installed in Sweden.

 

The First Mark4 chassis was completed quickly and adopted many of the design features of the Mark3 Imp chassis but with additional bracing and triangulation at the rear to support the Saab's cast iron gearbox. The driveline consisted of Saab inboard parts mated to Imp shafts and stub axles. As the Saab engine was shorter than that of the Imp there was room to fit a 5-core radiator between the driver and engine and this combined with the lower height of the engine allowed for a return to the more sleek Mark 2 bodywork.

 

Swedish Rally champion Tom Trana trying the first Mark4 for size.

 

Following a testing accident at Brands Hatch with the first Mk4 a second car was commissioned. The new chassis featured improved rear geometry with equal length arms and longer uprights to hold the now 13" rear wheels. The bodywork of the second car was from the Mark3 as the shorter under-tray avoided the under exhaust system and permitted easier engine access.

 

The Mark4 Saab was raced in both Britain and Sweden and in its time held the class lap record at both Lydden Hill and Mallory Park. In late 1968 the second Mark4 was being shipped back to Sweden when in heavy storms in the north sea a large item of heavy machinery became loose and fell onto the car crushing it. The remains were taken to the Saab competition department but were found beyond repair and scrapped.

 

No further mark4's were built, as Saab decided to withdraw from their proposed formula. The original and first Mark4 lived on and to this day still resides in Sweden with the family of its original driver.

 

The second JW4 Mark4

[Mark (smokey mow)]

JW4 Mk5 IMP - Formula IV / Formula Libre

Although his original company had gone bust Johnny Walker was far from ready to quit and with encouragement from Stan Gray and Peter Gerrish he approached automotive engineer Frank Costin and a new company was formed Johnny Walker (Costin) Ltd.

 

Following the demise of the Saab powered project Walker was determined to follow the Imp route like his rivals due to the availability of tuning options. A new design was commissioned from Costin that would later become the Mk6, in the interim though Walker would continue with an evolutionary design; the Mark 5.

 

The Mark5 was a conventional affair and carried over Much from the design of the Mark3 Imp. In formula IV trim the car ran with a a Willie Griffiths tuned 875cc Imp engine and Jack Knight close ratio gearbox, inverted as per usual. The car was also trialled in Formula Libre with a 1000cc Imp engine. To save money Mark3 bodywork was used with cooling entries for the radiator cut into the top surface of the nose and also the undertray. Front wheels were 12" with 13" rears.

 

The JW4 was now unfortunately beginning to show its age, it was technologically behind may of its competitors that were now using all round disc brakes and the conventional nature of the Mark5 did not make it a race winner against the well developed rivals in Vixen or the Aluminium monocoque McNally.

 

Johnny Walker behind the wheel of the JW4 Mark5

[Mark (smokey mow)]

Costin Walker/ Type AH/ JW4 Mk6 - Formula IV/ Formula Ford

The 1969 Motorsport show saw the unveiling of the newest and also last car to bear the Johnny Walker name; the Costin Walker. Still in its unfinished state the cockpit internals were blocked from the media's view and the aerofoil was made from wood.

 

When finally revealed the all Costin designed aluminium body clothed a totally new design of chassis. The modular space-frame consisted of three fully triangulated torsion frames of high complexity and stiffness which to this day is still regarded as the stiffest space-frame ever built. The complexity was a discouragement to some customers however due to the work involved in repairing even the simplest of damage whist the chassis design meant you didn't so much sit in the car as "wear" it.

 

Design and Development of the car was somewhat ad-hoc with Costin only working on the project when Walker had raised sufficient funds to pay him for the next stage of work. Frustrated with progress Frank Costin eventually left the project and Walker handed over the development to Tony Hilder of Piper cars with the car being renamed the Type AH after Hilders initials. Hilder's brief was to sort the handling of the car which required some modifications to the suspension geometry. The car was uncompetitive and Reputably Hilder was unable to tame the handling of the car, this frustrated Walker who never settled the final part of his account.

By 1971 Walker had taken the development of the car back in house and calling the car the JW4 Mark 6 he recruited Keith St. John to resolve the issues which Tony Hilder could not. This development was largely successful but midway through the season Keith St. John crashed the car at Lydden spinning and striking a bank with the front corner causing damage to the magnesium upright and bodywork.

 

A dejected Walker who saw the whole Costin project as a "costly exercise" from which he could not see a return on his investment broke up the team shortly after to retire from racing. The Costin Walker was never repaired and the motorsports business was broken up.

 

Manufacturing and selling rights for the JW4 were quickly sold by the end on 1972 but it was not until 1974/5 would the Costin find a new home. Thankfully this unique car survives in a condition of restoration and one day will hopefully race again.