Mini Twini: twin-engined, four-wheel-drive concept tested in full

| 9 Apr 2014

Twin-engined machines have a special appeal. Bugatti, Maserati and Alfa Romeo all tried the formula, but most of these early applications tortured a single axle. Citroën successfully made it work for an off-road 2CV (the Sahara), but two motors and four-wheel-drive are generally only associated with Land Speed Record machines or military giants.

Who came up with the mad idea of sticking a second engine in the back of a Mini – doubling the power and the driven wheels – isn’t clear, but there’s a good case for maverick engineer Paul Emery. The man who ran front-wheel-drive F3 cars in the early ’50s, and fitted the first disc brake on a racing car in Europe, was always non-conformist. By the ’60s, this ingenious specials builder had moved away from racing and focused on Minis. As well as the Dart, he designed a ‘Twini’ but gear-linkage problems handicapped its progress and Emery’s Fulham workshop switched to tuning Hillman Imps. “Good traction, but that’s about all,” was how Emery dismissed the failure, yet his concept soon set others off on the same track. First, Alec Issigonis developed the ultimate Mini Moke, whose four-wheel drive and doubled torque proved highly impressive on winter snow trails in 1962.

Mini Twini gear linkage

During a visit to the Longbridge factory, John Cooper got a chance to drive the Twini Moke. The BMC design team relished any opportunity to demonstrate its four-wheel-drive toy and the motor sport legend was hugely impressed by its power and dramatic traction. The test sowed a seed, and he tore back to his Surbiton factory with the idea of building a Mini road car with a similar layout. While his single-seaters struggled to deliver, Cooper became obsessed with the Mini project and talked of nothing else. Mini parts were scattered over the workshop floor, and within six weeks a running prototype had been built up from a bare shell and was soon scaring motorists around the Hollyfield Road works.

Cooper fitted a full FIA Group 3-spec 1088cc motor – with Formula Junior head and twin 1½in SU carbs – in the nose, sending 82bhp to the front tyres. The rear rubber had a tougher time from a tuned 1212cc motor punching out 96bhp. ‘The installation work was a very neat job,’ reported John Blunsden in Sports Car Graphic, ‘and with typical Cooper thoroughness it had been made into a robust little car.’

Mini Twini interior

The extra torsional strength demanded by this 178bhp, 1600lb road rocket came from steel channel sections under the doors, plus a rear subframe reinforced by crossmembers and fish-plated corners. The twin gearboxes had matching ratios and the levers were linked by a sliding rod to allow synchronised changes. “The steering arms were bolted to the rear subframe and virtually became another wishbone,” recalled Cooper in the ’90s. “There was no problem synchronising the two ends since nature acted as a differential. It was marvellous on snow and our drivers loved it on tarmac. We thought it could be the ultimate rally car and developed it in parallel to BMC with the intention of making 1000 of them to get it homologated.”

The Cooper Twini never raced, but Sir John Whitmore did test it extensively at Brands Hatch and got down to a 67-second best on special 4½in magnesium wheels. On narrower rims he later pushed too hard and spun off. “The Twini was very neutral when both engines were in tune,” reported Whitmore, “but if one played up the handling changed dramatically.” At Goodwood, when the front motor failed, he lapped with just rear power. Although the racing knight’s times were 2 secs faster than the Mini record, on the limit the Twini oversteered like a pig.

Mini Twini cornering

The Cooper-built Twini came to a dramatic end on the Kingston bypass in May 1964. The huge accident not only destroyed the car, but also left John Cooper fighting for his life. En route to Roy Salvadori’s new Esher home for a dinner party, the Twini rolled several times and Cooper woke up in hospital with cracked ribs, amnesia and severe concussion. The timing was particularly bad because his father was frail with heart problems and control of the racing team seemed to be ebbing away. The wreck was so bad it was difficult to ascertain what had caused the smash. One theory reported that the front engine had cut out, or possibly a gearbox jammed, causing a sudden change in handling. “We think the balljoint in one of the steering arms seized,” said Cooper. “It was a freak accident, but the publicity killed the Twini stone dead and BMC did the same. It was a pity; the idea had enormous potential, particularly in rallying. It was years before the Audi quattro.”

Mini Twini rear engine

In parallel with Cooper’s project, engine tuning specialist Downton Engineering also produced a Twini that it boldly entered alongside a standard car in the 1963 Targa Florio. Fitted with two 998cc Riley Elf engines, the car was only just finished before the team left for Italy and had barely been tested. Braking was by Cooper ‘S’ discs all round and the transmissions had straight-cut competition gears. The suspension was lowered by 1in and the fuel tanks carried six gallons. Whitmore was teamed with Le Mans winner Paul Frère, who came out of retirement for the classic Sicilian road race. The large air scoop just ahead of the right rear wheel channeled air to the engine, but the Mediterranean heat took its toll on the ‘prototipo buffa’ (funny prototype), which ran in the under-2-litre GT class. ‘It was great fun and greatly admired for its audaciousness,’ wrote ‘Jenks’ in Motor Sport.

Mini Twini prototype

The Targa Twini was plagued with problems and forced to stop several times on the course during the early laps to refill the radiator. In addition to the overheating, the tortuous mountain circuit caused transmission problems and the paired linkage often failed to synchronise gearchanges, resulting in the two engines turning at different speeds. Frère proved the more cautious of the team, setting slower times in an attempt to conserve coolant and tyres, while Whitmore was a crowd favourite, blasting the Twini over the start/finish line in a full-blooded powerslide to cheers of “avanti” from the locals. “We’ll have some fun,” Whitmore informed Jenks, “even if it doesn’t last the race.”

Mini Twini Targa Florio

Thankfully for the Downton pit crew, the weather later cooled and the regular stops for water abated. Both Minis made the finish, albeit two laps down on the winning Porsche, with the standard car of Bernard Cahier and Rob Slotemaker 25th, two places ahead of the Twini. No doubt they had a happier post-race party than Ferrari, which lost the lead on the last lap.

Mini Twini engine

How many Twini Minis were built is a mystery. If you include the Moke and Emery’s effort it was four, but contemporary reports record BMC also building a saloon. Sadly, only the Moke survives. Roll on four decades and Jeff Lane, collector of weird and wonderful motors for his Nashville museum, started thinking about a Twini to join his 2CV Sahara. His search for a survivor proved fruitless, so the only option was to recreate one. Through his passion for microcars, Lane met British Peel enthusiast Andy Carter at the marque’s 50th anniversary return to the Isle of Man. Carter then sourced a rare Mini-based Peel Viking and restored it for Lane. “Jeff was pleased with the car, which led to enquires about the Twini,” says Carter. “No one seemed to know what happened to them, other than that the Cooper car was destroyed in 1963. My hasty suggestion that we could easily build one was immeidiately taken up by Jeff.”

Mini Twini dashboard

Two donor Mk1 shells were sourced, and work started in August 2007. By chance, Carter’s son Rory owned a Mk1 but he refused to let dad cut it up. “Our key reference was a cutaway drawing and detail photographs published in an American magazine,” says Andy. “Without that we would really have struggled on the cockpit details. We decided to go for 1275cc power units with identical tune at both ends. It was important that the gearboxes had the same final drive, too. Like Cooper, we chose rubber-cone suspension with disc brakes all round. The beautiful simplicity of the Mini made the job easy. Although the project was built for show, it had to work.

“Like Cooper’s Twini, the stripped shell was stiffened by bars in the sills. The boot floor and bulkhead were cut away to take the rear subframe, which helped to make the shell really stiff. The rear subframe proved too wide, so we ended up sectioning 1in out of the centre.” The single 12-gallon fuel tank, positioned behind the front seats, has a feed and separate pump for each set of 1½in SUs. “That way you can still drive the car on one engine,” says Carter. “The accelerator works both throttles and, with the PTFE-lined modern cables, the doubled action is still light. Unlike with Webers, the accelerator just operates the SU butterflies and doesn’t prime the fuel. One pedal also works both clutches. The exhaust is a single system with both engines linked into a neat stainless-steel transverse box under the rear, all fabricated by Andy Newton at GranFab in Nottingham. Access to the rear engine is excellent, thanks to the removable cover. It takes just four bolts to get to the plugs.”

Mini Twini vent

 The Twini was fully assembled before the cosmetics were started: “I wanted to make sure it worked before trimming and paint. The ride was firm, but it settled down with the extra weight of a passenger, and the braking was fantastic.” Reassured, Carter commenced the final fittings. The Tartan Red paint scheme was done by H&D Autos of Sutton-in-Ashfield. Just like in the Cooper Twini, the floor remained painted metal with rubber mats, but a pukka ’60s-style rally seat for the driver proved a challenge to find. This and the standard passenger seat were trimmed in period fabrics. Cooper alloy wheels with black-painted centres completed the job.

Prior to it being shipped, Lane generously allowed C&SC to test the Twini before he had even seen it, let alone driven it. Settle into the hip-hugging rally seat and you feel as if you’re suffering from double vision. Not only are there two gearsticks between the seats, but the instruments are also mirrored. All of the key Smiths gauges are doubled up – with the exception of the speedo and ammeter; only the front engine charges. Weirder still, there are two ignition keys. Carter advises we warm up the rear engine first, then start the front unit once the rear temperature needle has moved. With fuel pumps behind chattering like castanets, the front engine barks into life. You can’t help but laugh at the drama. Push the throttle, watch the tachometer needles move in unison and revel in the fantastic stereo engine notes. The noise isn’t intrusive, but you feel as if you’re having your own traffic-light race with a second phantom Cooper. Even before we’ve engaged first gear, I love it.

Mini Twini panning

Our test day is one of the summer’s wettest, but Carter and the mint Twini aren’t phased by a rain-soaked airfield. The throttle and clutch action feel no heavier than a standard Cooper’s, but gear selection takes some adjusting to. You work one lever, but both sticks operate via a cross-bar connection. If you wrong-slot into fourth rather than second, the mighty torque of 2550cc and eight cylinders easily copes with the taller ratio. Once familiar with the baulky gate, traction from the four driven wheels is staggering and the more you use the revs the more the sounds meld into one throaty bellow. Although the Twini has done few miles, Carter encourages me to push it and the roadholding is startling. The faster you motor through the apex, the more neutral and balanced it feels. When it does let go – as Whitmore discovered at Brands – there’s little hope of catching the Twini. The all-round discs shed speed like no classic Cooper I’ve experienced, pulling up straight and strong.

The Twini isn’t road legal, but I’d love to take it out and outrun a few BMW Minis. They’d never understand that telltale side duct or the Abarth-style boot prop. Look out Nashville.

This article was originally published in the September 2008 issue of Classic & Sports Car magazine, which retains the copyright to all words and images. Click here to see our terms and conditions.

Words: Mick Walsh; pictures: Tony Baker