Old Bike Australasia: Ariel Square Four – The Squariel – Shannons Club | Motorcycles catalog with specifications, pictures, ratings, reviews and discusssions

Old Bike Australasia: Ariel Square Four – The Squariel – Shannons Club

9 May 2015 | Author: | Comments Off on Old Bike Australasia: Ariel Square Four – The Squariel – Shannons Club
Kawasaki Square Four 2 Stroke Prototype

Old Bike Australasia: Ariel Square Four – The Squariel

Story and photos . Jim Scaysbrook

The story of the Ariel Square Four must start with the young Edward Turner, who in time, would rise to become the most powerful figure in the British motorcycle industry. But it was a different situation in the mid 1920s, when young Turner was a struggling engineer in London, cobbling together a 350 cc overhead camshaft-engined motorcycle of his own design in a tiny workshop.

He had dreams (and designs) of producing a four-cylinder machine, but this was way beyond his modest means, and although he had hawked the concept around the trade, there were no takers. Then, during a visit to Birmingham with his blueprints under his arm, Turner met Jack Sangster, the owner of the Ariel company at Selly Oak, and Sangster agreed to give the youngster a drawing office, as well as an assistant Bert Hopwood. Turner reasoned that his square-four design overcame the bugbears of the normal in-line four which, when mounted transversely in the frame was too wide, and when mounted fore-and-aft, resulted in an overly long wheelbase.

What emerged was a 500 cc design with a chain-driven overhead camshaft, with the drive to the gearbox taken from the left-hand end of the rear crankshaft. It was in effect a doubled-up vertical twin, with the two cranks coupled by gears.

The prototype engine was mounted in the lightweight frame used for the company’s 250 cc single, but by the time the new model was ready to be displayed at the 1930 Earls Court Show, the engine had been transferred to the more robust chassis used for the 500 cc Ariel single. A hand-change four-speed Burman gearbox was used initially. The Square Four (catalogued as the model 4F) caused a sensation at the show, sharing the limelight with another new ‘four’, the V4 Matchless Silver Hawk.

The economy, on the other hand, was on a rapid downward spiral following the Wall Street crash, and even though Ariel was gearing up to produce the new model for 1931, the company was already in serious strife. So serious in fact, that by 1932 Ariel was bankrupt, and was only saved by the injection of private capital from Jack Sangster, who reformed the company into Ariel Motors (JS) Ltd. Staff numbers were slashed and the majority of the factory leased out.


Motorcycle production shrank into one small section of the premises, and the ranged of models trimmed.

Surprisingly, given the austerity of the times, the big-ticket Square Four remained in production, but the engine was scheduled for a major redesign in the coming years. Early examples suffered from insufficient cooling of the cylinder head and rocker box, resulting in frequent blown head gaskets. To encourage sidecar use, the capacity was quickly upped for the second year of production to 587 cc, by the simple expedient of over-boring each cylinder by 5 mm.

For 1933, a four-speed, positive stop foot change gearbox was added.

In the next major redesign, towards the end of 1935, the costly overhead camshaft operation gave way to pushrod overhead valves. Down below, the original design which had overhung cranks (with the exception of the driving crankshaft on the left rear) was completely redesigned to feature full crankshafts, coupled by gears on the left hand side, rather than in the centre. As well as the 600 cc version, a full 1000 cc job was also on offer when the new model (known as the 4G) went on sale in 1937.

The larger model put out 38 bhp at 5,500 rpm and Ariel claimed it would pull from ten to one hundred miles per hour in top gear.

In 1939, a unique form of rear suspension was added (as an option) to the Square Four, and also to the single cylinder Red Hunters. This was a form of plunger suspension, but with pivoted links that allowed the rear wheel to travel through an arc, giving constant chain tension. Both the 600 and 1000 versions dispensed with Amal carburettors in favour of the Solex 26FH carburettor and from 1938, the Solex 26AH.

Ariel Square Four

Just when things were looking rosy, along came the war, and much of Ariel’s production was switched to armaments and other engineering, although a 350 cc military model based on the 1939 Red Hunter was produced. When peace returned, motorcycle production at Selly Oak at first concentrated on the 350 single, but eventually the Square Four went back into production, but in 1000 cc form only.

By this stage, Ariel had new owners the BSA Group but the company, at least publicly, remained in charge of its own destiny, with former racer Ken Whistance at the helm. The Square Four again was the subject of a major redesign (the Mark I), with telescopic front forks and the substitution of aluminium alloy for major engine components, including the cylinder block and the head. This chopped a whopping 33 pounds (15 kg) from the considerable all-up weight.

The engine was still in its pre-war ‘two pipe’ form, with the exhaust ports exiting from manifolds attached to the cylinder head, but it 1954 another major redesign took place to produce the Mark II version the ultimate incarnation of the design.

When the British magazine Motor Cycle tested a Mark II in 1956, the report said “few, if any, other types of machine provide the same feeling of exhilaration. The driver of a ‘Squariel’ has four cylinders and 1,000 cc at his fingertips, waiting to respond to his every whim.” The tester confirmed the amazing flexibility of the engine, which pulled ‘snatch-free’ from 10 mph to the top speed of 102 mph.

It also praised the braking capabilities, saying. “with such an abundance of power and speed at one’s disposal, the subject of stopping quickly and safely becomes one of prime importance. The magnificence of both the Ariel’s brakes cannot be exaggerated. The functionallooking full-width alloy front brake was fade-free, delicate in operation and completely trustworthy under hard application and in all circumstances.” The five-gallon fuel tank allowed almost 300 miles (480 km) to be covered between fuel stops.

The Mark II featured four separate exhaust pipes, two on each side, which emerged from handsome polished alloy manifolds and curved downwards to join a single muffler on each side. With high quality fuel becoming available, compression ratio was raised to 7.2:1, with power subsequently up to 42 bhp at 5,800 rpm. Carburation was now by a variable choke MC2 SU carburettor, fitted with an air cleaner.

However while the sporting Ariel singles gained a very effective new frame with swinging arm rear suspension, the Square Four soldiered on with the plunger/link design, and would do so until it reached the end of its production in 1958, by which time the UK price was £336/16/6 including the dreaded UK Purchase Tax. Indeed, this was the end of the line for all four-stroke Ariels, replaced by a new wave of two strokes headed by the Val Page-designed twin cylinder Leader.

The Square Four had a rebirth of sorts in the late 1960s, when the Healey brothers, George and Tim, produced the Healy 1000/4.

Tim had been drag racing a machine with a highly modified Square Four engine, and with what he and George had learned about making the engine work more efficiently (and stay together longer), they came up with the idea of their own complete machine. This used the MkII engine which had carefully thought out modifications to the lubrication system, including a separate oil filter in an Egli-type spine frame (made by Slater Bros in England) with the motor hung underneath.

Metal Profiles front forks and Girling rear units were used, with a huge Grimeca double sided front brake. The massive top tube of the frame carried the oil, and the improved lubrication and subsequent cooling allowed the compression ratio to be raised to 7.5:1, giving a 10% increase in power. The Healey brothers managed to carve around 60 pounds in weight from the original model, which further enhanced performance.

Inspired by their creation and buoyed by the interest it created from prospective buyers after its release at the 1971 Earls Court Show, the brothers abandoned their trucking business in the Midlands and moved to Reddich, near the old Royal Enfield factory, to concentrate on producing the 1000/4 as well as spares for other Squariels, but from 1971 to the end of the show in 1977, only 28 complete machines were built. Today, Healey 1000/4s bring big prices on the rare occasion one comes up for sale.

Interesting articles

Other articles of the category "Kawasaki":

Translation
Our partners
Follow us
Contact us
Our contacts

dima911@gmail.com

Born in the USSR

423360519

About this site

For all questions about advertising, please contact listed on the site.


Motorcycles catalog with specifications, pictures, ratings, reviews and discusssions about Motorcycles.