The Final Featherbed: 1967 Norton Atlas
By Robert Smith
1967 Norton Atlas
Claimed power: 49hp @ 6,800rpm
Top speed: 110mph
Engine: 745cc air-cooled OHV parallel twin, 73mm x 89mm bore and stroke, 7.6:1 compression ratio
Weight (dry): 395lb (180kg)
Fuel capacity: 3.2gal (12ltr)
Price then/now: $1,050(est.)/$4,000-$12,000
Not many production motorcycles are notable for the frames they use.
Apart from Norton’s famous double-cradle frame from 1950, I can think of only Lino Tonti’s long-running design for Moto Guzzi and Miguel Angel Galluzzi’s trellis frame for the Ducati Monster as defining each model. (Though Philip Vincent’s Series B, which had no frame at all, certainly warrants a mention!) But perhaps only the Featherbed has achieved legendary status.
It’s a well-known story, but it bears repeating. During World War II, Cromie McCandless and his brother Rex owned an engineering company in Belfast, Northern Ireland. Rex was also one of the best known and most successful motorcycle racers in Ireland, but was dissatisfied with the lack of suspension in the rigid-rear frames fitted to most motorcycles at the time. Thinking that motorcycle frame design had been left behind by the increases in engine power, McCandless designed a rear subframe that incorporated a swingarm and spring/damper units from a Citroen car. He fitted it to his race bike, and it worked. Before long, competitors started inquiring about his rear frame. After partnering with fellow racer Artie Bell, McCandless began offering conversion kits and modifying frames for other riders.
In the early postwar years, reports of the McCandless conversion and its racing successes reached the mainland, eventually attracting the attention of Norton’s managing director, Bill Mansell. Working under contract to Norton, McCandless was able to devote his time to developing a new frame for the Norton Manx to replace the unstable and crack-prone “Garden Gate” plunger frame. What McCandless came up with was an elegant dual-cradle, steel tube frame in which two continuous loops encircled the engine with ample triangulation at the head stock. It was light, rigid and strong, and with McCandless’ rear suspension and Norton’s own Roadholder fork fitted, it provided outstanding handling.
Successful testing was carried out at the Montlhery circuit in France and at the Motor Industry Research Association’s test track in England. It was at the Silverstone track in 1950 that works racer Harold Daniell made the now famous comment that the new McCandless Manx was like riding on a “feather-bed.” The name stuck.
The racing Featherbed frames were rather special, being made up from Reynolds 531 high-tensile tubing that was SIF-bronze welded. When the Featherbed was introduced on production machines it was made from mild steel, with the rear section bolted in place. But the Featherbed frame endured for close to 20 years on numerous Norton models with only two major changes: from the “wideline” design, which used straight tubes for the top frame rails, to the “slimline,” in which the top tubes were necked in at the front of the seat for a more comfortable ride; and from the bolted-on rear section to a fully welded frame.
The first street Norton to get the new frame was the Dominator 88 500cc twin, developed from the plunger-framed Model 7. However, the Featherbed frame, which was always manufactured at Reynolds under the supervision of frame guru Ken Sprayson, was much more expensive to make than the Model 7’s, so only export markets (especially the U.S.) got the new frame at first.
The Dominator 88’s engine was essentially Bert Hopwood’s 1949 overhead valve parallel twin, with a 66mm bore and 72.6mm stroke and modest 6.7:1 compression. Fed by a single 1-inch Amal carburetor, the 88 produced 29.5 horsepower at 7,000rpm and was good for 92mph. The cylinder block and cylinder head were each single castings in iron. The crankshaft was built up from two separate halves bolted together through a central flywheel and running on a drive-side roller and timing side ball bearings. The light alloy connecting rods had split big-end caps with plain bearings. The single camshaft was located at the front of the engine with chain drive from a half-time gear. The hemi-heads were arranged with parallel intake tracts and widely splayed exhausts for better cooling. Drive to the Norton/Sturmey-Archer 4-speed gearbox was via a single chain and multiplate clutch.
The 88 garnered high praise from testers, especially for its handling, comfort and sharper performance than the Model 7 because of its lighter weight. But that didn’t prevent Norton running into financial problems, and in 1952 Associated Motor Cycles bought the company. Initially, not much changed except that Norton no longer fielded a full Grand Prix team. The 88 benefited from a larger 8-inch front brake in 1954, and a light alloy cylinder head and an Amal Monobloc carburetor in 1955, when it was joined by the Dominator 99. This used a 596cc engine with dimensions of 68mm x 82mm. With a 7.4:1 compression ratio and 1-1/16-inch Monobloc carb, the 99 produced 31 horsepower at 5,750rpm and would top 100mph. In 1956, the gearbox of both models was changed to the AMC type and an improved clutch was installed.
1960 saw the introduction of semi-enclosed “de luxe” versions of the 88 and 99 (a fashion of the time, like Triumph’s “bathtub” enclosures), while the Featherbed frame was modified to improve ergonomics by bringing the top tubes closer together at the front of the seat (the “slimline”).
It was likely the arrival of Triumph’s Bonneville 650 in 1959 that prompted Norton’s next move. While the 99 had been close to the Tiger 110 in performance, the new T120’s 46 horsepower gave it a significant edge. So for 1961 Norton presented super sport “SS” versions of the 88 and 99, with new downdraft-intake cylinder heads, dual Amal Monobloc carbs and higher compression (8.5:1 and 8.25:1, respectively) for 36 horsepower at 7,000rpm and 44 horsepower at 6,750. The 600cc 99SS lasted just one year before it was replaced by a full 650cc sports machine, the 650SS. The extra capacity was obtained by lengthening the stroke to 89mm, a dimension that would remain in all production Norton twins until the last Commando. Fitted with dual 1-1/16 Amal Monoblocs and 8.9:1 compression, the 650SS claimed 49 horsepower at 6,800rpm. Road testing gave top speeds of over 100mph for the 88SS, 108mph for the 99SS and approaching 120mph for the 650SS.
Enter the Atlas
Also new in the 1961 lineup was an even larger version of the twin, using the same 89mm stroke as the 650SS but with the bore enlarged to 73mm for 745cc. The Atlas was intended for the U.S. market, so it was tuned for a broad powerband rather than outright power. Piston crowns were dished to reduce compression to 7.6:1, and with its single 1-1/8 Monobloc carb the Atlas produced 49 horsepower at 6,800rpm, the same as the 650SS, but in a more relaxed manner. Other differences between the 650SS and the export Atlas included a smaller capacity 3.2-gallon (U.S.) gas tank, high handlebars, chrome fenders and fatter tires; 3.25 x 19 inches and 4 x 18 inches on the Atlas instead of 3 and 3.5 x 19 inches on the 650SS.
In 1962, AMC closed Norton’s old Bracebridge Street premises in Birmingham, moving production to the Plumstead, London, factory that originally housed Matchless. The Matchless influence manifested itself through the 1960s in a range of hybrid machines using the Atlas engine in AMC running gear — but that’s a whole other story. Further rationalization of the large-capacity Norton range followed, leaving just the 650SS (voted Machine of the Year by Motor Cycle News readers in 1963 and 1964) and Dominator 88SS in the home market range. The Atlas continued for export only — until 1964.
The U.K. market Atlas was different from the export model, with dual Amal Monobloc carbs, a larger gas tank, and flat handlebars. It was finished in black and chrome like the 650SS. All Atlases now had 12-volt alternator electrics, but retained magneto ignition (though battery-optional capacitive discharge coil ignition was introduced in 1967). Testers at Motor Cycle News enjoyed the relaxed cruising at highway speeds offered by the big twin, but they also noted intrusive vibration above 4,500rpm. The Motor Cycle News’ tester liked the top speed of around 110mph, with fuel consumption of close to 40mpg (U.S.), but they also noted vibration around 5,000rpm, although the bike’s tall gearing meant this wasn’t an issue at cruising speeds.
It wasn’t Norton’s motorcycles that were making the news in 1966, though. AMC went into receivership and was purchased by Villiers Engineering parent company Manganese-Bronze, the new motorcycle pision operating as Norton-Villiers. It was the end of the James and Francis-Barnett marques, though Matchless- and AJS-badged machines with Norton engines continued into 1968. By that time there were just two Nortons left on sale with the Featherbed frame: the Atlas and a single-carburetor 650cc machine, the Mercury. And there was a new kid on the block, still using what was essentially the Atlas engine, but in a completely new spine frame with rubber engine mounts: the Commando.
Colin Kelly’s Atlas
Colin Kelly is a dedicated fan of Norton Featherbed twins. A few years back, he rode a 650 Mercury across Canada from Vancouver to Toronto on his way back to his native England. Now settled back in British Columbia, Kelly has built a reputation for concours level Commando restorations — but he had never tackled an Atlas. Three years ago, Kelly was able to trade a Commando project bike for a 1967 Atlas that had been parked outside in the Pacific Northwest’s wet climate and allowed to deteriorate. On the front fender was a decal, “Port Alberni Toy Run 1993.” Kelly remembered taking part in the same ride and seeing the Atlas, which was then in mint condition, with the gas tank painted in British Racing Green. It was “a little different to the sad-looking rusty heap that I now had,” Kelly says.
The good news is it was an all matching number bike (frame, engine and gearbox), making it the perfect base for a restoration. Even better, when stripping the engine, Kelly found the original dished low-compression pistons running in cylinders that had never been rebored. The crankshaft journals were also stock size, so Kelly concluded it had relatively low miles. On the downside, the primary chain had let go at some time, making a mess of the case, and the sheet metal parts were in rough shape. But the chassis, fork, wheels and gearbox were in good condition. Kelly decided he could build a concours-winning Atlas from the 1967 model, using donor parts from a basket case 1966 Atlas and a crashed 1968 Mercury. “I find that because of the Atlas’ bad reputation (for vibration), very few are built to this standard,” Kelly says.
He set to getting parts powder coated and chromed, and degreased the engine and gearbox. After inspection, the cylinder head was bead blasted and the engine and gearbox cases were cleaned with bronze wool to preserve the sandcast finish.
Kelly was also able to re-use the stock dished pistons after honing the cylinder bores and fitting new piston rings. And he had on the shelf a brand-new set of Jones chrome wheel rims (Dunlop and Jones supplied most of the wheel rims used on British motorcycles up to the 1970s). 1967 was a crossover year for the Atlas, and while Kelly’s ’67 retained its original Lucas K2F magneto and Amal Monobloc carburetors, Kelly opted to go for the late-1967 model year battery/coil ignition setup, and fitted new Amal Premier Concentric carbs.
“Strictly speaking, the gas tank should be cherry red for 1967,” Kelly says. “Black was an option for 1966. l wanted the bike to stand out and be different, so I went for black.” The Commando-style twin-leading-shoe front brake was also an option for the 1967 Atlas. “I now had a growing pile of mint Norton parts ready for assembly,” Kelly says. “l was very careful with attention to detail with small things, like using brass ferrules instead of screw clips for the rubber oil and gas lines.” Among the more difficult parts to find were the 1-5/8 inch exhaust headers. Kelly bought the last stock pair at RGM Norton in Cumbria, U.K. (rgmnorton.co.uk) “I had the bike on its wheels in late January 2017,” Kelly says. “Now I had a running machine. The dished pistons were a real plus. The lower compression gives the engine a lazy feel and it pulls strongly from 2,000rpm without laboring. This definitely counters the infamous Atlas vibrations, which are still there as the revs increase, but feel a lot tamer. As far as l know the dished pistons are not available from any parts supplier.” Most Atlas restorers are stuck with using the flat-top Commando pistons, which work perfectly but have higher compression — which increases engine vibration.
Kelly’s Atlas won both Best in Show and Peoples’ Choice awards at the Classic & Vintage Motorcycle Show ’n Shine in Cloverdale, B.C., in April 2017, and Kelly plans to show the Atlas at the International Norton Owners Association rally in Washington state in 2018. MC
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