Norton Model 7 Dominator
 Model 7 Dominator swinging arm version | |
| Manufacturer | Norton |
|---|---|
| Production | 1949-1953 |
| Assembly | Bracebridge Street, Birmingham |
| Successor | Norton Model 88 Dominator |
| Engine | 497 cc (30.3 cu in) air-cooled OHV vertical twin |
| Bore / stroke | 66 mm (2.6 in) x 70.6 mm (2.78 in) |
| Compression ratio | 6.7:1 |
| Top speed | 95 mph (153 km/h) |
| Power | 29 bhp (22 kW) @ 6,000 rpm |
| Ignition type | Lucas magneto |
| Transmission | Wet clutch, 4-speed, chain drive |
| Suspension | Front: telescopic forks Rear: (1949-53) plunger, (1953-55) swinging arm |
| Brakes | 7 in (180 mm) drum front & rear |
| Tires | (1949-53) 3.00x21 front, 3.50x21 rear (1953-55) 3.25x19 front, 3.50x19 rear |
| Wheelbase | 54.5 in (1,380 mm) |
| Dimensions | L: 84.5 in (2,150 mm) W: 28 in (710 mm) |
| Seat height | 31 in (790 mm) |
| Weight | 413 lb (187 kg) (dry) |
| Fuel capacity | 3.75 imp gal (17.0 L; 4.50 US gal) |
| Footnotes / references [1][2][3][4][5] | |
The Norton Model 7 Dominator was a 500 cc vertical twin motorcycle manufactured by the Norton Motorcycle Company from 1949 to 1955. It was the first of Norton's Dominator range of motorcycles. The engine was designed by Bert Hopwood and was a departure from Norton's previous practice of producing single-cylinder machines.
Engine and transmission
Having worked under designers Val Page at Ariel and Edward Turner at Triumph, where he assisted with the design of the Triumph Speed Twin, Hopwood was poached by Norton to design a new twin engine.[6]
The engine had a 360-degrees built up crankshaft with central flywheels. This arrangement meant that a central main bearing could not be fitted. The outer main bearings were of ball bearing on the timing side and roller bearings on the drive side. Alloy conrods were split at the big end and used a bush for the big end bearing. The camshaft was fitted in front of the engine, driven by a chain off a half speed pinion. For ignition a Lucas magneto was fitted at the rear of the engine and to supply power for the lights a dynamo was fitted at the front of the engine. Both were driven by chains.[2][3][4][5]
The cylinder block was in cast iron and had an integral push rod tube. Cast iron was also used for the cylinder head, which had cast in rocker boxes to eliminate potential oil leaks between head and rocker boxes. A shallow combustion chamber, combined with low included angle valve configuration and flat top pistons gave a good swirl effect. The head had widely splayed exhaust ports to aid cooling. A single Amal carburettor fed fuel to the engine through an alloy manifold. (om the show model the manifold was part of the head casting.[2][3][4][5]
The engine used a traditional long stroke with a bore and stroke of 66 mm (2.6 in) x 70.6 mm (2.78 in) and produced 29 bhp (22 kW) at 6,000 rpm.[2][3][4][5]
Primary drive was by chain to a wet clutch and was enclosed in a pressed steel chaincase. A new 4 speed "lay-down" gearbox was fitted. Final drive was by chain.[4][7]
References
- ^ "1953 Norton Brochure" (PDF). Retrieved 12 June 2021 – via www.classicbike.biz.
- ^ a b c d "1951 Norton Model 7". Classic-British-Motorcycles.com. Retrieved 12 June 2021.
- ^ a b c d "Norton Model 7". Classic-British-Motorcycles.com. Retrieved 12 June 2021.
- ^ a b c d e The 497 cc Vertical Twin Model 7 "Dominator" Norton. Motor Cycling Magazine. 31 March 1949. pp. 430–432 – via WALNECK'S CLASSIC CYCLE TRADER, JUNE 1999.
- ^ a b c d Smith, Robert (29 May 2013). "Comparing the BSA A7 and Norton Model 7". Motorcycle Classics. Retrieved 12 June 2021.
- ^ Tinworth, Bruce J (2021-03-03). "Norton Dominator: an Australian investigation. Part I". RealClassic. Retrieved 13 June 2021.
- ^ Urquhart, Stuart (1 October 2016). "Norton Model 7". RealClassic. PressReader.com. Retrieved 13 June 2021.