| MODEL | VELOCETTE SUPERCHARGED 500 1939 |
| Year | 1939 |
| Engine Type | Parallel twin, OHC, supercharged; two crankshafts geared together, shaft and bevel camshaft drive |
| Displacement / Capacity | 500 cc |
| Bore X Stroke | — |
| Compression Ratio | — |
| Cooling System | Designed as liquid cooled; air-cooled heads and barrels fitted for the TT |
| Max Power | — |
| Max Torque | — |
| Ignition | Magneto |
| Induction | Supercharger |
| Start System | — |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4 Speed, in unit with engine |
| Clutch | — |
| Final Drive | Shaft |
| CHASSIS SPECS | |
| Frame | Duplex cradle |
| Front Suspension | Webb T.T. girders with single compression spring and friction dampers |
| Rear Suspension | Pivoting (swinging) fork |
| Front Brakes | — |
| Rear Brakes | — |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | — |
| Rear Tyre | — |
| FUEL SYSTEM | |
| Fuel Capacity | — |
| Fuel Consumption | — |
| Top Speed | — |
Built as a 500 cc racer for the 1939 TT, the Roarer was effectively two 250 cc singles side by side with counter-rotating crankshafts for near-perfect balance, one of which drove a supercharger. Drive went through a unit four-speed gearbox and shaft to the rear hub. War began soon after its only practice outing, and postwar rules banned blowers.
