Allard – Wade “roots” type supercharger unit suitable for supercharging internal combustion engines, either petrol or diesel, ranging in capacity from 1000 – 5000 cc, depending on air flow and / or boost pressure required.

These units have been specially adapted for automobile use, where high r.p.m.'s are necessary. The smaller of the two supercharger units, the RO20, has a capacity of 2000cc per revolution and is normally fitted to engines ranging from 2000-3000cc, when a boost pressure of between 5-8.0 psi is required.

The larger RO34 Allard-Wade supercharger unit is a longer version of the RO20 unit, thereby increasing the capacity to 3400cc per revolution and making it suitable for engines ranging in capacity from 3000 – 5000cc. Where a boost pressure of above approx. 8.0 psi is required, such as for competition use, then these units can be successfully mounted onto smaller engine capacities. (For example the RO20 supercharger fitted to a 1300cc engine with a drive ratio of 1:1.0 will supply a maximum boost of up to 18 psi.)

The Wade supercharger is a roots type blower with directly opposed inlet and outlet ports, employing two parallel alloy rotors each with three lobes, mounted on a ridged steel shaft supported by a ball and roller bearing at either end. The drive is transmitted from the driving rotor to the driven rotor via single helical phasing gears. The case which contains the rotors is an aluminium alloy die casting. The two housings, which supports the bearings at each end are also aluminium alloy die cast. The three-lobed rotors are of all-aluminium construction, the shaft of high tensile steel being press-inserted into the centre hole of the 4 hole extrusion forming the lobes.

The gears are single-helical pattern, the driving gear of alloy steel being mounted directly onto the rotor shaft by straight sided serrations. The driven gear of phosphor bronze is bolted onto a steel hub which in turn is mounted onto the rotor shaft. Provision is made for angularly displacing the bronze gear on its hub so that the two rotors may be correctly phased.The seals between the case and the bearings are designed to prevent lubricating oil seeping into the air stream. The seals themselves are sintered iron sleeves provided with labyrinth grooves and run with a fine clearance in the tunnels of the end housing. There are on sliding contacts in the seals. The bearing supporting the rotors are of the single-row deep groove ball journal pattern for axial location and of the single-row parallel roller pattern for resisting the tooth pressure of the gears. Whilst every care is taken in the preparation of this information, we cannot accept responsibility for any inaccuracies or omissions. The supercharger is built to very high standard with close tolerances. There being a minimum rotor tip clearance of.004” with the rotors centrally placed and a mesh clearance of .006” with all the backlash taken up. Maximum recommended rotor speed is 6,500 rpm but for continuous rating and use 6,000 rpm is the maximum advisable. For the larger unit the corresponding figures are 6,000 and 5,500 rpm respectively. Due to the high percentage of light alloys used in the construction of these units. The RO20 type only weighs 40lbs. And has a rated capacity of 2,000cc per revolution giving a maximum airflow of 350 cu. Ft. per min at 6,000 rpm. with a pressure of 2.0 psi.

Mounting of the supercharger

The supercharger drive shaft must be mounted parallel to the axis of the engine crankshaft, but the casing can be rotated around this axis to any position, but preferable where it is possible to fill and check the oil level, retained in the end housings to lubricate the gears. ( See section on lubrication )

The supercharger is normally bolted to the engine by means of steel or alloy mounting brackets attached to at least four of the 1/4” bolts at either end of the casing. If it is not possible to mount the supercharger with the drive shaft in line with the crankshaft pulley ( from where the blower is to be driven ) then a drive shaft extension can be fitted, but this must be supported at its outer end.

Lubrication

Lubrication is required for the rotor drive gears in each end housing. There are four brass plugs fitted to each end housing and depending on the position of the supercharger, should be used to fill and check the level of the lubricating oil. Oil used is normally 20-50 engine oil and the chamber should be filled to approx. 1/4” of its total capacity. Under normal circumstances the oil should be checked and topped up every 450-500 miles.