An Interesting New Supercharger
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Important Claims Made for Centric Blower—A Novel Design That Appears to be Thoroughly Sound According to Mechanical Principles
(IF the conventional rotating-valve type, and constructed
in a manner that should minimize frictional losses, heavy oil consumption and unreliability, a new supercharger has been recently introduced by Centric SuperChargers, Ltd., Ribble Bank Mills, Bow Lane, Preston, Lancs. The accompanying drawing shows the device in its latest form for engines of large capacity. It is also made to a somewhat simpler design, in which the vanes revolve about a fixed spindle mounted in the end of the main casing.
There are four vanes, each running on its own pair of ball bearings and being free to turn independently of the others. Every one of the eight vane carriers, which are symmetrically arranged in pairs, incorporates a balance weight, so that no bearing is subjected to appreciable radial loading. Distance pieces between the inner races of the bearings locate the vanes laterally. Thus the clearance between the vanes and the casing at their ends and outer edges can be reduced to the minimum. In practice, 0.001 in. has been found to be adequate.
The vanes are driven by a hollow rotor, running on roller bearings, placed eccentrically with the vane spindle and itself driven by internal gearing from the central shaft. Equally spaced around its circumference are four slots running parallel with its axis and of circular section. In these work trunnions, of hard fibre, likewise slotted to B2(I receive the vanes. Thus the only sliding motion is that of the vanes in these trunions.
Lubricant is fed into the hollow vane-shaft, whence it flows from a series of small holes to the ball bearings; and is then flung on to the vanes and trunnions.
This apparatus should be capable of running at high speeds for protracted periods. Every part is balanced, and the continual changes in angular velocity of the vane-andcarrier units should not be sufficient to cause excessive stresses or loadings on the parts concerned. Furthermore, the vane-bearing speeds are low.
A Centric supercharger suitable for an engine of 1.5-litre capacity weighs under 20 lb., is 8 ins, in diameter and 10 ins, long overall. It will deliver mixture at a pressure of 7 lb. per sq. in.