From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Secret memo describing an improved EAC clutch with a new damping mechanism and other modifications.
| Identifier | ExFiles\Box 66\4\ scan0020 | |
| Date | 15th May 1925 | |
| TO BY.{R.W. Bailey - Chief Engineer} FROM AJS. S E C R E T. X8300 Mis S 15 AJS2/M15.5.25. Copy to GJ. HS.{Lord Ernest Hives - Chair} IMPROVED EAC. CLUTCH. We send herewith drawing LeC. 2067. shewing a clutch incorporating an improved form of damping, in place of the 4 sprung pads used on the moveable ring hitherto. In the improved form the damping consists of arranging the plate which abuts on the rings of ferodo with a set of 4 springs, each of which exerts 40 lbs. in position, and holds this plate against 4 symetrically placed stops in such a way that the last 10 to 25 thous. of travel of the clutch ring when making engagement is used in compressing the springs referred to until the flywheel ferodo carrying plate abuts solid with the face which eventually supports it. The distance through which the clutch moveable ring travels in compressing the 4 springs is determined by the thickness of the plate upon which the flywheel ferodo is mounted. Our drawing shews about .015 between the ferodo plate and stop. We consider that in making the initial experiments with this new form of damping device this clearance should be .010 and be increased only if found necessary to the minimum amount required to prevent the clutch plate jaggering. It should be noted that with this new arrangement of damping that the clearance in which the clutch brake may be adjusted is increased, giving a wider margin for adjusting the position of this latter device. On this drawing we shew an aluminium centre piece for the universal joint portion of clutch in place of the steel drop forged one for lightening purposes, and further for lightening the flywheel and decreasing its inertia to a certain extent we have taken a considerable amount from the rear of the rim, and eliminated the necessity of end milling the quadrants between the lever guides used hitherto, the guides being abandoned in favour of controlling the lever by a longer fulcrum pin in bearings placed further apart. It is intended that this fulcrum pin should be a piston pin fit in the clutch lever, and just an easy fit in the outer lugs which are machined from the solid forging as indicated on the drawing. The inside diameter of flywheel and clutch parts are slightly increased making the ferodo slightly narrower in width, and incidentally increasing the effective friction radius of it. The clutch spring units are now somewhat altered from those hitherto used in being longer, to make up for the amount removed from flywheel, and owing to our desire to fit the clutch disc retainers and flywheel ferodo plate stops on the one joint facing, it has been necessary to increase the amount which the spring units extend to when free, in order that they may press the clutch disc on to the retaining plates, and so square up and hold in position the disc and centre unit. (1) | ||