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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).
Proposed test procedure for different clutch part assemblies on a dynamometer rig.

Identifier  ExFiles\Box 74\2\  scan0232
Date  28th June 1929 guessed
  
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Proposed Test.

Will you now help us to arrange as soon as possible an accurate test as follows:-

(1) On an engine on unit dynamometer arrange for assembly of the clutch parts in four different forms:-
(a) Standard with Ferodo.
(b) Standard with Johns Manville white clutch lining.
(c) Fabric on driven disc with Ferodo.
(d) Fabric on driven disc with Johns Manville.

The fabric to be in continuous uninterrupted rings on all four assemblies.

The clutch cover to have four 3" "ventilation" holes on the face to allow insertion of "Motometer" to give temperatures inside clutch.

(2) Take the depth of the 8 recesses for clutch springs and read on the spring test balance the exact load produced in each recess on each spring assembly. Stamp this load on each spring assembly. (Check this after each test in case of any softening of springs from heat.)

(3) Engine to be fitted on water-pump spindle with an engine "tachometer" of the type fitted by Maintenance Department.

This tachometer must be calibrated against the accurate speedometer on the dynamometer unit, and a calibration chart made.

(4) Conduct each test as follows:-
(a) Remove opposite clutch springs until the clutch will just slip with a known total clutch spring load at about 500 RPM.

Slipping is shown by a difference in reading between engine tachometer and the speedometer on the rig.

Read the torque and clutch spring load at which slipping takes place. Also room temperature and temperature inside clutch. Coefficient of friction is then given by -

(2 x Total clutch spring load - 30) x 6.125 x coeff. fric. = torque.
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(b) After say five and ten minutes slipping under these conditions, repeat above readings. Control the throttle opening and dynamometer load during this test to keep the relative engine and dynamometer speed as constant as possible.

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