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).
The use of Wimperis Accelerometers for monitoring train safety on curves, with example acceleration graphs.
| Identifier | ExFiles\Box 113\2\ scan0019 | |
| Date | 14th November 1922 guessed | |
| 4 WIMPERIS ACCELEROMETER THE SAFETY OF HIGH SPEED TRAINS WHEN ROUNDING CURVES The vital necessity of watching closely the effect of speed when rounding either long or short curves has been brought out with special emphasis in recent years by several serious accidents, and few will question the utility of devices which can be made to indicate automatically the condition as regards safety of any piece of line. Such instruments are called "Equilibrists." The early forms of the instrument had the disadvantage that they did not write any permanent record of their survey of the line. No device of this kind can be regarded as adequately meeting the requirements of Railway Officers unless it can be made to give in a permanent form the result of the automatic survey which it makes of the state of the line—a record which shall be available for reference in the Railway Offices, and for comparison with records taken after any improvements in the track or in the train service have been carried out. Such comparisons are of especial use when the Permanent Way Department of the Railway is engaged in putting in transition curves—indeed, in work of this kind, they are almost essential if the success of the improvements is to be conclusively demonstrated. The needle of the Recording Equilibristat moves along the Zero line of the moving paper whenever the cant of the outer rail on a curve is exactly suited to the speed and the curvature of the line at that point. If the cant is one inch too little or one inch too much the needle will move to the right or the left as the case may be, until it reaches the one inch departure line ruled on the specially prepared paper. The paper is graduated in equal divisions representing inches of excess or deficiency in cant. An examination of such a chart in conjunction with the Speed Record (also obtainable from the Equilibristat) shows at once whether the speed of travel is suited to the cant, whether the cant begins at the right point in the curve, and whether the increase or decrease of cant is sufficiently gradual. If either the cant or the curvature of the line changes too rapidly, the Equilibristat needle will swerve across the paper and indicate the precise point in the track which needs attention. Tests carried out in this way over the same piece of track are found to give identical information about the track whatever be the kind of coach in which the instrument is placed during the test. On pieces of track which are not curved the instrument will bring to light any places where the rails are not at the same height—places sometimes known as "slacks." The earlier instruments were spirit levels in which the motion of an air bubble was carefully watched, but this, of course, gave no permanent record. Others worked on the principle of pendulums, either suspended from a point or rocking upon a surface. These were liable to oscillate on their own account and were difficult to control. They were also affected by any vertical up and down motion due to the unevenness of the track, or to the motion of the coach on its springs. None of these early attempts led to the introduction of any instrument sufficiently trustworthy to be adopted by railway officers. Very careful search was made, over a large range of years, by some of the large English Railway Companies for a satisfactory instrument for this purpose, but none was found until a few years ago when the invention described in the following pages was introduced. This invention was a joint product of a study of the subject by Mr. H.{Arthur M. Hanbury - Head Complaints} E.{Mr Elliott - Chief Engineer} Wimperis, M.A., M.I.E.E., and Mr. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} K.{Mr Kilner} B. Elphinstone, M.I.E.E., of the firm of Messrs. Elliott Bros., and the resulting instrument, known as the "Wimperis Recording Accelerometer and Equilibristat," is now in use on many Railway Systems. Graph 1: FT PER SEC² Labels: BALHAM, START, 'CELERATION, CHECKED BY SIGNAL BUT NOT STOPPED, FIRST PART OF BRAKING, SECOND, STREATHAM ACCELERATION CURVE FOR L.B. & S.C.RY STEAM TRAIN FIG. 3. Graph 2: FT PER SEC² Labels: KILBURN, WEST HAMPSTEAD, FINCHLEY ROAD, SWISS COTTAGE ACCELERATION CURVE FOR MET. RY D.C. ELECTRIC TRAIN FIG. 4. NOTE TO FIGS 3 & 4 THE SPACE BETWEEN TWO CONSECUTIVE CURVED ORDINATES REPRESENTS 5 SECONDS OF TIME Graph 3: FT PER SEC² Labels: OXFORD CIRCUS, PICCADILLY CIRCUS Axis: 0, 20, 40, 60, 80, 100, 120 SECONDS ACCELERATION CURVE FOR BAKERLOO TUBE RY D.C ELECTRIC TRAIN FIG. 5. Graph 4: FT PER SEC² Labels: QUEENS ROAD, OLD KENT ROAD Axis: 0, 20, 40, 60, 80 SECONDS ACCELERATION CURVE FOR L.B. & S C RY A.C. ELECTRIC TRAIN FIG. 6. Footer: ELLIOTT BROTHERS, LIMITED Established 1800. CENTRAL BUILDINGS, WESTMINSTER, LONDON, S.W., AND CENTURY WORKS, LEWISHAM, LONDON, S.E. | ||