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).
Article from THE AUTOCAR magazine detailing how to build a simple electric timing set.
| Identifier | ExFiles\Box 138\2\ scan0031 | |
| Date | 28th November 1924 | |
| PLEASE FILE UNDER CHRONOGRAPH M4630 THE AUTOCAR, November 28th, 1924. 1097 AN ELECTRIC TIMING SET. How a Reliable and Accurate Electric Timing Apparatus Can be Simply Made at a Cost of a Few Shillings. By H.{Arthur M. Hanbury - Head Complaints} Mortimer Batten. A GREAT deal of interest can be obtained from an accurate electric timing apparatus, quite apart from its indispensable use in obtaining split second results of fast-moving vehicles over short distances. The apparatus here described is the result of much experience along the same lines in photographing wild animals electrically, and, incidentally, experience of this kind often goes to prove how hopelessly slow and inaccurate human fingers are compared with automatic electric machinery. For example, it is often a hopeless task to photograph by hand some rapidly moving animal, such as a weasel, in the precise moment, so it seems, but on developing the plate it is found that the animal had moved quite considerably ere the exposure occurred. As affording a comparison—the writer has not uncommonly run two cameras in series for the purpose of obtaining two separate pictures of the same animal on its touching the contact plate. In this case, No. 1 camera was tripped electrically, but not until the exposure was complete—that is, the shutter-operating mechanism at the end of its stroke—was the current shunted over to No. 2 camera, so that one might expect a pause sufficient for the animal to alter its position slightly between the two exposures. But nothing of the kind. Both cameras would show the wild subject in precisely the same pose, with not the width of a hair difference between the two, though to the human onlooker it seemed that instantly No. 1 camera clicked, the animal was away like a streak, and quite out of the field of focus when—a perceptible interval later—No. 2 camera was heard to operate. Human and Electric Agency Compared. Experimenting on these lines, I designed and made the simple electric timing apparatus illustrated herewith, and proceeded to test its accuracy for my own amusement by dint of photographic proof. The camera was wired up to the electric apparatus in such a way that the circuit was closed upon it and the photograph taken by the same arm that operated the stop watch—that is, so that the photograph occurred at the precise instant that the watch started. For the purpose of the tests a broad white tape which would show in the photograph was used, the object being to compare the accuracy of the human agency with that of the automatic electric apparatus. Therefore, in the first series of tests, a bell push was used in circuit with the apparatus, and instantly the car broke the tape this was operated by hand. A dozen plates were exposed, and the results varied considerably. In some the car was apparently seven or eight feet on one side or the other of the tape—that is, either the car had not nearly reached it, or it was some feet beyond and the tape severed. It should be mentioned that the line was crossed at a speedometer reading as near to 54 m.p.h. as possible. In none of these tests was the car actually in the process of breaking the tape. In the second series of tests the camera was left wired up to the timing apparatus as before, but the closing of the first circuit was actually done by the car as it broke the tape, and by dint of the simple contact maker shown in fig. 2, so that the human agency was ruled out. Again, a dozen plates were exposed, and every one of these showed the tape flying wildly asunder, and the car occupying precisely the same position on the field of focus. This, then, proved definitely that the human agency was not to be compared with the mechanical agency for accuracy; it further proved that the apparatus was as accurate and consistent as anything we can hope to arrive at. Costly Apparatus. In these days many motoring clubs have their own electric timing apparatus, which is quite automatic, and generally beautifully made and ingenious to a degree. It has, however, always seemed to me that such an outfit is, as a rule, unnecessarily complicated, and consequently not always reliable, while £20 to £30 is nothing to pay for even the less elaborate sets. My own instrument certainly cost under 5s., not including the watch and accumulator; it is easily made, and if constructed with care is absolutely reliable. The only way in which it falls short of the more elaborate plant is that one is compelled to stand by it, and to reset the instrument during the intervals while the test is being made. It may be added that the amount of current used in the operation of an apparatus of this kind is exceedingly small. It uses infinitely less than is required to ring an electric bell. With a similar apparatus a pocket flash-lamp battery will operate the mechanism through 100 yards of ordinary, cheap bell wire, and I have used the same battery for the purpose all one su--er. A 4-volt 10-amp.-hour accumulator should be adequate for all ordinary purposes, though I have not tested it over more than 200 yards. It should be observed that the apparatus is designed to form the lid{A. J. Lidsey} of the accumulator box. Fig. 1 Showing the construction and wiring of the electric timing apparatus. DIAGRAM LABELS: LOCK SPRING STOP WATCH SPRING CLIP HOLDER BELL COILS TWO-WAY SWITCH WIRES TO CONTACT MAKER AT BOTTOM OF HILL WIRES TO ACCUMULATOR PIVOTED ARMS ARMATURE WIRES TO CONTACT MAKER AT TOP OF HILL FOOTER: D 9 B 17 | ||