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).
Procedure for conducting low-temperature tests on accumulators using a lagged box with solid carbon dioxide.
| Identifier | ExFiles\Box 164\3\ img164 | |
| Date | 11th May 1938 | |
| LOW TEMPERATURE TESTS ON ACCUMULATORS. Our method of testing an accumulator at low temperature is to place it in a suitably lagged box containing solid carbon dioxide. When the temperature has fallen to the desired figure the test is taken, and this can be done without opening the box as the box is provided with current carrying leads and voltmeter leads which pass through the lagging. Provision is made for reading the temperature of the electrolyte in one of the cells, and this is taken as the temperature of the accumulator. A copy of our drawing No. G.1722 is enclosed to show the construction of the box. It is made of heavy gauge plywood with suitable re-inforcement of the base to carry the weight of the accumulator. A gas-tight joint is provided for the lid {A. J. Lidsey} by tightening down upon a rubber ring, and to avoid distortion angle-iron re-inforcement is fitted at the top of the box and on the lid. {A. J. Lidsey} A suitable lagging material is cotton linters, or alternatively "kapok" may be purchased from a local furniture stores. The interior of the box should be made gas-tight by dipping in wax, or by painting, as otherwise the heavy gas, carbon dioxide, which is given off as the solid material volatilises will find its way into the lagging, and much of the cooling effect will be lost. To measure the temperature of the accumulator a glass tube, sealed at its bottom end, passes through the lagged lid {A. J. Lidsey} and enters the electrolyte of one of the cells. A small quantity of mercury is put into the tube to make contact with the bulb of the thermometer, which is inserted in the tube. This arrangement avoids the need for obtaining a special thermometer with the graduations commencing several inches up the stem. An accurate thermometer, of normal design, can be used with this arrangement, it only being necessary to raise the thermometer quickly when a reading is required to ascertain the cell temperature. It is advisable to see that the bottom of the glass tube touches the top edges of the separators in the cell, and also to have the electrolyte level as high as possible, as during the long period of standing before the accumulator reaches the desired temperature the level of the electrolyte will fall considerably, and the glass tube may not be in contact with the electrolyte if these points are not taken care of. | ||