Brake Tests

140 (G) Minimum expense of maintenance and “running repairs” of the brake rigging between shopping of cars, for the purpose of expediting train movements. (H) The parts to be designed so that they cannot be applied improperly, for the purpose of minimizing the possibility and probability of making wrong repairs. (I) The initial and maintenance cost to be as low as consistent with, but secondary to, the points mentioned above. 304. (A) Precaution against parts dropping on track can best be exercised by:— (a) Designing the rigging so that it will not have to be disconnected for adjustment, thereby reducing to a minimum, chances for the members becoming disconnected through failure to prop- erly replace pins, bolts, nuts, cotters, etc., after adjustments are hurriedly made. (b) Providing suitable safety supports for the parts most likely to become disconnected while car is in motion. 305. (B) Maximum brake rigging efficiency can be insured only by having the moving parts as free from resistance, due to friction, as possible and by having all members of the brake rigging so designed and located that the losses in the transmission of the forces through them will be reduced to a minimum throughout the range of variations caused by wear in trucks, wheels and shoes. This requires ample pin bearing but where large diameter pins are used they should be confined to equalizers. Members in compression are to be avoided, but where unavoidable they should be subjected to minimum loads, be of minimum length and if possible one end anchored to a fixed point. The three forces acting on any lever should always lie in the same plane. Proper attention must also be given to the location of hangers in order to insure satisfactory release of the brakes without the aid of springs. Any features in the rigging which tend to lengthen the time required to transmit the pressure from the brake cylinder to the brake shoes is especially detrimental to the over-all efficiency of the rigging, for the reason that this lag in obtaining the shoe pressure occurs at the time when the vehicle is running at its maximum speed. 306. (C) To insure uniform distribution of brake force (in relation to weights braked), the shifting of wheel weights should be limited to that caused by inertia forces and unavoidable longitudinal shocks. This necessitates: (a) Locating the shoes and brake beam hangers of clasp brake, so that the influence of the hangers on the shoe pressure will be the same for all wheels, allowing, however, sufficient inclination of the hangers to insure a satisfactory release of the brake.