J. J . WALKLATE. J

43

H.— 2l;

throughout the system. i therefore consider that any special car for working that route is not feasible. The Parnell Rise.never troubles me: it is short and straight, and there is a landingplace. We have never had any trouble on that line. It happens to be an exceptionally severe gradient. In the potteries the hand-brake is used as a service brake, and the pneumatic slipper brake is exclusively used as an emergency brake. The Chairman. —We should like the evidence of the motormeu in charge of the car when this skidding eventuated, and the emergency had to be used. 1 think it was a car fitted with an air brake the first day out. Commission adjourned till Thursday.

Auckland, Thursday, 21st April, 1910. Commission resumed at 2.15 p.m. Mr. Myers stated that the man who had driven the car was not now r in the company's service, and had left Auckland, so they understood, but that the company would do its best to trace him.. William: George Toop Goodman, M. Inst, C.E., M.1.E.E., M. Amer. E.E., duly sworn. Examined by Mr. Myers :My name is William George loop Goodman. I am a civil and electrical engineer. lam at present Chief Engineer and General Manager of the Adelaide tramways, and came for the purpose of giving evidence on this Commission. 1 have been an engineer for twenty years. I have had special experience in tramway-construction and the working of electric tramways—that is my specialty 1 have had considerable experience in tramways, and have constructed a portion of the Sydney trams, the Dunedin tramways, and now the Adelaide tramways. I have been responsible for the design and the whole undertaking of the electric trams in Dunedin and Adelaide, and a considerable portion of it in Sydney. I have had very considerable experience in the working of the magnetic brake, I suppose more than any other man in Australia. I was the first to adopt the magnetic brake. I have had some experience in the working of the air brake in Sydney. I had experience in the working of the tram system in Sydney during the construction that was going on on other portions of the line, and I paid close attention to the working. After the construction of that portion in Sydney was finished I resigned the service. My experience of the actual working of the air brake is limited to Sydney, with the exception of severe and extensive tests which I made in America. I had similar tests with the magnetic brake there in Pittsburg. I did not have to do the designing or construction there. My reason for making the experiments was in order to enable me to arrive at a decision as to what was the best brake to adopt for those tramways; and we adopted the magnetic brakes. I have an exceedingly good opinion of the Newell magnetic brake—in fact, I am known as the " magneticbrake man." That does not imply that 1 consider the Newell magnetic brake is the proper brake under all conditions. The Adelaide district and the Dunedin district, having regard to the gradients and general conditions, are not in any way comparable with the Auckland district. The principal reason is that the topographical conditions in Adelaide and Dunedin are different from what they are in Auckland —that is to say, they have very severe gradients here that do not obtain in either of those two places. I carried out very extensive experiments in Glasgow in order to see if I got the same results as I obtained in Pittsburg. I think the Newell magnetic brake, under suitable conditions, is the very best form of brake I know of. You want conditions where you have not to negotiate heavy grades. Where you have heavy grades it is necessary to have a brake which you can use on the down grade continuously ; and w r ith the magnetic brake, by continual coasting thereon, it throws very excessive and heavy stresses on the motors. Now, where you have the down gradients you also have to climb the up grade, and when climbing the up grades the work done by the motors is exceedingly heavy and severe, and consequently that heavy work causes the motors to heat to a large extent, and unless the capacity of the motor is such that the heat generated can be easily dissipated, then you want the motors free on the down grades in order to allow the motors to cool. In other words, I mean by that, that with the magnetic brakes, unless you have sufficient capacity in the motors, it is inadvisable to coast on the down grades, because you are throwing extra work on the motors which they are not designed to carry. And the conditions which really govern the use of the magnetic brake are such that you must limit the speed at which the brake is applied, you must limit the coasting on the magnetic brake, and you must limit its use, and when you have to make any sudden stop on steep gradients, especially at a high rate of speed, the brake may not act. I have carried out a great number of experiments in order to see really what amount of work there is on the motors, and though we have been told that it is not necessary to provide any capacity in the motors to provide for the magnetic brake, I have found you get some disastrous results unless you put in motors with a larger capacity than is necessary for traction purposes only. The experiments I have carried out recently show that the current occasionally generated by the motors when operating the magnetic brake is momentarily greater than the motors take when doing the work of hauling the cars. You see from that that with a hilly country and the magnetic brake, the brake, if used for coasting, is doing work on the down grade as well as the up grade, consequently the motor has no time to dissipate that heat which is generated. The result of the continuous working of the magnetic brake on steep gradients would be that unless the motors were properly designed to carry the loading, you would have severe trouble with the commutation of the motors, and you would get a complication that would render the brake inoperative. That also applies to the great necessity of limiting the speed at which the magnetic brake is applied. Although I have adopted the magnetic brake in Adelaide, I have had to give strict instructions that the magnetic brake is not to be used at a speed greater than fifteen miles per hour. Neither is the magnetic brake to be used for coasting on down gradients. In Adelaide we have no gradients to speak of, and it was that