The Brennan Mono-rail.

Progress, Volume II, Issue 11, 2 September 1907, Page 408

The Brennan Mono-rail.

If we may judge by the line taken by the Scientific American, the way for the single-rail invention of Mr. Brennan is by no means clear yet. In its issue of March Bth its editor says that " Of course it is a far cry from the model to a structure of the size and weight of a modern railroad train ; and at the first blush it would seem as though the weight of gyroscopes of the size necessary to impart the required stability would be so great as to rob the invention of all practical utility " Further, he says, that as the inventor calculates the weight at only five per cent, of the total load, or say about three tons for a sixty- ton Pullman car, " it is certain that the fly wheel must be run at an enormous speed, at a speed so high that it becomes a matter of speculation as to what kind of metal can be found to withstand the enormous centrifugal stresses that would be involved. Furthermore, it must be remembered that failure of the rotating mechanism would mean the loss of all stability to the train, and that just here, in the unlikely event that the invention should prove to be mechanically practicable, would be a constant source of peril, which might well detract from its popularity with the travelling public." A fortnight later, after the drawings and descriptions of the trials of the model Lave been made public in Britain and reached America, the editor returns to the charge with an even worse opinion, for he says plainly that ""Were it not for the fact that its inventor bears a distinguished name, and that the exploitation of the device occupied two hours of the time of the last meeting of the Royal Society of London, the Brennan gyroscopic locomotive would deserve no further notice than is usually given to any interesting scientific toy. At the present writing indeed it cannot be regarded as having demonstrated its practical value, at least as applied to heavy trains of the kind that are now running on the railway systems of the world. The model locomotive exhibited before the Society was only six feet long, and, judging from the illustrations, 'must have been of rathe r light construction. We should be prepared to find that the weight and power of the gyroscopes would quickly increase to a point where they would be prohibitive " The editor admits at the same time that, so far as the model itself is concerned, the result of the trials was everything that could be desired , and in the description he has himself given of the apparatus occurs the best we have yet seen of the gyroscopic part of the invention. "In the model " says the editor, " as shown, there is a small closed compartment at the forward end of the car, and in the after part of this, mounted on the floor of the car, is the double gyroscope whch serves to maintain the car in equilibrium. The gyroscopes are mounted in an air-tight case in which a partial vacuum is partially maintained. They rotate in opposite directions in a vertical plane at the high speed of 7500 revolutions per minute. Provision is made for assisting the gyroscopes in returning quickly to the horizontal plane. The object of running the gyroscopes in vacuo is, of course, to get rid of the skin friction of the air, and

Mr. Brennan claims that he has been so far successful that the model will remain standing upright on its single rail for a considerable time after the current has been cut off." As the editor shows that he has realised the claims of the inventor as to the practicability of running the full sized gyroscope at the high speeds necessary to compensate for the low weight, his failure to refer again to his first adverse opinion as above quoted must be regarded as a sign that he is still unconvinced by the fuller information afforded. In engineering circles here the opinion is freely expressed that' even if the apparatus gives the results promised by the model, the invention will not be of great use for heavy traffic requiring long trains of wagons, such for example as mineral traffic, as the expense of the gyroscope on each ear — for that must necessarily be involved — would be prohibitive. Moreover, it is thought that for shunting purposes the invention would be unworkable