The Brennan Dual Gyroscope Control.
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An Amazing Invention is Brought to the Stage of Practical Operation.
The problem of imparting stability to otherwise unstable bodies, structures, or vehicles has engaged the attention of Mr. Louis Brennan, CB., the inventor of the Brennan steerable torpedo, and a gentleman who gained his early engineering training under the able tuition of Mr. Alexander Kennedy Smith, for several decades. As far back as 40 years ago, when Mr. Brennan was the victim of the excessive jottings which are associated with up-country travelling in Australia, he formed the con
ception of working out a method of securing smooth and easy running for passenger-carrying vehicles of all classes, and the germ of the idea which le then conceived has now been brought to a fruitful and fortune-presaging stage by his genius.
It is not possible for us to give exact :mechanical details of the improved form in which Mr. Brennan now constructs and regulates his mechanism, because, as he has personally informed us, there have been variations and departures from his original designs to an extent that must render his specification No. 27,212 of 1903 of little more value than an empirical guide. Many inventors Defore Mr. Brennan have worked upon :he devising of a self-balancing structure, and we are perfectly aware that aumerous attempts have been made to ;ecure that end by the adoption of two and more gyroscopes, but it has to be admitted that no real measure of suc:ess has hitherto waited upon any of :hese earlier essays in the direction of assured stability under the conditions )f practical use.
It must suffice, at the present time, and pending the receipt of suitable lrawings from Mr. Brennan hereafter, .hat we give only a brief statement of he underlying principles which have allowed him successfully to combat the enormous difficulties which have baffled so many other experimenters in the same line of scientific research. Two gyroscopes, or, to use the word more generally applied to the form invented by Lord Kelvin, two gyrostats, are employed by Mr. Brennan, and the spindles of the gyrostat wheels are rotated by any suitable means, preferably electrical, but permissibly by a steam turbine of the Delaval type, or by a high-speed internal-combustion engine, with the interposition of suitable gearing where necessary. The two gyrostats are in every respect similar, except that they rotate in opposite directions, and they are supported in carriers which are pivoted on parallel axes, these carriers being connected, by means of Links or gearing, so that the rotation of the one carrier in one direction insures a corresponding rotation of the other, carrier in .the opposite direction. The axes of the gyrostats are horizontal, and at rightangles to the longitudinal axis of the vehicle.
The essence of the invention is the introduction of means by which any disturbance of equilibrium, or change of direction of the vehicle, automatically controls the precession of the gyrostats, together with an automatic means of accelerating or retarding such precession. This capacity to provide variable positive or negative acceleration of the precession is such, that the structure or vehicle is rapidly brought back to a middle or normal position of maximum stability, as soon as any force, as wind pressure, centrifugal influences, changed distribution of load, or the like, sets up a disturbance of stability, and the action is so controlled that there is no tendency of any gyroscopic effect to persist, and, thereby, to pro duce oscillations increasing in amplitude.
An interesting feature of the invention is that Mr. Brennan can dispose his two gyroscopes in any part of the structure, no matter at what distance apart, so long as their relative move ments are maintained in accordance with the principles laid down above.
One of each such pair of gyrostats is termed by its inventor the actuating gyrostat, and it is provided with means for automatically accelerating the precession when the equilibrium is disturbed, so that the connection between the two invariably must bring about equal but opposite movements of precession in the second one when the actuating gyrostat is operated. It will be realised, therefore, that equal movements of both the gyrostats about their horizontal axes will take place, and that the second gyrostat will assist in controlling the balance of the car. Where very high speeds are employed, it is provided that each pair of gyrostats can be enclosed in an air-tight casing from which air has been exhausted. Although the earlier models were mounted on ball bearings, Mr. Brennan has now adopted a particular form ot plain bearing.
It will, of course, be clear that the gyrostats must continue to revolve when the vehicle is at rest, unless supporting " legs" are dropped, and that their revolutions are independent of the driving mechanism for the road wheels, and it will be of interest to our readers to know that the small gyrostats in the model of which we give illustrations run at a speed of 7,000 revolutions per minute, and have a ring-diameter of five inches.
We recently had the opportunity to observe the behaviour of a model vehicle, adapted to run upon a single rail, by invitation of the inventor, this model being built true to a one-eighth scale : each a lb. of weight of this model accordingly corresponds with a weight of 512lb. in the full-size structure. The model is 'close upon 5 feet in extreme length, and is m foot 6 inches in width ; its unladen weight, inclusive of a battery of 12 secondary cells, is 1751b., and it carried out the majority of the tests under notice with a useful load of toolb. upon it, except on the occasions when it bore either of two members of the visiting party, one of whom weighed to stone, or the equiva
lent of a load in excess of 30 tons for a full-size car, the dimensions of which would have been nearly 40 feet in length by 12 feet in width.
Mr. Brennan's programme of tests was exhaustive and thorough, as will be gathered from our four accompanying illustrations. They proved beyond question that his system really provides stability on sharp curves, both horizontal and vertical, and that the singletrack vehicle for the conveyance of dead loads is no longer to be regarded as the dream of an illusionist. Probably the most interesting of the tests were those in which the model carried a full-grown man along the track and across a length of wire cable, stretched taut between two banks scene 30 feet apart, and in which it safely travelled over a loose piece of similar cable merely laid upon the lawn. Although no tests were made, on this occasion, other than upon a mono-rail or its equivalent, the single rail which is shown in three of our illustrations consisting as a matter of fact of ordinary gas piping, it will be evident that for low-speed vehicles on common roads no special track is necessary. We fear,
however, that a high-speed vehicle designed to run on common roads would be liable to irremediable risk of side slip, owing to the absence of any reliable means of resisting centrifugal force at the points of ,contact with the sun face of the highway, for the beautiful function of the system, whereby the car when running on a mono-rail leans inwards on a curve, and so automatically counter-balances the effect of centrifugal force, against which the outer rail of an ordinary locomotive track is super-elevated, and which cannot fail to command the admiration of both the mechanical and the lay mind, would not be equally operative.
Another remarkable quality of Mr. Brennan's combination is the extraordinary capacity of his car, under the dual gyroscopic influence, to resist any force that may be applied to it. For example, the dropping of weights equivalent to five tons upon the extreme edge of the wagon body of the little model did not, as might have been expected, depress that side of the structure on the contrary, the result was a distinct elevation of that side—a rather uncanny effect.
In the full-size railway car, designed to carry, say, a couple of hundred passengers, the gyroscopes will revolve at some 3,000 revolutions per minute, and this will provide so high a peri
pheral speed that the factor of safety ir stability will be several times greatei than in the model. FCKL such a vehicle the total weight of each gyrostat wil be about 1,5oolb., whilst the diamete of each ring will be 42 inches, and onl. 2 horse-power will be needed for thei rotation. It will weigh 20 tons empty Needless to say, high-speed railwa travelling, with greater comfort fo passengers owing to lack of vibratioi or oscillation, is Mr. Brennan's firs goal. The smallness of the spar occupied by the stability mechanisn will allow very neat designs of cars ti be employed, although they may be a wide and as high as circumstances o route and environment permit.
We understand from Mr. Brennai that it is his intention, as soon as hi present absorption in the mono-rai branch of the invention is lessened, t give close attention to the study c commercial and slow-speed moto vehicles for use on ordinary highways It is scarcely necessary for us to ad that our supporters may rest assure that first publication in regard to an such developments will appear in "To COMMERCIAL MOTOR."