FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1910
1910 - 0538.PDF
project these points on to the planes, then we get equal pressure on OZ and OV. OV is virtually the whole plane, whereas OZ is only about two-thirds of the plane. So the remainder of the left-hand plane is devoted to the tendency of righting the machine. Of course there will be considerable slip on the right-hand plane, but this, though having a tendency to cause the machine to drift, would be helpful to the righting effect of the left-hand plane. I think the matter turns on the direction of Plt P2, which must be parallel to the force, W. Of course, this is only my opinion, backed by experience with models, and I shall be only too pleased if I am on the wrong track. This righting effect can be seen by taking a piece of paper 2 ins. wide and about 8 ins. long and bending it in the middle, giving it a dihedral angle. If this is dropped at any angle it will automatically right itself. Croydon. ARTHUR C. BASEBE. STABILITY DEVICE. [602] I wish to have your opinion on the following appliance, which I believe will give automatic stability to aeroplanes. Attached to the wheel working the warping or aileron wires is a small reversible electric motor, the necessary power to actuate it being derived from a battery. Connection is given by a device somewhat like a spirit-level, excepting that mercury takes the place of the spirit, and that it is slightly concave. When the aeroplane tilts over, the mercury in the tube falls to one side, forming a con nection between wires from battery to motor, which being set in motion warps the planes. The rudder also has an attachment to the motor, this completing the necessary action to obtain lateral stability. As the relative action of the rudder with warping to effect a turn is different, hand manipulation is to be used for circling movements, the stabilising device being automatically disconnected. Longitudinal automatic stability could be arranged for in a similar way, with the exception of the connection for the rudder. Of course, the motor is not directly connected to the warping wires ; however, the mechanical difficulties are not great, and I have evolved quite a number of methods to produce the various actions. Hand-control could always be resorted to in emergencies, but I think that my method, besides serving to keep the aeroplane in automatic balance, would be of much use in case of a sudden breakdown of the engine, and also lessen the constant nervous strain on pilots during lengthy flights. I have had this idea of automatic control for quite some time, and although I have never seen or heard of an appliance of this kind, it seems to me to be simple and feasible. If my explanation is not sufficiently clear, perhaps I could send you one or two rough designs. Trusting you will favour me with your opinion as to whether it is a practical idea, and with best wishes for your continued success. Sunderland. J. H. DORAN. [The mercury tube device has been invented as a means of indicating, by means of coloured electric lights, the canting of a machine in flight, and has also been invented as a means of throwing into action a relay mechanism for manipulating the control-gear, although the exact details may not have been quite the same as those described in the above letter. We are not aware that the device has ever been used in practice, and it is therefore impossible to say how it would act. Everything depends, of course, upon the steadiness of the motion being such as to prevent the mercury from setting up a natural oscillation from one end of the tube to the other.—ED.] FLOATS FOR AEROPLANES. [603] I am very much obliged to Miss Bland for her interesting table of weights carried by different gliders. I notice that she asks for information re the use of floats for starting aeroplanes over water. I remember that Mr. Bellamy tried floats at Brooklands some three years or so ago, for the purpose of testing propellers, but I do not think they were very successful. It might pay to use some arrangement like M. Santos Dumont's hydroplane, and to place planes similar to aeroplane surfaces below, so that as the speed is increased the apparatus rises, and the resistance becomes less. It is quite likely that this method has been tried already, but I am not sure. Miss Bland has certainly attained a wonderful success with her glider, and I shall be most interested to hear how the power-driven machine behaves. I hope it will be equally successful. Windsor. W. WHATELY SMITH. PROPELLER REACTION. [604] It has puzzled me for some time how two propellers could possibly nullify the effects of torque when one engine only is used. In a good many types of models which I have seen two skeins of elastic and two propellers are used, and that, to me at least, appears to be as it should. But in the Wright biplane, for instance, surely the reaction of the engine must have the same effect as it would if only one propeller were used. If my assumptions are incorrect, I should be very glad if you or one or your readers could put me right. Park Royal. DAVID LUCKING. [The engine torque is not balanced by the use of twin propellers. Twin propellers ought to be used instead of a single propeller when the calculations show that greater efficiency and convenience will result therefrom. See recent article on testing propellers. When two propellers are used it may be deemed desirable to cause them to rotate in opposite directions in order to neutralise their gyroscopic effect. Some constructors, however, consider this to be an unnecessary precaution.—ED.] THE PITCH OF A PROPELLER. [605] Could you tell me through your valuable paper exactly how to get the pitch of a propeller ? I must state right here that I don't understand mathematics. Has the diameter anything to do with the pitch ? I understand that the angle at which the blades are §et affects it, but on most propellers the angle varies from the boss to the tip. If you would explain you would very much oblige Park Royal. INQUIRER. [Possibly the accompanying sketches will serve to elucidate the difficulty. The pitch of most propellers is constant along the blade, consequently the angle varies from tip to root. At any radius, if the circumference corresponding to that radius is set off in a straight line, and the angle of the blade at that radius is set off as shown in 0fBlade_ Blade the sketch, then the pitch.will be represented by the vertical drawn from the opposite end of the circumference line, as shown. A series of such diagrams drawn for different radii will produce the same pitch with a propeller blade as ordinarily constructed. liana The sketches illustrate the pitch represented by the angle of the chord. It is a moot point whether this should be taken as the datum from which to estimate the true pitch, but it serves the purpose of illustrating the meaning of the term.—ED.] EXPERIMENTAL GLIDER. [606] I intend to build a glider, and would be very much obliged if you would answer me the following question, viz. : Would biplane glider, 18 ft. span, chord, 5 ft., height, 4J ft., tail, 6 ft. by 3 ft., have enough area to carry a boy of fifteen ? Headingley. P. GARNETT. [Much depends on the weight of our correspondent, but, allowing 130 lbs., every square foot of surface would then carry a little under three-quarters of a pound load, which is about as much as ought to be allowed in experiments of this sort, at any rate until experience has been gained in connection with gliding in high winds.—ED.] 536
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
