Are you worried by any question in Engineering or the Mechanic Arts? Put the question into writing and mail it to the Consulting Department, TECHNICAL WORLD MAGAZINE We have made arrangements to have all such questions answered by a staff of consulting engineers and other experts whose services have been specially enlisted for that purpose. If the question asked is of general interest, the answer will be published in the magazine. If of only personal interest, the answer will be sent by mail, provided a stamped and addressed envelope is enclosed with the question. Requests for information as to where desired articles can be purchased, will also be cheerfully answered. Remedy for Mis-Firing What are the causes of mis-firing and pound- Mis-firing or skipping explosions is If the spark is advanced too far, caus- 1 back" the spark lever, and if this does not remedy the trouble, it may be caused by: (a) Loose crank bearing. (b) Loose cross head or piston bearing. (c) Loose fly wheel. (d) Loose main bearing on journal. The remedy for these troubles is selfevident. If unable to overcome this difficulty the services of some expert should be secured to diagnose it. The pounding or knocking sensation is not only very annoying to the operator, but will do more injury to the motor than all the other troubles combined. The absence of oil in the cylinder will also cause the motor to pound. If the pounding occurs only when the machine is laboring under a heavy load or ascending a hill on the high gear, it can almost invariably be traced to the spark being too far advanced. How to Fill Sacks Please suggest some ready and easy method of filling sacks with grain.-F. A. B. Set up three posts made of two by four pine timbers, as indicated in the drawing, with the apex about six feet from the ground At a height that will permit the sack to rest on the ground when filled, screw stout hooks into the scantlings. If the sack is raised too far its sides will tear out This arrangement is portable and the services of but one instead of two persons will be required to fill the sack. DEVICE FOR FILLING SACKS WITH GRAIN. Charcoal Sifter Will you print a drawing of a device for sifting wood ashes in order that I may secure charcoal for my hens?-T. J. T. The simplest apparatus will suffice. Take a box, and replace the bottom with a piece of stout wire netting. Nail on a FOR SIFTING CHARCOAL. board for a handle. By shaking a small quantity of ashes at a time, the charcoal may be easily sifted out. Artificial Daylight Is there an artificial light which gives colors their true daylight appearance?—E. A. No form of artificial light has been discovered which can be recommended as a substitute for daylight in color examination. The electric arc light and the magnesium light are perhaps the best for this purpose. Pressure of Molten Iron How do you calculate the upward pressure of molten iron on a mould?-W. I. S. This is calculated in the same way as the upward pressure of water, which is measured as follows: The depth (in feet) is multiplied by the weight (in pounds) of a cubic foot of water (62.35), and the product, in turn, by the area (in square feet) upon which the pressure is exerted. Thus, if the depth were 4 feet, and the area 10 square feet, the pressure would be 4x62.35x10. Now, iron is 7.2 times heavier than water The cubic inch is here taken as a basis. The weight of a cubic inch of cast iron is approximately .2607 of a pound. To calculate the upward pressure of molten iron, therefore, multiply the depth (in inches) by .2607, and this product by the number of square inches in the area upon which the pressure acts. To Find H. P. of Gasoline Engine Please illustrate and describe method of finding the horse power of small gasoline engines, using brake.-H. L. The figure represents a simple and easily arranged differential strap brake, which gives satisfactory results for small motors of less than two horse power. It consists of a piece of belt held in place on the pulley by clips or strings fastened parallel with the shaft to keep the belt from slipping off. Two spring scales, one of which is anchored and the other attached to a hand lever, to regulate the compression of the belt upon the surface of the pulley when the differential weight, B-C, on the scales may be noted simultaneously with the revolutions of the pulley. The formula then would be The accompanying sketch illustrates the principle of an electric track switch, and its operation. I, I are two insulators placed in the trolley wire cutting out a portion of the wire from the rest of the line. M is the electro magnet which operates the switch proper. The windings of this electro magnet are connected at one end to the live trolley and at the other end to the insulated portion of the trolley. No current flows through the magnet winding unless there is some connection between the trolley wire and the ground. When it is desired to operate the switch, the motorman places his controller on the first or second notch as the car comes under the insulated section of trolley wire. I M ELECTRIC TRACK SWITCH. B -D DIFFERENTIAL STRAP BRAke. The trolley car operates as a closed switch, current flowing from the live trolley section through the magnet windings to the insulated section of the trolley, through the trolley wheel and connections to the ground. The magnet is energized and the switch is thrown. When the motorman does not desire to throw the switch, he allows his car to drift under the insulated portion of the trolley wire with the controller on the off point. Thus the circuit is open between the insulated trolley wire and the ground. The portion of the trolley wire between I, I is situated from 50 to 75 feet from the switch. The switch is controlled by the magnet M. Auto's Engine Makes Great Record By William T. Walsh HE old theory that automobiles are eccentric machines, irresponsible in their workings, subject to all manner of accidents, and lacking, under hard usage, in wearing qualities has been finally and effectually exploded as the result of a recent test. This prejudice against belief in the permanent efficiency of a given automobile was in part justifiable, for until the last few years the auto vehicles turned out were far from satisfactory. A season's use and the machine went to the junk heap. The general public, and indeed the most enthu siastic autoists, as a rule, do not realize the enormous strides that invention has made in the durability and efficiency of motor cars during the twentieth century. It was to call attention to the full possibilities of the modern standard motor vehicle that the trial test referred to was made. Rather strangely enough, it was not a new machine that was employed for the purpose, but one that already had a run of over 40,000 miles to its credit. The owner had turned in the vehicle for the purpose of securing a more recent pattern and the makers were so well pleased with its condition that they de MISS ROCHE, OF MILWAUKEE, THE ONLY WOMAN TO OPERATE A CAR IN A NON-STOP TEST. termined to put its long-employed parts to a further test of endurance. How long the motor of a car that had been driven over the worst sort of roads in all weathers and in all temperatures, ranging from one hundred degrees to zero, would run without once stopping, was the problem. The results were truly remarkable. In one hundred and forty hours and thirtysix minutes, two thousand, two and onehalf miles were made without the motors being brought to a stop, though, of course, the car itself was not in motion all of this time. Such a run, while unusual, would have no great significance were it not for the excellent condition the machine's parts, as a whole, were in at the end of the test. The trial was finally ended, not because of any break down, but because the gasoline used was of such poor quality as to close up the tube that fed the carbureter. The machine employed in the test was a small touring car of eighteen horse power that had been purchased in the fall of 1904. In the spring of the following year the car was resold and its new owner kept a careful record of the mileage, gasoline consumption, cost for repairs, etc. Up to the time the test was made the machine, as already stated, had traveled over 40,000 miles. The "non-stop" run, as it was called, was arranged for in the comparatively short time of four days. In preparation few changes were made in the parts of the car. Only new tires were fitted and storage batteries installed in place of the customary dry cell type. The spark coil vibrators were also over-hauled to fit them to the difference in the battery force. That there might not be the slightest doubt raised as to the result of the test a corps of disinterested observers were selected who were with the car during its entire run, and two experts were chosen to declare as to the condition of the machinery at the end of the run. The experts named were Edward B. Waite, A. S. M. E., Head of the Instruction Department of the American School of Correspondence, and Technical Editor of TECHNICAL WORLD MAGAZINE, and Professor Virgil Oldberg, M. E., of the Armour Institute of Technology. The trial was made between the cities of Milwaukee and Chicago, back and forth, till over two thousand miles had been run, when the stoppage of the feeder occurred. Over two hundred miles were covered after that, but these were not counted. A general invitation had been issued to automobile manufacturers, owners and all other interested persons to witness the dismanteling of the car. On the morning of the twenty-eighth of February, a |