Cooking by Electricity

How can heating and cooking utensils be fitted for the use of electricity?-S. D. F.

To fit heating and cooking utensils for the use of electricity, a thin film of enamel or cement is spread over the outer saucepan, griddle, kettle or heater. Then iron, platinum or other high resistance wire is laid zigzag over it, with copper wire connections made to the two ends; and more of the cement or enamel is spread over the wires so as to completely imbed them. When enamel is used the apparatus is put in a kiln and burnt on similar to the ordinary iron cooking utensils. In both methods the film of enamel or cement insulating the heating wires is put on so thin and is so good a conductor of heat that the heat generated by the electricity is rapidly conveyed to the utensil to be heated. Electricity can thus be sent through the wires without fear of overheating them. This would not be possible if they were exposed to the air, which does not conduct heat, but radiates it.

To Straighten Steel Tools

I have had trouble with reamers bending while hardening. Can you help me in straightening them?-J. G. W.

Such tools as taps, reamers, or drills, which become bent or crooked in hardening may be straightened in the following manner. Place the bent tool between the centers of the lathe and then put a rather heavy piece of steel in the tool post of the lathe, as shown in the accompanying figure. The end of the bar in the tool post should be against the convex side of the work.

Rub a little oil on the work and heat until the oil commences to smoke; then apply pressure by means of the cross feed

screw, until the article bends a little the other way. While in this condition the work should be suddenly cooled. If it is not straight, the process may be repeated. Great care should be taken to cool the pieces uniformly; otherwise the unequal contraction would probably cause the work to crack. This method is proving very successful in many shops, and is the method advised by authorities on steel work.

To Measure Power of an Engine Kindly explain the use of a transmissiondynamometer for measuring the power of an engine.-W. R. D.

A form of transmission-dynamometer which may be easily and cheaply constructed has been devised by Professor Goss of Purdue University. It is shown. diagrammatically in the accompanying figure. This dynamometer consists of a differential lever by which the difference in tension of the two sides of a belt is determined. This lever is pivoted to a fixed point "c" and carries the pulleys "b" and "c." It is provided with a scalepan "s," and a combined dash-pot and counterweight "d." The power transmitted by the belt is measured by the speed in feet per minute at which it runs multiplied by the difference in tension of the two sides, as shown on the dynamometer. The force tending to raise the left end of the lever is twice the tension of the tight side of the belt; that tending

from the fulcrum of the lever to the center of the pulley supported by it. Since the lever arm of the scale-pan "ao" is twice the above, a weight on the pan equal to the difference in tension of the belt will advance the lever.

The belt speed is known from the revolutions per minute of the driven pulley and its circumference in feet. The formПdnw 33000'

ula for horse-power is H. P. =

where "d" is the diameter of the driven pulley plus the thickness of the belt in feet, "n" is its revolutions per minute, and "w" is the weight in pounds necessary to balance the lever. The observer in charge should keep such a weight on the scale-pan as will cause the lever-arm to move evenly between the stops.

To Make a Shoe Polishing Box How can I make a shoe polishing case?H. W. R.

One writer suggests box fitted as is shown in the accompanying illustration. A strip is fastened a few inches below the top of the box, for a foot rest, with rollers made of broom handles on each side. A strip of flannel passes over the shoe and under the rollers, and may be moved

very briskly by grasping the ends. A drawer may be fitted into the lower part of the box for carrying the blacking and brushes.

Remedy for "Grounding" Troubles

How does a ground in the armature of an incandescent lamp lighting dynamo announce itself? Please give the best method for locating and clearing trouble.-T. J.

Two or more "grounds"-accidental connections between the conductors on the armature and its iron core or the shaft or spider-would have practically the same effect as a short circuit and should be treated in the same way. A single ground would have little or no effect, provided the circuit is not intentionally or accidentally grounded at some other point. On an electric railwayoverhead trolley-or other circuit which. employs the earth as the return conductor, or a three-wire system with the neutral conductor grounded, one or more grounds in the armature would allow the current to pass directly through them, and would cause the machine to spark and have a very variable torque at different parts of a revolution.

A ground may be detected by testing

with a magneto and bell. It may be located by the drop-of-potential method. Another way to locate it is to wrap a wire around the commutator so as to make connection with all the bars, and then connect a source of current to this wire and to the armature shaft--by pressing a wire upon the latter. The current will then flow from the armature conductors through the ground connection and the magnetic effect of the armature winding will be localized at the point where the ground is. This point is then found by the indications of a compass needle slowly moved around the surface of the armature. The current may be obtained from a storage battery or from the circuit, but should be regulated by lamps or other resistance so as not to exceed the normal armature current. The armature core may be more or less insulated from the shaft and ground by the insulation between the laminae, in which case one contact with the conductors would not have the effect of a ground. Sometimes the ground may be in a place where it can be removed without much trouble, but usually the particular coil and often others have to be rewound.

Steam Action in Duplex Pump How does the steam act in a duplex steam pump, and how is valve gear set?-F. A. McL.

The steam must enter the cylinders before the stroke is completed, because the steam accelerates the speed of the piston in the duplex pump quite as much as in the simplex pump. When the steam pis

ton arrives at a distance of three and onehalf times the width of a steam port from the cylinder head, it begins to close the channel that lies nearest to the exhaust port, cramps the exhaust, and when it arrives at a distance equal to two and one-half times the width of a steam port from the cylinder head, the steam cannot exhaust at all. The exhaust steam is now compressed while the driving steam is becoming wire-drawn, which continues till the piston arrives at a distance of one and one-half times the width of a steam port from the cylinder head. At this moment the steam begins to enter in front of the piston, and the driving steam begins to exhaust. When the steam piston has arrived at a distance of two and one-half times the width of a steam port from the cylinder head toward which it is moving, the slack is used up on the valve of the other steam cylinder, which is then ready to start..

The two steam pistons should be placed in the middle of their strokes, and the rocker arms set plumb to the piston rod with the large rocker arms attached to the piston rods so as to be guided thereby. Then the steam valves must be mounted on their respective seats, so as to cover both outer ports in the chest face. Then the valve rods must be inserted and joined to the respective short rocker arms, and the set collars adjusted to the valves so that the slack may be equally divided. Then one of the large rocker arms must be placed out of plumb until the outer port of the opposite steam cylinder is quite open. Then the valve gear is set.

A Mountain of Ivory IT T is no wonder naturalists should be bewailing the disappearance of the African elephant. This pile of twenty thousand billiard balls, reckoning ten to each mighty beast-five for each tuskrepresents all that a herd of two thousand full grown elephants will yield. In Asia and Africa there are hosts of resident agents buying tusks from the natives or financing white or black hunters in expeditions into the interior that may take a couple of years.

The precious tusks are wrapped in sacking and brought to London or Antwerp, where sales totalling $400,000 at one time are held periodically. It is an

astonishing sight to walk through the ivory "floors" at the docks with their far stretching vistas of curved tusks of all sizes-some of them seven feet long.

Here come the brokers, their sales lists in hand, to go feeling and tapping among the ivory to see which is perfectly sound and solid, and bid accordingly. A hollow tusk is readily detected and fetches barely one twentieth of the price of a hard and perfect specimen. It is from the brokers that the billard ball makers buy, and then forthwith put the tusks on to whirling saws and turning machines, from which they soon emerge as costly and perfect spheres ready for the chalked cues and green cloth of the favorite indoor sport.