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in injurious quantities was less apparent, but it appears from what is now known that this is the limiting factor in the use of engines exhausting into poorly ventilated places. The presence of carbon monoxide in the air in relatively small quantities has been shown to have a marked effect upon the blood, producing sickness, and if inhaled in sufficient quantity, death. After careful inquiry, the best that can be stated at this time is that without injury to health, no more than 0.1% of carbon monoxide can be breathed and that for a short and infrequent intervals. It is probable that one-half of this percentage could be allowed for a considerable period of time without noticeable effect. The per cent. of carbon monoxide in the garage air depends upon the amount made by the engines running and on the quantity of air with which it is mixed. It will be necessary to provide ventilation for the worst combination of gases which such engines can make under unskillful handling, or else to become informed as to the actual amount of carbon monoxide produced and provide air accordingly.

It is not sufficient to consider the average amount produced as distributed over the whole time of running such a machine. The total quantity of gasoline burned in any one day may have produced but a small quantity of carbon monoxide, but if this has been confined to a relatively short period during bad carburetor adjustment, and in some poorly ventilated space, the momentary percentage may be very high and the consequence may be fatal. It is evident that to be entirely safe the ventilation must be sufficient to keep the percentage of carbon monoxide below the assigned limit when the engine is producing the maximum quantity possible. If the maximum quantity is provided for by proper ventilation, the chance of injury to health may be considered to be remote. Certain peculiarities of gasoline engines cause the percentage of carbon monoxide generated to vary between rather wide limits, but the maximum is fairly constant. No other constituent of the exhaust gases varies so much or so rapidly with slight changes of adjustment as does the carbon monoxide. Conveying the exhaust gas to the outer air is the simplest and most positive remedy for disposal of this deadly gas.

Instructions for Repairing Storage Battery.-In repairing a Willard storage battery a definite routine must be followed in tearing down and building up same in order that it will be in the best condition when re-assembled. These steps are as follows:

First: Remove all vent plugs and washers.

Second: Centerpunch both top connectors in each cell which is to be repaired; then drill 34-inch into top connector, with a 38inch diameter drill. Now pull off top connector with pair of pliers.

Third : Apply gas flame or blowtorch flame to the top of the battery long enough to soften the sealing compound under the top cover. Now, with heated putty knife, plow out the sealing compound around the edge of top cover.

Fourth: Insert a putty knife, or any other thin, broad pointed tool, heated in flame, along underside of top cover, separating it from the sealing compound. Then with putty knife, pry the top cover up the sides and off of the terminal posts.

Fifth: Then, with heated putty knife, remove all sealing compound from inner cover.

Sixth: Now play the flame onto the inner cover until it becomes soft and pliable; then take hold of both terminal posts of one cell, and remove the elements from the jar, slowly; then lift the inner cover from the terminal posts.

Seventh: Now separate positive and negative elements, by pulling them apart sideways. Destroy old separators.

Eighth: To remove a leaky jar, first empty the electrolyte from the jar, and then play the flame on the inside of the jar until the compound surrounding it is soft and plastic; then with the aid of two pairs of pliers, remove it from the crate, slowly, lifting evenly.

Ninth: To put in a new jar, in place of the leaky one, heat it thoroughly, in a pail of hot water, and force in gently.

Tenth: In re-assembling the battery, first assemble the positive and negative elements, pushing them together sideways; then turn them on the side and with both hold downs in place, insert new separators, being very careful to have the grooved side of the separators next to each side of each positive plate. Also be careful to have the separators extend beyond the plates on each side, so there will be no chance of the plates short-circuiting. Now press all separators up against hold downs.

Eleventh: Heat

up

inner cover with flame; then place same on terminal posts; then take hold of both terminal posts and slowly lower the elements into the jar

Twelfth: Now, with expansion chamber in place on the inner cover, pour the melted sealing compound on to the inner cover,

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Fig. 464.--Diagram Showing Construction of Points to be Reached in

Rebuilding or Tearing Down Willard Storage Battery.

until it reaches the level of the hole in the top of the expansion chamber,-i.e. so that when the top cover is replaced, it will squeeze the sealing compound off the top of the expansion chambers.

Thirteenth: Now soften top cover with flame and replace on terminal posts until it rests on top of expansion chamber; then place a weight on top cover until sealing compound cools.

Fourteenth: Now, pour sealing compound around the edge of the top cover, until it reaches the top of top cover; then when the sealing compound has cooled, take a putty knife and scoop extra sealing compound off of top cover, making a smooth surface over all the top of the battery.

Fifteenth : In burning the top connector to terminal post, proceed as follows: Scrape the hole of the top connector until the curface is bright and clean; scrape terminal post until top and edge are bright and clean. Now, scrape a piece of lead-preferably a small bar-bright and clean; then apply hydrogen gas flame, mixed with air under pressure, to the top connector and terminal post assembled, at the same time heating lead bar. When top connector and terminal post begin to melt, apply lead bar directly on same, melting it, thus making a firm burned connection. Then fill rest of hole-space with melted lead and smooth off even with top of top connector.

Care of Grinding Wheels.-Chattering and waviness in appearance of the part finished is usually caused either by the wheel spindle being loose in its bearings, the grinding wheel being out of true or out of balance, or particles of the material being ground having become embedded in the wheel. A loose spindle should, of course, have its bearings adjusted. In a great majority of cases, however, the cause of imperfect work is due to the wheel getting out of shape. It is important that its face should be perfectly parallel with the travel of the carriage, and in order to produce a result of this kind a diamond tool must be used, as near to the headstock or footstock center as is practicable, especially on work of small diameter. Where the work is not so small, say 2 inches in diameter, the truing device can be clamped at the most convenient point, and in either case it should be carefully seen to that the stud holding the diamond and the arm supporting same, are solid against the work. If the truing device is not rigid the face of the wheel will not be dressed perfectly true.

It will be observed that the stud in which the diamond is mounted can be revolved in its holder and it is important that the point presented to the wheel should be sharp; for instance, if the diamond should become worn and flattened, it should be turned

a

and thus present a new point to the wheel. Keeping the wheel true is important for the operator to observe, particularly so when he comes to make a final finish. The wheel should be traversed by the diamond at a uniform speed, rather slowly in order to give it time to cut away the particles. If it is desired to do rapid cutting, it will be found proper to pass the wheel by the diamond more rapidly thus making a rougher face on the wheel.

The number of times that the face of a grinding wheel has to be trued depends entirely on the character of the work being finished and the kind of wheel used. There are some wheels that wear away rapidly enough so that little truing is necessary. There are also cases where a harder wheel is desirable and a hard wheel necessarily requires more truing than a soft one. Where pieces are rather large and considerable stock has to be removed, it may be necessary to true the wheel each time a piece receives its finishing cut. Where the stock to be removed is not more than 164-inch diameter it is advisable to finish in one operation, but when there is as much as 137-inch diameter to be removed it is good practice to grind it in two operations. As stated above, it is desirable generally to present a sharp point of the diamond to the wheel in truing, but there are times when the smooth surface is preferable, particularly when it comes to producing a very fine finish; the flat surface of the diamond will tend somewhat to glaze the wheel and thus produce a better finish. A coarse wheel properly trued will produce a good finish. .

The amount of wear the wheel is subjected to depends upon the operator in many cases. Never bring an emery, corborundum or other abrasive wheel suddenly against the work or the work abruptly to the wheel. The feed should be gradual, so that the sparking will start almost imperceptibly. Grinding is not intended to be a roughing process but is a method of finishing in most cases so careful manipulation of the feed control is required to prevent the wheel from "digging" in.

Speed for Wheels. The table below designates number of revolutions per minute for specified diameters of wheels, to cause them to run at the respective periphery rates of 4,000, 5,000 and 6,000 feet per minute.

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