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Small        Cupola        For        The

[pic 1]

byRobert        Frazier

One  man  can  easily  handle  this  cupola.   It  will  melt  35  lbs.  of  iron  at  a  time,  or about  300  lbs.  per  hour.

 brick and sift it through a riddle to remove unbroken pieces. The floor lining should be about 3 inches thick at the back and sides and slope toward the tap hole where it is about 2 or 2 ½ inches thick.

The two tuyeres (air- blast inlet ports), 3 inches by 1 ¾ inches wide are located on opposite  sides of the shell 9 inches above the bottom of the drum, and 6 inches above the floor lining. Cut two 3-inch   diameter   holes  in

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RON can be melted in small quantities, and very  inexpensively  with the  small cupola described in this article. The simple materials for its construction are obtainable almost any- where.   One man can easily take care of the furnace, charging the coke and metal, tapping and  pouring.    Under  ordinary  conditions  it will melt about 330 pounds of metal per hour. This can be increased to 400 pounds per hour, but such rapid melting is hard on the liningand is not recommended.

The shell of the cupola consists of two standard 15 ½ -inch by 21 ½-inch grease drums (Fig.  5).  Cut  the  head  and  the bottom out of the one that is to be placed on top. They may be fastened together by small angle brackets bolted to the sides of the joint, which are then bolted together.

The grease drums are about 15 inches in internal diameter. The lining is  made  up with regular 3-inch cupola brick set in a mortar made of fireclay and water. This makes the internal diameter 9 inches. If the 3-inch cupola fire brick are not available, 18-inch diameter drums may be used and lined with ordinary fire brick set on end with the wide face on a radial line, making the in- ternal diameter 10 inches. The space between the bricks should be filled with the fireclay mixture.   The floor of the cupola is lined with a mixture of one-fourth fireclay and three- fourths  crushed  fire  brick.     Crush  the fire

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 the shell and insert 4-inch lengths of 3-inch stove pipe, leaving one inch project  outside. Shape the inner end as shown in Fig. 1. Then build the lining up  around the  tuyeres and fill in the space between the tuyeres and the bricks with the fireclay mixture. The breast opening is 4x4 inches. The spout is formed of heavy sheet metal, flanged on one end and bolted or riveted to the shell at  the  breast hole. These details are all shown in the sec- tional drawings, Fig. 1 and 2.

A blower capable of delivering 90 to 100 cubic feet of air per minute at 4 or 5 ounces pressure will be quite satisfactory. With this air blast pressure, the coke bed is  carried from 16 to 18 inches above the tuyeres. You can check on this later by examining the lining which will show a fusion or "burning- back" a little above the tuyeres and extending upward to the top limit of the melting zone. When this has been determined, a measuring rod can be made to indicate the height to maintain the coke bed when charging the cupola. If greater  pressure  and  air  volume are used, the melting zone will be too high, causing an excess  of sparks to fly from the top. Lower pressure will result in a  lower melting zone and cold iron.

Fig. 3 shows the layout of the blower and the air-piping to the furnace. The 3-inch outlet of the blower leads through a windgate to  a  3-inch  T,  and  the  air  supply  branches

Mechanix   Illustrated

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[pic 2]

Workshop

Scrap iron can be quickly and safely melted in small quantities for castings, etc. with this home blast furnace.

here, a line going to each tuyere.  The piping is 3-inch  stove pipe with the necessary ells. The windgate can be made up for you by a tinner.   It is a simple sheet metal box with a movable slide to regulate the opening, and thus the air supply. Stove pipe makes an in- expensive and easily renewable air line. However, if a more permanent system is de- sired, 3-inch gas pipe may be used.

The cupola  and  blower can  be set up  on a frame built up of angle iron about 16 inches high. A movable wooden step can be built  up to stand on while charging the furnace.

The fire is started in the cupola with shav- ings and small pieces of wood. Then  add larger pieces of wood until the wood is piled

September, 1941

 above the tuyeres. Then add a small quantity of soft coke. This coke is easier to ignite and will start the regular coke. Regular foundry coke should be used. To yield the 'best' melt- ing service, the coke and iron must be broken up fine, the coke in chunks the size of an egg and the iron into small pieces with a max- imum of not over 2 pounds when using good clean scrap.

Then charge in half of the amount of coke required for the coke bed. With the air ad- mitted by the breast hole, sufficient heat should be produced by the wood fire to dry the lining and ignite the coke. If additional air is needed, you can temporarily disconnect

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Small Cupola For Workshop

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the air pipes at the tuyeres. When the coke charged has become well ignited, add the re- mainder of the coke needed to bring the coke bed up to the required height. This can be meas- ured from the top by means of the rod which was previously prepared for this purpose.