�Fig. 12. A nail
or piece of wire
will grind Buick
valves
��134
lap joint form. If such is the case the ring is removed from the cylinder and placed in the vise between the soft metal jaw clips, as shown at Fig. 13 B. Sufficient metal is removed with a fine file from the edges of the ring at the slot until the edges come into line and a slight space exists between them when the ring is placed into the cylinder. It is impor- tant that this space be left between the ends, for if this is not done, when the ring becomes heated the expansion of metal may cause the ends to abut and the ring to jam in the cylinder.
Another method of fitting a piston ring is indicated at Fig. 13, C. A plug is made of soft wood, such as yellow pine that will be an easy fit in the cylinder and one end is turned down enough so that a shoulder will be formed to back the ring. The turned down por- tion should be a little less than the width of the ring to be tested. The ring is pushed on this turned down end of the wooden plug and held by a small batten secured by a screw in the center. This does not hold the ring tightly enough to keep it from closing up. It is also important to turn the end of the wooden plug small enough so that its diameter will be less than the bore of the ring when that member is tightly closed. The cylinder bore is smeared with a little Prussian blue pigment which is spread evenly over the cylin- der wall with a piece of' waste and the ring is moved back and forth in the cylinder while it is held square by the shoulder on the plug. The high spot on the ring will be shown by color. Us- ually the ring will be found to bear hard- est at each side of the slot. These high spots are removed carefully with a very
��Popular Science Monthly
fine mill file or piece of emery cloth and the ring is again inserted, in the cylinder bore to find other high spots which are removed in a similar manner. When the rings fit fairly well all around, the en- tire surface will have a uniform coating of blue.
If the old piston rings are bright all around but appear to have lost their elas- ticity, a new lease of life may be given by a process known as peening, which is shown at Fig. 13, D. The ring is stood on a surface plate and is tapped inside with the peen end of a light hammer us- ing the harder blows at the thick section and gradually reducing the force of the blow as the slot is approached. If skill- fully done a ring may be stretched to some extent and considerable elasticity imparted. Piston rings are not always of simple form shown. Various duplex constructions have been offered with an idea of reducing the possibility of leak- age. A ring of this type which is known as the "Leak Proof" piston packing is shown at Fig. 13, E. These duplex rings are harder to install than the simple forms, and it is important that they be carefully fitted to the cylinder and to the
��f,7e
��Wood Block
���LeahProof Pkton Ring
��Fig. 13. Processes incidental to piston ring restoration
piston grooves, as described below.
The bottom ring should be placed in position first; this is easily accom- plished by springing the ring open enough to pass on the piston and then sliding it into place in the lower groove which on some types of engines is below the wrist pin, whereas in others all grooves are above that member. It is
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