Popular Science Monthly 



111 



more accurate and expensive special pres- 

 sure gage. The tire gages will register 

 correctly in most cases, or at least will 

 show closely the amount of pressure so that 

 it may be compared in the different 

 cylinders. 



An adapter fitting is necessary for use 

 with a tire gage, and may be made without 

 difficulty from cast-off parts found in any 

 garage. A discarded spark-plug body 

 forms the main portion of the adapter as 

 shown at A. The inner tube valve-stem is 

 provided with a thread along its entire 

 length for the check-nut used to keep it in 

 place on the tube. A special washer of 

 brass is filed out to fit the seat in the spark- 

 plug body, against which the porcelain is 

 clamped and the valve threaded into place. 

 Of course, if the washer at the bottom of the 

 valve-stem that fits inside the inner tube is 

 large enough, this may be used. Other- 

 wise, the valve-stem should be cut off and 

 screwed into the special seat washer. 



The parts are assembled as shown at A 

 and held together by pouring molten lead or 

 babbit around the valve-stem. When the 

 filling material cools, a tight joint is assured 

 because the metal fills the threads in the 

 spark-plug body and valve-stem. To use, 

 the adapter-fitting is screwed into the 

 spark-plug hole as shown at B. The 

 engine may be cranked by the self-starter or 

 turned by hand and the tire gage will show 



Cylinder 



A tire gage fitted in a discarded spark plug 

 body to test the compression of a cylinder 



the compression in pounds per square inch 

 existing in the cylinder interior if it is held 

 in such a way as to depress the valve 

 inside. A comparison may be made be- 

 tween cylinders by testing each in turn. 



If the compression is weak, there is an 

 opportunity for gas leakage somewhere, 

 usually around the piston rings or through 

 the valves. The average compression in 

 a gasoline engine when cold is 75 lb. Some 



engines have 1 less, others more. Compres- 

 sion is determined by the volume of the 

 engine combustion chamber as compared 

 with the total cylinder contents. High 

 compression engines are more apt to knock 

 when carbonized than the low pressure 

 engines. — Victor W. Page. 



Preventing Hinge Rods from Loosen- 

 ing on an Automobile Hood 



ON most low priced cars there is no pro- 

 vision made to hold the hood hinge 

 rods in position, and they invariably be- 



Rjveted cap 



Thread 



A round nut turned on the end of the hinge 

 rod keeps an automobile hood from rattling 



come loose, due to the vibration. The 

 illustration shows a method of eliminating 

 this trouble. It is only necessary to pro- 

 vide two end caps for the rods, one of which 

 is fastened permanently while the other is 

 free to be removed by using threads. It is 

 also necessary to remove a portion of the 

 hood to provide suitable clearance for the 

 caps. The rods in their new form are held 

 securely in position. — Adolph Klein. 



The Proper Camber for the Front 

 Automobile Wheels 



THERE is no specific standard for the 

 camber or canting of front wheels 

 outward at the top, but it is done on most 

 of the cars, to make it easier to steer and 

 turn the curves than would be possible if 

 the wheels were perpendicular. This cam- 

 ber of the front wheels of different cars 

 varies from H in. to \ X A in. between 

 inside felloe measurements. If the Avheels 

 stand too far outward at the top, there is 

 apt to be some binding effect at the axles, 

 and the tires will not roll freely. 



