Figure 1096 shows the working action of the shock absorber when the lever arm is moving on an upward stroke. When driving over a rough road, the recoil of the car springs is instantly softened by the resistance set up in the shock absorber in forcing the fluid in the shock absorber through small by-passes. This is accomplished by means of the rotating shaft. This shaft, which is connected to the lever arm, automatically turns every time an uneven point in the road is encountered and forces the fluid from one compartment to another through small by-passes in the stationary wing shaft and around the bottom of the needle valve seat. (See Fig. 1096).
On the downward stroke of the arm where greater shock absorber resistance is required to cushion the recoil of the springs, the fluid is forced only’ through the by-pass around the bottom of the needle valve seat. The resistance at this point is controlled by the adjustment of the needle valve. The by-pass in the stationary wing shaft is completely closed by the ball check valve which is forced down on its seat by the pressure of the fluid.
To permit dealers to completely service Model A shock absorbers, a set of shock absorber tools has recently been designed (see Fig. 1097). K. R. Wilson ofBuffalo, N. Y., is making the tools. The complete set sells for $24.50. These tools permit dealers to take care of every service operation necessary in the dismantling and reassembly of Model A shock absorbers and should be included as part of every dealer’s service equipment.
Shock absorber complaints usually fall into one of three classes, i.e.:
Should an owner complain of hard riding, first make certain that the springs, spring shackles and shock absorber connecting links are properly lubricated and working freely.
Due to continued neglect a spring will be- come dry and rusty-a shackle may freeze in its bushing-a connecting link will become dry. These conditions seriously affect the action of the shock absorber (see Fig. 1098).
After lubricating these parts throughly and making certain that none of the shackles are frozen, check the shock absorber for proper adjustment and correct fluid level. Shock absorbers must be adjusted to give the owner the type of ride they prefer. Screwing the needle valve to the right increases the resistance in the instrument. Screwing the needle valve to the left reduces the resistance.
If it is suspected that a shock absorber is below its required strength, the strength of the instrument can be quickly checked while it is on the car by means of the special tool shown in Fig. 1097. This can be done as follows:
Disconnect shock absorber arm from instrument and drop linkage down out of the way. Close needle valve by turning it to the right until it seats. Insert testing tool over square end of the wing shaft, tighten testing tool clamp bolt and slide the weight back to the rear notch on the end of the shaft as shown in Fig. 1100. With the lever arm in its fully raised position, release the weight and record the number of seconds for the weight to travel downward to its stop position.
There is approximately 23 degrees of travel, and if the instrument is at its full strength it will require at least 15 1/2 seconds for the weight to descend (at summer temperature), and 50 seconds (at freezing temperature). It being assumed that the instrument has been exposed to outside temperatures just prior to making the test. If the car has been standing in a heated shop for some time the summer temperature test will of course apply.
If the reading in seconds is less than the figures given, the instrument is not at its required strength. With the needle valve in the closed position, move the testing tool lever in an up and down direction. If a free motion of more than 3⁄4″ to l”, measured at end of lever, is felt while the arm is being moved up and down, it indicates that the air vents are plugged, causing an air pocket in the working chamber. If an air vent is plug- ged, or if an instrument is under minimum strength, it will be necessary to remove the shock absorber from the car, take it apart and thoroughly clean the parts. To perform this operation; proceed as follows: