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Armstrong Shocks

Here is an interesting article I found on a Singer web site from the UK, that talks about our shocks, how they work and how to adjust their resistance. I also found a maintenance tip from a British Car club in Texas. The writer there suggested cleaning out the shock with kerosene then refilling with oil. You have to remove the unit from the car for this but that is fairly simple. With the valve cap up, (screw T in the diagram) remove it. Pull out the valve unit and put it in a kerosene bath. Now dump out the oil from the chamber. It only holds a few tablespoons of oil. Fill the chamber with kerosene and work the lever and watch the fluid being pumped back and forth. Do this a couple of times then drain it and refill with oil. When I did mine I worked the oil back and forth then drained it just to make sure all the kerosene was out. The article below says you must use Armstrong Super Shock Oil but lots of people use engine oil. This sounds like a good winter project, however when I did mine it took only a half hour each for the front shocks.

The Armstrong Lever Action Shock Absorber

The Armstrong New Super Double-Acting Self-Regulating Hydraulic Shock Absorber is of the Vertical Cylinder Type. All working parts are submerged in oil.

CONSTRUCTION.

The body A is a zinc alloy die casting and bolts directly on to the frame of the car, the two cylinders B and C being connected by passages E and F. The double crank G and arm H are a force fit on serrated portions of spindle I, which rotates in the body A on generous double bearings. Connecting rods J connect the crank G to pistons K to which non-return recuperating valves N are fitted. The arm H is connected to the axle of the car link L.


HOW IT WORKS

As the axle moves to and from the car frame, so the pistons move in and out of their respective cylinders pumping oil from one to the other. The interior of the body is filled with oil to within 3/8" from top of cover, any shortage of oil beneath the pistons is instantly made good though the recuperating valves N.

CAM VALVE (SELF REGULATING)

As the car axle moves to and from the car frame the oil pumped from the compression cylinder B to rebound cylinder C or cylinders C to B, and has to pass between the taper ended valve P and screw Q, which is adjustable to offer any desired resistance to the action of the axle.
As will be seen from the drawing the upper end of the valve F is held in contact with the cam on spindle I, which means that on fairly good roads the valve P is in its lightest setting and shock absorber gives a normal resistance--just enough--yet not too much to produce harshness, but when bad roads are encountered the spindle I oscillates and the contour of the cam depresses the tapered end of valve P further into the central port of screw Q and thereby increases the resistance of the shock absorber.
The automatic, variable resistance obtained from the cam movement makes this shock absorber entirely self-regulating, the resistance automatically increasing as required thus enabling the car to pass over bad with comfort equal to good roads.

SCREW TAPER VALVE.

As the axle moves towards the frame the oil is pumped from the cylinder B to cylinder C, but as it has to pass the spring loaded valve R a resistance governed by the tension on the spring is offered to the movement of the axle.
On the return or rebound stroke the oil is pumped from cylinder C to cylinder B, and as the ball valve only opens in one direction the oil must now find its way to cylinder B past the taper screw S, which is adjustable to offer any desired resistance to the rebound of the car spring.

ADJUSTMENT OF CAM VALVE.

Both rebound and compression are controlled by screw Q, to tighten rebound and compression slack nut T, taking care that the screw Q does not turn.  Turn screw Q half a turn inwards and lock up the nut, taking care the the screw Q does not turn.
To reduce the resistance follow the above instructions, but turn screw outwards

SCREW TAPER VALVE ADJUSTMENT.

Both rebound and compression are controlled by screw S.
The same instructions apply as for cam valve, but refer to screw S and nut U.

Note.--Shock absorbers adjusted too lightly make your car feel harsh and hard; we recommend slacking off first in case of doubt.
These shock absorbers will only work satisfactorily on Armstrong Super Shock Absorber Oil. Examine your shock absorber oil lever regularly. The correct level is 3/8" from top of cover.

Double Note: I personally have found these shocks to be quite reliable and I have been able to resurect several of these by just general cleaning and fresh oil. You should try that first prior to sending it out for rebuilding.

 

Copyright 2006
Okanagan British Car Club