For the expenditure of quite a small number of pence, one may construct a machine which will show fairly accurately what is the value of one’s grip and the twisting, power of the arms; and, even if inaccurate, will serve for competitive purposes.  The apparatus is very simple in principle, consisting of but five pieces of wood, an ordinary spring balance registering up to 40 lbs., and a couple of handles.  The total cost is but a couple of shillings at the outside.

Fig. 162 is a plan of the machine as used for grip measuring.  The base is a piece of deal 1 inch thick, 2 feet long, and 5-1/2 inches wide.  The lever, L, is pivoted at P, attached to a spring balance at Q, and subjected to the pull of the hand at a point, R.

The pressure exerted at R is to that registered at Q as the distance PQ is to the distance PR.  As the spring balance will not record beyond 40 lbs., the ratio of PQ to PR may conveniently be made 5 to 1, as this will allow for the performances of quite a strong man; but even if the ratio be lowered to 4 to 1, few readers will stretch the balance to its limit.

The balance should preferably be of the type shown in Fig. 162, having an indicator projecting at right angles to the scale through a slot, as this can be very easily fitted with a sliding index, I, in the form of a 1/4-inch strip of tin bent over at the ends to embrace the edges of the balance.

CONSTRUCTION.

[Illustration:  Fig. 162.—­Plan of strength tester.]

[Illustration:  Fig. 163.—­Grips of strength tester.]

As the pressures on the machine are high, the construction must be solid throughout.  The lever frame, A, and pivot piece, C, should be of one-inch oak, and the two last be screwed very securely to the baseboard.  The shape of A is shown in Fig. 163.  The inside is cut out with a pad saw, a square notch being formed at the back for the lever to move in.  The handles of an old rubber chest expander come in useful for the grips.  One grip, D, is used entire for attachment to the lever; while of the other only the wooden part is required, to be mounted on a 1/4-inch steel bar running through the arms of A near the ends of the horns.  If a handle of this kind is not available for D, one may substitute for it a piece of metal tubing of not less than 1/2-inch diameter, or a 3/4-inch wooden rod, attached to an eye on the lever by a wire passing through its centre.

A handle, if used, is joined to the lever by means of a brass plate 3/4 inch wide and a couple of inches long.  A hole is bored in the centre somewhat smaller than the knob to which the rubber was fastened, and joined up to one long edge by a couple of saw cuts.  Two holes for good-sized screws must also be drilled and countersunk, and a socket for the knob must be scooped out of the lever.  After making screw holes in the proper positions, pass the shank of the knob through the slot in the plate, and screw the plate on the lever.  This method holds the handle firmly while allowing it to move freely.