In the absence of a steel auto bumper, a heavy duty muscle builder can be built from wood, with the exception of a large coil expansion spring or several smaller ones. Again the overall dimensions will depend upon the size or weight of the child.

As shown in Figure 2.19, the base is a 28-in. length at least 3/4 in. thick, ripped to a width of 5J in.; its ends are half-lapped into 12-in. lengths of the same material 2 in. wide. The two uprights to which the long rocking member is pivoted are n or 12 in. high, cut from 3/4-in. stock 3 1/2 in. wide, and half-lapped into the sides of the base 7 1/4 in. from the front end. They are separated by, but attached to, an 8-in. length of 2 x 4 set up edgeways between them. For a footrest an 11-in. section of J-in. dowel is glued into a tightly fitting hole through all three uprights.

The rocking member, also of 3/4-in. stock, is 3 1/2 in. wide and 26 or 27 in. long. A 3 1/2-in. length of 2 x 4 is screwed into the underside and drilled to form a pivot block for the long carriage bolt extending through both uprights. Extra holes drilled in the two uprights will permit adjustments for growing children. An eye-bolt in the front end holds one end of the helical spring; another in the front end of the base assembly has its bolt end countersunk flush with the bottom of the front cross member.

An animal head, such as the horse in the Figure 2.19, is fastened into a tightly fitting slot just behind the pivot block by means of 2-in. finishing nails driven through the edges of the rocking strip. For longer life a pair of small angle irons anchor it fore and aft, as illustrated. The seat is band-sawed or compass sawed from available thick stock and has two countersunk bolts to attach it to a series of holes at the end of the rocker to adjust it to the legs of the user. It may be padded with excelsior or kapok and covered with leatherette once the bolts are in place. The rear end of the wide rocking member will have to be slimmed down with a drawknife near the pommel of the "saddle."

Fig. a. 19. Adjustable heavy duty muscle builder.

If a large, helical expansion spring cannot be obtained, two or more pairs of ordinary 16-in. screen door springs, attached by screweyes on both edges of the forward end of the rocker, can be adjusted diagonally to screweyes near the ends of the front cross member of the base to create sufficient tension for small children; add another pair of springs for heavier children if necessary. Enamel the base black, dark green, or blue, and the other two members red. A pure white or dappled steed will be set off by brown or black bridle straps of real leather, oilcloth, or outlined in paint.