A 2-1/2,-hp lawn mower engine drives this kart at more than 30 mph. It's Class A fun for anyone. By S. Calhoun Smith
T
HE "go kart" has taken the U. S. by storm. A happy wedding of lawn mower engine and steel tubing on four little wheels, it has become a craze among kids and adults with a yen for racing or just plain driving fun. Kart racing originated in California and has spread eastward since 1956. Now the GKCA (Go Kart Ka rt Club of of America) is firmly established established and has set up sensible rules governing design and power for stable, safe "karting." Even the lowest powered Class A, 2.5 102
hp karts are capable of 30 to 35 mph with an adult aboard and more when driven by a lightweight 10-year-old. Races are run on paved parking lots and small dirt ovals and regular sports car type raceways have been built with tracks four-tenths of a mile in length and 20 feet wide. Such tracks incorporate eleven turns, both banked and flat. The MI Kart was designed and built by Bob Peru of Red Bank, N. J. and can be considered a basic Class A kart. It complies in all respects with GKCA Mechanix Illustrated
specifications. Cost runs from $100 to $110 complete with an A-400 Clinton engine. Peru did the welding himself but anyone not equipped to do it would have to spend $20 to $30 extra. The building time was about 25 hours and the tools required were a square, hack
saw, tin snips, files, hammer, large vise and an electric hand drill or drill press. To help hold cost down, the frame is made of thin-wall conduit, but more expensive chrome-moly tubing could be substituted throughout. Some parts, the seat and steering hoops, steering
COMPLETED FRAME with axles installed; a thin-wall conduit is used to reduce cost
BELLY PAN and seat back are sheet steel; they're spot-welded to the conduit frame.
January, 1960
103 103
FRONT END view shows brake and throttle pedals and the simple steering mechanism.
SPOT BRAKE pivots flush against inside face of sprocket. Note engine mount plate.
yoke, front wheel spindle brackets and engine mount plate, can be purchased ready-formed from various kart manufacturers. Their use will speed building considerablyBegin construction by drawing a side frame outline on a piece of scrap lumber. Cut and flare the tubing required and heat the lower piece to make the bend. Fit the pieces over the outline and clamp them. Then tack weld all joints and remove the framing from the board. Using the first side as a pattern, patte rn, clamp the part s of the second to it and tack weld them together. This will insure uniformity. Next fabricate the front and rear axles. Bend the front wheel spindle brackets to shape and drill them for the kingpin bolts. Then weld them to the front axle tube. Align them carefully, square on the tube ends and parallel to each other. The rear axle tube ends are bushed
CLINTON 2-1/2-hp engine drives MI kart at more than 30 mph with adult load; note throttle crank on seat hoop.
SPANKING NEW kart is ready to go. You can upholster seat but boat cushion from marine supplier does nicely.
with a length of pipe to reduce the inside diameter for the 5/8-inch round stock axles. The axles are held in the tube with a quarterinch bolt near each inner end. They can be tapped for short bolts or holes [Continued on page 150]
RECOIL STARTER is pulled as youthful driver sits with his left foot depressing brake pedal.
Build MI's Kart [Continued from page 106]
can be drilled all the way through for bolts and nuts. The side frames, axles and crosspieces can now be assembled. Cut and flare the pieces and tack weld them, using a try square to make sure they're aligned. Add the axles to the frame ends, squaring up the assembly as it progresses. Note that the front axle is rotated slightly in the side frame ends so that the kingpin axis has a 7° rearward slant. The frame-axle assembly can now be completely welded at all joints. As the last step, add the diagonal crosspiece at the rear. The front wheel spindle units are made up next. Cut the kingpin bushing tubes to fit snug inside the brackets. Then weld the wheel spindle bolts to the sides of the bushb ushings. Follow this by welding the spindle steering arm pieces to the bushings. Note that right- and left-hand units are required since the steering arm pieces slant inward. The steering and seat hoops are now formed and cut to fit onto the frame. To make the curves, apply heat and bend a little at a time so that the tubing will not deform. Tack weld the hoops in position after clamping them at the proper angles; then complete the welds. Next cut the belly pan and seat back to shape, checking the pieces against the frame for correct dimensions. Tack weld the belly pan in place on the bottom of the frame and then skip weld the pan edges to the frame. Welds should be about one inch long and two inches apart. Where the pan touches the crosspiece at the steering hoop rosette, welds can be used or the sheet and tubing can be drilled for self-tapping sheet metal screws. To prevent the sheet steel from buckling during welding, use a chill block clamped about a quarter-inch from the edge along the area to be welded. The chill block can be a piece of 1/2xlx24-inch steel bar stock. The seat back is skip welded to the front of the seat hoop in the same manner as the belly pan. Make halfround cuts to clear the side frame tubes. Sissy rails can now be bent to shape, fitted to the sides and seat hoop and welded in place. The steeri ng assembly is made next. Cut and drill the steering shaft support 150
bracket s of 1/4xl-in 1/4xl- in strip steel. Bend the steering shaft front end and drill it for the tie-rod bolt. Then bend the yoke to shape. Put brackets and collars on the steering shaft and weld the yoke to the shaft end. Next slide the shaft through the top bracket to spread out the collars and weld the bracket to the underside of the hoop curve. Hold the lower end of the shaft at the proper angle to align the top bracket while welding. Finish by sliding the shaft into position and welding the front bracket to the top of the front axle. The tie-rod ends are threaded for about one inch to match the Heim ball end fittings. Clevis end or Ford brake rod ends could be substituted if the ball ends are not readily available. Adjust the rod ends at the center to align the wheel spindles at zero degrees. Toe-in or toe-out can be adjusted later when the kart's running qualities have been checked. While working on the front end, weld the pedal pivot bolts to the side frames. Drive and engine mount parts are next on the list. The wheel hub is first fitted with a large washer for bolting on the large sprocket. This permits removal of the sprocket if different sizes are to be fitted. (If (If you do not wish to bother with wit h removal, removal , the sprocket can be welded flush to the wheel hub inside face.) face.) The large washer was her and sprocket are drilled for mounting bolts. Disassemble the wheel to make welding on the hub easier. The large washer is welded to the hub 3/16-in from the inside face so that the hub forms a shoulder for centering the sprocket. Weld the washer from behind, aligning it carefully so that it and the sprocket will track without any wobble. After assembly, mount the drive wheel and sprocket on the axle. Next bolt the engine to the mount plate, install the clutch (if used) and the chain. Now carefully align the chain and sprockets, moving the engine and mount on the frame. When set, mark the position and clamp the mount plate to the frame. Then remove the engine and wheel and weld the mount plate to the frame. The engine mounting bolts should be in the center of the slots so that the engine can be shifted to correct for wear on the chain January, 1960
Build MI's Kart and sprocket. The spot brake is made and installed next. Detail drawings are self-explanatory, but follow this procedure for mounting on the axle: mount moun t drive driv e wheel on axle; mount brake on pivot bolt and tube; clamp brake firmly to sprocket in "brake" position (this will position pivot tube tub e on bottom of axle tube); then clamp and weld pivot tube to axle. The throttle linkage is made next. Cut out and drill all parts shown on the detail drawing. Then put the engine in place on the mount so that the upper linkage parts can be aligned with the engine throttle. The brackets, rods and cranks can be assembled by brazing. Complete the throttle and brake linkage by making the pedals and push rods. Note that there are rightand left-hand pedals. Remember to slide the fairleads and stop tubes onto the push rods before bending the S ends. Rods can be fitted with clevis ends if desired so that adjustments can be made. Fit one end of the rod to the brake at the rear and put the pedal on the other end. Next put the pedal on the pivot bolt at the front, clamp the fairleads to the side frames and braze them in place. Braze the stop to the rod ahead of the fairlead with the brake off and clear of the sprocket. The throttle push rod and pedal are assembled in a similar manner. Last, make and install return springs on both pedals. This completes the metal work on the kart. All welds should be wire brushed. Welding splatters and braze flux should be chipped off all metal surfaces and the metal cleaned before painting. It's a good idea to clean up the welds during fabrication for easy access to the tight corners. The Clinton engine, of course, is not the only one which can be used; West Bend, Briggs & Stratton, Continental, Power Products and McCulloch engines fill the bill with slight mount modifications. The builder who wishes to customize his kart will find such items as mufflers, drum brakes, chromed tanks, steering wheels and racing slicks available from the many kart manufacturers. You can add whatever your pocketbook will allow—but simple or dressed up, the MI kart is a kartload of fun fun. •
