Building and Riding a Unicycle (Jun, 1960)
Building and Riding a Unicycle
Learning to ride this fugitive from the circus is becoming an increasingly popular modern day exercise
By HAROLD P. SMITH
A USED or even wrecked 20 or 24-in. bicycle will supply most of the major parts needed to make a unicycle, and you can build it for one-third the cost of a new one.
We chose 24-in. bikes for parts to build the unicycles shown in Fig. 1. If you are picking up a used or wrecked bike for parts, select one with a good front wheel fork and rear wheel. And, if possible, one having a New Departure Model D or Bendix 13 coaster brake because these types have rear wheel hubs that are identical in size and shape at both ends, a feature that simplifies the making of the axle adapters.
Converting the Wheel Hub. First remove all the coaster brake parts from the rear wheel hub and, since these parts are not needed they can be discarded. Then, with a spoke wrench obtainable at any bike shop, remove all wire spokes from wheel rim and hub. This is necessary because of the high heat the hub will be subjected to during brazing later.
To center and fasten the 5/8-in. axle to the hub, grind, file or turn down the , outer edges of four %-in. steel washers (Fig. 3) concentric with the hole to fit deeply into the bearing races of the hub. The washers and axle are to be brazed to the hub later to make up a one piece hub-axle assembly.
Fork and Axle Bearing Supports. Since there are no bicycle parts that can be used for the bearing supports welded to the ends of the fork (Fig. 2), you will have to make these from scratch. First hacksaw two 9/16-in. wide rings or collars from 1-1/2-in. black-iron pipe, and four 1-in. lengths of 1/2-in. dia. steel shafting. Grind or file a 1/16-in. deep semi-circular notch on the pieces of 1/2-in. shafting as in Fig. 4, so that they will seat against the pipe rings.
Dress the insides of the rings with a half-round file or portable hand grinder so the ball bearings can be slipped into the rings. Then remove the bearings and clamp two of the 1/2-in. shafting pieces to each ring. Back up the 1/2-in. shafting with scrap pieces of steel square stock as in Fig. 4, and be sure the pieces of 1/2-in. shafting are diametrically opposite and parallel to each other. Weld or braze the pieces of shafting to the rings.
If you are not equipped to do the welding or brazing yourself and must have it done at a local weld shop, make up all of the parts requiring welding so you can have all of it done at one time. It will be cheaper that way.
After the bearing supports are brazed, bore a hole through the center of each of the %-in. shafting pieces with a #3 drill. Then saw the bearing supports apart with a hacksaw, cutting through the 1/2-in. pieces of shafting as in Fig. 4. Make identifying centerpunch marks on the two halves of one of 1/2-in. shafting pieces on each support so that they can be reassembled exactly as they were before cutting apart. Next, redrill or open the #3 drilled holes in one side of each bearing support with a 17/64-in. drill. Tap the #3 holes in the other sides with a 1/4-28-in. tap. Use 1/4-28 x 1-in. hex-head cap screws to fasten bearing support halves together.
Since all bicycle forks are bent slightly for caster effect, your first job will be to straighten it. Clamp the fork between two soft-wood blocks in a vise and, with a length of 1 or 1-1/4-in. pipe slipped over a fork arm for leverage as in Fig. 5, carefully bend the arm straight. If you make a series of short bends, gradually moving the pipe toward the end of the fork arm, this reverse cold bending will not affect the strength of the fork. Then saw off the ends of the fork arms 12 in. from the inside center of the fork where the arms come together. This will leave about 1/2-in. clearance for a balloon tire on the 24-in. wheel.
Now clamp the bearing supports on a scrap piece of 1-5/8-in. round stock, spacing them 3 in. or the length of wheel hub apart as in Fig. 6. Butt the sawed-off ends of the fork arms to the centers of the threaded halves of the bearing supports and braze in place. Use plenty of brazing metal and build up a joint that flows smoothly to the contour of the bearing support.
Pedal Crank Arms. Since it would take quite a bit of work to adapt the one-piece crank arms on American-built bikes for use on this unicycle, we used two lefthand cranks and pedals made for English bikes. Your local bike shop or hardware store can order these for you from Chicago Cycle Supply Co., 224 N. Desplaines St., Chicago, Illinois. The cost will be about $6 for the two 5 1/2-in. crank arms, pedals and fastening keys.
The crank arms fasten to the 5/8-in. hub axle with tapered keys, so you will have to file two 3/8-in. key slots at the ends of the axle as in Fig. 3. Make these slots diametrically opposite each other. Have the crank arms on hand when filing the slots so that you can make trial assemblies to obtain a good firm fit with no play. Any loose movement of the crank arms on the axle would make it very difficult to ride the unicycle, particularly for a beginner.
The axle can now be permanently brazed to the wheel hub. Place one of the four washers, previously ground down to fit within the hub bearing races, into each end of the hub and braze in place. Then position the other two washers flush with the ends of the hub and braze. Finally, insert the axle, position so it projects equi-distant at each end of the hub and braze it to the end washers.
Reassembling the Wheel. Clamp the fork between two pieces of wood in a vise with the bearing supports up. Hang the wheel rim in the fork crotch and install the hub assembly with bearings in the bearing supports. If washers or spacers are needed to center the hub between the bearings, saw two rings from a 1/2-in. pipe and dress the insides with a file so they will slide on the 5/8-in. axle shaft. Now, replace the wire wheel spokes, loosely at first, and gradually tighten them as you true up the wheel. If you have trouble truing up the wheel, take it to your local bike shop and have it done because this is a job where experience can save a lot of time.
Saddle. Regular bike seats don’t work too well on a unicycle. Most riders prefer a deeply crotched saddle about 4-in. wide and softly padded. The saddle is mounted on a metal post that slides inside the fork stem so the saddle height can be adjusted to suit the length of the rider’s legs.
Obtain a 10-in. length of pipe or tube that will just slide into the stem on the bike fork you used, and weld a piece of flat steel to one end as in Fig. 2. Drill two 3/16-in. holes in it for fastening to the saddle later. To clamp the saddle post at any height on the fork stem, hacksaw a 1-in. long slot at the end of the stem and over this, place a bike seat-post clamp. You may have to spread the post clamp a little to make it fit.
For the saddle, cut the ends of a 12-in. length of 2 x 2-in. pine at a 45Â° angle and fasten the two cut-off pieces to the 12-in. piece with glue and nails as in Fig. 7. File and sand all of the corners and edges round and give it two coats of shellac. Then cut two oval-shaped pieces of 1-in. thick sponge or foam rubber as in Fig. 7, and bevel the edges. Stretch the small oval of sponge rubber across the triangular blocks on the wooden frame and fasten to ends of the 12-in. piece with rubber cement and a few roofing nails. Center the large oval-shaped piece of sponge rubber over the smaller one and fasten all around with rubber cement.
Next, cover the rubber padding with upholstery fabric, overlapping and tacking the long edges to bottom of the wooden frame first. Then fold and tuck the material at the corners under the ends and tack the ends to the bottom. Stitch the folded corners to the sides with heavy thread. Center and fasten the saddle post to the bottom of the padded saddle with two #10×1-1/4-in. rh screws.
When assembling the saddle to the fork, adjust the height of the saddle so that the distance from the top of the saddle to the pedal nearest the floor is equal to the rider’s full leg length as measured from the crotch to the foot instep.
How to Ride a Unicycle. According to Mr. Joseph J. Giallombardo, a veteran unicyclist and physical education instructor at New Trier High School, Winnetka, Illinois, the best way of becoming accustomed to the “feel”‘of being on the unicycle and to practice balance, is to hold on to a gymnasium stall bar with one hand as you rock the wheel back and forth slightly with the foot pedals. Outdoors, you could hang on to a fence or clothesline post to maintain side-to-side or lateral balance. Have the pedal crank arms in the horizontal position so the wheel can be rocked easily and instantly to maintain fore and aft balance. Place the balls of your foot, not instep, on the pedal.
The whole trick is in being able to quickly shift the wheel hub directly under the center of gravity of you the rider. Do not attempt to remain motionless. You must keep rocking the wheel back and forth to maintain balance.
To get off the unicycle gracefully, move your body weight just a little ahead of the wheel axle. Then, as one pedal nears its lowest position, step forward and down, reaching back with your hand to catch the unicycle by its saddle.
To mount the unicycle, without the aid of a fence or post, stand in back of the cycle straddling the saddle. Have the left pedal near the floor and place your left foot on it lightly. Bend forward and grasp the tire with your right hand a few inches forward of the fork. Now, using the left pedal as a step, push yourself forward and quickly place your right foot on the right pedal while moving the wheel first back and forward with your hand to keep your balance. When the crank arms reach the horizontal position, straighten up and hold your arms outspread at your sides to help maintain lateral balance. Then lunge forward, making one complete turn of the wheel, so your feet again return to the horizontal position where you can rock the wheel to regain your balance. With continued practice, you will soon find that you can make several complete turns of the wheel before rocking to regain balance.