Motorbikin in the 40's-50's Pt.1


Sep 8, 2008
The basic design was familiar in the World War 2 years hauling defense workers to their jobs on very little gasoline, which was rationed. All sorts of small engines were used, but mostly washing machine and lawnmower motors. The basic Bartlesville bike was a rectangular frame usually of 1” angle iron that served as foot rest and mounting for brake and clutch peddles and in the middle a mounting plate for the engine. This was welded to the area formerly occupied by the peddle shaft housing and the center of the front portion welded to the front down tube. The frame was reinforced by a pair of handlebars cut and welded to the front corners of the rectangular frame and to the front down tube from the steering head. This makes a very strong structure, and resembles crash bars. The jackshaft housing was usually welded to the seat post and used 5/8” I.D. generator bearings. Many improvements were developed along the way and those are what I want to detail here. In the beginning, before Whizzer motorbikes, the rear drive pulley on the wheel consisted of a plywood pulley that was attached to the engine shaft and a vee groove cut into the edge with whatever we could come up with, like sharpened screwdrivers or if we were lucky, a genuine wood lathe tool. This was a tedious and very dangerous job at best and we just squinted and ducked, as we didn’t know what safety shields were. The insides were removed to leave about 3” of rim and the thing was attached to the spokes with lots of washers and screws. The metal Whizzer pulley sieve was the best thing to happen to the art. Some bikes used no clutch at all, and the rest took a cue from reel-type lawnmowers and used an idler pulley against the outside of the bottom run of belt from the engine to the jackshaft. The motor pulley usually was about 2” and the jackshaft pulley it drove was about 6”. The final drive was something like 2-1/2” driving whatever the Whizzer pulley was. The actual ratio was usually jiggled around until the thing pulled itself with reasonable authority and satisfactory speed. Our dynamometer was SHAWNEE HILL If you couldn’t pull it, you didn’t have squat and everyone would laugh at you. When it came time for THE TEST, some folks would secretly drop moth balls in the gas tank to raise the BTU of the fuel for a few minutes to put out more power. The down side was it always grew crystals in the carburetor and choked it off, so a quick trip home was in order to rinse it out. I built my first motorbike in the 7th grade with a 5/8 hp. Briggs & Stratton WM out of a Maytag washer. It had a suction carburetor and a little square tank that mounted on the footrest frame. I could ride the 10 blocks to school and back all week on one tank of gas. I had no clutch and to stop, I put my shoe soles against the front tire behind the fork, since I had no front fender. If I stopped, I simply legged it along about 3 feet and the beast was running again. The throttle was a choke cable with a knob on it. It started a love affair that has lasted 57 years so far and I am just now finishing up number (approx.)14 The art was to build the best thing you could with what you could barter for, buy, or whatever. You also tried to dream up something that no one else had done. That made you noteworthy. My contribution to the art was to wrap the peddle chain around the coaster brake and pull it back with a screen door spring fastened to the seat clamp bolt at the top of the seat tube. This was a improvement over welding a lever to the sprocket and a clevis rod fastened to it. It was much easier to remove the rear wheel to fix the many flats. My 12th one was built on a Schwinn 20” frame with a 1-1/2hp Briggs& Stratton model N, which was the WMB with a gravity carburetor and an oil pump rather than a splasher on the rod. I couldn’t get ready to pay $45 for a Whizzer replica shieve, so I elected to use a chain drive final. I machined an aluminum hub which I sawed in half and bolted together on the brake housing inside the spokes. From this, 3 spacers extend through the spokes and a pedal sprocket is bolted to the alloy hub. Enough of the sprocket middle is removed so that the brake lever has room to mount. A brake sprocket on its hub is mounted on the jackshaft. The clutch is the usual idler pulley on an arm powered by a spring horse spring. It has a large washer welded to the top of it so that it can be held down to rope-start the engine and also has a motorcycle clutch lever on the handlebar. .Number 13 is an old Rollfast frame with a Schwinn spring fork. It had a 2 hp Lawson for a time but has been replaced with a 3hp Clinton from a 1968 Yazoo high-wheel lawnmower. It is also driven by a bicycle chain. I mounted a rubber tired wheel from a clothes dryer tub support on the crankshaft and it drives a bicycle generator so that I have lights whenever the motor is running. As on a bicycle wheel, the generator may be retracted for daytime running. The fuel tanks (2) are made from 4” dia. Exhaust tubing and the ends of 16 ga. Sheet were bulged by applying 6000 psi. on a rubber stopper while supporting the stack of ends on a large diameter pipe nipple. The filler necks and caps came from junked automotive power steering reservoirs. I cut the tops off of two needle valves and mounted them to the top of the tanks and made brass stems that extend to seats in the bottom of the tank. I can select which tank from the top side. The tanks are strapped to the sides of the frame on a special shoe folded over the frame tubes. They tee into a settling bowl with a shutoff. This bike runs an honest 40 and when my old friend from years ago rode it , he threw me the ultimate challenge with a twinkle. “BUT WILL IT CLIMB SHAWNEE HILL?” I returned shortly and proudly reported that I started from a dead stop at the bottom and was doing 30 at the top. The new one is the fulfillment of a fantasy I have had for years. A TRANSMISSION ! I decided I could use a Sturmey-Archer 3-speed rear wheel transmission as a jackshaft. In the planning stage, I realized the thing free-wheeled in the wrong direction but a friend on the internet asked if I could use a second jackshaft. It seemed ridiculous at first, but finally it didn’t sound all that silly. I would have to mount it on the left rear of the rectangle in a fork with the sprocket facing outward. It would have to drive a sprocket on a spindle with another sprocket which would drive the rear sprocket. I machined off the right side spoke flange and cut the center out of a 6” pulley so that it would fit against the inside of the left spoke flange. I pop-riveted it there through the spoke holes drilled 1/8”. A tapped boss was then welded to the seat post to receive a 5/8” shaft with a snap ring groove to retain the two 15-T ball- bearing sprockets on a common tubular hub. I was finally ready for a test ride. The engine is a Jiang Dong Chinese industrial engine of 5-1/2 hp. It is an angled cylinder with overhead valves and required the seat post be relocated rearward to directly against the rear fender, some 3” of relocation with a 13 X 22” rectangle plus an additional inch to make it longer. The front tube was re-formed to follow the arc of the front wheel. I have elected to leave the governor in place as it is effectively “cruise control” and I never had that before. It limits the engine to 3300 rpm, but it is enough to propel it at 42 mph. in 3rd gear. There is roughly another third of the rpm range unused. The test was sort of a shocker because the pull of the small chain loop bent the 2nd jackshaft and caused the chain to climb and jump teeth. I machined a cup that I bolted to the end of the shaft and welded an ear on it. I attached a large turnbuckle to that and the other end to a bracket bolted to the top fork behind the seat post. This is pretty much in line with the driving and driven sprockets and solved the problem, even allowing me to tweak the chain adjustment a mite. I might add, the sprockets are all #41, with the Sturmey-Archer sprocket having been machined down and inset in a recess turned in the 18-T drive sprocket and silver soldered in place. The rear wheel has a 56-T sprocket. The rear wheel is one for a Worksman industrial bicycle and has a super heavy rim with spoke nipple dimples in it and is laced with 0.100” spokes. The coaster brake sprocket is about 4”dia. With the aluminum hub and steel sprocket in place with no tire, it weighs 11-1/2 lbs.! I bought a Walmart Cruiser bike with balloon tires and a nice big tubular fork, and stainless steel fenders. I used the gooseneck, tires and tubes, fenders, fork, and put the rear coaster brake wheel on the front so I have a front brake. I am now running the rear brake chain around the rear sprocket and then connecting it’s spring to the same attachment point on the brake peddle arm. The clutch spring is off a trampoline and has lots of authority, so I am using a long motorcycle clutch lever. Of course I have the peddle to push if I want to. There is a thorn proof band inside the tires. I was lucky and found a bicycle seat about 1 foot wide. It must have been off an exercise machine. The throttle cable is a John Deere throttle and by twisting the knob it can be locked in position. One big surprise was that the transmission ratios are backward due to the fact the housing, formerly the rear wheel hub, is driven and the sprocket is the driver for the rear wheel. It makes no difference and I spend most of the time in 2nd gear to run the transmission 1:1 to spare the internals unnecessary wear. The rear fender brace that came on the donor bike was too short so I used an available piece of ½” stainless tubing that curves nicely around the outside of the fender. Since building I have replaced the front coaster brake with a Schwinn rear drum brake hub with the sprocket removed. Not much better but made my chrome plater happy
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