DIY OLD SCHOOL CHOPPER BIKE
Old Skool Attitude chopper brings back the golden age of chopper building when most bicycles had only a single speed, one brake, balloon tires, and nice flowing lines in the frame. Your daddy would remember the days when he and his buddies would take that old bicycle, extend the forks by hammering another pair end to end, replace the front wheel with a smaller one, and then strip all unnecessary parts from the frame. Those builders who had access to a welder may have even modified the frame or forks to adjust the rake, which is what I plan to do here.
The fun thing about this project is that all of the parts are true to the era, right down to the 1970s exercise bike that I used for parts.
This photo shows the vintage 1970s single speed frame that I found at the dump one day while scavenging for parts. I was just a young "whipper snapper" when these bikes were on the road, but I do remember seeing them chopped and modified, ridden by garage hackers of the day. I thought it would be cool to salvage this old frame from the mud and give it the life it always wanted, keeping true to the style of the era from whence it came. I had an old 1970s exercise bicycle sitting in the back of my garage, as well as a banana seat, an old single speed wheel, and a vintage bicycle light, so this project was certainly possible.
I planned to add longer forks to the chopper, but did not want it to lean back too much, so a simple frame extension would be necessary in order to increase the rake and length of the frame, which would keep the bottom bracket roughly at the same height to the ground.
As shown, the original head tube was removed and two pieces of conduit, equal in diameter to the original frame tube were fit in place. The original head tube could not be reused due to the lugged construction, which leaves huge holes in the head tube and contaminates the joint with brazing filler. Another head tube from some scrap frame was used to replace the original head tube.
This photo shows the top tube extension tack welded to the frame. This 8 inch long piece of conduit has the same diameter as the original frame tubing, so it would be easy to seamlessly integrate it by grinding away the weld material. Head tube angle was also increased to allow the new forks to have quite a bit of rake so that the frame would not be lifted at the front, creating a skyscraper style chopper.
When doing these ad-hoc frame modifications, it is a good idea to place the parts and wheels on the ground to make sure your final product will have the angles and dimensions you are after. Bottom bracket height is another matter of concern, as you don't want your pedals to hit the ground around corners.
The first extension tube was completely welded at the top tube joint as well as the head tube joint as shown here. The head tube was checked for vertical alignment with the seat tube just after the first few tack welds were made.
To make the final product look like it was born to be a chopper, the frame welds are ground completely flush and then carefully cleaned with a flat file. The resulting tube extension as shown in this photo is completely seamless. When making a seamless joint, rough grind the weld material with a grinder disc, being careful not to create a low spot, and then finish with a hand file, so you do not accidentally take away any excess material.
The seamless joint will be just as strong as the original weld, as long as your penetration and welding technique are adequate. Chances are that you will have to fill in a few tiny holes and the grind a little more, but it is all for the love of the craft.
The missing section of down tube will be filled in with another piece of electrical conduit, this time a section of factory elbow. As shown here, the elbow is cut so that the curve joins the original down tube as a butt joint and then curves up to meet the head tube. If you have a tube bender, you could also make your own curved extension tube.
This photo shows the completed frame modifications after cleaning up the down tube welds at the seam. Once painted, there will be no detectable seam where the frame was cut and welded, making the final product look very professional. I'll bet your dad never had a chopper frame of this quality!
To keep with my silly idea of only adding vintage parts to the Old Skool chopper, I dug out this vintage 1970s exercise bike from the huge pile of scrap at back of my garage. I could almost hear ABBA songs playing in the background as I gave the cranks one last spin before heating up the zip disc for total annihilation of the unit. I decided to use the handlebars of the exercise bike as chopper forks, integrating the actual handlebars and fork legs as one smooth flowing line. Those massive cranks would also fit the new chopper perfectly, as they were also the correct style for this project.
The two front tubes that form the handlebars and front stand on the old exercise bike were hacked from the frame as shown here 9. I also cut the legs off of some really old kid's bike forks so I could weld them to the end of the new forks, creating that nice tapered look that all forks had back in the day. Also shown here is a fork stem that will fit into the chopper frame's head tube, allowing me to create the new long forks.
To create the new flowing front forks, the two amputated fork legs were bolted to the front wheel axle and then tack welded to the exercise bike tubing. This photo gives clear image of how I plan to integrate the curved tubing into one continually flowing handlebar and fork unit. The front wheel is used as a guide to make sure that each fork leg and handlebar half had the same shape and angle.
To join the new long forks to the chopper, a fork stem would need to be connected to both tubes in order to create a useable pair of forks. The fork stem and two small tubes shown here will be used to complete the assembly, securing the two fork legs to the head tube. The two smaller tubes will be welded to the fork stem at 90 degrees to each other and are at whatever length is necessary to place the fork legs parallel to each other as will soon be shown.
The two small tubes are welded to the base of the fork stem as shown in this photo so that there is a 90 degree angle between them. Because the front wheel is being used as a guide to keep the two fork legs parallel to each other, it is easy to calculate how long each of the two small tubes needs to be. The ends of both tubes are ground out to conform to the fork legs, making the joint easy to weld.
This photo shows how the new fork stem joins the two fork legs together so that they run parallel to each other once held in place by the front wheel axle. The position of the fork stem will determine the length of the forks and the height of the handlebars in relationship to the frame.
I decided to keep the forks as long as possible, placing the handlebars very low for a "low and lean" look. The fork stem should also run perfectly parallel to each fork leg in order to keep the forks aligned with the rest of the frame.
The new forks can now be installed as shown here, although it is not a good idea to put any weight on them just yet. The two small tubes that connect the fork legs to the fork stem are not strong enough to take any real weight, so some extra support will have to be added between the top of the fork stem and the fork legs. This dual support system is often referred to as a triple tree fork. Also, notice how low my handlebars are in relation to the rest of the frame. The rider will have to hunch over to reach the handle bars, but whoever said a chopper should be comfortable? It's about attitude, not comfort!
The top of the fork stem needs to have some kind of support in order to keep the two lower tubes from bending once weight is on the frame. I found two reflector mounting brackets as shown here, which when bent the appropriate way, would fit perfectly between the top of the fork stem and the fork legs, assigning the needed support. You could also make a triangular plate with a hole for the fork stem to do this job as well.
The two reflector brackets are shown installed on the fork stem, adding the needed support the fork legs. A small hole will be drilled in each fork leg so a machine screw can secure the brackets to the fork legs, giving the entire fork assemble much greater strength. Now the fork legs can take the weight of a rider safely.
Well, that's pretty much it. To keep true to the era, I added a banana seat, single speed coaster brake rear wheel, vintage bicycle light, and the crankset from the old exercise bike. Oh, and most choppers from back then had a front wheel that was much smaller than the rear, so I added a 20-inch front wheel. This photo shows the Old Skool chopper before painting.
The Old Skool chop actually rode very well, considering the ultra low handlebars and extended forks. With that huge balloon tire and coaster brake rear wheel, you could lock up the wheel, and fish tail like crazy around the corner, leaving a thick black trail of rubber on the road. The wheelie ability of this chopper was intense thanks to the banana seat, allowing the rider to shift the center of gravity over the rear wheel. Next time you find a bunch of retro junk at the dump, bring some attitude back from the past. Hang onto your welding hats, kids. The next project will appeal to the young chopper enthusiasts.
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