ChopWork Orange - Section 1

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Take a typical mountain bike and transform it into a 1970s old skool chopper with style.

Kids' bikes with 20-inch wheels are abundant at the dump and yard sales, especially the cheap steel frame units. These bikes not only take a beating, but they are outgrown in a year or two, so you will probably find a lot of them at your favorite scrap yard or city dump. These frames are easy to chop, and 20-inch bikes make great choppers, but unless you are only 4 1/2 feet tall, there won't be much leg room on one of these bikes. The problem of size is compounded even more if the head tube angle is taken back to add more rake, as this pushes the handlebars even closer to the seat. At this point, your only option is to move the seat higher or farther back, creating either a goofy looking chop, or a flying death trap that pulls uncontrollable wheelies on so much as a sneeze.

To get a little more leg room on a chopper made from kid's 20-inch frame, two frames will be joined together in order to move the bottom bracket further up. The head tube will also be pushed forward, allowing for a nice long set of forks to be installed without creating a super tall wheelie machine.

The sacrificial lamb is a typical steel girl's frame 5-speed bike (Photo 1), fresh from the garbage heap at the local dump. For this project, you will need two 20 inch frames, and the components to make one complete bicycle. Depending on how you join the frames, the condition of the front half of one frame and the rear half of the other may not be important, as you will soon see.

Photo 1 - A discarded 20 inch kid's bike.

The second frame is again a small 20-inch steel kid's bicycle (Photo 2), most likely another 5 speed or possibly a BMX wannabe. When joining two frames together to create a Frankenstein chopper, it really doesn't matter too much on how similar the frames are, just make sure the rear triangle to be used fits whatever rear wheel you end up using. Since, I planned to use 20-inch wheels all around, the two donor frames are just perfect.

Photo 2 - Second frame to be cut.

It's always good to take everything apart in order to assess what will be usable and what will be tossed. Cracked bearing rings, rusty bearings, bent pedals should all be replaced. Here are the two donor frames and enough guts to assemble one complete bicycle (Photo 3).

Photo 3 - Assessing all of the raw materials.

There are many ways to join two frames together in order to create one longer frame, and depending on the condition and size of each frame, you will have to decide what goes where. In Photo 4, I cut the top tube and head tube from the first frame (top photo), and the down tube, head tube and bottom bracket from the other (bottom photo). I planned on using the rear part of the first frame, and only the bottom bracket, down tube and head tube section from the other as you will soon see.

Photo 4 - Cutting the frames for the fusion process.

As soon as any part is cut, it is a good idea to grind away any left over metal, as the part is easily handled on the workbench at this point. Once you start welding, it may be difficult if not impossible to get the grinder disk into the area that needs to be ground. Photo 5 shows the bottom bracket cleaned and ready for welding.

Photo 5 - Grinding the bottom bracket clean.

I admit, there was no real plan here, just the idea of making a longer, taller frame for a chopper with extended forks. I decided to lay both bottom brackets on the ground and see where the head tube on the front frame would end up (Photo 6). The resulting layout was perfect! The bottom bracket was farther ahead, the head tube was nice and high, the rake was increased, and the distance between the head tube and seat was longer. I promptly tack welded the two frames together right where they sat, making sure vertical alignment was correct.

Photo 6 - Laying out the two frames.

With the basic frame tack welded together, the next step was to fill in the gaps using whatever scrap was cut from the other frames. Since the frame from Photo 6 would not be anywhere near strong enough to hold up to a riders weight, some tubing was needed to create a solid shape. Photo 7 shows a seat stay, cut in half to separate the two small tubes. Let's see where I can find room to weld these on the frame!

Photo 7 - Seat stays cut for use in the new frame.

Two lengths of tubing were just long enough to form two triangles from the head tube to the top of the seat tube (Photo 8). Since the triangle is the strongest shape you can form with tubing, this is a good thing. The two bottom brackets still needed to be joined, so another small section of tubing was cut from the leftover frame to fit between them (shown above not yet connected).

Photo 8 - Two triangles formed formed the seat stays.

The tube running between both bottom brackets almost completed the frame (Photo 9). In fact, I would imagine the frame would be strong enough to right at this point, but something looked missing - just not enough going on in there yet. Besides, I had a lot of leftover scrap from the two frames. At this point, the welds were completed and ground clean.

Photo 9 - Starting to look like a frame again.

I wanted a tube that would form another triangle in the frame, and since the tubing was becoming gradually smaller in diameter from the bottom to the top, I found an even smaller bit of steel rod (from an old fridge rack) to install (Photo 10). Now the frame was made of many triangles, and looked completed. Hmmmm, what else could I weld onto this thing?

Photo 10 - Adding more to the frame.