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.
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Step 1: Find a Donor Bike
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.
Step 2: Find a Second Donor Frame
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.
Step 3: Inventory All Necessary Parts
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).
Step 4: Cut the Frame Tubes
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.
Step 5: Grind and Clean the Bottom Bracket
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.
Step 6: Tack Weld the Two Frames
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.
Step 7: Fill Gaps and Make Seat Stays
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!
Step 8: Make Triangles for Strength
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).
Step 9: Frame Is Taking Shape
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.
Step 10: Add More Tubes
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?
Step 11: Front Fork Construction
Before adding any more to the bike, I decided to work on the front forks. The front forks will be a typical set of round tube BMX forks (Photo 11), cut and extended to some length using 1-inch thin walled electrical conduit. The first thing to do was cut the dropouts from the fork legs, sparing as much of the metal as you can since they will be put back on the new forks.
Step 12: Cut the Fork Legs
The fork legs were then cut so that only the vertical portion is removed (Photo 12). Imagine drawing a line from the inside of each leg and continuing it up past the head tube. This is the line that will be cut. This is done so that new fork legs can be installed later.
Step 13: Extend the Forks
The forks are extended by welding two lengths of 1-inch conduit where the original legs were cut (Photo 13). You will have to grind a little away from the original fork material in order to make a proper joint with the conduit for welding. When I welded the fork extensions to the original fork stem, the front dropouts were already welded to the other ends of the fork legs, and a wheel was installed to hold it all in place. The two extension legs are also laid on a flat board to help alignment.
Step 14: Use Leftovers for Pizazz
This leftover chaining fit nicely in the frame as shown in Photo 14. It was at this stage that the bike was given the name ChopWork Orange, because of all the gears, and yes, it would indeed be painted orange.
Step 15: Assemble the Chopper
The chopper was assembled in order to make sure everything was going together correctly (Photo 15). A banana seat, and some wide handlebars were installed to give the bike an old school cruiser look. A fork length was chosen that put the two bottom brackets in approximately the same position they were on the original bike, this would ensure that the pedals had adequate ground clearance.
Step 16: Make a Ghost Ring
Rather than just leaving the rear bottom bracket empty and unused, I decided to salvage the original crank set to create a ghost ring. This secondary chain ring does nothing but spin with the front one, but it will add to the ChopWork theme of this bike. In Photo 16, the arms are cut from the crank set, leaving only the center axel. It is ground smooth as well.
Step 17: Paint the Chopper
Once completed, the chopper was hand painted with a brush using some spare orange paint that was hanging around the garage. The chain rings were painted black to accent the bike, and the chrome was polished up with some steel wool. The completed chopper turned out quite well considering it only took a few hours and started life without any plan (Photo 17).
Step 18: Start Showing Off
The bike looks cool with the dual chain rings (Photo 18). I tell people that this doubles your top speed, allowing the chopper to keep up to city traffic. It of course, does nothing more than look cool!
Step 19: ChopWork Orange Choppers Are Cool!
Once the hard work is done, it's all about looking cool, you know! The chopper is very comfortable, and easy to ride, even for the chopper newbie. Banana seats also let a variety of riders of different heights ride the same bike, just move to a comfortable spot on the seat. Christina takes the bike out for a cruise and it rides like a dream!