CARNAGE DIY CHOPPER BIKE
Full suspension mountain bikes with v-shaped frames have become very popular over the years, so it's no wonder that the local landfill has been seeing more and more of the cheap steel versions lately. The typical lifespan of a department store type bike seems to be about three years. Although fully suspended, the inexpensive steel versions have no more quality about them than their non suspended counterparts, and this makes them great for chopping and welding. A full suspension chopper? Nah, what's the point? Of course, the unique qualities of the v-shaped frame were quite appealing.
I came across the idea for this chopper by accident one day when I was moving the giant pile of scrap bike frames from one end of my small garage to the other. This regular ritual involves throwing one frame after the other across a 10 foot distance until the pile was at the other end of the garage. As I tossed this full suspension frame onto the pile, it landed upside down with the rear triangle extended outwards as far as it could travel and voila! An idea came to me as you will soon see as you read on.
The donor bike has a single spring connected to the rear triangle which is hinged just behind the bottom bracket (Photo 1). The frame consists of two nicely curved oblong tubes shaped like a wishbone; this could easily be transformed into a cool chopper with loads of style. The condition of the suspension is not important, in fact, you do not even need the spring for this conversion. Same principle for the front fork suspension as well. This bike was found at our local landfill, and is pretty much shot - no cables, shifters, brakes, and the front suspension was floppy - a perfect candidate for chopping!
I stripped down the entire bike (Photo 2), and found the front rim to be rusted and seized, so it was tossed. The rear wheel had an "old school" chrome rim and sidewall tire, which was good, since I had a matching wheel in a smaller 20-inch size. I always like the smaller front wheel on a chopper, so this turned out ok. As for style, I though a really long, slender look would look great with the cool curves of the oblong frame tubing. The first step was to forge out the basic frame, then see were my twisted imagination took me.
It wasn't at all difficult to make a stylish chopper frame out of the mountain bike frame - in fact, the entire frame only needed a single cut and two welds! As you can see in Photo 3 above, the little seat tube stub was cut from the end of the frame, and a section of another mountain bike (bottom bracket and down tube) was laid in place were the suspension spring used to be. Not only does this create a low stretched frame, but it places the head tube on a perfect angle for some seriously long forks.
The bottom bracket and length of down tube can be cut from any old frame - I chose one with oversized tubing in order to keep the fat tube look. Notice how the end of the tube (opposite the bottom bracket) has been hammered somewhat flat so that it can be welded to the frame more easily.
Because this new bottom bracket was the non threaded type for a one-piece crank arm, I did not have to worry about orientation (no threads), I just put it in place then welded it solid (Photo 4). Even though the rear of the frame is still hinged, the addition of his new tube makes it as solid as if it were welded at every joint. The length of the added tube and the position of the rear triangle prior to welding will determine the rake and height of the frame. For my frame, I wanted the chain stays (which are now on the top) to run parallel with the backbone of the frame.
You will notice that the rear dropouts are now reversed. They could be cut and re-welded, but I left them, as this added some danger and weirdness to the bike. Better make sure those rear wheel nuts are tight, buddy!
Here are the front suspension forks taken apart (Photo 5). There is a long bolt that has to be removed under the plastic cap on each top end of the fork legs. Once the bolt is taken out, the forks just fall apart. Not much of a spring in each leg; it's no wonder why the suspension felt so weak. Toss the springs on your junk pile for some other evil contraption, as they will not be needed for this fork extension.
You may want to leave the horseshoe shaped bit of steel that joins the two lower fork legs together. This piece adds strength to the fork and prevents twisting. It may also help in aligning the extension when it is built, or be a great headlight, fender, or human skull mounting plate. I hated the look of this thing, so I promptly hacked it off, but it's your decision.
To extend the forks, I found a pair of 50-inch long lengths of 1.25-inch electrical conduit, and wouldn't you know, it fit snugly over the end of the lower fork legs (Photo 6). Because of this, alignment of the fork legs to the extension tube would be a "no brainer", just put them in place and weld. Since the front forks were to be longer than 4 feet, 1.25 inch conduit was just right. One-inch conduit would be a little too flexible for my taste. Muffler tubing would also work for this.
Getting here was easy, just drop the fork leg into the conduit, and weld it solid. I took this opportunity to fully weld and grind the joint, as it would be much harder to do once the forks were completed. Photo 7 shows the welded fork legs.
The fork stem would be fairly easy to join to the fork leg extension tubes since it had a square tube originally connecting the stem to the fork legs (Photo 8). By cutting the original top legs from this square tube as close to the joint as possible, it would be easy to weld the new fork extension legs in place. Once cut, the area was ground slightly to clean up the mess and restore the round profile needed to make a good fit with the conduit.
To connect the stem to the fork tubing, I measured from the top of each leg, and marked a point that would place all three tubes at the same height (Photo 9). As you will see later on, because of the traditional triple tree design, the fork stem and both fork legs needed to be at the same height. I also had a front wheel bolted to the fork dropouts and then laid the entire unit on a flat board to aid in alignment. The distance between the top of the fork legs is almost exactly the same as the distance between the lower fork legs or dropouts, about 5.5 inches. You could make the distance between the top of the fork legs whatever you want, but I think it looks best if they are roughly parallel all the way up the bike.
Once it was tack welded solidly, I checked the entire fork for alignment by looking down the length while the front wheel was installed (Photo 10). If all checks out, then apply the final welds to the fork stem and fork legs, if not, you know what to do (chop, chop). If there is only a slight misalignment between the legs, you may be able to just twist the fork while holding the wheel solid to put it back straight. If the entire thing looks like it was thrown off a bridge, then break those task welds and try again.
The top of the triple tree fork design will be a flat plate bolted to each fork leg and secured to the fork stem via gooseneck stem. Simply cut the top section from an old steel gooseneck so that at least 2 inches of the stem (tube with the angle cut at the bottom) remains as shown in Photo 11. You will not need the bolt and wedge, or the clamp part of the gooseneck.
The top of the triple tree fork is just a bit of plate or flat bar rounded at the edges to conform to the width of the fork legs (Photo 12). A hole is drilled at each end to approximately the center of each fork leg, or to allow a bolt to pass through the plate and meet a nut welded into each fork leg as will be shown in the next photo. You may want to weld the two nuts in place first, coming back to drill the holes in the plate later, just in case the two nuts are offset in the fork legs as the ones I used were.
If you really wanted the holes centered on the plate, the nuts would either have to be large enough to fit snugly in the fork tubing, or a washer would have to be welded in first, then the nuts into its center hole. The method I used here (using half inch nuts and bolts) works just fine, and is plenty strong for this design.
Photo 13 shows the 1/2 inch nuts welded into the fork legs. Since the diameter of the nuts is much smaller than the inside diameter of the fork tubing, they are only welded along one side. This method offers plenty of strength. The nuts should be flush with the top of the fork tubing, and end up as much in the center as possible. The holes in the triple tree top plate are drilled to match the location of the nut centers.
Here are the completed triple tree forks installed on the bike (Photo 14). Notice how the top plate is rounded around the edge of the fork legs. This gives the bike a professional look. The nice thing about this triple tree design is that it does not restrict you on what type of handle bars or gooseneck you have to use. The top of the plate is blank, and you could weld the clamp form the butchered gooseneck back to the top for a standard set of handlebars, or go for something more radical like I plan to do as you will soon see.
Since the top of my workbench was clean (rare event), I decided to get out the jigsaw, some scrap steel and work on some eye candy for the bike. Photo 15 shows a cool looking evil spike thing I cut from some paper to install on the rear dropouts (drop-ins on this bike). I like to work with paper and scissor for this kind of thing, as it is easy to make adjustments then trace the design onto the desired material.
The shapes are cut from the steel using a jigsaw with a steel cutting blade (Photo 17). Take your time, especially around sharp corners and your blade will last a long time. This blade is quite a few years old. If you have to start cutting in the middle of the plate, drill a 1/4 inch hole just outside the cutting line to get the blade in.
Since the jigsaw and sheet metal were already laying on the workbench, I decided to make a custom rear fender using the same method as the dropout spikes. I cut two sides and a center strip out of the steel (Photo 19), and they will be welded together to form a fender. The center strip is longer than the side parts because it has to fit around the curve. Those boring formulas you learn in math class do actually come in handy some day!
To ensure that your fender will be solid, and for that professional look, the entire length of the joint on both sides of the center strip should be welded (Photo 22). It's best to weld with the amperage a little low, even though the weld will be chunky. We are going to grind it all away anyhow. Do a bit of extra grinder work, rather than fill in a burn through on this part of the build. Do not weld inside the fender, or it will warp out of the sides.
If you have some patience, the finished fender will look factory pressed after you grind the welds (Photo 23). I always do the rough grinding with a heavy disc, taking the weld area almost flush with the metal, then I switch to a cut off disk for the fine work. Once the fine work is done (this includes re-welding pits and holes), I use a sander disk to clean it right up.
Welding the small missed areas and pin holes usually takes two or three tries to get right, so have patience and you will be able to make a perfect fender. Your grinder is your best friend when doing this kind of work.
The fender was welded in place just inside the seat stays in order to hide the welds (Photo 24). Three short welds per side are plenty to hold the fender in place, and I would avoid welding the entire length or you may end up warping the frame, fender or both. It's best to weld the fender in place with a wheel installed, so you can make sure nothing rubs. If you are caught riding a chopper that has parts rubbing, you will be beat with an ugly stick and run out of town - do it right!
Yes, it's an old skool racing steering wheel (Photo 25). When I was a kid, I always wanted to build a chopper with a steering wheel, but always got caught trying to take the one from the family car, so now was my chance. Will this even work, you ask? Why not? You hold on, you turn - what's the difference if it's a bicycle handle bar, steering wheel, or axe handle? None, just as long as you can turn the forks.
Since the top of the triple tree plate was blank, all the was needed is two bolts welded to the top that would hold the steering wheel. I found some old wheel stud bolts that would fit the holes in the steering wheel just fine.
I placed the bolts tightly on the steering wheel, held it in the proper place, then tack welded the bolt heads to the top of the triple tree plate (Photo 26). The steering wheel was then removed and the bolds were welded all the way around and then ground clean. Putting a steering wheel on a chopper was not that hard to do after all!
The seat base is cut from 3/4 inch plywood and placed directly on the frame and fender (Photo 28). The two steel sides cut earlier hold the seat snugly between the retired bottom bracket, no bolts are necessary. As for padding, I plan to glue some rigid black foam directly to the plywood and leave it as is - no vinyl. Rigid black foam looks fine with no covering, and is very resistant to wear and moisture.
I threw the bike together to make sure all the components fit and had proper clearance (Photo 29). Everything looked just right, and the steering wheel gave the bike a unique look indeed - a cross between a car and chopper, hence the name Carnage. I chose a minimalist front chaining and crank set from am old BMX, and then cut the chain to fit on the mid rear cluster gear. I resisted the urge to test ride the bike, I wanted to take it out fully painted for the first time.
In line with the car-chopper fusion theme, I installed the brake lever as though it was a stick shifter. On a motorcycle, this kind of installation is called a "suicide shift", since you have to take your hand of the steering to us it. Kind of ironic that this is also the brake, don't you think? As shown in Photo 31, a small stub of tubing from a handle bar is welded to the frame so the lever can bolt on to it.
The next few photos show you how to get a decent look from a spray can without having a proper area to paint. I hung the frame from the clothesline in the backyard with a bit of rope (Photo 32). Try to get the frame hanging in the center of your yard if possible, and move anything important at least 10 feet away from where you are painting. Windless, bug-free nights are best if you have such a thing in your area.
First, I take a can of metal primer, shake it vigorously, then just apply a light dusting using quick strokes at about 10 inches from the frame. Do not spray directly at the same spot. Always do it in strokes. The first coat of primer should look like it does in the photo, just a very light dusting, no more. Let it dry for 15 minutes.
Once the first light dusting coat of primer is dry, you can fully coat the frame with primer (Photo 33). Again, shake the can often, and only make short back and forth stokes with the can held at least 10 inches from the frame. This will take a while and may use more than one can of primer, but will result in a run-free well coated finish. To get to this stage, I used the entire can of primer. Be sure to get the entire frame from all angles - lay on the ground if you have to.
This coat of primer should set for about an hour. How does your lawn look now?
Once your primer has dried, and if the neighbors have not called the cops on you for stinking up the neighborhood, you can now start painting the frame. The first coat of paint should be done like the first coat of primer, just a light brushing of paint, not worrying about all the blotches or missing spots (Photo 34). The idea is to just dust the frame so the next coat will take.
Let this first paint coat sit for about half an hour or so. If the sun is out, it will dry even faster. If it rains, you're screwed!
Now you can fully paint the frame, using the same side to side strokes with the can held away from the frame. Shake the can often, and do not spray the same area over and over. Keep moving around the bike, dusting the frame until the actual color starts to become uniform and solid (Photo 35). You will probably need 1 full can of spray for a frame this size. If you take your time, moving around the frame at all times, the final paint will be a smooth, run free coat.
Although the paint will not be nearly as scratch resistant as a professionally done powder coat, it should look just as good.
The painted and assembled bike is sleek looking unique chopper / muscle car fusion. (Photo 36). A huge light was added to the top of the forks, and the frame was painted black at the tips of the forks, dropouts and head tube. The suicide brake lever was connected to a side pull brake, hidden under the rear of the frame, and it does indeed work.
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