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Carnage Chopper - Section 1

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*** Featured on and ***

donor bike waiting to be hacked carnage chopper
A mountain bike becomes a sick chopper with steering wheel and ultra long front forks.

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 thought a really long, slender look would be 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.

Photo 2 - Parts are parts


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, 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 where 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 the 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.

Photo 3 - Inverted and extended.


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!

Photo 4 - Tube and bottom bracket welded.


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.

Photo 5 - Separate the front suspension forks.


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.
Photo 6 - Extending the front forks.


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.
Photo 7 - First part of the fork extension completed


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.
Photo 8 - Fork stem prepared for welding.


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.
Photo 9 - Connecting the stem to the fork leg extensions.


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