Carnage Chopper - Section 1
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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
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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