One day while relaxing with a pencil and notepad, I began to draw
a chopper frame that had free flowing lines and curves in the frame,
something that would have been difficult or impossible to achieve using
tubing of any kind. At the time, I did not really consider building
such a chopper since I mainly used round or square tubing for frame
building, and such lines would not be possible.
Then, I remembered seeing one of those chopper motorcycle shows on
TV where they would form a gas tank using sheet metal, welding the
corners so that just about any shape could be created. I thought, “Hey,
why not build an entire custom chopper frame out of nothing but sheet
metal, essentially creating every single tube from scratch so that it
would look more organic and free?”
The idea sounded like an insane amount of work that only the most
hard core garage hacker would ever attempt, so in traditional Atomic
Zombie fashion, I began cutting that same day!
I’ll warn you ahead of time – this build involves a huge amount of
physical labor. Sure, anyone with a cheap AC welder and hand held
grinder can do it (that’s all I own), but be prepared to sweat and work
muscles you didn’t even know you had. If this was easy, every bike
freak would do it, so you will certainly have something unique if you
have what it takes to see it through to the end. You have been warned!
Originally, I planned to create this “no tubing” chopper as a plan for our
AtomicZombie.com
website, but I realized that not many people would be crazy enough to
build a complete frame from sheet metal. Instead, I decided to do it as
a free source of information that would showcase what can be done with
only a basic welder, an angle grinder and a $100 worth of thin sheet
metal. The other issue that made this build unsuitable for a DIY plan
is that there are no measurements – seriously!
I just took a marker and began to draw free form shapes like forks
and frame tubing right on the sheet to be cut out. This build will
require you to release your creative energy because I have no idea what
the angles or dimensions of any of the tubes are, nor would I have any
idea how to even measure such complex shapes.
What I did know ahead of time was how far the wheels will be apart
(wheelbase), how long the forks will be, and where the bottom bracket
needed to be so that I could reach the pedals (about 32 inches from the
end of the seat). Other than that, I took very few measurements, and
simply based the “size” of the Terminator on my favorite three
choppers, stealing ideas and features that I liked from each one.
Figure 1 – OverKill was my first chopper to use a car wheel on the rear
The Terminator had to have a car rim on the rear – that was a must.
After trying this crazy modification on my first chopper, OverKill, it
just seemed silly to go back to some skinny little tire, or department
store chopper rear wheel.
As shown in Figure 1, that 15 inch wide car tire puts those 4 inch
wide department store chopper wheels to shame, almost mocking them.
What really blew me away was how smooth OverKill was to ride, even with
that 60 pound monster on the ass end. Another benefit to using a car
rim is that you can pick them up free at just about any metal scrap
yard and add a few dollars worth of bicycle spokes to create the entire
wheel.
It is certainly not difficult to add spokes to a car rim (as you
will soon see), and like all things custom, it’s simply a matter of
doing a little manual labor in order to create something you can’t
purchase. In the world of custom bikes, money ain’t king, only your
ability to pour some sweat and blood into your work (I mean that
literally).
Figure 2 – The Gladiator Trike Chopper was very comfortable
As for seating position and handle bar height, I found the Gladiator
Chopper Trike to be about perfect for my riding style. This chopper has
two car wheels at the rear, a springer front suspension, and a full
recumbent style padded seat. Besides the fact that it took a little
effort to get those huge boots rolling, the Gladiator was a real smooth
cruiser that I would often ride for hours at a time.
I decided to base the general size and wheelbase of the Terminator
on the Gladiator, so I found a bucket that was the same height as the
seat on the Gladiator and then took a measurement from the top of the
bucket to the position of my heel when extended outwards.
Other than your leg length (inseam), you are free to do just about
anything you want on a chopper, creating a massive 5 foot rise on the
frame, or keeping it mean and low. Just grab something to sit on, drop
a pair of wheels on the floor (front and back), and imagine your
chopper. You could even prop up a few broom handles, or bits of tubing
to get an idea of what you might like for fork length and frame height
as well.
Sometimes I put down the wheels and bucket to sit on then take a
photo to manipulate in Photoshop or simply print it out and pencil in
the rest of your frame. Seriously, don’t get too technical, or you will
wind up spending our valuable time in some forum squabbling about rake
and trail when you could be building your chopper!
Figure 3 – The Vigilante was my first attempt at building a square tube frame
When I decided that I would attempt the Terminator build, I set two
rules: there will be no tubing used in the entire frame besides the
small necessary bits such as the bottom bracket and head tube, and
everything else will be made from flee flowing shapes made by welding
sheet metal into custom tubing.
One of my first attempts to avoid round tubing can be seen in Figure
3, the Vigilante Chopper. For this chopper, I used only square tubing,
and it was all installed at 45 degrees, creating a diamond shaped frame.
The “theme” was to make the Vigilante look like a stealth bomber
featuring a flat black body with many sharp edges and contours. The
Terminator will also have sharp edges in the frame tubing, but also
free flowing curves, creating a kind of carved look throughout the
frame and forks.
Figure 4 – Starting with the front forks
One of the only planned measurements on the entire build was the
length of the forks – 5 feet long. The reason for this is because it
looked good on my other choppers, and because the scrap piece of sheet
metal shown in Figure 4 just happened to be 5 feet across. The sheet
metal you will need should be non-galvanized (not shiny silver) and
have a thickness similar to that of bicycle tubing (between 14 and 16
gage).
Don’t worry too much about the sheet metal thickness if you can get
a good deal on some scraps. It might be a good idea to bring a bit of
bicycle tubing along with you and tell the supplier that you want a 4
by 8 sheet of whatever they have that is close to the thickness of the
round tubing.
The sheet I used was a 4 foot by 10 foot sheet of 16 gage mild
steel, and yes, the damn thing was heavy, just like your chopper will
be when you are finished making the frame! If you want a lightweight
bike for touring the countryside, then you are reading the wrong plan.
Since the only goal so far was to carve out a 5 foot long fork for
the Terminator, I just hand drew a few arcs on the sheet as shown in
Figure 4 so that my forks would have a profile similar to a machete.
This is where you must put your artistic brain to work, as there are no
rules when you are making your own tubing from scratch.
If the tubing has a side wall of less than 1.5 inches, then the
frame will be extremely strong and able to support just about any
rider. In Figure 4, the pointed end shown on the left of the photo will
be the wheel end of the forks, and the other end will become the handle
bars. The handle bar end of my tubing is will create a shape with a 1.5
inch profile.
Figure 5 – You will need a decent stack of discs for this project
To cut out the side walls that make up each tube, you will need a
good supply of patience, as well as grinder discs like the ones shown
in Figure 5. The disc on the left is a 3/32 cut off disc (zip disc) and
the disc on the right is a flap disc (sanding disc).
A zip disc is a great tool for cutting along marked lines on sheet
metal, and you can even follow curves if the arc is not too small.
The flap disc is used to remove razor sharp edges after cutting the
metal with the zip disc as well as cleaning up mirrored parts so that
they are both identical. Although this is only a guess, you will
probably use at least 10 zip discs and five sanding discs for this
project, so look for deals on multi packs. A good full face shield as
also a must when you are working with the thin zip discs and doing so
much cutting.
Figure 6 – Cutting sheet metal with a zip disc and a jigsaw
As shown in Figure 6, a jigsaw with a metal cutting blade can also
deal with the sheet metal, but it takes a great deal more effort and
time to cut so many lines with a jigsaw. I highly recommend that you
get used to handling the grinder for cutting and leave the jig saw only
for intricate curves that may be too difficult to cut with the zip
disc. The grinder is the ultimate tool for any garage hacker, so become
one with it, making it feel like an extension of your own arm!
The first of the four sidewalls for the forks are shown being cut in
Figure 6. The zip disc took about 5 minutes, whereas it took over an
hour to make it half way across the first line with a jigsaw, and wore
down a brand new blade.
Figure 7 – The first front fork side wall cut from the sheet
The first shape is shown in Figure 7 after cutting it free from the
sheet using the zip disc. After cutting out the metal, the flap disc is
used to clean up the curves and to take off the razor sharp edges along
the cut lines. When making two identical shapes, the first one will be
used as a template for the second since it would take an engineering
degree to figure out these random curves using math.
Figure 8 – Tracing out the second front fork shape
The nice thing about using the zip disc to cut curves is that you
don’t have to be perfect with the marker since the lines will be
“smoothed out” by the action of cutting with the grinder. Once cut, any
ripples or mistakes can be cleaned up further using the flap disc as
well.
Figure 8 shows the magic process of drawing an identical freeform shape for cutting – using the first piece as a template.
A sharp black marker is the best way to draw a visible line for
cutting, and makes tracing a new shape very easy. Since we are making
side walls, there are no front and back sides, so it doesn’t matter
which way you cut out the shapes.
PART TWO coming soon…stay tuned