The rollbar will be 40” tall from the floor to its UPPER
side. It will be 62” wide, outside to outside. The top two
bends are 70
o
and the two lower bends are 20
o
.
To de ter mine the total length of tubing needed,
you could sit down and calculate it. Time usually cost
more than tubing, so let’s do it the easy way. Take the
total width of the rollbar (62”) and add it to twice the
height (40”). This gives us a length of 142” (62” + 40”
+ 40”). This is slightly longer than we actually need,
but there’s a popular rule in fabricating: It is easier to
remove material then to add it. Through experience
you will learn how much extra tubing you must leave
to complete the part.
An important rule of bending is, if possible, always
make the bends closest to the center first and work
your way out. This allows you to make measurement
corrections between bends. Based on this rule, place a mark at the center of the rollbar tube. This is shown
below.
BEND 1:
The first bend will be the upper right side bend. The upper dimension of the rollbar is 50”. From the center of
the rollbar to the outside of the bend is 25” (50” divided by 2). Lay the tube to be bent on the floor and hold the
template above and parallel to it as shown below. The scribed side of the template will always face towards the
center of the tube being bent. Using a tape measure, slide the template left or right until it is 25” from its outside
edge to the rollbar’s center mark as shown to the right. Using a marker, draw a line on the rollbar directly below the
scribed line. Since the desired bend is only 70
o
and the template is 90
o
, you will have to use your best judgement
of when the template is 25” out. This gets easier with experience. Take note of what side of this mark the bend
needs to be and draw an ‘X’ there so that when you load the tube into the bender you’ll be bending on the correct
side. Now, load the tube into the bender and make
the first bend. Don’t forget to over bend a little to
account for tube springback. For this material 3 to
4 degrees should be sufficient. Once you know the
correct over bend required, you may want to record
it for future reference.
BEND 2:
Place the template above the rollbar tube with the
reference line facing bend 1 as shown below. Slide it to the desired 50” outside to outside of the two top rollbar
bends. Do NOT use the tube’s center mark as a reference and place the template 25” left of center. The reason
is that if the first bend was not made at the correct position to achieve 25” from rollbar’s center you can correct
this error in the second bend’s position. Mark the rollbar tube exactly underneath the template line and make the
second 70
o
bend.
Erase the center mark on the rollbar tube and mark a
new center exactly midway between the outside of the
two bends. Why? Let’s say your measurement shows
the two top bends are really 50 1/4” wide instead of the
desired 50”. In that case, your old center mark could
be off by as much as a 1/4”. The NEW center mark
corrects this error. With template bending your errors
can generally be fixed in the next bend. If you had
started bend 2 from the rollbar’s center mark you would
not have made the correction. Eventually, every bend
adds a little more error and you end up with a rollbar
that does not fit.
62"
40"
20°
70°
50"
Rollbar dimensions
25”
Template positioned for the 1st bend.
Tube’s center mark
50”
Do NOT use this
mark as a reference
for bend 2
Template’s reference line
Template positioned for the 2nd bend.
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