I get asked all sorts
of questions but perhaps the most common is what can you fit drive
train wise in chassis "X"? Until you have built you first chassis
it's hard to see just how easy it is to make changes to my basic
designs. The following should give you a good idea on how I
would deviate from the plans. In this case I am going to take
a 2 seater design with a rear mounted radiator and change it into a
3 seater with a front mounted radiator.
With the drive train
in position I started on the upper cab. Since I want to put a 3rd
seat in this chassis I deviated from the plans by making the A to B
pillar bars 2 inches longer than called for. While bending these
tubes I did discover a typographical error in my plans. If you
purchased the HR2 Pickup plans see the following
file for the correct numbers.
The box is my radiator
mock up. It is approximately 25" wide, 20" tall and 7" thick.
This is narrower than my existing radiator by one inch so I'll have
to either get a smaller radiator, notch the front tubes or mount the
radiator in back. More on this later.
The longer span
between the A and B pillars gives me the extended cab look I am
A head on view of the
A to B pillar.
The next step was the
double A pillar bar. The cross bar in the picture is to hole
the two A pillars in place side to side until I get to the roof.
After some additional
thought this tube may or may not be in the final version.
After mocking up the rear seat I may need the extra room for entry
into the front seats. To answer that question the front seats
need to be positioned which means the front floor needs to be
designed. When you are working on this part of the buggy you
need to keep transmission/transfer case removal in mind as well as
exhaust routing, front driveshaft routing, legroom, etc, etc.
I used some scrap
tubing to mock up where the front seat mounts were positioned in
relation to the outside of the seats. For this chassis I am planning
on using square steel tubing for the main floor structure to make
mounting panels easier. I also want the whole inner structure
to unbolt for maintenance access.
The floor will step up
from the foot wells a few inches so I would need a tube on the side
of the chassis to mount the cross tubes for the floor. I found
a stack of material that was the correct height and tack welded it
to the frame. This gave me a great reference plane while I
worked to notch the final tube into position.
Next I tack welded
some steel channel to give me a reference plane for the floor cross
tubes making sure I had enough clearance to rotate the transfer case
if needed. I am utilizing some scrap 1.25 x 1.25 steel tubing
for the two cross tubes; two 4" pieces on each side and a
center piece filling in the rest of the gap. Two tabs per side
will be welded to the frame and bolted thru the removable center
Here's the front bar
tacked into place.
It is always good to
double check things. After throwing the rear seat back in the
chassis I am thinking the seat still needs to go back a few more
inches. The seat shown is a PRP preemie seat (22"
Tall X 17" Wide X 20" Deep)
which fits my 5 year old perfectly.
However, since I want this chassis to accommodate the family for the
next 5 years I want enough room in back to go up to the pre-teen
sized seat (28"
Tall X 19" Wide X 23" Deep)
which is basically a couple more inches
in all directions.
Now you will see the
importance of keeping the frame lightly tacked together. With
my drivers seat and 3rd seat in place I cut the welds on the motor
mounts and rolled the motor/trans back a few inches to make room for
my existing 19" tall x 26" wide x 7" deep Ron Davis dual pass
radiator. Next I cut the welds on the front shock hoops and rotated
them outward until I had enough room for the radiator. At the
same time I positioned the front axle so it was centered on the
frame and figured out where the shocks would have to mount assuming
7" of up travel. Based on this I found I needed to lower the
shock hoops about 2 inches.
With the shock hoops
lowered I then re-made the two bars that tie the A-pillar into the
shock hoops (note the new downward angle which actually matches the
The front axle will
actually sit 8" back from where it is shown, I just have to raise up
the chassis but want to wait till I can throw some more welds at it.
Another thing I learned from this mock up was that I may be able to
get away with a single driveshaft (no carrier bearing). You
can see the tube in the first picture goes straight back with very
little angle to the transfer case output. I am hoping this
means I can run in 4 high without a lot of driveshaft vibrations and
I thru a tire into the
mix just to see what a 110" wheelbase would look like (remember the
front axle needs to move back 8").
Back to the passenger
cabin. Using some masking tape I tried quite a few bracing
configurations before coming up with this one which seemed to
maximize rear passenger headroom while still keeping the roofline
low. The rear seat is tucked up close to the two front seats
with the intention of using the space between the two front seats as
legroom. there is enough room that I can move it back 3-4".
Once I was happy that
I could get my 3rd seat in the chassis I started to brace the
chassis side to side by installing a dash bar and upper roof bar
(front). The double A pillars also got moved forward an inch
for more entry room.
Once I get a few more
of the cross bars in I can throw better weld the chassis so its
easier to climb around in. As it is I have had to use ratchet
straps to hold the A to B pillars in place at their correct angles.
On the tool front, my
harbor freight angle finder has been augmented by a digital version.
I highly recommend one of these vs. the one on the left for the
better measuring consistency.