Hard to believe it's been two years since my
first Project Money Pit entry
and 7 years since I first got into
the sport. Over the course of that project I took my
short wheelbase Samurai from a leaf sprung off-road machine to a tubed out 4
linked crawler. I have learned a lot about what works and what doesn't and
have been feeling the itch to take the next step and build a crawler from
scratch. One of the important lessons is also the reason for this projects
ominous name. This hobby can be expensive and it never seems to let up,
hence the addition of "bottomless" to the project name was natural.
Making a Plan
First off this won't be a fast project.
My plan is to have it drivable by winter 2005. I am hoping I can
approach this project in a stepped manner, building it from the drive train up.
I guess this is a good time to list the goals of Project BMP.
Seating for 2 adults and 1 child.
2. The target weight is 2500 lbs loaded
if I stay with a Zuk drivetrain,
2700 lbs. loaded if I go with a Toyota
3. More storage room than Project MP.
4. More robust tubing in commonly
5. Longer wheelbase. 105-109"
6. Better visibility.
Basically I am looking for a recreational crawler
that will seat three but still feel light and nimble. Eventually I'd like
to add rear steer which means swapping in a drivetrain that can handle D60's
would be good to do during the build up in anticipation of the bigger axles down
Chassis: Utilizing what I have learned over
the past few years I plan on making a frame from scratch.
Axles: For now, I plan to utilize my
existing axles. They have served me well and I haven't seen the need to
change them out. I would like to implement some sort of rear steer down the road
as funds permit.
Drive train: I am still up in the air on
this one. On one hand I have a lightweight and dependable drive train in
Project MP but I feel I am pushing the limits of what the stock Samurai transfer
case can take. With bigger axles an inevitable upgrade, this might be a
good time to beef up the drive train and get that step out of the way. The
most logical step is to install a Toyota transmission and dual transfer cases.
This would allow me to retain my existing motor which would be good for the
budget. However, now is a good time to do a motor upgrade too. It
will all boil down to what kind of deals I come across in the next couple of
months as I search for possible parts cars.
Suspension: Links all around. My
existing rear suspension will make its way over from Project MP. The front
will be link with coilovers. Ensuring adequate clearance
between the motor, links, coilovers and steering gear will be one of the harder
parts of this project.
The tubing on Project MP was eventually
mocked up in Solidworks so I could see what it would look like before I started
building it. Project BMP will go to the next step and actually use the
model as the blueprint. The goal here is to model everything possible so I
will know where and how everything will mount before I start bending tubing.
Another benefit to modeling the buggy before I build it is the ability to get
some useful data from the software. Based on the materials I assign to the
parts I can get the weight of the entire vehicle and the center of mass at any
time during the design process.
These images are the result of a couple
weekends and many weeknights of work. The design utilizes my existing
Beard seats and a smaller version for the rear.
Currently I have 90% of the buggy modeled
including a full tank of gas (8 gallon fuel cell), a full cooler (40lbs), two
storage bins, battery, Suzuki drivetrain, and hi-lift (mounted behind the
seats). The present weight is right around 2400 lbs. When I am done
with the design I will do a complete break down of the weights.
Some isometric views. As you can
see I have a narrow front end and 90 degree approach angles front and rear.
The tires shown are 37" tall and the wheelbase is at 107".
Here's a comparison with the Project MP
model. I should note the Project MP cage height is not accurate, it should
be taller. In fact, the overall height of Project BMP is roughly 2 inches
shorter than Project MP.
Somehow I managed to package all that in
a chassis that is only slightly longer than the Project MP chassis.
The main structure of Project BMP
consists of a lot of different sized tubing. Here's the key for the above
Red = 1.62 Dia x .250 Wall
Blue = 1.62 Dia x .120 Wall
Green = 1.00 Dia x .120 Wall
Orange = 1.00 Dia x .095 Wall
Grey = 1.37 Dia x .120 Wall
Black = 1.50 Dia X .120 Wall
The heavy wall tubing shown in red will
be used in the areas my present rig has taken a lot of hits on. These
positions are pretty much the areas most rigs end up pivoting around or take the
brunt of the force when rolling. I am mainly after dent resistance in
these areas, from my experience .120 wall is too easy to dent. Any 1" dia
tubing used for bracing is .120 wall, the .095 wall stuff is used for the cooler
mount and dash. I am going to go with 1.37 x .120 wall on any brace that
should only see compression or tension loads (no anticipated side impacts).
This was done to offset the increased weight in the .250 tubes. The 1.50 x
.120 wall tubes are used in any brace that may see a side impact. The other
reason for using the slightly smaller diameter 1.50" tubing is so when I mount
body panels they will be slightly recessed below the neighboring 1.62 dia
tubing. You may notice I used 1.37 dia tubing for the door braces
which may see a side impact. I plan on having a small nerf bar on the side
like my present rig that will stick out a ways past the door bars. This
serves as a step when getting into the rig and also takes the brunt of the hits
when pivoting around something with the side and on hard flops. My present
door braces are unscathed so I am going to continue using what has worked for
Note - I have made the plans I used to
build this chassis available for purchase, details
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