The Fat Tire Sand Bike designed by Mike Scarani could be the sand-spittin’ scrawler you’ve been looking for. He designed it using no 3D CAD of any sort, but his knowledge based in mountain biking, architecture and a few CAD applications, gave him just enough passion to push the limits of drive train dominance. Here’s the breakdown.
The Fat B@stard
Once you see the bike, the name makes a bit more sense. Developed to ride the east coast beaches, this 21-speed, rear drive sand stomper uses disc brakes and an offset jack shaft to make the terrain navigation a bit more bearable. Mike gives us an overview of his experience, inspiration and why he went about designing it the way he did.
I’m an architect with some experience in MicroStation, Sketchup and Revit, with experience solely in architectural applications of CAD. I had no prior bike designing or custom building experience. Just 24 years of mountain bike experience and interest in any and all types of design.
I did not use any CAD program even though I have some experience with CAD programs. I did all my initial design by hand sketches and then final layout on the cardboard. The primary reason, I guess, is that it was a fluid process. I did not know all of the components I was going to use at the start of the actual construction. I had a general idea, but you can see by some of the earlier photos how the overall frame design changed.
A site called atomiczombie.com was very useful. Brad is a very creative and resourceful guy, and the other people frequenting his website have a wealth of knowledge on the topic of building one-up bike projects that I haven’t found elsewhere on the web. (Also see Ode to Chupacabra Bike (Riding the Spine)
The Design Challenge
In the Fat Tire Instructable he posted that documents the entire process he goes on to mention, “The problem I considered was one of drive train alignment. With the fat tire, the chain had to shift too far outside of the normal bottom bracket to rear wheel alignment, in order to clear the tire width. I also wanted to make this work with gears, as I knew the large tire would weigh a lot.”
One of the most interesting parts of the design process is when Mike went through locating (step 8) and aligning (step 12) the Jack Shaft. Most of the construction and supports were taken off a donor bike and used to mount each component in place after the optimal location had been determined.
“It weighs a lot, but it is a blast to ride and you never saw a bike get so much attention…I did not set out to make the most efficient, or lightweight, or highest performance bike I could. It was all about maximizing tire size and working out the drive train issue. This was for fun!”
