I've wanted to build a custom bicycle for many years. I started wondering how fat of a tire I could accommodate on a bicycle. I had seen pictures of the Hanebrink Technologies extreme terrain bicycle, but wanted something still more extreme.
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.
Originally I wanted to spoke up a fat tire rim with a standard bicycle hub, but this proved impossible due the the small rim size with the large tire.
After seeing one of the most creative bike ever (see Ode to the Chupacabra on
http://www.ridingthespine.com/Journey/category/chupacabra
I got the idea of using a standard geared rear hub as a jack shaft or transfer hub between the front (bottom bracket) alignment and the rear tire alignment. This also solved the problem of gearing the bike, since I didn't have to mount the gears on the wheel itself. Thanks to The Atomic Zombie for instruction on one of his bike for the widened hub concept and for much other inspiration.
It weighs a lot, but it is a blast to ride and you never saw a bike get so much attention.
It took me a few months of noodling this around in my head and on paper before I started in earnest to create the "Fat Bastard" extreme fat tire sand bike. Hope you enjoy it as much as I do.
Let me also just say, for the record:
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 drivetrain issue. This was for fun! And also to learn how to weld and to see where this project might lead.
IF YOU LIKE, PLEASE GIVE THIS INSTRUCTABLE A GOOD RATING. THANKS!!
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.
Originally I wanted to spoke up a fat tire rim with a standard bicycle hub, but this proved impossible due the the small rim size with the large tire.
After seeing one of the most creative bike ever (see Ode to the Chupacabra on
http://www.ridingthespine.com/Journey/category/chupacabra
I got the idea of using a standard geared rear hub as a jack shaft or transfer hub between the front (bottom bracket) alignment and the rear tire alignment. This also solved the problem of gearing the bike, since I didn't have to mount the gears on the wheel itself. Thanks to The Atomic Zombie for instruction on one of his bike for the widened hub concept and for much other inspiration.
It weighs a lot, but it is a blast to ride and you never saw a bike get so much attention.
It took me a few months of noodling this around in my head and on paper before I started in earnest to create the "Fat Bastard" extreme fat tire sand bike. Hope you enjoy it as much as I do.
Let me also just say, for the record:
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 drivetrain issue. This was for fun! And also to learn how to weld and to see where this project might lead.
IF YOU LIKE, PLEASE GIVE THIS INSTRUCTABLE A GOOD RATING. THANKS!!
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Signing UpStep 1: Getting started - what you will need
What you will need are:
1. The ability to weld. I never welded before this, but wanted to learn. I bought a $99 120V stick welder from Sears and taught myself on this project. It was painful, since the stick welding was pretty dirty so I had to do a lot of chipping (away the slag) and grinding and rewelding. Eventually, body putty covered all the rough (but strong enough) welds.
2. Some steel donor bikes and rigid electrical conduit. I cut up quite a few bikes to get the parts I needed. What parts you use and exactly how you configure the overall frame design are not critical. What is critical is placement and alignment of critical components. I
3. Wheels - I ended up using rear wheels from a Yamaha Blaster atv, because that is what I could find on Craigslist locally. It turns out they were a good choice because of the 4 bolt pattern which I will explain in later steps. Also, you can finda decent selection of used ones on ebay or other places online with tire sizes up to 11x22 (yeah baby!). I started with the wheels and designed the bike out around those. You need to know how wide to make the frame. I actually started with giant blue knobby tires and ended with rounder black knobbies (the first ones were a bit too square and messed with the handling)
4. A bunch of purchased (motorized) go-kart components from BMI Karts. More about those later. And some purchased bike components.
5. Basic knowledge of bicycles and power tools. I bought a 4" angle grinder and used a ton of cut-off wheels, flap wheels and grinding stone to cut and shape almost every component on the bike in some manner. This was a critical piece of equipment. I used my welding gloves and a face shield. I used flap wheels to remove galvanizing from conduits prior to welding. Do not weld galvanized steel. Also used conduit benders for curved framing members.
6. A big piece of cardboard for layout
7. Patience and some creativity
8. Time
1. The ability to weld. I never welded before this, but wanted to learn. I bought a $99 120V stick welder from Sears and taught myself on this project. It was painful, since the stick welding was pretty dirty so I had to do a lot of chipping (away the slag) and grinding and rewelding. Eventually, body putty covered all the rough (but strong enough) welds.
2. Some steel donor bikes and rigid electrical conduit. I cut up quite a few bikes to get the parts I needed. What parts you use and exactly how you configure the overall frame design are not critical. What is critical is placement and alignment of critical components. I
3. Wheels - I ended up using rear wheels from a Yamaha Blaster atv, because that is what I could find on Craigslist locally. It turns out they were a good choice because of the 4 bolt pattern which I will explain in later steps. Also, you can finda decent selection of used ones on ebay or other places online with tire sizes up to 11x22 (yeah baby!). I started with the wheels and designed the bike out around those. You need to know how wide to make the frame. I actually started with giant blue knobby tires and ended with rounder black knobbies (the first ones were a bit too square and messed with the handling)
4. A bunch of purchased (motorized) go-kart components from BMI Karts. More about those later. And some purchased bike components.
5. Basic knowledge of bicycles and power tools. I bought a 4" angle grinder and used a ton of cut-off wheels, flap wheels and grinding stone to cut and shape almost every component on the bike in some manner. This was a critical piece of equipment. I used my welding gloves and a face shield. I used flap wheels to remove galvanizing from conduits prior to welding. Do not weld galvanized steel. Also used conduit benders for curved framing members.
6. A big piece of cardboard for layout
7. Patience and some creativity
8. Time
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I've had the wrong link out there for 4 years.
Thanks for picking that up.
I have corrected it now.
Thanks for all the tips and tricks and steps and thinking you went through with this bike!!!
I made one just like it only started with a Yamaha 7 inch fat tire dirt bike frame and disappeared the motor and transmission and welded in a Schwinn 12 speed bike frame and then proceeded to play with it until it worked. Current rendition has a 3 speed front derailer and a one speed rear. Kept the shocks and the front brake and it rides a little funny as your knees have to be out at a 45 degree angle to avoid hitting the rear shock brackets and it's one really looooooong chain with no jack-shaft like yours.
Handling in deep snow is not great due to weight of bike and geometry. Better in sand.
i cant think of a nicer bike thanks
1 a lock
and 2 a removable chain setup
toward my eventual electric-motorcycle-bobber build!! Just waiting for batteries
tech to be the right prices. -Lee A123 cells are looking better and better...
Trying to work out the details of a light-weight production model of this one.
A tire (27" or bigger around) gives a better "gyroscopic" stability to the bike. Pushed down a hill with the handle bars locked in place, and a bike with 27 inch wheels will practically keep itself upright.
This is why a motor cycle is easier to keep "upright" then a scooter with, say 10 inch wheels.
The tire here, will have to rotate fairly fast to get anywhere near that stability, and they will be heavier. I bet it would be harder, not easier to ride :-)
Without it you would have to set the distance between rear axle and jackshaft precisely.
Also, this allows me to try different size chainrings/sprockets to optimize the gearing.
I sure hope you are 1.9m, not 1.9 cm.
I equate that to about 6'-3" tall.
I am 6'-1" tall.
I think this is a good match.
I happened to use a bike frame that is a large or 19" or about 43cm (bottom bracket to top tube center to center)
So I guess I'll just have to get a 19" frame and I´ll be good to go. Once again: thanks.
How much does it weigh with the "snow tires"? Are you mainly riding it in level "beach" areas, or have you also gone in dunes?