Fat Tire Chopper Bicycle

Discussion in 'Photos & Bicycle Builds' started by graucho, Feb 11, 2009.

  1. graucho

    graucho Active Member

    It's time.:devilish: Building mini choppers and 2 1/2 years of dabbling with MB's It's time for me to
    combine one sport bike with another.

    I've spent 3 weeks working on a frame to fit a 6 ft. adult rider. I saw this frame design a
    year ago and couldn't stop thinking about it so I gave it a whirl. Not as easy as I thought.

    In tradition of keeping a radical bicycle look, the frame is designed with a single down tube.
    Of course keeping a peddal drive train. (different than my mini choppers)

    Im going with a 45 to 47 deg. rake, with a 24" 72 spoke front wheel. Chrome billet forks.
    I'm not building the rear frame until I find the ultimate 11"wide x 23"tall rear tire/rim combo.
    The head frame is bowed, to accept any engine style. I may start with a HT to save costs.
    If I love the bike I may upgrade.

    This will be a slow going project due to a busy life. This is where i'm at so far. I'll keep this
    thread updated as things progress. graucho

    Attached Files:

    Last edited: Feb 11, 2009

  2. junkyard

    junkyard New Member

    looks good so far....love the frame
  3. Mountainman

    Mountainman Active Member

    nice looking and clean
    easy to see
    will be a fine machine

    that frame THING is sweet --
  4. graucho

    graucho Active Member


    I made a little more progress. I got the rear wheel/tire so I will be able to come up
    with a design for the rear frame/jackshaft. for the fork i'm going with a 45 deg. rake
    for a little more stability.

    I have to keep the engine on the "up and up" since im sure I will be pulled over plenty.

    This bike will not be for riding to work etc, just for the experience of the ride. Fun fun fun. More to come.

    Attached Files:

  5. azbill

    azbill Active Member

    it's gonna take some power to get that much rubber rollin' !!!
    that is gonna be a cool ride :):):)
  6. srdavo

    srdavo Active Member

    That's what it's all about!!

    and it's gonna take some brakes to get it to stop!!
    agreed..... a very cool ride! :D
  7. wcocc

    wcocc Guest

    I have a similar frame, bought it from alan at us choppers, did you get your idea from the same bike? they look exactly the same. I am going to primary drive/ belt drive my frame, bike etc, I think I might need more than the standard 2.5 hp to move this thing. Its a very heavy frame! Keep us posted, I want to see what you come up with, my tire setup is going to be off a motorcycle, 16 incher with the belt drive on it. etc. etc. Can wait to get it done.
  8. graucho

    graucho Active Member

    Thanks mike! yes I ordered one for a template. My dimensions are slightly different. The shape
    is the same. I have 65.00 bucks in the pipe and 15 hrs labor. Im planning on making a series of
    choppers with this design with a youth group. To teach them welding and basic chopper design.
    They get a cool chopper bike in the end that they made themselves. (witout engine)
    I just have to figure out how to raise the money locally to help the costs of there builds. (very low income group)

    Yes mine is heavy. My rear tire alone is 35 lbs. You got my interest in the belt drive. That would
    be the cats meow. Im not sure on my powerplant yet. Im hoping to keep it street legal. Any ideas?

    I want to keep mine low, I found some drawback bars for it.

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  9. graucho

    graucho Active Member

    Your not kidding. This will be a heavy ride. (Solid) Ill end up with front and rear disk brakes. It wont be built for speed. Just a cruiser. 20 mph. But yes, I need it to stop for my well being. :smile:
  10. stude13

    stude13 Active Member

    hooper imports has the honda 50-70-90-110-125cc clones for about 325 bucks. i have a 70cc w/3spd auto. the cool thing is an embossed number 48 on the barrel. it is the same motor that akvan uses to drive his trike. he had that thing loaded down with a pile of stuff and said he could get over 45mph. im building a very heavy occ chopper trike and will use my 70 (48) on it. goucho if you go to hooper import llc's page the list near the bottom has bikes built in a program that sounds similar to yours. mitch
    Last edited: Feb 16, 2009
  11. graucho

    graucho Active Member

    Last edited: Feb 17, 2009
  12. stude13

    stude13 Active Member

    i really enjoy your work. did you see the high school projects on hoopers site? im going to wire mine just as your example and pray it works. i was amazed with the power akvan had, in fact he said he could have used a 50cc and had pleanty. mitch
    Last edited: Feb 17, 2009
  13. graucho

    graucho Active Member

    Yes Mitch, those bikes were amazing.

    I rounded up all of my axle parts. Now I can weld up the rear frame around that fat tire.

    Attached Files:

  14. graucho

    graucho Active Member

    Slid the parts together to check the fit and take a peek of how it will look.

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  15. graucho

    graucho Active Member

    I was digging through inventory and stumbled across this minibike 97cc lifan engine I had shelved. I was doing a little dreaming and thought since I was stretching out the bike I could mount it behind the seat, and I could leave the open frame area "open". Then keeping the smell, noise behind me.

    Before I took the tank off I put a little gas in it, pulled it 4 time and it fired up after 3 years. This 97cc's going to have to work a little to pull the bike. But not any more than a 250 lb. guy on a 35 lb. bike with a 20 lb. happytime.

    On the other hand...I change my mind on bike designs everyday. Who knows what i'll end up with. :jester:

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    Last edited: Feb 20, 2009
  16. robin bird

    robin bird Member

    Wow you sure are an incredible artist
  17. SimpleSimon

    SimpleSimon Active Member

    graucho, I really admire your work. I gotta say, though - your shop is entirely unreasonably neat, tidy, and clean.

    Fine stuff.
  18. graucho

    graucho Active Member

    Thank you guys. My shop does get trashed often. The photos must have been on a good day. :smile:

    I have been working on the rear frame and engine mount for the fat tire. Its been 8-15 degree's in the garage. Burrrrrr. I must love this ****.

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  19. graucho

    graucho Active Member

    I found a neat headlight from a 12v kids electric "Razor" motorcycle. In my photo its just sitting on the fork, i'll have to do a little fabricating. There are some plastic parts so we'll see if it lasts. It was free so thats no loss in $, only time.

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  20. graucho

    graucho Active Member

    Jackshaft set up

    Here's the raw section of the jackshaft set up. the shaft will be trimmed on the final set up. Im sure i'll finetune the sprocket ratios when i'm up and running. I set the engine in place to show position.

    I was asked how long the bike is? I stretched it to 7'11in. so it fits in my 8ft utility trailer. I was also asked how hot will the seat/rider get with the engine underneath/behind? There is a heat shield that mounts on top of the engine. We'll find out. :smile:

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    Last edited: Mar 3, 2009