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Thread: Fat Trike Build

  1. #1
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    Fat Trike Build

    I am going to start my fat trike build this week. Its going to be half MTB, half cruiser. Im building it as a trail capable, kid carrier. It will have a removable bench in the back for my 5 year old and 3 year old. Im mostly building it as a fun project for family rides to the beach and for some mild trail riding.

    I want to build it full suspension, but will probably build it rigid to start and possible add suspension if its needed later. I will use my "lightweight Klunker Build" as a starting point. It will probably end up with a 3x7 drivetrain with a gear reduction after the jackshaft.

    I have almost everything I need to build it, except a front wheel. I need to decide if I want to spend the $$$ for another fat wheel and tire, or if I want to build a double rimmed wheel from parts I have on hand.

    Ill post pics as I go.

    Here is the bike I am starting with...


  2. #2
    Thumper
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    subscribed and Good Luck. Love customizing stuff.

  3. #3
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    Subscribed. What frame is that?

  4. #4
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    in on this !

  5. #5
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    this i want to see........i have a trike that i want to bastardize into a fat trail capable rig

  6. #6
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    Thanks guys! The frame is actually a Next cruiser frame. Its aluminum and surprisingly light. My cruiser is only 22.4 pounds, and thats with regular tubes, a coaster brake, and an old Rock Shox Judy SL.

  7. #7
    N8R
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    So it sounds like you are making a delta trike and not a tadpole trike? Cool either way, I like both kinds. Delta trike will be more family friendly I would think.

  8. #8
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    2 rear wheels, 1 front. I suppose that's a delta trike.

    I plan to have the rear bench for the kids removable, so I don't have to carry the extra weight when it's just me. I may even have it so that there are different attachments that will fit on the rear. Like a little BBQ, or a keg!

  9. #9
    N8R
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    Yeah, that's a delta trike. This will be a cool build!

  10. #10
    N8R
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    For what you are doing, I think the delta trike will be better because it will be 2 wheel drive and have 2 wheels under most of the load. More traction. The tadpole would have one wheel in the rear and half the traction. Aired down 2WD fatrike in the snow should be really cool.

  11. #11
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    I absolutely agree!

  12. #12
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    I started to get some parts together that i am going to use.

    So far I have the fork off of my Beast, it has a disc mount. I have a pair of 26x4 tires from my beast, but I may get 3 Devist8rs for this build. I have an ok set of pedals i forgot i had too.







    I also made the jackshaft. I want to use as many parts I have already, so I started with a rear freewheel hub that I have. I turned the end of it down a bit, and rounded out the inside of a cruiser cog to weld to it. Ill let the pics do the talking.













    As a side note:
    Its best to do welding on a hub with it totally disassembled. That way you sone boil the grease, and have to rebuild it, like i did...

  13. #13
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    Looks like it might be hard to lace spokes behind the new cog. S bend maybe?
    Latitude 61

  14. #14
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    No spokes on this hub. It's now a jackshaft. The cog I welded on will have a short chain that runs to the rear axle.

  15. #15
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    Cant wait to see this thing finished.

  16. #16
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    I did the gearing calculations:

    Crankset is 24/34/42
    Cassette is 13/28
    Jackshaft to axle dear reduction is 50%

    So hi gear will be 1.61-1 and low gear .42-1. That should be a relatively useful range based on what I want this bike to do and the weight of it.

    In comparison to my other bikes:

    Fat Trike: .42 low gear; 1.61 figh gear
    Fat Bike: .52 low gear; 2.0 high gear
    Yeti 575: .61 low gear; 3.72 high gear

  17. #17
    N8R
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    If you are going to use the stock Beast tires I think it would be cool if you welded up some 7"-8" super wide rims and spread those suckers out for a massive footprint. I was playing around with mine, and if you spread out the tire beads the Beast tire is capable of getting super fat with a much wider rim which you could easily make by widening regular rims if you have access to a TIG. You could have another set of narrower rear wheels with the devista8tors on them to swap out when you want narrower tires.

  18. #18
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    That would be cool. But I've only got access to a MIG right now. Another thought I had was to make it a dually in the rear, but thats for after its on the road and riding.

  19. #19
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    I got a couple more parts for this build.

    I found a set of Hayes Hydraulic disc brake with 203mm rotors for $40 on craigslist. I also got a pair of lights from a buddies motorcycle. I think they are off if a newer Triumph. Not exactly sure how Ill use them, but they are pretty sweet and were free. Im thinking of making a 12v battery pack and swapping some LED bulbs in.



    Now I need to see what I am going to do for a front wheel. I can get a 26x4 wheel with a disc mount for $140 from a local shop.

  20. #20
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    Quote Originally Posted by blown240 View Post
    Im thinking of making a 12v battery pack and swapping some LED bulbs in.
    Any particular reason you are thinking of doing 12v? Have you done much with loose LEDs? If you haven't, it may be worth some time reading up on the DIY light forum. I've spent hours just reading random threads there and have learned a ton, yet still know so little compared to some of those guys. I know it's a very small part of your build, but thought I would mention it. Can't wait to see the work as it progresses!

  21. #21
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    Only reason I was thinking 12v was because that's what the motorcycle these lights came off of was. I figured that there is a replacement LED bulb that will plug right into the stock socket, and it would probably like to see 12v. I know zero about bare LEDs though, so I'll do some reading.

  22. #22
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    This is getting interesting...

  23. #23
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    I finally got some garage time yesterday, and was able to get some work done on the Fat Trike.

    I used the fork, stem, and bars that came stock on my Beast. Also the stock front hub, and a spare rim that I had laying around. I had a random set of spokes too, that just happened to work nicely as a 2 cross.

    Here is the bike with the fat front:





    Then I got to work on the back. I really wanted to avoid having to make supports that ran up to the seat post, and I think I found a good solution. I used a couple of stamped steel channels that are for a garage door opener. I bolted them in with the rear jackshaft/hub. Then I bent them so that they sit on the kickstand mount. Later ill make a brace to reinforce this area a bit. Im pretty sure this will be strong enough to not have to use kickers up to the seat post, and it gives me something to build the rear trike portion off of.

    Here are some pics:



















    Thats it for now. Hopefully I'll get more time with it later in the week.

  24. #24
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    Now that I have bandwidth again on photo bucket, I can do a much needed update to this build.

    I was able to go for my first test ride tonight. It went OK, but not great. Its strange to ride a bike that doesn't lean, and I overlooked 1 BIG thing....

    First some pics to show where I'm at with it:














    So I think it looks really cool. And I know that when I get the bench on the back for the kids, they will LOVE it.

    But heres where I screwed up. My idea for the rear hubs was terrible. Basically I just took standard cheapie front hubs, knocked the races out of them, slid them onto the axle, and drilled a hole for a grade 8 bolt to bolt them on. The problem is that I underestimated the force that is on the hubs when turning. Both wheels drive, so there is a lot of drag as one wheel is forced to slide sideways when cornering. This force caused the grade 8 bolt to rip thru the hub body. I should have known the hub bodies were not strong enough, but I never thought about it.

    This pic is after about 100 feet of riding on the street in front of my house:



    So my next step is to make some new hub shells out of DOM tubing, then ill weld them to the hub flanges I have, or maybe make some hub flanges.

  25. #25
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    This is awesome!!! Just found this thread I'll be watching it for sure.

    Have u thought about a rear diff? Reason I ask is ur going to find that ur going to run like crap with weight on the back, rear traction will overcome any front traction u have and ull push badly.

    Reason I mention it is last year I started toying with similar idea, just mtb trike nothing as bad ass as a fat trike. Money issues put halt on that and have some parts I got sitting in a box atm lol. Ur build has me now revisiting this coupled with I stumbled across the box last night.

    Looking forward to seeing ur build finished and in action

    Sent from my Nokia Stupidphone using Tapatalk

  26. #26
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    There are still a lot of people racing trikes here in the UK.

    They have probably solved this problem, and will have suitable hubs.

    You may have already seen this site, but if anyone else is interested in trikes it's worth a look:

    Tricycle Association UK
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  27. #27
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    Definitely want to watch how this build works out. I have an old Worksman trike sitting in the shed I've always wanted to put fat tires on.

  28. #28
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    Thanks for the replies!

    I have never seen that trike website. And I realized I am going to have to do some kind of differential. It will most likely be in the form of a double freewheel.

  29. #29
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    Re: Fat Trike Build

    Schwinn Town and Country trikes have a proper differential gear set.

    sent remotely

  30. #30
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    Quote Originally Posted by squareback View Post
    Schwinn Town and Country trikes have a proper differential gear set.

    sent remotely
    Thats true, but they are only 1 wheel drive technically. I want to have a double freewheel, that way when I am going straight, both wheels will drive.

  31. #31
    N8R
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    Trike looks sweet! I would also second the idea of not running a locked rear axle unless you are only going to ride on loose surfaces. I was toying with the idea of isolating the rear wheels from each other and each having a freehub and getting rid of the jackshaft freehub. You would have two chains coming off the main drive axle that go back to each wheels freehub cog. This would be better than a rear diff because while pedaling you will always have power going to both wheels but when turning either wheel will be able to spin faster than the other when needed. it would not work going in reverse but bikes don't have reverse anyway.

    The tough thing with this idea though is finding an opposite direction freehub/freewheel because one will have to be in the opposite orientation of the other. Do any reverse direction freehubs exist?

  32. #32
    N8R
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    oops, I wrote all that above and then after posting read your last comment, so it looks like you already have that idea!

  33. #33
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    Here's what you need:

    Performance Products | Detroit Truetrac Differential

    ...only smaller and lighter. It's what I run in my 4X4 truck. :grin:
    Originally posted by bucksaw87
    I still fail to see how mustaches, fixies, and PBR are ironic.

  34. #34
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    Actually I was thinking of doing something like an EZ locker.

    Basically a couple of gears facing each other, each one bolted to one of the axle shafts. One of them could slide on the shaft just enough for the teeth to slip across the other gear. There would be a spring that pushes the 2 gears together (maybe like a valve spring from a car).

    When riding straight, the spring holds the 2 gears and both wheels are driven. The same would apply when braking. But when turing, especially with a load, the force of the wheels moving at different speeds would be enough to overcome the spring tension, and would let the gears slip.

  35. #35
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    double pedaler fat trike

    Quote Originally Posted by N8R View Post
    Yeah, that's a delta trike. This will be a cool build!
    I am working on a double pedaler fat trike
    Attached Thumbnails Attached Thumbnails Fat Trike Build-image.jpg  

    Fat Trike Build-image.jpg  


  36. #36
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    I made some new hubs. Now the shell is DOM tubing. I seriously doubt these will ever give me trouble!





    Not the prettiest welds, but they will work:


  37. #37
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    I had the first official test ride tonight. I have working rear gears and a working rear disc brake.

    I didn't want to spend too much money on this build, and I wanted to use as many parts on hand, so I ended up using a friction shifter going to a cheapie rear derailed. It has a 7 speed freewheel, but the rear frame assembly slightly blocks the high gear, so its a 6 speed. The rear brake is a Tecktro Hydraulic that I had laying around and the rotor is 203mm. It stops well enough to slide the fat tire, and this bike is just for cruising, so I doubt I'll put a front brake on it.

    The next step is to build the rear bench for the kids, figure out a locking diff, and give it a little paint. I may end up putting some sort of head and tail light on it too.

    Here are some pics:












  38. #38
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    This is a great thread.

    More like the fatbike threads of old where we were seeing loads of innovations, ingenuity and bodges.

    Keep it coming!
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  39. #39
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    It's really turning out awesome. Right on!

  40. #40
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    Check out the turning radius on this pig:


  41. #41
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    Turning radius= wheelbase. Dat handling... like it's on rails. This is The Next Big Thing.

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