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  1. #1
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    Full suspension fatty design with Surly Nate sized tires ( more boredom )

    So, having still a bit of time I have been screwing around with geometries, tire clearances, shock travel - wheel travel ratios, chain line clearances and lastly O.D. Crank - swingarm bend clearances. This is not easy to design with so many variables !!!

    Specs:

    Steel tubing frame assemblies

    80mm front travel max
    135mm front hub, 82mm rim and Nate tire
    160mm rotor

    75mm rear travel max
    30mm shock arm travel
    2.5 : 1 ratio

    170mm hub, shimano 10 speed cassette, 11-36t
    82mm rim and Nate rear tire
    160mm rotor


    Full suspension fatty design with Surly Nate sized tires ( more boredom )-underside-swingarm-assembly-solid-modeling-mode.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-close-up-sliding-drop-outs-solid-modeling-mode.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-left-side-nates-layers-turned-.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-left-side-xray-w-o-tires.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-right-side-xray-w-o-tires.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-shock-mtd-xray.jpg
    roxo56
    Surly Troll 650b

  2. #2
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    Will the Tires have clearance when compressed?

  3. #3
    MaverickMotoMedia.com
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    you're gonna wanna put a linkage in there. Pedal bob is going to be terrible with that setup.
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  4. #4
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    not necessarily. Single pivot can work quite well without a linkage if done right. I recently had a Santa Cruz Superlight29 and was blown away by how well it pedaled for a "cheap" and "simple" bike. Not sure if it was because they've got all the geo and pivot loctions dialed perfect, or because shocks are better these days or what, but it worked.
    Bend, OR

  5. #5
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    Quote Originally Posted by Gigantic View Post
    you're gonna wanna put a linkage in there. Pedal bob is going to be terrible with that setup.
    How would the linkage reduce pedal bob?

  6. #6
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    That was the first thing I worked on...they fit with about 10mm clearance at full 75mm .
    travel

    Quote Originally Posted by liquidboarder2k4 View Post
    Will the Tires have clearance when compressed?
    roxo56
    Surly Troll 650b

  7. #7
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    I had a SC Butcher and consider the SC single pivots to be my ideal.
    I studied other systems too ( Yeti, Ventana, Niner, etc..) but the simplicity and weight savings of a single pivot system like the Heckler and Butcher was my logical selection.

    I'm lazy and don't like all of the extra linkage disassembly and regreasing involved with levered linkages. Plus, I have had this crazy idea after getting into this design that FS fatties of the future (and I think they will be hugely popular, forgive the pun)
    are going to probably be used for more radical terrain and will evolve into a much lighter and much more widely ranged machine than the current snowbike that gets used for trail "sometimes". The reason I'm thinking that is because I read constantly on this forum of many of you who now leave the FS skinny tired bikes at home and use the fatty for trail.

    Why have two bikes to take care of if one can reasonably do both ? Keyword there is reasonably !

    Anyways, I now have a good acad block library in 3d if anyone needs some for design. Just PM me...

    I'm working on a HT 190mm version and will try a 190mm Bud tired FS too now that I have a component library.

    Quote Originally Posted by TroyS600 View Post
    not necessarily. Single pivot can work quite well without a linkage if done right. I recently had a Santa Cruz Superlight29 and was blown away by how well it pedaled for a "cheap" and "simple" bike. Not sure if it was because they've got all the geo and pivot loctions dialed perfect, or because shocks are better these days or what, but it worked.
    roxo56
    Surly Troll 650b

  8. #8
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    Full suspension fatty design with Surly Nate sized tires ( more boredom )

    I think the linkage mention was meant as a Swing Link, to stiffen up the rear when it's actuated.

    I remember AMP bikes had a similar shock/strut interface early on that got complaints of being flexy. They added a swing link...flex problem solved.

  9. #9
    Sup
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    the pivot is too high
    the chain is going to pull the wheel down
    if you have any sag it will bob all the way down the trail
    the ideal single pivot location is at the top of the chain ring
    with more than one chainring it will always be a compromise
    look at all the trek's and cannondale's ignore all the fancy monkey motion links because they are all single pivot
    should get you in the right area

    good luck ....cool project
    I am slow therefore I am

  10. #10
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    Quote Originally Posted by Burnt-Orange View Post
    the pivot is too high
    the chain is going to pull the wheel down
    if you have any sag it will bob all the way down the trail
    the ideal single pivot location is at the top of the chain ring
    with more than one chainring it will always be a compromise
    look at all the trek's and cannondale's ignore all the fancy monkey motion links because they are all single pivot
    should get you in the right area

    good luck ....cool project
    Thanks for that critique. I will rework it to move pivot. Do you agree that a link pivot is a better system or will a SC single pivot concept work if I relocate pivot ?
    roxo56
    Surly Troll 650b

  11. #11
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    Unless you're Dave Weagle or Joe Graney, i would not try to invent anything suspension wise. I think your first idea of copying a santa cruz single pivot as closely as possible is the right idea. Trek and cannondale have other parts that are not present in your design. I believe that all they do is modify the linkage ratio as the swingarm moves through its travel, but i don't know enough about it to be certain there aren't other effects as well.

    If your design only has one part (like a Superlight) then use the superlight pivot location. If you have swing links and that other business, then use the pivot location of bikes like that.

    I think my Superlight had less pedal bob than a Fuel EX that i rode a couple years ago.

    All that said, i think Burnt Orange is right, if you compare your pivot location to that of the Superlight, you can see yours is much higher. The superlight pivot is about even with the big ring.

    Full suspension fatty design with Surly Nate sized tires ( more boredom )-santa-cruz-superlight-29-dxc.jpg
    Bend, OR

  12. #12
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    The new Heckler's pivot looks to be placed exactly the same also.

    I think it's great that you're working on this design. Have you built bikes before? Do you intend to actually build this?

    As mentioned by someone else, rear end flex is an issue with this type of design, but it's not horribly important i don't think, especially on a fat bike. Sure stiffer is better, but that adds cost and complexity. You have to choose your own compromise. Is the stiffer frame enough more FUN to justify the cost and complexity? Up to you.

    In any case, you'll want to use large bearings and a carefully designed interface for that pivot, to make it as stiff as possible. Santa cruz sells rebuild kits for their pivots, you could use their hardware and design your frame to suit.

    Full suspension fatty design with Surly Nate sized tires ( more boredom )-heckler_profile_blue.jpg
    Bend, OR

  13. #13
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    Full suspension fatty design with Surly Nate sized tires ( more boredom )-juneau3.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-juneau1.jpgFull suspension fatty design with Surly Nate sized tires ( more boredom )-juneau2.jpgTroy,
    I admire the Heckler too for it's simplicity and also realize that it probably enjoys greater stiffness due to it's aluminum frame. It should be possible to increase rear swingarm rigidity thru the use of thicker tubing selections or perhaps even the use of an aluminum swingarm. Does anyone know of a website where Heckler type suspension bearings are spec'd ? Or any larger bearings that could be used are spec'd ?

    In the meantime, I've reworked the main pivot fulcrum to just above the larger chainring. Also, I've reworked the CS and SS curves so that a Surly Lou will easily fit and added upper and lower stay braces that will allow full suspension travel. Might add a DT mtd rubber bumper to maintain/limit max swingarm travel ?
    roxo56
    Surly Troll 650b

  14. #14
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    Looking good. I've found that the closer you can get the pivot to the bottom bracket , the less you'll have to worry about chain growth through travel. Not sure if you intend to run a FD, but your pivot location may interfere with an FD if that's your intent. Personally, I'd just run XX0 or XX1 and eliminate the FD. Also, may want to consider putting the kink in the seat tube a little lower. You'll have to tweak the front triangle a bit to maintain your geometry, but having that much seat tube sticking out seems like it would be kind of limiting for different riding styles.

    As for the Heckler bearings, they sell bearing/linkage kits through the SC website. Information is probably pretty limited, but you could always just order a set to base your design around.

  15. #15
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    I really like this design.Why not just build a wide swingarm for a superlight or do you plan to produce frames?

  16. #16
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    Most linkage designs are no better than a single pivot design. The wheel arc is the same.
    If you're interested, read Ken Kasaki's dissertation on it here:

    Index

    In it he shows that the ideal pivot point is between the bottom bracket axle and the chain line, i.e. the vertical chainline. Meaning, a pivot point somewhere around the top of the granny ring or middle ring. Given that it's a fat bike, and you may spend more time in the granny gear, that points towards a lower pivot point, maybe 30 to 50 mm above the bottom bracket center. (Chainrings have a radius about 2 X # of teeth +3, so 24 tooth ring is 51mm radius). Within this range, it probably doesn't matter much, but it will be much better than a pivot point at the top of the big ring. Well, better, maybe not much better.

    If you look at the top Specialized, Cannondale, and Trek bikes, after all these years, they all have basically a mono pivot design with the pivot somewhere around what I just said.

    If you're really interested in the suspension design, download the software "Linkage" and play around with it.

  17. #17
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    You'll also want to think about heel clearance with the shape of your chainstays.

  18. #18
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    A wider swingarm on a superlight would only address tire clearance thru the swingarm. It would not solve chainline-BB issues that "Lou" brings with him ?
    roxo56
    Surly Troll 650b

  19. #19
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    I will study that dissertation. Thanks for that link and your summary of pivot locations based upon his remarks.
    You make an excellent point by noting that much time will be spent in granny gear up front. That would likely be because this FS fatty will be at least 40 lbs ?

    In fact, I have pondered going 1x10 (half granny) with an OD crankset to aid with chain tire clearance. Not that that is currently an issue. Does anyone know offhand what is the smallest tooth count cog possible (outboard) on the Moonlander crank ? 28 teeth would be perfect if it fits.




    Quote Originally Posted by Godlikedog View Post
    Most linkage designs are no better than a single pivot design. The wheel arc is the same.
    If you're interested, read Ken Kasaki's dissertation on it here:

    Index

    In it he shows that the ideal pivot point is between the bottom bracket axle and the chain line, i.e. the vertical chainline. Meaning, a pivot point somewhere around the top of the granny ring or middle ring. Given that it's a fat bike, and you may spend more time in the granny gear, that points towards a lower pivot point, maybe 30 to 50 mm above the bottom bracket center. (Chainrings have a radius about 2 X # of teeth +3, so 24 tooth ring is 51mm radius). Within this range, it probably doesn't matter much, but it will be much better than a pivot point at the top of the big ring. Well, better, maybe not much better.

    If you look at the top Specialized, Cannondale, and Trek bikes, after all these years, they all have basically a mono pivot design with the pivot somewhere around what I just said.

    If you're really interested in the suspension design, download the software "Linkage" and play around with it.
    roxo56
    Surly Troll 650b

  20. #20
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    This was easy and I now have over 3k miles of road, off road and up north down hill riding on it and it's still riding just like the day I built it.

    Another Full Suspension Phatty

  21. #21
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    Quote Originally Posted by Look Out Below View Post
    This was easy and I now have over 3k miles of road, off road and up north down hill riding on it and it's still riding just like the day I built it.

    Another Full Suspension Phatty
    That looks good and not overly difficult to mod.As mendon posted lenz is looking to build a fatty fs and i see the risse racing lassen is gonna be an option also.

    Roxo,i apologize for the thread derail.

  22. #22
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    Quote Originally Posted by roxo56 View Post

    In fact, I have pondered going 1x10 (half granny) with an OD crankset to aid with chain tire clearance. Not that that is currently an issue. Does anyone know offhand what is the smallest tooth count cog possible (outboard) on the Moonlander crank ? 28 teeth would be perfect if it fits.
    It looks like FSA makes a 29 tooth 94mm BCD ring, and surly makes a spider for the Mr Whirly cranks that would make that work.

  23. #23
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    no prob. nice conversion. tire size ? how'd you fix bb ?
    roxo56
    Surly Troll 650b

  24. #24
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    Sold my 2-stroke dirtbike today to make room in my garage for a new fatbike. I'm getting close to having this design ready to turn over to a custom frame builder and need a recommendation. Many seem to be so busy they don't bother to return emails. I'm not looking for the absolute best welder. Just someone who can build my design and check me for missing items like cable guides, brake post locations, water bottle cage mts, etc...

    Thanks to those who have suggested geometry mods and suspension advice.

    Steel frame
    1x10 drive train
    Bud/Lou tires
    29 tooth FSA ring
    13-36 cassette
    100mm BB
    MWOD crank w/ spider ring
    XT brakes
    3" rear travel (with 4" possible later)
    190mm rear hub, 135mm front
    203mm rear rotor, 180 front
    80mm front suspension suspension corrected
    neutral single pivot link (cnc'd)
    flanged & inset ball bearings (Lily)
    8-10mm hardware at pivot links
    6.5" x 1.5" Fox CTD shock

    Check it out:











    roxo56
    Surly Troll 650b

  25. #25
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    Try Lenz or Ventana. Looks good.
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