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  1. #1
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    Steel FS Linkage designs

    So I've gotten a wild hair and have started researching steel full suspension builds with the intent of building a frame for myself.

    Taking a look at companies like Cotic, Privee, as well as some of the custom builds on this forum, I see single pivot designs. I want to know why. Are there any examples of steel DW/VPP/ABP link bikes? Maybe it's just for the sake of simplicity?

    My workhorse trail bike is an Ibis Ripmo, and I quite like the ride characteristics. Would there be any pitfalls in trying to replicate that in a steel build?

    I'll be digging through the forums to see if I can answer my own question, but if anybody would be willing to help it'd be much appreciated.

    Cheers

    - Mutt

  2. #2
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    2 reasons for single pivots:

    1: It's easy to design/build with fully custom geometry without screwing up the kinematics.
    2: In the era of single chainrings the benefits of more complex suspension designs are negligible. That's why a lot of large manufacturers like Trek (ABP is just a fancy name for a single pivot design) have returned to single pivots/fauxbars.

    If you just want to build something complex because you think it'll be fun, by all means do it. It'll be much harder and IMO you won't really benefit in terms of the function/ride of the bike, but it's about what makes you happy, not anyone else.

    -Walt

  3. #3
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    That makes a lot of sense. It also aligns with the aesthetic desires I have for a steel framed bike.

    I think I'll start with trying a single pivot for the sake of simplicity, and try to avoid setting myself up for failure given my lack of experience.

    Walt, would you mind explaining why single chain-rings have lessened the return on complex suspension? I don't totally follow how the two are connected.

  4. #4
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    Ok so for the sake of my own understanding I'm going to try and write it out here. Anybody feel free to correct or shame me for the bits that be wrong.

    With the goal of limiting pedal bob manufacturers take into account chain-line in relation to pivot point on a full suspension bike, using that chain tension to restrict suspension travel. With older bikes, tradition dictated multiple chain-rings front and rear (booo) to get friendly climbing gear ratios. Small front, large rear would change the chain-line enough that complex suspension designs were made up to create a shifting virtual pivot point (!??!).

    With modern bikes we have single front chain-rings and dinner plates on the rear to get the friendly climbing gear ratio. Chain-line defaults to a constant around that front pivot point, allowing for less variables when designing a frame?

    I suppose I'm getting hung up on how to limit pedal bob with a single pivot design. Then again maybe pedal bob isn't actually that big of a problem, especially given how common climbing switches are on shocks?!

  5. #5
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    Quote Originally Posted by canadianjerkey View Post
    Ok so for the sake of my own understanding I'm going to try and write it out here. Anybody feel free to correct or shame me for the bits that be wrong.

    With the goal of limiting pedal bob manufacturers take into account chain-line in relation to pivot point on a full suspension bike, using that chain tension to restrict suspension travel. With older bikes, tradition dictated multiple chain-rings front and rear (booo) to get friendly climbing gear ratios. Small front, large rear would change the chain-line enough that complex suspension designs were made up to create a shifting virtual pivot point (!??!).

    With modern bikes we have single front chain-rings and dinner plates on the rear to get the friendly climbing gear ratio. Chain-line defaults to a constant around that front pivot point, allowing for less variables when designing a frame?

    I suppose I'm getting hung up on how to limit pedal bob with a single pivot design. Then again maybe pedal bob isn't actually that big of a problem, especially given how common climbing switches are on shocks?!
    You have it pretty much right. Keep in mind that there's also a lot of marketing BS involved - there are plenty of suspension designs that have no advantages at all, but the companies involved need to make "new" stuff and market it.

    Of course some designs do have at least small advantages (generally wheel path) to compensate for the increased complexity. But there's plenty of meaningless "innovation" too.

    Download a copy of linkage and you can play around with different designs and see what happens.

    If you don't want to do that, to eliminate squat (pedal bob) just line the main pivot up with the top of the chainring. That will pretty much get you to 100-110% antisquat and you're basically good.

    -Walt

  6. #6
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    Walt pretty much summed up every reason I went with this design: https://www.flickr.com/photos/clockw...57691970402140
    NOTHING WORKS LIKE CLOCKWORK

    www.clockworkbikes.com

  7. #7
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    Quote Originally Posted by Walt View Post
    2 reasons for single pivots:

    1: It's easy to design/build with fully custom geometry without screwing up the kinematics.
    2: In the era of single chainrings the benefits of more complex suspension designs are negligible. That's why a lot of large manufacturers like Trek (ABP is just a fancy name for a single pivot design) have returned to single pivots/fauxbars.

    If you just want to build something complex because you think it'll be fun, by all means do it. It'll be much harder and IMO you won't really benefit in terms of the function/ride of the bike, but it's about what makes you happy, not anyone else.

    -Walt
    Trek has been on the single-pivot deal since they left URT Y-bike behind. And really, it is more Horst link designs that are being returned to than single pivots, IMO. The Horst link and VPP patents availiable for use without licensing, it is going to be interesting to see who else besides Diamondback tries out the counter rotating links of the VPP.

    But I agree that very good bike can be made using a single pivot. I'm on one now. The silly oval ring feels much worse for my pedal stroke than the simple suspension.

  8. #8
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    Quote Originally Posted by Clockwork Bikes View Post
    Walt pretty much summed up every reason I went with this design: https://www.flickr.com/photos/clockw...57691970402140
    That frame looks rad, great shape on the rear triangle.

    Now that it's been established that single pivot makes the most sense from a practical perspective, does anybody have any examples of steel frames that went more complex anyway?

    I wonder if there would be any potential issues getting linkages to be stiff enough, or other production issues.

  9. #9
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    My original bike was classic single pivot.



    My second fs I have added a shock linkage to drive the shock but the rear triangle is still a single pivot.



    The links to drive the shock don't need to be anything crazy as the main pivot is doing the bulk of the work in stiffness.

    My first set of rocker plates driving the shock I made some errors and they broke so I quickly knocked some out with the steel I had on hand, in the pic above it's before I trimmed them down some.

    This basic layout of a single pivot frame with a linkage actuated shock has been used in many many many different configurations, it's basically what Evil does currently. Short links attached to the rear triangle that are pushing or pulling the rocker that drives the shock.

    I moved to a linkage as I didn't love the linear nature of a single pivot. It's difficult to get much progression in the LR on a classic single pivot so you need to rely on the shock tune to get ramp-up at the bottom of the stroke and you're need to give up suppleness in the early stroke to get it.

    If you don't have the Linkage program yet you should buy a copy and mess around in it looking at bikes you've ridden and like.

  10. #10
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    Collection of photos on the 2nd build in here.

    https://www.pinkbike.com/u/shirk-007/album/NPC144/

    First build here.

    https://www.pinkbike.com/u/shirk-007...hy-Bike-Build/

    The second frame I broke it in the Whistler Bike Park on closing weekend.

    https://www.instagram.com/p/BopKqZzl...ken-by=earle.b

    Long story short I had screwed up when I built it and didn't properly braze on the rocker link mounts and had blown them off and damaged the seattube in a deep bottom out. Frame broke where the seattube was heavily dented. I should have gusseted the dent when it happened.

    The next version I am working on.

    https://www.instagram.com/p/BopKqZzl...ken-by=earle.b

    https://www.pinkbike.com/u/shirk-007/album/LL150/

    Basically a copy of what Ancillotti is doing with their pull link design.

  11. #11
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    Quote Originally Posted by shirk View Post
    ...I moved to a linkage as I didn't love the linear nature of a single pivot. It's difficult to get much progression in the LR on a classic single pivot so you need to rely on the shock tune to get ramp-up at the bottom of the stroke and you're need to give up suppleness in the early stroke to get it.

    If you don't have the Linkage program yet you should buy a copy and mess around in it looking at bikes you've ridden and like.
    Thanks for this advice, I'll definitely look at some linkage driven stuff. I'll also see about purchasing the linkage program once I'm off work this evening.

    I'd like to be able to run a coil shock so progression will definitely come into play. From previous experience riding an Ibis HD3 and bottoming out hard on larger features I know what I don't like!

  12. #12
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    As far as programs go, bikechecker.com and linkage are a must, but is anybody using any other programs for look development and design? I have a good deal of experience with 3D programs for animation and design (C4D, Houdini), but not much with engineering in mind.

    Maybe it just comes down to what I'm comfortable with as long as I can measure angles and lengths!

  13. #13
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    I work out the suspension in Linkage, then make my own model in Fusion360. Fusion has a free license for home / small business use.

    Being able to pull up three bikes at once in Linkage is nice. I can have two variations of my build open then the bike I want to benchmark against.

  14. #14
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    Quote Originally Posted by shirk View Post
    The next version I am working on.

    https://www.instagram.com/p/BopKqZzl...ken-by=earle.b

    https://www.pinkbike.com/u/shirk-007/album/LL150/

    Basically a copy of what Ancillotti is doing with their pull link design.
    Heyyyyy! Nice work. I have some unfortunate circumstances going for my next personal frame that involves a severe lack of physical space available (the frame is going to look a little bit like a motorcycle because there's going to be alien objects crammed into the front triangle), and I was thinking, for a single pivot, could I locate the rear shock very low using a series of intimately placed, small, inverted levers? It is nice to see the question answered with prior art packaged in a much more practical example.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

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    Yes that layout I am using on the next frame creates a big ol open front triangle. A bike packers dream, or someone that loves big water bottles. Fun that I neither bikepack nor usually rely on bottles for my water. But I just couldn't shake the look of the Sunn/RTS/Ancillotti outta my head and just had to build a bike with the shock tucked down in at the bb.

  16. #16
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    I actually had a framebuilding student once who is an ultra-geek mechanical engineer who talked me into letting him build a tweaked Evil - lots of weird little levers all mounted down low. It actually worked out really well and he's still enjoying the bike 2 years later - but man was it a PITA.

    Anyway, I digress. The nice thing is that Evil sells *all* of the small parts (rockers, pivots, etc) and you can get all that stuff off the shelf if you want to do something similar:
    https://www.evil-bikes.com/collections/parts-kits

    -Walt

  17. #17
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    I should have mentioned: if you want to do the Evil style setup, you'll need at least one and maybe 2 small radius bends in the downtube to fit everything in. Like I said, PITA!

    -Walt

  18. #18
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    Quote Originally Posted by canadianjerkey View Post
    That frame looks rad, great shape on the rear triangle.

    Now that it's been established that single pivot makes the most sense from a practical perspective, does anybody have any examples of steel frames that went more complex anyway?
    My buddy adds floating brake and idlers to his 1-pivots to further isolate the suspension from pedaling/braking forces (and cuz he likes to run SS if he wants to).

    Steel FS Linkage designs-wht.jpg
    Steel FS Linkage designs-green.jpg
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  19. #19
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    Quote Originally Posted by Walt View Post
    I should have mentioned: if you want to do the Evil style setup, you'll need at least one and maybe 2 small radius bends in the downtube to fit everything in. Like I said, PITA!

    -Walt
    I'm definitely leaning towards the evil style setup right now, great that they sell all the small parts, though I might try and build it all myself anyway.

    As far as small bends go, I'm hoping I can enlist my Dad into helping out. He has a good deal more experience with metalworking than myself (also the space and the tools). Maybe I'll even convince him to switch over from his carbon bike. Hah.

    We'll have to see how well his sculptural metalwork translates to frames!

    https://jnicktaylor.com/wp-content/u...2_IMG_8853.jpgSteel FS Linkage designs-01-big-boy-taylor_nick_42_img_8853.jpg

  20. #20
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    Quote Originally Posted by slapheadmofo View Post
    My buddy adds floating brake and idlers to his 1-pivots to further isolate the suspension from pedaling/braking forces (and cuz he likes to run SS if he wants to).
    Aw man, that's a whole new can of worms with idlers! I have seen more and more of them though... Does Linkage support idlers? I bought the personal license but haven't gotten home to install it yet.

  21. #21
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    Yes Linkage supports idlers.

    Bending tubes for bikes is something unique to bikes. Not many metal workers have experience bending the thin wall tubing. Or I might be wrong and your dad has a fully kitted Di-Arco bender on hand.

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    Quote Originally Posted by shirk View Post
    Yes Linkage supports idlers.

    Bending tubes for bikes is something unique to bikes. Not many metal workers have experience bending the thin wall tubing. Or I might be wrong and your dad has a fully kitted Di-Arco bender on hand.
    Can't say for sure! I'll have to scout around next time I go out to the coast for a visit. There will likely be quite a few differences between the tools he has for his sculpture and what's required to build a more complex frame.

    Any advice for bending tubes if it comes to that?

    At least my wife will be pleased I'm not trying to age aluminum in the oven.

    Thanks to all again for pitching in with this thread!

  23. #23
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    Honestly, back up several steps and build yourself a town bike or at most a hardtail. You'll learn stuff that will make the FS project actually doable without endless frustration. Then revisit.

    -Walt

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    Quote Originally Posted by Walt View Post
    Honestly, back up several steps and build yourself a town bike or at most a hardtail. You'll learn stuff that will make the FS project actually doable without endless frustration. Then revisit.

    -Walt
    Totally fair, and as of around 3pm today my adjusted plan. I have an old Trek Ticket Stub dirt jumper that I really dislike, on account of longer chainstays and a repair weld that might not hold. Building a replacement frame seems ideal, and it'll give me a good opportunity to test/learn to trust my own welds.

    That all said, I'm enjoying the FS chat and posted examples. I'll still be planning out the FS build!

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