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  1. #1
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    650b full suspension (Not 650b full suspension)

    Hah! You thought I'd already made one. Sorry.

    Now that I have your attention though, who's done it? Or put in some research into it?
    I'm looking for a real challenge of a summer project (yeah, I'm starting to plan it already), and I've really been wanting a FS bike for a while. 650b seems like the way to go. I would hope in the 4-6" of travel range.

    Could a Ventana rear end be used? How do I get one of those? gut another bike? go from scratch? How the hell does that FS thing work anyway?

    Any thoughts would be super appreciated. Thanks!
    Last edited by adarn; 07-31-2013 at 08:18 PM.

  2. #2
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    An ambitious project;

    As far as the rear triangle is concerned, I'd be very surprised if you couldn't simply call Ventana and order one. I'd be further surprised if you couldn't get at least a few small morsels of advice there as well. As I've heard, the owner is pretty legendary for being a right-there-and-ready kind of guy.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  3. #3
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    Pretty sure Ventana does not sell direct to amateur builders. Need to prove insurance. Walt might chime in as I think I got that from something he has posted.

    Go single pivot and fab everything yourself.

  4. #4
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    Ventana only sells to insured "professional" builders. That said, you can score broken/used/old Ventana frames all over the place and pull off the rear end.

    I've written about how to build with these rear ends pretty extensively on the blog if you do some searching around. They offer a lot of flexibility in an off-the-shelf product, so you get a lot given that you don't have to fab much up yourself. That said, you can do it all yourself (especially single pivot bikes) in a variety of ways and that may be more fun if you're building for yourself and don't mind some experimenting.

    -Walt

    Quote Originally Posted by shirk View Post
    Pretty sure Ventana does not sell direct to amateur builders. Need to prove insurance. Walt might chime in as I think I got that from something he has posted.

    Go single pivot and fab everything yourself.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  5. #5
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    Build your own rear triangle in steel, that's the fun part of the project, just finished a 29er fs all steel and it works well, you can do it, keep us posted.

  6. #6
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    Walt, I've seen your blog posts and they're definitely a good resource.

    I'll definitely be doing a lot of research on the front end here.

    Syltmunk, got any pics?

    Adam

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    Worthless!

    ...without pictures, that is! Share the wealth, man!

    -Walt

    Quote Originally Posted by Syltmunk View Post
    Build your own rear triangle in steel, that's the fun part of the project, just finished a 29er fs all steel and it works well, you can do it, keep us posted.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  8. #8
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    Quote Originally Posted by adarn View Post
    Walt, I've seen your blog posts and they're definitely a good resource.

    I'll definitely be doing a lot of research on the front end here.

    Syltmunk, got any pics?

    Adam
    Here are some pics of my all steel 29er, have about 200 miles since finished, no issues so far works great.
    Attached Thumbnails Attached Thumbnails 650b full suspension-dscn0951.jpg  

    650b full suspension-dscn0953.jpg  

    650b full suspension-dscn0956.jpg  

    650b full suspension-dscn0955.jpg  

    650b full suspension-dscn0954.jpg  


  9. #9
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    OK, so I'm finally starting to dive into this project, and I have a lot to learn...
    To be honest, I know almost nothing about suspension, so I'm hoping to maybe get some tips from you guys.

    Here is what I am thinking at this point:

    I drew up this sketch in sketchup mostly to get the idea across of what I'm thinking and hopefully get some feedback
    650b full suspension-fs-drawing001.jpg

    So for gemoetry I'm thinking:
    STA: 70
    HTA 69
    ST C-T: 450mm
    ETT: 635mm
    CS: 420mm
    HT: 120mm
    BB drop: -10mm unsagged

    I was thinking of 6" of travel, but I'm still on the fence about having that much.

    I was planning on using a 1" headset for the pivot, 7/8" x .035 straight gauge for the bent section of the rear triangle and 5/8" x .035 for the straight support.

    I think that my main concerns with doing the rear triangle this way are 1. actually bending the tubes, and 2. having to attach the shock to the rear triangle at the bend, would that be an issue?

    I plan on using mostly TT bmx tubes on the front triangle. 34.5mm ST so I can run a 31.6 dropper post and a 44mm HT. I will probably drill a hole right through the DT for the pivot, and possibly sleeve it too, or something else to reinforce it.

    The next thing I need to figure out, and really need help with is pivot placement. Any tips on that? (sorry, I know what kind of question that is).

    Oh, also, the whole thing is gonna be fillet brazed, which I find kind of funny, but it's what I've got!

    Anyhow, I'm excited to get working on this and even more excited to ride it!

    Thanks,
    Adam

  10. #10
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    Suspension design

    Adam,
    I've done a fair bit of scouting around on this very subject and these are the two best resources I've found. The Linkage bike suspension design software is unbelievably good particularly for the price. They have a demo model so you can get an idea of what you are getting before you buy.
    Linkage Bike Simulation Software - News

    If you combine that with reading all of the Joe's Corner blogs on the Santa Cruz site (many times) you may begin to understand what all of the graphs mean and what you are shooting for in your design. I think this is a cool thing that Santa Cruz did because most companies aren't that forthcoming. There was a blurb like this on the Yeti site once but they pulled it down. Start with this one:
    Santa Cruz Bicycles COMPANY

    The guy that is the head designer for Banshee Bikes has his masters thesis posted on-line. He used the Linkage software to design their latest downhill bike...and got a masters degree for it. I don't remember the link for that but I bet you could find it.

    It also helps to have one of the world's most experienced bike suspension designers living in your town, Doug Bradburry, that you can corner and force to divulge all of his worldly knowledge.
    There is nothing more difficult to plan or more dangerous to manage than the establishment of a new order of things.

  11. #11
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    Thanks Sick Sticks,

    I just read all of those articles on the Santa Cruz site and it's certainly some good info, it'll take some time to soak in.

    I'll have to look around for that thesis too, that could be neat.

    Thanks!

  12. #12
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    Quote Originally Posted by adarn View Post
    OK, so I'm finally starting to dive into this project, and I have a lot to learn...
    To be honest, I know almost nothing about suspension, so I'm hoping to maybe get some tips from you guys.
    Copy a Santa Cruz Heckler.

    Dig into Walt's blog, he has some info deep in there about his single pivot and what he would do different and what he learned.

  13. #13
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    JMc003 Photo Album - Pinkbike

    There is a massively long Pinkbike thread that sometimes has some useful into. You have to weed out the drawings of never to be built huck machines with 76 inches of travel and made with steel girders but some good pops in like above.


  14. #14
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    Quote Originally Posted by shirk View Post
    You have to weed out the drawings of never to be built huck machines with 76 inches of travel and made with steel girders but some good pops in like above.
    That's the best use of a Prophet swing arm I've seen in ages.

  15. #15
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    Sweet! Thanks for the info guys!

  16. #16
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    Adam,

    Your drawing looks a lot like a design I've been kicking around for awhile now. Crazy. I think we've both been looking at the Heckler a bunch. One thing I like about the heckler design is the simplicity and it would be easy to get the clearances around the rear wheel with shortish chainstays.

    An interesting example of a steel full sussy is the Cotic Rocket. the Product of COTIC cycles : droplink ROCKET You might also be interested in Cy's take on their droplink design What is the "droplink" suspension platform? From the bike geek corner of COTIC cycles and why they went with steel Why use steel to make a full-suspension bike?

    With the single pivot designs brake jack can be an issue depending on how you roll. I've noticed this as a rider but it was never horrible to me and I felt the design worked better in other areas compared to a typical 4-bar design or SC's VPP. Granted my background is in moto before bikes where brake jack is huge. I have not ridden a split pivot or Trek's ABP (another split pivot design), both look very smart to me. This old thread has some good nuggets on brake jack that initially helped me understand more what was happening. "Brake jack" - an explanation.

    I've also seen some people do some crazy kinematics analysis using solidworks if that's something you have access to.

    Hope that helps! I think there needs to be more full sussys in steel!

  17. #17
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    FWIW;

    I've owned a Heckler since 2005. I don't ride it anymore since the Niner and now the Fatbikes, but it was and is a great bike. I put a lot of rough wet miles on that thing, and it still gets the job done just fine. It's hard for me to think back now and realize I used to ride such a "small" bike as that (even though it's an XL), given the modern bikes that actually fit me, but it is a great machine. Still has the original bearings in the swing arm even. Bought a set of Enduros but never needed them!

    Not one single complaint about the performance of the bike, other than not really fitting the size of it. It is a great platform to use for a model. They are not legendary for nothing!
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  18. #18
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    Those single pivot bikes really only have one thing going for them - ease of construction. To get them to ride acceptably both up and down, you will need a highly tunable shock or the ability to revavle your own shock. You have some slight shock rate tuning options based on where you mount the fixed end of the shock relative to the arc or the moving end, but this affords only a very minor change in end or beginning rate. Design around either a cane creek double barrel (fairly adjustable, but potentially not adjustable enough) or perhaps an RS Monarch where you have the full service manuals, valving options and air can choices to dial the suspension in.

    A single pivot also puts all of the stress on the one pivot. The downtube needs to be massive to counteract the forces. This is achievable in alu with oversized and non-round section tubing, but in steel can you get suitable tubing that won't make the bike too heavy? Any flex in that pivot will result in rapid wear of the shock bushings and compromised performance of the shock. Any angular irregularities in shock activation will result in lots of stiction.

    I'm just wondering if a single pivot design is a good choice for a steel front triangle?

  19. #19
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    Yes

    Having built lots of steel FS bikes, I can say that it works just fine for both front and rear triangles.

    Single pivots ride great with basically any modern shock (I have been on professional podiums on them in the recent past) and they are light, stiff, have great reliability and require very little maintenance. They are killer when done well and that's why they are still used and probably always will be.

    Moreover, the OP is doing a first suspension bike so even if you disagree with al of that its still the best option just for ease of design/construction.

    Walt

    Quote Originally Posted by TigWorld View Post
    Those single pivot bikes really only have one thing going for them - ease of construction. To get them to ride acceptably both up and down, you will need a highly tunable shock or the ability to revavle your own shock. You have some slight shock rate tuning options based on where you mount the fixed end of the shock relative to the arc or the moving end, but this affords only a very minor change in end or beginning rate. Design around either a cane creek double barrel (fairly adjustable, but potentially not adjustable enough) or perhaps an RS Monarch where you have the full service manuals, valving options and air can choices to dial the suspension in.

    A single pivot also puts all of the stress on the one pivot. The downtube needs to be massive to counteract the forces. This is achievable in alu with oversized and non-round section tubing, but in steel can you get suitable tubing that won't make the bike too heavy? Any flex in that pivot will result in rapid wear of the shock bushings and compromised performance of the shock. Any angular irregularities in shock activation will result in lots of stiction.

    I'm just wondering if a single pivot design is a good choice for a steel front triangle?
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  20. #20
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    Hey thanks guys, In response to all of that...

    Yep, I'm pretty much going to copy the heckler straight up with a few adjustments to fit me better.

    As Walt said, this is my first time building a FS bike, and it's really an experiment. I'd love to have a fun bike to ride, and I'm confident that I will, but I'm sure it will have some things that I can learn from.

    I'm using steel because it's all I have the tools for and because its cheap and easy to work with.

    As far as brake jack, pedal bob and those things, I would definitely be interested in learning how to minimize those things (the SantaCruz articles had some good info on that), but I understand that I'm building a single pivot bike and it won't ride like a hardtail.

    I'm working on some more final drawings now and my tubes are on the way. This is going to be sort of a side project, but I think I should be getting into it soon here.

  21. #21
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    Don't worry about brake jack, or get lost in the fact that there is no linkage mumbo jumbo.

    I currently ride a single pivot and it shreds.

    A good fork and tires will mean more on the trail then as long as the shock tune is't way off, the good thing is it's easy to get the shock info for a Heckler.

  22. #22
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    Sounds awesome Adam! When I get a design flushed out of my single pivot I'll be sure to post it up here for fun. Just checked out your site... are you in Boulder? We should ride sometime.

  23. #23
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    Nice, I'll look forward to seeing it. I am in Boulder for the summer... always happy to ride.

    As for the bike, I went ahead and bought that linkage simulation software and I've been having some fun messing around with it. What I've found though is I'm going to have to figure something out to get my seat tube to clear the tire. I don't have access to a tube bender, so I guess my best option is to just stick the ST onto the DT like this program conveniently lets me do.

    I've also settled for a measly 140mm of travel. I was going to go for 150, but without bending the ST it seems like that would be a major pain. Also I don't need 150.

    With it set up this way I only get 21mm of chain growth, which doesn't seem terrible, the leverage ratio gets up to 2.76, which I understand to be not terrible.

    Anyway, I'm going to spend some time thinking this through more, but I'd kind of like to try building something soon and just seeing how it goes. Tubes are in the mail, so I suppose that's going to happen soon.

    650b full suspension-ful-sus.jpg

    -Adam

  24. #24
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    What is the deal with the 68 degree sta?

  25. #25
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    Quote Originally Posted by shirk View Post
    What is the deal with the 68 degree sta?
    That was to compensate for moving the ST so far up the DT, effectively it should be 70.

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