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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 09:18 PM.
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  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.
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  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.
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  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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  7. #7
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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
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  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
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  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!
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  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!
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  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!
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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?
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  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.
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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

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  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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    70 is going to be pretty crappy, once sagged it's going to feel like you are way over the rear wheel.

    Go 73-74.

    Another great single pivot bike to copy geo from. I have the previous version of this, it's a touch steeping in the HA at 67 and I think the sta is 72.7.
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    Hi Adam

    Are you aware that you can use a Down-tube for the Seat stem from Nova Cycles that is 34.9mm, 15 degree bend. At your length of seat tube, you would have 0.6mm wall, so it needs a sleeve. Seat stem: using a dropper post @ 31.6mm, you will need a 1mm walled sleeve.

    NOV-CODT-B35-969

    This will allow you to attach to the BB shell and clear the tyre.

    Eric
    If I don't make an attempt, how will I know if it will work?

  28. #28
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    Quote Originally Posted by shirk View Post
    70 is going to be pretty crappy, once sagged it's going to feel like you are way over the rear wheel.

    Go 73-74.

    Another great single pivot bike to copy geo from. I have the previous version of this, it's a touch steeping in the HA at 67 and I think the sta is 72.7.
    Xprezo - Fabrication 100% canadienne
    Oh dang! that's why I need you guys. Yeah, I generally like a slack STA due to my ridiculously long femurs, but you're right about the sag, I think I'll steepen that up a tad.

    Quote Originally Posted by Eric Malcolm View Post
    Hi Adam

    Are you aware that you can use a Down-tube for the Seat stem from Nova Cycles that is 34.9mm, 15 degree bend. At your length of seat tube, you would have 0.6mm wall, so it needs a sleeve. Seat stem: using a dropper post @ 31.6mm, you will need a 1mm walled sleeve.

    NOV-CODT-B35-969

    Eric
    Eric,

    That's a great tip! Thanks.
    Although, what would I rather have... a sleeved seat tube, or a floating bottom bracket?
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  29. #29
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    Adam
    To clarify the sleeve, the 34.9 Tube needs an outer sleeve, used with a 1mm walled inner sleeve. The ideal seat stem size is 33.6mm.

    If it was my build, I would prefer a solid BB to a 'noodly' one. And I would be radical and do a steel inner sleeve machined with a shoulder to suit the seat stem and silver it in.

    Eric
    If I don't make an attempt, how will I know if it will work?

  30. #30
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    Yep, I hear ya Eric,
    I think I'm going to go that way. I just got a lathe, so I suppose it will be a fun job for that.

    While I'm posting here, I've looked all around for tech drawings of FOX forks and can't seem to find any. I just need that AC length for the 150mm Talus 34. Can't seem to find it...
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  31. #31
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    Should be about 540mm at 150mm of travel.

    The 160mm is 550mm.

    My old 150mm Talus 36 is listed at 545mm.

  32. #32
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    Are you planning on using a Front Derailleur? If so, check your clearance to the swingarm and think about how you plan on attaching it.
    -Aaron G.

    "Before D.W., "anti-squat" was referred to as pedal feedback."

  33. #33
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    Nope. Not a big fan of those, I'm gonna stick a Chain guide mount on there and run one of those, I don't think I'll need that much clearance for one.
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  34. #34
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    Sweet, Thanks Shirk!
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    I can roll a tube for you, I just have the harbor freight but with the swag offroad dies. Has to be non-heat treated, so a TT versus, or a nova like the ex butted 28.6 EXTERNAL BUTT SEAT TUBE 1.2/0.6/0.9 x 580 :: EXTERNAL BUTT SEAT TUBES :: ROUND TUBES :: MAIN TUBES :: TUBES STEEL :: Nova Cycles Supply Inc.
    cheers
    andy walker

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    Orange has a pretty good drawing of their frames on the website. I have not checked if it's to proper scale, but I assume it is.

    The Five is known to me a great riding bike. Some small tweaks to account for 650b and it's another great frame to model you bike after.

    I am working on modeling a bike after the Alpine 160.

    1 3/4 0.049 straight gauge for the downtube
    TT 34.9 seattube
    TT 44mm headtube

    Undecided on a .9/.6/.9 versus 34.9 toptube or 1 3/4 0.035 straight gauge

    Also still trying to figure out what gauge and diameter to use for the rear triangle.

    For the main pivot I plan to use a 31.8 headtube then use a 25.4 steer tube as the pivot axle. This way I can use two upper cups from a 1" headset as bearings. I learned this from digging in Walts blog.

    Just need to continue my braze practice and get a couple hardtails under my belt before going from concept/planning to reality.

  37. #37
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    Exactly. These days asking about where the front derailleur will mount on a mountain bike is like asking where the canti hanger will go. I have literally not sold a single mountain bike with a front derailleur in something like 10 months.

    -Walt
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  38. #38
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    Andy,

    That's super generous of you, thanks so much! I may have actually figured a way to go with a straight ST, which I will touch on later, but I may also take you up on that.

    And Shirk,
    Very cool. I'm planning on the two headset tops as well, I'm using a butted top tube and not really worried about it.

    My rear triangle is going to be 7/8" x .035" straight gauge for the upper part and 5/8" x .035 for the support, which kind of seems overbuilt to me, but I suppose we'll see.
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    650b full suspension-9256119629_43f230487d_z.jpgI have the 1 1/8 and 1 1/4" swag dies, may have to add the 1.375" anyway Here's 20mm on the ex butted nova ST.
    cheers
    andy walker

  40. #40
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    Well... Here's a change...

    I've changed my mind. I just finished building a frame for a buddy with 650b wheels, my first experience with them. At first I didn't have a wheel to stick in the frame, so I was using a 26er to check things out, but it seemed a little big. I measured it, and it was 27".

    I guess I new this already, but just hadn't really thought about it.

    So I've decided to build this thing as a 26er. It's going to make actually building it up soooooooooooooo much cheaper because I can buy stuff off of friends and I'm honestly starting to think that this 650b thing is pretty dumb (Start argument: take it to another thread if you want).

    This will also allow me to not bend any tubes, and if I build something super shitty, I'll have spent less money which is really great.

    Anyhow, I'm hoping to get the front triangle mitered tomorrow and then I'll start working on the pivot and maybe the rear triangle. Updates to come... some time.
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  41. #41
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    Well...

    Just because the rims don't measure what they are called - they rarely do by the way - you can't argue with the physical merits of the "27/29" inchers. You simply make your choices. Going with a more economically feasible build makes perfect sense from that standpoint, if that is an important consideration. Can't argue that, although the only thing really different is the wheels & tires. Probably, just getting started and figuring out full suspension in the easiest fashion makes the most sense. Save the fancy stuff for when you've got it all doped.

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  42. #42
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    Given the price (free, if you have as many bike dork friends as me) of 26" parts these days, and given that I happen to know the OP is a starving college student (who builds crazy awesome stuff and whose talent I am jealous of) I'd say 26" makes perfect sense.

    Honestly having ridden 26 vs 650 head to head I can't say I can tell much of a difference anyway.

    -Walt
    Waltworks Custom Bicycles
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  43. #43
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    Quote Originally Posted by shirk View Post

    I am working on modeling a bike after the Alpine 160.

    1 3/4 0.049 straight gauge for the downtube
    TT 34.9 seattube
    TT 44mm headtube

    Undecided on a .9/.6/.9 versus 34.9 toptube or 1 3/4 0.035 straight gauge

    Also still trying to figure out what gauge and diameter to use for the rear triangle.

    For the main pivot I plan to use a 31.8 headtube then use a 25.4 steer tube as the pivot axle. This way I can use two upper cups from a 1" headset as bearings. I learned this from digging in Walts blog.

    Just need to continue my braze practice and get a couple hardtails under my belt before going from concept/planning to reality.
    dude. you building bikes? tres awesome!

  44. #44
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    xy9ine, Thanks for pointing out so my brain could read the 2nd time, The 1" steerer tube with headsets for bearings. Aha, that's a great idea Walt used. Hmmm...
    cheers
    andy walker

  45. #45
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    Quote Originally Posted by xy9ine View Post
    dude. you building bikes? tres awesome!
    Currently teaching myself how to braze.

    Couple hardtails first them some sort of straight gauge fs beast (beast in over built weight, not some DH huck monster).


  46. #46
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    Wow, thanks for making my day Walt! Dang that's a nice thing to say haha.

    But yeah, I do happen to be in that starving college student position (or at least I will be after this bike) And I think I have enough biker friends to do it for realllly cheap in 26. So that's good.

    And I'm glad to hear a more trusted opinion on my observation of the 650 thing.

    Adam
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  47. #47
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    Front triangle

    Alright, well I finally have some progress to report, or at least I hope.
    I brazed up a front triangle, but I think I'm stuck here for a little bit. Here is where I'm at:



    Looking pretty good I suppose. My worry is here though. I was thinking of eventually using a King headset for my pivot, so I bought a couple super cheap ones with about the same stack height to start off with. After sticking them in the pivot with the tubes that I'm planning on using to clamp on the rear end, things are looking pretty wide - 4.5" or 115mm wide.



    I don't have my cranks in hand yet, so I'm not sure if I'm screwed, but what do you think? I measured some other cranks and I think I should be OK (doesn't mean I won't hit my heels on stuff) but it just doesn't feel right.
    Attached Thumbnails Attached Thumbnails 650b full suspension-20130723-160842.jpg  

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  48. #48
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    Re: chainline vs pivot.

    I measured my E-Thirteen triple and I would suggest that it is representative of cranksets in general, and at 115mm width, it looks like you could only use the outer chain ring only. That would not make for a tidy 1 x anything arrangement.

    Now that is all in place (welded), I presume that the pivot is press-fit 30mm for the head cups? You could in that case make an internal spacer and use sealed cartridge bearings 6903 series, 17 x 30 x 7mm - pressed in. Machine up for yourself a 17mm hollow pivot shaft and you will have the clearance needed.

    Something to consider.......not as good a bearing design, headset bearings would be better, but your options are limited.

    The build looks really good with plenty of bracing/surface area keeping the BB and pivot rigid.

    Eric
    If I don't make an attempt, how will I know if it will work?

  49. #49
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    Thanks Eric,

    Yeah I was thinking just pressing in bearings would be my other option. I think I'm going to go ahead and find a crappy, representative crank set at the bike co-op and check it out, I think I could be OK.

    In the mean time I'm going to go ahead and order my stuff. I picked up a fork and wheels today. Gettin' serious money wise about now, so I hope this works.
    -Adam Sklar
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  50. #50
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    Curious why you moved the pivot point vs the original drawing or bikes like Heckler/Orange.

    Can you go narrower on your collars that are going to clamp to the pivot shaft? Perhaps squish the ends of your swing arm tubes to gain clearance.

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