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Thread: Round MTB Stays

  1. #26
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    Why crimp both stays? Why not just crimp the drive side stay and only in the area where the chain ring(s) need to pass and/or cut and weld a tube or plate to create a small recess in the critical area of the drive side stay.

    Also, are you guys using True Temper 22.2mm round stays or just generic 4130 tubing? (Henry James as Versus tubing in 22.2mm size so it seems this is an option). If you are using generic 4130 tubing where are you ordering it from?
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  2. #27
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    The crimp is for the crank arm not the chainrings. I used 7/8" x .035" 4130.
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  3. #28
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    Unless I am not understanding.... I see no reason to crimp for the end of the crank arm. It seems you could avoid the inference by simply bending to clear the crank arm.

    In any case 7/8 inches is about 22mm and it gets me thinking....

    I am planning to try to make a set of 22mm round stays for my next 29er. What I am planning now is to make a "S" bend stay. Up front on the drive side the inference is from my 36 tooth ring at around 55mm to the right of BB centerline. I figure that I need 3mm of clearance between the ring and the chainstay. At most the outer edge of the chainstay can be 52mm from center line if I don't crimp. With 22mm wide stays this means that my maximal tire clearance becomes (52 - 22) * 2 to give me a total of 60mm of tire clearance. If I reduce the width of the drive side stay to 15mm in just the critical area I obtain 74mm of clearance between the stays in the area of the chain ring. The non drive side stay can simply be pushed outward. Since the tire will be a little back from the area where the chain ring is I imagine that I can obtain clearance for some pretty wide rubber with full 22mm diameter on the non drive side.

    Right now I am thinking about doing no crimping on the non-drive side and then on the drive side simply cutting a section of the chainstay out and welding in a small plate to stiffen and strengthen the stay. In effect it would be similar to a yoke style design but only on the drive side so it should be lighter then a traditional yoke style and stronger then crimping the stays. My plan is to use "S" style bending to avoid heel and crank arm inference problems.

    Any thoughts and has anyone done anything similar?
    Last edited by febikes; 01-03-2013 at 07:59 PM.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  4. #29
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    When I did this I wasn't bending my own stays so that's what I had to work with.
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  5. #30
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    Ummm...

    SEVEN eighths (.875) is 22.225mm.

    Anyway, I don't know much, only two frames in and only one style (Fat), but I've had ZERO problems getting the room I needed for a 4" tire with .750 round stays, a 100mm BB, and 2 (granny/middle) rings. I guess I'd like to see a drawing, since I'm totally visual. If you could not make the room otherwise, a very strategic sectioning and plating of a round stay might not lose you much if any strength, while giving you the clearance you need. Pick the right compromise and it should work fine, and look neat too. My gut says making a relief for the ring(s) is the way to go, but that is a flier off the top.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  6. #31
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    Quote Originally Posted by TrailMaker View Post
    SEVEN eighths (.875) is 22.225mm.
    I much prefer the metric system because it's easier to work with vs. all the fractions that people use with inches.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  7. #32
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    Quote Originally Posted by TrailMaker View Post
    a very strategic sectioning and plating of a round stay might not lose you much if any strength, while giving you the clearance you need. Pick the right compromise and it should work fine, and look neat too. My gut says making a relief for the ring(s) is the way to go, but that is a flier off the top.
    A common strategy to gain room with tight tolerances, especially belt drive applications.

    Here is a blog post that details some of the process...

    Groovy Cycleworks 330-988-0537: Martin's build...day 3 through ???

    and a pic of the finished plated stay.

    cheers,

    rody
    Attached Thumbnails Attached Thumbnails Round MTB Stays-martins-ti-081.jpg  

    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  8. #33
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    Thanks Rody as always I love your work!

    I am also excited about the potential in the technique.

    The following is a quick drawing I did to sketch out the idea.
    Attached Thumbnails Attached Thumbnails Round MTB Stays-chainstays.jpg  

    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  9. #34
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    Bending on chainstays, radius and start points?

    Another drawing of the idea.

    I am trying to decide what CLR to get for the bending die.

    Right now I am thinking about using 7" (aka 177.8mm).

    What do you guys think the ideal CLR is for this sort of thing?
    Attached Thumbnails Attached Thumbnails Round MTB Stays-chainstays.png  

    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  10. #35
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    Quote Originally Posted by febikes View Post
    Another drawing of the idea.

    I am trying to decide what CLR to get for the bending die.

    Right now I am thinking about using 7" (aka 177.8mm).

    What do you guys think the ideal CLR is for this sort of thing?
    Mark,

    According to your drawing, you have the 177.8 CLR dimension you are trying to achieve in the wrong spot. The CLR is the center line of the tube bend, not the inside diameter of the bend, which is where your dimension leader is pointing. To achieve the bend that you show, you'd need a die that is 177.8 + 1/2 the diameter of the tube (11.1mm) = 188.9mm CLR die. So maybe a 7 1/2" would put you pretty close to where you want to be?

  11. #36
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    Quote Originally Posted by stuntnuts View Post
    Mark,

    According to your drawing, you have the 177.8 CLR dimension you are trying to achieve in the wrong spot. The CLR is the center line of the tube bend, not the inside diameter of the bend, which is where your dimension leader is pointing. To achieve the bend that you show, you'd need a die that is 177.8 + 1/2 the diameter of the tube (11.1mm) = 188.9mm CLR die. So maybe a 7 1/2" would put you pretty close to where you want to be?
    Huge thanks!

    I will update the drawing.

    I have been trying to design around using the largest practical CLR to minimize the bending drama and avoid issues with the thin wall 4130. As you know the dies are expensive and the largest die my new Pro Tools 105 bender will take is 7". I think I can make the clearances work with a 7" radius.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  12. #37
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    I'm successfully bending .75" diameter, .035" and .049" wall 4130 on a 5.5" CLR bender with excellent results. No sand packing, no ice, nothing. Although you are bending .875" diameter, which is a bit bigger than my .75" diameter tubes, I wouldn't fear CLR's smaller than 7" if you think it will help with clearance.

  13. #38
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    As I have mentioned many times, I am bending .750 x .035 CroMo on a 3.5" CLR Pro Tools 105 with no extra effort needed. EASY! I don't see why .875 wouldn't bend as well. I'm not sure why you feel the need to use a 7" CLR, but that is certainly a choice that needs to be made. I can see it for esthetics in some instances, as the bends tend to be a little tight to the eye in certain areas, but it seems the tighter radius allows getting through tight areas a little easier.

    I took your specs from your first crude drawing and laid out a rear end. .875 tube bent on a 3.5CLR. I radiused the tire and allowed a fairly generous 10mm tire-to-stay clearance. I brought in an Origin8 crankset from my Fatbike layouts for reference. As you can see, you will have ring interference and I also modeled in a 6" disc rotor that will need clearance as well. Obviously, you don't have any crank issues at all, just rings and disc. From this super quick mashup with very little fiddling done, it looks very feasible to me.
    Attached Thumbnails Attached Thumbnails Round MTB Stays-febikes.jpg  

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  14. #39
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    Design update

    I updated my design.


    Still using 7" bends and including some 60mm straight sections to help transition the "S" bends.

    I have not yet used a bender so at this point I don't have any idea of the capacity for the PRO-TOOLS 105 bender but after speaking with them it sounds like the design is doable.

    What do you guys think? Is this something that can be made using a rotary draw bender and a 7 inch die? Is a tool like the PRO TOOLS 105 up to the job?
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  15. #40
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    Hey;

    1) The key to bending thin wall on a tight CLR is the anti spring back assembly included with the smaller CLR dies. Maybe all the small tube dies come with this feature, but I don't know for sure. I know that the large tube sets do not, as they don't need it. Maybe you don't need it for large CLR small tube sets either? My guess is that it is mandatory for ANY small tube bending, regardless of CLR.

    2) You will not be able to put bends in a tube back-to-back-to-back like that. There has to be a fairly substantial distance between them to accommodate the distance from the bend to the end of the follow shoe. It needs a certain distance of straight tube past the bend to draw against. In other words, you can't draw a bend through the follow shoe. In that configuration, you'd have to draw one bend, and likely press the next, and in some sort of very short press die.

    3) The 7" CLR die gives you those big looping bends and wastes a lot of crank clearance. I could maybe see doing the rear bend with a 7, but beyond the nice look of gradual bends (subjective), they are not very practical when space is tight. Isn't it always?
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  16. #41
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    IMO that amount of chainstay cutout is pretty excessive. Remember that the stay is only as strong/stiff as it's weakest/flexiest point. Not much point in using 7/8" or whatever if you're basically ending up with only 1/4" or whatever at the cutout point.

    An arbor-press type bender may work better for what you're going for as TM said, too.

    -Walt
    Waltworks Custom Bicycles
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  17. #42
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    Thanks guys, it is great to hear your thoughts.

    I am nervous about using smaller CLR but it is good to know that others have achieved good results. The guys at PRO-TOOLS tell me they think 7" dies are the way to go. It is likely that they are conservative and want to avoid the pushing the bender too far beyond the specifications for minimal wall thickness. They also tell me that I can "S" bends provided I have 3" of transition so I will be reworking the CAD a little because the current drawing is 60mm transitions. If needed I will go down to a smaller CLR, They are going to make custom dies so I want to make sure my CAD work is conservative. I don't really want to push the envelope for the bending performance.

    For the cut out I plan to have a fairly beefy plate in there but again I am nervous. With a thick enough plate the flex should not be an issue. It looks like Lynskey uses the plate style with a beefy plate and from what I have seen it works well. I will be doing some testing to determine the plate thickness that is needed with 4130.

    I will also likely reduce the cutout as per Walt's comment. It is a balance point because I want to be comfortable with 2.3" tires. I don't really need to run anything wider then that.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  18. #43
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    Does anyone have recommendations for thickness for plate style in 4130?

    I am thinking about going full plate on the drive side similar to the following.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  19. #44
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    Plates are heavy and flexy - there's a reason tubes are the structure of choice for bike frames. If you do want to go that route, I've mostly seen ~1/4"-3/8" range. But it might be time to just use an oval stay, IMO.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  20. #45
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    REALLY, REALLY, REALLY...................

    I'll stress it again. THE BENDING IS A NON ISSUE! I felt the same way as you before I did it. I never thought it would work, and it ends up being stoopid simple. Nearly foolproof. I could take a stick of tube and my drawing above, toss it in my PT105, and have you a pair of perfect stays in a half hour. The only difficulties are getting the bends in plane with each other (the same with any bending project), and possibly not getting the bends the perfect distance apart on the first one. Many times the first one is a prototype because you simply can't calculate the real actions/reactions/positions of the materials and components on paper. Then sometimes, you actually nail it the first time!

    I cannot guarantee that .875 will act the same as .750 because I have not bent it. It is possible that the larger tube would not bend on a 3.5" CLR like the .750 will. However, based on the ease with which I can bend what I am, it is my guess that .875 would bend just fine on a 3.5CLR. I'm not sure why they are insisting on a 7"CLR? All I can tell you is what I am having complete success with. You should shoot for the tightest CLR that you can, in my opinion, and I am quite convinced that it is far tighter than 7". Do note that they say that the thinnest .750 tube you can bend on a 3.5CLR is .058"! I'm doing .035 EASILY!

    As for the clearance relief for rings and such, I see that as a non issue in this case. I don't think anyone would go so far as to take half the diameter of the tube away to get the clearance needed, and we are not talking very much of a relief at all in reality. Yet, while there are obvious negatives to crimping stays, people mash the crap out of them all the time, to far greater detriment to the structural integrity of the tube than we are talking here. I'd be very surprised if a cut of even 1/4 the tube diameter were necessary. It would likely be half that, or less. I further don't see the need to use material much heavier than the tube itself to make the plate. It is the tube's shape that gives it the majority of its resistance to bending, not its thickness. With a minimal reduction in diameter, the tube should retain a very significant amount of its original integrity, and the plate thickness should not be an issue. I'd use whatever I had around. 16-18g should be fine.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  21. #46
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    If you're going to do a cutout, I think doing a cut with a hole saw, then welding in a matching diameter piece of tubing looks pretty good. The straight cut/flat plate IMO looks ugly.

    Then again, this is coming from the person with perhaps the worst taste on earth, so you should probably ignore me.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  22. #47
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    Thanks guys, I am going to rework the cad with some tighter CLR and see if it helps. I agree that big plates look ugly and have been thinking about the hole saw approach. I want the design to be strong, stiff, and also look good.

    When I revise the drawing, I will ensure that the minimum tube cross section will be 14 mm behind the cut out. I plan to make the minimum chain stay length 425mm. With paragon sliders it should be possible to slide the wheel rearward when running wide tires and bring it forward when smaller tires are mounted.
    Mark Farnsworth, Raleigh, NC
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  23. #48
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    Quote Originally Posted by Walt View Post
    , this is coming from the person with perhaps the worst taste on earth, so you should probably ignore me.

    -Walt
    Mark,

    Listen to Walt, he does have the worst taste on earth

    A few quick points...

    - for your proposed build, I've not seen any convincing rationale why you want to use 7/8" stays on a steel 29er. You are making the fabrication design layout and ultimate fitment more complex than it needs to be. 3/4" round is plenty strong for your application, allows for greater clearances, and will fit your anticipated sliders with less manipulation at the dropout stay joint.

    - Forget a simple vertical scallop cut for your ring clearance, it does not provide enough of a forward clearance for variation in ring sizes. Creating a plate insert with an inline holesaw cut as demonstrated in the blog post above creates a longer surface area in line with the stay for versatility (smaller rings, belt drive chainwheels) and is near invisible once built up.

    - hydraulic press benders are where it is at for close proximity bends. You guys are killing me with all the draw bender manipulation. Invest the time to build the correct tool and then benefit from it's ability and time saving effort for a lifetime.

    Then again, my perspective is as lame as Walts...do what makes you smile!

    rody
    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  24. #49
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    Quote Originally Posted by Walt View Post
    Then again, this is coming from the person with perhaps the worst taste on earth, so you should probably ignore me.
    Awwww...

    Say it aint so, Walt?!



    OK Farnsworth, time to jump out of the box. Come up with something slick. I was going to use the CS below as a way to maximize heel clearance while stepping out around my rotor, until the thought of using the low mount Paragon DOs flashed into my brain and I had my final - and widely acclaimed - CS epiphany for my Kroozer. I'm still not sure I could bring myself to use it on an MTB that will get pounded on, but it would sure look fargin kool.

    -
    Attached Thumbnails Attached Thumbnails Round MTB Stays-kroozercs1.jpg  

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  25. #50
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    Quote Originally Posted by Rody View Post
    - for your proposed build, I've not seen any convincing rationale why you want to use 7/8" stays on a steel 29er. You are making the fabrication design layout and ultimate fitment more complex than it needs to be. 3/4" round is plenty strong for your application, allows for greater clearances, and will fit your anticipated sliders with less manipulation at the dropout stay joint.
    Thanks! I was/am concerned about the stiffness of 3/4" chainstays but if you think they will work can you expand on your thinking? Earlier in this thread Golem Builder asked this question without any response. I started my design work around 7/8" stays because I found several examples online and they seem like a super stiff option. DFL also had a thread a while ago about them and I have seen others come up from time to time around 7/8" stays. I also see lots of these 7/8" stays on titanium bikes so I know the tire clearance can be solved.

    As a single speed, I want the stays on the bike to be crazy stiff because I am often mashing a big gear out of the saddle and a stiff drive train feels better then one where the bike springs as you try to mash into the pedals. I am not a huge guy but I like the idea of the frame being stiff. For my next personal bike I was thinking around pushing the chain line out to around 58mm and gaining a little more space that way as well.

    I don't mind the stiffness of the normal oval stays but wanted to break out of the mold a bit and try to increase stiffness and also like the idea of designing my own curves for the stays rather then using the off the self options.

    Do you think round 3/4" with .034 wall would be more or less stiff then standard oval stays? It would be easier to fit the 3/4" stays but when I look around I seem to see more examples of people using 7/8" stays.

    Quote Originally Posted by Rody View Post
    - Forget a simple vertical scallop cut for your ring clearance, it does not provide enough of a forward clearance for variation in ring sizes. Creating a plate insert with an inline holesaw cut as demonstrated in the blog post above creates a longer surface area in line with the stay for versatility (smaller rings, belt drive chainwheels) and is near invisible once built up.
    Yes, that will be the plan as well.

    Quote Originally Posted by Rody View Post
    - hydraulic press benders are where it is at for close proximity bends. You guys are killing me with all the draw bender manipulation. Invest the time to build the correct tool and then benefit from it's ability and time saving effort for a lifetime.
    I will have to think about this one a bit more,
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

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