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  1. #1
    Belltown Brazer
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    Trying some stuff

    Riding this one raw, and splitting the riding with my buddy/test pilot. Leaving it raw for a little while to make sure the seat stays hold up. First couple of rides feel good. This one uses a 73 BB shell with the drive side set at 68mm BB distance to give me an extra 5 mm on the nds. Don't think I need to do that in the future. 72 STA, 69.5 HTA, 425 chainstays, 655 FC. Made for a 120 stem. Feels short and quick. Cheers! B
    Attached Thumbnails Attached Thumbnails Trying some stuff-pa140806.jpg  

    Trying some stuff-pa250936.jpg  

    Trying some stuff-pa250939.jpg  

    Trying some stuff-pa250940.jpg  

    Trying some stuff-pa250942.jpg  

    I am Belltown Bikes LLC. Steel bicycles hand made in East Hampton, CT

  2. #2
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    Cool! Love to see people thinking about chainstays/front center/wheelbase as part of the steering equation instead of just head tube angle.

    What is the goal with the NDS chainstay? Tiny seastays (are those 1/2"?)

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

  3. #3
    Belltown Brazer
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    Quote Originally Posted by Walt View Post
    What is the goal with the NDS chainstay? Tiny seastays (are those 1/2"?)

    -Walt
    Hey Walt, the goal with the nds chainstay is lateral stiffness. In my mind, the flex we're worried about in the rear triangle has a large "X" component. If you go with the "vertically compliant, laterally stiff" goal then you should use round chainstays. The oval ones are stiff in all the wrong directions - and weak in all the wrong directions too. I also believe that the seat stays all but eliminate any "vertical compliance" - unless they are *really* curved, or are attached to a spring of some sort...the truss structure of the rear triangle eliminates vertical movement...ATMO.

    Anyway, I'd love to use round chainstays on both sides, but as you know short chainstay 29ers require some compromises. The oval on the ds is the compromise in this case.

    Those seat stays are 0.375". I've made a few bikes with them and they work fine...well, fine enough for us "continual prototype" fellas (no failures yet). If the food on my table depended on the frames I probably wouldn't go smaller than 0.5". I am concerned about the reliability of the small stays where they curve sharply to the seat tube...hence the weird "bridge".

    B
    I am Belltown Bikes LLC. Steel bicycles hand made in East Hampton, CT

  4. #4
    RCP Fabrication
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    Cool bike!

  5. #5
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    Nice! I like the creative thinking on the chainstays. Something I pondered about too with the current tubes out there being ovalized for tire clearance which is nice but yeah, no vertical compliance.
    So my question to you since you have a nice new test bike...do you notice any difference in how it rides (softer?) compared to a frame with two oval chainstays?

  6. #6
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    In my opinion...

    ...vertical compliance on hardtails is nonexistent pretty much no matter what. Lower tire pressure, padded saddles, and setback posts made of stuff that flexes all can actually make a difference (Velonews did a pretty awesome article where they actually tested seatposts for flex a while back), but I must have significant time on at least 3 dozen hardtails of all designs and materials and... I could never tell a difference.

    I've built bikes for myself with all kinds of random shapes and types (and lengths) of chainstays and seatstays and once again, can't tell a difference in flex/compliance.

    YMMV, of course. But I stopped trying to make hardtails compliant by messing around with the stays a long time ago. There's a laundry list of stuff (tire clearance, heel clearance, beefiness, manipulation/dimping friendliness, dent and chainsuck hardiness, etc) that I care about more when selecting a stay.

    -Walt

    Quote Originally Posted by MDEnvEngr View Post
    Hey Walt, the goal with the nds chainstay is lateral stiffness. In my mind, the flex we're worried about in the rear triangle has a large "X" component. If you go with the "vertically compliant, laterally stiff" goal then you should use round chainstays. The oval ones are stiff in all the wrong directions - and weak in all the wrong directions too. I also believe that the seat stays all but eliminate any "vertical compliance" - unless they are *really* curved, or are attached to a spring of some sort...the truss structure of the rear triangle eliminates vertical movement...ATMO.

    Anyway, I'd love to use round chainstays on both sides, but as you know short chainstay 29ers require some compromises. The oval on the ds is the compromise in this case.

    Those seat stays are 0.375". I've made a few bikes with them and they work fine...well, fine enough for us "continual prototype" fellas (no failures yet). If the food on my table depended on the frames I probably wouldn't go smaller than 0.5". I am concerned about the reliability of the small stays where they curve sharply to the seat tube...hence the weird "bridge".

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

  7. #7
    Single Speed Junkie
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    I like it, looks like a good design.

    Meriwether, I had a frame using Ti tubing that was ovalized on both CS for clearance. Hod one good ride on it when both ovalized stays cracked top and bottom. If one can manipulate the tubing without causing stress risers then it should hold up I'd think.

  8. #8
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    Since nobody has said anything about it yet; that cutout seat lug/sleeve is really cool.

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

  9. #9
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    Quote Originally Posted by Walt View Post
    Since nobody has said anything about it yet; that cutout seat lug/sleeve is really cool.

    -Walt
    I second that, nice detail, balance and cool factor.

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

  10. #10
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    Quote Originally Posted by Walt View Post
    ...vertical compliance on hardtails is nonexistent pretty much no matter what. Lower tire pressure, padded saddles, and setback posts made of stuff that flexes all can actually make a difference (Velonews did a pretty awesome article where they actually tested seatposts for flex a while back), but I must have significant time on at least 3 dozen hardtails of all designs and materials and... I could never tell a difference.

    I've built bikes for myself with all kinds of random shapes and types (and lengths) of chainstays and seatstays and once again, can't tell a difference in flex/compliance.

    YMMV, of course. But I stopped trying to make hardtails compliant by messing around with the stays a long time ago. There's a laundry list of stuff (tire clearance, heel clearance, beefiness, manipulation/dimping friendliness, dent and chainsuck hardiness, etc) that I care about more when selecting a stay.

    -Walt
    I agree, the biggest things that help are a Ti seat post, Ti-railed saddle or a Brooks saddle (try it for awhile), and tire pressure. Big wheels too. Or rear suspension obviously.
    I had a YBB and THAT was awesome for vertical compliance but ...duh...no brainer. The stays cracked at the weld after 2 years too from all the flexing.

    I don't have as many bikes to go off, but I'm riding a frame with 14mm convex seatstays and...no difference. I thought maybe round chainstays may help but most round stays need to be hugely crimped/ovalized anyways to get tire clearance.

  11. #11
    Belltown Brazer
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    We're all on the same page IRT vertical flex...only exists in the minds of big company marketing spinmasters. I do belive that there is plenty of sideways flex in the rear end though. When you're standing and working hard and the bike is rocking the rear end is flexing. Now, the wheels and the tires flex more, but there is still flex there.

    The nds round stay is intended to gain back some of the stiffness in the sideways direction that is given up by using (and then dimpling) the oval cs on the ds. I think that using a through axle rear end would also go a long way to eliminating this flex. I also think ROR cs's are no better than full ovals.

    My thinking on the skinny seat stays is to just make them as big as they need to be and no bigger. I tried them on the last frame for me, and could not tell the dirrerence between them and something larger.

    I only have 3 *really* leafy rides on the frame so far. But it feels good. Between the 4" of leaves on the trails and my legs coming off of a week at Disney World, it is hard to tell anything other than it goes good...it is comfortable...no wackiness. I'll hand it off to my buddy after the hurricane (well,after we repair the trails after the hurricane) and get his impression.

    My marketing guy says this assymetric CS design increases lateral siffness 30% while increasing vertical compliance 20%!! ;-)

    I'll get back to battening the hatches now. B
    I am Belltown Bikes LLC. Steel bicycles hand made in East Hampton, CT

  12. #12
    Belltown Brazer
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    Quote Originally Posted by Walt View Post
    Since nobody has said anything about it yet; that cutout seat lug/sleeve is really cool.

    -Walt
    Thanks Walt, here is another one I did like that on my daughter's bike:
    Attached Thumbnails Attached Thumbnails Trying some stuff-pa060797.jpg  

    I am Belltown Bikes LLC. Steel bicycles hand made in East Hampton, CT

  13. #13
    Nemophilist
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    Lordy!

    Looks like it would snap in half. If not the stays, then the seat post. Or, I'd have the rear tire ground into the ST in a few peddle strokes! I don't suppose it was designed for Clydes, though.

    Interesting concepts. Another escapee from the box!
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  14. #14
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    Now those are some sweet statistics! All you have to do is say it on the interwebs and it's true, you know.

    I see where you're coming from with the lateral stiffness and agree. I was shocked at my Fatbike's un-stiffness laterally with oval stays and an overbuilt wishbone seatstay setup. Maybe you remember my stellar Youtube video? It was quite exciting. Granted, there is something wrong with that frame since it's not half that bad on my non-fatbikes with the same stays.

    I think it's interesting how you (as in framebuilders) can use small diameter seat stays with steel frames and at least in the short term, have no issues with too much flex or rear triangle weakness. Maybe if they're straight gauge and not 0.6mm wall it helps. What have others found with this?

    stay safe out there on the east coast!

  15. #15
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    TM, Seat Post?

    Quote Originally Posted by TrailMaker View Post
    Lordy!

    Looks like it would snap in half. If not the stays, then the seat post. Or, I'd have the rear tire ground into the ST in a few peddle strokes! I don't suppose it was designed for Clydes, though.

    Interesting concepts. Another escapee from the box!
    Hey TM, you had a bad Seat Post Experience?
    Alternatives seem to scare you.
    How's that Amish Farmbike going?

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

  16. #16
    Nemophilist
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    Well;

    I have not broken a seatpost on a modern MTB. I do not want to, thank you. Anything hugely unsupported like that gives me the willies. Granted, I weigh 240lbs; well outside the norm. However, thoughts of things coming adrift under my butt, particularly since I am sitting on it much of the time, are not something I want to contemplate. I broke a few as a kid, and I can tell you it is a sudden and very hard fall. I do not bounce so well as that these days!

    The Humvee is mowing it down very nicely, thank you. Fun machine! It will have a stylish "little" brother soon.

    We now return to our regular programming.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  17. #17
    Belltown Brazer
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    I've broken 2 Moots Ti seatposts and a homemade Carbon seat post thing in the past 6 years or so. Not too dramatic of an event really. Handlebar breaking much more exciting. I have yet to break one of my homemade Ti-Joe Ti seatposts...aside from having the head come loose when I was trying different adhesives.

    But I'm only 180# or so, not 240!! B
    I am Belltown Bikes LLC. Steel bicycles hand made in East Hampton, CT

  18. #18
    will rant for food
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    I've thought about your approach a bit off and on.

    Basically we're talking about a leaf spring vs a truss. How much do you want of which one, etc.

    I thought it might be neat to make a frame that looks a lot like a Jones space frame, but with a bottom bracket concentric pivot and a little dog bone link near the seat stay / top tube.

    Have some ridiculously overbuilt chain stay acting as a swing arm, and an almost direct seatstay to headtube setup kind of you like have going on here, coupled with a normal top tube doing what a top tube normally does... put a through axle rear hub into the whole picture.

    The application would be 1" (or something) travel for bike packing in places where you really, really don't want to have to deal with broken suspension components.

    Anyway. Cool bike!!
    Latitude: 44.93 N

  19. #19
    mcd
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    i'd like to throw my .02 in on this. first, i hope all ya'll guys are ok after Sandy blasted through...

    unbeknowst to MDENVENGR i acquired one of his frames and the fork it was designed around this spring from a 3rd party. It has the super thin seat stays a super thin top tube, beefy downtube and ovalized chainstays. also, curved seat tube, super short chainstays and a long head tube and non suspension corrected geo... i've been riding it a few times a week since june.

    i had been riding a SIR 9 for 6yrs prior to this. the geo is insanely awesome. it just works for me.

    as to the riding characteristics...i ride it ss with a magic gear. my first magic gear i was using an old cog from a broken up 9speed cluster and whenever i came out of a hard corner the rear stays would flex enough to throw the chain off. i don't feel like there is any more or less vertical flex than the niner. i did finally get a ss specific chain and rear cog and haven't thrown the chain anymore.

    i agree that it would be very interesting to ride a bike with rounded chainstays and see if i could feel the difference. on my ss i am always standing and mashing down while pulling the bike back and forth which i really had to pay attention to while using the narrow cog with no tensioner. interestingly, i did ride it as a 1x9 for a couple of days last month and had no issues and couldn't tell if there was any side to side flex at all, so if i was going to use it geared i'd go with the frame as is because i like the idea of a little flex(softness)

    anyway, sorry for the long ramble. here are some pics! yay for pics!
    Attached Thumbnails Attached Thumbnails Trying some stuff-belltown-bb.jpg  

    Trying some stuff-belltown-frame.jpg  

    Trying some stuff-belltown-seat-tube.jpg  

    Trying some stuff-belltown-seatstay.jpg  

    disclaimer: i (NO LONGER) live with my mom...

  20. #20
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    That is a sweet bike that MCD has!

    We road the Pisgah Double Dare together and had a blast. I enjoyed the chance to see a Belltown up close and was really impressed with the bike. The fillet brazed construction looks great. I very much like the way the seat stays are the bikes are done.

    Great looking bikes!
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  21. #21
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    So is the 120 stem to get a shorter front center? For the sake of a compact wheel base? Weight distribution?

    I have long arms so 120 +/- stems are the norm for me, but outside the racing scene 120 seems to have slid off the stem length range trend.

  22. #22
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    Independent vs dependent

    Stem length is thought of as an independent variable (ie "I need to pick a frame size where I run an 80mm stem") rather than what it should be, which is a dependent variable ("Now that I have the front center, BB height, saddle height/setback and wheelbase that I want, I'll pick a stem to put my hands where they need to go")

    Using the stem as an independent variable made decent sense in the days of 71/73 geometry on 99% of all mountain bikes but it has really broken down now that frame geometry is all over the place and mountain bikes are built for widely varying types of riding. People commonly end up on bikes that are WAY too long for them because they want to run a 70mm stem (or whatever) and to make matters worse long stems are now thought of as "XC" or "racer" items.

    Stems are just a way to get your bars where you need them. Nothing more - I wish more people understood this so I wouldn't have to explain it repeatedly to customers.

    -Walt


    Quote Originally Posted by dr.welby View Post
    So is the 120 stem to get a shorter front center? For the sake of a compact wheel base? Weight distribution?

    I have long arms so 120 +/- stems are the norm for me, but outside the racing scene 120 seems to have slid off the stem length range trend.
    Waltworks Custom Bicycles
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    waltworks.blogspot.com

  23. #23
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    Quote Originally Posted by Walt View Post
    People commonly end up on bikes that are WAY too long for them because they want to run a 70mm stem (or whatever)
    Yeah, I built my second frame like that (short chainstays = GOOD!, short stem = GOOD!), it sucked, I went back to long stems.

  24. #24
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    Quote Originally Posted by Walt View Post
    Stem length is thought of as an independent variable (ie "I need to pick a frame size where I run an 80mm stem") rather than what it should be, which is a dependent variable ("Now that I have the front center, BB height, saddle height/setback and wheelbase that I want, I'll pick a stem to put my hands where they need to go")

    Using the stem as an independent variable made decent sense in the days of 71/73 geometry on 99% of all mountain bikes but it has really broken down now that frame geometry is all over the place and mountain bikes are built for widely varying types of riding. People commonly end up on bikes that are WAY too long for them because they want to run a 70mm stem (or whatever) and to make matters worse long stems are now thought of as "XC" or "racer" items.

    Stems are just a way to get your bars where you need them. Nothing more - I wish more people understood this so I wouldn't have to explain it repeatedly to customers.

    -Walt
    For me the stem length and front center are connected.

    I know where I want my hands in relation to the front axle, and the front center I like.

    Set those points (and saddle position) after locating the BB and all the other specs are what they need to be to connect the dots (very simplified explanation).

    This usually results in a shorter TT and long stem than the current fashion and puts more weight on the front.
    mtbtires.com
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  25. #25
    Belltown Brazer
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    Quote Originally Posted by dr.welby View Post
    So is the 120 stem to get a shorter front center? For the sake of a compact wheel base? Weight distribution?

    I have long arms so 120 +/- stems are the norm for me, but outside the racing scene 120 seems to have slid off the stem length range trend.
    DR: Walt put together a great explanation. My take is this: When I first started riding 29ers I noticed that I had to really weight the inside handlebar entering the corners to get the bike to turn like I wanted. When I started designing/building my own I would figure about 100mm stem. That worked pretty well. More recently, as I've farted around with FC and HTA and chainstay length (my current thinking is towards longer - 425 effective -chainstays), a tad longer stem keeps my hands where I like them and keeps the FC in check.

    Even with the long stem, it does not feel like you're hanging off of the front of this one. The 68.5 HTA and the 100mm fork help that.

    Cheers! B

    PS: that red bike was a very early frame...number 8 or 9. I was suprised that it ended up in the Carolinas. The fellow I sold it to as a used demo flipped it pretty quickly. I'm happy to see it is still holding up. I replaced the chainstays on that frame once - thereby learning not to dimple them vertically. I must say my design thinking has changed since then. For me that bike was super comfortable, and went around corners better than anything before or since. But, ultimately I found it to be slow...the slack STA was the culprit for me. I felt like it took (relatively) a lot of energy to stand up - like I had to "pull" myself into a standing position, instead of just straightening my legs to stand up. Not a biggie maybe, but around here one will stand/sit about a million times per mile.
    I am Belltown Bikes LLC. Steel bicycles hand made in East Hampton, CT

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