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Thread: e-Fat

  1. #1
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    e-Fat

    I've learned a hell of a lot from this forum and the great people that post their builds and knowledge, but I've never shared any of the bikes I've been making.

    Seeing that it's winter and there have been a few others share their recent fatbike builds I thought it about time to share a frame and fork I recently made. The bike turned out well but for one issue that someone will likely easily point out(other than elevated chainstay bikes are an acquired taste looks-wise). I'd love to hear thoughts on how to improve this design, have at it!

    This is my second e-stay fatbike, 4th fatbike. It was built to fit Bud and Lou tires on 100mm wide rims. I was recommended the geometry by MikeSee and he built the wheels for the bike too, Rootbeer colored Clown Shoes, Borealis 190 rear hub, Fatback 135 front hub.

    e-Fat-efat-littlebald_trail.jpg

    I feel that elevated chainstay bikes have potential to ease some of the issues found with normal fatbike rear triangles, especially when trying to accommodate 4.7" tires, get sufficient crank and chainring clearance from the chainstay and tire, as well as offer room for shorter chainstays withOUT any severe dimpling or big bending. Chainsuck is moot with a 1x setup. Inspiration of the design comes a bit from 3D Racing's Chris Herting.

    e-Fat-tire-clearance-rear.jpg

    The two cables are internal to the top tube (31.8 x 9/6/9 Verus), the downtube is a 38mm Supertherm with the longer butt at the BB end so that the chainstays meet the downtube in the 1mm wall section rather than the thinner butt. With this size frame there was about 100mm of butt at the headtube still (see photo for sharpie marks).

    e-Fat-fronttriangle_mitered.jpg

    The chainstays are 3/4 x 0.035 bent on an Anvil 9" radius bender. The wishbone seatstays are all descending sizes of 0.035" 4130 too starting at 1" for the main stay, then 3/4, then 5/8 to the legs. Rear dropouts are PMW's.

    This frame's geometry is:
    - 68 deg HTA
    - 72 effective STA
    - 430mm chainstays (16.7" effective)
    - 12.6" BB height.

    Fork was made with the True Temper FB4 blades, and the crown pieces are 1" x 0.058", PMW 2017 dropouts.
    - 450 atc,
    - 50mm offset which makes for an even 100mm of trail.

    The weight of the frame? Don't know. I forgot to weight it. It's heavy, at least 5lbs. Total bike weight with the custom rear rack is 36lbs.
    e-Fat-testing_clearance-crank-front.jpg
    the crank checker device I coped from Joel of Clockwork. Works wonders!
    e-Fat-mill-platform.jpg
    e-Fat-hole-platform.jpg
    e-Fat-platform-loaded-mitered.jpg
    e-Fat-platform-welded.jpg
    e-Fat-frame-andfork-rear.jpg
    e-Fat-clearance.jpg
    e-Fat-ski-setup-shop.jpg

    I blabbed on and put more pics on my blog here if you're interested

  2. #2
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    Great! I love it! I have never been much of a fan of elevated stays, but this just makes sense. A clever way of solving a typical fat bike clearance problem.

    Had a look at the blog pics, and really admire no.11's forked Seatpost-BB connection; any reason that wasn't replicated here? Ease of construction? Stiffness?

    The UK isn't really the place for fat bikes at the moment, maybe if they had enormous inflatable tyres (BBC News - UK floods: River levels rise as rain and wind sweep in), but definitely something I want to try building in the future (It probably sits just behind a 'fully' 650b).

    Great stuff, thanks for sharing

  3. #3
    J_K
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    I think I have already commented on the blog, but that is an amazing piece of work! I really like the color, is it semi matte finish?
    I'm not a fan of wishbone seatstays and elevated chainstays, but to get good clearance I think they are very useful.
    If the frame weighs only 5lbs it's very light, mine is exactly 5lbs painted and it's smaller frame with smaller tubes.

  4. #4
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    I miss Friday show and tell nicely done!!
    PAYASO 36er.....Live the Circus

  5. #5
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    Dude, you are killing it! I think your design overcomes a lot of the aesthetic issues I have with elevated stays. Plus, I gotta say, your bike is so phat

  6. #6
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    Nice touch with the bottle cage between the extended e stays
    Your welding is sweet, execution is pro quality.
    When are you taking orders?
    cheers
    andy walker

  7. #7
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    Quote Originally Posted by Meriwether View Post
    I The bike turned out well but for one issue that someone will likely easily point out(other than elevated chainstay bikes are an acquired taste looks-wise). I'd love to hear thoughts on how to improve this design, have at it!
    I've been puzzling over this since you mentioned it on Flickr a while back. Something to do with the chain hitting the e-stay? Or do your calves hit the wishbone?

  8. #8
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    Quote Originally Posted by toby_g View Post

    Had a look at the blog pics, and really admire no.11's forked Seatpost-BB connection; any reason that wasn't replicated here? Ease of construction? Stiffness?

    The UK isn't really the place for fat bikes at the moment, maybe if they had enormous inflatable tyres (BBC News - UK floods: River levels rise as rain and wind sweep in), but definitely something I want to try building in the future (It probably sits just behind a 'fully' 650b).

    Great stuff, thanks for sharing
    Thanks!
    I didn't do the forked seat tube just for ease of fabrication. That was a total pain to fixture and braze! I'm not sure it did a whole lot, at least noticeably on a bike with 4.5" tires and 4psi in the tires. I actually just got that bike back from the friend I made it for so I'll be testing it side by side with the new eFatty. I also think the streamline tube i used to brace the chainstays to the seat tube on the recent frame is way stiffer than the plate i used for the last one. This new frame feels very stiff with the full 3/4 straight gauge back there, so I don't notice the flex associated with normal e-stay MTBs.

  9. #9
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    Quote Originally Posted by J_K View Post
    I think I have already commented on the blog, but that is an amazing piece of work! I really like the color, is it semi matte finish?
    I'm not a fan of wishbone seatstays and elevated chainstays, but to get good clearance I think they are very useful.
    If the frame weighs only 5lbs it's very light, mine is exactly 5lbs painted and it's smaller frame with smaller tubes.
    Thank you J_K!
    The color is a bronze powder that has tiny flecks if you look close. It didn't turn out as nicely as I'd have liked. I was hoping that it'd better match the rims...but oh well.

    It's relatively easy to get the clearance with wishbone stays, yes. That's the main reason I did it since I don't have a 5" bender or whatever it'd take to make that bend in the seatstays. Being such a short rear end it'd have to be a huge bend very quickly past the tire.
    I'll have to up my frame's estimate to 5.5lbs then

  10. #10
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    Quote Originally Posted by fixxer View Post
    Dude, you are killing it! I think your design overcomes a lot of the aesthetic issues I have with elevated stays. Plus, I gotta say, your bike is so phat
    thanks man, it looks better than some estay bikes but yeah, they're on the whole so UGLY! But Cunningham had it right, they just make sense for some applications.

  11. #11
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    Quote Originally Posted by todwil View Post
    I miss Friday show and tell nicely done!!
    I unknowingly submitted on friday! Nice, let's keep it going!

  12. #12
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    Quote Originally Posted by afwalker View Post
    Nice touch with the bottle cage between the extended e stays
    Your welding is sweet, execution is pro quality.
    When are you taking orders?
    cheers
    andy walker
    The flask cage actually had to be 'retrofitted'...got to try my hand at welding stainless...
    Thanks for the nice words, i actually took my first real order last week (someone I don't know contacted me). I'm not officially open for business though!

  13. #13
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    Quote Originally Posted by dr.welby View Post
    I've been puzzling over this since you mentioned it on Flickr a while back. Something to do with the chain hitting the e-stay? Or do your calves hit the wishbone?
    You got it dr.welby. The chain rubs on the rear bend of the s-bend chainstay.
    Check out this picture of 3D's bike. Other than it being a belt drive single and made of AL, what is the main difference? I was too focused on the tire and crank clearance and just missed the chain clearance as it goes up the cassette. I crimped the chainstay so it's not a problem. But next time, if there is one, i'll not do s-bends and figure out a new way to raise the stays vertically.

    e-Fat-3d-snowbike2.jpg

  14. #14
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    Nice!
    First off, awesome looking bike. Second nice call on the skis. I've been dying to build a fat bike for long ski approaches. I've had one designed, but it's just not in the budget for a while. Done anything cool with it yet?

  15. #15
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    e-Fat

    Quote Originally Posted by adarn View Post
    Nice!
    First off, awesome looking bike. Second nice call on the skis. I've been dying to build a fat bike for long ski approaches. I've had one designed, but it's just not in the budget for a while. Done anything cool with it yet?
    Thanks Adarn! The ski pannier is something I've wanted to make for a couple years, from when I lived in Colorado and would never skin into places in because it was 6 or 10 miles of flat before getting to the turns. This bike will make it fun and faster both ways. Only problem is I now live in a state with persistent drought, worst winter ever. I also need to learn where the turns are, so no, haven't used it yet

  16. #16
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    Nicely crafted!

    The thing that interests me most is the front geo. with both a slacker than normal HT and more rake/trail, I'd be very interested in the handling. I have been contemplating the same things myself, and looking at similar numbers. I'd be very interested in how it steered.
    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
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    Quote Originally Posted by TrailMaker View Post
    Nicely crafted!

    The thing that interests me most is the front geo. with both a slacker than normal HT and more rake/trail, I'd be very interested in the handling. I have been contemplating the same things myself, and looking at similar numbers. I'd be very interested in how it steered.
    Thanks TM.
    I'm giving this geometry a thumbs up. I've only ridden it twice on snow though, several times on dirt. It's been a banner year for LACK of snow here. The thing I noticed most is the slower steering and seeming increase in stability at slow and faster speeds. The slow speed one trips me out since I thought there'd be more wheel flop with so much trail, but there really wasn't. You rarely ride up super steep hills when on snow (you're hiking if you do) so you don't get any of the wheel flop associated with slack HTA's and lots of trail of normal MTB's.

    The steering is slower and less fidgety. My other fatbikes had 70 or 70.5 deg HTA's and it was a task to keep them on a narrow packed trail when moving slow.
    With steeper head tube angles it felt like any imbalance from me and I'd be off the trail and off the bike.

    My current thoughts are pretty much the polar opposite of what I thought i'd want on a fatbike. I thought a geometry with more weight over the front wheel would increase slow-speed stability, not lessen it. But I've learned to throw most preconceived notions out the window when it comes to fatbikes. The slack angle seems to enable the front wheel to do what it wants more when less weight is on it, and you don't get thrown off the trail as easily in the process. Downhills are better obviously too with this geo.

    It's interesting to me that the new Salsa Beargrease has a 68.5 HTA and somewhat short chainstays too. I think the fatbike geometry trend is going the way all mtbs seem to be going.

  18. #18
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    Great Feedback, Whit!

    It does indeed stand to reason that it would have the effect you mention, but we also know that reason does not always play out in usage. Good to know. If I ever get in a position to build another bike - it doesn't SEEM like it these days - I'm definitely going that route. In the short term, I'd like to pop an On One fork on one of my bikes to get a feel for that sort of change, and see if it was at all transformative.

    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  19. #19
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    Quote Originally Posted by Meriwether View Post

    The steering is slower and less fidgety. My other fatbikes had 70 or 70.5 deg HTA's and it was a task to keep them on a narrow packed trail when moving slow.
    Do you still have any of them built up? I'd like to see how much the weight distribution has changed.

  20. #20
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    e-Fat

    Quote Originally Posted by dr.welby View Post
    Do you still have any of them built up? I'd like to see how much the weight distribution has changed.
    Trying to part together #11 to ride side by side for that exact purpose. But the chainstays on that one are 467 so that may skew my "results"

  21. #21
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    Meriwether

    Thanks for sharing your build.

    e-Fat-img_0008.jpg

    e-Fat-img_0009.jpg

    When I built my E-stay, the engineering analysis done showed that it was better to lock down chainstay movement before they attached to they down tube. A simple understanding of this is if you hold out in front of you the palms of your hands. Place a ball or tube and rock your shoulders, you get a rotation - right. Now if you place the ball/tube forward to you fingers and touch your palms together and now rotate your shoulders, no rotation. The conclusion is that the downtube connection is not stressed, and the chainstays cannot add rotation to the seat-tube joint. (The stress at the DT was important to me as my wall thickness is only .5mm).

    The second issue, chain clearance, in my build I used unicrown fork blades (CX Deda), with the link to the DT being Columbus Life seatstays. I recall that the unmitered butt end to butt end measured about 90mm. I see that Nova now have what appears to be more generous bend surplus at the top of their CX fork blade which might allow it to be used in the Fat bike application. If it does, this method could be handy as being tapered, chain clearance is less of an issue and fork blades are very 'bendy' when needed. I got 4 bends in mine.

    The testing that I did revealed on this fork-blade/seat-stay arrangement showed forces able to flow pass the seat tube joint and the SS section acting like a spring to kill the stress. I have no problems whatsoever with this layout, getting on 2.5 years now.

    Hope this helps a little in expanding understanding of this lay-out. Being different, it looks unconventional, and I have to admit that in all my studies of this layout, that I am yet to see a truly elegant variant, but the design is well suited to how you have used it.

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

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