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Here is one I made earlier. Stainless steel frame

Discussion in 'Downhill & Freeride' started by bikemonkey, Feb 1, 2008.

  1. bikemonkey

    bikemonkey Chimp

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    I am always reading the stuff in here but I only registered today.
    Over a year ago I started designing what in my thoughts was my dream bike. I did a lot of research, look at different bikes, tried to define what was good and bad. analyzed different suspensions systems and their advantages and disadvantages. after a few months of designing I came up with this:



    and then with time it evolved into this:



    a few more adjustments and it was time to start building the bike.
    It looks like a mad cross between a brooklyn and a dark cycles. but the resemblance stops there, just on the looks.
    The frame is made in stainless steel to MIL specification and the suspension linkage in 7075 aircraft graded aluminum. I spent a ton of time and resources in the machining of various components.
    the bike and suspension geometry is the formula that came out of the extensive initial research.



    it has two different chains, there is no pedaling or chain growth induce bobbing. it has a rearward rear wheel path and the frame without shock weights around 10 pounds. the entire bike is weighing around 46 pounds and that is including a geared 8 speed sturmey archer hub and really old components. with a bigger budget a lot of wight could get shredded of it.





    it is a really short bike with only a 43.3 inches wheel base and an even shorter chain stay - 15.7 to 16.9.

    it travels up to 10 inches at the rear, but it is currently set at 8.



    It rides really good, it sticks to the ground in corners like anything else I have tried. every single rider that has tried it has fallen in love with it and suggested that I should start making some more.

    I am not ready to quit my day time job just yet, I am working in a longer front triangle (only an inch longer) and I waiting on my new alfine hub with trigger shifter to arrive to test it some more. (the current sturmey archer is only grip shift compatible .... no comments there) and then give it a good paint job.

    I hope you guys like it, and any feedback is welcome.
    cheers
     
    #1 -   Feb 1, 2008

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  2. MtnbikeMike

    MtnbikeMike Turbo Monkey

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    That bike looks very well-made from the pics. How do you adjust the travel? Is it one of those 4 holes in the swingarm?

    :thumb:
     
    #2 -   Feb 1, 2008
  3. Stray_cat

    Stray_cat Monkey

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    I like what you have going on with the geo and shock mount. Any plans on trying the new SRAM 9spd hub (I'm not sure if their out yet). The production sample I have felt pretty nice, and it's a slightly more internalized part. No CJP exposed. But, it is only grip shift compatable.
     
    #3 -   Feb 1, 2008
  4. DBR X6 RIDER

    DBR X6 RIDER Turbo Monkey

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    That's not a bad weight. It looks like it could easily be heavier than that...even with old parts.
     
    #4 -   Feb 1, 2008
  5. sriracha

    sriracha Monkey

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    wow.

    nice bike and nice manufacturing! the frame looks awesome!

    i want one.

    i especially like the multiple holes offering setup variation, like shock eye to eye and leverage ratios.
     
    #5 -   Feb 1, 2008
  6. jonKranked

    jonKranked Press Button, Receive Stupid

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    hey man that is a very slick looking bike... i love seeing homemade steel :thumb:

    not to sound like i'm trying to knock you (i'm not), but i'd be curious to see how much better it would get with a newer shock!
     
    #6 -   Feb 1, 2008
  7. jon-boy

    jon-boy Monkey

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    #7 -   Feb 1, 2008
  8. FCLinder

    FCLinder Turbo Monkey

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    Great Concept man!!! It looks great. I am happy to see more homemade frames. Keep up the good work. Can't wait to see your ride review.
     
    #8 -   Feb 1, 2008
  9. mandown

    mandown Poopdeck Repost

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    can't comment on the design, other than aesthetics. it looks great. keep working it and maybe you will quit your day job :thumb:
     
    #9 -   Feb 1, 2008
  10. SuspectDevice

    SuspectDevice Turbo Monkey

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    Actually the SRAM Inter9 will work with a friction shifter. Don't tell anyone at Sram though, OK:pirate2:
     
  11. no skid marks

    no skid marks Monkey

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    Very nice,don't get why you're running so much chain,why not one chain and one idler?
     
  12. xy9ine

    xy9ine Turbo Monkey

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    then he'd have to run some sort of tensioner that could suck up a fair amount of chain growth, and most likely a chainguide as well as the chain would be whipping around a bit. that's a clean jackshaft configuration with no chain slap. nice work.
     
  13. no skid marks

    no skid marks Monkey

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    Yeah I forgot it had a single speed type set up with the geared hub.Does the chain tension change at all,I'd imagine it does a tiny bit unless you had equal sized sprockets.Lahar type tensioner wouldn't need that much chain and only one.
    You'd be able to knock a lot of weight out of it with a deraileur,yes sad but true.You'd also get slightly more active suspension.But I guess you know all that,and weighed it up. I'd run with a geared hub myself. Sram 3 speed for racing and 7 or whatever for everything else.
    Please keep us updated. Love your work.
     
  14. buildyourown

    buildyourown Turbo Monkey

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    Nicely done. Especially for a first try.

    What type of tubing exactly did you use for the front triangle? Where did you source it?
    What method did you use to join it?

    I am a weldor and framebuilder and I really can't tell from the pics.
     
  15. SPINTECK

    SPINTECK Turbo Monkey

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    I like it. Concentric drive for long travel bikes is probably the way to go in theory, but I haven't tried one.

    Bummer you're half a world away or I would come over and test ride it! :)
     
  16. sriracha

    sriracha Monkey

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    anybody know where one could purchase a SRAM Inter9 disc hub???

    are those available in the U.S. market yet???
     
  17. P.T.W

    P.T.W Monkey

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    I am not ready to quit my day time job just yet, I am working in a longer front triangle (only an inch longer) and I waiting on my new alfine hub with trigger shifter to arrive to test it some more. (the current sturmey archer is only grip shift compatible .... no comments there) and then give it a good paint job.

    good work:clapping::clapping::clapping:
    wouldnt it be a shame to paint stainless???? just crack out the scotchbrite pads...lighter than paint to:monkeydance:
     
  18. EVRAC

    EVRAC Monkey

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    Awesome.

    Alfine should be better than Sturmey, but still not very durable for a dh bike. What about Rohloff? What about mounting the hub at the main pivot? (I know that's easier said than done.)

    I agree about not painting it.

    Now you just need a new fork.....

    Anyways, great job.
     
  19. demo 9

    demo 9 Turbo Monkey

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    wow, that bike is incredable and how u came up with that design is above me but if u did sell it i wood probably buy it if was lookin for a new bike
     
  20. TomBo

    TomBo Monkey

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    Please don't paint it. Its way too sexy naked. What SS tubing did you use? What kinda of jig did you use for welding / brazing it?
     
  21. TGR

    TGR Monkey

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    wow, really clean frame, I should try to build myself one, there's a lot of nice homemade chromo dh bikes popping on bike sites now...
     
  22. CBJ

    CBJ Turbo Monkey

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    Nice job - must be a nice feeling riding a your own bike.

    What fork is that?
     
  23. bikemonkey

    bikemonkey Chimp

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    Yes they are: http://sheldonbrown.com/harris/sram.html

    but I have read reviews in where they say the shimano shifts better, even under pressure.

    I am still worried about the alfine and its performance. But it is on its way, so I will have to use it anyway. Does anybody has any experience on how trusty the alfine hub will be?

    Rohloffs hubs are great, but currently I can't afford one, and I would love to have the hub built in the frame. may be my next design will be like that.

    About the jig .... I made it, it was even harder than making the bike. and I used a mig welder and then polished the welding to give a smother looks. next time I think I should go for a tig welder.
     
  24. ÆX

    ÆX Turbo Monkey

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    i have been moding my alfine and its def beefier than the 7s nexus i used last time. the axle is 10mm and steps up to 12mm thru the hub for strength and stiffness.

    i got one of these and these to easily adapt. will make production a lot simpler with less parts to build.

    anyway the alfine has quicker engagement and def better shifting under load. trigger shifter take some getting used to b/c its backwards.
    thumb upshift, index finger down.

    you can get them in Canada now if you can get a shop to buy you one.
     
  25. bikemonkey

    bikemonkey Chimp

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    The fork is a ddg floozy, from around 1997 or 1998, and still going strong. it has 7 inches in travel (depending on the day). it was one hell of a fork in its day and not that bad by today standards. I have updated some of the insides.

    BCD: have you used the hubs on the wheel or built in the frame? I think the lateral and torsional forces will kill it with in a few days of riding if it is being use as a wheel hub. I really hope I am wrong, otherwise I will have to fit the bike with a dérailleur.
     
  26. ÆX

    ÆX Turbo Monkey

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    yeah, i would think it would. that and the unsprung weight is horrible.

    i have used it on a xc bike. have not finished my dh frame for it yet.
     
  27. PatBranch

    PatBranch Turbo Monkey

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    Awesome bike! I agree about not painting it. Just polish it and maybe clear coat it.
     
  28. Pslide

    Pslide Turbo Monkey

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    Bikemonkey, that's fantastic! You've done what I've always wanted to do...design and build your own bike. I've done plenty of the designing, none of the building.

    I really like the overall design, high pivot, low CG, linkage design, steel brazed construction - it's all fantastic!

    However, might I suggest something, in the humblest possible way? Looking at the way the shock forces will act through the linkage and into the frame, it looks like the force between the yellow linkage in your diagram and the frame will be very very big!

    That force, and all the forces from the swingarm are acting on that small tube joining the downtube with the seat tube. That's a lot of force, especially considering if you bottom out the suspension on the large drop!

    Of course, steel is very strong and the tube is quite short, but maybe you should think about adding a gusset between that tube and the downtube for added strength.

    I made a diagram below. My force analysis is probably wrong (I've been out of school for almost 10 years now), but I think the general idea of the forces is correct. And you can see where I'm suggesting a gusset.



    Anyway, great job! You deserve a lot of respect! I hope this bike brings you lots of success, both riding and designing and building!

    -Aaron
     
  29. dirtdigger

    dirtdigger Monkey

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    with out knowing what the down tube is, i'd say it'll need some extra support? like a big head tube gusset and/or a tube from the down tube to the seat tower?
    I say this as i bent the down tube on my homemade over the weekend plus there was some mainframe flex on high speed rough stuff, felt like the fork was flapping around on the bike like a lose head set or sloppy bushings in the forks