First Ventana Kit Build- Mtbr.com
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  1. #1
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    First Ventana Kit Build

    I'll be starting my first Ventana full suspension build for myself soon and have a few questions. Walt, I saw some of your old blog post about this too.

    First Ventana Kit Build-full-suspension-seat-tube.jpg

    Will a 1.375" x .035" chromo tube be sufficient at the upper pivot point? The pivot is already mitered for 1.375" so I hope so.

    It looks like the lower pivot gussets provided by Ventana are unnecessary. Is there any reason I can't put the pivot tube in the middle of the seat tube? It looks like there will be clearance but I haven't done a full mock-up yet.

    There's not a lot of room for bronze fillets around the pivots. Would it be more prudent to TIG these?

    The lower pivot is supplied undersized. Are you drilling this to 15mm after welding?

    Thanks, Joel
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  2. #2
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    Quote Originally Posted by Clockwork Bikes View Post
    Will a 1.375" x .035" chromo tube be sufficient at the upper pivot point? The pivot is already mitered for 1.375" so I hope so.
    That tube size is probably sufficient. However, consider sleeving the tube at the pivot.

    Quote Originally Posted by Clockwork Bikes View Post
    It looks like the lower pivot gussets provided by Ventana are unnecessary. Is there any reason I can't put the pivot tube in the middle of the seat tube? It looks like there will be clearance but I haven't done a full mock-up yet.
    It'll clear the seat tube at the bottom bracket no problem. You do, however, need to pay attention to the top of the seat tube. Using a straight tube, the seatstay bridge or tire can run into the seat tube. Depending on how much travel you're looking for (probably transitioning around 4"??) you'll need to bend and/or offset the seat tube forward.

    Quote Originally Posted by Clockwork Bikes View Post
    There's not a lot of room for bronze fillets around the pivots. Would it be more prudent to TIG these?
    No, not a ton of space, but I've done it. If you have a tight miter, the fillet doesn't really do anything besides hold the pivot in place; it should be supported by the seat tube itself.

    Quote Originally Posted by Clockwork Bikes View Post
    The lower pivot is supplied undersized. Are you drilling this to 15mm after welding?
    I use an adjustable reamer.

  3. #3
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    I have mostly transitioned away from using the Ventana rear ends (building my last few frames with their hardware/rockers now) but I don't want to dig up all that old info, so, random thoughts and maybe useful answers.

    -As Feldy says, 1.375x.035 is fine. Sleeve the tube behind the pivot tower, though, and tie it all together (I just TIG this whole thing).

    -If you move the lower pivot forward by mounting it in the seat tube itself, remember a couple of things:
    1. You'll need to move the rocker pivot forward too, which will mean a bent or cut/welded seat tube. Mock everything up first, it can be quite a juggling act to keep the pivots where they need to go, the seatstay bridge/tire out of contact with the seat tube, and the insertion depth and angle of the upper bent portion of the seat tube compatible with the seatpost you want to use.
    2. Remember that the suspension behavior is going to be determined mostly by where that main pivot goes. If you don't want to get super geeky with Linkage, just line it up with the top of the chainring (whatever size you think you'll use) and you'll be at around 100% antisquat which is a nice neutral place to be. The stock Ventana pivot location will squat a decent amount under pedaling loads (can be desirable, or not).
    3. The angle between the seat tube and downtube will get really tight, which means you also need to very carefully check that your desired shock will fit (including at full compression). Fully mocking everything up before joining the pivot tower is highly recommended.

    -I would TIG everything if you have the ability/tools to do it that way. IMO not a great project to do with fillet if you have a choice. But it can be done.

    -I turn the main pivot tube out to 15mm before welding, then do a light cleanup (sometimes necessary, sometimes not) after welding/distortion has shrunk it a bit. If you leave it stock, you will have quite a bit of reaming to do - and you won't be able to use the swingarm as a fixture to hold the pivot in place while you tack it.

    -The alignment on the Ventana swingarm and seatstays is *atrocious*. You can work around this by just using the rear end itself to fixture the pivots before tacking/joining them. If you assume everything is square and install your pivot points as such, you will probably get an unpleasant surprise. This often means your wheel is not staying perfectly in plane with the frame through the stroke, but in practice it isn't noticeable.

    -Alignment/symmetry of the pivot tower (the steel piece that slips over the seat tube) is likewise often horrible. And it is machined quite sloppily such that it moves around on the seat tube. Make sure you install the seatstays/rockers as fixtures to ensure they are aligned/symmetrical. The yoke on the seatstays is pretty narrow and it will hit the side of the seat tube if you are not very careful here.

    Feel free to call me if you have other questions. It can be quite a can of worms when you first start doing these.

    -Walt

  4. #4
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    Thanks, folks. I have an actual customer's bike to finish up and will then hit the Ventana kit--with more questions, I'm sure.
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  5. #5
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    Here we go. Decided to use a 1.38" x .065" ST and turn down some sections to .035" wall.





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  6. #6
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    Did you also bore out the middle to take a 31.6 seatpost? or are you going with a collar for 30.9? I like the externally butted tube you made! I experimented with some crude centerless grinding to make a 8/6/8 top tube with a really short center. Worked better than I expected.

    Looking forward to more of this build!
    Myth Cycles handbuilt bike frames
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  7. #7
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    The ID is supposed to be 31.62mm but is a little under-sized, so a light ream should do it. Very convenient ID.
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  8. #8
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    That's bold and cool... but if the seat tube doesn't stay *perfectly* straight, it's going to be the reaming job from hell. Remember that you're only welding stuff to one side of the tube!

    Don't ask me how I know this...

    Then again you could just shim to 30.9 and solve it that way if it comes down to that.

    Man I wish I had a decent lathe.

    -Walt

  9. #9
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    I know what you mean. I scored this 1.244" reamer on eBay which should take care of it.

    NOTHING WORKS LIKE CLOCKWORK

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  10. #10
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    Quote Originally Posted by Walt View Post
    Man I wish I had a decent lathe.
    My lament every week. We live in a machine tool desert.
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  11. #11
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    NOTHING WORKS LIKE CLOCKWORK

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  12. #12
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    Things are getting interesting.







    NOTHING WORKS LIKE CLOCKWORK

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  13. #13
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    You should really put more effort into that shock mount. Have some pride, man!

    ;P

  14. #14
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    Progress but my heart's not really in it because all I can think about is how I can make my own rear end. I've got some ideas I just need to flesh out in SolidWorks.

    NOTHING WORKS LIKE CLOCKWORK

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  15. #15
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    Does Sherwood sell the current gen rear end to builders? I ride the previous gen frame which was a custom build and also had the previous gen frame in steel by Curtlo. That frame was destroyed in a head on with a moto. I had Ventana build me a new front triangle using the old stays.
    Ripping trails and tipping ales

  16. #16
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    Quote Originally Posted by Clockwork Bikes View Post
    I've got some ideas I just need to flesh out in SolidWorks.
    That sounds fun. Want some help?
    I might have some time to contribute.
    Write me t@tgwms.com
    My carbon fiber full suspension frame build blog:
    https://carbonmtb.blogspot.com/

  17. #17
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    All done but haven't ridden much since the trails are still pretty soggy here.







    Attached Thumbnails Attached Thumbnails First Ventana Kit Build-26968863867_7c65e3ac44_b.jpg  

    NOTHING WORKS LIKE CLOCKWORK

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  18. #18
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    Killer! That thing came out great! Is that powder coat? I like the fade.
    Myth Cycles handbuilt bike frames
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    http://www.mythcycles.com

  19. #19
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    Bike turned out nice Joel, as always!!
    PAYASO 36er.....Live the Circus

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    I'm sorry what part of "BIGLY" didn't you understand?

  20. #20
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    Noice!

  21. #21
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    Joel, you don't mess around, even when your "heart isn't in it". I love that.

    -Walt

  22. #22
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    Lookin great.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

  23. #23
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    I love it.
    Ripping trails and tipping ales

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