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  1. #1
    mtbr member
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    Titanium seatpost

    I'm looking to make a ti and was hoping to get a little nuggets of info from the collective. I'd like to make a 31.6mm x 400mm post with 20mm offset. Currently I have a 1.25"x.035 that's undersized that will fit in my frame now. I'd have to have it bent locally to get my offset.

    My concerns are that even though it fits it's a really snug fit. I'm not sure .035 will cut it with my fat ass. I could also use 1.25"x.045". I also don't know what size tube to use for the cradle. Speaking of cradle, I planned on using the Enve cradle which has a OD of 30mm.

    For the tube to hold the cradle I was thinking either 1.25"x.083" or 1.5"x.29". With either size I will have to bore out the tube to fit the cradle.

    I'd appreciate your thought...ps I'm north of 200 lbs.
    Last edited by Jamenstall; 06-03-2012 at 03:01 AM.

  2. #2
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    Several of my bikes have custom posts using 1.0" x .035 4130 and they work well, plenty stiff with just a slight flex which I like. I make a alloy seat tube sleeve/clamp with a 1.0" ID, that is pressed into the 1.25 ST. I made one using 1.0 x .021 TI and it was too flexible. 1.25 x .035 should work well. Great thing about them is the springiness, makes it feel like a padded seat cushion. And since your screen name is softbutt....

  3. #3
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    Any info where to buy the ti seat post?

    Sent from my HTC Sensation 4G using Tapatalk

  4. #4
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    Cool, please "post" some pics when you have complete.

  5. #5
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    The posts were custom made for each frame. Since they are designed for the frame, the angle is fixed. They are ridiculously light at 140 grams for a 380mm long post.

    The seat collar/sleeve is pressed into the frame, so no slot is cut in the seat tube. Then the collar is honed and lapped to size. Been running this design on my freeride bike for 5 years and the post still adjusts silky smooth.
    Attached Thumbnails Attached Thumbnails Titanium seatpost-ti-seatpost-036.jpg  

    Titanium seatpost-ti-seatpost-029.jpg  


  6. #6
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    Really?

    By my calculations, 1"x.035"x380mm is 200g all by itself, even with no head.

    Or is that the ti post you're talking about?

    -Walt

    Quote Originally Posted by TacoMan View Post
    The posts were custom made for each frame. Since they are designed for the frame, the angle is fixed. They are ridiculously light at 140 grams for a 380mm long post.

    The seat collar/sleeve is pressed into the frame, so no slot is cut in the seat tube. Then the collar is honed and lapped to size. Been running this design on my freeride bike for 5 years and the post still adjusts silky smooth.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  7. #7
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    TacoMan - thanks for the info. I think I will stick with the .035 that I have on hand. I still need to order the tube for the cradle.

    I've had a little setback with this project. The company who I had planned on bending the tube didn't want the work. So now I will be running a straight tube with a offset cradle (think Eriksen)

    Quote Originally Posted by TacoMan View Post
    Several of my bikes have custom posts using 1.0" x .035 4130 and they work well, plenty stiff with just a slight flex which I like. I make a alloy seat tube sleeve/clamp with a 1.0" ID, that is pressed into the 1.25 ST. I made one using 1.0 x .021 TI and it was too flexible. 1.25 x .035 should work well. Great thing about them is the springiness, makes it feel like a padded seat cushion. And since your screen name is softbutt....

  8. #8
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    I stated the TI post is 1.0 x .021 (which is 140g in the picture above, I weighed it last night), the 4130 post is 1.0 x .035. But 380mm is too long for the TI post, too flexible, I put that post on another frame and use the 4130 post on the frame requiring the 380mm long post. 300mm would be the longest I would want the 1.0x.021 TI, that is why I suggested 1.25 x .035 TI should work well for softbutt's 400mm post.

    I am actually making a post today that is 430mm long out of 1.25 x .035 4130, I'll let you know how stiff it is. I would use TI, but don't have any on hand. If this post is too stiff, I'll order some TI.

  9. #9
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    I built a 31.6 x 430mm post today for my Lunar Newton single speed. I was running a Thomson 380mm that was too short. Also found out after removing the Thomson after just two rides, it was already bent about .010 right at the MAX line where I had it set. This is why I build posts out of steel.

    On my lathe using a mandrel, I turned down the 1.250 x .035 wall 4130 tube to 1.240 OD to fit the 31.6 ID seat tube. I also polished it a little but the machined finished look real nice. This made the tube .030 wall. I also changed the end and welded a cap to the tube instead of inserting a aluminum fitting, this made it look cleaner and also lighter. The seat post weighed in at 314g, pretty light for such a strong post.

    I am taking it on a ride in one hour, but so far it feeels pretty good. I'll let you know how it works out.
    Attached Thumbnails Attached Thumbnails Titanium seatpost-125x430-seatpost1.jpg  

    Titanium seatpost-lunar-newton-ss.jpg  


  10. #10
    Eric the Red
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    Off topic Tacoman, but the computer cases on your manufacturing site are pretty awesome.

  11. #11
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    I thought the seatpost felt real good while riding. You could feel it take the sharp edge off of ruts while seated. If anything, I would want a litlle more flex. Titanium in the same .035 wall thickness would give twice as much flex. Going to .045 wall TI would give about 50% more flex. Note that they would be turned down to .030 and .040 wall. Or I might resize the frame for a 1.250" seatpost.

    edoz, Thanks, that is what keeps me busy. The bike stuff is just a hobby. There are a lot of bike parts I would like to make if I only had more time. I am also building a new supension system for my desert racecar including the custom shocks. One day that shock design will find its way to my bikes.

  12. #12
    bee
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    Quote Originally Posted by TacoMan View Post
    The posts were custom made for each frame. Since they are designed for the frame, the angle is fixed.

    So what you are saying in essence is that since the seat angle is fixed, there is no way to adjust the saddle tilt angle. Correct?

  13. #13
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    Quote Originally Posted by bee View Post
    So what you are saying in essence is that since the seat angle is fixed, there is no way to adjust the saddle tilt angle. Correct?
    correct, the frame angle will never change unless you radically change the fork. Seatposts are adjustable to work on all frames, but if you make it for one frame to the rider preference, no need for adjustments -keep it simple. I already dialed in the angle with the Thomson post installed.

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