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  1. #1
    CTB
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    The birth of a titanium part - 4-Banger content

    I thought you guys might like to see this.

    Last month I spent 13 hours straight (yes…) with my friend in his machine shop (read: basement) making a new shock mount for the 4-Banger to replace the one that failed. We did not finish the part, believe it or not. Ti is a bit of a pain to machine – you cannot use a high feed rate like with aluminum or even steel, so things took a VERY long time to complete. It is a BEAR to tap for something like an M6x1.0. We could have pounded out probably two aluminum parts in the same amount of time.

    The alloy we used is 6Al-4V ELI. This is the same material used in hip replacements – the ELI (“extra low interstitial”) exceeds the regular 4V stuff in several ways, I’m told, and is very immune to outside substances, etc.

    Here’s a slideshow of the pics I took showing the birth of a part.

    http://s25.photobucket.com/albums/c9...view=slideshow

    Also, we had some fun with the shavings. I learned that Ti burns like a mofo if you use the shavings and not a chunk of the stuff.

    We quit at 1:30am with only two small operations left. However, we were having issues with the mill, so we decided to start again when fresh, rather than scrap a 13-hour part made from expensive Ti.

    My friend with the shop uses it for income, so he wasn't able to finish the part until last night. I now have it installed and will go for my first ride on the new part tomorrow.

    For the geeks: I was able to set my eye-to-trunnion to exactly half way between the Rock Shox coil setup (130mm, too slow for steering) and the Rock Shox SID air shock (140mm, too quick for steering). BB height went from 12.75" (too low - I was grounding out) to 13.125". Hopefully this will all work out, and hopefully the Ti part will make up for the liberties I took with the engineering and not fail. Plus the part is adjustable, so I can tune in the head angle from here.

    Here's a teaser - we went from this:



    to this:


  2. #2
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    looks good
    _______________
    1x10 IS SO FINE on my 21.9 lbs IBIS SL-R
    11-36 XTR in the rear, 36T wide-narrow upfront

  3. #3
    smell my finger
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  4. #4
    CTB
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    I guess I should add this:


  5. #5
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    Good luck with that part, hope it works out for you.
    Cost wise, would it be feasable to make it a production part for us "4 Banger Brethren" ?
    I am still running my SID and got my stock shock as a back up. It would be nice to put a Fox on it though.
    Keep us posted.

    Ken

  6. #6
    Seeeriously easy Livin
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    That sure was a big chunk to machine such a small part, I'm guessing you already had the material.

  7. #7
    CTB
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    Flystagg, it still is a big chunk of titanium. We only used the corner of that big block, so the bulk of that block is still sitting on my buddy's metal stock shelf. Plenty more parts can be made from that block, which is nice.

    Ken, unfortunately, no. This part has over 16 hours of labor in it, plus the cost of the Ti, etc. Maybe "bigger" equipment could make the part faster, but Ti does require a slower cutting speed than steel or aluminum. I now understand why Ti bikes and parts cost so much. Also, this design required custom bolts to be fabricated for the shock attachment area because of the lack of real estate in there for fastening. This is what led to the failure of the aluminum part, so I'm hoping the much stronger Ti can make it live. The ideal solution would be a threaded-body air shock with a smaller diameter than the Float RL that I used, enabling the use of the original 4-Banger hardware (which are standard bolts available at places like McMaster-Carr), but I've never found such an animal.

    Or, one could make the part from steel at the expense of weight. For comparsion, here are the weights of the various 4B shock setups:

    SID air shock with bolts and reducers: 306g
    Rock Shox Super Deluxe coil-over setup with trunnion, bolts: 573g
    My Fox with Ti trunnion, reducers, and bolts: 367g

    Because the bike is already porky by today's standards, I wanted the weight save of Ti or aluminum, which as you can see is 210g or so, nearly half a pound.

  8. #8
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    Why not make it out Aluminum?
    _______________
    1x10 IS SO FINE on my 21.9 lbs IBIS SL-R
    11-36 XTR in the rear, 36T wide-narrow upfront

  9. #9
    CTB
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    The first version of this part was aluminum. This is what happened:

    http://forums.mtbr.com/showthread.ph...28#post5687728

  10. #10
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    Good job!

    After some health issues, I finally got to try out the new part today. I'm extremely happy. This was the first time I got to ride this frame with my current wheel/tire setup and the all-Fox suspension. Head angle is dialed in nicely, and the ride quality was excellent. I also took advantage of the increased travel, based on the position of the sag ring after the ride. The bolts retained their torque (checked with my tq wrench), so that's a step in the right direction. Now to see how long she lasts...keep your collective fingers crossed!

  11. #11
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    '11 Jedi
    '01 Straight8
    '01Rocket88< ran over it.. always do a full walk around!
    '00 Homegrown

  12. #12
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    How did I miss this for soo long?!? This is a fabulous thing and I'm fully envious of your friend.

    I wonder if it would be possible to make an aluminum one with steel inserts for the bolts. Any chance you want the sell the wrecked aluminum collar?

    Can we get pictures of it on the bike?

  13. #13
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    Thanks, Shwinn8.

    Bad Mech, glad you're back aboard. Yes, my friend has some really great equipment in his shop, and he's done it all by shopping extremely wisely and getting good deals. He also gave me the deal of the century on this latest part. You don't want to know what I paid for it.

    I think it may be possible to make an aluminum one with steel inserts. In fact, now that the Ti part is complete, Stage 2 of the project is to give the aluminum part to another friend of mine to work on a time-sert-style fix on it, the idear [sic] being to have a spare trunnion handy if one should give up the ghost.

    There are also custom bolts I had made (from yet another friend) for this installation. It wouldn't be possible without these.



    What you see are, from left to right, the custom bolt (prior to being trimmed even shorter in the thread area), my make-shift trial setup just to prove out the function of part, and then the original style of bolts used on the Banger, but trimmed to the length needed for this part to work. The relief between the shoulder and the threads are why one needs custom bolts for this. I have not met fastener engagement standards with it and needed every last bit of thread I could get, hence the custom bolts. It's a risk I'm willing to take with my own bike, but not with others.

    There are some pics of the unit on the bike at the end of the slideshow. Here's a teaser, but if there is an angle or something that you'd like to see, let me know.



    Though for all intents and purposes, it looks just like the aluminum one (as seen below) did, just not as nice of a surface finish:



    I really hope this baby holds up. I smiled a ton on today's ride - I'm a suspension geek (both for bikes and cars), and I love it when a suspension works well.

    BTW, if anyone knows of a threaded-body air shock that has a smaller diameter than this Fox (which is about 41mm), I'd love to see it. If Specialized made a threaded-body version of those teeny-tiny Brain shocks they have now, that would really be the ticket.
    Last edited by CTB; 06-29-2009 at 05:57 PM.

  14. #14
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    I was thinking, with the aluminum collar, instead of putting a time sert in, it might be worth drilling the threads out, recessing the back side slightly, and squeezing in a steel t-nut.That was you're not having to count the aluminum holding any threads at all.



    By the way, I still owe you measurements off my Straight 6.

  15. #15
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    Hmmm, interesting. The biggest issue is still the core issue - the thickness of the trunnion where those T-nuts would go is a skinny 7mm, and then that has a 2.5mm counterbore where the shoulder bolt engages it. I suppose you could eliminate that and then shim the shoulder bolts outward with 2.5mm of washers. I've just never determined if Schwinn put that counterbore in there to fit the standard part, or if they utilize that bearing area (which is an M8 diameter, vs the M6 threads on the bolt) to take the load off the M6 portion. It's not a press fit, so it may not be load bearing. I'll have to see what sizes of those T-nuts are out there.

    EDIT: BMech, this one could show promise if trimmed down for depth and the inside diameter (the 19mm dimension).

    http://www.mcmaster.com/#98965a310/=2j8hn1

  16. #16
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    Quote Originally Posted by CTB
    Hmmm, interesting. The biggest issue is still the core issue - the thickness of the trunnion where those T-nuts would go is a skinny 7mm, and then that has a 2.5mm counterbore where the shoulder bolt engages it. I suppose you could eliminate that and then shim the shoulder bolts outward with 2.5mm of washers. I've just never determined if Schwinn put that counterbore in there to fit the standard part, or if they utilize that bearing area (which is an M8 diameter, vs the M6 threads on the bolt) to take the load off the M6 portion. It's not a press fit, so it may not be load bearing. I'll have to see what sizes of those T-nuts are out there.

    EDIT: BMech, this one could show promise if trimmed down for depth and the inside diameter (the 19mm dimension).

    http://www.mcmaster.com/#98965a310/=2j8hn1
    I think you could get rid of the counter bore safely. Like you said, it's not a press fit, so the actual walls of the counter bore aren't taking any force. I'd think the force is all being transferred by the threaded portion, and the shoulder bottoming against the side of the trunion mount, both of which are preserved with the aluminum collar and t-nut.

    Trimming for height is easy, but what do you mean by the inside diameter?

  17. #17
    CTB
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    The base diameter of the T-nut I linked to is way larger than the area available on the trunnion. I believe it is 19mm, but there is no where near that on this trunnion. 19mm is larger than even the flats with the counterbore, so the trunnion would need redesigned to use a base that large, or the base would need to be trimmed. Either could be done, of course.

  18. #18
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    Quote Originally Posted by CTB
    The base diameter of the T-nut I linked to is way larger than the area available on the trunnion. I believe it is 19mm, but there is no where near that on this trunnion. 19mm is larger than even the flats with the counterbore, so the trunnion would need redesigned to use a base that large, or the base would need to be trimmed. Either could be done, of course.
    Why not cure the base of the t-nut to follow the inside curvature of the trunion, and steal some thread area from the inside of the trunion to allow the t-nut to keep it's full base?

    By the way, are you riding toe clips?

  19. #19
    CTB
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    Sure, that would work on the bottom of the T-nut ("bottom" in reference to the direction of the shock), but the top of the base would stick out above the top of the trunnion. Not a huge deal, but not the cleanest. Ideally to use a T-nut with that large 19mm base diameter, the trunnion would need to grow vertically by about 10 more mm than it is currently. That would be possible if one removed the lockout lever on the shock (which I never use). The holes in this trunnion are offset to be able to get the proper I-to-Trun lengths for the 4B. A simple flat trunnion like the original Jekyll or Banger ones would have given I-to-T dimensions that were far too short.

    One issue that comes to mind is I'm not sure how one could machine that relief on the inside of the trunnion. The external counterbore was relatively easy, but I'm not sure how we could do an internal counterbore for the base of the T-nut.

    Yep, I ride toe clips. Tried clipless for a year and a half and never liked them. Clipless are definitely better for everything except one thing: I could never get out of them when the need would arise, and that didn't go so well on Arizona rocks (or Michigan rocks, for that matter). I took them off while recovering from knee surgery to avoid twisting the knee and never went back. Maybe someday I'll try a different style (these were the original Scott clipless SPD's that came with my '98 Moab) and see if I can get out of them better.

  20. #20
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    Quote Originally Posted by CTB
    Yep, I ride toe clips. Tried clipless for a year and a half and never liked them. Clipless are definitely better for everything except one thing: I could never get out of them when the need would arise, and that didn't go so well on Arizona rocks (or Michigan rocks, for that matter). I took them off while recovering from knee surgery to avoid twisting the knee and never went back. Maybe someday I'll try a different style (these were the original Scott clipless SPD's that came with my '98 Moab) and see if I can get out of them better.
    That's funny because I rode the original Scotts on my bike up until this year. Did you have the tension on them turned all the way down? They were agravating me knees even after a lot of fiddling, so this year I'm on Crank Bros Eggbeaters and love them; my knees feel great and they're very easy to get out of.

  21. #21
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    Ditto on the Egg Beaters! I just bought another set ( Candys ) for my single speed.

    Ken

  22. #22
    CTB
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    Sorry...
    Last edited by CTB; 07-01-2009 at 11:48 AM.

  23. #23
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    Database
    Last edited by CTB; 07-01-2009 at 11:48 AM.

  24. #24
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    freaked
    Last edited by CTB; 07-01-2009 at 11:48 AM.

  25. #25
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    out
    Last edited by CTB; 07-01-2009 at 11:48 AM.

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