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  1. #1
    PTW
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    Gusset length & butted tubes

    Hey guys i was just wondering what you opinions are on how long you think gussets should be when used with butted tubing?
    Iv purposely left out details to get a broad range of opinions/answers.

  2. #2
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    If you have to ask...

    Don't bother with them unless you're willing to do the actual engineering (or pay someone else to do it) to figure out what you need. Otherwise you're just moving stress risers around, at best, or sometimes making things worse.

    -Walt

    Quote Originally Posted by PTW
    Hey guys i was just wondering what you opinions are on how long you think gussets should be when used with butted tubing?
    Iv purposely left out details to get a broad range of opinions/answers.
    Waltworks Custom Bicycles
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  3. #3
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    Wile Walt's posting has some good advise in it I don't follow his belief system on this one , could be I was schooled in gusset's as a young lad by KB himself and later Jensen the head engineer at Bontrager .

    I have used Gusset's on ALL my butted tube bikes without trouble , before you say anything please keep in mind my bikes are ridden by Pro's and Joe's alike and after 5+ years I haven't seen a frame come back broken so take this advise as it stands .

    Gusset's should ALWAYS be left open on the end , there is NO good reason to weld these all the way around , you need to leave a open inner facing radius cut to help the stress / forces to escape from the joint .

    I personally do not add scallops to the sides of my gusset's either , this is a personal preference and I'm not 100% sure if this makes a difference anyway .

    MAterial - ALL gussets need to be laser cut from a piece of TUBE , do not make them from cold rolled sheet and roll the radius into them .
    What happens when you hit a piece of cold rolled with a hammer ?
    It's develops a ripple or dent , this is exactly what will happen when you use a cold rolled gusset and you bike take a solid hit the gusset will absurd the hit and cause the gusset to wrinkle .
    The difference from a formed gusset and one that has been cut from a solid tube ?
    Structure - the tube gusset will retain it's form after several hit's were a formed / cold rolled gusset will absurd the stress forces .

    Welding - I suggest building the frame then fitting and welding the gusset on afterward , do not fit the downtube and gusset on at the same time and weld them together it just doest work and you wont get the proper weld penetration into the downtube headtube joint as you might think you would.

    Length - this can get a bit tricky with butted tubes , I prefer to run the end of the gusset at least .50 -.75 away from the end of the butted section.
    I suggest using 1.0 to 1.25 away from the end gusset to the end of the butted section on frames used for more aggressive riding .
    NEVER make your gusset longer than the butted section of the frame or this will split your frame and DT like a can opener !!!

    Good luck PM me with any questions you might have


    Practice - practice makes perfect keep trying until you have something your confident in .
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  4. #4
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    "Welding - I suggest building the frame then fitting and welding the gusset on afterward , do not fit the downtube and gusset on at the same time and weld them together it just doest work and you wont get the proper weld penetration into the downtube headtube joint as you might think you would."

    been wondering about this....thanks!

  5. #5
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    Quote Originally Posted by Evil4bc
    Gusset's should ALWAYS be left open on the end , there is NO good reason to weld these all the way around , you need to leave a open inner facing radius cut to help the stress / forces to escape from the joint .
    The open end is a guaranteed source of corrosion, unless you never get your bike wet or keep a frame for more than 5 years.
    Quote Originally Posted by Evil4bc
    MAterial - ALL gussets need to be laser cut from a piece of TUBE , do not make them from cold rolled sheet and roll the radius into them .
    What happens when you hit a piece of cold rolled with a hammer ?
    It's develops a ripple or dent , this is exactly what will happen when you use a cold rolled gusset and you bike take a solid hit the gusset will absurd the hit and cause the gusset to wrinkle .
    The difference from a formed gusset and one that has been cut from a solid tube ?
    Structure - the tube gusset will retain it's form after several hit's were a formed / cold rolled gusset will absurd the stress forces .
    OK, this makes no sense to me. How is a formed sheet different than a chunk of tube. Are you comparing mild steel sheet to 4130 tube? Why not just form a piece of 4130 sheet? This shouldn't make any difference what so ever.
    EDIT: I just realized that we might be talking about different things. When you say formed gusset, do you mean one that doesn't fully contact the tube along its length, and "bridges the gap" between the DT and HT? If so, I agree that its a bad design because it concentrates all the stress where it meets the DT, rather than spreading it out.

  6. #6
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    Quote Originally Posted by yoyoma
    The open end is a guaranteed source of corrosion, unless you never get your bike wet or keep a frame for more than 5 years.
    Never had a problem here , the powdercoat finish takes up the void in the open area and protects the frame from corosion and mostiure from seeping in .
    Powdercoat when applied properly is basically a polyurthean plastic melted evenly all around the metal surface of the frame thus protecting it from corosion .

    If you leace a open void here were the non welded area is open to contaminants and debris then YES this area will develop rust after some time , but high grade chromoly like TrueTemper OX platinum is pre treated for corrosion and only develops surface rust not pitting rust so so sorta safe other than the nasty orange seepage on rain rides .
    which in that case you could spray the inside of the gusset area with Frame saver and to good .


    Quote Originally Posted by yoyoma
    OK, this makes no sense to me. How is a formed sheet different than a chunk of tube. Are you comparing mild steel sheet to 4130 tube? Why not just form a piece of 4130 sheet? This shouldn't make any difference what so ever.
    Tubes are drawn out over a die thus creating a better overall round structure , the gussett form is laser cut out of this drawn tube in the process heattreating the edges and allowing the gussett to retain the outer form from the orignal round structure .
    I believe from my past experience these are stronger and hold up better to repeated abuse when welded properly to a bicycle frame.

    VS

    Sheet even in 4130 form is just that sheet , when you roll sheet into the form, desired it's has then been cold formed and doest retain the same original structure as say a TUBE .
    With past experience I have found that when used in high stress area gussets such as these retain the original properties of sheet metal rather than those of the tubes themselves .

    Conclusion-
    I'm not sure if I'm explaining this right but tube to tube vs tube to formed sheet ? I highly encourage you to try each method and find which works best for your personal fabrication methods and use of intended end product .
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  7. #7
    jimfab
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    butted?

    Hey, i am no sort of structural engineer, but i can say after years in metal fab that gussets are typically used to make up for a defect in original engineering. I.E. you build something... it breaks so you add a gusset. I am not trying to say that people that use gussets on bikes have bad engineering. I know that fabricators that learn with gussets use them, and those that dont...well dont use them, its a sort of style. Gussets can be a form of personal expression . Gussets can allow you to put your personal artistic stamp on things. Gussets can be a great tool. However when it comes to bicyces i have always thought the concept of butted tube was to put the strength where it needs to be and take the weight from where you don't need the strength. I would say that you should consider a thicker butt end or a bigger tube if you are considering a gusset. If you upgrade size and you still don't think it is enough just use .120 wall or get a motorcycle (i kid ). Again, I "aint no engineer", and gussets do have there place in Cretan applications, its all up to you and how you want your bike to look, ride, and weigh.

    cheers

  8. #8
    Who turned out the lights
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    You could also look at a gusset as adding an external butted section in the location the tube needs it most (bottom, at HT joint) and not having it where it is not needed (top of tube).

  9. #9
    jimfab
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    true dat

    Another option is to cope in a bend, this is an old trick of the trade to increase strength in a welded joint. the idea is to get the most metal and weld contact as you can to help spread the load without causing stress risers. this has become very common in production bikes these days. I believe someone on this forum once said "gussets, telling cracks where to start since 1980". Unfortunately this is a very true statement. Gussets don't eliminate the stress on a joint, they just move it. Now you end up with the stress of the head tube closer to the small part of the tube that was only supposed to be in pure tension or compression. Take a look at a high lift crane sometime. It is not unlike a bicycle, it is a series of triangles welded together made from the lightest material posable. The high lift crane is simply an amazing application of physics like a bicycle. I am not sure but i don't think that they use gussets at the joints on a crane. I know that the ladder truck at my work is 100' tall is made of a series of triangles and has no gussets. Again, i am not trying to bash gussets or folks that use them, just saying if you think you need one you may reconsider the underlying structure. But consider coping in a bend as another option.

    Best of luck

  10. #10
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    This thread is in dire need of some photos... I'm assuming, a flat plate gusset is one of these, right?



    And a tubular shaped gusset is one of these, right?



    Quote Originally Posted by jimfab
    Another option is to cope in a bend, this is an old trick of the trade to increase strength in a welded joint....
    and a bent tube coped joint is kinda sorta like the downtube at the HT connection on this bike frame? (note: I realize these are hydroformed aluminum tubes, but I think you get the idea...)



    I do have one question, on this last photo... I'm looking closely at that structural element that links the top tube to the top of the seat tube. Its a little larger than a 'gusset' but is still a small element to better reinforce the frame. I'm seriously thinking of a more Dirt Jump styled 29er frame for my first bike frame project (with a steeply angled top tube, similiar to this Titus frame) and was thinking of mitering a simple piece of tubing to act as this brace, probably half as long as this Titus brace. You know... draw a straight line from top of head tube to rear axle in side view? That would have to leave lots of seat tube sticking up above the top tube, something that would be enhanced with such a brace. Oh, and just cause it looks cool. In attempting to keep inline with this thread topic, what does the team here think of small tube elements used for structure enhancement (particularly for a first time builder?)

    thanks,
    zip
    Last edited by zipzit; 08-13-2009 at 08:01 AM.

  11. #11
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    ZipZit

    The ornage surly you poasted is a typical plate style moto gussett , these have almost NO increse in stranght but increse your heateffected zone all the way back to the middel of the top and down tubes - most bikes with gussett's similer to this will break about .50 back from the end of the weld zone for the plates and the entire section breaks all at once

    Second up - marron surly
    This is a great example of the Tiwan formed gussett , this is what I speak of when I say rolled sheet formed into the shape of a gussett .
    this lil guy when hit hard will act more like a can opener on the underside of your DT and will either crack at the tip or cause the entire DT to bend right at that point .

    Even worse is the "fashion gussett "
    ( looking for a decent pic now )
    This is the gussett that we have all seen on production bikes were the gussett is welded to the downtube but in NO WAY contaqcts the headtube at all .

    Overkill gussett , I think we can add more metal in here someplace , or weld on another plate here or there ???


    LOGO gussett - laser cut pattern or company logo cut into the gussett
    Pictured is the tp tube gussett by the TAKE bmx ( note I really like this one )


    The Volume cutter V2 freestyle fixed gear frame also had a logo gussett , much like many other the logo started to develop cracks early on and most of these frame broke due to the logo cutout's in the gussett . I called this on TRICKTRACK right when the bike first came out .


    Here is a shot of a properly applied top and downtube gusset made from laser cut TUBING !!! notice the heat effected zone is very small and only at the edges of the gusset , this helps the tube it's welded to retain it's strength and this process only heattreats the welded area , once the frame is post weld heat-treated the welded zone then anneal themselves , leaving the non welded zones to air harden as intended by the material manufacture .

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  12. #12
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    Nice!

    Excellent, informative thread. Great photos too. I'll link this from the FAQ.

    -Walt
    Waltworks Custom Bicycles
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  13. #13
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    Quote Originally Posted by Evil4bc

    Second up - marron surly
    This is a great example of the Tiwan formed gussett , this is what I speak of when I say rolled sheet formed into the shape of a gussett .
    this lil guy when hit hard will act more like a can opener on the underside of your DT and will either crack at the tip or cause the entire DT to bend right at that point .
    IMGP3951 (Small).JPG

    The exception that proves the rule ?

  14. #14
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    Looks like it broke at the butt transitions.. if so, bad positioning on that tt cable guide.


    This looks like an impact that was so far above and beyond the frame/materials as to be hard to draw conclusions.


    -Schmitty-

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    Quote Originally Posted by Schmitty
    Looks like it broke at the butt transitions.. if so, bad positioning on that tt cable guide.


    This looks like an impact that was so far above and beyond the frame/materials as to be hard to draw conclusions.


    -Schmitty-

    Agreed, a simple destructive method of locating butts. The result of coming up a bit short on a double. Extreme example but I was suprised that the gussett didnt act as the fulcrum for the failure.

  16. #16
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    Quote Originally Posted by Walt
    Excellent, informative thread. Great photos too. I'll link this from the FAQ.

    -Walt

    Walt
    Your kind words and encourment are always a plus on these boards Thank you
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  17. #17
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    Holy crap - well that pic shows why there's a english kid out there with the net screen name "DMR'sSnap"

    The above frame broke because of 2 factors
    1. The upper cable guide placement , this looks to be brazed onto the top-tube so this means the guy in the factory was a little too hot that day and the top-tube got most of that heat causing the very large heat effected zone .

    2. the lower gusset focused the force when the rider landed straight into the thin section of the butted tube and the toptube wasn't strong enough to stop this from happening .
    In fact it was weekend by the overly hot brazing that the bike broke completely !!!

    Let's keep this thread going as a basis for informative post regarding gusset's and gusseting techniques'
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  18. #18
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    Dollars to donuts...

    I bet the construction was fine. Nothing is unkillable - looks like he shorted a big double, or hit the bottom of a ditch at speed, or ran into a parked car. C'est la vie. I'd say it did it's job as best it could.

    Of course, I don't know what happened to this particular frame, but nothing about that picture screams "bad brazing" to me. It screams "crash".

    -Walt

    Quote Originally Posted by Evil4bc
    Holy crap - well that pic shows why there's a english kid out there with the net screen name "DMR'sSnap"

    The above frame broke because of 2 factors
    1. The upper cable guide placement , this looks to be brazed onto the top-tube so this means the guy in the factory was a little too hot that day and the top-tube got most of that heat causing the very large heat effected zone .

    2. the lower gusset focused the force when the rider landed straight into the thin section of the butted tube and the toptube wasn't strong enough to stop this from happening .
    In fact it was weekend by the overly hot brazing that the bike broke completely !!!

    Let's keep this thread going as a basis for informative post regarding gusset's and gusseting techniques'
    Waltworks Custom Bicycles
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  19. #19
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    Here is a shot of a properly applied top and downtube gusset made from laser cut TUBING !!! notice the heat effected zone is very small and only at the edges of the gusset , this helps the tube it's welded to retain it's strength and this process only heattreats the welded area , once the frame is post weld heat-treated the welded zone then anneal themselves , leaving the non welded zones to air harden as intended by the material manufacture .

    [/QUOTE]

    I know nothing of frame building, but I know plenty about welding. I must say, those are some rough looking welds, undercut all over the place.

  20. #20
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    So, with an open ended gusset, would you weld from the headtube, or toward the headtube? does it matter?

  21. #21
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    Quote Originally Posted by Cracked Headtube
    So, with an open ended gusset, would you weld from the headtube, or toward the headtube? does it matter?
    Not sure if that question was for me or just in general. My answer would be I have no clue, I'm not sure of the best welding sequence for frame building, and I honestly cant tell which direction the weldor went based off the picture. But as far as those welds go, reduced heat or more filler would help with the undercut.

  22. #22
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    Any comments on seat tube gussets / reinforcements? Good idea? Waste of time? (Photos in order from hollow box & fillet gusset --> up..)










    thanks for any and all feedback...
    zip.
    Last edited by zipzit; 08-14-2009 at 12:01 AM.

  23. #23
    what, no trials?
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    This is a friends bike. He isn't a daredevil and was "just riding along" , hit a small rock garden and SNAP!

    I like the way it snapped at the cable guides and the gusset end. I'm guessing it's the butt end also??

  24. #24
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    Heres another DT failure on a bike with the same paint job....
    It failed about 10 miles short of the finish of the CCP, the bike is a size 17"
    the break is just below the end of the gusset, I think the failure was caused by the crowding of the butt with the gusset as detailed by Evil4bc in an earlier post.

    This has been a super informative thread, thanks guys!
    Attached Images Attached Images

  25. #25
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    You get what you pay for on those Redlines. Total POS made in China. Poor design, poor spec, poorly made. Reminds me of the first Dedacai Kona 29er frames.

    Drawing any conclusions from that other taco'd frame is difficult not knowing what the tubes are and where the butts are. That impact was way above and beyond regardless. The tt cable guide looks very suspect though. I would guess that huge ass dt gusset just applied force down the tube until the butt, and bamo.


    -Schmitty-

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