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Homemade Reduced Weight Bar

Discussion in 'Chainsaws' started by Jon1212, Aug 10, 2016.

  1. Dolmar Junkie

    Dolmar Junkie Not interested in rehab, just more Saws...

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    Similar, but the referenced unit doesn't have a lick of black paint on its Cannon. So I will need that Carlton to determine if the paint is detrimental to performance...
     
    Last edited: Mar 16, 2018
  2. RI Chevy

    RI Chevy DollyStihlvarna Runner ????

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    He would'nt need a saw then. He could chew wood with his teeth. Lol
     
  3. Dub11

    Dub11 Some body poisoned the watering hole!

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    what a dick move by the ups guy.

    You won' have to worry about paint after I'm done installing some high beams.
     
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  4. Dolmar Junkie

    Dolmar Junkie Not interested in rehab, just more Saws...

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    That's exactly what the postmaster says,
    everytime I wake him up...
     
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  5. KiwiBro

    KiwiBro Pinnacle OPE Member

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    Thanks for the great thread fellas.
    Sorry if I missed it but how did the flex of the CF insert bars compare to solid?
    Also, there are radically different coefficients of thermal expansion of Steel (plenty) and CF (naff-all). Any cracking around seams or delam' of the CF?

    *edit*, further to the above, if the thermal expansion issues are not really a problem, then how about taking an oregon RW and replacing the insert with CF and comparing the weight and flex? It may be the bar can be not just lighter but stiffer at the same time, money and time being no object.
     
    Last edited: Oct 11, 2018
  6. mettee

    mettee Super OPE Member

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    It would be a good choice to use pre-preg carbon or carbon kevlar, and a more complex cut out(engineered for strength) could really optimize weight/strength and end up super light. Bond the two sides through some smaller cutouts and cure it in a vacuum. That way you wont have to bond with epoxy, and from one side to the next it would be solid carbon(interconnected).

    I thought about doing ti, but I think carbon would be far more rigid. Could even source spread tow fiber.

    I'd make a template that matches the shape cut in the bar, then it would lay right in and you could cure it flat and perfect.
     
    Last edited: Oct 12, 2018
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  7. KiwiBro

    KiwiBro Pinnacle OPE Member

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    Another issue with the inserts might be how well they transfer heat from the rails. Epoxy for example is relatively useless compared to steel. Not only that but wouldn't the glass transition temperature of epoxy be below what our bars might get to, thus some of whatever stiffness we observe at room temps might not be there during normal bar use if there is too much epoxy in there with too low a Tg.
     
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  8. mettee

    mettee Super OPE Member

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    Spread tow reduces resin/epoxy left in the cured carbon by removing the voids. There are several higher temp curing resins, that also makes them more high temp stable.

    I have a buddy at Boeing, I'm going to pick his brain on it.

    I have seen resins online that claim working Temps of 300 c, or 572 degrees f. But the resins are more complex to handle/cure. Carbon itself goes way up over 1000 on its own.
     
  9. mettee

    mettee Super OPE Member

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    Using spread tow, could also add in rigidity in ways we need to reduce flex by customizing the direction of the fiber.
     
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  10. mettee

    mettee Super OPE Member

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    "Among the more exotic of resins, bismaleimides and polyimides (close relatives, chemically) are used in high-temperature applications on aircraft and missiles (e.g., for jet engine nacelle components). BMIs offer hot/wet service temperatures (to 232°C), while some polyimides can be used to 371°C for short periods of time. Volatiles and moisture emitted during cure make polyimides more difficult to work with than epoxies or CEs; special formulation and processing techniques have been developed to reduce or eliminate voids and delamination. Both BMIs and polyimides have traditionally exhibited higher moisture absorption and lower toughness values than CEs and epoxies, but significant progress has been made in recent years to create tougher formulations, and BMIs are now touted as having better resistance to fluid ingression than epoxies. Increased use of BMI is being driven not just by tooling and applications where service temperatures exceed 177°C, but also by the increasing use of composites in structures that need improved hot/wet and open hole compression (OHC) performance at moderate temperatures, e.g., 80°C to 120°C. This is the reason behind much of its use on the F-35 Lightning II fighter jet, enabling damage-tolerant structures at lower mass vs. epoxy."
     
  11. ferris

    ferris Super OPE Member

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  12. SOS Ridgerider

    SOS Ridgerider Man of many names

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    I see this thread has been resurrected. Nice!

    I have used both of my carbon bars a little bit by now, and they do just fine. I’ve had a few inquiries if I can make them for other people too, so I’m looking for someone with a mill, who can help me out with cutting them.

    In all honesty, the stiffness of the bar depends a little on what bar you start out with.

    The 32” GB bar I got from @Jon1212 was quite a bit stiffer, and nicer quality, than the cheap Laser bar I used for the 36” project. I never got around to doing the stiffness tests, but it’s clear that the Laser bar is more whippy than the GB.

    Going forward, if I can make more, I’ll probably start with Oregon PowerMatch bars. They are consistent quality, tried and true, and available anywhere.

    I’m sure there are many ways to make them better than what I’ve done, but they’re working very well for a hack like me. I haven’t used either of the 32”-36” for felling yet, so it’s all been bucking cuts and play, and the flex doesn’t bother me. My RW Oregon 34” bar isn’t any less whippy, for that matter.

    Jon’s idea was to make a true homemade reduced weight bar, which he did a great job with. I took it one step further, and incorporated a few tools that most people don’t have in their homes, although my buddy does. Lol

    It would be cool to see someone take this further, and really engineer it, even though at that point we’re getting further and further away from homemade.

    I see the last posts address the concern about temperature, and the epoxy’s ability to handle it. In my experience there hasn’t been any issues with the epoxy. At all. I’ve done some long cuts with them, and many in a row. No sign of any stress or softening anywhere. The saw porters use the same epoxy I used, inside the jugs, to get the numbers where they want them. I have the feeling a jug gets at least as warm as a bar under operation. Lol

    This is probably the longest post I’ve ever written. Good Lawd!!!
     
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  13. smokey7

    smokey7 Pinnacle OPE Member

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    I do feel like there is better options for filler material then reg old JB weld. There are some industrial epoxies that are just silly for thermal resistance and strength. Also should be said that those epoxies are probanly somewhat difficult to find or to find in a size/volume to make it a option for oyr application. West system epoxies are very strong redily available and lots of options for curing times strengths and colors.
     
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  14. SOS Ridgerider

    SOS Ridgerider Man of many names

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    I agree. I'm sure there is something better. I still have the stuff from my old post in the fridge, and when the time is right I'll try it.
     
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  15. mettee

    mettee Super OPE Member

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    Let me see if I can make sense of this, with my lack of coffee this am...

    The jb weld is an outstanding solution, and SOS is right...it handles the heat just fine.

    Where I go with that is that jb weld is heavier, and far less rigid than it could be if it was carbon fiber bonded to carbon fiber, and there was very little resin as it would be normally cured and vacuumed down(this sucks the extra into a cotton like mat).

    So if say, we use spread tow fiber, and lay them up in the bar in a way that is to reduce flex, and cure it that way, you form essentially two pieces the bar itself, and the carbon. I feel like the middle carbon layer is crucial in adding the reduced flex requirement. The epoxy isn't helping with that it's only holding in the carbon. If we could get it to take on a dual role(replace with carbon bonded to the other carbon) that would rock!
     
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  16. mettee

    mettee Super OPE Member

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    Pre-preg?
     
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  17. mettee

    mettee Super OPE Member

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    I'm going to draw a bar up in solid works and make some cuts in it. I can set the material to chromoly and check compressive force along with several other forces.

    SOS, if you cut another bar I can tell you to avoid the square corners if possible. Even just a 1" corner radius would be better. I can explain more later, but I think you know what I'm getting at.
     
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  18. mettee

    mettee Super OPE Member

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    Depending on the thickness of the bar, it's looking like there could be between 15 and 20 layers of fiber. That is outstanding number wise for strength.

    Ill run that piece alone just for strength and see what it puts out.


    ETA: The carbon in the appropriate thickness with a high modulus is approximately 10% more "stiff" than the steel counterpart. Not comparing strength here.

    So if it is done right, this would yield a bar at least as strong as it was prior to being milled. But actually stronger :)
     
    Last edited: Oct 12, 2018
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  19. KiwiBro

    KiwiBro Pinnacle OPE Member

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    I wonder how much of the heat-sink qualities of the steel bars are factored into the design of the saws. Too much epoxy/CF and how does the saw or bar rails dissipate heat fast enough to avoid damage?
     
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  20. mettee

    mettee Super OPE Member

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    [​IMG]

    30" bar in Chromo to start
     
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