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  1. #1
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    Carbon DH frame DIY build thread (updated with pics)

    As promised, a thread about my little DIY DH frame project.

    A few pics, showing the mold parts, the jig, and the foam core of the main frame.

    This shows the first of 3 builds. Each to be slightly different in suspension design.

    The other 2 foam cores are also ready to go.

    The fiber and the epoxy arrived a couple of days ago, so when my job allows, time will be spent on this.


    Magura
    Last edited by Mr.Magura; 07-06-2011 at 11:18 AM.

  2. #2
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    very cool!

  3. #3
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    HI!

    Can you put the BOM of this project? (is that Rohacell IG?)
    The U part (with 3 holes) is it for Shockmount?
    Are you going to use Aluminium insert for BB/Main bearing/Headset?
    Also, I don't know if you are aware, but this guys over here www-8020.net (don't mind publicity! I donīt work for THEM nor I do have Comission!), but nice JIGs can be made out of it.


    GREAT WORK - in portuguese: "EXCELENTE TRABALHO!"


    PS: don't get me wrong, but it's a bit IBISish! I would like to have some time at work to do something in those lines!...

  4. #4
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    Quote Originally Posted by Tkul View Post
    HI!

    Can you put the BOM of this project? (is that Rohacell IG?)
    The U part (with 3 holes) is it for Shockmount?
    Are you going to use Aluminium insert for BB/Main bearing/Headset?
    Also, I don't know if you are aware, but this guys over here www-8020.net (don't mind publicity! I donīt work for THEM nor I do have Comission!), but nice JIGs can be made out of it.


    GREAT WORK - in portuguese: "EXCELENTE TRABALHO!"


    PS: don't get me wrong, but it's a bit IBISish! I would like to have some time at work to do something in those lines!...
    The BOM for the front triangle would be along these lines:

    A few kg worth of PTFE for the mold parts.
    A block of PS foam (Rohacell has too many disadvantages, though it sure is stronger).
    Approx. 6m2 300g/m2 unidirectional carbon
    1m2 woven 160g/m2 carbon
    1m2 465g/m2 ballistic woven Kevlar
    Approx. 100m 3K carbon rowing
    A 7075T6 linkage mount
    Approx. 2.5kg of epoxy

    The U-part is for the linkage plate pivot.

    All the bearings will be mounted directly in the carbon.

    Yeah, the 8020 system is good for jigs, but I prefer to have a flat surface as a reference point, as this is a bit more complicated than just setting up tubes in the right positions.
    By using a plate, I have my zero in close vicinity at most points.
    I did though consider something like the 8020 system in the beginning, but couldn't think my way out of the lack of a reference plane in the setup phase.

    I just took a look at the Ibis, and sure you're right, the front half looks a bit like the Mojo.
    It will however not bear much of a resemblance once the fiber has been added.


    Magura


    EDIT:

    What are you doing for a living, since you have such possibilities?

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    Looks like a great project! I cant wait to see it progress.

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    Quote Originally Posted by j_raquet View Post
    Looks like a great project! I cant wait to see it progress.
    Well, I hope to have the first front end ready within 2 weeks. The linkage and the rear will take another couple of weeks I suppose (if work permits spending the time).



    Magura

  7. #7
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    Way cool, subscribed. I want to build a full suss fat bike before summer is out. This will be inspiring!

  8. #8
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    So, a quick rundown of the details.

    The bottom bracket is the dimensions of a Shimano external type, but all of it is internal, so the bottom bracket is pretty wide. Like 105mm as I recall.
    All bearings are to be glued directly in the frame, so no alloy bearing cups.
    I aim for around 4 to 4.5kg for the frame without rear shock.
    Adjustable head angle, BB height, suspension compression curve, chain-stay length, and so forth by a few different rear ends.


    My target for this frame, is to make a hard wearing, versatile, and stiff DH frame.
    It is also my intentions to keep the man hours down, in order to be able to make a few for experiments.
    As I wrote initially, the first batch consists of 3 frames, but I expect to make a few a year in the future.
    Having said that, I guess I better point out that they are not for sale, before I get the usual lecture about that "I" am a company or manufacturer or whatever the clown in question can wring from his imagination
    I do this for fun and education, and that's it!
    That it's posted here, is to inspire others to take on a project like this themselves (and due to a few requests).


    Magura

  9. #9
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    Thank you for sharing this project.

    Are you making molds out of fiberglass to layup the carbon?

    What is your layup schedule going to be?

  10. #10
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    Quote Originally Posted by shirk View Post
    Thank you for sharing this project.

    Are you making molds out of fiberglass to layup the carbon?

    What is your layup schedule going to be?

    I am going to make them moldless, using the foam core as positive mold. Hence the setup in the photos, as I need to keep everything in position till the fiber is applied and the vacuum is up.

    What is a layup schedule? You'll have to forgive my ignorance, but I'm not a native English speaker, and the term is not easy to make sense of from a dictionary


    Magura

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    Layup schedule refers to the number of layers and the orientation as well as the type of cloth used.

  12. #12
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    Quote Originally Posted by Mr.Magura View Post
    I am going to make them moldless, using the foam core as positive mold.
    I take it that means the foam will be staying within the finished frame? You'll have the quietest, strongest bike on the planet! Keep us posted please

  13. #13
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    Subbed!
    My Bike: http://forums.mtbr.com/showpost.php?...3&postcount=49

    On-One Whippet 650b XC machine

  14. #14
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    I'm impressed. The frame plug is very well made. Why not use it to make a cavity mold for the composite frame, and use inflated bladders to compact the resin/fiber matrix?

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    Quote Originally Posted by Fix the Spade View Post
    I take it that means the foam will be staying within the finished frame? You'll have the quietest, strongest bike on the planet! Keep us posted please
    AFAIK you can remove the foam by disolving it with acetone.


    Quote Originally Posted by forwardcomponents View Post
    I'm impressed. The frame plug is very well made. Why not use it to make a cavity mold for the composite frame, and use inflated bladders to compact the resin/fiber matrix?
    how does one do the layup using a female mold and pressure bladders?

    to the OP: great work. I would definitely like to do something similar.

  16. #16
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    Quote Originally Posted by sonic reducer View Post
    AFAIK you can remove the foam by disolving it with acetone.

    how does one do the layup using a female mold and pressure bladders?

    to the OP: great work. I would definitely like to do something similar.
    Bladder molding frames of this nature normally require custom bladders which are costly to make for prototype runs. They are also not perfect out of the box, often requiring changes in the bladder design to allow for layer build up in specific areas, with bagging external dimensions will change when layer buildup is changed.

    Bladder materials are either latex or nylon, and are often used in prepreg layup,although I have bladder molded hollow parts using wet layup. The viscoscity of a wet layup and bladder molding on frame would require perfect sealing on A and B mold halves or else as the bladder pressure increases it can force out resin.... that is unless the part is layed up damp, and resin is pulled through the mold. For this to happen the mold parting halves must be perfectly sealed or else when you pull vac to draw resin through the mold it will pull air through parting line.

    Moral of the story, bladder molding is best left to prepreg on parts which have multiple unique shutoffs on parting line... like seat tube, and head tube.

    His method is sound for making short run prototypes, and if going production an aluminum tool, bladder, prepreg, and a heated platen press would be used.

    Josh

  17. #17
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    Interesting project. I made something remotely similar when I made a carbon fiber neck over an obeche core for a headless bass guitar. Looking forward for more pics and story.
    Marko

  18. #18
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    Quote Originally Posted by MPU View Post
    Interesting project. I made something remotely similar when I made a carbon fiber neck over an obeche core for a headless bass guitar. Looking forward for more pics and story.
    Marko
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  19. #19
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    Been waiting for you to start a building thead after reading about this here bike in the "DH Carbon" thread, Magura! Looks promising for sure. Nice work. Eager to see the linkage designs you adopt for testing.

  20. #20
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    Quote Originally Posted by shirk View Post
    Layup schedule refers to the number of layers and the orientation as well as the type of cloth used.
    Thanks for the clarification

    The number of layers differs a lot depending where on the frame you look. I have an entire A4 sheet of notes for this (handwriting), so it would be quite a task to post it.
    I am going to use mainly 300g/m2 UD carbon. 0, 20, and 45 degrees to the axis of the tubes.
    I will add carbon multi wall nanotubes to the epoxy (5% by weight), to enhance the properties.
    In areas of potential hard impact, I will use ballistic weave 463g/m2 Kevlar.


    Magura

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    Quote Originally Posted by Fix the Spade View Post
    I take it that means the foam will be staying within the finished frame? You'll have the quietest, strongest bike on the planet! Keep us posted please
    Yes, the foam core will stay in the frame, as the 120g weight penalty seems to be well worth the benefits. I did it the same way when I made a road fork of carbon 15 years ago, and have seen no ill effects of that approach.

    I am not sure there is much strength to gain from leaving the foam core in there, but it makes for a dead silent frame, instead of the terrible noise a hollow frame makes. It also keeps water and dirt from entering the frame, which in turns keeps the bearings in the bottom bracket dry on the inside.


    Magura

  22. #22
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    Quote Originally Posted by sonic reducer View Post
    AFAIK you can remove the foam by disolving it with acetone.




    how does one do the layup using a female mold and pressure bladders?

    to the OP: great work. I would definitely like to do something similar.
    Thanks for the compliment.
    This is not rocket science, so just go ahead and get your feet wet.

    Yes that's right, acetone will dissolve the PS foam core if I one day will feel like making the experiment some day.

    To use female mold and bladders, a completely different approach is required. Then we are talking prepreg and custom bladders. That in itself is no big deal, as DIY custom bladders are relatively easy to make, but to cure the prepreg, you need to heat up the entire mold.
    Considering those issues, and the limited (if any) benefits it may offer, that approach is a bit overkill for a limited series.
    Also keep in mind, that I do not want more than one frame of each design, so making new molds for each design, makes for a very man hour intensive, and expensive toy.
    Like I do it now, I can make the entire frame for something like 400$.


    Magura

  23. #23
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    Quote Originally Posted by joshuagore View Post

    Moral of the story, bladder molding is best left to prepreg on parts which have multiple unique shutoffs on parting line... like seat tube, and head tube.

    His method is sound for making short run prototypes, and if going production an aluminum tool, bladder, prepreg, and a heated platen press would be used.

    Josh
    This conforms well with my experience. I have seen a few people over time, try to fight all the issues of bladder molding prototype runs. So far they have either failed, or ended up with hefty expenses, and a very limited (if any) quality increase.

    With lots of attention to design and careful processing, I can get 70% fiber content by vacuum bagging, using a closed cell foam core. That is more than good enough for something like this.
    The void count can also be kept low if done with care and attention, according to my experience.


    Magura

  24. #24
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    Todays progress was to test the batch of foam used for the core, and my new vacuum pump.

    It turned out rather good. The pump is offering a max. vacuum of 70 cm/Hg, which is quite good for something like this project.
    The foam is able to survive full vacuum from the pump, which simplifies the whole thing.

    Next step is to make tailor made vacuum bags for the project. This may sound easy, but rest assured that it is among the hard parts of this project.


    Magura

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    This looks awesome, something I'd like to do some day, but not quite yet, good luck!

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