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will rant for food
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Discussion Starter · #1 ·
Via sweating out the aftermath of many failures, and with the help of many people, I'm now able to do this kinda bladder inflation molded bizniss, rough cut and unpolished as it may be at the moment:

IMG_20140421_094029.jpg

Don't know how many times I failed to produce this sort of result. No idea.

Once I get a proper 3 axis CNC mill, I should be able to prototype these very cost effectively. Now to work out more of the bugs.
 

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Nemophilist
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Damn dude!

About time you got off your duff and got some of these made!

I'm UTTERLY TOTALLY KIDDING of course. You are a testament to dogged determination, if nothing else. I somehow knew you would figure it out eventually, and I am sure you will keep figuring it out for a long time to come as you refine your process. If anyone else has been thinking about doing this, you better be mentally tough enough to keep your head down and your eye on the prize. It's a LOOOONG climb!

Mucho kudos, Amigo!
 

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Great to get that milestone. Tick off another box. Keep going.

I know that this is a lug, but my traditional heritage would have me wanting to sort of make the sockets 'pointy'. Its early days to ask this question, but can that be done from a lug like this? Carbon Tubes bonded in, instead of filler as you would use with steel. I just like the art work....

Eric
 

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will rant for food
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Discussion Starter · #4 ·
TrailMaker - I know you kid, but there's some truth to it even if unintentional. Fell on my ass a bunch!

Eric - I follow what you mean, and I think those frames are timeless. The answer is yes it could be done - diamond edged hole saw and careful manual cleanup. I want to have lots of less ambitious trials done before I take a stab at that style.
 

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will rant for food
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Discussion Starter · #6 ·
That's looking great. Any more pics of the molds and bladders?
Some attached. In order:

1) A "2D" or lay-flat bladder.
2) Wet sanding after polyester sealing the milled area of the MDF.
3) Put on an epoxy topcoat for a bit of shine, it's not evenly applied as would be had with a proper clearcoat. EDIT - I was SUPER pleased to see the mallard plumage effect after polishing and epoxy coat. I think the iridescent effects of UD fiber is way more interesting to look at in person than twill fiber patterns.

I'm not actually using this part as I damaged the mold in use, wanted to just get a reasonable idea how a part might turn out once I learn more about the foibles of high pressure mold design.

For starters, not going to use MDF. I bent some Uni-Strut reinforcement and dimpled the crap out of the exterior of the mold.

I think one reason that this topic is not better documented the way metal working is pretty well documented is maybe because it is dangerous if disrespected. I think I remember calculating after damaging the mold that there was a near half-ton parting force between the mold halves at a "mere" 25 psi.

IMG_20140410_125259.jpg IMG_20140412_185140.jpg IMG_20140422_235429.jpg
 

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Nicely done!

I have another CF frame planned for this spring or summer, along with some ideas of my own. Will share when I am under way.

And by the way, its alway a little sweeter when it works after many failures.
 

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will rant for food
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Discussion Starter · #8 ·
Hah, definitely. Can't appreciate the good without the bad. Now that I've had some time to stop being pleased with myself, I gave the part a thorough inspection and judged a whole BUNCH of reasons on why it's not ready for prime time. That stuff is really difficult to photograph with the equipment I have.
 

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would rather be ruined
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drew

i was trying to figure out if the radius finished edges were a feature but now i ve seen the tool it makes sense obviously its a front triangle not just a head lug but same system is used

I have attached a picture to flikr for ya drew this is how we mold a head tube with bearing seats and everything to size

i will try to crop down another image to show you the overwrap and bonded joint area where the tubes get glued to the lugs


https://www.flickr.com/photos/compositepro/14034619351/

one of the reasons i dont really show and tell with bladders is that pressure is dangerous and you get some guys trying to hit 200psi because they heard somewhere thats what company A does it at and then they heat it up to 90 degrees
well it goes without saying someone will say i saw it on the internet
 

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will rant for food
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Discussion Starter · #11 ·
one of the reasons i dont really show and tell with bladders is that pressure is dangerous and you get some guys trying to hit 200psi because they heard somewhere thats what company A does it at and then they heat it up to 90 degrees
well it goes without saying someone will say i saw it on the internet
Yeah, that's kinda what I'm driving at. The super high pressure is so whatever small voids you leave during even careful layup, the air bubbles will *dissolve*, right?

Well - you also need, like, a full size truck to squish those mold pieces together.

And all I drive are sedans ;)

Which kinda bums me out - I was initially so bummed out about how little doco there was on the net about this stuff, and I see it might be for a legitimate reason. My hatred for censorship and my appreciation for safety are butting heads here.

ktm520: the raw material was a prepreg that accepts 180 F to 240 F, I used 200.
 

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would rather be ruined
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Yeah, that's kinda what I'm driving at. The super high pressure is so whatever small voids you leave during even careful layup, the air bubbles will *dissolve*, right?

Well - you also need, like, a full size truck to squish those mold pieces together.

And all I drive are sedans ;)

Which kinda bums me out - I was initially so bummed out about how little doco there was on the net about this stuff, and I see it might be for a legitimate reason. My hatred for censorship and my appreciation for safety are butting heads here.

ktm520: the raw material was a prepreg that accepts 180 F to 240 F, I used 200.
Well high psi isn't a prerequisite I know we have solved problems for factories where too high a pressure was assumed to be beneficial frames were light on resin and delaminating even demoulding them

Using a bladder and incorrect pressure you can trap and lock off air in the laminate it wont escape or boil off any volatiles(older resin systems) as it would in an autoclave

Do you know about your resin cure cycle through to its tg at some point it will have a lower cp (more fluid) this usually happens before gel though not always hence you can time the bladder pressure to ramp at certain points this means you can run less psi throughout the process

Don't rule out sticking a vacuum line in their just as a further experiment
 

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will rant for food
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Discussion Starter · #13 ·
Well high psi isn't a prerequisite I know we have solved problems for factories where too high a pressure was assumed to be beneficial frames were light on resin and delaminating even demoulding them

Using a bladder and incorrect pressure you can trap and lock off air in the laminate it wont escape or boil off any volatiles(older resin systems) as it would in an autoclave

Do you know about your resin cure cycle through to its tg at some point it will have a lower cp (more fluid) this usually happens before gel though not always hence you can time the bladder pressure to ramp at certain points this means you can run less psi throughout the process

Don't rule out sticking a vacuum line in their just as a further experiment
I have some rather detailed docs on the prepreg resin I'm using, unfortunately I don't have a heating system (yet) that can go into the sort of detail described.

Also, what you're saying is consistent with what I saw during my first pressurization test with this mold (which failed), the resin viscosity at time of demold was very thin, sort of like snot. I had to laugh at myself after the fact, I wasn't using a thermocouple or anything, just a few reference plies that I checked on intermittently - yeah well, MDF is wood and glue and therefore has a stupidly low thermal conductivity, I basically interrupted the first molding's attempt when the resin was pre-gel state.

So yeah. Thermocouples. Duh.

I've been kicking a few other ideas around in my head to possibly increase the safety factor. Nothing definite yet, and at the moment more focused on getting a halfway decent mill running. With this mold, the machining costs alone... if I were to make say just 20 prototypes in house, I'd break even super fast on a mill heavy enough for high speed non-metals machining.
 

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will rant for food
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Discussion Starter · #15 ·
Interesting that the MDF mold will withstand elevated cures.
Forgot that detail: it didn't. The parting faces of the mold were not touching and as such I can't use this cured part (among other reasons).

There was 2-3mm of curl away from plane on each face at the edges.
 

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Love what you're doing. Keep up the good work.

If you're not going to use mdf then what next? Big lumps of alu are not cheap. For that head-tube area a mold could be made out of sectioned pipe, mitered, welded and flanged. Miter all the pipes, weld them together, cut in half, weld on flanges so you can bolt back together, bolt back together and then bore in from each open end to your desired dimensions.
 

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will rant for food
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Discussion Starter · #17 ·
Love what you're doing. Keep up the good work.

If you're not going to use mdf then what next?
Either a frangible mold design, or something else I haven't even tested yet and people who I mention it to thinks I'm crazy (but my dad doesn't, and he's a nutcase about plastics).

Jury's out on that subject.
 

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Nemophilist
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How'bout cement?
 

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How'bout cement?
Mortar or concrete found in a ready mix bag at your home center ranges from 3000-5000psi compressive strength. Plenty to resist the parting pressure but you'd need to bind the halves with some A36 (or better) steel shapes and high-strength bolting. Unistrut is not the answer as you found.
You might need some sort of interior metal sleeving as I'm not sure you'd get repeatable results out of the mortar alone. I think the sharp corners and creases would break free because they are thin and brittle.
 
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