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PostPosted: Mon Oct 31, 2011 5:36 pm 
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Why do you say that?

Cyfac uses Kevlar as well in their lug/shell wraps.


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Posted: Mon Oct 31, 2011 5:36 pm 


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PostPosted: Mon Oct 31, 2011 5:48 pm 
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Just because some does it (especially not someone who makes bikes) it does not mean that it makes sense. A lug on a bicycle frame is nothing which has demands concerning impact, and the failure behaviour is good even without a crack arrestor like aramid fibres. So why shoud one use a fibre that can not handle compressive strength, has problems with the fibre-matrix-bonding (especially if not dried very accurate) and has little stiffness, so it does not get that much load? If you want to get a designated fail safe behaviour on bike parts, you should add additional load paths and a layup which shows inter fibre fracture first in the right ply and early enough before the first fibre fracture. That way you do not affect weight or stiffness as much as if you use aramid fibres, getting a fail safe behaviour at least as good.

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PostPosted: Tue Nov 01, 2011 1:09 pm 
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Kevlar is good for clamping zones, ie seat posts

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PostPosted: Tue Nov 01, 2011 2:18 pm 
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Carbon Cowboy
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Well, about the kevlar reinforcements - for my PT3 frame I didn't used it much (around 20g for the whole frame), mostly on the areas where I drill the holes. Now I use it for the clamping area (seatposts) and sometimes also for saddles..
I already have the "laminat-plan" for my next frame project and I'll use it on some areas - where I'll have to drill holes, and it really isn't a lot of kevlar,..the rest will be of course made with carbon fibre,..this time the "beauty look" will be in UD. Once I'll have the mould I'll probably make also one in 3K, will see..unfortunately I have to study :mrgreen: and it will take some more time before I'll be able to continue with the work.

Otherwise I'll make the chainstays on my PT4 frame monocoque, that's also one more reason why it will take me some more time to finish the moulds,..but it will be worth the extra work :mrgreen:

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PostPosted: Tue Nov 01, 2011 4:25 pm 
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gumgardner wrote:
Kevlar is good for clamping zones, ie seat posts


No it isn't. Clamping a seat post is like having a tube under pressure from outside. The result is compression stress in the circumferential direction of the tube. If you have the Aramid in the same direction, it will cause microbuckling, so the fibre is defective.
If you it in the axial direction, you do not get much effect. It does not get damaged that much by notches, but this effect is not that much bigger if you have an additional ply of carbon fibre. Though the CF will cause a better distribution of the high contact pressures, because of its much higher stiffness. So there is no reason to put some Aramide there, except marking the area where clamping is allowed.

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PostPosted: Tue Nov 01, 2011 7:11 pm 
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Mr. Hyde - one question for you.
What do you think about using carbon/kevlar on the areas where you drill holes. I had quite a lot frames (Cipollini etc.,..) in my hands that are using it around that areas,..
But once again, it's about some very small amounts of carbon/kevlar and it isn't "replacing" carbon, but is there only as an additional reinforcement.

And if I remember right you also started a frame project? How is it going?

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PostPosted: Tue Nov 01, 2011 8:28 pm 
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In aereas where you are drilling holes it might be useful as a crack stoppper. But think about the general higher stress in this area because of the notch (around 3 times as high!). There you need additional strength, and you achieve that in the lightest way by adding CF, not AF (if the rest of the lamina is CF). Of course I see that you are not replacing CF by AF, but even adding AF has nearly no effect in an bicycle frame, so you can even save the 20g or what, the costs for an additional fabric in the workshop and the effort having it processed properly (the complex drying, the bad cutting).
You also can mould all holes, that's way more effective than adding AF or CF.

My bike (I don't call that project, because it does not really match the definition of a project since I am building more than one bicycle frame in my life :wink: ) got a bit neglected while building the wind tunnel model, and now I have an advanced design project about a undercarriage of an airplane, so it does not happen that much. But I startet building a frame with standard fibres to get a little expercience with the specialities planned for the light frame, have a look at the blog ;-).

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PostPosted: Sat Nov 05, 2011 12:17 pm 
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Mr. Hyde - keep the good work going :thumbup:



Some news about my work - about the saddle/seatpost combos.

I worked on a new prototype that had only 2 carbon wings instead of 3 (the carbon reinforcements). With 2 wings it's even a bit lighter and also a bit more comfortable. Here is just the 3-wing reinforcement from my PT3 frame:
Image

For some future combos I'll most probably use that method with 2 wings (like on the front area there will be only one wing on the rear area of the saddle)...will send some more photos soon, I send that combo on a test and should get it back in a week. Anyway, it's only a bit improved, nothing special, but just to let you know. Also the weight savings are minimal: 3-5g, depends on the seatback.

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PostPosted: Mon Nov 07, 2011 3:35 am 
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I've been looking at your stuff and it is very inspiring. I wonder how did you learn all this? Through school? Books? I study mechanical engineering and only a small part of the curriculum is dedicated to composites.

Any how, would you be able to point me in the right direction to get started?

keep it up!


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PostPosted: Mon Nov 07, 2011 4:59 am 
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Berk, all very good stuff indeed.

Re the saddle, my vote goes to 2-wing, same as your decision. The lateral flexing forces are not that great to require any more. One drawback to this design (other than adjustability issue but there's no way around that) is the fact that the seat mast goes right into the center of the seat and takes out any suspension effect of saddle rails. Given the two wings are going to add a bit of weight, it MIGHT be useful to think about alternative structures that provide a bit more "give".

My manufacturer doesn't currently focus on seats etc, but I do have some thoughts in that regard.

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PostPosted: Tue Nov 08, 2011 12:04 am 
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Carbon Cowboy
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surlaplaque wrote:
I've been looking at your stuff and it is very inspiring. I wonder how did you learn all this? Through school? Books? I study mechanical engineering and only a small part of the curriculum is dedicated to composites.

Any how, would you be able to point me in the right direction to get started?

keep it up!


First of all thanks!
Sure not through school, everything is just pure experimenting and collecting as much informations as possible. I have that luck that when I started with all this I get in contact with some people who work in some of our hi-tech composite industry. I get some material and slowly started working with it. Before that I made rocket fuels and of course also complete rockets. I made the tubes in quite similar principe and also working with some dangerous chemicals wasn't something new for me. Then I made a lot experiments. Really a lot. And slowly started with some bigger projects. Of course I was going step by step,..and I'm still going step by step,..and each step is better, improved,..

During all that time I get a lot of important informations, I also learned a lot. And after my third frame I'm prepared to do an even better frame. Something that will be really on a high level.,..I'll have to prepare more than 120 pieces of carbon for my PT4-NANO frame, also the materials that I use are now one of the most advanced. And as I mentioned, I get in contact with some people here in Slovenia who are working in the composite industry. We have quite a lot hi-tech composite companies (Akrapovič, Elan, PipiStrel, Seaway, etc.,..)


elviento wrote:
Berk, all very good stuff indeed.

Re the saddle, my vote goes to 2-wing, same as your decision. The lateral flexing forces are not that great to require any more. One drawback to this design (other than adjustability issue but there's no way around that) is the fact that the seat mast goes right into the center of the seat and takes out any suspension effect of saddle rails. Given the two wings are going to add a bit of weight, it MIGHT be useful to think about alternative structures that provide a bit more "give".

My manufacturer doesn't currently focus on seats etc, but I do have some thoughts in that regard.


Thanks.
It would sure be good if I would make it with some suspension, but then it wouldn't be that light and also the procedure would be much more complicated (already my procedure is quite complicated - carbon wings). But I'll make the combos now with only 2 wings, it should be a bit more comfortable. I rode with my PT3 for quite a lot kilometers without any probelms,..but it's true that I'm really quite used to a cycling saddle :mrgreen:

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PostPosted: Tue Nov 08, 2011 12:47 am 
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I feel I should chime in regarding elviento's concerns about the comfort of these saddle/post combos. I did 9000 km this season on one of them and intend to use nothing else in the future! Try it and see for yourself! If the shape of the saddle suits (you can choose between several) and provided you use good quality bibs, there really shouldn't be a problem. My longest ride this year was 270 km and it wasn't my butt that complained the loudest...
If Jure was to complicate the construction to increase its comfort, the certain significant weight gain and loss of aesthetic appeal would IMHO not be worth it.


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PostPosted: Wed Nov 09, 2011 11:27 pm 
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@giantdale
Thanks, glad to hear that!


And some new photos froma a seatpost.
It's 31.6mm x 370mm and 150g.

Image

It will be for MTB and the other parts are from FRM - a friend of mine provided me some nice parts and I really like them!

Just one more photo from the seatpost with a saddle. You can see also carbon/kevlar in the clamping area, and as you can see it's with gloss finish and white graphics:

Image

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PostPosted: Tue Nov 15, 2011 1:44 am 
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UD combo with AX Phoenix saddle shape:

Image


And some news from my side,... I already wrote on Facebook and will share with you also here.
In the past few days I just get a new idea, how to make a custom made frame that would look like a monocoque frame - wihout any visible edges and with smooth lines on the joints. It's a procedure where I would need just one set of moulds for a custom frame, and I could make a custom standard road frame, a MTB frame or even an aero/TT frame with some aero tubing!

Of course it's my secret how it will be made,..because I need a MTB bike I'll most probably first make a MTB frame with this procedure, but it may take me some more time before I start with the work, but just to let you know that I'm working on my future projects,..

At this moment I'm working quite a lot on some projects and hopefully I'll be soon able to show some more products. My head is ful of inovations and just can't wait to start with all those projects! Today it's also a very good day for me, because someone from a hi-tech company from Slovenia contacted me, and I was really very surprised...and in the future I'll for sure keep working with carbon, hopefully also in the carbon industry, I'll give my best :thumbup:



Here just some more photos, to show you the background of all those carbon parts, probably it's interesting for some of you:

Image

DANGEROUS chemicals - good equipment is VERY IMPORTANT (good mask, gloves and other protection, also a good ventilation and workshop)...

Image


Anyway, as soon as I'll have some news I'll let you know. Thanks for your attention :thumbup:

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Posted: Tue Nov 15, 2011 1:44 am 


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PostPosted: Tue Nov 15, 2011 2:11 am 
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I did ask you way back about those integrated saddle combos with ax saddle shape. What is the weight and size of this one?

I am curious of MTB frame. Will wait for some more progress. Good luck in the meantime.

Chris.

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