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 Post subject: Re: Carbon Fiber Frame?
PostPosted: May 11, 2016, 10:39 am 
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3 layers of uni laid up would be stronger than the same in a weave as there is a reduction of force between the crimps and you need more resin with a weave resulting in less carbon. In by doing so, you rely more on the strength of the epoxy.

weave strands are only strong in the direction that run. During layup, if strands are not held tightly together, they will loose strength in that direction.

http://www.asminternational.org/documen ... hapter.pdf

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: May 11, 2016, 10:58 am 
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But the obvious corollary is that since unidirectional fibres are strong in only one direction, you need twice as many layers if you want the composite to be equally strong/stiff in all directions.


I suppose that should be compared to the twice as many layers to make it as strong in any direction at all using woven material. Considering the varying weights of the materials and also that the unidirectional materials come stacked in multiple layers, I'm having a hard time really following this logic. It's all about straw men with you.

Another problem with the woven materials is that half the thread come to an early end on the sides of the fabric. You have to overlap those edges or provide another layer to cross those seams. If you overlap the layers that puts a flaw in the material where other layers have to cross that bump. When I built samples it was possible to get them to fail in that area. Making choices about this is just another issue in determining an appropriate stackup.

I'll clarify an earlier comment about cars and marketing. It is seldom an issue in a car what to do about 10 Kilograms. You don't want it to be heavy, but typically in competition cars there are reasonable minimum weights and it would matter less in a street car. Typically you can make tradeoffs somewhere.

If you look at airplanes they are much more at the mercy of physics than marketing. It's a more honest endeavor. An example would be Porsche deciding to use their decades of experience with air cooled engines to build an aviation power plant for light airplanes. After an effort in 10s of millions of dollars, on top of all their other existing experience and production abilities - they failed by 10 kilograms and in fact never sold a single unit. This compared to engines designed in the 1940's-1950's.

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: May 11, 2016, 12:22 pm 
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horizonjob wrote:
I'll clarify an earlier comment about cars and marketing. It is seldom an issue in a car what to do about 10 Kilograms. You don't want it to be heavy, but typically in competition cars there are reasonable minimum weights and it would matter less in a street car. Typically you can make tradeoffs somewhere.


Yes, I agree.

The 'seldom' is in F1 or high-end aerospace, where you're chasing the ultimate performance pretty much money-no-object and where, yes, you'll want to use unidirectional fibres wherever you can determine the direction and magnitudes of loads accurately enough for it to be worthwhile.

For the rest of us, it's a whole lot more sensible to accept a slightly sub-optimal design in the interests of cost and ease of construction. Which means, once again, woven fabrics predominate.


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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 1, 2016, 9:58 pm 
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Hands down, best thread I have enjoyed reading so far in the Locostusa forums :cheers: i microwaved some :lurking: came back and now you guys are all nice to each other damn! :whip: I AM CANADIAN... (Commercial) I will add, that anyone that has had an opportunity to discuss any forms of Carbon Fibre work with any retired, or unemployed Engineers that have worked in F1, def deserves a listen to. Have watched and obsessed over that sport for decades... I do think that (IMO) 'how rigid my frame is - look at the numbers' has def become a common theme here that I think is overkill, but wdik? I am still debating what avenue to take on my first build. Westfield, Locost, 442 - the list. :shock:


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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 1, 2016, 10:05 pm 
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Sam_68 wrote:
mjalaly wrote:
...we just learn how not to build cars from guys on your side of the pond

You must be slow learners, given your global dominance of race and sports car manufacture (not).

Remind me how many US Formula 1 manufacturers there are? I've lost count... :lol:


There is 1 team... HAAS... Has a lot of Ferrari in it tho. Just say'n :BDH:


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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 1, 2016, 10:43 pm 
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thrill21 wrote:
I AM CANADIAN... (Commercial)

Well hopefully trump will let you visit :D

thrill21 wrote:
I will add, that anyone that has had an opportunity to discuss any forms of Carbon Fibre work with any retired, or unemployed Engineers that have worked in F1, def deserves a listen to. Have watched and obsessed over that sport for decades... I do think that (IMO) 'how rigid my frame is - look at the numbers' has def become a common theme here that I think is overkill, but wdik?


No matter how stiff a chassis is, it is only as good as the suspension design and the tons of other factors. Lots to worry about.

You can build the most awesome thing in the world but at some point, an 80yr old man in a crx is probably going kick your butt on the track... don't ask me how I know.


thrill21 wrote:
I am still debating what avenue to take on my first build. Westfield, Locost, 442 - the list. :shock:


Whatever will make you smile at the end of the day.

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 2, 2016, 2:41 am 
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mjalaly wrote:
You can build the most awesome thing in the world but at some point, an 80yr old man in a crx is probably going kick your butt on the track...


That's a sig-line worthy snippet for sure. :cheers:

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 2, 2016, 3:13 am 
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mjalaly wrote:
No matter how stiff a chassis is, it is only as good as the suspension design and the tons of other factors.


Can't argue with that!

And it's amazing how well most traditional spaceframes work, despite having stiffness figures that are only slightly better than boiled spaghetti.

...but it doesn't stop you trying to get every factor as good as you can. Give up on that, any we might as well go back to building Austin Sevens. :)


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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 29, 2016, 10:47 am 
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Zoombie Thread just for page 11 bookmark

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 29, 2016, 11:50 pm 
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21 pages and so much "spirited discussion", this has officially become a must do for me. :cheers:
I have the basic concept figured out need to begin gathering parts and material.

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 30, 2016, 8:14 am 
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RichardSIA wrote:
21 pages and so much "spirited discussion", this has officially become a must do for me. :cheers:
I have the basic concept figured out need to begin gathering parts and material.


Just buy one of these and make a tube chassis.
https://3dprint.com/53440/x-winder-filament-winder/

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 Post subject: Re: Carbon Fiber Frame?
PostPosted: June 30, 2016, 10:58 pm 
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I'm looking at basically a four box main structure, two fairly tall box sills and the center tunnel surrounded by a larger box that is the tub and scuttles.
Major questions now are front and rear space-frames for suspension and drive-train.
In that regard I need to decide just how far forward to go with the CF structure.
I think my basic design is sturdy enough to work fine even in plywood so CF should be overkill.

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