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The advantage in CF race tubs is the stiffness and torsional rigidity it provides. The weight savings is a nice bonus, even in a F1 chassis where weight savings is a high priority.

As Cory M said, the intersection of CF tubes needs precise joinery. To fabricate such components in anticipation of all the joints required would be a complicated and expensive undertaking. Traditional welded joints are the best cost-effective solution. In the step up the evolutionary ladder there were fiberglass tubs, followed by honeycomb panels, then CF tubs. Space frame tubes are still used in sub-structures (also roll cages), but in the highest levels of racing, it's autoclaved CF sheets.

Sherwood
Old 06-21-2005, 12:37 PM
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A cool CF weight loss item I've looked into is CF axle shafts. There's a company in the UK that makes them, but not for the 911
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Old 06-21-2005, 12:43 PM
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Quote:
Originally posted by 911pcars
In the step up the evolutionary ladder there were fiberglass tubs, followed by honeycomb panels, then CF tubs.
Sherwood
Uhh -- Fiberglass tubs??? With the exception of the Lotus Elan, I don't think that there were many. Don't you mean Aluminum panelled tubs (like most Sports 2000's use)?
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Old 06-21-2005, 01:24 PM
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Sure you can make a carbon fiber tube frame.

Just don't expect the tubes to be round ....


. ...or constant profile


....or straight


Why would they be limited to those constraints?




oh, btw; apparently those guys at Porsche didn't read Pelican here, on how "stucture, under the bumper facade, isn't really needed."

Maybe it's just there for parking lot bumps.
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Old 06-21-2005, 01:25 PM
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I always wondered what the 2009 Boxster would look like...
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Old 06-21-2005, 01:43 PM
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"Uhh -- Fiberglass tubs??? With the exception of the Lotus Elan, I don't think that there were many. Don't you mean Aluminum panelled tubs (like most Sports 2000's use)?"

FG tubs were not that common. I was referring to Jim Hall's early Chaparral race cars. The 2A tube was made of laid up FG, but constructed using the same techniques as today's CF construction (vacuum formed and heat cured). The FG tub was augmented with aluminum sections. The latest Race Tech magazine has an article on composite chassis history.

Sherwood
Old 06-21-2005, 01:48 PM
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Hey Janus, ...remember when you were wanting to make clothing from carbon fiber???
Man, you got it bad.













...as if I'm any better... I read it right along with you... ')
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Old 06-21-2005, 01:58 PM
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Quote:
Originally posted by Leland Pate
Hey Janus, ...remember when you were wanting to make clothing from carbon fiber???
Man, you got it bad.
Oh man, you don't know the half of it. I've got yards of raw c/f and kevlar stacked in my basement and I just got a HPLV spray kit from Harbor Freight to spray molds and coatings. My only obstacle is that I need to figure out a venting system that will allow me to lay up c/f in my basement without blowing up the house. I would have tried it over a year ago but the folks on this board (thankfully) talked me down from the ledge and advised caution. So I am taking baby steps. Blowing up the house would suck.
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Old 06-21-2005, 02:03 PM
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There are a lot of issues using carbon fiber for anything, many of them noted here.

IMHO, the best property of metals is that they are omnidirectionally "strong." But that means you may have a lot of excess material against loads that aren't there.

With any type of fiber reinforced plastic, you have to align the fibers in each direction against a projected load. this of course has its advantages, such that if you have a load in only one plane, you don't have to use excess material for all planes, which you would by default with metal. This saves weight and space.

the only real way to build a safe 911 tub would be model it with finite element analysis and then autoclave a pre-preg carbon (carbon cloth with pre-impregnated resin) shape/mold to realize both strength and weight savings.

The cost of this could easily reach 7 figures.
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Old 06-21-2005, 02:15 PM
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Quote:
Originally posted by JanusCole
My only obstacle is that I need to figure out a venting system that will allow me to lay up c/f in my basement without blowing up the house.
Have you looked into vacuum infusion instead of wet layup? The mold are only slightly more complicated...

Last edited by JasonAndreas; 06-22-2005 at 01:33 AM..
Old 06-22-2005, 01:30 AM
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Laying up carbon fiber w/ epoxy (such as West System's ProSet) does not pose any explosion hazards that I know of.
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Old 06-22-2005, 03:12 AM
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Quote:
Originally posted by Tim Hancock
Laying up carbon fiber w/ epoxy (such as West System's ProSet) does not pose any explosion hazards that I know of.
But it smells bad. My friends complain about the smell in my shop, even though I have a nice ventilation system.

The only fire hazard I can think of would the acetone for cleanup and styrene monomer for thinning the resin.
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Old 06-22-2005, 05:12 AM
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Hey island 911 look here:

http://www.macqc.com/stock.php

These tubes ARE round
Old 06-22-2005, 06:07 AM
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Yeah, lots of applications still, for round tubes.


Thom, if you want to contain the smell better, look into VIP method, that Jason suggested. Or, start using prepregs.

. . . here's a good VIP link
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Old 06-22-2005, 07:20 AM
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Quote:
Originally posted by Tim Hancock
Laying up carbon fiber w/ epoxy (such as West System's ProSet) does not pose any explosion hazards that I know of.
My initial concerns came when I considered laying up c/f and painting it. The folks here pointed out that some paints can be explosive. But it inspired me to go to the safety section of the Fibreglast website and they said this about composite fabrication...

POLYESTER RESINS, GEL COATS, ACETONE , STYRENE, STYRENE WAX AND PVA

These are all considered flammable liquids. Each of these products has a flash point lower than 100 degrees F. This means that vapors of these products can ignite at temperatures lower than 100 degrees F if presented with a direct ignition source. The lower the flash point , the more highly flammable a material is considered to be.

Consequently, when working with any of these products, you should have plenty of fresh air and avoid all sources of ignition.


That was enough to convince me that I should proceed with caution.
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Old 06-22-2005, 08:05 AM
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anybody who wants to do this should check out Fiber Fab - a spin off co. from Amory Lovins

they can do "cheap" that is nearly as stiff as hand laid material
Old 07-30-2008, 09:34 PM
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3D Printed Track Bike Masterpiece, in Carbon and Titanium

Video: Track Bike Build With 3D Printed Lugs

revisitng an old thread - not withstanding the issues above the ability to design and then make lugs that are infinitely variable and precise geometry for tube framing is here

Last edited by micheloaks; 08-16-2013 at 03:29 PM..
Old 08-16-2013, 03:26 PM
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or something like described in this article - Automotive lightweighting with alternative materials







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Old 08-16-2013, 05:26 PM
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My old boss went to a carbon fibre frame on his bicycle...it was very light.
Within 3 months...the front tube was starting to "unwind" the fibers were separating.
I guess stones and other abrasive things were causing the problem.
He sold it...and went to a Titanium frame.
So...there is one possible problem you might run in to.
Bob
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Old 08-16-2013, 10:38 PM
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