Bruce_Dunn@mindlink.UUCP (Bruce Dunn) (02/08/91)
> gregc@cimage.com writes: > Person: Greg Cronau > > I don't even want to *think* about the number of G's on the spacecraft > when that sucker goes taunt. You'd have to make the cable out of something > resilient so that it would stretch to absorb the initial shock. > You could make the cable out of a kevlar bungee. Certainly would give a > new meaning to the concept of a "slingshot" manuever. :-) > > gregc@cimage.com Kevlar is fascinating stuff. I just acquired a spool of Kevlar fiber for tinkering purposes. It looks like pale yellow dental floss, or like polyester sewing thread. The spool that I have is loaded with a strand that has two individual thread-like fiber bundles twisted around each other. The thread is quite flexible in spite of the very high Young's modulus of the fiber (high stiffness). This is probably because the actual fibers making up the thread are extremely fine (nearly invisible if the end of a thread is frayed out), and the thread can bend by flexing of the fibers over one another. The real surprise comes when you cut off a length of fiber and try to break it by hand. You can't exert enough force with your bare hands to break the fiber (at least not without risking having the fiber cut into your flesh). What looks like a thread has the tensile strength of steel wire roughly the same thickness. The Kevlar I bought was obtained from the Canadian distributor for Edmond Scientific. In the Edmond catalog, the item is catalog number G34,883. Price is $13.50 U.S. for a 600 yard spool. I don't have the contact information for Edmond Scientific in the U.S., but Canadians may contact Eftonscience Inc., 3350 Dufferin St., Toronto Ontarion M6A 3A4 (416-787-4581). -- Bruce Dunn Vancouver, Canada a752@mindlink.UUCP
marty@puppsr.Princeton.EDU (Marty Ryba) (02/09/91)
In article <4728@mindlink.UUCP>, Bruce_Dunn@mindlink.UUCP (Bruce Dunn) writes: |> Kevlar is fascinating stuff. I just acquired a spool of Kevlar fiber for |> tinkering purposes. It looks like pale yellow dental floss, or like polyester |> sewing thread. The spool that I have is loaded with a strand that has two |> individual thread-like fiber bundles twisted around each other. The thread is Kevlar is fascinating stuff. It doesn't have to be yellow; I've seen it white too. |> The Kevlar I bought was obtained from the Canadian distributor for Edmond |> Scientific. In the Edmond catalog, the item is catalog number G34,883. |> Price is $13.50 U.S. for a 600 yard spool. Though the price doesn't sound too bad, for convenience and maybe a better price, plus for stuff that is really optimized for tensile strength with high flexibility and minimal abrasiveness (needed for making cables that last), go to any good archery shop. There are several brands of Kevlar on the market; one was called "Super Flight" or something like that was twice as strong per weight than standard Kevlar, and lasted longer since one needed fewer strands per cable and it was less abrasive. Remember, the lighter the string, the faster the arrow will go. Archery involves some high-tech materials science and physics besides being plain fun. -- Marty Ryba | slave physics grad student Princeton University | They don't care if I exist, Pulsars Unlimited | let alone what my opinions are! marty@pulsar.princeton.edu | Asbestos gloves always on when reading mail
vail@tegra.COM (Johnathan Vail) (02/12/91)
In article <6117@idunno.Princeton.EDU> marty@puppsr.Princeton.EDU (Marty Ryba) writes: In article <4728@mindlink.UUCP>, Bruce_Dunn@mindlink.UUCP (Bruce Dunn) writes: |> Kevlar is fascinating stuff. I just acquired a spool of Kevlar fiber for |> tinkering purposes. It looks like pale yellow dental floss, or like polyester |> sewing thread. The spool that I have is loaded with a strand that has two |> individual thread-like fiber bundles twisted around each other. The thread is Kevlar is fascinating stuff. It doesn't have to be yellow; I've seen it white too. |> The Kevlar I bought was obtained from the Canadian distributor for Edmond |> Scientific. In the Edmond catalog, the item is catalog number G34,883. |> Price is $13.50 U.S. for a 600 yard spool. Though the price doesn't sound too bad, for convenience and maybe a better price, plus for stuff that is really optimized for tensile strength with high flexibility and minimal abrasiveness (needed for making cables that last), go to any good archery shop. There are several brands of Kevlar on the market; one was called "Super Flight" or something like that was twice as strong per weight than standard Kevlar, and lasted longer since one needed fewer strands per cable and it was less abrasive. Remember, the lighter the string, the faster the arrow will go. Archery involves some high-tech materials science and physics besides being plain fun. Should this thread go somewhere else? Anyway, kite shops sell "300 pound" kevlar string. It is yellowy, braided I think, and quite strong. Just the thing for flying a couple of 10' stunters in a hurricane... jv Law of Stolen Flight: Only flame, and things with wings. All the rest suffer stings. _____ | | Johnathan Vail | n1dxg@tegra.com |Tegra| (508) 663-7435 | N1DXG@448.625-(WorldNet) ----- jv@n1dxg.ampr.org {...sun!sunne ..uunet}!tegra!vail