![]() |
#1
|
|||
|
|||
![]()
"Sheldon Brown" wrote in message
... ed wrote: I keep hearing about emergency kevlar spokes but can't find in my area. Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting? -- Phil, Squid-in-Training |
Ads |
#2
|
|||
|
|||
![]() "Phil, Squid-in-Training" wrote in message Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting? Kevlar has poor fatigue characteristics. |
#3
|
|||
|
|||
![]() |
#4
|
|||
|
|||
![]()
In article , "Phil,
Squid-in-Training" writes: Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting? There is a wheel like that, the Topolino, page 30 in the Colorado Cyclist catalog. The kevlar/carbon spokes "span the entire wheel" and are held to the hub by a sleeve (personal observation while drooling in CC's showroom). The tension goes from side to side of the rim with very little tension on the flange. No more elbows to break. I've no clue as the durability and will certainly not be the first one on the block to have personal experience with a set of them. But at $499.99 rear and $349.99 front I hope they are durable. www.topolinotech.com Tom Gibb |
#5
|
|||
|
|||
![]() Andrew Lee wrote: "Phil, Squid-in-Training" wrote in message Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting? Kevlar has poor fatigue characteristics. Were are the facts on this statement? Having worked with Kevlar I would never had thought this to be true. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 80,000 Newsgroups - 16 Different Servers! =----- |
#6
|
|||
|
|||
![]()
"Phil, Squid-in-Training" wrote:
Would you be able to lace a wheel entirely with kevlar cords? And have it be useful/long-lasting? Maybe. Chafing of the surface fibers could be an issue, and might be why composite-spoked wheels have used resin to encapsulate fibers into a somewhat-rigid spoke. Spoke stretch (and therefore wheel rigidity) would almost certainly be a problem, and it's difficult to imagine what advantages such construction might have to offset its higher material and development costs compared to a conventional wheel. Spinergy Spox are one example of wheels made with synthetic fiber spokes. The earlier Sugino Tension Disc used a web of aramid cords radiating out in several diractions from each nipple, with the whole web for each side sandwiched in plastic film. Chalo Colina |
#7
|
|||
|
|||
![]() "S. Delaire "Rotatorrecumbent"" wrote in message ... Kevlar has poor fatigue characteristics. Were are the facts on this statement? Having worked with Kevlar I would never had thought this to be true. I guess to be accurate, it would be better to say how it is used. I got this impression from a climbing perspective, where it is fairly common knowledge that kevlar has poor flex fatigue and is that is a consideration for cord where there is constant flexing. Thus you wouldn't want to tie and untie knots in the cord regularly, but you can tie it once into a loop for your Hexes (a form of rock protection or anchor). You can google this for more information... I also found references to it loosing strength in sail cloth applications (where they also found Kevlar had problems with long term UV exposure, a problem that can be overcome though I think). I'll leave it up to you to google for perhaps a more scientific paper with testing... I also found these old Jobst posts: Ed Chait writes: I would think that at least on a single speed, or fixed gear bike, a narrow, toothed Kevlar belt and aluminum sprockets would be lighter, cleaner, quieter and never require lubrication. I'm sure a belt drivetrain has been tried before. Why has it never caught on? It's good you say that in the subjunctive, there being no proof that it is possible or practical. Kevlar is definitely not the medium, it fails in fatigue as soon as it absorbs a little moisture, and it IS hygroscopic. Kevlar has limited uses and timing belts is not one of them. Jobst Brandt avid G? writes: Yes, that's the kind I also had in mind when replying, and it is such belts where the Kevlar fibers break in fatigue with the absorption of humidity. I doubt that anyone makes timing belts with Kevlar these days. Their frailty must be common knowledge in the business. A quick Excite net search revealed quite a few companies with sales info for Kevlar reinforced belts. Maybe it's not a major problem for certain products or conditions. I'd be curious to learn more. We don't know where the Kevlar is and how it is used. It's somwhat like the sticker "Intel Inside" on a product. Jobst - do you have quantitative data, references or experience that would be informative for the rest of us ? I was involved in the development of paper moving plotters at HP before their ink jet plotters. These plotters used timing belts to move the carriage and paper (X&Y). We tested all sorts of belts and discovered that, in the humidity chamber, all Kevlar belts failed. We used conventional Rayon backed belts after that with no trouble. No papers were published on these findings, they being insignificant in that sort of work. Jobst Brandt ow, it may be that Kevlar is not "bad" in fatigue characteristics when used in pure tension,it is doubful that it can compare to steel operating at stress below the fatigue limit. I amnot familar with how the fibers would be secured at the ends, but if there are lots of bendsthat might cause problems with the constant stress cycling of loading rolling wheel...I don't know for sure though. In what applications have you worked with Kevlar? |
#8
|
|||
|
|||
![]() |
#9
|
|||
|
|||
![]()
Sugino T-Disc ( aka Tioga T-Disc) were 256 kevlar strands mounted in a
mylar sheet. They were 32-hole format for use with a standard hub and rim and worked just fine. They were actually lighter than 32 spokes. Really. http://www.yellowjersey.org/wheel.html Hey cool - I see my idea has some validity! -- Phil, Squid-in-Training |
#10
|
|||
|
|||
![]()
On Fri, 11 Jul 2003 13:22:48 GMT, Jasper Janssen
wrote: I wonder what would happen if, as a physics experiment, you laced a wheel with a single steel cable, using appropriate sized pulleys at the hub and the rim, and a single inline tension adjuster at one point. The pulleys would have to have fairly heavy duty bearings to roll under 200 kg tension, though, I don't think a bushing is gonna do that trick. On the other hand, even at relatively severe deflections of the rim, the pulleys would have very little actual movement to do in order to equalise the spoke tension across the wheel. Hmm. If 'spoke' tension is always equal on each of the spokes, then there's no force holding up the hub, and thus the hub would fall down to the ground instead of being held up. Oh well, there goes my experiment. As someone pointed out in email, I missed an important thing: As the hub does its sagging, the "spoke"/wire angles change and provide a net force upwards. So the wheel should behave more or less[1] as the rigid-rim/rubber spoke model: as you're riding along, the hub will be positioned slightly (or maybe a lot) below the center of the rim. Jasper [1] In several ways less, of course. |
Thread Tools | |
Display Modes | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Strange pinging noises from rear spokes... | Paul | Mountain Biking | 4 | June 15th 04 12:39 AM |
Kevlar Tires | Neil Smith | General | 7 | August 13th 03 11:12 AM |
Replacement for rim with offset spokes | Richard | Mountain Biking | 1 | July 23rd 03 12:15 PM |