From: dlp@Eng.Sun.COM (Dan Pritchett - SunSoft Engineer) Date: Fri, 6 Nov 92 08:21:06 PST Subject: YABS Yes, that is Yet Another Blown Spoke. Here are the details. Bike: Ryan Vanguard Rim: 26" Matrix ATB Comp Alloy Spokes: DT 2.0mm stainless Hub: Phil Wood (newer unit that is a single cast) Spoke Pattern: 3 cross Tire: Pan Racer Hi-Road @ 90 psi All of the spokes were checked about 300 miles ago and the wheel was fine. I've had a scruffing noise that the bike shop could not locate. I thought it was a broken spoke, but they couldn't find a problem. The chain had chewed up several spokes for an unknown reason (it's never been into the spokes) about 500 miles ago, and all of the spokes with a knick were replaced. This morning I found a broken spoke on the freewheel side again. It is broken at the hub. It is a spoke that pulls the rim as the bike is pedaled. I am considering having the bike shop relace the wheel in a 4 cross pattern and use "butted" spokes (yes, this is the wrong phrase, but I can't remember the correct term for spokes). I am thinking DT stainless again with a 1.8-2.0-1.8mm taper. Does this seem like a reasonable solution? Should I expect to blow spokes on the Vanguard every 200-1000 miles? Thanks Dan Pritchett | ARPA/Internet: dlp@zule.Eng.Sun.COM SunSoft Desktop Prod. Tools | GEnie: D.PRITCHET3 | Packet: KM6PR@N0ARY.#NOCAL.CA.USA.NA -------------------------------------------------------------------------- I used to think that I was cool. Running around on fossil fuel. Until I saw what I was doing. Was driving down the road to ruin. James Taylor From: lenny@hobbs.hunt.inmet.com (Lenny Goodman) Date: Fri, 6 Nov 92 13:19:54 PST Subject: Re: YABS I'm not sure if recumbents put special stresses on a rear wheel, but I would think that you already have very good spokes (DT stainless), and a perfectly adequate crossing pattern (X3). I don't think butted spokes or cross-4 is the answer. Maybe the spoke tension is wrong (too loose or too tight). Or maybe the tension is not consistent for all spokes on one side of the hub (freewheel side spokes will have more tension). Rear wheel pulling spokes are the most common ones to break (assuming there is no physical damage to the spokes due to the chain or an accident). I beleive Phil Wood hubs have a bevel on both sides of the spoke hole, so the spokes were not put in backwards. If you had the wheels built locally, I would talk to the wheel builder about improper tension, or have another wheel builder you trust check them out. Len Goodman From: SteveSgt@torrent.sj.ca.us (Steve Sergeant) Date: Sat, 07 Nov 1992 00:02:08 PDT Subject: Re: YABS On Fri, 6 Nov 92, dlp@Eng.Sun.COM (Dan Pritchett - SunSoft Engineer) wrote: >I am considering having the bike shop relace the wheel in a 4 cross >pattern... The 4-cross pattern has seemed to help every bike I subject to heavy touring or commute-luggage loads ride smoother. I'm convinced it's contributed to wheel longevity. >...and use "butted" spokes (yes, this is the wrong phrase, but I >can't remember the correct term for spokes). I am thinking DT >stainless again with a 1.8-2.0-1.8mm taper. The only reason to use butted spokes is to save miniscule amounts of weight. You're touring and commuting on your Ryan; why not go for straight 2.0mm spokes as I have done on my touring and commuting bikes? > >Does this seem like a reasonable solution? Should I expect to blow >spokes on the Vanguard every 200-1000 miles? I put about 6,000 miles on my original Vanguard wheel without spoke breakage (Sun Chinook rims, 1.8mm 3-cross, 36 hole suzue sealed hubs). My wheel finally failed, as you know, from the rim adopting a funny shape that couldn't be corrected by spoke tension. If you ride like such an animal, perhaps you should go to a 40 or 48 spoke tandem wheel. :-) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Steve Sergeant Internet: SteveSgt@torrent.sj.ca.us 3266 Tulipwood Ln. Radio: KC6ZKT [@N0ARY.#NOCAL.US.NA] San Jose, CA 95132 GEnie: STEVSERGEANT (408) 945-0395 FAX: (408) 945-0543 Audio Engineering, Music, Macintosh, Bicycles, Backcountry, Japan From: mason@asylum.sf.ca.us (Meat Vehicle) Date: Sat, 7 Nov 92 18:42:03 -0500 (EST) Subject: Re: YABS I have a few thousand miles on my Ryan, many of them agressive and offroad, I've never had any spoke problems. I don't know what the rim/hub combo is, it's whatever they came with in 1989, but it does have (36) butted spokes. From: M.S.Gerritsen@sms.utwente.nl Date: Tue, 10 Nov 92 13:24:45 WET Subject: re: Butted spokes (WAS: YABS) Spokes are butted because rims are elastic. Compared to straight gauge spokes, the db spoke has to be stretched further to achieve similar tension. When the rim is deformed the db spoke still will retain some tension, while the straight gauge spoke could be totally unloaded. Completely unloading a spoke puts a higher fatigueloading on it, and makes it more likely that the nipples will work loose, making for even more trouble. 4x lacing can cause problems because of the acute angles. When the spokeholes prevent the nipples from aligning with the spoke, bending stresses will be induced in the threadroot. Remember lacing patterns depend on wheel-hub diameter. I'd say that 4x in a 26" rim is on or over the limit. It is more benificial to decrease wheeldish by shimming the freewheel as far over to the right as possible. Do you really need 8 or 7 cogs? Check that the spokes are compatible with the flange thickness. To thin a flange compared with the lenght of the section between bend and head will introduce bending-stresses again. If necessary use washers between spokehead and flange. Some high-gloss stainless steels are supposed (by some) to suffer from road-salt induced fatigue. /Marten From: " pardo@cs.washington.edu" Date: Sat, 07 Nov 92 10:35:10 -0800 Subject: Butted spokes (WAS: YABS) >[The only reason for butted spokes is to save a bit of weight.] Butted spokes also have a smaller aerodynamic profile. Reducing the air drag from wheels is important for a go-fast. There are two other reasons I've seen given for butted spokes. I don't know if they are true or hooey, but I'll tell you the arguments anyway, since they are more applicable to daily riding: Most spoke failures in straight-gague spokes occur at the ends. Making the ends slightly larger or the center slightly thinner changes the distribution of stress so that ends are fatigued less, and, thus, the whole spoke is less likely to fail. A well-designed spoke will fail about as often in the center as at the ends (and rarely!). and Since the thinner section is more elastic, the whole spoke is more elastic (has a smaller spring constant). The thin spoke can be tightened to the same tension as a fat spoke, but a given added force stretches the thinner spoke further. When a load at the rim changes the tension of one spoke, a more elastic spoke will spring further and thus share the load among its neighbors. The second argument makes less sense to me, but since rims are not perfectly stiff, I'm still willing to believe that the effect is potentially important. ;-D on ( The literary wheel: such a simple device ) Pardo From: " pardo@cs.washington.edu" Date: Fri, 06 Nov 92 14:00:52 -0800 Subject: Spoke failures >[The spokes may have been too loose or too tight.] Which reminds me/I forgot: if the spokes are not `stress relieved' during building, then they will loosen during the first few hundred miles of riding. When the spokes are loose, then each spoke is cycled through a greater range of tensions each time the wheel goes around, fatigue is accellerated, and an otherwise fine wheel will start blowing spokes. ;-D on ( Spoke failures, acted successes ) Pardo