01-04-08, 07:37 AM
Check out the twisted spokes on these BMX wheels. I've never seen anything like that before.
Is it a good idea?
This guy seems to have twisted the spokes two whole turns, which is the most I've ever seen. But this lacing pattern, sometimes called a Snowflake Pattern, has its fans. Do a search using that term and you'll get a few hits, maybe even a link to further discussion.
I twisted the spokes on the front wheel of my Downtube Mini when I put a Shimano Nexus front hub into it; the new hub is larger than the old one, so the spokes were a little too long, and the twist used up the extra. I did a half twist. That wheel now has ca 3000 miles on it, and has caused me no trouble. I later put a SA 3-speed hub in a 20" wheel for my daughter's bike; did a whole twist on those. She's ridden it less than 100 miles, though, so I can't comment on its durability. Recently I rebuilt the 16" wheel on my Kent Ultracheap Folder with a SA 3-speed hub, also doing a whole twist, but haven't actually ridden that yet; looks great, but I can't comment on its durability yet. To be clear, in each case I've used the original spokes, which were too long, so instead of buying new spokes I put in a twist to use up the excess length.
Small wheels with large hubs have unusually short spokes, which can't stretch and bend with the bumps the way long spokes in big wheels do. This causes them to break at or near the head. Twisting spokes effectively combines two spokes into one. Shocks travelling from the rim, which would normally be concentrated on one spoke, are now shared between the two. Furthermore, the twist puts a little bit of a spring into the middle of each spoke, which should somewhat reduce the dynamic stresses on the spokes and somewhat increase the flexibility of the wheel as a whole. Also, there's a little more room between spokes, making it easier to pump up the tires.
No doubt there are disadvantages. The nipples meet the rim at an even more oblique angle than otherwise, concentrating the pressure of each spoke on one side of the spoke hole, which is probably bad for the rim. The bending of the spokes probably weakens them as well, though this is not a part of the spoke that is prone to breakage. And of course, if one spoke breaks, you lose tension in two.
Somewhere on this forum you'll find a photo of the front wheel of my mini. I'll post pictures of the other two one day....
01-05-08, 12:09 AM
In my wheelbuilding book the swiss bloke who wrote it says twisted spoke patterns are a phase most bike rebels go through at one stage and has very little positive to say about it bar the fact that if they are doing that then at least they aren't smoking dope or robbing pensioners. What a wag - those crazy swiss! :)
It's not something that adds strength - it's really a 'bling' thing so you pays your money and takes yer' choice on it. I for one would lose even more hair than I have trying to calculate spoke lengths for such an enterprise!
FYI - this is the book I'm talking about which is really good if you like dry swiss wheel humour :)
That wheel building book by schraner is great.