Published by Tristan on 19 Jan 2009 at 11:11 am
Triplet lacing pattern
I received this question in an email conversation I’ve been having with a gentleman from the USA…I’ve been thinking about triplet patterns quite a bit lately so I though I’d share my thoughts and try and answer some questions.
Speaking of hubs and dish, it seems like you’ve kinda solved that
problem with your triplet spoke pattern setup on that Tune-XR300 setup
that you built. From those pics, it looks like one could use any 32h
hub with a 24h rim, yes? I also noticed that you laced the non-drive
side spokes with the heads in. Any particular reason why? Are the
tensions in the NDS spokes the same as the DS ones now?
Tune Mag180 Triplet rear hub - note only 8 non-driveside spokes
The ‘triplet’ pattern consists of 24 spokes. On the driveside (DS) there are 16 spokes laced 3-cross, on the non-driveside (NDS) there are 8 spokes laced 1-cross. Because there are only 8 NDS spokes every second spoke on the NDS flange is skipped. There are triplet-specific hubs: Tune do a custom triplet version of their Mag180 rear hub, and USA wheelbuilder Troy Watson uses a custom-built White Industries hub designed for triplet lacing. USA company Alchemy Bicycle Works will have a triplet version of their soon to be released ORC rear hub.
Campagnolo / Fulcrum and Corima use similar concepts for some of their factory wheels. The concept of mis-matched drilling is not new and dates back as early as the wheels on a Model T.
By lacing the NDS with the heads in the flange spacing is effectively widened which builds a laterally stiffer wheel. Trying to lace a traditional heads-in / heads-out pattern would be difficult because of the tight bends the spokes would be forced to make in the 1-cross pattern. Lacing the NDS spokes radially would work well and remove any torsional load from these spokes.
The driveside spokes leave most hubs close to a perfect 90 degree tangent. Torsional stiffness is very good and the wheels looks great.
Spoke tension of the NDS tends to be 90% of DS…this allows the DS spoke tension to be lower and the wheel to be built more like a front wheel where all spokes are close to 100kgf rather than 120kgf on the DS but only ~60kgf for NDS as in a typical rear wheel.
The triplet pattern is quite good but suffers a couple of shortfalls:
You can only use a 24h combination – If the rider warrants a wheel with 28 spokes then this pattern will not work.
Should a NDS spoke break the wheel will go so far out of true that it will not rotate inside the frame and will be unridable. I’ve built a few wheels in this pattern and the only problem I’ve had was with a NDS nipple failing – the possible cause was the higher than normal NDS tension combined with the nipple exit angle and perhaps a spoke which was ~1mm too short and cut at a non-perpendicular angle. I rebuilt the wheel with nipples from a different batch and rebuilt the NDS side with longer spokes and there haven’t been any more problems.
The wheel is also quite difficult to build…the ‘rules’ are totally different than for a normal lacing pattern so it takes a bit of thinking, especially with the first few wheels. Even now I have to take my time and really think about what I’m doing as it’s very different to lacing and tensioning standard 24×2.
The rim needs to be very stiff for this pattern. The XR-270 and XR-300 work well but a lighter rim would not work as well. WeightWeenies member mises has an Alex R400 laced triplet on his travel bike but this is the only example I can remember seeing of a light (400 gram) rim being used in this pattern however the XR-200 might be stiff enough for a light rider.
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Troy Watson on 21 Feb 2009 at 10:46 am #
Hi Tristan,
Great blog article! Mises has now built a XR200 into a triplet rear wheel and said it built up easier then the R400. I don’t think it would be stiff enough for larger riders but I think sub 54kg riders could use it.
Tristan on 21 Feb 2009 at 10:51 am #
Hi Troy
I built a pair of XR-200′s yesterday and was thinking about how well they’d deal with a triplet pattern….as you say it should work well for light riders. Thanks for the heads-up.
I haven’t tested the stiffness of the XR-200 but it feels much stiffer than the R400.