Another product we showed at Interbike was our new spokes and taper hex nipples for 2008…
Traditional spoke nipples are made of brass, brass isn’t a particularly strong metal, but it is a pretty heavy one. Aluminium is about a third the weight of brass, so making aluminium spoke nipples seems like a good way to save weight without losing any real strength right?
Well the problem with previous aluminium spoke nipples has usually been that they round off really easily, because although aluminium can be as strong as brass, it is a lot softer. When you slide a traditional square spoke key onto a square nipple, there HAS to be a little gap, if the spoke key fitted perfectly then sliding it on and off would be impossible. This little gap means that the key moves slightly round the nipple and just presses right on two opposite corners of the nipple. With nice hard brass this isnt usually a big problem, but with softer aluminium nipples they just cant take this and distort.
Our solution to this issue is to make a special hexagonal nipple and key.
Hexagons work better than squares for transferring torque. That’s why most other nuts and bolts on your bike use them, but with a straight parallel hex getting the key to fit right would be even harder. But our nipples TAPER and so does our key. So the key slides on easy then as it slides down the nipple gets tighter and tighter fitting until ALL the gap is eliminated. This means that the key FULLY supports the nipple and spreads the load over FIVE of the six corners.
It is pretty hard to see the taper because it is very very slight, but this cad rendering might help show it.
The key itself has the matching female taper hex and is kept as simple as possible so you can keep it on your key-ring so it is always handy.
On the spokes themselves we wanted to save a little weight too, but without going as far as a traditional double butted spoke. Our solution to this was to make a very gentle transition and to reduce the section area by just 20%. We also kept the butting away from the hub flange where grind damage is most likely to occur.
We call this “semi-butting”, though technically it is still a double butted spoke.
You are going to have to look pretty hard at the first photo to see the very gentle transition from one size to the other, but it is there and it saves about 15% off the weight of the spokes.
Combining these two, we can produce a weight saving of about TWO ounces per wheel. A little less on a 36, and quite a bit more on a 48. For a typical 36 front 3cross and 48 rear 4 cross you should see a weight saving of well over a quarter of a pound, without any difference in wheel strength, but that is a real pleasure to true thanks to the taper-hex nipples.