Servicing a Schmidt

[Ian H]

Ah!

...um...

[Brucey]

.... I'm not a big fan of 15G spokes, given potential breakage at nipples.

fair enough, but IME if spokes break at the nipples this normally is a pretty good indication of inadequate stress-relief in the build.  Stress relief in short spokes is tricky; I've had to stress-relieve 13G spokes that are less than 90mm long and  eventually the selected method was to use.....

... a hammer....

cheers

[rogerzilla]

It's also a result of non-perpendicular spoke/rim angles, which LWaB has avoided by going radial.  This angle is a general problem with l/f hubs and small diameter tangentially-laced wheels, although the problem is minimised by reducing crossings and making sure there is a hard kink in the spoke where it exits the nipple, not a soft bend.  Very aggressive stress relieiving, using an old crank as a lever between the spoke crossings, will usually give you this kink.

[Brucey]

hence the hammer approach....

I don't remember any wheels that I have built (which is many hundreds now) breaking spokes.  However I am very particular about stress relief and I do try and avoid having (ahem) kinky nipples in the first place.

I have an idea that the parallel squeeze (as recommended by Jobst Brandt) may not be ideal for wheels with kinky nipples, in that the kink and the squeeze are in the same plane more or less, so the spoke may have to kink some more once the squeeze is relaxed, thus rendering the stress relief ineffective.  I usually squeeze the other way (i.e. parallel to the axle) so maybe  the spokes see a better stress-relief at the nipple end and a better set/stress relief at the hub end too.

I see plenty of wheels with broken spokes, and it is usually very clear that the spokes have not been set or stress relieved at all; it isn't difficult to do a lot better than that....

cheers

[LittleWheelsandBig]

I do stress-relieving of my wheels, along with ensuring that spokes properly fit the holes in the hub and correct alignment of spokes versus nipples (the reason I choose 0x, 1x or 2x for small wheels) and all the rest. I've broken a handful of spokes in my wheels in the last couple of decades, about matching the number of cracked rims.

My main bugbear is consistency in construction. Why do we use/ recommend DB spokes for large wheels, rather than just thin plain gauge spokes or single-butted spokes (for a snug fit at the hub)? Because having 14G at both the hub and the nipples and thinner elsewhere is recognised as being a little more durable/ forgiving of corrosion, etc. I don't see why that approach should change for wheels that are 2/3 the diameter.

[Brucey]

sure. But then again one of the benefits of DB spokes in larger wheels is lost in smaller ones whether you like it or not, in that short spokes are less elastic than longer ones.  Then again the service loads in smaller wheels are different too; arguably small wheels are a lot stiffer so you can use fewer spokes and maybe they will see smaller loads anyway.

I suggested 14/15G SB spokes as a pragmatic alternative to DB ones, if you can't get DB ones.  I will happily use PG 15G spokes in many kinds of wheels.

cheers

[jsabine]

I don't see why that approach should change for wheels that are 2/3 the diameter.

Obviously its a bit chicken and eggs, but isn't one of the issues simply spoke availability? No use recommending DB spokes for little wheels if you can't get hold of them.

One thing that presumably feeds into availability is consistency of manufacturing - I guess that you can produce a lot of different lengths for big wheels if you process a batch of spoke wire to a swaged length of c20cm, while you'd probably want different swaging for 349 and 406 wheels, not to mention all the other wheel sizes. Given that small wheels on decent bikes are a bit of a minority interest, and as Brucey says the benefits from DB spokes are arguably lower in any case, there's an awful lot of reasons not to manufacture for a limited market.

[rogerzilla]

A lot of people buy DB spokes for weight saving and there isn't much weight saving with a small wheel.  That may explain the lack of them on the market.

I think DT Revs would be great on a Brompton wheel, giving the spokes the elasticity they otherwise lack due to their short length.  The objective, of course, is that a spoke should never go slack even when you hit a bike-eating pothole.  DT Revs are very slow to build with, though, due to their ability to twist 360 degrees 

[LittleWheelsandBig]

Moulton special-ordered a few lengths of a couple of models of DB Sapim spokes. Sapim will make any length you want for virtually any of the their models but the minimum orders are a bit much for most folk.

Extreme DB spokes like DT Revolutions are arguably better for small wheels than for large. Large wheels tend to have too much lateral movement with those sorts of spokes.

The more extreme DB spokes have very short butted lengths and the production process gives a fair bit of freedom in selecting a swaged length. It is just a case of minimum orders...