Re-build.

26 11 2012

Well…that was interesting….

On bringing the fatsno/marge lite up to tension I found the spokes too short to fill the nipple. As I mentioned previously I used the freespoke calculator, did a lot of reading around and I measured everything except the ERD on the rim by vernier gauge and confirmed the dimensions. I built this combo 3 cross, brought the tension to within 5kgf of 100kgf on the drive side (quite a bit less, but still consistent, on the disc side….which sort of surprised me), it was perfectly dished, spokes were all bent carefully around the flanges etc, with 263mm spokes – nothing funky going on.

But the spokes ended well below the shaft/head of the nipple on the disc side and only just came into the head on the drive side. The on-line wheel build programs suggested that 263mm would be ideal for my build…263.1 left 262.6 right from freespoke for example.

For a primer on why this is not acceptable, see Wheel Fanatyk: Wheel Building Tip No. 9 РSucceed with Alu Nipples.

So, nothing for it but to take it apart and build it up with 264mm spokes.

With 264mm spokes, on the higher tension/drive side, the spokes are 0.5mm away from the ‘top’ of the nipple and come to the bottom of the nipple slot on the disc side. The wheel is perfectly dished and within 0.1mm lateral and vertical (other than the welded joint area, a given), 100kgf/ within 5kgf on the drive side.

Unless there is something I don’t know about going on with the ERD ( I will go and measure this on the rim destined for the front wheel) the calculator isn’t calibrated for aluminium nipples….for brass nipples, 263mm would be fine IMO/FWIW, but not for my wheel build standards!

Oddly enough, if you plug the ERD and measurements into the DT swiss calculator, you pop out….264mm. So, my question is, did Surly cut out the middleman (reminds me of the ‘name your fingers’ song my 2 year old sings….) and in giving the ERD of 543.5 allow us to calculate the spoke length easily on standard spoke calculators that do not allow offset spoke-nipple hole dimensions etc.

Of course, *nothing* mitigates against slight errors on wheel builds – after all you are relying on lots of measurements and in some instances manufacturing tolerances/measuring differences of a mere 0.1mm at every stage could easily lead to a different ideal spoke length.

Nothing can substitute for experience.

On poking around the web, I found an interesting discussion on bikefroums and this informative post from someone called Drew Eckhardt.

(In answer to a question about whether you can compensate for too-short spokes with longer nipples)

“No – that’s exactly the problem here.

The wheel builder used nipple length to finish the distance between hub and rim and nipples are not as strong as spokes, especially when the nipples are made out of aluminum.

Longer nipples would provide more threads below the rim; but those don’t make the nipple strong enough to hold up where it goes through the rim without a spoke’s reinforcement.

Longer nipples should only be used when when the rim configuration results in the spoke wrench flats ending up inside the rim instead of outside where they’re useful for truing. To provide the most tolerance for spoke length and rim diameter variations this in turn dictates using a longer nipple with the same amount of thread you have with a 12mm nipple (Sapim) or spokes that have longer thread (via a spoke threading machine).

DT spokes have 9mm of thread (it might actually be 9.5; but lets use 9mm for discussion purposes)

DT nipple slots are 1mm deep.

Measured to the top of the nipple DT 12mm nipples have 8mm of thread, 14mm 9mm, and 16mm 10mm.

With the 12mm nipple you have 1mm remaining before the spoke runs out of threads and nipple stop turning when your reach the top, or 2mm past the slot. If we assume that you’re allowed to go 1mm below the slot (I wouldn’t since the nipple is narrower there) that provides +/- 1.5mm of tolerance. With spokes coming in 2mm increments some rim + spoke combinations will let you choose a size that ends at the slot for +2/-1mm of spoke length tolerance or +2mm / -4mm of ERD variation or a size that ends at the top of the nipple for +1/-2mm of spoke length tolerance or +4/-2mm of ERD.

With the 14mm nipple you have 0mm remaining at the top, or 1mm past the slot for +/- 1.0mm of tolerance. You might be able to aim for the slot itself; or you might be stuck aiming for 1mm below the slot for +2/-0mm of tolerance.

With the 16mm nipple you have 0mm remaining at the bottom of the slot and +/- 0.5mm. Some rim + hub + spoke brand combinations won’t work at 2mm increments because you need to aim for the bottom of the slot with 0 tolerance for long spokes / small rims or 1mm short of that with 0 tolerance for short spokes or big rims.

That’s not viable with alloy nipples where spokes that are too short result in broken nipples.”

 





Wheels.

25 11 2012

Do like building wheels. The Surly Marge Lites are pretty neat, with the box sections at the edges of the rim which i would presume aids stiffness and durability. I have built my fat rear wheel with a Hope fatsno hub after a lot of deliberation over which 170mm rear hub to use. There are pros and cons of them all…if DT made one, it would be an easy choice! But as it stands, quite a few folk I know and trust use the fatso, it is reasonably field serviceable, allows a nearly symmetrical (stronger) wheel build and spares are from a local source. I would have liked to try the Paul components one, in general I have always found Paul parts exceptionally well made and durable, but having I9 internals makes it slightly less easy for me to get parts if needed.

I used DT comps and Prolock aluminium nipples. As ever, the sums are important and in this instance I used Freespoke, which has the useful feature of allowing for the offset nipple holes, the DT calculator and I also measured the parts myself in order to check the validity of the published numbers. It is important to do this when using aluminium nipples so the spokes ‘fill’ the nipple and durability is high.

 

Next, I plan to disassemble the Hope 170mm quick release and rebuild it with DT RWS end parts. Such is (my) life.





Blighted.

18 11 2012

The last few weeks have slipped by. Snot may have lubricated that sliding. We’ve all been blighted by the cold, coughs and gunky eyes. Nice.

Two things to note though. Firstly, project ‘Snow Job’ is go. Snow Job? a GI Joe character. He has a red beard and is a winter combat specialist. Two pictures, to pique your interest, from Sean (the builder/alpha cheese of Vertigo Cycles).

 

Some stays there with a becoming curve, i’d say.

 

The swaged tube may form the back bone of a set of bars. We’ll see.

I have posted about my plans for a fat bike recently and the ideas have crystallised now. I’m not going to spill all the beans, but suffice to say it will be sweet as. One of the neatest features we are aiming for is a PF 30 bottom bracket shell, in a custom 100mm width. This (when mated with King PF30 BB cups) should allow me to use 24mm or 30mm axle cranks. ’30mm?’ I hear you cry….’e13 then?’. Nope. Sean is hoping to have some super wide Hollowgram axles made that will allow me to use a very versatile, stiff and, yes, light system.

This project is going to take some time. There are several things that will need more than the usual amount of preparation to come to fruition. I’ll obviously post more details as it takes shape.

What else? Mr Naegears and myself took our first track class at the Chris Hoy velodrome. The banking didn’t faze me as much as I thought it might, though I found the rental bikes a tad under geared for booting it…my usual slow cadence is clearly not ideal! I guess if you have ridden a fixed gear and/or in a skate park you will be ahead of the game. It is wicked good fun. I’d thoroughly recommend having a go. Our next class is soon and you can bet I’m going to practice walking around on smooth concrete floors in grip-less look keo cleats a bit more before my next visit. Yep, it was pretty embarrassing!

 

So. There we have it.

Today’s music from RL Burnside.