Dale - We all think in different ways, and the easiest way for me to describe is to ask you to draw a picture at full scale of half a rear wheel. Start with a symmetrical wheel on 120 mm OLN, and note the key angle formed by the spoke and a parallel to the hub spindle. Just put the flanges at the right place and the rim at the right place, and check the angle. Might Now, superimpose on that sketch a 5-speed, conventionally dished, with the inboard left flange. As I visualize things, the left side angle is more than twice the "acuteness" of the right spoke angle, that is, the deviation from perpendicular. When you run out the trigonometry, that's why the left spokes are so much looser than the right ones: to get the same axial tension (not total tension) on the right spokes as the left ones have (and that's what locates the dish), you have to have much more total tension on the right side spokes. Now, if you move the left flange outboard 7 - 10 mm, you make the angle on the left side that much more acute, and the loads on the right side to balance that much higher.
But wait! We've misunderestimated things (as GWBush might have said). We've assumed the spokes are radial, when in fact they are somewhat longer if they are conventionally crossed. Which has the effect of making the angles even shallower, and that axial component even greater. You could simulate this by just assuming that the wheel you're building needs 300 mm. radial spokes, eh?
So, maybe if you want to use an outboard left flange, you should compensate by lacing radially on the right side. :-)
Now, I haven't done the measurements, and it was the early 1960s when I had my only real experiences with the outboard flange (Normandy, HF, 36, with Weinmann clincher rims). And my problems went away with the replacement hub. That wheel was built by a local bike shop in Houston, not too sophisticated a place with these new-fangled derailleurs in 1962. The proprietor assured me that the cam-type Weinmann brake QRs on the hangers were used by racers as drag brakes... But the wheel he built lasted.
If it's important, I'll brush up on trig and get the stress ratios. Or ask Beloved Spouse for help: she tutors math, and I haven't committed the crime of trig in several decades now.
harvey sachs mcLean va
On 1/3/11 6:37 PM, Dale B. Phelps wrote:
> wow! I'd always understood that the cause of broken spokes was too
> little tension, and that wheels should be built tight, not "loose."
> I've also on rear wheels never (repeat NEVER) have had a spoke break on
> the drive side without stuffing the derailleur into them (I confess THAT
> happened once.) Drive side spokes s/b very evenly matched in tension and
> very tight, with non-drive side spokes what 2/3 the tension of drive side?
> And (for ME) it is also hard to believe that a 7mm outboard difference
> on the non-driveside rates an almost vitriolic regard (yes Harvey I was
> impressed by what I read.)
>
> I don't know if other CR members have the experience of bent rear
> spindles (since it does not rotate, it is a spindle, not an axle) but I
> have, and even when I was a svelte 170 pounder. Now that I am 200
> pounds, I thought this "oddball" 40 hole rear hub with the
> more-distributed load bearing would perhaps better endure this big beefy
> boy's, never again bending another surprisingly pricey campy hub spindles.
>
> I know that opinionism about wheels is rife, and I would never presume
> myself to be a comprehensively-minded wheel builder, but I now wonder
> about the issues that Harvey so staggeringly articulated, and before I
> take a few hubs and rims (and hopefully, proper-enough-looking modern
> spokes sourced from one of our favorite suppliers) out to Santa Clara
> for some building, I'd like to hear from others about use of this one
> hub in particular (the bottom one in the below foto):
>
> http://www.wooljersey.com/
>
> IS the 7mm offset of the outboard flange rear hub I have more than a
> properly-built, properly-tensioned wheel can bear? CAN a skilled
> master-builder work with such a flawed "dumb design"? Or should this hub
> be kept in a case (or offered to a collector) as another example of what
> poor design ideas existed prior to 2011?
>
> Dale Phelps
> Montagna lunga Colorado USA
>
>
> From: Harvey Sachs <hmsachs@verizon.net>
>
> Until this morning, I'd assumed that Normandy/Atom was the only
> widely distributed hub with as dumb a design for derailleur bikes as
> the lower one in Dale's picture. It's good to know that campagnolo
> had one of these, and wish I had one to add to my small collection
> of Campag's worst designs, together with the Gran Trashmo, the
> single-pulley Sport RD, and the various "matchbox" or plunger FDs.
> The ones designed to grit up the sliding contact.
>
> In Dale's picture, I'm talking about the lower one, the one with the
> left flange all the way outboard, for the best possible bracing, eh?
> NO. All the way outboard, for the highest possible tension on the
> nearly vertical right-side spokes. My first Sears came with such a
> beast, which served well - like a mule - for teaching patience.
> Because one got pretty good at the drill of removing the (two-notch)
> FW to replace the spokes that popped.
>
> I can only assume that these hubs, like the vermiform appendix, were
> relics of some earlier, functional, design. Like maybe a 110 OLN for
> single-speed FW. Then respaced at some marketer's command, to get a
> product out the door when those crazy Murakins wanted some absurd
> 5-speed FW.
>
> Build it up, Dale, for someone you really, really, dislike. Or not,
> in the spirit of wishing all a wonderful New Year. Like some other
> Campag parts, nice eye candy for the brain to reject.