7

Wheel building using a SON Dynamo hub (28 12 disc), Wheelsmith DB14 spokes (stainless; J-bend), and Velocity Atlas rims (700c; 32 hole) with a two-cross lacing pattern. Disc brake, loaded touring.

The spokes bow out far from the dynamo's flange. I did all of the inner spokes first, and couldn't get an outer spoke to pass under an inner spoke (4 holes down) without crazy distortion. Even going straight to the rim hole was awkward. Probably would kink once tightened.

Spokes don't lie flush with hub flange

Doesn't seem to be the parts. Though the SON dynamo hub has a thicker flange, its manual specifies 2mm spokes, which is what I'm using. Peterwhitecycles appears to use the SON-Wheelsmith-Velocity combo in their wheelbuilding and recommends two-cross. Here's an example where someone used SON+Wheelsmith DB14 and two-cross lacing.

Here's what I've already tried. Working the spoke to seat the head better, angling the spoke toward other holes, and even applying slight pressure to see if the elbows would bend a tad. Just avoiding the bending problem by not passing the outer spoke under the inner spoke feels like a bad idea.

Any suggestions?

2
  • 1
    How thick is the flange? I don't see washers in between the spoke head and the hub's rim, did you use any?
    – Criggie
    Apr 13 at 6:13
  • 1
    The flange is 3mm thick at it's thinnest point, and it gets slightly thicker towards the holes. There aren't any washers.
    – Laoshi
    Apr 14 at 1:59

1 Answer 1

13

Bowing as the outer spokes exit the flange is normal. The angle when the spoke is made is set arbitrarily, and it's the job of the wheelbuilder to cold set it best as possible to match what the specific wheel wants it to naturally be for the parts used, such that the spoke wraps neatly around the flange and then runs at a straight line to the nipple.

The better you do this the more resistant the wheel will be to going out of true or breaking spokes. Were you to do nothing and tension the wheel up with the spokes forced into position, the tension will eventually mask the issue somewhat, but it will leave a static stress in the spoke and the bowing will tend to work itself out somewhat in use, which causes the wheel to go out of true. Setting the spoke line at the hub (as this topic is usually called) is one of the areas where good handbuilt wheels can stand apart from most machine built ones. (Automated wheel assembly lines can have a step that addresses setting the line and even do an okay job of it, but it's not universal that they have this functionality and the results can be mediocre even when they do).

There are some different schools of thought for what stage of the build process to set your line at the hub. For wheels like you have in front of you where it's a tight fit and the bowing is fairly severe initially, I usually do it once I'm at "ground zero" for thread engagement, which in ordinary circumstances (optimal, uncompromised length spokes) is after the nipples have been set to just cover all the spoke threads, at which time the spokes will still have near-zero tension. When the bends are severe and it's a butted spoke, it's pretty easy to feel what's happening as you bend and to get the bend you need even without tension. Jobst Brandt in The Bicycle Wheel and in his Usenet postings would often refer to doing it a little further along in the tensioning process on the premise that once some tension is established, it can help the builder feel what's happening as they've gone far enough with the bend (I'm paraphrasing a bit here on rec.bicycles.tech posts I only think I remember). Here are the pertinent pages from his book:

bicycle wheel page 96

bicycle wheel page 97

As for the actual technique, I've done it two ways:

  • Pressing hard with the thumbs to smash the outside spokes one by one against the flange as Brandt describes above. Typically the challenge with this is getting the feel for whether you've done enough.
  • Padding a Knipex Plier-Wrench with firm plastic on the jaws to prevent marking the parts and then pressing with that. I have a pretty high opinion of doing it this way because despite the enormous amount of force you can generate compared to doing it by hand, you're not going to go too far unless you try.

You're basically trying to get the spoke to wrap neatly around the flange and wind up aiming naturally at the rim hole. It is a tactile skill that, as Brandt wrote, takes practice. The good news is that while doing an expert level job of it is a key piece of producing wheels that virtually never go out of true, you can still get a reasonable amount of the way there by doing a solid beginner attempt and just get the spokes pointed the right direction.

The other bit of context that might be helpful here is that Schmidt and many other high-end hubs do exactly what you're seeing because they're trying on purpose to create a tight fit and use up all of the bent part of the spoke elbow. Hubs that do a lesser job of this are easier for lacing in mass production environments, but that is where the advantages end. The disadvantages are that looseness means the spokes will tend to have an unsupported area that has to be addressed that much more carefully on a handbuilt wheel in order to give the best lifespan possible. The scenario you're in is the much more favorable one because it tends to be relatively easy to get the spokes to wrap well around the flange as in the illustration above.

6
  • 2
    This matches my experiences - a wheel build always looks like rubbish until it is almost done. I do recall mention of a light hammer tap to help conform each spoke to the hub rim, but can't find mention of it right now.
    – Criggie
    Apr 13 at 6:15
  • 3
    This is also relevant: Stress Relieving Spokes by Jobst Brandt - Sheldon Brown Bending the spokes into a better spoke line probably won't help wheel durability as much as also properly stress relieving the spokes. Apr 13 at 11:41
  • 1
    @AndrewHenle agreed, this is only one of the important handbuilding steps Apr 13 at 15:47
  • 1
    @Criggie In [Sheldon Brown's Wheelbuilding article] (sheldonbrown.com/wheelbuild.html), halfway down there's a part about the light hammer tap in the Initial Spoke Adjustment section. Perhaps that?
    – Laoshi
    Apr 14 at 3:01
  • 1
    Using the resources shared by @Nathan Knutson and Andrew Henle, the problem seemed to be being too afraid of kinking/snapping the relatively brittle stainless steel spokes (If I understood the stress relieving article correctly, pushing the spokes past the stress they'd normally undergo, can actually lengthen their service life.). Pressing the outbound spokes slightly above the J-bend had a lot of tension, like when a twig is about to break. I pressed past that high-tensity feeling, and the spoke gave way by either bedding and/or bending to bow out less. It worked great.
    – Laoshi
    Apr 14 at 3:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.