jrouly

My latest foray into wheel building has found me attempting to lace a Sturmey Archer GH6 front dynohub onto a 700c box style rim. I am having absolutely no success with it, and I'm starting to suspect I've got the wrong length spokes entirely.

The rim is the Velo Orange PBP Polished Box Rim. 32h, ERD of 606mm.

The hub itself is a little harder to nail down the measurements for.

My measurements:

• OLD = 94mm
• NDS flange diameter = 42mm
• NDS flange centerline offset = 33mm
• DS flange diameter = 102mm
• DS flange centerline offset = 26

I've found slightly different measurements on Edd (spoke calculator) and in a post by mrrabbit on these forums (which I can't link to because my account is new -- the title is "Sturmey Archer Dynohub "8 59" 32H Wheel Build Information FYI").

I plan to do 3-cross on both flanges (unless advised otherwise).

The spoke lengths I've come up with (and purchased) for this rim+hub+cross combination are:

• DS = 16x 296mm
• NDS = 16x 287mm

However, whenever I try to build the wheel (I've tried many times now), I end up coming up about 1cm short on opposing spokes after one side is built.

What gives? That mrrabbit post indicates I should allow for a cross factor of 3.10 in my calculations instead of 3.0, but that only yields 1 and 3mm increases in calculated spoke length. Is that enough of a difference in tolerance to warrant buying new sets of spokes? It doesn't seem like 3mm would be enough to bridge a 1cm gap observed when building.

Help!

Bike Gremlin

Either not properly measured, or not lacing it properly. Your spoke lengths for the measured results you wrote here do match up pretty well.

A recommendation, if I may, unless you've already red it:

https://www.wheelpro.co.uk/wheelbuilding/book.php

Bill Kapaun

You need to get ALL the nipples started on both sides first.

8-10mm is what you would be short if you were trying a 4X accidentally.

jrouly

​​​​​​So I found an old original wheel building guide put out by Sturmey Archer, and they recommend entirely lacing one flange first. I have tried that, as well as lacing one side halfway then the other, then back to the first side. In both cases, the nipples are either sticking out of the rim or started correctly.

And in both cases, the gap appears once an opposing spoke is laced opposite a completed side of the wheel.


This is a good point. I'm definitely not accidentally lacing 4X, but seeing that gap made me think I should be doing 2X instead of 3X.

When I try 2X though the spokes are simply too long, and I'd need to file down quite a bit of threads.

speedevil 

Normally, you'd lace the trailing spokes (heads out) on one side, then the trailing spokes on the other side. When the wheel is half laced, there will be 8 spokes from each flange laced to the hub. Then you lace the leading spokes (heads in), and it doesn't really matter which side you lace first.

Agreed that inadvertently miscounting and winding up with a cross 4 pattern will leave the spokes roughly 8-10mm short.

I think the PBP rim has holes drilled offset so that the eyelets aren't in the center of the rim but alternate slightly right and left of the centerline. Do all of the spokes from one of the flanges go to eyelets that are on the same side of center?

The first spoke normally goes to the right of the valve stem hole, but some rims are drilled differently and the first spoke needs to go one hole away from the valve stem hole so that they go to the eyelet on the same side of the flange. Regardless of the "handed-ness" of the rim, the second spoke will leave 3 empty holes in the rim between the it and the first trailing spoke.

jrouly

The rim has all the eyelets drilled on the centerline.

I will upload a pic of the lacing in progress this evening.

ljsense

That's a sweet book -- every time a wheel building question comes up, I think of just posting that link. Good job.

Bill Kapaun

I assume you are only screwing the nipples on so that 1 thread still shows?

You may have an "indexing" problem where you are starting the 2ND SET 1 hole off on the OPPOSITE FLANGE from where you should.
I'll attach a crappy pic to show one ea. correct/wrong. The left is correct if your 1st spoke was adjacent to the valve hole and proceeding counter clockwise.

fietsbob

One of these? It comes up for S-A GH6 hub.

TiHabanero

Every time this happens to me I know I screwed up the starting spokes. Time to do it again, Sam.

jrouly

I'm actually threading them even looser because I was concerned about them being so short -- quite a few threads showing, a little over five.

Yep that's exactly the one. The wheel building guide I found for it is an old Sturmey Archer document and covers many of their hubs, with specific instructions for dynohubs pointed out, which I have been trying to follow.

I'm not sure if I can attach images yet, but once I can I will.

rhm

I assume that's what we're talking about. The first time I built one of those into a wheel, I got utterly baffled. I had no clue how I had confused myself so badly. I had to quit and start over, and then I made the same mistake again the second time... and the third time. The keyhole shaped spoke holes mean you have to think it all through correctly before you start, and I failed each time. Finally got it right, but oh, man.

Assuming you have the right length spokes, a few tips:

1. Once you have the right spokes, be sure you remember which ones are for which flange. They will be different lengths and it will not be obvious which ones are for which flange. Separate them. Mark the bundles in some unambiguous way. This should be obvious, but I've made this mistake more than once. I'm a slow learner.

2. lace the large flange first. Leave the nipples pretty loose.

3. When you lace the small flange, find some short, thick nails, like roofing nails, or wood screws or something to hold the spoke heads into the holes. Put both spoke heads in one of the holes in the flange, and drop a nail into the center to keep them from slipping out. Put all the spokes through the flange before you start lacing.

4. Once you've got all that done, lace all the leading spokes, then the trailing. Or the other way around, just don't alternate.

5. Once you've got all the spokes in, tighten the small flange nipples first, until you can be sure the heads won't slip out. Then you can remove all the nails.

jrouly

Man I am in the same boat right now. Getting it wrong, trying again, getting it wrong, trying again... I've tried alternating starting points (left and right of a reference spoke on the higher flange), 2X and 3X, pretty much everything I can think of above and beyond what the S.A. wheelbuild instructions say to do. No joy.

Every time I try to lace up the smaller flange, I get to opposing spokes and I just come up a few mm short, a little under a cm.

I don't want to just order another set of slightly longer spokes without knowing that's the issue, but I don't really see any other options at this point.

JaccoW

The shell on these is the same as with their drum brakes right? I have a bike with a front wheel like that. I could take it out and make some pictures if you want. It's probably a 36H hub though.

rhm

Okay, so I'm sitting on a train into the city, after waiting in the station for 45 min (holiday schedule today trying to build your wheel in my head. Good times! I suspect your problem is exactly what @Bill Kapaun referred to in post #8 .

You have laced up the large flange side of the hub, and that went okay, right? And the problem you're having is with the small flange?

So now what I'm wondering is: how many times have you unbuilt and built up the large flange side of the hub? That is, did you build it once and move on, or have you done that several times too?

If you've only done it once, try this. Unbuild it, and move the rim one position clockwise or counterclockwise, doesn't matter, and build it up again. THEN try the small flange again.

jrouly

Yeah, it definitely looks like a similar shell.

Oh man oh man oh man.

I had this whole post typed up about how I'd tried re-indexing several times, rotating each side one hole, etc. But I said **** it and just tried one more time.

This time, when I started the lower flange, I made sure to start the index leading spoke one before the corresponding spoke on the opposite flange, and to lace it through the corresponding rim eyelet one before the opposite spoke. Visually, it looks like the spokes are crossing, but this is because of the flange diameter differential. The spokes are now actually *correctly* indexed.

I'd apparently been avoiding this configuration the entire time because of the look that the spokes were crossing instead of lining up correctly, but it was just an illusion. If you want pictures, search the wheelbuild sub****** for "gh6" and you'll find my post there where I can post pictures.

It laced up perfectly the first go. Now I just need to tension it.

Thank you all so much -- I must have spent two months on this, on and off, trying different configurations and quadruple checking my measurements. The feeling of accomplishment....holy cow guys.

Thanks all!

gilesa

From the initial post:

My measurements:

• OLD = 94mm
• NDS flange diameter = 42mm
• NDS flange centerline offset = 33mm
• DS flange diameter = 102mm
• DS flange centerline offset = 26

I've found slightly different measurements on Edd (spoke calculator) and in a post by mrrabbit on these forums (which I can't link to because my account is new -- the title is "Sturmey Archer Dynohub "8 59" 32H Wheel Build Information FYI").

I plan to do 3-cross on both flanges (unless advised otherwise).

The spoke lengths I've come up with (and purchased) for this rim+hub+cross combination are:

• DS = 16x 296mm
• NDS = 16x 287mm

I assume the longer spokes on the larger flange (DS) is simply a typo, but the 9mm length difference is suspiciously small.
I roughly measured my 590mm Dynohub wheel and found 255 and 280mm spokes. The generator side is laced two-cross,
with three-cross on the other side, which must reduce the length difference a little.

This suggests that the problem is an error in spoke length.