View Full Version : problem with spoke length
bitt3n
05-31-2017, 08:07 PM
I'm building a rear HED Belgium wheel with a CK R45 disc hub and 290mm spokes on the non-drive side recommended, and I'm having trouble getting the spokes to reach the nipples on that side. I rounded down from the 290.8 mm recommended by the spoke-length calculator. That seems to have been a bad idea.
I'm doing the first set of 7 spokes on the non-drive side and the last three are maybe 1mm too short. I tried unscrewing the nipples on the opposite side until the spokes were almost falling out, but that didn't seem to help. I'm using 12mm nipples. Should I switch to 14mm nipples? Or should I get 291mm spokes?
Black Dog
05-31-2017, 10:28 PM
Get 14 mm nipples. Way cheaper and easier at this point.
Something sounds fishy. You should not have a problem with the initial lacing even if the spokes are 2mm too short. I am assuming this not your first build? You should start with just a few treads into the nipple, then tighten once it's all laced up.
foo_fighter
06-01-2017, 12:35 AM
I agree, something doesn't add up.
How would 14mm nipples help?
The threads are the same on Sapim and Wheelsmith 12mm vs 14mm nipples .
Even if you got 16mm DT nipples and got the spokes threaded, you would end up with a weaker wheel:
http://sheldonbrown.com/images/dt-threads.jpg
Louis
06-01-2017, 01:09 AM
How would 14mm nipples help?
They help if you're willing to have the end of the spoke be farther "down" the axis of the nipple.
Clearly the closer it is to the rim seat the better your load transfer will be, but since the first few threads of engagement take the majority of the load, and almost none if it is taking place at the end ("top") of the spoke, you're taking load through the body of the nipple anyway, so having a slightly shorter spoke in a slightly longer nipple isn't the end of the world.
bitt3n
06-01-2017, 01:28 AM
Something sounds fishy. You should not have a problem with the initial lacing even if the spokes are 2mm too short. I am assuming this not your first build? You should start with just a few treads into the nipple, then tighten once it's all laced up.
It is my first build so I could easily be doing something stupid. I've only been using a few threads to start. The drive side seems fine (at least, it was easy enough to lace), but as soon as I put a single spoke in the non-drive side the entire hub moves off axis toward the installed spoke, suggesting it's too short.
Here's the wheel with the valve at 12 o'clock. The first non-drive side spoke is installed to the left of the valve.
http://i.imgur.com/Cmfmmz8.jpg
Here's a closeup of the threads. You can see the nipple is barely screwed on
http://i.imgur.com/mvTngGR.jpg
You can't really see it in the picture, but the hub is off axis toward the installed non-drive spoke (up), even with the nipple barely screwed on. When I work my way around the non-drive side, the spokes on the other side of the wheel are impossible to get in the nipples.
http://i.imgur.com/tFpz46o.jpg?1
Here are the calculations that led me to get 291mm spokes (I rounded down from 291.8 mm, following a few suggestions always to round down, but I think this was not wise):
http://i.imgur.com/tzsKoBW.png?1
The only thing that I find a bit puzzling is when I go to double check the stated measurements in the CK manual that came with the hub, that page has been crossed out by hand with magic marker for some reason. (Also there's no distinction between the centerlock and six bolt R45D in that spoke calculator. I'd assume it wouldn't matter and the CK specs suggest it doesn't but then I wonder why the pages are crossed out.)
I agree, something doesn't add up.
How would 14mm nipples help?
I didn't realize the threads are the same as with 12mm, so I guess they wouldn't.
Louis
06-01-2017, 01:33 AM
Have you double-checked the ERD and the hub measurements?
bitt3n
06-01-2017, 01:51 AM
Have you double-checked the ERD and the hub measurements?
The ERD is the same that HED reports.
I notice that the CK Manual (https://chrisking.com/files/public/content/media/document/4/8/r45_r45disc_manual_12_21_16.pdf) has a value of 33mm for the center to flange non-drive side measurement of the R45 Disc Centerlock rear hub, whereas the calculator has 35mm for that figure (which is the correct value for the non-disc R45).
That seems like it would cause the spokes to be slightly too long rather than too short (and only very slightly).
As for the other measurements, the spoke calculator rounds them all to the nearest mm but aside that they appear accurate. (Setting aside that in my paper manual the measurement pages are crossed out.)
jc031699
06-01-2017, 03:59 AM
Something looks wrong with the lacing.
All of the heads out spokes from the near flange on the photo should be pointing the same direction.
Same for the heads in spokes on the near flange - opposite direction.
paredown
06-01-2017, 05:40 AM
I hadn't built a wheel for thirty+ years, and had to get retrained this week. Finished a front (always a bit easier).
The instructions for procedure on Sheldon's page are the best. Especially with rears, it is important to start in the right spot:
http://www.sheldonbrown.com/wheelbuild.html?iframe=true&width=100%&height=100%
The other thing I see--you have the same problem that I was having--slightly beefier walls on the hub flange and/or a slightly shallow 'J' on the spoke, and the spoke doesn't want to lie flat against the flange as you put it into position--I would be interested in what the 'pros' here suggest to get them to lie flat.
ergott
06-01-2017, 06:32 AM
The issue here is you rounded down instead of up.
When you have a large flange on the non drive side, the crossing spokes don't take as straight of a path to the rim. In fact, you have to tighten the heads out spokes about half turn or more to get the tension to be the same as the heads in spokes. Heads in spokes have to basically wrap around the flange before straightening out to the cross of the other spoke, then back on its way to the the rim.
When I build CK hubs (and others like it) I actually add 1mm to the result and choose my length accordingly. On the drive side it's much less of an issue.
If you were to build large flange track hubs like Phil Wood, you have to consider the same issue all around and definitely round up, not down.
I would definitely not use longer nipples to try and fix a bad build. That's how they break. The threads in the head of the nipple are the only ones that really count for wheel strength.
oldpotatoe
06-01-2017, 07:10 AM
I'm building a rear HED Belgium wheel with a CK R45 disc hub and 290mm spokes on the non-drive side recommended, and I'm having trouble getting the spokes to reach the nipples on that side. I rounded down from the 290.8 mm recommended by the spoke-length calculator. That seems to have been a bad idea.
I'm doing the first set of 7 spokes on the non-drive side and the last three are maybe 1mm too short. I tried unscrewing the nipples on the opposite side until the spokes were almost falling out, but that didn't seem to help. I'm using 12mm nipples. Should I switch to 14mm nipples? Or should I get 291mm spokes?
Hard to tell from the pix but I'm guessing a lacing error. Wrong hole in hub to wrong hole in rim, over one too far or something. .4 or .7mm shouldn't make that big of a difference.
I think it's easiest to install all drive side pulling spokes, 7 in your case, turn wheel over, all NDS pulling spokes. First spoke in hub in hole 2 to the right of the valve hole, first on NDS is next to valve hole, between DS spoke and valve hole. . Turn wheel over again, then rotate hub clockwise and install crossed spokes drive side, over again, NDS spokes..easier to have in proper holes.
ergott
06-01-2017, 08:01 AM
Are you lacing your key drive spoke to the right of the valve hole?
Mark McM
06-01-2017, 09:55 AM
Clearly the closer it is to the rim seat the better your load transfer will be, but since the first few threads of engagement take the majority of the load, and almost none if it is taking place at the end ("top") of the spoke, you're taking load through the body of the nipple anyway, so having a slightly shorter spoke in a slightly longer nipple isn't the end of the world.
The concept of the stress being concentrated on the first few threads is true for "traditional" nuts and bolts - but spoke nipples aren't traditional nuts. Because the threads of the nipple are below the head, the threaded section of the nipple is stretched instead of compressed, which acts to spread the load more evenly across the length of the threads. In addition, the modulus of brass nipple is only half the modulus of a steel spoke, which would tend to concentrate the thread stresses further up the shaft of the nipple. The worst case is for aluminum nipples (modulus only 1/3 or steel), where the thread stresses are concentrated closer to the spoke head. For aluminum spokes, running the spoke all the way through the head really does improve the durability of the spoke.
bitt3n
06-01-2017, 10:14 AM
When you have a large flange on the non drive side, the crossing spokes don't take as straight of a path to the rim.
That seems like it would affect the spokes with the heads on the inside of the rim, so the spoke has to reach around the flange to get to the hole. In my case, the only non-drive spoke that I've attached to the rim has the head on the outside, so it doesn't appear that the flange is getting in the way.
Are you lacing your key drive spoke to the right of the valve hole?
I followed this video (https://www.youtube.com/watch?v=OYl4NO5m16Q) for the drive-side and the same guy's second video (https://www.youtube.com/watch?v=8NJwEcm-NTw) for the non-drive side exactly, and just reviewed it to make sure. The three-cross pattern looks fine, each spoke under the first two and over the last one, exactly like his wheel.
You can see at this point (https://youtu.be/OYl4NO5m16Q?t=112) in the video that (with the drive-side facing up) he puts the drive-side key spoke into the hole on the left of the valve. He does this because that hole is directed toward the drive side.
As far as I can tell the HED rim's holes all run down the centerline rather than being angled one way or the other like the rim he's using. I just followed his procedure exactly. With the non-drive side facing up (as in my picture), the first spoke I laced to the drive side is on the right of the valve, and the first spoke I laced to the non-drive side is on the left of the valve. The spokes on either side of the valve are parallel, which looks correct from the video.
Which spoke to use to start the lacing on the non-drive side seems pretty obvious from his explanation (the spoke on the on the non-drive side that's opposite the key spoke on the drive side), so I don't think I've made a mistake there. Up until I add the first non-drive side spoke everything looks symmetrical, but when I add that spoke the hub shifts its axis toward the added spoke.
If there's any additional picture I could take to help clarify what might be the problem, definitely let me know. The drive-side spokes are all quite loose, nothing seems weird there.
Something looks wrong with the lacing.
All of the heads out spokes from the near flange on the photo should be pointing the same direction.
Same for the heads in spokes on the near flange - opposite direction.
I just taped all the loose spokes on the non-drive (near) side together to get them out of the way. There's only one non-drive spoke actually in a hole, the one extending up to the hole left of the valve stem. The key spoke on the drive side is to the right of the valve stem, with the two spokes parallel, and the rest of the drive-side three-cross pattern looks right as far as I can tell from the video, though I'd be happy to be corrected.
Mark McM
06-01-2017, 10:33 AM
From the photos, it looks to me like you've laced the NDS spokes offset by 1 spoke hole. The first NDS spoke laced to the rim (just to the left of the spoke hole) is a pulling spoke, and at the rim it is laced one hole clockwise from the corresponding DS pulling spoke at the rim - but it the hub it appears to be laced one hole counter-clockwise of the same DS pulling spoke.
Normally, the DS and NDS spoke angles (pattern) should be identical, but the pattern on each side should be rotationally offset by 1 spoke hole - and obviously they should be rotationally offset in the same direction at both ends of the spoke.
R3awak3n
06-01-2017, 11:21 AM
I highly recommend this book
http://www.wheelpro.co.uk/wheelbuilding/book.php
its cheap, you get it instantly and it just makes lacing wheels so so easy.
I agree that there is a lacing mistake, 1 mm will not matter than much and I usually round down myself when its not too much (and since I usually buy my spokes through a place that only does even spokes).
bitt3n
06-01-2017, 11:43 AM
From the photos, it looks to me like you've laced the NDS spokes offset by 1 spoke hole. The first NDS spoke laced to the rim (just to the left of the spoke hole) is a pulling spoke, and at the rim it is laced one hole clockwise from the corresponding DS pulling spoke at the rim - but it the hub it appears to be laced one hole counter-clockwise of the same DS pulling spoke.
Normally, the DS and NDS spoke angles (pattern) should be identical, but the pattern on each side should be rotationally offset by 1 spoke hole - and obviously they should be rotationally offset in the same direction at both ends of the spoke.
This looks like the correct answer. Once I moved the NDS spokes one hub hole over everything looks okay. If anything I'm surprised how loose the spokes are (though they're all barely threaded on, so hopefully that's normal).
Next time I need to be more careful about putting the first NDS spoke through the hub hole directly opposite the DS key spoke.
http://i.imgur.com/7VW04SE.jpg?1
Mark McM
06-01-2017, 12:36 PM
If anything I'm surprised how loose the spokes are (though they're all barely threaded on, so hopefully that's normal).
Yeah, that's normal (and a good thing, as it makes it easier to star the spoke threads). The spokes have about 10 mm of threads, so when the threads are first started the spokes will have several millimeters of slack, making them quite loose. As you tighten the spokes so the ends approach the tops of the nipples, you should find the spokes tautening up quite nicely, and the wheel starting to become quite rigid.
ergott
06-01-2017, 12:56 PM
Looks good.
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