wheelbuilding problem (darn....)
 

Darn....

Let me start by saying I have build about ten wheels to date, over the last year or so. I feel like I have been pretty successful and I am getting the hang of it. Wheelbuilding has become something I enjoy.

Lately I've taken to buying/finding single vintage 27” rims, pairing them, and building vintage wheel pairs (usually with a decent pair of old Normandy or other high flange hubs). I feel like I have made something special out of junk.

So recently I laced up two old (but nice) Rigida double-wall rims. The front went together nicely and is now finished.

The rear, another story. I laced it up, tensioned, dished and trued. This time I built it tighter than I usually do. Right as I finished, I grabbed the rims and flexed them some to make sure the spokes were seated OK and the next thing you know I'm looking at a wheel with a severe potato chip shape, maybe an inch plus out of true.

What did I do wrong? Did I build it too tight? The rim seemed perfect before I built it up, straight, round and never before laced. I did de-tension it but it has retained the potato chip shape. I used double-butted spokes for the first time, usually I have used straight gauge spokes.

And the rim. When I disassemble it, if it is that out-of-true, is it ruined?

Darn....

(hey anybody have an old Rigida blue label double-wall clincher rim out there?

Argghhh...

Been there, done that. "Tighter than usual" sounds similar to what I did. And what a sense of dismay when you stress relieve, notice it went out of true, try to fix it with the nipples, and it just gets worse.

I think I was less gradual and more aggressive tightening the spokes on the build that tacoed. I'll never make that mistake again.

I actually unlaced my rim, bent it back by supporting the rim at the low points with blocks and carefully but firmly leaning on it. Then I rebuilt the wheel. The wheel is tight and true now. But it still hasn't been ridden yet, so I don't know if it will be durable (I hope so!). And I'm far from an experienced wheelbuilder (your wheel count in fact exceeds mine), so perhaps someone else will chime in.

The spoke tension on the drive side spokes will be higher than the non-drive. If the differential between them is not correct (generally to high on the non-drive spokes), you end up with a wheel chip.

Rear wheels seem to come out better if you work at the tensioning and truing, dish and round all together, as first phase of the truing operation. I bring the drive side to a rough even tension(soft) and then go to work around the wheel a 1/4 turn - 1/2 turn at a time. The final tweaking, after initial tensioning, will be one small area at a time, remembering that every turn on on spoke is offset somewhere else on the wheel. I tend to work on one area and them spin the wheel to look for any changes, using no more than a 1/4 turn at a time(usually it is more like 1/8 turn) especially as you get toward final tension.

Check out "The Wheel Book " by Jobst Brandt, an industry standard.

Good luck.

I don't think his problem has to do with tension...at least not completely;) I'll bet you dollars to donuts (Gee, Brain, if everyone used donuts wouldn't their wallets be all squishy?) that his spokes are laced asymmetrically. That puts uneven tension on the rim and can pull the rim to one side resulting in the classic taco shaped wheel. Trailing and leading spokes should have the heads pointing at one another for each side.

Additionally, seat the spokes, timin8r, before you start to tension the wheel. I use a large screw driver to bend the spokes to conform with the hub while they are still loose. It's the second thing I do in wheel building after lacing. Sheldon Brown used an old crank arm. He did his late in the tensioning. I do it right up front.

Ouch!

Yes. If it hadn't tacoed at flexing it probably would have tacoed at first ride.

Don't blame the spokes, blame the tension they were carrying.

Yes, no, maybe...

I've also done what Flycrash describes, disassembled, straightened and reassembled with good results. But those wheels have all been degraded to beater/commuter status, which maybe isn't the most taxing of applications.They've held up to that w/o problems though.

When I have done such an exercise I've locked the spokes together at the crosses with a small strip of tape before removing the rim. Makes the reassembly much simpler not having to go through all the steps of the lacing again

The rim doesn't care much about where the spokes are anchored at that stage - unless he's bringing some spokes to tension way before the others by giving all nipples equal turns and a flawed lace pattern has left him with some spokes effectively shorter than the others. But lacing with wrong spoke lengths like that usually only means that the wheel goes out of true. To get (residual) tacoing you've got to have overtension or an outer force.

How would you get that to work? Spoke holes are "always" offsetfrom one flange to the other. Go through any spoke hole parallell with the axle and you end up smack in the middle between two spoke holes on the other side. Either they're always facign each other or they're never facing each other, for any X pattern.

Thanks all for the comments.

I did build the wheel pretty darn tight, tighter than any wheel I've built to date. Those spokes, particularly the drive side, sang a high note I could never reach!

I've read/reviewed two or three books and the last one was the Musson book you can get online. He says that most wheels are not built tight enough. So I built these tighter. He also says he never uses a tensiometer. So I didn't. I guess I'm not yet experienced enough to build wheels “by ear.” By the way I think that book is the best I have seen so far.

From the previous posts, I believe I did everything pretty much right. I learned by wheel #2 to always take quarter-turn baby steps so that I don't build a taco right from the outset. As I increase tension, I move between lateral truing, radial truing and dishing, with an occasional foray into equalizing spoke tensions a touch. I also (as Musson suggests) remove the outside-spoke “bow” very early in the process, which is what I believe cyccommute is recommending. Especially lately, I have built some darn good wheels.

I don't understand the “asymmetric lacing” comment. The wheel was a classic three-cross, and I always double-check the lacing (over-over-under, etc.) before I start tensioning in earnest.

Man I had this thing really dialed in. Almost perfect. Spent a lot of time on it. Except I guess it was too tight. If only I had backed off a half-turn a couple times around. Darn....

The “taping” suggestion is a good one. I'm gonna tape the nine spoke bundles together and remove the rim. And probably look for a replacement, if I can't easily coax the rim back into shape. I really don't wanna chance me or anyone riding on an inferior wheel. The old Normandy hubs matched and I want the rims to match, besides the spoke lengths are for the old 27” Rigida blue label but probably not much else.

Not that it matters, but this is the first wheel set that I measured myself in order to determine the spoke lengths. You know, the rim diameter and the hub measurements. And I believe my spoke lengths were spot on. It worked out really well.

I'm chalking this one up to experience. Really, with the few wheels I have build myself, it's pretty clear that books are books but experience is the best teacher. And I thought the same thing that dabac mentioned. If I had not taco'ed the wheel by flexing it, it almost assuredly would have taco'ed on the first ride.

An asymmetrical wheel is one where the spokes for either trailing or leading spokes are all fed from the same side. Old machine built wheels were done this way since the machine wasn't sophisticated enough to feed spokes from either side. It's a common newbie mistake also. It results in a wheel that has uneven tension...much like using two different length spokes...that is prone to tacoing.

You are being too literal. Take two spokes that are on opposite sides of the wheel but are doing the same job, i.e. both are trailing or leading. They should be mirror images of each other. If one head faces in, the other side will also face inward. If the head of one faces outward, so will the other. For example

http://www.chrisking.com/prettyandst...ront_wheel.jpg

If the spokes aren't like this but instead have the heads facing in the same direction, you can end up with an unstable structure since the forces on the heads are pulling the wheel towards one side. Put a little sideways force on it and the wheel will settle into a nice low energy state that looks like a potato chip:eek:

It was very common in the 70s and 80s to have this happen. That's part of the reason I started building my own wheels.

Left flange trailing & inbound + right flange trailing & outbound = asymmetric, OK, gotcha.

But uneven tension is "all" about sloppy building, and very little about spoke length or spoke orientation. If you lace any X pattern and have the outbound spoke crossing underneath the inbound you're pretty much cancelling the effect of the spokes leaving the hub one flange width apart.
Assuming both leading and trailing are still under tension an outbound spoke passing under the inbound at last cross will act on the rim as if it's axis was anchored 1/2 spoke dia to the inside of the middle of the flange. I can't see that tiny difference doing anything significant unless something else is causing the spokes to go slack, and maybe not even then.

But that isn't much of a problem either, as long as you are within the working span of the nipple/thread interface, i.e. enough threads engaged and not bottoming out. But sure, it you run out of threads before reaching proper tension, then you're in trouble.

what the buck?

Just trying to be helpful...

Don't like it when people qualify their ideas in the interest of honesty? Suit yourself.

This uneven tension is different from what you'd get from sloppy building. Instead of the force vectors on each pair of spokes canceling each other out, the force vectors pull in the same direction. Put a little sideways force on the wheel and everything will seek a lower energy state...which looks a lot like a potato chip:eek:

When I built my PowerTap rear, I was raising the tension, then started noticing that it was going out of true. I tried to fix these spots by truing just with more tension (I was still trying to get the tension up a bit).

After I trued about two spots, I noticed that other areas were now WAY out of true. Then I realized that I must have gone beyond the rim's max tension. I spun the rim in the stand, and it was doing a 1" hula dance. F@ck.

Ok, so I backed off the tension, 1/4 turn at a time, all the way around. Sure enough, the rim went almost completely true. I evened the tension out from my previous truing attempts, and brought the rim back up to tension. I left it about 10kgf lower, and it came together fine.

I've ridden it about 2500 miles in four months, neither the true nor the tension have changed at all in that time. I believe the NDS is about +/- 3kgf on tension.

So, all is not lost. It will probably be fine.

Do you have any data to support that? Or maybe some finite element analysis or even a free body diagram? Or did you just make it all up?

The spokes "pull" the rim only in a direction parallel to their own axis. Heads in or heads out doesn't change the direction of that axis very much, if at all. It may change the distribution of forces at the hub flange, but flange failures are not very common, and not the cause of the OP's problem.

em

Assuming it's an X pattern, equal tension and that you do the outbound-under-inbound thingy at the outermost cross the direction of the pull axle will differ one spoke diameter between leading and trailing spokes. I have a hard time believing that it would have a significant influence on wheel strength or rigidity.

Nope. I've just seen a lot of potato chipped machine built (even some handbuilt) OEM wheels that were laced asymmetrically. Nobody does it that way any more so it not as common a problem. It can be a newbie mistake, however.

I have seen discussions of the problem in print but that was long ago and, like I said, it's not a common practice now.

The lacing may not be the issue either. I don't think it has much to do with how tight timin8r tensioned the spokes...I make very tight wheels myself...it may have more to do with not seating the spokes prior to tensioning the wheel and then flexing them when the wheel is tight. Once twisted, I'm not sure I'd use the spokes or the rim.

Sorry, timin8r. You may have learned a very expensive lesson.:o

But outbound-under-inbound at the outer cross reduces the effects of heads-out and heads-in significantly. You've got an offset between leading and trailing spoke of one spoke diameter at say 2/3 of the spokes length from the rim. That's a tiny, tiny vector to blame a collapsed rim on.

cyccommute....

I don't agree, at least not yet, that I have learned an expensive lesson. If I do learn from this and not repeat my mistake, whatever it was, it will have been worth the cost of a rim and some spokes. My wife is a Montessori teacher and my girls are Montessori students. Their “mentor” has a saying - “If you can't be right, be wrong.” Truer words....

But I'm still not 100% sure what I did wrong. Yes I built the wheel tight, probably quite tight, and it was a vintage (aka "old") rim. What I want to know is this, as specifically as you have time for. What steps do you take to “seat the spokes” prior to tensioning?

After I laced the wheel, and basically got it to where the threads had just disappeared under the nipples, I put on a pair of stout gloves and pushed the outside spokes with my thumbs so they were straight, not bowed. Also, many times, before and during tensioning, I put on the gloves and massaged (squeezed) the spokes bunches. Sometimes I heard the “tinking” of a spoke head moving into position. Sometimes not. What I did not do, until the very end, was to flex the rim. Should I have done this as well? I guess I feel (felt) like what I had done was sufficient, and that flexing a barely-tensioned rim would not have much of an effect, certainly not as effective as what I was already doing.

Also, to address what waterrockets said, and by way of additional information, up until the time i flexed the fully (overly?) tensioned wheel, I never had a problem truing it. Additional tensioning always made it better, never worse.

I was at my LBS last night and discussed it with one of the fellas there. He said it sounded like it was over-tensioned and “it's always better to error on the side of a little too loose.” I'm not sure I agree with that.

Sounds to me that you over tensioned the wheel. Jobst Brandt says in his book:
What do you mean by "seat the spokes"?

Sounds good, also grab two spokes that cross and squeeze. This will get a good spoke line.

The tinking was most likely because the spoke was not unwound all the way. I don't flex the rim. I think it is very hard to determine if all the spokes were stress relieved. It can be a good way to unwind the spokes, I prefer to do it while tensioning. For stress relieving, I prefer to grab parallel spokes and squeeze.
I believe waterrockets is correct. There is a max tension. Once that is reached you will get waves in the rim. The tension needs to be backed off, as mentioned above by Brandt.
I agree about not to error on the side of too loose. You might not have the wheel as tight as possible, but not too loose.

I also think it's better to have the spokes too loose than too tight, except maybe with double eyelets. Overtensioned spokes will wreck the rim, sending you over the handlebars, while loose spokes will just start breaking, giving you enough warning to stop the bike before the wheel stops turning.

Every wheel I have is laced "asymetrically," except for the radial. So far they are all pretty stable. Spoking the wheel all heads-in or all heads-out probably has more to do with the type of machine used to lace the wheel than with the ultimate strength of the wheel.
Do you have a reference?
"Not seating the spokes" may cause the spokes to fail at the hub, but only after there has been enough use to cause fatigue. It will never cause a rim failure.

Folded rims are caused either by too much static tension in the spokes, or by too much lateral load. A wheel with insufficient tension is susceptible to folding from lateral loads while riding.

em

+1

+1

Some old rims flex too much.
They are OK for the front wheel, but quickly go out of true in the rear.
It's especially noticeable when you use double-butted spokes because they can stretch more.