I discussed this a while ago with FBinNY and he set me straight on the issue of spoke tension during braking. It's what allowed me to visualize what would happen with a wheel laced using the pattern discussed here.

The only reason a standard cross-laced hub does not experience torque during rim braking (or when simply sit on the bike) is due to the trailing AND leading spokes on both sides of the hub. Without those spoke forces countering each other, the hub will be torqued when displaced by any amount (though even at rest, without trailing and leading spokes on the same side the hub is being torqued).

Think of it this way:

Any force generated by the brake, is effectively balanced by the force generated by the friction at the contact patch between tire and road surface. It's a zero-sum game.

Basically, as far as the hub and spokes are concerned braking will "look" just like the rider suddenly became a tad heavier.

The braking force causes the rim as a whole to push back on the hub, this force is carried via the spokes. This force will cause the leading spokes at the top of the wheel to wind up whille the trailing spokes unwind, moving the rim to the leading spoke side.

At the bottom of the wheel the reverse is happening, so it moves to the trailing side. Net result is that the angle of the wheel to the hub changes with braking force = very bad handling characteristics.

I think it's half radial and straight pull spokes.

with radial spoking, you can't transmit any torque from the hub to the rim.

other patterns like crow's foot has some benefit, albeit minute

They don't refer to it as radial lacing but it sure looks like radial lacing to me: http://www.mavic.com/road/technologi...se.1.9395.aspx

You can transmit torque with a radially laced hub it's just that you are doing it by pulling straight out on the hub flange which isn't nearly as strong as pulling at some angle or, better yet, tangentially.

Draw a diagram (I sound like FBinNY talking to me a few months ago). Using this questionable lacing pattern on a rim braked bike will not cause the hub flange to twist as you have suggested during braking. What you are suggesting will happen if applying torque to one side of the hub (rear wheel or disc braked wheel). During rim braking, the leading and trailing spokes facing the back of the bike at the time will receive an increase in tension while the spokes facing forward will decrease in tension. This is due to the counter force being applied to the hub by the fork as it tries to slow the bike. However, what's different in this scenario from a standard wheel is the since there are only leading or trailing spokes on each side of the hub, the hub shell receives a torque as the spokes pull in opposite directions on the hub (whereas with crossed spokes, you'd have equal numbers of leading and trailing spokes pulling in opposite directions on the hub on both sides of the hub with a net torque on the hub shell equal to 0).

that's half radial there. The drive side is radial, the NDS is 2x

I think the source of your confusion is that they use straight pull spokes all around.
the NDS spokes, although going straight out of the hub, are offset so that the spokes are actually going out on a tangent.

You're right. I was only looking at the drive side.

Read my description again. We are in agreement, I never argued for a torque on the hub.

It is simply a matter of changing spoke tension with applied force. I actually think the problem is worse than I said becasue it would apply to the wheel simply supporting the weight of the rider as well.

Maybe I'm misunderstanding you. I'll try to phrase your argument in my own words and you can correct me where I'm wrong.

You are saying that during braking, leading spokes at the top of the wheel will increase in tension while trailing spokes will decrease. On the bottom of the wheel you are saying the reverse will happen (trailing spokes increase in tension, leading decrease). This change in the balance of tension will cause the dish of the wheel to change.

I disagree on all points except that a change in tension balance will cause the dish of the wheel to change. That much is true. However, the only way to create an imbalance in the tension of this proposed wheel would be to apply a torque to only one hub flange (as would happen on the drive side of the rear wheel or the disc side of a disc braked wheel). Leading spokes can do nothing to counter a torque applied to the hub that cause a tension increase in the trailing spokes. As a result, they lose tension.

However, when a person sits on a bike, the spokes pointing up increase in tension while the spokes pointing down decrease in tension. Similarly, during rim braking, the spokes pointing rearward increase in tension while the spokes pointing forward decrease in tension. Leading/trailing makes no difference in these scenarios. At any given time, there are both leading and trailing spokes pointing up, down, forward, and back.

Back to the proposed wheel. When a person sits on a bike with a wheel laced like that, the leading and trailing spokes pointing up will increase in tension. The difference between this increase in tension compared to a standard wheel is the lack of complimentary spoke pulling on the opposite side of the same hub flange (a crossed wheel will one spoke pulling up on the rearmost side of the hub flange while another spoke pulls up on the forward side of the hub flange and this is happening on both hub flanges). When one spoke is pulling up on the rearmost side of the hub flange while a spoke on the other side of the wheel pulls up on the forward side of the hub flange, the result is the hub shell shell getting twisted like a pretzel. Insert top and bottom of the hub flange for the forces happening during rim braking.

Thanks. That made perfect sense, and I could visualize it perfectly.

Torque does transfer, peeps; torque from pedaling goes TO the rim from the hub, otherwise we wouldn't move. Torque transfers from the rim to the hub, otherwise we wouldn't stop.

Don't see the OP's spoke-pattern idea working for a rear hub; the tire would rub the right stays under pedaling, and the left under braking, so such a degree that it would be like isometric resistance training.

Incorrect.

Don't know if I'm understanding you correctly, but the forces occuring in spokes and hub during (rim) braking are very similar to those experienced while JRA. While JRA the wheel has to carry its portion of the rider's weight in a pure vertical orientation, when braking this angle changes from the vertical to something pointing backwards, and the force increase somewhat. The amount the angle changes and how much the force increase depends on how hard the braking is. But basically the wheel don't see any difference between braking or a heavier rider coasting.

I don't know where to start.....

I've built hundreds and hundreds of wheels and spent many hours playing with "non-standard" spoke patterns......

Unless you are using purpose-built hubs like Mavic and others, there is an undeniable efficacy in symmetrical spoke patterns. Most hubs are not designed with flanges that can tolerate significant radial loads, nor are they designed to withstand significant twisting forces on the shell.

As a builder, my wheels stand up to the test of time and use because nothing I'm doing pushes the materials past what they were designed to do. This goofy hyper-twist design serves no purpose other than the gee-whiz-neato factor, and I seriously doubt you could get one up to proper tension and have it stay straight long enough to get any use out of it.

My daughter started hanging out with me at the shop when she was 8 years old and took her first look at a wheel I was building, paused a second and said... that's a 3 cross wheel with (pause) 36 spokes... and she started helping me lace wheels the same day.

She made no mistakes.

She can take dis-assembled parts, look at a complete version, and reassemble those parts perfectly and she likes to do all her own maintainence although she needs help pumping up tyres as she isn't big enough to get a floor pump over 45 psi as at that psi the resistance equals her weight.

She would tell you this is probably not a good idea and I would agree with her.

Good idea? No. Has it been done? Yes. If you want to do it to be different go for it, just be careful and try not to do anything to aggressive with it. I'd also use a thick bodied hub just in case.

The upper spokes on a wheel are not affected by the load. The bottom spokes tend to lose tension a a reaction to the load. A wheel stands on it's spokes as they are loaded in compression. If the load is great enough they will lose enough tension and collapse.

I'm sorry, but that is totally.......

LAME!

:lol:

btw, it's AN idea.:rolleyes:

Not sure where you got this from but it's wrong. The upper spokes are most certainly affected by the load. They increase in tension while the lower spokes decrease in tension. You'd have to stretch the upper spokes quite a bit to get the lower spokes to become completely loose. You'd need a rim failure to get them to collapse.

I'd put it down as being simplified rather than wrong.
Indeed they are, but the increase that they see in load is much less than the decrease in load seen by the spokes immediately below the hub. The difference is so big in comparison that one can argue that the load increase for the upper spokes aren't significant. (for a given wheel configuration of course.)

If starting from an otherwise sensibly configured and decently built wheel.

I agree with this, and would like to add that the upper spokes are trying to pull the top of the rim down, creating a flattened oval. This means that the spokes on the sides of the wheel (even those somewhat below the horizontal line, i.e. the 4 and 8 o'clock spokes) are also experiencing increased tension. The only spokes experiencing decreased tension are those between the 5 and 7 o'clock positions.

Correct.

Explain how that is possible. For a given force applied to the hub at the axle, the hub will deflect some amount relative to the centerline of the rim. This will result in an increase in tension for some spokes with a decrease in tension in other spokes. All spokes are starting out with tension applied and assuming a reasonably built wheel, will still have some amount of residual tension even with the decrease as a result of the load. How do you conclude that these changes will be so largely disproportionate that the increases can be basically ignored?

The rim displaces toward the hub. Spokes near the bottom lose tension. The tiny amount of tension gain in the upper spokes is due to the rim losing its round shape. Jobst Brandt's book explains this quite well.

Yes, Brandt's book explains this. Tension decreases in just a couple spoke at the bottom. All the other spokes experience either a slight increase in tension or no increase in tension at all. Any deformation in the shape of the rim -- that is, deviation from the round shape -- requires a change in spoke tension where the deviation from roundness occurs. Because most spokes see little or no change in tension, it follows that little or no deviation from roundness occurs except at and very near the bottom. My recollection from his book is that Brandt determined this both through very careful measurements of actual wheels and also through finite element anlaysis modeling.

Assuming which rim? I can see how a change in roundness would affect tension but I'm skeptical that any decent rim would see that big of a displacement along the bottom (especially given that there is a tire/tube distributing the load).

The spokes at the top must also see an increase in tension from the applied load. The rim losing it's round shape near the bottom should mostly affect those spokes near the deformed area.

The primary displacement of the rim is at the bottom, where it contacts the tire which contacts the ground. No matter the rim, this happens, though it's very small (rim strength obviously controls the amount of displacement). The rest of the rim will sort of 'warp' but much less so than at the bottom. The lower spokes take the most of the load. The other spokes change in tension due to the 'warping'. I really can't explain it that well but Brandt has good drawings of the displaced shape of a rim due to all sorts of loading.

Quite obviously, if the tension in some spokes decreases, the tension in other spokes must increase. But, only a few spokes at the bottom decrease in tension so you've got 7 or 8 times as many spokes that do not decrease in tension. Then there is the fact that the strength of the rim resists change of shape. That is, some of the decrease in tension in the spokes at the bottom is countered by changes in compressive load in the rim. The net result of al this is that the increase in tension in the spokes at the top is slight and is dwarfed by the decrease in tension at the bottom. As Brandt put it, the hub does not hang from the top spokes as traditionally described, it stands on the bottom spokes.

Why the hell should I. The idea like you is bull****.