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I'm no engineer, but I have always wondered why track hubs have high flanges.
 

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Mostly tradition

Pablo said:
I'm no engineer, but I have always wondered why track hubs have high flanges.
In the olden days, it used to be believed that high flange hubs made for a stiffer, stronger wheel. But later it was discovered that flange size has little do with wheel strength, and in fact high flange hubs can be a disadvantage (the spokes take a steeper entry angle into the rim, increasing spoke breakages at the threads).

The reason track wheels have stuck with high flange hubs is largely due to tradition, but also due to the small advantage that a spoke can often be changed on the drive side without having to remove the sprocket (this is a very small advantage, however).
 

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i duno..

people are always talking about how you want a wide hub to make the wheel stronger.. besides, for about 1cm of difference, were talking at most, about 6 degrees (264 spoke length, 245 avg straight length)

you need it wide to keep the wheel from pulling side to side..

and that im using a mtb hub, arnt the road bike rear hubs 35mm shorter?

do you have any proof?
 

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Just to add I heard from an old trackie that high flange hubs also help when building a wheel in a 4 cross pattern.. the spokes don't ride up over the heads of neighboring spokes.

The laterally stiffer argument has been debunked by lab tests but that was the belief.
 

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Flange height and flange spacing

tamu said:
i duno..

people are always talking about how you want a wide hub to make the wheel stronger.. besides, for about 1cm of difference, were talking at most, about 6 degrees (264 spoke length, 245 avg straight length)

you need it wide to keep the wheel from pulling side to side..

and that im using a mtb hub, arnt the road bike rear hubs 35mm shorter?

do you have any proof?
Yes, it's absolutely true that wider flange spacing makes a (laterally) stiffer and stronger wheel. But the flanges on high flanges are simply taller, not more widely spaced. The important variable is the angle of the spokes to the rim. Making the flanges taller has little affect on the spoke angle. A wheel with short, widely spaced flanges will be stiffer and stronger than a wheel with tall, narrowly spaced flanges, because flange spacing has a much greater affect on spoke angle than flange height.
 

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Mark McM said:
Yes, it's absolutely true that wider flange spacing makes a (laterally) stiffer and stronger wheel. But the flanges on high flanges are simply taller, not more widely spaced. The important variable is the angle of the spokes to the rim. Making the flanges taller has little affect on the spoke angle. A wheel with short, widely spaced flanges will be stiffer and stronger than a wheel with tall, narrowly spaced flanges, because flange spacing has a much greater affect on spoke angle than flange height.
both are equally important on angle of the spoke, and both affect it just as much..

assuming length from the hub to rim (perpendicular to hub) is 255, hub is 135mm spacing..

gives us an angle of 75

now, we use a "track hub" lets say its 1cm bigger radius, that makes it 245mm from rim to hub, hub is? 100mm,

that make it an angle of ~78


these angles arnt correct because the spokes arnt radial laced.. but you cannot argue that hub spacing, wheel diameter, and flange diameter all play equally important roles in spoke angle.

if you want to argue that shorter spokes do not increase strength over longer spokes, fine

but you cannot say that because hubs with high flanges cause a larger angle to the normal vector of the inside of the rim, that this weakens the rim


although i cannot test this, it seems wrong, i cannot say they are absolutely true, because most 135mm spaced hubs also have a casset leading to dish..
 

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Garbage in, garbage out

tamu said:
both are equally important on angle of the spoke, and both affect it just as much.. ..
No, they are not equally important. Because the angle of the spokes is so steep, every millimeter of change in lateral spacing has a much greater affect than a millimeter of change in radial spacing, as we shall see below.

tamu said:
assuming length from the hub to rim (perpendicular to hub) is 255, hub is 135mm spacing..

gives us an angle of 75..
It looks like the value you used for flange offset is incorrect. A typical 135mm rear hub has a left flange offset of about 30mm and a right flange offset of about 25mm. This gives angles of 83.3 degrees on the left side, and 84.4 degress on the right.

tamu said:
now, we use a "track hub" lets say its 1cm bigger radius, that makes it 245mm from rim to hub, hub is? 100mm,

that make it an angle of ~78 ..
Using the more realistic smaller flange offsets, the angles change to 83.0 degrees and 84.2 degrees, left and right respectively. In other words, an average change in angle of 0.25 degrees - hardly worthwhile.

On the other hand, lets see what happens if we were to move the flanges 5mm outward (35mm left and 30mm right) instead of increasing the flange radius. Using the original 255mm spokes, the left spoke angle becomes 82.2 degress, and the right spoke angle becomes 83.3 degrees, or an average of 1.1 degree difference. So you get more than 4 times the difference in angle with only half the change in distance of the spoke ends - which makes flange spacing about 8 times more important than flange diameter.

Of course, even though there appear to be small gains with increase in diameter of the flanges, there are practical reasons that you can't achieve it anyway. On dished rear wheels, the limit on wheels strength is the dishing, required to fit a cassette on the right side of the wheel. The limit of the spoke angle is determined by the clearance between the spokes and the derailleur, so you can't increase the spoke angle beyond a certain point without interfering with the derailleur cage. This limiting angle can be reached with either a large or small diameter flange. So once you've sized and positioned the flange at this spoke angle limit, the actual diameter of the flange becomes moot.


tamu said:
but you cannot say that because hubs with high flanges cause a larger angle to the normal vector of the inside of the rim, that this weakens the rim.
So then it's a good thing that nobody did say that. However, when you cross the spokes, the spokes enter the rim at a sharper angle, so there is more bend in the spokes right at their weakest point (the threads), so larger flanges do increase the chances of spoke failure at the threads.
 

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yes, my numbers were off, didnt think about spacing until i got to class..

things have been really hectice these past few days.. the rim i was using for compareson thinking is my surly-alex dx32, single speed and no deraileur..

i was not thinking about the angle of the spoke vs radial vector, but the angle between the spoke and the perpendicular of the hub

looking at my wheel, i see there is an angle to worry about, but that didnt cross my mind.. I guess i was thinking more along the lines of a radial lace to simplify it.

if you lace your wheel radially, or (2x might reduce this angle as well) a very high flange hub would make no difference.. (front wheel)

when it comes to strength, and you lace 3x or something, the only angle that would compromise the rim is the angle between the radius and the spoke.

this angle is arctan(hub radius/249)

does it really make that much of a difference compared to the side to side angle of

arctan( (flange seperation /2) / (249) ) (even though the holes are offset some, making this angle less)

btw, the diameter on surly is 58mm
 

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the guy who said shorter spokes was partially right

High flange hubs were popular when spoke steel was not so good; that is - shorter spokes make less flexible and stronger wheelb hence the need for high flange hubs.

These days it is all bunk....spokes are manufactured to the highest degree and tolerances and the need for high flange hubs is kaput. That said...I use 'em. Me thinks they look kool.

vtw
 

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High flange hubs were always bunk

victorthewombat said:
High flange hubs were popular when spoke steel was not so good; that is - shorter spokes make less flexible and stronger wheelb hence the need for high flange hubs.

These days it is all bunk....spokes are manufactured to the highest degree and tolerances and the need for high flange hubs is kaput. That said...I use 'em. Me thinks they look kool.
Speaking of bunk -

For wheels with 3x or 4x crossed lacing, the spokes are only about 1% shorter with high flange hubs - not enough to make significant difference in stiffness. And the wheels are no stronger - in fact, they are potentially slighly weaker, since the spokes take a sharper angle into the rim, causing a higher stress concentrations at the nipples.

People may have thought high flange hubs were stiffer and stronger, but this is really just another cycling myth. The only good reason for high flange hubs is when the additional clearance is required for internal mechanisms (internally geared hubs, power measuring hubs, etc.) or for hub brake mounting (disk & drum brake hubs).
 
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