The earlier statement " Lateral bending[email protected] said:Dave Ornee writes:

>>>> <SNIP> Lateral bending strength of deep aero rims, that can bridge

>>>> large spoke-to-spoke distances for vertical loads, is not

>>>> significantly higher than rectangular cross section rims, their

>>>> width being the same.

>>> Can you explain more of what you mean here?

>>> Are you talking about 19 mm wide 21mm tall rim (as an example of a

>>> regular cross section rim) having the not significantly higher

>>> lateral bending strength as a 19 mm wide 30 mm (as an example of not

>>> a very deep aero section) rim when built into a wheel?

>> The radial depth of, for instance, an MA-2 is 1/3 that if a typical

>> aero rim (over 40mm) (for which we need to buy inner tubes with extra

>> long valve stems).

>>> I will wait for your explanation before jumping the conclusions, but

>>> I would like you answer to include how spoke support angle plays

>>> into this as well as other factors of physics.

>> I don't know what you mean by "spoke support angle". Spokes come in

>> pairs both laterally and circumferentially so their angles are

>> balanced. This concerns radial loading. The depth of an aero rim

>> furnishes bridging strength, the bending strength of a bean going as

>> the third power of its depth.

> "Spoke support angle" = Spoke bracing angle. I don't know what you

> mean by "their angles are balanced". This isn't of particular

> interest to me, but I sure don't see that in the angles of spokes

> left Vs. right in rear wheels. I understand that the force vectors

> must be balanced.

For rear wheels with offset, spoke tension is different for left and

right sides by the sine of the angle.

> It is my understanding that:

> 1. The bracing angle or "spoke support angle" increases as the height

> of the rim increases.

There is no connection between the two parameters. Only thew radial

distance from hub to spoke end in the rim affects that angle and the

percentage difference over the length of a spoke is small. I still do

not see what you are proposing.

> 2. The higher the "spoke support angle" the stiffer the wheel

> latterally; all other things being equal.

As I said, that goes as the sine of the angle and that is a small

number. Far more significant is the number of spokes (or their

density per lineal length of rim).

> Please provide a couple of examples of "the bending strength of a bean

> going as the third power of its depth."

The equation is (b*h^3)/12 and is reviewed on various web sited:

http://www.engineersedge.com/calculators/section_square.htm

http://pergatory.mit.edu/2.007/Resources/calculations/bending/bending.html

> I would find it helpful if you used the MA-2 and the 40 mm deep aero

> rim you suggest in your earlier statement.

What earlier statement and what is it that is unclear?

Jobst Brandt

strength of deep aero rims, that can bridge large spoke-to-spoke distances for vertical loads, is not significantly higher than rectangular cross section rims, their width being the same" was the one that I was questioning.

I didn't say that it was unclear, I just don't agree with it.

To extend my point (possibly to ad nauseum), spoke holes on a 40 mm deep rim are closer together than your MA-2 for the same spoke count), spokes are shorter, spoke support angle is greater (yes I agree they are all by small amounts), but when combined with a rim that has 3 times the h (from the equation) I come to a different conclusion.

The lateral bending strength difference, at least to me, *is* significantlyl different.