Bike porn

Ok;

Assume four point bend deflection (but works for all small scale deflection cases), non-dynamic loading case. Where major span is 100mm, and minor span is 50mm. Again, as this is constant this does not need to be exactly the same as real BB's.

Assume square axle of width (a) 17.68 mm, (b) 21.2mm. Where (a) is the maximum width for a square axle on a standard 25mm BB, and the same for (b) where 21.2mm is the maximum for the BB30 standard.

Then assume an exposed axle length of 25mm (not that this is used in the calculation, but needs to be non-zero to allow for over roller rotation). Apply symmetric loading on the central loading rollers.

As in;

.......↓......... ↓.........

---

..↑...................... ↑..

Then calculate area moment of inertia, I. Where;
I=bh^3/12 where b=width, h; height

From above we say that b=h, thus I=h^4/3

Thus for,
BB25 I=(0.01768)^4/12=8.14e-9m^4
BB30 I=(0.02122)^4/12=1.68e-8m^4

Let stiffness be, say.... 163GPa, (medium stiffness UD CFRP - In this case thats Hex IM7/8552)

Then using;

E[flex]=F(L^3)/4Id;

where d; deflection. Re-arrange for d

d=F(l^3)/E4I

Letting F (quasi again!) =1kN

Thus;

d|(a)=(1000)(0.1^3)/(163,000,000,000)(4)(8.14e-9)
d|(b)=(1000)(0.1^3)/(163,000,000,000)(4)(1.68e-8)

Thus;
Deflection for
(a)[25mmBB]=1/5308=1.88e-4m, or 0.188mm
(b)[BB30}=1/11016=9.08e--5m, or 0.0908mm

Yeah but if you assume that:

s(t) = s0 +
|v(t)|dt ; r(t) = r0 +
v(t)dt ; v(t) = v0 + a(t)dt
v(t) = v0 + at en s(t) = s0 + v0t + 1
2 at2.
ρ = v|v|= dre˙t = ven ; en =e˙t| e˙t|
v = vQ +v  + ω ×r  en a = aQ +a
α ×r  + 2ω ×v  + ω × (ω × r )ω × (ω ×r ) = −ω2r n
P = ˙W = F · v
W = T + U ; ˙T = −˙U met T = 1
2mv2.
S = Δp =Fdt
A =2F · ds =21
F cos(α)ds
L: τ = ˙L = r × F; and L= r × p = mv × r, |L | = mr2ω
τ = ∂U ∂θ Fi = 0 en
τi = 0.

So basically saying stuff that nobody understands doesn't make you right.

ω ω ω ω ω ω ω ω

do you realize you have posted 8 tiny asses?..

That twisted bike would ride like a noodle.

ba dom tish.

It's necessary to demonstrate with mathematics why a carbon square taper spindle isn't porn.

No it isn't, porn is aesthetic for most people rather than technical. Mathematical justification for technical porn is for nerds and nerds don't do porn (it would scare them)

Ah, but if it wasn't for nerds, we would have no Internet, therefore, no redtube ect.....

But yeah, fuck maths, more porn.......

So basically saying stuff that nobody understands doesn't make you right.

It's not my fault you dont follow it. Its pretty simple to be honest.

Anyway, its maths porn. And who said aesthetics had nothing to do with maths.

You guys can take this technical discussion elsewhere, this is the pron thread.

Yeah but if you assume that:

s(t) = s0 +
|v(t)|dt ; r(t) = r0 +
v(t)dt ; v(t) = v0 + a(t)dt
v(t) = v0 + at en s(t) = s0 + v0t + 1
2 at2.
ρ = v|v|= dre˙t = ven ; en =e˙t| e˙t|
v = vQ +v  + ω ×r  en a = aQ +a
α ×r  + 2ω ×v  + ω × (ω × r )ω × (ω ×r ) = −ω2r n
P = ˙W = F · v
W = T + U ; ˙T = −˙U met T = 1
2mv2.
S = Δp =Fdt
A =2F · ds =21
F cos(α)ds
L: τ = ˙L = r × F; and L= r × p = mv × r, |L | = mr2ω
τ = ∂U ∂θ Fi = 0 en
τi = 0.

So basically saying stuff that nobody understands doesn't make you right.

could you 2 please shut your faces, thank you

for once we have a couple of people talking some seriuos for a change, no jokes, no bullshit, something the you can B) read and learn something or B)just ignore.
it is so difficlut to scroll down 3 post, FFS?

I think me and Rik could be friends....

Needs larger downtube

surely you mean bigger downtube

ω ω ω ω ω ω ω ω
*i was thinking more, 8 pairs of norks ! *

Ok;

Assume four point bend deflection (but works for all small scale deflection cases), non-dynamic loading case. Where major span is 100mm, and minor span is 50mm. Again, as this is constant this does not need to be exactly the same as real BB's.

Assume square axle of width (a) 17.68 mm, (b) 21.2mm. Where (a) is the maximum width for a square axle on a standard 25mm BB, and the same for (b) where 21.2mm is the maximum for the BB30 standard.

Then assume an exposed axle length of 25mm (not that this is used in the calculation, but needs to be non-zero to allow for over roller rotation). Apply symmetric loading on the central loading rollers.

As in;

     .......↓.........          ↓.........

---

---

..↑...................... ↑..

Then calculate area moment of inertia, I. Where;
I=bh^3/12 where b=width, h; height

From above we say that b=h, thus I=h^4/3

Thus for,
BB25 I=(0.01768)^4/12=8.14e-9m^4
BB30 I=(0.02122)^4/12=1.68e-8m^4

Let stiffness be, say.... 163GPa, (medium stiffness UD CFRP - In this case thats Hex IM7/8552)

Then using;

E[flex]=F(L^3)/4Id;

where d; deflection. Re-arrange for d

d=F(l^3)/E4I

Letting F (quasi again!) =1kN

Thus;

d|(a)=(1000)(0.1^3)/(163,000,000,000)(4)(8.14e-9)
d|(b)=(1000)(0.1^3)/(163,000,000,000)(4)(1.68e-8)

Thus;
Deflection for
(a)[25mmBB]=1/5308=1.88e-4m, or 0.188mm
(b)[BB30}=1/11016=9.08e--5m, or 0.0908mm

Which is pretty much exactly 2. So for the same load, the deflection is half. Not a third.

I think that will do. And there was me thinking that I finished work at 5pm :-)

This just might be one of th greatest posts in LFGSS history

Too many variables. cough

and what might they be?

for flexural stiffness where modified beam theory limitations apply (ie, small delfections relative to aspect ratio of member) there are no other variables which need to be taken into account

sorry, i failed to figure out - who won? you or MT?

*SEXON SPECIAL FRAME by CHERUBIM*

Gorgeous. I hate all these carbon fibre space 2001 style bikes, they just look shit in my eyes. Sure, they are great at what they do, but there is no class to them, there is no inspiration. I remember a great saying, things you own in life should be beautiful or useful.

and what might they be?

for flexural stiffness where modified beam theory limitations apply (ie, small delfections relative to aspect ratio of member) there are no other variables which need to be taken into account

Apologies, I have no idea if it a water tight calculation.

Looks impressive. :O

haha, nobody wins...

We were looking at different stiffnesses.

Flexural stiffness, when you put your weight on one pedal, to see how much the axle would bend downwards.

Torsional stiffness, when you put your weight on one pedal, to see how much the axle rotates clockwise.

With carbon fibre being what it is, it has very different stiffnesses in different directions. So for something like an axle (which experiences multiple loading directions), it does not make too much sense to have it out of something like carbon. Something like Ti is much better as it has good flexural stiffness and torsional stiffness. Its also much less brittle than carbon.

on sale that was on this forum..

Hope they got a refund.

It's not my fault you dont follow it. Its pretty simple to be honest.

Anyway, its maths porn. And who said aesthetics had nothing to do with maths.

I really don't know why you would want to be on a forum with such inferior beings then. The kabballah forum is that way please >>>>>>>>>>>>>>

do you realize you have posted 8 tiny asses?..

I was hoping that would go by unnoticed.... :o

Bad photo, but I fell in love with this bike while looking around the Edge stand at Interbike.

Yeah, nice

That is truly hideous.