Angled brake track or straight brake track for maximum aero

Discuss light weight issues concerning road bikes & parts.
Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Hambini, thanks for the explanation and good to see you back - always interesting info from you.

But *please* try not to call people "morons" etc. on here, it annoys me and many others, it's unnecessary and it will shorten your stay :D

Best,
Marin

by Weenie


hambini
Posts: 354
Joined: Tue Nov 15, 2016 8:13 am

by hambini

Marin wrote:
Wed Nov 07, 2018 11:00 pm
Hambini, thanks for the explanation and good to see you back - always interesting info from you.

But *please* try not to call people "morons" etc. on here, it annoys me and many others, it's unnecessary and it will shorten your stay :D

Best,
Marin
If it annoys you, then please put me on block. All of the reasoning will be coming out in the next few days.

AJS914
Posts: 2366
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Hambini, what does the drawing illustrate about angled brake tracks?

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mpulsiv
Posts: 1235
Joined: Mon Mar 24, 2014 9:17 pm

by mpulsiv

hambini wrote:
Wed Nov 07, 2018 10:38 pm
I have drawn a really crap sketch on my marker board to illustrate what I think most people think airflow looks like and how it actually looks.
aerosketch.jpg
If you assume the conentious issue of yaw angle is the constant and zero, the top drawing shows how marketing perople show the aerofoils off. Nice steady flow going over the aerofoil section.

In reality the airflow is much more like the bottom sketch. The yaw angle is still zero but you get vortices and a solid body (the aerofoil) slicing through the turbulence, the air does not hit the aerofoil square on despite a zero yaw angle. This is the difference between effective and actual yaw angle.

For a wheel test to be valid and use steady state analysis like the top picture then you would need to increase the yaw angle to more than you think to give an accurate reading. My critics who are mainly on slowtwitch can argue over whether the systems I use for developing wind tunnel simulations to model the real world are accurate or not but they cannot argue the airflow hitting the wheel and tyre looks like the bottom picture (unless they are in still air in the middle of nowhere on a perfectly smooth surface with all bodies around at uniform temperature). When the airspeed gets faster (rider goes faster), the vortices and turblence is straightened by a stagnation point in front of the rider so the yaw angle gets smaller.

In general providing the sweep of the aerofoil is not too abrupt and the brake track is not designed poorly, a wheel with a DEEPER rim will always be faster. A deeper rim reduces the area of the wheel that has no solid boundary in it and reduces the drag from spokes. Hence a deeper rim will be faster.

The caveat is provided a moron hasn't designed it.

Hambini
Fair enough. Help me understand this layman terms. What is the consensus on narrower brake track? Based on my understanding, turbulence is increased at a lower speed.
Is there a valid reason to design a rim with an angled brake track? If so, I'd like to hear valid statements.
Racing is a three-dimensional high-speed chess game, involving hundreds of pieces on the board.

:arrow: CBA = Chronic Bike Addiction
:arrow: OCD = Obsessive Cycling Disorder

hambini
Posts: 354
Joined: Tue Nov 15, 2016 8:13 am

by hambini

AJS914 wrote:
Wed Nov 07, 2018 11:34 pm
Hambini, what does the drawing illustrate about angled brake tracks?
In a wind tunnel with perfect flow, it may improve drag -depends on the rest of it.

Out on the road. Unlikely that the brake track by itself will make much difference.

It needs to be considered more of a system than an individual feature

Marin
Posts: 3062
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

hambini wrote:
Wed Nov 07, 2018 11:26 pm
Marin wrote:
Wed Nov 07, 2018 11:00 pm
Hambini, thanks for the explanation and good to see you back - always interesting info from you.

But *please* try not to call people "morons" etc. on here, it annoys me and many others, it's unnecessary and it will shorten your stay :D

Best,
Marin
If it annoys you, then please put me on block. All of the reasoning will be coming out in the next few days.
I don't want to put you on block, I really enjoy the engineering side!

Unfortunately, I didn't get my point across:

Even if "all the reasoning comes out" you shouldn't call people names.

It's *much* more effective if you just present the facts, and then let people make up their minds. If your readers then think "ok, they really are total morons" you won without being an ass :mrgreen:

youngs_modulus
Posts: 529
Joined: Wed Sep 20, 2006 1:03 am
Location: Portland, OR USA

by youngs_modulus

Marin wrote:
Thu Nov 08, 2018 8:31 am
I don't want to put you on block, I really enjoy the engineering side!

Unfortunately, I didn't get my point across:

Even if "all the reasoning comes out" you shouldn't call people names.

It's *much* more effective if you just present the facts, and then let people make up their minds. If your readers then think "ok, they really are total morons" you won without being an ass :mrgreen:
I second this. I'm a bit of a hypocrite because I don't suffer fools gladly, but frankly: I'd be more persuasive if I did. Also, who can argue with a call to civility?

Hambini, please consider that Marin has been really solicitous, even after your snarky retort. He has a point. I've only recently re-engaged with WW, but I think you might have a lot to contribute. Please don't ruin it with venom.

hambini
Posts: 354
Joined: Tue Nov 15, 2016 8:13 am

by hambini

I think it's a fair point, so I must apologize to marin. Please consider this as that.

Marin
Posts: 3062
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

hambini wrote:
Thu Nov 08, 2018 10:43 am
I think it's a fair point, so I must apologize to marin. Please consider this as that.


:welcome:

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