HOT: Active* forum members generally gain 5% discount at starbike.com store!
Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Articles FAQ Contact About




Post new topic Reply to topic  [ 233 posts ] 
Go to page Previous  1, 2, 3, 4, 5, 6 ... 16  Next
Author Message
PostPosted: Tue Oct 18, 2011 6:34 am 
Offline
User avatar

Joined: Thu Aug 25, 2005 7:09 pm
Posts: 1227
Location: In the industry
This is probably the second most important junction on a bike frame (second only to the BB), so it deserves a separate post.

First I want to illustrate my point by showing a Scott Addict's headtube.

Image

As you can see, the downtube's junction on the headtube is fairly high, and the fork has a crown as tall as Yao Ming.

This creates 2 issues:

1. The front end stiffness suffers, because the two headset bearings will be closer for a given frame size, and that doesn't give you great torsional stiffness.

2. The aerodynamics suffers as there is a lot of area between the downtube and the crown junction.

My approach (and this is nothing new, Cervelo is already doing it) is to spread the bearings as far apart as possible, including depressing the fork crown. My fork length will be 355mm-ish... although I'd have to find out if manufacturing will run into any issues...

Re point 2, Pinarello/Merckx are doing something interesting to smooth out the airflow around that area.

Image

This is a good move as we have seen wind tunnel data that indicate the high air turmoil around this junction. But their "fairing" after the fork appears to be pure dead weight and does not add to the structural soundness of the area.
So a "lower the downtube" with a modified shape will fix that. The enlarged section will also contribute to the front end stiffness. In addition, this will effectively place the lower bearing near the middle of the downtube junction rather than below it, which should have some stiffness benefit (however little).

Lastly, a lower downtube junction gives you a slightly shorter downtube as well (probably 3mm). No biggie but this is WW, so there you go...


Attachments:
1246916747917-802fbm3rcbmb-670-75.jpg
1246916747917-802fbm3rcbmb-670-75.jpg [ 58.45 KiB | Viewed 1593 times ]

_________________
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal


Last edited by elviento on Tue Oct 18, 2011 7:17 am, edited 1 time in total.
Top
 Profile  
 
Posted: Tue Oct 18, 2011 6:34 am 


Top
  
 
PostPosted: Tue Oct 18, 2011 6:51 am 
Offline
User avatar

Joined: Thu Aug 25, 2005 7:09 pm
Posts: 1227
Location: In the industry
:noidea: I better catch up on 80s rap music.

I was more thinking of this dude...

Image
Image

Anyway, both are fairly cool IMHO, but there is a Falcon brand in the UK who sell entry level bikes, so I want it to be a bit different. Plus one less letter in the decals is more ww... :lol:

prendrefeu wrote:
By the way, can I place a vote for moving the name to Falcon from Falco?
Just sayin'. Or do you like Falco too?

_________________
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal


Top
 Profile  
 
PostPosted: Tue Oct 18, 2011 7:14 am 
Offline
in the industry
User avatar

Joined: Sun Dec 16, 2007 9:33 pm
Posts: 713
Location: Luxembourg / Sweden
I agree in principle with your thinking on this junction.
We have seen clear effects on this in our structural tests.
But when it comes to aero it's not. The air behind the front brake is already disturbed, you will not mend what is already broken by doing this. Also if you run standard der cabling these will interfere with the airflow.

On the trail: Personally I don't like how a bike with a trail >60 handles. I favor high speed stability when descending. Especially if you use high profile aero rims! Others tolerate highish rakes, especially light guys (not me). So I'm told... Also your weight distribution matters..

_________________
Technical Artisans


Top
 Profile  
 
PostPosted: Tue Oct 18, 2011 7:48 am 
Offline
User avatar

Joined: Thu Aug 25, 2005 7:09 pm
Posts: 1227
Location: In the industry
Re aero effect, it should be more relevant if one can optimize the cabling, which I am attempting to do. Here is Pinarello's CFD simulation...

Image

Re trail/rake, etc., agreed that one should not underestimate the impact of deep aero wheels on handling. That said, would it make sense to have a high rake fork for aero wheels and a low rake fork to go with low prof wheels? Talk about a slow wheel change... :noidea: ).

andy2 wrote:
I agree in principle with your thinking on this junction.
We have seen clear effects on this in our structural tests.
But when it comes to aero it's not. The air behind the front brake is already disturbed, you will not mend what is already broken by doing this. Also if you run standard der cabling these will interfere with the airflow.

On the trail: Personally I don't like how a bike with a trail >60 handles. I favor high speed stability when descending. Especially if you use high profile aero rims! Others tolerate highish rakes, especially light guys (not me). So I'm told... Also your weight distribution matters..

_________________
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal


Top
 Profile  
 
PostPosted: Tue Oct 18, 2011 8:51 am 
Offline

Joined: Tue Sep 22, 2009 1:29 pm
Posts: 631
Location: UK
Not sure if you're developing your own fork too, but the obvious solution to some of the issues in this area is to use something like the THM Scapula approach and integrate the brake, or a tri fork with rear mounted brakes (although not too sure how these desgins would ride on an all round bike, and the maintenance is a PITA)

Love this post by the way, looking forward to seeing the end product!

_________________
"We live in an age when unnecessary things are our only necessities." Oscar Wilde

Pegoretti Responsorium
Parlee Z5i
Donhou Commuter
1946 MacLeans Featherweight (L'Eroica!)
1991 Cannondale SM1000 (currently being renovated)


Top
 Profile  
 
PostPosted: Tue Oct 18, 2011 1:52 pm 
Offline

Joined: Tue Jan 15, 2008 6:29 pm
Posts: 30
andy2 wrote:
ISP
Pro: This is where you tune the ride quality. NOT in the chainstsays as the marketing people are telling you.
(yes I have the data & sources to go with the statement)
Con: What everyone is saying:-)! We chose against...


So true (that the ISP can define the ride quality). When Look launched the 595 with the ISP, that's exactly what we said about it....there's too many variations in seatposts, so when a company designs a frame around a certain seatpost and then a user changes to a lighter/flexier/etc post, then the ride qualities have now been changed for that bike.

With an ISP, the frame manufacturer controls the ride quality with no variance. Now the bike rides exactly as they intended it to.

Too many people see the ISP as a gimmick/marketing spin, but the benefits are real.....


Top
 Profile  
 
PostPosted: Tue Oct 18, 2011 4:53 pm 
Offline
User avatar

Joined: Sun Jun 18, 2006 10:29 am
Posts: 3448
Location: Athens, Greece
CSquare43 wrote:
Too many people see the ISP as a gimmick/marketing spin, but the benefits are real.....

+100
Most people I know who have had the experience of an ISP frame (including myself) love it.

_________________
My Cipollini Bond
My 8618gr Colnago Master X-light
My 9745gr Pinarello Dyna


Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 1:02 am 
Offline
User avatar

Joined: Thu Nov 10, 2005 5:31 pm
Posts: 3454
Location: Surrey B.C. Canada
I love my ISP and I also love the way that ROB set up the stubbie inside the tube instead of using a topper which I think just look ugly. Not sure how easy this would be to do with a Carbon frame but it is the cleanest set up I have ever seen.

There are a lot of other things you could build into a nice aero road bike. If I had enough money to build another custom bike, there are a few things I would do differently for sure adn they would be all aero related.

Image

_________________
BIG DADDY B FLOW
AERO & LIGHT is RIGHT

Cervelo SLC 5890g/12.98 lbs


Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 1:15 am 
Offline
User avatar

Joined: Thu Nov 10, 2005 5:31 pm
Posts: 3454
Location: Surrey B.C. Canada
I would also consider looking at a brake like the Tektro T726R on the front with a cable hanger which would allow you to run a cable down the front of the head tube which is more aero than a housing and cable running down the side of the head tube with a conventional brake. If you are designing the bike you could use this brake front and rear and keep the cables completely inline with the frame and out of the wind.


Image

_________________
BIG DADDY B FLOW
AERO & LIGHT is RIGHT

Cervelo SLC 5890g/12.98 lbs


Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 5:19 am 
Offline
User avatar

Joined: Thu Aug 25, 2005 7:09 pm
Posts: 1227
Location: In the industry
Is that glued or welded? Or does it offer any adjustment? BTW, the rear brake cable solution is really similar to what I have in mind. I like the way it's in the middle rather on the side (eg, the C'dale EVO). Aerodynamically slightly better and for smaller sizes gives you a bit more leg room for the braking action.

BmanX wrote:
I love my ISP and I also love the way that ROB set up the stubbie inside the tube instead of using a topper which I think just look ugly. Not sure how easy this would be to do with a Carbon frame but it is the cleanest set up I have ever seen.

There are a lot of other things you could build into a nice aero road bike. If I had enough money to build another custom bike, there are a few things I would do differently for sure adn they would be all aero related.

_________________
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal


Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 5:47 am 
Offline

Joined: Mon Mar 01, 2010 8:07 pm
Posts: 635
BmanX wrote:
I would also consider looking at a brake like the Tektro T726R on the front with a cable hanger which would allow you to run a cable down the front of the head tube which is more aero than a housing and cable running down the side of the head tube with a conventional brake. If you are designing the bike you could use this brake front and rear and keep the cables completely inline with the frame and out of the wind.


Image


I have been hearing above argument on some other places too but not sure what is more aero. Judging the design of the Tektro brake for me a side pull DA 7900 brake design appears to be more aero. By the way I like the 7900 brake design best from all others out there.
Not sure if a center pull brake cable and housing is not disturbing the clean airflow in front of the head tube that much that the drag of a side pull housing should be acceptable. Unless it is all hidden like the brake of the Scapula fork but with center pull and with some brake housing going down inside the fork and headtube entering from the headset cap.WW issues?

@elviento - I wish you good luck with your project.

_________________
Kuota Kom Evo
viewtopic.php?f=10&t=111825&p=955235#p955235" onclick="window.open(this.href);return false;


Last edited by bura on Wed Oct 19, 2011 6:23 am, edited 1 time in total.

Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 5:55 am 
Offline
in the industry
User avatar

Joined: Sun Dec 16, 2007 9:33 pm
Posts: 713
Location: Luxembourg / Sweden
I was just about to write that :shock: :D
It might be worth it to take a look at EE brakes too, they are very nice and compact and would go well behind the fork.

_________________
Technical Artisans


Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 6:22 am 
Offline
User avatar

Joined: Thu Nov 10, 2005 5:31 pm
Posts: 3454
Location: Surrey B.C. Canada
I have EE brakes and once the aero brakes arrive I will be able to compare them better. These are tests done on Slowtwitch that show that the center pull brake set up (modified version of this and not as neat) is as good as a pair of the Simkins aero brakes. There is now housing at all when you are using these aero center pull brakes as only the cable is exposed. A cable is just way better than housing and cable.

There brakes are not light at 149g each but I am sure I can lighten them up a fair bit when I get them.

My tri bike will not be the most aero but the goal is it get it under 6.8

_________________
BIG DADDY B FLOW
AERO & LIGHT is RIGHT

Cervelo SLC 5890g/12.98 lbs


Top
 Profile  
 
PostPosted: Wed Oct 19, 2011 6:35 am 
Offline
User avatar

Joined: Thu Nov 10, 2005 5:31 pm
Posts: 3454
Location: Surrey B.C. Canada
from slowtwitch classifieds but it gives you an idea of the size and how clean this can look.

Image

_________________
BIG DADDY B FLOW
AERO & LIGHT is RIGHT

Cervelo SLC 5890g/12.98 lbs


Top
 Profile  
 
Posted: Wed Oct 19, 2011 6:35 am 


Top
  
 
PostPosted: Wed Oct 19, 2011 6:45 am 
Offline
in the industry
User avatar

Joined: Sun Dec 16, 2007 9:33 pm
Posts: 713
Location: Luxembourg / Sweden
Never mind the cable, but between that cable hanger and those brakes most aero benefit of anything north of the rim is lost. The straddle cable mounting fi is just plain horrible. Sort of like having a bicycle mounted on the front of your aero car..... :?: :noidea:

_________________
Technical Artisans


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 233 posts ] 
Go to page Previous  1, 2, 3, 4, 5, 6 ... 16  Next


Who is online

Users browsing this forum: Google [Bot], thegunner and 40 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

   Similar Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Assos S5 vs S7 bibs. Looking for feel and fit comparison

in Road

dgasmd

8

1256

Mon May 12, 2014 11:51 am

kode54 View the latest post

There are no new unread posts for this topic. Rotor Aero Q-rings, is there a new 2014 design?

in Road

ill principe

9

1458

Thu Apr 17, 2014 8:34 am

dominikk View the latest post

There are no new unread posts for this topic. Chainring design and interaction with latest 11 speed

in Road

Omiar

5

686

Sun Aug 17, 2014 2:06 am

Zoro View the latest post

There are no new unread posts for this topic. Light bike or stiff bike?

[ Go to page: 1, 2, 3 ]

in Road

Kermithimself

32

2688

Mon Sep 22, 2014 7:19 pm

06SpiceRed View the latest post

There are no new unread posts for this topic. My next bike. SL3 or SL4?

in Road

Iamspecialized

13

933

Sat May 17, 2014 6:34 am

mpulsiv View the latest post


It is currently Fri Oct 31, 2014 5:31 pm

All times are UTC + 1 hour




Advertising   –  FAQ   –  Contact   –  Convert   –  About

© Weight Weenies 2000-2013
hosted by starbike.com


How to get rid of these ads? Just register!


Powered by phpBB