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PostPosted: Sun Oct 16, 2011 11:37 pm 
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Thats very true that the inner edge on a wheel has to act as a leading and trailing edge. The other thing worth thinking about is that a the cross section we see on the internet is not the "horizontal" shape the wind sees because a wheel is a circle, and the leading edge becomes less "blunt" at a point half way up or down the wheel; much the same as most downtubes are 3:1 in dimension but closer to 4.5:1 when you consider the horizontal flow at it's angle in a bike.

Hope that made sense, essentially a long way of saying those shapes are less blunt in effect for a good portion of the wheels presented to the wind shape.

It's also why I recommended looking at the shape of the Speed Concept and Cervelo. (If you're thinking it would be hard to do this, the speed concept uses the same shape on it's seatpost, so easy to see what they used). NOTE: I'm not saying you should straight up jack any of the above companies shapes, just look for clues as to what works and maybe look for trends.


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PostPosted: Mon Oct 17, 2011 7:46 am 
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No, not those. Ones I am incorporating are REAL engineering. :lol:

Seriously, though, I am generally willing to give them more credit whenever I can, but HP stays and BMC clusters are just beyond me. On the other hand, many of the improvements indeed make good sense. If you look at a top end bike today compared to a 1980s steel bike, you can clearly see the difference.

NGMN/Jsinclair -- your comments are excellent points and I did consider these to some extent -- but will probably give them a bit more thought. The seattube is fairly "upright" at around 73-74 degrees, therefore the increase on the cross section is limited, but in the meantime, I am just not sure about a 3" wide seat mast/sail is consistent with the goal here. Those look a bit out of place and in my mind are reserved more for full-on TT bikes. In other words, I want the tube to be 80% "tubing" and 20% "fairing" and not the other way around.

In (further) other words, I am not mentally ready to do this just yet.

Image

In addition, I am not sure structurally Kamm tail and a strict "V" shape (eg, Dogma, etc.) make sense due to the dirty air and the manufacturing complexities (carbon layup will be trickier around abrupt edges, and the internal bladders will have a harder time pressing the fibers to the clamshells. In real life people end up putting clay-like material to fill any imperfections and that's not very cool, is it?). I did give Kamm a lot of thought, and lost a fair bit of sleep over it before ruling it out. At the relatively low speeds of 15-30mph at which this bike will most likely travel during its lifetime, I feel an oval shape which will be rounder in the front (hence a true "egg" shape) strikes a decent balance.

jooo wrote:
Like many of the aero features you're looking at incorporating?

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Posted: Mon Oct 17, 2011 7:46 am 


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PostPosted: Mon Oct 17, 2011 2:58 pm 
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ISP no, build a frame with a nice seatpost-seat tube transition like many of the current TT bikes, the Wilier Twin Foil is a good example. I would do an Kamm-Tail frame, something a bit more aggressive than the truncated airfoils of the Scott Foil has but retaining road frame geometry. It's something that Trek haven't used yet in their road frames and the resulting frame could very really intesting.

Also I have to note that Trek have filed a patent about the use of Kamm-Tail tube shapes in bicycle frame so it's a bit dangerous to take this way.

Do you use any program to design the carbon layups?

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PostPosted: Mon Oct 17, 2011 3:43 pm 
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Epic-o wrote:
Also I have to note that Trek have filed a patent about the use of Kamm-Tail tube shapes in bicycle frame so it's a bit dangerous to take this way.


That's interesting, Neilpryde also uses kamm tails in their frame designs, and are very vocal about it.

My vote is for kamm tails as well, didn't really read up on it, but assuming the concept is sound.

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PostPosted: Mon Oct 17, 2011 4:02 pm 
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Very interesting. I'll be checking in every day now to see if there's been more progress.

Elviento, given the expense to have a custom frame done in Asia (I'm working with someone who was quoted $50k to do a custom mold for a new bike line), I'm interested in anything you can share about having a custom done there (assuming that you did end up going there for production.

Is this a one-off frame strictly for yourself, or are your expectations bigger than a single unit?


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PostPosted: Mon Oct 17, 2011 4:46 pm 
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Well, I am tempted to not go too drastic on the tubing shape this time around... Maybe Kamm Tail will be for my next project??? I am still looking for more data on the effectiveness of Kamm in a lot of dirty air around the seattube. Another big issue with a TT type road bike is weight. Don't forget the S5 is DOUBLE the weight of a R5CA. That, and getting over the looks.

In addition, at 75kg, I find a solid bike really enjoyable to ride. So i really have to balance stiffness, weight, and aerodynamics in this project.



Epic-o wrote:
ISP no, build a frame with a nice seatpost-seat tube transition like many of the current TT bikes, the Wilier Twin Foil is a good example. I would do an Kamm-Tail frame, something a bit more aggressive than the truncated airfoils of the Scott Foil has but retaining road frame geometry. It's something that Trek haven't used yet in their road frames and the resulting frame could very really intesting.

Also I have to note that Trek have filed a patent about the use of Kamm-Tail tube shapes in bicycle frame so it's a bit dangerous to take this way.

Do you use any program to design the carbon layups?

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PostPosted: Mon Oct 17, 2011 4:59 pm 
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I am hoping this could turn commercial but at this point I will focus on something that makes "ME" happy. :beerchug:

Sent you a PM on the cost question.

CSquare43 wrote:
Very interesting. I'll be checking in every day now to see if there's been more progress.

Elviento, given the expense to have a custom frame done in Asia (I'm working with someone who was quoted $50k to do a custom mold for a new bike line), I'm interested in anything you can share about having a custom done there (assuming that you did end up going there for production.

Is this a one-off frame strictly for yourself, or are your expectations bigger than a single unit?

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PostPosted: Mon Oct 17, 2011 6:13 pm 
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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...

The BIGGEST DEAL in bike design is geometry and fit. This is also the most overlooked.. No fancy branding terms or catchy pitches on the issue. Especially in the smaller sizes. How many bikes get the trail right in size 48-52?? How many bikes handle the same in all sizes. How many bikes actually produce bikes with a proper reach for people <178cm?
Perhaps not so sexy but crucial for the user!

/a

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PostPosted: Mon Oct 17, 2011 6:23 pm 
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In case of doubt I'd go with a round ISP and just make it as small a diameter as I could.

The air is freaking dirty and going in pretty much all directions and to find out what works you'd need to spend serious time in the tunnel. If you should really make different sizes at some point you'd have to do it all over if they have different STAs.

So I'd go for the least amount of frontal area, least amount of skin drag and get comfort as I go.

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PostPosted: Mon Oct 17, 2011 6:37 pm 
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Andy, you are absolutely correct on fit and geometry. Love to hear your thoughts on what seems to be screwed up on small size bike fit and handling.

I was actually just about to start on that topic, so here it goes:

Virtual TT: 540 (since the seatpost will have smaller setback, so it really is more like 530 with more offset)
Virtual Seat tube: 526 c-t; 51.6 c-c
Seat tube actual: 470 c-c (amount of slope 30mm, midway between Colnago and Cannondale for your reference)
Headtube: 140mm (looks huge but the fork has a lower crown than any model on the market, 10mm lower than eg a Scott Addict), plus I deliberately planned a 6-7mm taller headtube, so overall effect on front end should be close to 125mm).
Seat angle: 74 deg (or 73 depending how you measure it, more details on this later)
Head angle: 72 deg (will be a bit on the slow side but am used to Colnagos, ... plus toe overlap won't be too bad)
Rake: 45mm
Drop: 70mm
Wheelbase: 778mm +/-2mm
Chain stay: 406
Seat height: 72cm +/-2mm

That's about it. Here is a picture of my Prince for reference...

Lastly, regarding tuning ride quality in the ISP, did you mean the type of fiber used, or just the shapes and diameters, or a combination of both? My feeling is probably both.


Attachments:
Prcsm.JPG
Prcsm.JPG [ 77.98 KiB | Viewed 2005 times ]

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PostPosted: Mon Oct 17, 2011 7:07 pm 
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You are right about the dirty air... that being said, I still want SOME oval-ness to my seat mast for the following reason:

The average human furmur is 48cm, and the midpoint of that is more likely to create the "dirty air" that affects the seat tube (The knee will be farther away from the seattube so I am discounting it for now).

Assuming 90rpm and a 36km/h speed, that means the midpoint in your thigh will have traveled 43 meters (0.24 x 2 x 90) per minute while the entire bike travels 667 meters. Therefore, your "bike speed" will be 14 times your "leg speed". In other words, your legs are not quite fast enough to make the air too dirty for the aero mast to have any benefit. So some aero-ness should be useful afterall.

Now that brings me to a really interesting part of the analysis -- assuming you don't want a super wide mast (side view) but still want some airfoil/oval shape, then how narrow laterally can you go? Did quite a bit of math but confused myself in the end... :noidea:

Intuitively, however, One would not want to go below 20mm, as the thinnest seatpost is around 25mm. In addition, as a lot of the load goes to the cluster area, you probably don't want a super thin cluster but can afford to make it narrower a bit higher up the mast...


Ypsylon wrote:
In case of doubt I'd go with a round ISP and just make it as small a diameter as I could.

The air is freaking dirty and going in pretty much all directions and to find out what works you'd need to spend serious time in the tunnel. If you should really make different sizes at some point you'd have to do it all over if they have different STAs.

So I'd go for the least amount of frontal area, least amount of skin drag and get comfort as I go.

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PostPosted: Mon Oct 17, 2011 7:25 pm 
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I don't agree with a 72degree headtube and a 45 rake fork at all.
This is not in the trail sweetspot and will not only produce slow steering at lower speed but it will also move into oversteer at higher speeds when you lean the bike over at higher speeds. It will also tend to wander when out off the saddle...
Plse PM me for details or check out some of the old US steel builders like Kirk. Those guys know their geo, they simply bent that fork to get it right. 90% of the majic w steel is you have infinite adjustability. With monocoque carbon it's the inverse. Sort of like analog versus digital :lol: !

Re seatpost: A thin deep post will flex the wrong way. Not worth it on an all purpose bike. The aero savings are in the front end. An aero fork, heatube or best of all fit that allows you to spend time in the drops!!

http://www.kirkframeworks.com/Fitting.htm
http://davesbikeblog.blogspot.com/2007/ ... it-of.html

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Last edited by andy2 on Mon Oct 17, 2011 9:41 pm, edited 2 times in total.

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PostPosted: Mon Oct 17, 2011 9:23 pm 
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Kamm tail is not the way to go with an unrestricted full custom bike... With an egg shape, there will be earlier separation than a full airfoil. I'd just use a 12% or 15% NACA and be done with it


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PostPosted: Tue Oct 18, 2011 6:14 am 
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Thanks for the links, Andy. Looks like Kirk favors 63mm trail and Dave 59-60mm. Mine (w 21mm tires) comes out to 62mm trail, which does not seem that far off. I do agree it's slightly on the longer side, because my Prince and C50 both have fairly shallow head angles, so this is already creating quicker handling than before. A 46/47 fork rake probably work best but let's see how this turns out for now...

andy2 wrote:
I don't agree with a 72degree headtube and a 45 rake fork at all.
This is not in the trail sweetspot and will not only produce slow steering at lower speed but it will also move into oversteer at higher speeds when you lean the bike over at higher speeds. It will also tend to wander when out off the saddle...
Plse PM me for details or check out some of the old US steel builders like Kirk. Those guys know their geo, they simply bent that fork to get it right. 90% of the majic w steel is you have infinite adjustability. With monocoque carbon it's the inverse. Sort of like analog versus digital :lol: !

Re seatpost: A thin deep post will flex the wrong way. Not worth it on an all purpose bike. The aero savings are in the front end. An aero fork, heatube or best of all fit that allows you to spend time in the drops!!

http://www.kirkframeworks.com/Fitting.htm
http://davesbikeblog.blogspot.com/2007/ ... it-of.html

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PostPosted: Tue Oct 18, 2011 6:22 am 
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By the way, can I place a vote for moving the name to Falcon from Falco?

Clearly you are referencing this:
http://www.youtube.com/v/j3mTPEuFcWk?fs=1&amp;hl=zh_CN
Image

and not this:
Image

Although Falco was a pretty cool dude. First white rapper ever. In the 80's no less. In German AND English.

Just sayin'. Or do you like Falco too?

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Posted: Tue Oct 18, 2011 6:22 am 


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