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You guys know I love me some aero goodness.....
Last Post 10/04/2016 05:05 PM by Frederick Jones. 25 Replies.
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Cosmic Kid

Posts:2183

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09/29/2016 10:05 AM
....but I think these new bikes form Diamond Back and Cervelo may be my breaking point.



Just say "NO!" to WCP!!!!
SideBySide

Posts:428

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09/29/2016 02:29 PM
Ick!
huckleberry

Posts:501

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09/29/2016 02:45 PM
"....but I think these new bikes form Diamond Back and Cervelo may be my breaking point." - CK


"A man must know his limits."
longslowdistance

Posts:1498

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09/29/2016 03:09 PM
Looks like a superbike motorcycle, disc brakes included.

Cosmic Kid

Posts:2183

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09/29/2016 03:26 PM
Spot on, LSD...a lot of people have been calling it a DucatiBack.
Just say "NO!" to WCP!!!!
79pmooney

Posts:1756

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09/29/2016 04:01 PM
It does a 25 mile TT in about 9 minutes, no?
Gonzo Cyclist

Posts:568

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09/29/2016 04:56 PM
totally LSD, that was my 1st thought!! That looks like one of my motorcycles from my crotch rocket days!! DucatiBack, that is funny!
Lots of space to hide a motor down there!! LOL!!
79pmooney

Posts:1756

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09/29/2016 08:22 PM
Motor? No, this baby's got an engine. Room for the gas tank and enough sound insulation that you would never hear it. Exhaust runs through the catalytic converter above the crankset and out behind the seatpost. (The catalytic converter is a good one. No visible smoke.)

Ben
huckleberry

Posts:501

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09/29/2016 09:02 PM
I'll take the Ducati...
longslowdistance

Posts:1498

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09/30/2016 10:10 AM
LOL!
6ix

Posts:213

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09/30/2016 10:45 AM
I want to know more about that Cervelo. Those disc brakes sure look super aero on there!!

If the DiamondBack could be toned down just a bit and get rid of all the triathlon-specific add-ons like storage compartments and 5-course meal service on the handlebars, it could be a very interesting TT bike.

With elements of the Lugano charter rules being removed, will we finally see designs like in the good ol' days of Hotta, Lotus and Zipp? I won't include Pinarello in here because only Indurain's Espada was actually cool. The stuff Riis and Ullrich used were horrendous. Guess it comes down to if they are going to allow designs that don't meet the double-triangle rule.

Nick A

Posts:525

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09/30/2016 11:41 AM
I've never ridden a TT bike. Did my racing before they existed, and never been a tri guy. Now, that being said, when I switched from old school rims to my current not all that deep profile Mavic Kysiriums with bladed spokes, I noticed the first time there was a cross gust, it took me by surprise how the wheels caught the wind. When does such a large side profile become a problem for stability? Also, I wonder do they wind tunnel test these with a wind direction that is not head on? I wonder how that effects the slippery-ness of the profile. You'd think with the money involved, they would. But who knows?

Nick
6ix

Posts:213

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09/30/2016 12:02 PM
Nick, that's a good question about the wheel profiles. I could definitely be wrong but my guess is that it's similar to rotational weight where mass at the outside of the wheel (i.e., rim) is far more significant than if it was centered at the hub. Since your front wheel can be turned, I'd think that it will react more than equally increasing the surface area of the frame. That's why deep-section rims are so difficult to use during a cross-wind. Your own body has more surface area than any of these bikes. When riding with shallow rims with a strong cross-wind, you just kinda lean into the wind but your steering doesn't get too twitchy but a tall rim will be a nightmare to deal with.

So, if you successfully read all of that, I'd just say that the larger tubes and surface area of the frames doesn't adversely affect control. Or at least not even close to how much a deep-section front wheel would in a crosswind.
Cosmic Kid

Posts:2183

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09/30/2016 12:34 PM
Nick...I can ride my Zipp 404 (60mm depth) on my Shiv TT all day with no issues. When I throw my 808 on, it can definitely impact the handling on gusty / windy days. Did a recon ride on the Madison course on one windy day and it was definitely sketchy in a few places.

yes, they test bikes at yaw and large profile bikes usually improve at yaw due to the "sail effect". That is why you should ALWAYS use a disc, even in windy conditions. Now, whether bikes with large profiles like this can be impacted negatively in terms of handling in crosswinds....that is something I am waiting to see. Given the large profile presented from the front wheel the the downtube on the DB, it is something that would concern me. However, only the wheel is connected to the steering axis, so the large DT profile may not impact handling.
Just say "NO!" to WCP!!!!
79pmooney

Posts:1756

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09/30/2016 04:04 PM
6ix, the reason our (relatively) huge bodies don't become a huge issue in crosswinds is because we are not remotely lifting surfaces, ie airfoil shaped to sculpt and shape the wind. We are (sadly) just drag. (Not entirely true, but way too close for this aero and hydrodynamically thinking mind. It is impressive how much lift we can obtain just freestyle swimming by orienting our hands and forearms when we plunge them into the water and pull back for our stroke. The straight pull back is not the fastest.)

A symmetrical wing section can develop a lift coefficient of around 1.6. Really bad shapes (think parachutes) have a drag coef. of around 1.0. Plus the drag is always in the direction of the wind. Lift is at right angles to that wind. So an effective (or as sailors like to say, "apparent") wind angle of 20 degrees, if the drag force on a 1 sq foot object is 10 pounds. the lift on the same sized object but an aerodynamic lifting surface could be 16 pounds. Now factor in the direction of the forces. Drag, as relevant to the bike as a crosswind will be the sine of the angle, ie 10 X sin (20) = 3.4 pounds. Lift will be times the cosine, ie 16 X cos (20) = 15.0 pounds or 4.4 times higher. (It will also give you 5.5 pound thrust forward. To further make this interesting, lift is VERY subject to th relative wind angle. Small changes in angle, say from 20 degrees to 10 degrees will make a 2X difference, over 7 pounds in this example. Between that and the square factor in wind speed effect, you can see how topography, trees, buildings, other vehicles, etc, can make for a wlid ride on windy days for aero bikes.)

Personally, I think that airfoil shapes that can develop lift in a forward direction should be banned from bicycle racing. There is a place for land yachts. This isn't it.

Ben - lifelong sailor who loves planing dinghies and has sailed catamarans, winsurfers - very badly -, International Canoes, ice boats and skate sails. (hitting ! 60 mph and 45 on those last two).
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