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

Posts:2146

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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:427

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

Posts:490

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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:1474

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

Cosmic Kid

Posts:2146

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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:1735

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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:1735

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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:490

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

Posts:1474

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

Posts:203

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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:523

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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:203

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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:2146

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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:1735

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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).
79pmooney

Posts:1735

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09/30/2016 04:14 PM
CK, I've been wondering about the styling of that Diamondback. Finally got it. It was a challenge. Protoype got cut clean by a garage door. But the photos had to be out next week. No time. So the bike was cut to a clean line at the break. Seatpost and HBs photoshopped in. Now that the photo is out, production has to make them. Funny how great innovations come to be if you know the inside story!

Ben
Cosmic Kid

Posts:2146

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10/01/2016 08:41 AM
Updated pic of the new Cervelo....

Just say "NO!" to WCP!!!!
Nick A

Posts:523

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10/03/2016 10:18 AM
Wow, interesting analysis. What blows my mind are aero bars. What I mean by that is that for decades nobody figured this out. There's no technology involved, just the shape of some handlebars. I even, will occasionally put my forearms on the tops of my road bars, and can instantly feel the difference. I'm surprised nobody stumbled upon this pre-LeMond.

Aerodynamics is a fascinating field, but sooo complex. I've had a couple careers, and one was designing bridges as a civil engineer. Except, they were just your boring highway overpass variety. Simple static wind load. No aerodynamics required. But I do know from being peripherally involved with one suspension bridge, that the aero can get interesting. At one time they widened the bridge, and used an open steel grate deck, not for weight but for aero. It purposely killed the lift caused by the new profile. There was a cable stayed bridge somewhere that worked well in the wind tunnel, but then in practice they found that when water droplets formed on the cables, they began to "sing" during a steady breeze. As I recall, it was more of an embarrassment, than a safety issue.

Nick
79pmooney

Posts:1735

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10/03/2016 12:53 PM
Nick, a little off topic but following your lead. I lived in Seattle during the '90s; the years of bridge and other civil engineering failures. Of course, this is the city a couple dozen miles north of the famous Galloping Gerdie, the suspension bridge in Tacoma, WA that went into resonance and self destructed in a storm. While I was there, the Hood Canal floating bridge tore loose during a storm, Seattle's I-90 floating bridge sank, the traffic stop on the 520 floating bridge raised unexpectedly (and as I recalled, killed a driver) and about a mile north of that bridge, the new construction in the UW Husky stadium fell down.

The sinking of the I-90 bridge was the one that really got me. I was working at MARCO at the time, doing stability tests and writing the reports for fishing boats operating in the Bering Sea winter where adhering to those reports and not overloading the boats was life and death. I was using the latest versions of the high end stability software created right there in Seattle. (I would hit impasses trying to model in the boats in our shipyard, talk to the creator on the phone, he would make up a script that would work and I would run over to his house and get the new program.) The I-90 bridge sections were hollow concrete blocks that floated with the roadway above. The roadway was being torn down and the debris temporarily stored inside the section. (They had cut access holes in the sides. No one paid attention to the fact that the holes were on the south side of the sections and that winter storms in the northwest usually come from the south; that waves could well be several feet high. Before the storm, they had loaded the sections with so much debris that the cutouts were just 10" above the water!

This being Seattle, all anyone had to do to save that bridge was - go to UW's department of Naval Architecture and ask a professor there if a student could be borrowed to model the bridge into BHS (Basic HydroStatics - the ship modeling and stability program). The would have cost the State, contractors and everybody else exactly zero $$s. The student spends a week (as a raw beginner) to model the program and in week more will be able to tell everyone exactly how much water is allowed in the section if it is loaded to "here" before it sinks. Rocket science? No this is Archimedes 2000 years ago. The student could have done the calculations faster by hand but the model would have had real long term value. (There is a patent I share with that university. I approached a mechanical engineering professor with an idea, he put four students on it and it happened.)

I could have modeled and run cases for that bridge in an (easy) afternoon, but I would have demanded $20/hour. To lose a bridge to the cost of millions in the most naval architect heavy city in this country for violating the most basic principle? Really? (The math involved is far simpler than Newton's falling apple.)

Rant, rant. I haven't thought about those bridges in years!

A bridge singing in the rain? I like it!

Ben
Cosmic Kid

Posts:2146

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10/03/2016 02:22 PM
Posted By Nicholas Arenella on 10/03/2016 10:18 AM
Wow, interesting analysis. What blows my mind are aero bars. What I mean by that is that for decades nobody figured this out. There's no technology involved, just the shape of some handlebars. I even, will occasionally put my forearms on the tops of my road bars, and can instantly feel the difference. I'm surprised nobody stumbled upon this pre-LeMond.


They did....they were called "triathletes".
Just say "NO!" to WCP!!!!
longslowdistance

Posts:1474

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10/03/2016 07:38 PM
We have a winner!

Cycling was so hidebound.
Merckx's hour record bike had narrow drop bars, they did have a clue.
Nick A

Posts:523

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10/04/2016 11:10 AM
LSD: But the narrow drop bars are hardly the forearms a few inches apart position. Did they know about this position, and it just wasn't legal? I mean, you could have adopted this position pretty early on in the development of the bicycle, yet nobody did? Or if they did, I'm ignorant. As I recall, at least with any widespread usage, it started with cow horns then "aero bars" in the '80's. Google shows varying dates, but it looks like the first usage of forearms close together was in a 1984 in a RAAM race.

CK: LOL. True.

79: I hear ya. I did some bridge inspections in NYC. Oy. How about this. We flagged a bridge because a subway car in a rail yard under the bridge had taken out a column. So the cops thought, lets let the heavy trucks over the weight limit drive onto the bridge, get a few of them stopped in the middle, and then ticket them...instead of not letting them on the bridge in the first place.

N

Nick A

Posts:523

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10/04/2016 11:40 AM
Hmm, edit button now showing up? So, anyway: edit...

LSD, I wasn't trying to say cycling was hidebound. I was just marveling at how sometimes something so simple takes so long to get discovered. Complex rim and frame shapes take more recent technology, but just from personal experience, just putting the forearms (very) close together makes an instant and noticeable difference as compared to deep in the drops, even with narrower bars. I just think it's cool to think about,how nobody "accidentally" put there arms like this in the '60's, '50's, 40's, and noticed this as well, or if they did, nothing seemed to have come of it that I can find until the '80's.

N
79pmooney

Posts:1735

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10/04/2016 12:29 PM
Nick, with non-aero brake cables, you better know you will never need the brakes! You will have to sit up. pull your hands behind the cables then reach forward should you need to slow. So there was more disincentive to do the forearms on the tops.

Ben
Cosmic Kid

Posts:2146

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10/04/2016 03:05 PM
OK, leaving aside the overall design of the bike, this is some REALLY impressive engineering....wow. Would love to see Cervelo bring that kind of adjustability to a road bike!

https://player.vimeo.com/video/184688849
Just say "NO!" to WCP!!!!
longslowdistance

Posts:1474

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10/04/2016 05:05 PM
Nick, but it was hidebound! I was one of those hairnet wearing traditionalists. I know the animal. Very un-accepting of the nontraditional.
It took triathletes thinking outside the box to substantially move the technology forward, and an American embracing the tech in such a spectacular way (winning the Tour when it seemed lost) to help accelerate acceptance of new tech.
(As for doping tech, cycling has always been open to new ideas.)


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