Aero Time Trial helmet

[John Tolhurst]

In another thread (http://www.cruzbike.com/phpbbforum/viewtopic.php?f=10&t=1218)

Mark B wrote: I was thinking if I had an aero hat, there was no way he could keep with me!!!

Has anyone got any suggestions for what aero helmet we should find for Maria? The one I saw on Contadora (?) on the tour had an integrated visor, nice and smooooooth, I like it, but what happens when the head orientation is different?

 

[JonB]

johntolhurst wrote: In another thread (http://www.cruzbike.com/phpbbforum/viewtopic.php?f=10&t=1218)

Mark B wrote: I was thinking if I had an aero hat, there was no way he could keep with me!!!

Has anyone got any suggestions for what aero helmet we should find for Maria? The one I saw on Contadora (?) on the tour had an integrated visor, nice and smooooooth, I like it, but what happens when the head orientation is different?

I have extended the visor on my helmet using the shadow from a peaked cap. The wind does take it. The original visor has holes to guide the wind over the top, and something that prevents the sun from coming through the holes.

You could get a aero helmet without the visor and just use better sunglasses. I can _NOT_ recommend Randolph Aviator for bicycling since the speedwind gets your eyes to run with tears.

 

[Mark B]

I was joking about the aero hat. If I were as young and fit appearing as this guy was, there's no way he could have hung on. I don't think the helmet would have done much, in this instance.

Mark

 

[jeebus]

This topics reminds me, does anyone know the details of maria's bike setup?

I remember john asking about interest in disc wheels recently and at least off-hand I didn't guess it would be that big of a win. But since maria seems to be the most serious racer we've got on the bike so far, I am curious what her setup is.

Mark

 

[John Tolhurst]

I've never see Maria's bike in the metal, I made it yellow to add something special to it. It is shimano ultegra with origin-8 gary bars and American Classic wheels with possibly bladed spokes. I think Jim put 140 psi tires on their bikes. Maria also ran q-rings. Maria's Silvio is one of the first batch of 12 produced.

 

[John Tolhurst]

I like this one, but its not for road use! http://www.gathsports.com/productsingle.php?id=61

I like it because it gives a full face aero shape with the head in normal position.

 

[JonB]

Mark B wrote: I was joking about the aero hat. If I were as young and fit appearing as this guy was, there's no way he could have hung on. I don't think the helmet would have done much, in this instance.

How come you didnt suggest she got a PowerRanger suit? ;-)

 

[Mark B]

JonB wrote:

Mark B wrote: I was joking about the aero hat. If I were as young and fit appearing as this guy was, there's no way he could have hung on. I don't think the helmet would have done much, in this instance.

How come you didnt suggest she got a PowerRanger suit? ;-)

:lol: :lol:

Mark

 

[JonB]

I was thinking that even the hair under the helmet may influence the aero dynamics. So maybe she should cover her hair with a swimming hat?

 

[JonB]

Maybe the Ekoi CITY E+ Ecran Fume is the helmet you are looking for. http://www.ekoi.fr/casque-ekoi.php?var=691

 

[buyagain]

Its kind of like dealing with the mystery of Excalibur. If anyone here can explain the reason for dimples on a golfball we might then approach the solutions.

Bob

 

[teacherbill]

buyagain wrote: Its kind of like dealing with the mystery of Excalibur. If anyone here can explain the reason for dimples on a golfball we might then approach the solutions.

Bob

I have been told that the dimples on a golf ball helps determines its flight. :?:

 

[buyagain]

teacherbill wrote: I have been told that the dimples on a golf ball helps determines its flight.

I know that nothing happens in this world until the teacher is taught. Boy am I full of something or what. LOL

PS Your answer is way too vague. If you are referring to some kind of guidance the answer is no.

The truth is that a golf ball's "shape" and "speed" requires the ball to turbulate (dimples are little turbulators) the air as it passes though to keep air attached to its surface. A smooth ball fails to do this and the air becomes detached from the ball in flight prematurely and aerodynamically looks larger and more draggy to the air as it passes though. I know its hard to believe but a round ball of that size is more draggy and slower than the dimpled version. I have not the slightest who figured this out for the golf ball but I guarantee The Man powered flight scientists ran smack into this phenomenon and designed for it in their slow planes. Imagine how surprised they were to discover that the Wright Brothers were aware of the slow air barriers and tested for it too. Indeed it was determined that the air foil of the Wright wing foil was superior in this slow flight regime than modern foils.
I said all this to show that the aerodynamics of helmets are in this regime as well and that what may look aerodynamic to the eye is not necessarily so at the low Reynolds numbers of a bicycle helmet .

PS Missed you Bill, I know you're busy.

 

[buyagain]

JonB wrote: Maybe the Ekoi CITY E+ Ecran Fume is the helmet you are looking for. http://www.ekoi.fr/casque-ekoi.php?var=691

Anytime anyone mentions "Fumes" I think of Mark Bs helmet. :lol: but I digress. don't I.

 

[John Tolhurst]

That would be great. How do I buy one for shipment to Australia?

 

[John Tolhurst]

buyagain wrote:
The truth is that a golf ball's "shape" and "speed" requires the ball to turbulate (dimples are little turbulators) the air as it passes though to keep air attached to its surface. A smooth ball fails to do this and the air becomes detached from the ball in flight prematurely and aerodynamically looks larger and more draggy to the air as it passes though. I know its hard to believe but a round ball of that size is more draggy and slower than the dimpled version. I have not the slightest who figured this out for the golf ball but I guarantee The Man powered flight scientists ran smack into this phenomenon and designed for it in their slow planes. Imagine how surprised they were to discover that the Wright Brothers were aware of the slow air barriers and tested for it too. Indeed it was determined that the air foil of the Wright wing foil was superior in this slow flight regime than modern foils.
I said all this to show that the aerodynamics of helmets are in this regime as well and that what may look aerodynamic to the eye is not necessarily so at the low Reynolds numbers of a bicycle helmet .

PS Missed you Bill, I know you're busy.

So what would we like as a prize for adapting that helmet for speeds of 20mph? Shall we cover it in fine scale inside out bubble wrap? hmm ... ?

At our speeds we actually want super smooth, don't we? who knows the answers to this kind of question?

 

[buyagain]

johntolhurst wrote: So what would we like as a prize for adapting that helmet for speeds of 20mph? Shall we cover it in fine scale inside out bubble wrap? hmm ... ?

At our speeds we actually want super smooth, don't we? who knows the answers to this kind of question?

In WWII slick was not important until 350 or so mph. Hence you will notice quite a few flat finishes on planes. In fact flat was superior in some cases. Flush rivets were definately a must though. Slick for a helmets don't hurt but it don't help either.
Jack Lambie the famous glider aerodynamicist described how he designed Motorcycle helmets by mounting helmets at varying positions on his front finder and running them up to speed. He coated the helmets with a simple solution that when dried the residue left marks where air separation and turbulence occurred. He would turbulate each area with a glued piece of thread 1/4" ahead of each failure and later designed it into the finished helmet. The solution was easy to wipe off with no residue.
So I'm saying most any acceptable helmet would be fine just do that test and you've but to ask me for the recipe. Heck just leave the threads in place. It might even psyche out the competition with weirdness. Some might even call it art with the right thread color.
PS a helmet is a different size and thus a different Reynolds number than a golf ball so the dimple idea is out, OK?

Regards
Bob
PS Jack was a bicyclist too.

 

[trapdoor2]

Considering the huge number of hours the top TT riders do in low-speed wind tunnels, I would submit that their goofy looking helmets are optimized for such things. IOW, we would do well to consider something of similar shape and finish. If turbulators and flat-finishes were the ticket, you'd see 'em on the start line for sure.

At low speeds a lot of strange things happen with surface flow. Golf-balls are not optimized to operate in our range. Besides, the dimples are there to optimize directional stability more than for drag reduction (though it is a design-criteria balancing act these days).

What Maria needs is less an aero-helmet than a very comfortable one. Riding 12hrs with one of those TT helmets would be a horrible pain in the neck! :roll:

 

[WhiteSilvio]

trapdoor2 wrote:
What Maria needs is less an aero-helmet than a very comfortable one. Riding 12hrs with one of those TT helmets would be a horrible pain in the neck! :roll:

I agree. And looking at the photo of Maria on her bike I'd reckon that the helmet she wore was pretty much as aerodynamic as a reasonable amount of money can buy!!

I would suggest taking some head on shots of Maria in her riding position, because I think there may be more to be picked up efficiency-wise with different handlebars. While the Origin bars are obviously good for everyday use, I have a belief that one's arms are spread out and create an inverted funnel, trapping air.
If the 'bars are the same width as the shoulders and the hands are at a point that is roughly level with the shoulders, then the arms are virtually pointing straight into the wind.

For wrist discomfort/pain reasons (and that's another story already covered in a thread), I went back to "standard" road bars, and by tilting the STI levers out just a little, I have no problems with leg contact during gear changing, but I feel I roll a little faster than I used to. At the moment I have even taken to putting my hands "up on the hoods", whilst going along on the flat and downhill, to accentuate the straightening of the arm, pointing them more. When I need to pull on the bars I "drop down" onto the grips again.

Just a suggestion.
And in relation to the front "Carbo-yoke", which is like a flat bar the wrong way into the air, I have thought that a piece of cylindrical "foam" with a slot down the middle, forming 2 Ds, joined on one edge of the D top or bottom corner, could be slid onto and maybe glued, taped, tied around most of the yoke, thus presenting an elliptical profile to the wind.

Regards,
John R.

 

[buyagain]

trapdoor2 wrote: At low speeds a lot of strange things happen with surface flow. Golf-balls are not optimized to operate in our range.

When you talk this way Trapdoor2 you make me think you don't read my posts. I already had a P.S.> as follows:

buyagain wrote: a helmet is a different size and thus a different Reynolds number than a golf ball so the dimple idea is out, OK?

trapdoor2 wrote: Considering the huge number of hours the top TT

Lets give credit where credit is due. I suggest you Find out Who Jack Lambie was. Vaguely referring to a TT bunch who might have been lucky enough to study under Lambie don't cut it. LOL Plus with that kind of logic I'm encouraged to think the "Cruzbike" itself should have already been developed by the TT bunch too. Exactly which of this TT bunch coulda-shoulda-aught to have already created all this stuff and solved the helmet problems. I specifically referred to a guy named Jack Lambie. Reading a little about him should temper your assessment admirably.

Don't blame me I'm just trying to stay on topic.
I guess we aught to blame Johntolhurst for posing this question in the first place, Right? Its a given that the consequences as per the whole is quite menial. But, none-the-less interesting for those of us who are curious enough to ask.

So maybe you'd like to go and create another thread about the other more important preparations. I'm cool with that. As long as you let me address the boundary layer disruption problem of curiously viscous and sticky characteristics of air responsible for parasitic drag in the relevant reynolds numbers of what is known as the 12 mile per hour barrier. I'm cool with that. ROTFALMAO

OK so, Most pies are round, right?

Bob

PS what was your point again, Trapdoor2. I forgot. LOL

 

[John Tolhurst]

trapdoor2 wrote: Considering the huge number of hours the top TT riders do in low-speed wind tunnels, I would submit that their goofy looking helmets are optimized for such things. IOW, we would do well to consider something of similar shape and finish. If turbulators and flat-finishes were the ticket, you'd see 'em on the start line for sure.

Yes of course. The problem is the angle of the head. Our head is rotated back a lot compared to a TT rider, so the tail is going off in the wrong directly. That's why I looked at the gath helmet, thinking we could add a tail at the right angle. But the gath helmet is not for road use. maybe we can get a regular TT helmet and try to wear it in a tilted fashion.

trapdoor2 wrote:
At low speeds a lot of strange things happen with surface flow. Golf-balls are not optimized to operate in our range. Besides, the dimples are there to optimize directional stability more than for drag reduction (though it is a design-criteria balancing act these days).

yes, no the bubble wrap suggestion was not in complete seriousness.

trapdoor2 wrote:
What Maria needs is less an aero-helmet than a very comfortable one. Riding 12hrs with one of those TT helmets would be a horrible pain in the neck! :roll:

But how many free miles would she get if she had an aero helmet that could be worn that time. Story time. I did a bunch of roll-down tests comparing prototype sigmas to the silvio, swapping rider, andn all that. For some reason I rolled down faster what ever bike I rode. That reason turned out to be the visor on the other guys helmet, (we think) since I was 10% lighter. Tricky stuff, but aero always wins out.