July 28, 2014 Login  


these newfangled aero helmets...
Last Post 04/22/2014 04:16 PM by Keith Jackson. 95 Replies.
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Cosmic Kid

Posts:985

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03/29/2014 01:51 PM
OC, you can test aerodynamics of helmets by yourself....no wind tunnel needed.

Find a nice flat 1K course on a calm morning. Hit the start at a given speed, hold constant power for 1k. Lather, rinse repeat. Change helmets....repeat process. Differences are real, measurable and significant.


Just say "NO!" to WCP!!!!
79pmooney

Posts:1019

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03/29/2014 05:15 PM
Funk, doesn't that faster helmet get you to more beer and more and better choices of pie? And isn't that a more real gain than say 6" of podium elevation?

Ben
Ride On

Posts:414

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03/29/2014 05:39 PM
CK is this math correct for the test you want OC to run ? For total change in CdA of 0.01 he should see about a 5watt delta , assuming OC can hold about 25 mph. Two things make this test really hard to do. 1) exact same speed from test to test. Not sure about you but I find that almost impossible to do. My speed will vary +\- 0.5 mph no matter how close I try and hold it. 2) assuming he can hold the same speed, he has to hold his body, head, arms, feet pretty much everything in the exact same position from one test to the next. Really, really hard to do since you get no feed back if you change anything. There will be no number on a screen to watch to tell him he held his finger out in test # 2 It's easy to debate this stuff, it is really really hard to test it. The point is the guys doing the tests have the best data have a vested interest in the results. You don't spend a ton of the bosses money and tell him at the end of the day, that was fun but we didn't get any results that mean much.
Dale

Posts:439

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03/29/2014 09:16 PM
Posted By Cosmic Kid on 03/29/2014 01:51 PM
Differences are real, measurable and significant.



Mike? Mike Sinyard, is that you?

CK, you know I love you man, but that is such a load of hooie. The claim of 2 meters in a 200 meter sprint doesn't even begin to pass the sniff test.

While I do generally agree with the premises that given a choice pick the more aero gear there are other factors--

Cost

Aesthetics

Fit

Ventilation-- in the case of helmets

Stability-- I sold some wheels that were wonderfully fast but scared the crap out of me in gusty side winds

Ride quality-- I'll take a better ride where I'm fresh(er) at the end of a race as opposed to a marginally faster frame set that's beat me up for several hours

Cosmic Kid

Posts:985

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03/29/2014 09:26 PM
Ride on - you are arguing both sides of the coin. You are claiming that the helmets don't make that big of a difference, but then you are worried about OC "holding his finger out" on test #2. That would imply that minor differences in an aero profile make measurable differences in results.

Given that an aero road lid has been shown to have a major impact on an aero profile, then it stands to reason that if you are worried about a finger hanging out, than an aero road helmet will show a significant gain in speed. Thanks for proving my point.

The reason you limit the test to ~1k stretch of road is precisely so you can eliminate as much of the variables as possible. And you don't just do it once.....you do it multiple times with both lids and compare the aggregate results. And I didn't say hold a constant speed, I said constant power. Set your computer for a 10" avg display and it is much easier to hold power constant.

Pretty basic stuff.
Just say "NO!" to WCP!!!!
Ride On

Posts:414

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03/29/2014 10:50 PM
The point is , sticking your finger out will change your drag more than the differences between two helmets . I know you know that. The time difference is going to be around 1 sec. That is really hard to measure accurately with a guy on a bike doing 25 mph
Cosmic Kid

Posts:985

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03/29/2014 11:24 PM
Posted By Ride On on 03/29/2014 10:50 PM
The point is , sticking your finger out will change your drag more than the differences between two helmets . I know you know that.


You're serious?

No, I don't *know* that.....but I'd like to see your data that shows it.
Just say "NO!" to WCP!!!!
Keith Richards

Posts:694

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03/30/2014 12:45 AM
What do you call significant CK?
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Ride On

Posts:414

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03/30/2014 08:13 AM
No one has "test" data on sticking your finger out because they can't then market you something to warrant the test. Why waste test time which is expensive for no company gain and in some ways could be used to unsell some of your own products if people find out the numbers you have been telling them is all noise.

If I didn't feel wrong about using the companies CFD software and computer time to run a cycling flow analysis I'd whip you up a nice comparison of finger in versus finger out. I'd make enough assumptions that I'd prove myself right.
Cosmic Kid

Posts:985

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03/30/2014 08:21 AM
It depends on the rider and their position....but a drop in power of 20w (or more) can be pretty common.

Now those kinds if numbers are usually seen with a full TT lid. But as noted previously, the Evade tests pretty close to some TT helmets. Jordan Rapp (arguably the best US male triathlete) had a 5w difference between the Specialized McLaren TT helmet and the Evade. Pretty small delta (but also significant enough for him to chose the McLaren when allowed).
Just say "NO!" to WCP!!!!
Keith Richards

Posts:694

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03/30/2014 09:03 AM
20 watts under what conditions?



To me a 5 second delta in a test such as this is not significant. Bike is being held straight up and down with no wobbling. In the real world, anything I save by taping up my helmet I would immediately give back if I reach down and adjust my cycling shorts. And just to remind you, we are talking about these mass start aero helmets, not TT specific wear. Also, as I pointed out last season, not a SINGLE aero lid was worn on climbing days in the big stage races. Ventilation trumps aero when the road goes up.

Sweating this stuff at the level everyone here races at is just silly. Great for the bike business tho. Shop to you drop!
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Ride On

Posts:414

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03/30/2014 09:43 AM
Not many "areo" lids today in Gent Wevelgem. They seem to pull them out when it's cold , other than that they stay in the truck.
Cosmic Kid

Posts:985

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03/30/2014 09:44 AM
??? You are comparing one aero lid against another in that pic. IOW, you are trying to decide which is "fastest" among already proven "fast" helmets. I agree that such an endeavor is a fool's errand.

But that isn't what we are talking about - we are talking about significant differences between a standard road helmet and an aero road helmet (which as noted is close to being on par with some of the best TT lids).

As for your "pulling on your shorts" example, we have discussed this before. They are mutually exclusive and not related. If you are gonna tug on your shorts, you are gonna tug on your shorts. Has nothing to do with what helmet you are wearing. And in either case, if you tug on your shorts, having an aero lid will still let you be faster when you do it.

Tests have shown that wearing aero helmets does not increase core body temperature any more than a normal helmet. Now, that does not mean it doesn't "feel" hotter because you lose some evaporative powers and it seems like you are sweating more (you're not....it is just not evaporating as much). But perception is a powerful thing...and this is why riders often dump the aero lids for the MTB stages.
Just say "NO!" to WCP!!!!
Ride On

Posts:414

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03/30/2014 09:54 AM
In E3 the other day Sagan took the win over his 3 breakaway companions each who had "aero" lids on. Silly man he should have listen to the CdA numbers.

http://www.cyclingnews.com/races/e3-harelbeke-2014/photos/298613

Orange Crush

Posts:1146

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03/30/2014 10:39 AM
CK - please provide a reference showing that 20W difference. And not a full TT lid.

Based on a well known MIT reference study the advantage of a full TT lid over standard helmet at TT speeds is maybe 12-18W.

At more typical road race speeds the theoretical advantage of a full TT lid drops to 7-10W.

An Evade would be below those last numbers (its not a full TT lid) AND under idealized wind tunnel conditions.

So you're looking at 5W under best conditions.

About enough to reverse the effect of pinning on a race number.
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