Helmet field testing? CdA impact

[Osiris]

Those guys know a lot over there. Take what I write with a huge grain of salt. But, it is also important to understand that individual response to training regimes vary.

I would personally use longer and longer intervals over a period of months that cover the time of the race (about an hour). You have to get your brain used to the discomfort. Specificity, specificity, specificity. The ability to burn lactate is part of what you are training.

You could start with shorter intervals, say 6x5 minutes. Then 5 x 8 minutes. 4 x 10 minutes eventually working up to 3 x 20. The intensity of efforts obviously declines as the time interval increases. I seem to recall Andrew Coggan doing something similar recently and claimed it got him in the best shape of his life. Not sure it if was UKTT forum or Slowtwitch (before they banned him). The reason I think this might work for you (building up the time duration hard efforts)? An hour at threshold is hard physically and mentally.

I've done the 12 mile TT several times now, and I know that once I find that zone where I'm not using up more oxygen or burning more fuel than my body can replenish, I can just stay there all the way to the end. The trick is finding out exactly where that zone is, and unfortunately I've only been able to discover that at mile 10 or so. It always feels like more than I can manage until I realize that it isn't, but by then it's too late to make up for it. It's very frustrating to realize that had I pushed just a tiny bit harder from the start, I could have cut my time by several minutes over a long distance.

 

[ed72]

This aero testing is not easy.

I spent two hour yesterday with mixed, inconclusive results. I am pretty sure I screwed up. Experimental error.

I use a hydration bladder. On some runs, it was unbeknownst to me dangling down the back of the bike flopping in the breeze. After an hour of tests, I was thirsty and reached back and the hose wasn't where it was supposed to be. That is how I found it flopping around. I don't think the bite valve was hitting the rear disc, but possible. If this was the sole reason for differences in the runs, it is amazing. It was 11 watts at 26.3 mph. 2 feet of hose and a bit valve. I did not get to the helmet testing part. Something additional came up.

I am starting to recognize that I lack perspective/experience to have good judgment. Can a hose hanging down like that have such a relatively large effect? The effect on CdA was 0.008. Mama Mia

The tube length times width is 0.007 mm^2. The bite valve is 0.001 mm^2. If I model the tube as a stationary cylinder and the bite valve as a short cylinder, the coefficient of drag for each is 0.82 and 1.15, respectively. Multiply and adding gets me to 0.007, or pretty close to what I measured. Using the same approach calculating the area and looking up the cd, my handlebar mirror is about 0.004 or about the advantage of my fancy, smancy wheel over the Flo60

https://en.wikipedia.org/wiki/Drag_coefficient

 

[ed72]

In effect, the dangling hose added 20 seconds to my 20:00 minute TT. Ouch.

 

[ed72]

he reservoir, or like the 900ml bottle it gives more space to race self supported. One aero tip with drink systems such as this one is to make sure that you don't leave a very long straw dangling in the wind - with previous riders we've found that too much of an exposed straw can cost up to 3.5w at 40kph! For Jess the drink system wasn't too bad, but was still slower than nothing at all - costing 1.8w at 40kph and 0.8w at 30kph.

The straw on a Tri setup on the bars isn't nearly as long as the hose I referenced, so, the effect could be actually worse than I estimate. I know it is important to have the helmet straps tight. For sure.

https://www.aero-coach.co.uk/water-bottle-testing

 

[Osiris]

This aero testing is not easy.

I spent two hour yesterday with mixed, inconclusive results. I am pretty sure I screwed up. Experimental error.

I use a hydration bladder. On some runs, it was unbeknownst to me dangling down the back of the bike flopping in the breeze. After an hour of tests, I was thirsty and reached back and the hose wasn't where it was supposed to be. That is how I found it flopping around. I don't think the bite valve was hitting the rear disc, but possible. If this was the sole reason for differences in the runs, it is amazing. It was 11 watts at 26.3 mph. 2 feet of hose and a bit valve. I did not get to the helmet testing part. Something additional came up.

I am starting to recognize that I lack perspective/experience to have good judgment. Can a hose hanging down like that have such a relatively large effect? The effect on CdA was 0.008. Mama Mia

The tube length times width is 0.007 mm^2. The bite valve is 0.001 mm^2. If I model the tube as a stationary cylinder and the bite valve as a short cylinder, the coefficient of drag for each is 0.82 and 1.15, respectively. Multiply and adding gets me to 0.007, or pretty close to what I measured. Using the same approach calculating the area and looking up the cd, my handlebar mirror is about 0.004 or about the advantage of my fancy, smancy wheel over the Flo60

https://en.wikipedia.org/wiki/Drag_coefficient

I'm reminded of a case way back in the 1970's when a certain marathon runner who was the overwhelming favorite to win the Boston marathon ended up narrowly losing it. Some engineers at MIT decided to find out why. Their calculations showed that if he'd only cut his long hair to a normal length, it would have reduced his CdA enough to guarantee the win. I always think about that when I'm out performing tests which to the great majority of cyclists seem just a waste of time.

By the way, two interesting things I remember from the aero testing done by the British time trialist I mentioned earlier, were that removing his front derailleur reduced drag by ~2 watts, and that clothing was often the single biggest contributor to drag. Aside from helmet testing and being sure to wear my tightest jersey, I really haven't paid much attention to clothing. Maybe it's about time I don my skin suit and do some coast down tests.

 

[ed72]

clothing was often the single biggest contributor to drag

Definitely true on an upright based upon lots of testing.

I suspect a huge reduction can be made using 130 mm cranks and shoe fairings. I have searched for good aero testing on bents, I never found much other than Cruzbikes. Most of it is more like, I changed my seat and I used to huff and puff going down my road, the new seat is much faster. I like how Larry did his testing.....lots and lots of laps removes variation. If I had a track, I would do that too because at least you are also getting training in.

 

[ed72]

In case anyone is crazy enough to ever read this post.

I did five runs yesterday, each run consisting of three back and forths on a pipeline within a neighborhood. Each segment is about 1km long and drops 90 feet and then a turn around at the cul de sac and drop back down and back up to the start, three times. I used Chung analysis tool in GC

I had previously found that the large Vanquish helmet with shield was slower than the large with Shimano glasses. I even went back and rechecked that data.

I had noticed that the gap from the shield to my face was quite large and I felt as if I was swimming in the large helmet. I lost one of the shields and rather than pay $70 plus shipping for a replacement shield, I found Medium with shield for $150 with shipping. Voila.

Yesterday's multiple tests showed the shielded medium helmet slightly faster by 0.003 m^2 over the glasses. Maybe 0.1 mph at TT speed, not huge (I did not calculate, just giving context....). The medium is also more comfortable. The lower edge of the shield just barely touches my cheekbones whereas on the large, I can fit my finger in there and it just has to be catching wind. The shield has many practical advantages, so, the shield it is for me. The difference between the large and medium with shield might be 0.006, now that would significant. It just takes too much time and effort for me to do a direct comparision of the large to the medium when in fact, I decided the medium was more comfortable. Logically, bigger is slower. So, I am not going to take the time to test plus the hill is 8-10% and it is almost like doing a Tabeta workout.

 

[Osiris]

Just got back from more helmet testing. I made the mistake of riding on an unfamiliar trail which other riders assured me was perfectly flat. It isn't, and as a result I'm going to have to spend a lot of time extracting the flat portions of all the segments to do multiple run comparisons with both helmets. I'm tempted not to even bother, and just repeat the test on my favorite trail tomorrow where I know the grade is perfectly consistent.

One thing I do know for certain now is that the enormous aero advantage the Eolus helmet has over ordinary road helmets at very high speeds (35 mph+) didn't materialize at slow speeds. Coasting down the bridge with a starting speed of 5 mph, I hit top speeds of 19.1 - 19.4 mph with both helmets on numerous runs. There was no measurable difference. I think I used less power with the Eolus at 23 mph, but I need a flat section of trail that's at least a mile long (preferably longer) to be sure. The difference will be small though, because while I did manage to average 1 mph faster on one segment with the Eolus, I was unfortunately averaging 22 watts more as well, so it's not a worthwhile comparison.

While it was a wasted effort as far as helmet testing goes, the one upside is that my new Garmin Virb camera is performing beyond my expectations. Unlike the previous model, it automatically extracts all the data from other paired devices like my speed/cadence unit, Vector power pedals (and heart rate monitor, if I'd been wearing it), and displays them on screen. Every other kind of G-metric data can be displayed as well. The video quality with automatic smoothing enabled is wonderful at 1080P. At it's highest resolution of 4K, it's like looking out an open window. I'll have more to say about this camera in a separate thread.

 

[ed72]

Coasting down the bridge with a starting speed of 5 mph, I hit top speeds of 19.1 - 19.4 mph with both helmets on numerous runs.

It is kind of a signal to noise issue. You need the biggest signal possible (speed), in my opinion. For instance, a 0.01 m^2 improvement at 18 mph might only get you to 18.4 mph but at 37 mph, it might get you to almost 39 mph on a coast down (both terminal velocity). The variability (noise) won''t make it hard to detect the real improvement at higher speed but not so easy at lower speeds.

I have been trying to track down inexplicable day to day variability. On any given day, I am consistent but not day to day. So, what do I change day to day? Some days I wear sun sleeves and other days, bare arms. Kit also varies, of course. I did 45 miles of testing today, the arm sleeves showed faster than bare arms...like around 21 mph vs almost 22 mph at the same power over 10 miles. No question. Faster in every direction and on every strava segment. I plugged the segment numbers into Gribble and also Chunged them. The difference was a bit more than 0.01 m^2 on Chung and closer to 0.015 by my hand calculations/estimations A bit surprised at how much of an effect to be honest and would need to repeat it again.

 

[Osiris]

What I'm trying to figure out is whether it's worth wearing the Eolus helmet on my upright, when my max sustainable speed on that bike is only in the 22-23 mph range, not the 35+ mph terminal speeds I reached during my coast down tests several weeks ago. It will definitely pay off on the M1, where I can hit speeds in the mid 30's in a sprint, but maybe the returns are too small to notice on an upright at much slower speeds.

I dug out my arm sleeves, but I think I may need to buy new ones. These are a bit too loose, and those wrinkles are going to create drag. Given your results with them, I'll definitely be wearing a tight fitting set of those when doing my TT's from now on. So if arm sleeves add 1 mph to your speed, what about leg sleeves?

 

[ed72]

So if arm sleeves add 1 mph to your speed, what about leg sleeves?

I dunno. I bought a set but did not like how they felt when pedaling. (I notice that Larry always seems to wear something on the shins, maybe for aero purposes or maybe to keep sun off.)

I am still surprised how much the arm sun sleeves did to my speed. It wasn't exactly 1 mph, a little less. I guess my arms are pretty hairy. I guess I'm skeptical. But 22.5 miles up and back with sleeves and then repeat bare armed. There was only 2-3 mph wind.....very barely detectable. A couple examples. Similar power but significant speed differences

8.64 mile segment

21.0 at 127 watts vs 22.1 130 watts

5.23 mile segment

21.6 at 141 watts vs 22.3 at 138 mph

 

[ed72]

If I get a chance (calm day and time), I'll go over to my half pipe and Chung the sleeves and some leggings. I do remember reading a Top Triathaloner saying leggins or maybe it was knee socks were worth something 7 or 10 watts at his speed, I assumed he did not shave and did not doubt it but maybe this comparo was to shaved legs. If you think of the pedal stroke on a laidback bent, the shin from knee to ankle sees most of the wind. I theorized that my helmet should be just above the knees at t Ihe top of the stroke so that it is in relatively undisturbed airflow and keeping the bottom of the stroke in the already messy flow thru the frame and derriere. No need to screw both up. With 130 mm cranks, one could really get it dialed in at both ends but I am sporting 175 mm babies.

 

[Osiris]

I found some tight fitting arm sleeves at a local bike shop, so I guess I'll be testing them out tomorrow.

No luck on today's coast down tests. I found a short but steep hill which accelerates me to ~25 mph by the time I reach the bottom, but once again both helmets performed the same. Eight tests, and each result was within a hair's breadth of the others. I think the problem in both tests is that the descents were too short and too steep, which makes the acceleration from gravity alone so great as to mask the effects of aerodynamics. By contrast, the slope on the back side of Sugarloaf wasn't as steep, and the distance traveled was far longer.

The only good thing that came out of all this was that I think I've finally figured out how to climb efficiently out of the saddle. I never could get it right before, but this morning I slowed down the cadence quite a bit and got the timing right. The power output was only about 700 watts, but the amount of torque I was putting on those cranks was unreal. I'm surprised they didn't snap off! I'll have to practice this some more.

 

[ed72]

Professor Chung very generously gave me some tips to better maximize the sensitivity of testing on my half pipe by really varying the speed at both ends. I wanted to share a few things he said (hope this is not not cool)

Interestingly, I mentioned my observation with the bladder hose. He saw the same effect himself and had the same shock until he did some calculations.

He also said that with his experience with world class record holders and top athletes, very small things matter and that they have to pay close attention to everything. Funny that sometimes I am slippery and other times not. Small things matter a lot. Who knows, I have so much junk dangling off my bike for randonneuring that that alone could be a source of variation. I am pretty sure that if the disc covers come loose, it is like a parachute. I have seen this a couple times and am thinking of hot gluing or something like that to hold them on more securely.

WRT helmets, I am now going to focus on testing my head angles. (I should have just spent the money on wind tunnel instead of an expensive plane ticket to Paris)

 

[Osiris]

I dropped off my car this morning to have new tires put on and rode the bike back. I used that opportunity to test the accuracy of my Garmin Virb camera now that I've put on a wheel mounted speed sensor. When relying on satellite transmissions to calculate my speed, I noticed a lot of lag time; now it seems to pick up changes in speed right away.

I was a bit puzzled that I was averaging close to 300 watts just to maintain 22-23 mph on the way home, but then I realized that I was wearing a floppy t-shirt and shorts in place of my skin tight riding suit. Amazing how loose clothing alone can generate so much drag even at a fairly modest speed.

 

[ed72]

Those cameras with the overlay of speed, power, etc. are nice.

Even just unzipping your bike jersey adds a lot of drag. Baggy teeshirts and shorts? Doesn't surprise me at all

I went on a hilly 75 miler with three flats. The only redeeming part? So many cars and riders stopped to offer help, give me water, drive me to a bike shop. On one flat, a homeowner came over to offer tools and to bring his compressor over because I "been there a long time" to which I just said, "I'm slow". My Italian wife reminds bad things happen in threes. So, I should be good for a while.

Started along a stretch of road and remember I used to have or might still have the KoM. Decided to let it rip. Crushed it. 1.78 miles in 3:18, next closest is 3:44.

Guess I am starting my taper although I wasn't planning on it. Only rode 265 mi and 11,000 feet last week. Had been in the 320-380 miles and 15,000+ feet per week. Should have time to do more aero testing ala RChung

Of course British Airways pilots are probably going to strike. And who am I flying to Paris for Paris Brest Paris. You guessed it

 

[Osiris]

I'm developing a phobia about flats. There has been a rash of them on our group rides lately, and just yesterday the outer layer of one of my car's tires ruptured and partially separated, exposing the steel mesh inside. It's a miracle that the tire didn't explode. The set of Vitoria Rubinos on my upright are about done anyway, so I think I'll go back to tubeless self sealing tires. I've already got them on my V20, which is the only one of my bents that sees a lot of road use.

The data overlays are cool, but I'm not sure how useful these films are as a training aid. It just takes too long to find the part of the video you want to examine when trying to determine say, power output vs. speed. With Strava, I can just go to the Analyze tab and drag my cursor to isolate the parts I want to look at. I also don't have the faintest idea where to mount the camera to any of my bents. The old Virb I used many years ago was much more aero; the new one is just a brick. Put that out in front, and I can just imagine it creating 5 watts or more in drag. No thanks.

 

[ed72]

Two of the flats were my fault. On two of them I was bombing down into a small hill over an ancient bridge on roads I had not ridden in 20 years. The pavement to concrete transition on the bridge was more of a 1 inch lip and my biggest failure, I did not air my tires before riding. I was riding pretty hard, ironically over by Trump National in Bedminster, and into the hills. I used to be able to average 18 mph on my upright on these types of roads. I averaged 16.2 over 75 miles with a touch over 60 feet per mile of climbing but lots of very steep hills and lousy descents where I had to control speed. The third flat was a defective tube at the seam, which techncially is also my fault for not proving the tube before putting it into my spares. For the past 3 months I have been working on climbing and skills in the hills. The Viscoset headset has helped and I really worked on my brakes. The Tektro 725 brakes are not easy to adjust and I found that the adjacent pivot point on both must have had glue used for grease out of the factory. My next machine will probable have discs or sturmey archer hub brakes.

I am still afraid of puncturing on a bent after going down once from a puncture. I learned a technique that works for me. When I get a flat and know it, I sit up and unclip. The balance is greatly improved this way. On a long ride in southern florida, it was dark and raining cats and dogs and a metal grated bridge popped up. I did my sit up and unclip. I barely kept it upright but a few uprights did go down. I have decided to cross all metal grated brides that way nowadays. They can be slimy.

WRT helmets, I am going to try running experiments with different angles of my head but controlling that will be problematic. Maybe, just run the test with chin to chest and then the opposite extreme.

I read a paper recently discussing the aerodynamics of different textiles. What works at slow speed doesn't work at high speed. It turns out that fuzzy wool is pretty aero at slow speeds (say 12 mph) but horrible at high speed (I know that one). Also, Chester Kyle was quoted as saying unzipped jersey increases drag by 40%!!!! RChung told me the drag was very high on an unzipped jersey on a bent and that he keeps his zipped to the top. I also read some TT racers and Tri who adamently claim long aero socks or compression sleeves are much faster. I do have compression calf sleeves to try.

This week is probably my only chance to break 20 minutes for 10 miles. I am pretty sure I can do it. Next week is too close to PBP and after PBP, I am going to detrain.

 

[Osiris]

If you think your M5 is a handful when flatting, you should try it on a V20. You'll experience a total loss of control if the front tire flats, even at ridiculously slow speeds. By contrast, I blew a front tire on the M1 at ~30 mph after hitting one of those metal transition strips on a bridge, but managed to coast to a stop without any drama. There was a 2" long cut in the sidewall, so we're talking instant deflation, not a normal puncture like I experienced on the V20. That's the main reason I decided to switch to tubeless self sealing tires. The weird thing is that back in the '70's, I would ride my 10 speed every day on horrible roads, but never had a single flat. Now they seem to occur every two months or so, despite the roads and trails being much smoother here.

Unfortunately all my jerseys were bought at a time when I weighed 180 lbs. Now that I'm down to 165, I feel the material start to flap in the wind on my sides, shoulders, and sleeves. It's not bad on the bents, but very noticeable on uprights. I don't understand why bare skin does so poorly compared to fabric. Surely the skin is at least as smooth, if not more so. Lots of local TT and Tri racers wear compression socks, but I was told it's because it aids muscle recovery. I have a set for that purpose, but they're so tight around my calves that I was afraid they'd cut off circulation, so I never wore them when out riding. I may have to try them on the bents along with arm sleeves to see if it makes a difference.

10 miles in 20 minutes is something I can only dream of. If I could manage that, I'd be beating the fastest time trialists in the area. Maybe one day...

 

[ed72]

I don't understand why bare skin does so poorly compared to fabric. Surely the skin is at least as smooth, if not more so.

The extent of improvement depends on the fabric design, fit, wrinkles. Skin is too smooth for surfaces directly opposed to the wind like biceps, shoulders, etc

One of my skinsuit has smooth fabric up to the elbow and then rough ridges or perhaps one could call them trip layers from there to the shoulder. it really is not optimal for a bent position for several reasons....anyway. We try to minimize the wake behind us. If you get onto the wheel of a velomobile for instance, there ain't nothing coming off. It is not just the shape but the motion within the detached airstream that causes increase drag. The idea is airflow has more disruption and the votex at the back is nastier for skin vs fabric.

http://www.ero-sports.com/2017/index.php/ero-insight-blog/15-why-skin-is-slow