Test riding a true racing recumbent

[ed72]

I saw an interesting "result" happen with "rumpled jersey". I was at the A2 WindTunnel with Cruzbike a while ago. Jim Parker put his skin suit on (no small feat by the way) - went in the wind-tunnel, came out, switched to his super loose, flapping in the wind Jersey and go a lower cda value. That is where I stopped thinking about trying to pour myself into the skin suit. Not sure everyone would have the same result, but perhaps the skin-suit helps more when you are in the up-right position.

That is almost as interesting as the report indicating it is possible to go 24 miles per hour on 106 watts. On real roads with good tires and dual disks, maybe 140-145 watts to go 24 mph assuming bike and rider weigh 135 lbs, normal RHO, no drive train losses, and Crr of 0.0045.

I am sorry, there is no way Jim's baggy jersey and CdA of 0.230 was worse in a skinsuit. I do not believe it.

The other squirrely data is the 0 yaw vs 7.5 yaw power (extra 24 watts). I have never ever seen 7.5 yaw requiring more power than 0 yaw and it makes no sense scientifically. I saw several other anomalies when I read the report a year ago but kept my big mouth shut.

Something is amiss.

https://cruzbike.com/blogs/blog/cruzbike-at-the-a2-wind-tunnel

 

[3bs]

the great fun of stating the obvious and then dissecting it. wattage is the measure of mechanical power created by the body. the body is full of all kinds of mechanical variables even before we consider the biological ones. every bike will present a different geometry in itself. placing the body on that geometry creates a second layer of math. seat angle is just one of these variables. when i switch from bike to bike to trike my power and how i feel generating that power changes. and then as you all point out well, other factors like drag, pitch, weather course type also factor in what speed we can generate and then how long we can hold it. for me, my upper GI tract will not allow me to be as reclined as others. and my lungs are sufficiently trashed that they are limited in their functionality as well. these are just two factors when i am trying to go far and go fast. some day i may actually be 1. in good enough shape 2. weigh less, 3. be fully relaxed on the bike 4. be focused enough for all of the decimals to matter. i will see great improvements in my speed and distance just by getting rid of about 10 pounds of winter holiday cheer.

cant wait to try the m1 to see how it compares to m5 and v20 for me. then we will have the "average joe" data....

 

[LarryOz]

That is almost as interesting as the report indicating it is possible to go 24 miles per hour on 106 watts. On real roads with good tires and dual disks, maybe 140-145 watts to go 24 mph assuming bike and rider weigh 135 lbs, normal RHO, no drive train losses, and Crr of 0.0045.

I am sorry, there is no way Jim's baggy jersey and CdA of 0.230 was worse in a skinsuit. I do not believe it.

The other squirrely data is the 0 yaw vs 7.5 yaw power (extra 24 watts). I have never ever seen 7.5 yaw requiring more power than 0 yaw and it makes no sense scientifically. I saw several other anomalies when I read the report a year ago but kept my big mouth shut.

Something is amiss.

I was there and saw the data with my own eyes.
As far a yaw angles go. This is what I have been led to understand. Yaw angle of 0: This is what you would get on an indoor velodrome with basically no wind (other then what you are creating pushing through it). This is the best possible scenario.
If there is "wind", the Yaw angle is the angle that a virtual thread would be from you bike "line" when combining the angle of the actual wind and the wind you are making cycling through the air. The greater the angle the "possible" more drag that will be created, especially if you have a large frame or disc wheels.
This makes sense that it took 24 more watts to "ride" through a 7.5 yaw angle.
I was also there for this and saw them rotate the base to 7.5 degrees and then start up the wind tunnel.
The windtunnel measured more drag with the bike tilted at 7.5 front straight. There did the math - and it came up to 24 more watts.
...
If I am totally off-base with my definition and understand of Yaw angle and how it affects drag on a bike - please educate me. - always willing to learn more.

 

[Osiris]

Ed72, since you're a numbers guy, how many watts of resistance do you figure an idler wheel like the one on the M5 creates?

 

[McWheels]

Baggy clothes have been shown to offer an advantage, as the attached shows, somewhat unexpectedly. I would suggest this is to do with filling in the parts of a concave shape creating the most aerodynamic bluffs.

 

[bladderhead]

Sounds like 3bs has the same problems as me. If the lungs don't get you the belly will.

 

[ed72]

Ed72, since you're a numbers guy, how many watts of resistance do you figure an idler wheel like the one on the M5 creates?

I don't know.

IIRC Bram told me that putting a tube and pulling the chain up onto a pulley to keep the chain off the front wheel would cost 8-10 watts.

I would say the v20 has a fairly significant advantage over any rear drive recumbent in terms of efficiency.

 

[Osiris]

I don't know.

IIRC Bram told me that putting a tube and pulling the chain up onto a pulley to keep the chain off the front wheel would cost 8-10 watts.

From the photos I've seen, Bram's solution was just a guide tube. I've been using an idler wheel instead, but decided to remove it last week. I couldn't feel any difference when pushing the pedal around with my finger tip, but ditching the extra idler must have reduced friction somewhat. The placebo effect alone might be worth a KOM or two.

 

[ed72]

I was there and saw the data with my own eyes.
As far a yaw angles go. This is what I have been led to understand. Yaw angle of 0: This is what you would get on an indoor velodrome with basically no wind (other then what you are creating pushing through it). This is the best possible scenario.
If there is "wind", the Yaw angle is the angle that a virtual thread would be from you bike "line" when combining the angle of the actual wind and the wind you are making cycling through the air. The greater the angle the "possible" more drag that will be created, especially if you have a large frame or disc wheels.
This makes sense that it took 24 more watts to "ride" through a 7.5 yaw angle.
I was also there for this and saw them rotate the base to 7.5 degrees and then start up the wind tunnel.
The windtunnel measured more drag with the bike tilted at 7.5 front straight. There did the math - and it came up to 24 more watts.
...
If I am totally off-base with my definition and understand of Yaw angle and how it affects drag on a bike - please educate me. - always willing to learn more.

The tunnel must have had a problem that day.

24 mph on 106 watts would be a CdA of around 0.100.....nearly velo territory. Please correct me if wrong. Assumed rider and bike 135 pounds. Crr = 0.0045 (that is the best I can get with GP4000si with latex tubes on good roads, so, I used it....can get better with other tires), zero drivetrain losses, and RHO of 1.22. A good velomobile takes about 100 watts for 25 mph, approx.

WRT to -7.5 degrees of yaw requiring 130.5 watts whereas 0 degrees only required 106.4 watts to go 24 mph, do you believe either of those numbers? Seriously. This is a massive difference. I could almost believe the 0 yaw (CdA of 0.130 ish). If a mere 7.5 degrees of yaw really required 24 more watts, there is something seriously wrong. Normally the sail effect of one disc (or even deep wheels like Zipp 808) lowers total required power at 7.5 degrees and two discs should have an even larger effect. Look up test results from Tour magazin. They test wheels alone, bike and wheels using a mannequin (uprights of course). Once the yaw gets to 10 to maybe 15 degrees, flow separates from deep dish wheels and resistances goes up significantly over baseline; however, this separation isn't seen practically speaking in the really world with discs because real world yaw angles are rarely greater than 20-25 degrees at racing speeds where separation might occur on discs over 30 degrees (maybe). The sail effect with discs can be felt. They are just faster. Steering is a bear. At modest yaw angles, the wind can actually push you. Are you suggesting otherwise? If so, why would you ride with dual discs especially in windy races like Sebring. The extra 24 watts is especially odd because the tail box itself reduced drag at 7.5 yaw rather significantly. I just have never seen disc wheels increase required power at 7.5 yaw. Maybe my brain isn't working clearly. Just never saw it. If you can find the orignal research from Dupont in the 90's when the developed the Specialized TriSpoke, I seem to remember it explaining the sail effect rather well.

This is what the blog post said. It should be obvious that discovering well into testing makes culling out bad data rather difficult.

Unfortunately, many of the 75 separate “runs” that we did were invalid due to a rear-wheel clearance issue that wasn’t discovered until we were well into the testing day. Because of this, we didn’t get valid results for some of the items that we wanted to test.

I simply cannot believe a loose, flappy club jersey would be more aero than a properly fitting, quality skinsuit. I do not dispute that you saw the numbers. I dispute the validity of the test results themselves.

Aero wheels actually make more of a difference than the chart indicates. In a crosswind, the air drag of standard wheels goes up, while that of disk and deep rim wheels goes down.......In the right crosswind, the air drag of these wheels can drop below zero, the disks acting as sails to provide a propulsive force

Took me a while to find a recumbent specific source.

http://www.recumbents.com/wisil/brown/airdragformula.htm

 

[ed72]

Baggy clothes have been shown to offer an advantage, as the attached shows, somewhat unexpectedly. I would suggest this is to do with filling in the parts of a concave shape creating the most aerodynamic bluffs.

4 watts difference is well within the margin of error on this type of testing or even powermeter error. The head was also covered with a hat, which is likely a factor. You could be right about filling in the shape. But this example doesn't really apply to a normal summer club jersey vs. a properly fitting skinsuit. An Aerodynamic scientist would be better here. Surely there are places to induce some turbulence or at least that is why Zipp thinks with their new wheels. I can only say without reservation that my winter kit is much, much slower than anything I can wear in summer by far.

 

[ed72]

From the photos I've seen, Bram's solution was just a guide tube. I've been using an idler wheel instead, but decided to remove it last week. I couldn't feel any difference when pushing the pedal around with my finger tip, but ditching the extra idler must have reduced friction somewhat. The placebo effect alone might be worth a KOM or two.

I might have misunderstood him. I recall him saying to learn how to ride it and don't put the tube and the pulley up here because it will cost 8-10 watts at speed. Derailleur pulley tests show pretty low wattage, so, I dunno. I do know this. A fixed gear with no idler would be the most efficient on a rear drive.

The chain makes a racket over the idler and I have wondered as well. I'd need very well calibrated power meters at the crank and at the rear wheel. My two Powertaps differ by 4% from true. (one is 2% high and one is 2 percent low). Putting a valid measuring system together would be hard....at least for me. (I don't think the idler is more than a handful of watts lost)

If looking for a couple watts, investigate aero skewers.

 

[Osiris]

I might have misunderstood him. I recall him saying to learn how to ride it and don't put the tube and the pulley up here because it will cost 8-10 watts at speed. Derailleur pulley tests show pretty low wattage, so, I dunno. I do know this. A fixed gear with no idler would be the most efficient on a rear drive.

The chain makes a racket over the idler and I have wondered as well. I'd need very well calibrated power meters at the crank and at the rear wheel. My two Powertaps differ by 4% from true. (one is 2% high and one is 2 percent low). Putting a valid measuring system together would be hard....at least for me. (I don't think the idler is more than a handful of watts lost)

Guide tubes struck me as a poor solution, generally. They're noisy, create a lot of friction, and wear through after a time. My idler suffered from none of these issues, but after doing all this aero tweaking on the M1, the thought that I might be wasting a few watts with the extra idler horrified me. I had to get rid of it. It seems to have done some good already, judging by this morning's results. I crushed one of my two year old records, increasing my average speed by 1.3 mph. I'm convinced that ditching the extra idler was what did it.

If looking for a couple watts, investigate aero skewers.

I'm on it. The M1 is at a local shop having the BB slot enlarged, but once I get it back and properly dialed in, it's going to be fitted with a set of those aero skewers you recommended.

 

[Osiris]

The tunnel must have had a problem that day.

24 mph on 106 watts would be a CdA of around 0.100.....nearly velo territory. Please correct me if wrong. Assumed rider and bike 135 pounds. Crr = 0.0045 (that is the best I can get with GP4000si with latex tubes on good roads, so, I used it....can get better with other tires), zero drivetrain losses, and RHO of 1.22. A good velomobile takes about 100 watts for 25 mph, approx.

Based on my ride from a couple of weeks ago: on level ground over a distance of 3.5 miles I averaged 23.6 mph on 199 watts. Rider weight is 167 lbs + 23 lbs for the Vendetta (I think). New tires are Hutchinson tubeless and wheels are American Classic Argent Tubeless, so not exactly set up for racing. I also have an under-seat bag, which Jim claims saves a few watts. Does my speed/power ratio look pretty good, or could I squeeze another mph or so out of it with a bit of tweaking?

 

[ed72]

I did the about 66 miles up and back on the Van Fleet trail today and the extension down below I-4 at a steady 19 mph average on 105 watts average with a standard road jersey and my bike kitted for randonneuring (lights and big honking battery and other stuff). This is about 0.182 cda or thereabouts, the trail was pretty bumpy and Crr is a bit of a guess. It was also pretty windy.

23.6 mph on 199 watts is around 0.220-0.225. Unfortunately, I don't have a V20. It seems there would be room for improvement but I don't know where to look. Lower seat? Bottles behind the headrest? I think there are some special tricks to get the wicked low levels that Larry clearly squeezed out of it. My guess. Pure guess. Narrower bars would be big. The "splitter" or cover thing on the back under the seat would help a lot. The splitter thingie or whatever it is called on the front of the frame, probably not much. The whole back half of Larry's bike looks slicker but pure subjective. I also notice that Larry always seems to have arm covers and leg covers and many Triathloners have shown them to increase TT speeds by quite a lot. Also helps skin health. It is on my to do list to test, I have compression ones for my legs to see if they help in a number of ways. In short, I would look at pictures of Larry's ride with him on it.....I've been on his wheel, there is nothing coming off the back of his bike. Very slick.

https://www.gribble.org/cycling/power_v_speed.html

 

[Osiris]

I did the about 66 miles up and back on the Van Fleet trail today and the extension down below I-4 at a steady 19 mph average on 105 watts average with a standard road jersey and my bike kitted for randonneuring (lights and big honking battery and other stuff). This is about 0.182 cda or thereabouts, the trail was pretty bumpy and Crr is a bit of a guess. It was also pretty windy.

23.6 mph on 199 watts is around 0.220-0.225. Unfortunately, I don't have a V20. It seems there would be room for improvement but I don't know where to look. Lower seat? Bottles behind the headrest? I think there are some special tricks to get the wicked low levels that Larry clearly squeezed out of it. My guess. Pure guess. Narrower bars would be big. The "splitter" or cover thing on the back under the seat would help a lot. The splitter thingie or whatever it is called on the front of the frame, probably not much. The whole back half of Larry's bike looks slicker but pure subjective. I also notice that Larry always seems to have arm covers and leg covers and many Triathloners have shown them to increase TT speeds by quite a lot. Also helps skin health. It is on my to do list to test, I have compression ones for my legs to see if they help in a number of ways. In short, I would look at pictures of Larry's ride with him on it.....I've been on his wheel, there is nothing coming off the back of his bike. Very slick.

https://www.gribble.org/cycling/power_v_speed.html

I took a look at Larry's V20 when we met in Daytona, but the only big difference I noticed was the narrow handlebars. He's written elsewhere that this setup makes it very hard to control the bike, so I had to cross it off as a modification I would consider. The advantage my V20 has over every bent I've owned is it's "user friendliness", and I wouldn't want to sacrifice that. The tail box behind the headrest looks promising though; it adds functionality without any apparent downside. I'll have to PM Larry to see what other secrets he wouldn't mind sharing.

By the way, I performed some tests comparing different arm/hand positions this afternoon. It was a pretty crude test, which consisted of driving at highway speeds with my left arm/hand sticking out the window and approximating the two positions it was in when riding my M1. The angle of my forearm didn't seem to make much difference in terms of drag, even at 60 mph, but the difference in hand position had enormous effects. With my palms facing forward into the wind and my fingers curled as if wrapped around the grip, it felt like I was arm wrestling. It really surprised me how my hand caught the wind like a sail. By contrast, when rotating my hand 90 degrees, it felt like I'd taken it out of the air stream. 90% of the wind force pushing against my hand just vanished. I repeated the experiment about a dozen times, and the results were always the same. This may explain how I mysteriously picked up 0.3 mph at the same power level after ditching the old V-handlebar in favor of my current "gunner bars" setup. I really wish I had something better than this to go on, but it will have to do for now. When I get the M1 back and I'm still seeing 26.4 mph at 191 watts after several more tests, then I'll know it had to be the handlebar change that made the difference. Should that turn out to be the case, I may duplicate that setup on my M5.

 

[ed72]

I don't doubt hand position has a significant effect and sounds like you found a keeper although time will tell. I was surprised at some of my discoveries with hand position, too. I would like to experiment with gunners but solving a newly developed speed wobble is taking my feeble brain power at the moment. Anyway. It is a lot of little things that add up. Some of the improvements are specific to your body and your bike.

 

[Osiris]

23.6 mph on 199 watts is around 0.220-0.225. Unfortunately, I don't have a V20. It seems there would be room for improvement but I don't know where to look.

I took the M5 out for a test run this morning. On a three mile test segment I averaged 25.9 mph on 239 watts. How does that sound in terms of efficiency?

Easy improvements would be to replace the Gatorskins with a set of GP5000's, and remove the headlight and mirror. I'm really tempted to test the skin suit, but then I'd have to ride late at night so that no one could see me in it.

 

[Osiris]

I'm just looking over my data from this morning's test ride on board the M5. One very interesting thing I noticed was that an average power output of ~240 watts on the M5 feels like ~190 watts on the M1. Why is it just as tiring to produce 50 watts less on the M1? Who knows, but apparently there's still a price to be paid for putting out more power even when perceived effort is the same. When I stopped pedaling on the M1, I felt fine. By contrast, the test runs I did on the M5 left me completely exhausted. My heart was pounding, I was dizzy, and I felt completely drained of energy. Curiously I didn't notice these things at all when riding; only after I stopped and dismounted.

 

[ed72]

I took the M5 out for a test run this morning. On a three mile test segment I averaged 25.9 mph on 239 watts. How does that sound in terms of efficiency?

Easy improvements would be to replace the Gatorskins with a set of GP5000's, and remove the headlight and mirror. I'm really tempted to test the skin suit, but then I'd have to ride late at night so that no one could see me in it.

Sounds reasonable. Multiple trials and also comparing helps give confidence. Lots of variability.

How's this for efficiency. 377.9 miles in 22 hours moving time burning only 5100 calories, I don't believe the online calculators no matter how sophisticated when it comes to calories. Comes out to 14 calorie per mile. I ain't never goin lose no weight at this pace.

 

[Osiris]

Sounds reasonable. Multiple trials and also comparing helps give confidence. Lots of variability.

How's this for efficiency. 377.9 miles in 22 hours moving time burning only 5100 calories, I don't believe the online calculators no matter how sophisticated when it comes to calories. Comes out to 14 calorie per mile. I ain't never goin lose no weight at this pace.

I can't even imagine riding for 22 hours. I once read that a single peanut contains enough energy to run a mile on, so perhaps dieting is the only practical way to lose weight.