Aerodynamics

[WASYLBRYTAN]

Thats interesting. Do you have any pictures of your setup? I'm real interested in trying this out.

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

 

[WASYLBRYTAN]

Comparison tests need to keep variables the same. if you change motors or power settings, I would not include those results. Just because you use a higher power motor does NOT mean you are using more power. It's all about the load at speed. You need a Cycle Analyst or watt meter in order to do any real energy consumption testing IMO.

You have a very valid point. When I first got this motor I ran it with and without the fairings, exchanging them dozens of times and I left the fairings on because their performance was superior. It is not very scientific but the fairings "feel" so good that I don't want to take them off.

And, for what it's worth, the load, speed, bike, conditions, route, weather with the new motor were identical in every way to conditions with the old motor. Bill

 

[mrbill]

Just curious how many of you have put any effort into aerodynamics with your setup and what were your results?

I posted my build recently here:
http://endless-sphere.com/forums/viewtopic.php?f=6&t=60307

And didn't see much traffic on the thread.

Here's a photo showing a friend of mine modeling a faired and socked Power Gold Rush (Easy Racers):
http://mrbill.homeip.net/albums/zach_rides_hybrid_gold_rush.2010.12.04/pages/page_8.html

The rider's head sits above the top of the front fairing allowing a view forward. This custom e-bike version of the Gold Rush is similar to what one can buy stock from Easy Racers today for about $5-6k.
http://mrbill.homeip.net/albums/seattle_to_portland.2000.07.08/pages/page_3.html
http://easyracers.com/bicycles.html

And, here I am riding my Power Pursuit (Rotator) at PIR several years ago:
http://mrbill.homeip.net/albums/epower_challenge.2010.05.31/pages/page_40.html

Both of these bikes have open bottoms for ease of riding. Closing the bottom would be the next step to improve aerodynamics if I didn't mind giving up the convenience of being able to put my feet down easily.

I've ridden my Power Pursuit with and without the front wheel fairing (top 1/3 of wheel), and I see no noticeable decrease in aero drag.

Here are a couple of photos showing the front wheel fairing:
http://mrbill.homeip.net/albums/powerPursuitBuild/single-image/20140412-DSC05061-photo.html#anchor
http://mrbill.homeip.net/albums/powerPursuitBuild/single-image/20061203-powerPursuitBuild26-photo.html#anchor

I plan to discontinue use of the front wheel fairing because it prevents me from using a headlamp or video camera. Perhaps with larger wheels it makes more difference, but I have a hard time believing it would make more than about 5% difference unless my bike were more streamlined. And, certainly there are bigger fish to fry (aerodynamically-speaking) on typical city bike or MTB with knobbies.

 

[WASYLBRYTAN]

I continue to see at least a 20% improvement in battery range everytime I test this. Bill

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

 

[veloman]

I continue to see at least a 20% improvement in battery range everytime I test this. Bill

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

What are your speeds? Terrain, stops, wind? How much do you pedal?

 

[Chalo]

I continue to see at least a 20% improvement in battery range everytime I test this. Bill

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

You know, I think it's the ayahuasca talking.

 

[WASYLBRYTAN]

I continue to see at least a 20% improvement in battery range everytime I test this. Bill

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

What are your speeds? Terrain, stops, wind? How much do you pedal?

Everything is the same as it was before I installed the fairings; that is why I notice improvement with such certainty. I ride the same route 2 or 3 times each day at the same times, speeds, terrain, weather conditions. I know the route so well that I can even detect different bumps in the road. Do you think I let those ugly things mess up my beautiful bike for nothing? It costs nearly nothing for anyone to try them; it's not as if I am trying to sell something. Bill

 

[WASYLBRYTAN]

I continue to see at least a 20% improvement in battery range everytime I test this. Bill

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

You know, I think it's the ayahuasca talking.

Ayahuasca is a hallucinogenic drug. This sort of person thinks a new discovery is the result of drugs. I PITY THE FOOL

 

[Modbikemax]

I continue to see at least a 20% improvement in battery range everytime I test this. Bill

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

Null winds is a startup company trying to commercialise this idea.
See
http://www.gizmag.com/null-winds-upper-wheel-fairings/31781/pictures

I think it has merit. I noticed a 3~5 km/h improvement on a non ebike when I went to aero spoked deep vee wheels.
A new set of Mavic aero spoke wheels looks cooler than duct tape and cardboard too. :wink:
Try ditching the fat tyres too.

 

[WASYLBRYTAN]

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/10329744_649790328447932_1839114540391792081_o.jpg

See
http://www.gizmag.com/null-winds-upper-wheel-fairings/31781/pictures

I think it has merit. I noticed a 3~5 km/h improvement on a non ebike when I went to aero spoked deep vee wheels.
A new set of Mavic aero spoke wheels looks cooler than duct tape and cardboard too. :wink:
Try ditching the fat tyres too.

Whenever I look at the cost of aero wheels the appearance of my duct tape improves. My 1.75 Schwalbe Marathons are E-Bike rated and I wouldn't give them up for anything. I have ridden 16,000 miles on them in a year and a half and they still have lots of tread left. I think they might have a chance to make it the equivalent of around the world at 25,000 miles. I am regularly getting more than 100 miles (160 km) from an 8.8 amp hour battery so I must be doing something right. And it is sheet aluminum, not cardboard. The whole point to what I am doing is almost zero cost. Bill

 

[Modbikemax]

Hats off for doing the test and getting the results Bill.
I try to keep costs realistic too but as any cyclist knows it's all in the wheels if you want performance.
That's why they don't run fat tires in the Tour.
It is interesting you are on the same track as Null winds. I wonder if we will see a commercial product along these lines soon.
There is quite a bit of discussion in the cycling community about fairings and streamlining but the bike manufacturers are falling in line with racing regulations which don't allow fairings. That's why we see lots of $300 streamlined handlebars but no plastic fairings.
I ride into a head wind most days and I would love to be able to buy a functional fairing developed by years of race proven technology. But alas sheet Ali and duct tape seems to be cutting edge at the moment.

 

[Tommy L]

[youtube]rYdnkaAhVtI[/youtube]

The 12 degree as it leaves you is the most important aspect

It is amazing and heading into a very strong wind is like to wind isn't there!

Tommy L sends....

 

[WASYLBRYTAN]

Hats off for doing the test and getting the results Bill.
I try to keep costs realistic too but as any cyclist knows it's all in the wheels if you want performance.
That's why they don't run fat tires in the Tour.
It is interesting you are on the same track as Null winds. I wonder if we will see a commercial product along these lines soon.
There is quite a bit of discussion in the cycling community about fairings and streamlining but the bike manufacturers are falling in line with racing regulations which don't allow fairings. That's why we see lots of $300 streamlined handlebars but no plastic fairings.
I ride into a head wind most days and I would love to be able to buy a functional fairing developed by years of race proven technology. But alas sheet Ali and duct tape seems to be cutting edge at the moment.

This all started for me when I wanted to improve the aerodynamics of my bike with minimal discomfort. Aero bars were my first choice but they involved an uncomfortable/hard to control position . I found the null winds site and tried my own version of it because it was the simplest looking device I found anywhere. Although the wheels only give 10% of a bike's drag, the improvements I experienced are way more. I think that in this case, the whole is greater than the sum of its parts. Because it works so well and costs almost nothing, I want as many as possible to try it. If all our results are consistent we may have the holy grail of e-bike aerodynamics. Three days ago I obtained 217 kilometres range from an 8.8 amp hour battery. The tires I have give me such good results I will not change them. 1.75" with 70 PSI is not exactly a fat tire.
I am waiting for a meeting with the owner of the company which makes my bike so I can discuss building aerodynamic-skirted fenders at the factory level where cost is minimal. This is why I want testimony from more than one user about their effectiveness.

Racing regulations are idiotic and of no concern to me. Racing regulations are responsible for failure to recognize the bicycle as a legitimate transportation device because egotistical racer wannabees attract all the attention. We might all be much better off if bicycle racing did not exist. If manufacturers find a cheap and easy way to increase e-bike range they will sell more to real people. Bill

 

[veloman]

You should state voltage, not just ah. Ah alone means very little.

Manufacturers will only sell products that the public wants. The vast majority of people have a very clear idea of what they want their bike or ebike to look like. The best selling ebikes look as much like bicycles as possible (E-motion).

In USA, appearance is the most important. Consumers rate looks above function almost always from what I've seen.

Until the racers start using fairings, the public won't latch on. Everything follows the racers. Just like with motorcycles. The racing motorcycle industry did away with real fairings and now we have motorcycles that require the same power to go highway speeds as a modern car (because they are so non-aero).

But I agree with you. I want to see aero ebikes that get 30% more range. Keep doing what you're doing, just know what you're up against. I still need to build my own wheel fairings.

 

[Modbikemax]

The fairing on a race motorbike is more about handling and keeping the front wheel on the ground. Power is not an issue for them but handling is. The days of the most powerful are over it's all about handling and the rider now days.

I must say Bill I am a little sceptical about your performance figures on the bike pictured. I have clocked up a few k's now and I can only assume you are going very slow with lots of pedalling or your speedo is not set for the correct wheel size.
As veloman suggests a bit more information might be useful. If you are onto something it's worth sharing the data.

 

[WASYLBRYTAN]

36 volts, 8.8 amp hours. 217 kilometres at 18 kph. I am skeptical of my own figures. That is why I want more people to try them. Bill

 

[DrkAngel]

36 volts, 8.8 amp hours. 217 kilometres at 18 kph. I am skeptical of my own figures. That is why I want more people to try them. Bill

At 18 kph, (= 11.18 mph), wind resistance is a nearly null factor! 10% of 30 kph, (= 18.46 mph), and 3% of 50 kph (31mph).
Any meaningful results should require an otherwise identical configuration at carefully monitored, and much higher, speeds.
At 18kph, a 5 psi tire pressure differential might have better results!

I, and likely most, thought you might be talking about 30-50kph+ (18-31mph+) ... where wind resistance becomes a major factor.
Most sources rate that wind resistance does not become a major factor till near 20mph (30kph+)

 

[Modbikemax]

36 volts, 8.8 amp hours. 217 kilometres at 18 kph. I am skeptical of my own figures. That is why I want more people to try them. Bill

At 18kph I am not surprised you got those figures. I would barely need to pedal on my non ebike at that speed.
Given an inverse square law for drag you would find your figures plummet at a more realistic speed of 25 to 30kph.
Certainly going slow is the first and easiest way to reduce drag.

The challenge comes when you want to go fast and reduce drag.

At 18kph it would be very difficult to say your streamlining was having any affect at all since other variables would be having a much larger affect in proportion to wind drag. With skinny high pressure tires you might get another 30km.

 

[WASYLBRYTAN]

I cannot express how disappointed and frustrated I am with this forum. I discover something interesting and tell people about it so that they can try it and give me their feedback. But all people want to do is discredit me as if I am trying to cheat them or get money out of them. I GIVE UP

 

[Modbikemax]

I cannot express how disappointed and frustrated I am with this forum. I discover something interesting and tell people about it so that they can try it and give me their feedback. But all people want to do is discredit me as if I am trying to cheat them or get money out of them. I GIVE UP

Thats a bit immature. I did say you were onto something but some broader testing is required. Try doing the test at higher speeds and get more data.
The worst thing that could happen is you will learn something.

 

[tahustvedt]

Good 60 mm profile wheels on a road bike reduce the power required to ride at 40 km/h by about 10 W compared to conventional wheels with low profile rims and round spokes. At 20 km/h I estimate the aero benefit would be more like 2 W. A lot of wind tunnel comparison tests have been done and can be found online by searching.

I'm a bit surprised that more people don't use recumbent bikes. A good, suspended recumbent will probably be almost as efficient as a time trial bike as far as aerodynamics go.

 

[teklektik]

I cannot express how disappointed and frustrated I am with this forum. I discover something interesting and tell people about it so that they can try it and give me their feedback. But all people want to do is discredit me as if I am trying to cheat them or get money out of them.

Seriously, dude -try what and why?

There are two entirely different concepts here:

• The Nullwinds 'headwind-negating' fairings
• WASYLBRYTAN's 'range-improving' fenders

• Nullwinds is very clear:
  
  In still air, the Nullwinds fairing has been tested to give no significant improvement.
  
  Of particular note (see Nullwinds Drag Mechanics Document):

  1. Under null headwind conditions, the predicted gains are minimal, which is consistent with road test results.

     Importantly, both their new drag formulae and their road tests are consistent on this point.
     
     
  2. The Nullwinds maximum estimated potential speed improvement of 16% using their unreleased computational model are for a 10mph bike in a continuous 40mph headwind and only where the spoke drag is a large percentage of the overall vehicle drag.
     
     These Nullwinds estimates are unsubstantiated by testing - the largest recorded savings by actual test were "in excess of 10%".
  In any case, large heavy riders with upright posture on heavy ebikes using fat 26" ebike tires certainly fall in the category of bikes with low spoke-drag-to-vehicle-drag ratios. Nullwinds observes that such vehicles will show substantially reduced improvement.
  
  Nullwind's claims of improvement may mislead those who believe that the power required to propel a bike at 10 mph in a 10mph headwind is the same as that required to propel the bike at 20mph in still air. However, this is certainly not the case and simply traveling at higher speed without headwind will not make the fairings work - and Nullwinds states this clearly.
  
  
• You claim a repeatable 20% range improvement with your DIY fairings in essentially uninstrumented tests:
  

  I continue to see at least a 20% improvement in battery range everytime I test this.
  ...
  I ride the same route 2 or 3 times each day at the same times, speeds, terrain, weather conditions.
  ...
  Three days ago I obtained 217 kilometres range from an 8.8 amp hour battery.
  ...
  36 volts, 8.8 amp hours. 217 kilometres at 18 kph.

  So - on a heavy draggy ebike in presumably still air (or certainly not continuos high speed headwinds day after day of your tripping) you are claiming 200% of the best test gains claimed by Nullwinds. Confusingly, your vehicle and riding conditions are flatly stated by Nullwinds to reduce or eliminate any gains by their technology.
  
  • Looking at the figures you have supplied we see that you go 217km on 36v with an 8.8 Ah pack yielding an energy consuption of:
    217km / (36v x 8.8Ah) = 1.46 Wh/km travelling at 18kph (2.35wh/mi at 11mph).
    
    With a little math we know that a 60lb hybrid bike with 170 rider requires 7.6Wh/mi to achieve 11mph in still air.
  So - you are puttering along at 11mph and are providing 69% of the power by pedaling. Your 'tests' are based on results that rely on unmeasurable and subjective rider pedal power input that is 222% of the applied motor power - hardly a compelling test scenario to claim a 20% increase in ebike range.

Returning to the question of 'what to test and why?':

1. By their own statements, Nullwinds appears to offer insignificant improvements for the ebike world - wrong style bike, wrong speed, and wrong headwind requirements.
2. You offer claims that contradict the testing and physics presented by Nullwinds and substantiate them only with vague and subjective tests that rely on 69% of the vehicle power from the rider at speeds that are generally considered undesirably/unrealisticy slow.

Nothing to test in either case.

 

[kudos]

I recently did a range test on my 10T Mac running new 12S Lipo 50V 8Ah with 30A controller.

I was doing no effort pedaling the whole way and got 19 miles.

Now I know we aren't comparing apples with apples here, your battery is 0.8 Ah bigger, you are using a low powered mid drive where as I'm using a relatively high powered geared hub and I was averaging 14 mph where as you were doing 11.

However, despite the different setup you are claiming 135 miles!

This is over six times the range of my setup on similar size battery, which you must admit sounds difficult to believe.

Saying that, I have a bike I can use and I may well give this a go out of curiosity.

Kudos

 

[teklektik]

Good 60 mm profile wheels on a road bike reduce the power required to ride at 40 km/h by about 10 W compared to conventional wheels with low profile rims and round spokes. At 20 km/h I estimate the aero benefit would be more like 2 W. A lot of wind tunnel comparison tests have been done and can be found online by searching.

Interestingly, Nullwinds specifically makes note that aero wheels impair the effectiveness of their fairing because the wheels lower the spoke-to-vehicle drag ratio. Mixing the two does not give an additive advantage...

 

[tahustvedt]

Found a page with collected data. Some of the links are manufacturer tests though (The Giant Propel test, for example) so not necessarilly impartial, thought not necessarilly wrong either. http://www.aeroweenie.com/data.html

My road bike is a Cervelo S5 with 58mm rims. It's fast.