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The importance of good aerodynamics on a bicycle

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The importance of good aerodynamics on a bicycle

Old 01-21-11, 02:59 AM
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sunnyday
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The importance of good aerodynamics on a bicycle

Ive been reading about this subject for a few days . I have noticed that many ebikers on youtube do not seem to worry about their ebike being aerodynamic . Things like your upper body, square batterys , bike bags, etc have a significant bearing on slowing down your bike and making you and your motor/battery work harder.

Supposedly when doing 11 mph or less on a bicycle { flat land** front wind resistance isnt a large factor...but once you go above 11 mph, it becomes a noticeable factor. One article I read claimed that around 18 -20 mph on a bicycle , 80% of the energy used to maintain that speed , is being used up to overcome the wind resistance that hits the bike and the upper torso of the bicyclist . If these numbers have any truth to them , then we can see how important it can be to have a setup that allows the front wind resistance to be lessened as much as possible. Imagine going 20 mph on your ebike , and soley using the motor to maintain that speed , but also having your bike setup in a aerodynamically favorable way so you only need 20 -30 % energy to maintain 20 mph , compared to a non aerodynamic bike that would use 100% to maintain that speed.

I ordered a wattmeter for my bike and will soon be fabricating a V shaped front windshield from clear lightweight plexiglass which will provide a fantastic pointed shape to cut thru the front wind resistance , instead of that wind hitting my flat upper body head on and constantly slowing me down.

I will test the results with and without the front windshield using the wattemeter to get a good idea on how much aerodynamics help.

the windshield will be relatively lightweight , at under 5 lbs and it will mount to the front forks and steeering stem so it is always pointed in the direction of my turns/travel.

If the info I have read about aerodynamics is correct, this windshield should make a noticeable positive difference in allowing less energy to be used up to achieve certain speeds / distances.
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Old 01-21-11, 03:11 AM
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also, there will be a 6 " - 12 " space between the inside of the windshield and my front handlebars...this space will allow me to have a lightweight aluminum rack mounted there , so a bicycle carry bag can be situated there to haul odds and ends . This means the carry bag will also be shiedled from the front wind resistance......instead of having a carry bag mounted in a position on the bike in which it just decreases aerodynamics even more...

a square battery/s , carry bags, water bottles , your upper torso , bike racks, etc all add extra resistance to the front winds , decreasing motor and battery effieciency and making it more difficult to peddle the bicycle. If these accessories are gonna be used, then I think it would help greatly to mount them in a aerodynamic way.

We usually are looking for ways to increase our distances/ speeds and battery/ motor efficencys thru less weight, or regenerative methods ,etc....BUT....having a aeorydynamic setup on your bicycle may be the best way to increase efficiency by 20 % or more. Imagine being able to get 36 miles distance covered instead of 30 miles...all just by having a front windshield desgined to cut thru the headwind resistance. Such results are better then regen can offer.
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Old 01-21-11, 08:08 AM
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https://www.youtube.com/watch?v=lmkLr...eature=related

Last edited by sunnyday; 01-22-11 at 01:59 AM. Reason: To satisfy moderator desires.
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Old 01-21-11, 12:42 PM
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Originally Posted by sunnyday View Post
Ive been reading about this subject for a few days . I have noticed that many ebikers on youtube do not seem to worry about their ebike being aerodynamic . Things like your upper body, square batterys , bike bags, etc have a significant bearing on slowing down your bike and making you and your motor/battery work harder.
The "problem" can be solved with bigger/better motors and batteries. That's certainly a lot easier than with a standard bike, where the equivalent solution would be lots of training and practice to build yourself up.

But seriously, if the purpose of your trip is to carry luggage -- your luggage isn't a problem, it's the reason. Sure, you could make it more aerodynamic, but do you care enough? For an electric bike, just twist that control a little harder -- you don't even have to pedal harder.

Square batteries aren't likely to make a big impact on your speed/efficiency. The difference is more than zero, granted, but it's likely pretty damn small. Your riding position is likely to have a much larger impact, as would any panniers or other big things sticking out. Unless you're racing, there's better things to work on (and if you're racing, there's other things to work on first before you make a fairing for your batteries.)
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Old 01-21-11, 03:05 PM
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I think that's where the recumbent bikes come in handy.
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Old 01-21-11, 04:10 PM
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The guy in the youtube video built that from scratch and didn't just install a kit wheel and lash batteries to a rack.
I'm not going to hold it against him that he does not have fairings that were hand laid on C&C molds to wrap custom manufactured parts.
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Old 01-21-11, 04:31 PM
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Originally Posted by AllenG View Post
The guy in the youtube video built that from scratch and didn't just install a kit wheel and lash batteries to a rack.
I'm not going to hold it against him that he does not have fairings that were hand laid on C&C molds to wrap custom manufactured parts.

I dont recall saying anything about " holding it against him"

this isnt about criticizing a person for their choices, it is about the benefits of thinking in a aerodynamic fashion when it comes to bicycling in general.

I did not make any negative claims against the person in the video, I just commented on the lack of aerodynamics of his bicycle.
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Old 01-21-11, 04:33 PM
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Originally Posted by edcastrovalley View Post
I think that's where the recumbent bikes come in handy.

agreed..but they are often much more expensive then our upright 2 wheel counterparts.

recumbents seem to be ahead of the field when it comes to aerodynamic styling ...im just trying to apply that thinking to upright 2 wheeled bikes.
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Old 01-21-11, 04:35 PM
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Originally Posted by sunnyday View Post
this looks like a aerodynamic NIGHTMARE....the only thing that would make it worse is if he had a bicycle trailer hooked to the back that was square and wide . LOL

https://www.youtube.com/watch?v=lmkLr...eature=related
^^^
That didn't come across as high praise of his work.
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Old 01-21-11, 04:36 PM
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Originally Posted by AllenG View Post
^^^
That didn't come across as high praise of his work.

but it wasnt a comment on HIM personally..

just the bike..

correct ?
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Old 01-21-11, 04:37 PM
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I did not say : " this guy is a moron for making a non aerodynamic bicycle"

right ?

my comments are geared toward the vehicle and its lack of aerodynamics.
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Old 01-21-11, 04:44 PM
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Originally Posted by dougmc View Post
The "problem" can be solved with bigger/better motors and batteries. That's certainly a lot easier than with a standard bike, where the equivalent solution would be lots of training and practice to build yourself up.

But seriously, if the purpose of your trip is to carry luggage -- your luggage isn't a problem, it's the reason. Sure, you could make it more aerodynamic, but do you care enough? For an electric bike, just twist that control a little harder -- you don't even have to pedal harder.

Square batteries aren't likely to make a big impact on your speed/efficiency. The difference is more than zero, granted, but it's likely pretty damn small. Your riding position is likely to have a much larger impact, as would any panniers or other big things sticking out. Unless you're racing, there's better things to work on (and if you're racing, there's other things to work on first before you make a fairing for your batteries.)

My purpose is to experiment and see the benefits of having a aerodynamic windshield that blocks the air from hitting my chest/ arms/ head/shoulders ,etc...and then compare that to no windshield...

If it proves that I can gain only 10% extra distance , it will be worth it to me . Thats a extra mile for every 10 miles traveled , all just for putting on a windshield.
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Old 01-21-11, 07:12 PM
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Lets try this another way. The pointy windshield isn't going to help, much or any. Reduce your frontal area with narrow and dropped bars, and then build a fairing for behind your body. Google Oscar Egg bicycle....

In human speak: You are a scoop of ice cream, the fairing is a pointy ice cream cone, the cone should be BEHIND the scoop of ice cream if you want to improve aerodynamics

In engineer speak: boundry layer separation should be avoided by avoiding abrupt decreases in cross sectional area behind the largest section
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Old 01-21-11, 07:18 PM
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Originally Posted by merlin55 View Post
Lets try this another way. The pointy windshield isn't going to help, much or any. Reduce your frontal area with narrow and dropped bars, and then build a fairing for behind your body. Google Oscar Egg bicycle....

In human speak: You are a scoop of ice cream, the fairing is a pointy ice cream cone, the cone should be BEHIND the scoop of ice cream if you want to improve aerodynamics

In engineer speak: boundry layer separation should be avoided by avoiding abrupt decreases in cross sectional area behind the largest section

Really ?

you dont think there will be a noticeable reduction in air resistiance at 20 mph , if I put on a smooth , plexiglass pointed lightweight windshield that causes the wind to go around my upper body at the waistline and above, compared to that same wind hitting my face, and flat 26 " upper torso/chest area ?

wow...
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Old 01-21-11, 07:23 PM
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Originally Posted by sunnyday View Post
Really ?

you dont think there will be a noticeable reduction in air resistiance at 20 mph , if I put on a smooth , plexiglass pointed lightweight windshield that causes the wind to go around my upper body at the waistline and above, compared to that same wind hitting my face, and flat 26 " upper torso/chest area ?

wow...

If there was a steady 20 mph wind outside, and I stood in that wind , facing the wind directly with my body , surely I would feel it MUCH more then if I stood there with a smooth pointed windshield to make the wind go around my body..correct ?

I have a hybrid bicycle, so bending over while cycling is not a option for me...the bike isnt conducive for that style of cycling.
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Old 01-21-11, 07:37 PM
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[QUOTE=merlin55;12112271].

In human speak: You are a scoop of ice cream, the fairing is a pointy ice cream cone, the cone should be BEHIND the scoop of ice cream if you want to improve aerodynamics

/QUOTE]

so having the point of the ice cream cone in back of me, instead of having the point of the ice cream cone in front of me is more aerodynamic ?
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Old 01-21-11, 07:56 PM
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Originally Posted by sunnyday View Post
Really ?

you dont think there will be a noticeable reduction in air resistiance at 20 mph , if I put on a smooth , plexiglass pointed lightweight windshield that causes the wind to go around my upper body at the waistline and above, compared to that same wind hitting my face, and flat 26 " upper torso/chest area ?

wow...
Correct. Build a fairing that is behind your back, like Oscar Egg from a 100 years ago or so. Wind drag is equal to the speed cubed times the frontal area times the drag or shape factor. Your windshield will likely increase the frontal area, but not improve the shape factor. Think of a teardrop shape, the shape is produced by the wind forcing the water in to a shape with the lowest drag, blunt on the front...point at the back. The fairing behind you will improve the shape factor.
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Old 01-21-11, 08:32 PM
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Originally Posted by sunnyday View Post
..... I have noticed that many ebikers on youtube do not seem to worry about their ebike being aerodynamic .....
What if I was to suggest that many bicycle enthusiasts on youtube do not seem to worry about their bike being aerodynamic?

Alot of motorcycle enthusiasts dont worry about it, yet others insist on it.

Would that put this issue into another light?
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Old 01-21-11, 09:06 PM
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Originally Posted by sunnyday View Post
so having the point of the ice cream cone in back of me, instead of having the point of the ice cream cone in front of me is more aerodynamic ?
Probably, but in the absence of actual testing it's hard to predict given that the results depend on how smooth you can make the transition between your body and the tailcone. I'd note that commercial fairings like those from Zzipper are placed in front but have a very rounded shape like the rounded ice cream scoop rather than a pointy cone. They do claim to improve aerodynamics, but part of the goal is improved comfort by deflecting some of the wind (and rain/snow if present) from the rider.

If you really want better aerodynamics then the body sock approach used on some recumbents would seem to be a better bet - rounded fairing in front, a smooth body sock covering the middle portion incl. the rider, and connecting to a tailcone at the back.
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Old 01-21-11, 10:58 PM
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Originally Posted by sunnyday View Post
I did not say : " this guy is a moron for making a non aerodynamic bicycle"

right ?

my comments are geared toward the vehicle and its lack of aerodynamics.
No, you called it a NIGHTMARE (sic) and laughed.
Pick a better example than a proof of concept experiment it you want to complain about aerodynamics.
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Old 01-22-11, 01:50 AM
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Originally Posted by AllenG View Post
No, you called it a NIGHTMARE (sic) and laughed.
Pick a better example than a proof of concept experiment it you want to complain about aerodynamics.
exactly...I called it a nightmare...I did not comment on the person itself.

" it" is not a person.." it" is a thing...

Im trying to figure out why you insist on insinuating I was trying to attack a person when my comments were about a " bicycle and its lack of aerodynamics" .

Oh well, you are a moderator , so I guess its best for me to just let you win the argument.
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Old 01-22-11, 01:55 AM
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Originally Posted by prathmann View Post
Probably, but in the absence of actual testing it's hard to predict given that the results depend on how smooth you can make the transition between your body and the tailcone. I'd note that commercial fairings like those from Zzipper are placed in front but have a very rounded shape like the rounded ice cream scoop rather than a pointy cone. They do claim to improve aerodynamics, but part of the goal is improved comfort by deflecting some of the wind (and rain/snow if present) from the rider.

If you really want better aerodynamics then the body sock approach used on some recumbents would seem to be a better bet - rounded fairing in front, a smooth body sock covering the middle portion incl. the rider, and connecting to a tailcone at the back.

yeah, its mostly a experiment for me at this point in time....but from the articles I have read, if one achieves better aerodynamics , it makes a noticeable difference in efficiencys....I have read charts that actually breaks down the efficiencys gained by having :

shaved legs, tight lycra short pants , no water bottles , streamlined helmuts, streamlined windshields, etc....

The good thing is, I will be able to use my wattmeter to see if I gain efficiencys with my experiment.

Last edited by sunnyday; 01-22-11 at 02:00 AM.
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Old 01-22-11, 02:00 AM
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I went back and edited my post , the one that seems to have upset the moderator so much.
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Old 01-22-11, 03:11 AM
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Just so you know I won't moderate a thread if I'm part of the discussion.

Anyhow, my point was that pointing out the lousy aerodynamics of that bike is kinda like pointing out the poor off road capability of a Ferrari. It's something that was never considered.

A diamond frame bike's basic design (the fact that the rider is basically standing upright) is poor from the start aerodynamically.
If you really want to improve aerodynamics then decrease your frontal area. The most effective thing you can do with a diamond frame is use drop bars. Fairings and windshields are going to add weight, hinder your movements, and will be detrimental to your stability in a side wind. You may be slippery in a straight line by the overall performance of the bike is going to suffer somewhat badly.

Rather than adding complexity and weight to your bike I think you would be much better served by a set of drops or tri bars.

Last edited by Allen; 01-22-11 at 03:26 AM.
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Old 01-22-11, 08:05 AM
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Take a look at the helmets that the bicycle pro's use. They are much like what prathmann suggests. The idea is to decrease drag. The reason the icecream cone analogy works is that the drag comes from the air trying to refill the area behind you. The abrupt change in direction of the air takes energy. By tapering the backside the air flows around you.(laminar flow).
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