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Re: Aerodynamics thread?

Posted: Jun 15 2008 12:24pm
by recumpence
Your bike is actually pretty high for a recumbent (at least your head is high for good visibility). My head is just about 30 inches off the ground. It is tough to see dips in teh road and I have no suspension. So, I scout any new roads with my car before I ride them unless I am planning on rising relatively slow. :mrgreen:

Matt

I have been staring at this for a few months now...

Posted: Jun 29 2008 10:15am
by Lenk42602
I am waffling, really. The intent is to increase range, not speed ( although I am sure a few mph increase would result). But there seems to me to be a point of no return in everyone's projects. For some reason, installing a mini bike 1/2 fairing on my 74v Stealth Electric Bicycle seems to me to be that point........

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...because obviously I could source the lower 1/2 of the fairing and install it also. Concerned that it will fully depart from the stealth bicyce realm and clearly enter motorcycle land in the eyes of the uninitiated, and most importantly the law.

Now, if anyone can provide any real data, or directions on how to calculate, or help me to quantify exactly to what degree a 1/2 (or full) fairing on my setup will increase effeciency, I can begin weighing the exposure risk versus the performance benefit.....

Re: Aerodynamics thread?

Posted: Jun 30 2008 1:40am
by Pete
Len, have you checked out http://www.ihpva.org ? The site is a bit of a mess to navigate, but there is a lot of info burried there. HPV's are also all about efficency.

For info, I ride a recumbent trike. 40 mph with your head less then 3 feet of the pavement feels awful quick and has a huge grin factor :D . I looked into a fairing for the trike recently and talking witht he manufacturer - Greenspeed, they suggested that on a trike there is not a huge aerodynamic improvement. But it would be good to help keep the weather off.

Re: Aerodynamics thread?

Posted: Jun 30 2008 9:17am
by Lenk42602
Just checked it out - have to go back and read a little more... Thanks for the link!

peace,

len

Re: I have been staring at this for a few months now...

Posted: Jun 30 2008 12:00pm
by JennyB
Lenk42602 wrote: Now, if anyone can provide any real data, or directions on how to calculate, or help me to quantify exactly to what degree a 1/2 (or full) fairing on my setup will increase effeciency, I can begin weighing the exposure risk versus the performance benefit.....
I have no personal experience, but from what I remember of the reviews, a Zipper fairing on a drop-bar bike was about as effective as an aerobar. The main advantage was in comfort: you don't have to crouch so low, and it keeps the wind and rain off your thighs. That m/c fairing with flat bars would be less effective - I would estimate it to be much the same as riding 'on the hoods'.

The classic road bike position helps a great deal if you can adapt to it, if you have a meter you can quickly work out your own best compromise between comfort and range. The full aero, on-the-elbows position is in fact the most cemfortable, but not recommended where you may keed to change direction quickly.

Re: Aerodynamics thread?

Posted: Jun 30 2008 12:44pm
by John in CR
It doesn't seem like an aerodynamic fairing it terribly difficult. The thing we need to come up with is a design on the back side that addresses the acoustical problem with fairings, and that is, the better the fairing, the greater the concentration and focusing of road noise directly at the rider. I'd love to do a fairing, but I'd rather carry more batteries than become the focal point of amplified tire noise.

Re: Aerodynamics thread?

Posted: Jun 30 2008 4:48pm
by monster
i thought this was a good effort. i didn't notice any difference though.

Re: Aerodynamics thread?

Posted: Jun 30 2008 4:53pm
by Lenk42602
Monster,

Is that a zipper fairing? You said you didn't notice any difference? How fast where you traveling, and data, etc? I'm starting to think that while my little mini bike fairing looks cool, probably won't help much unless I sheild the entire front of the bike, and then add some tai of some sort....

Len

Re: Aerodynamics thread?

Posted: Jun 30 2008 6:19pm
by recumbent
John in CR wrote: The thing we need to come up with is a design on the back side that addresses the acoustical problem with fairings.
Truer words are seldom spoken.

I removed my full fairing for the hot summer months and my top speed dropped by...1- 2 kph.

The noise level dropped immensly to near nothing, quite refreshing, I'm going to keep it off till it gets cold out, that's where fairings really shine, they keep you warm & dry.

Re: Aerodynamics thread?

Posted: Jun 30 2008 6:50pm
by John in CR
recumbent wrote:
John in CR wrote: The thing we need to come up with is a design on the back side that addresses the acoustical problem with fairings.
Truer words are seldom spoken.
I removed my full fairing for the hot summer months and my top speed dropped by...1- 2 kph.
The noise level dropped immensly to near nothing, quite refreshing, I'm going to keep it off till it gets cold out, that's where fairings really shine, they keep you warm & dry.
I have a few ideas to test out once I get to a stage of fooling around with fairing, so maybe my previous hobby speakers and room acoustics will prove useful. I'm already making use lots of tidbits from the thermodynamics I picked up piddling around with hot air engines.

Re: Aerodynamics thread?

Posted: Jun 30 2008 8:50pm
by www.recumbents.com
If you have a recumbent bike, a tailbox is the best way to gain better aerodynamics. If you have a road bike, buy more batteries... 8)

Something like this Coroplast tailbox is cheap, easy to make and very lightweight.
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There are plans here:
http://www.recumbents.com/wisil/tailbox ... ailbox.htm

You can find ot more about aerodynamics here:
http://www.recumbents.com/wisil/whatsup.htm

-Warren.

Re: Aerodynamics thread?

Posted: Jul 01 2008 6:31am
by recumpence
Warren,

Welcome! Glad you found us.

I have some updates coming soon (new motor). :wink:

I am curious about your No-Com tail fairing. Should make that bike crazy fast.

Matt

Re: Aerodynamics thread?

Posted: Jul 01 2008 7:13am
by Miles
With upright bikes, maybe what we need are different ways of varying the riding position? Drops and other dual set-ups don't combine easily with throttles etc. (not a problem with a pedelec system, though...)

This kind of thing. Preferably something that can be adjusted on the move.

Re: Aerodynamics thread?

Posted: Jul 01 2008 4:27pm
by Mark_A_W
I just run a thumb throttle in parallel with my main throttle, fitted to the LH bar end. I sit up or get down on the bar ends, and still have a throttle.

Re: Aerodynamics thread?

Posted: Jul 03 2008 9:29am
by Miles
http://www.endless-sphere.com/forums/vi ... 38&start=2

Data from "Bicycling Science"; DG Wilson 3rd edition


Upright commuting bike... CD 1.15; Area 0.55sq.m

Touring bike... CD 1.0; Area 0.40 sq.m

Racing bike... CD 0.88; Area 0.36 sq.m

"Easy Racer" recumbent (unfaired)... CD 0.77; Area 0.77 sq.m

"Peer Gynt" recumbent (unfaired)... CD 0.74; Area 0.56 sq.m

"Peer Gynt" recumbent + front fairing... CD 0.75; Area 0.58 sq.m

"Flux" recumbent + rear fairing... CD 0.55; Area 0.35 sq.m

"M5" low racer recumbent (faired)... CD 0.13; Area 0.35 sq.m

"Avatar Bluebell" recumbent (faired)... CD 0.11; Area 0.42 sq.m

If anbody knows other sources of data, please let me know. I seem to remember some tables in "Human Power" - if I can find them, I'll post them here.

Re: Aerodynamics thread?

Posted: Jul 04 2008 4:05am
by JennyB
Miles wrote:http://www.endless-sphere.com/forums/vi ... 38&start=2

Data from "Bicycling Science"; DG Wilson 3rd edition


Upright commuting bike... CD 1.15; Area 0.55sq.m

Touring bike... CD 1.0; Area 0.40 sq.m

Racing bike... CD 0.88; Area 0.36 sq.m

"Easy Racer" recumbent (unfaired)... CD 0.77; Area 0.77 sq.m

"Peer Gynt" recumbent (unfaired)... CD 0.74; Area 0.56 sq.m
What matters is CD*Area:
Touring bike... CDA 0.4

Racing bike... CDA 0.32

"Easy Racer" recumbent (unfaired)... CDA 0.59

"Peer Gynt" recumbent (unfaired)... CDA 0.41
"Peer Gynt" recumbent + front fairing... CDA 0.44 (some mistake here?)

"Flux" recumbent + rear fairing... CDA 0.19

So, even a touring position will beat a semi-bent (bb lower than hips). This bears out my own experience that in aero tuck I can out-coast my brother's unfaired tadpole trike.

Re: Aerodynamics thread?

Posted: Jul 04 2008 4:39am
by Miles
JennyB wrote: "Peer Gynt" recumbent (unfaired)... CDA 0.41
"Peer Gynt" recumbent + front fairing... CDA 0.44 (some mistake here?)
I thought the anomaly was addressed in the text, but I can't find any reference to it. It's quite possible that a miss-matched front fairing could have a negative impact....

Re: Aerodynamics thread?

Posted: Jul 05 2008 10:01am
by monster
Lenk42602 wrote:Monster,

Is that a zipper fairing? You said you didn't notice any difference? How fast where you traveling, and data, etc? I'm starting to think that while my little mini bike fairing looks cool, probably won't help much unless I sheild the entire front of the bike, and then add some tai of some sort....

Len

i bought a baby bath tub from ebay then cut and bolted to my basket.

Re: Aerodynamics thread?

Posted: Jul 11 2008 11:34am
by TylerDurden
A post on ecomodder for an online simulator:

http://ecomodder.com/forum/showthread.p ... #post43066

Image

Re: Aerodynamics thread?

Posted: Jul 11 2008 2:00pm
by Drunkskunk
TD, looks like a great tool. have you plugged the CitiVan into it yet?

Re: Aerodynamics thread?

Posted: Jul 11 2008 2:10pm
by TylerDurden
Drunkskunk wrote:TD, looks like a great tool. have you plugged the CitiVan into it yet?
You can be sure I will, when it starts raining again... I just finished pulling the shredded tires & wheels to go and get new skins (maybe the tire-store has wifi).

Later, yall...

Re: Aerodynamics thread?

Posted: Jul 11 2008 3:55pm
by cerewa
How do you go up and down gutters/kerbs on all these recumbenty thingys?
The same way you go up and down gutters/curbs in a porsche - you don't.

I ride an upright bike but it has no suspension and I try to avoid taking bumps, up or down, of more than 1 inch (or 3 inches if i'm going really slowly). I ride in the road like I would on a motorcycle or car.

Re: Aerodynamics thread?

Posted: Jul 11 2008 6:12pm
by Mark_A_W
cerewa wrote:
How do you go up and down gutters/kerbs on all these recumbenty thingys?
The same way you go up and down gutters/curbs in a porsche - you don't.

I ride an upright bike but it has no suspension and I try to avoid taking bumps, up or down, of more than 1 inch (or 3 inches if i'm going really slowly). I ride in the road like I would on a motorcycle or car.
Then you may as well drive a car or ride a motorcycle.

Half the point of an e-bike being a pushbike is you can:

- ride on footpaths
- sneak around red lights
- ride on bike paths
- ride on the wrong side of the road
- ride through foot lanes, etc with barriers for vehicles
- bash over median strips at 30kmh to cross roads wherever you need
- closed roads
- footy ovals
- ANYWHERE

And it's pretty unlikely the cops will do you. The whole point of a bike is to AVOID the traffic, not mix with it.

My ride to work is 15km. My drive to work is 20km, because I can take SHORTCUTS.

If I was going to stick to the same legal route as my car, I'd get a Vectrix maxi scooter or something. A bicycle is about freedom. Without a robust bike (preferably dual suspension) you lose that freedom -the freedom to go where it's safest and quickest for you.

Re: Aerodynamics thread?

Posted: Jul 11 2008 8:40pm
by recumpence
Mark_A_W wrote:
cerewa wrote:
How do you go up and down gutters/kerbs on all these recumbenty thingys?
The same way you go up and down gutters/curbs in a porsche - you don't.

I ride an upright bike but it has no suspension and I try to avoid taking bumps, up or down, of more than 1 inch (or 3 inches if i'm going really slowly). I ride in the road like I would on a motorcycle or car.
Then you may as well drive a car or ride a motorcycle.

Half the point of an e-bike being a pushbike is you can:

- ride on footpaths
- sneak around red lights
- ride on bike paths
- ride on the wrong side of the road
- ride through foot lanes, etc with barriers for vehicles
- bash over median strips at 30kmh to cross roads wherever you need
- closed roads
- footy ovals
- ANYWHERE

And it's pretty unlikely the cops will do you. The whole point of a bike is to AVOID the traffic, not mix with it.

My ride to work is 15km. My drive to work is 20km, because I can take SHORTCUTS.

If I was going to stick to the same legal route as my car, I'd get a Vectrix maxi scooter or something. A bicycle is about freedom. Without a robust bike (preferably dual suspension) you lose that freedom -the freedom to go where it's safest and quickest for you.
I couldn't possibly disagree with you more. I used to ride freestyle in my teenage years. I also own a $3,500 radical freeride mountain bike. So, I enjoy hopping curbs and cutting through trails as much as the next guy. However, my E-bike is a recumbent. Until you ride a recembent, you will not appreciate their strengths. Also, for me, the point is accelleration and efficiency. I can't acheive both in a mountain bike. I can, however, with my recumbent.

Matt

Re: Aerodynamics thread?

Posted: Jul 11 2008 9:02pm
by TylerDurden
A cruzbike with a fairing and tailbox might be a good compromise.