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Re: Aerodynamics thread?

Posted: Aug 03 2008 9:24am
by StevenR
Here...

http://www.mueller-hp.com/windtunnel.htm

...is wind tunnel testing of Mueller fairings done by Mueller.

Basically says recumbant with fairing is no better than an aero tuck. For me, given the recum disadvantages, I will stick with an areo extension on flat bars. Now if I could just get the throttle and cruise control onto the old Scott AT-4's...

Re: Aerodynamics thread?

Posted: Aug 03 2008 11:36am
by recumpence
If that were the case, why are recumbents banned from upright bike racing classes?

What you have to look at with recumbents is, is it a low recumbent or a high recumbent? Is the seating upright or low?

The Vision recumbents he was testing are not lowracers. They are relatively upright seating style recumbents. I am sorry, but all this expensive wind tunnel testing can be easily avoided by using common sence. Look at the frontal area of the bike in question. If the frontal area is large, it will be slow. If the frontal area is small, it will be fast (generally speaking).

I am not trying to push anyone into a recumbent. Buy and ride whatever you enjoy most. But, I am tired of people giving this arguement.

A low recumbent that is setup well is faster than an upright bike, period. The world record is evidence of this and anyone who has ridden a lowracer knows it.

Again, ride whatever you enjoy. Heck, I have a couple uprights and a couple recumbents. Recumbents do have their drawbacks. But, don't kid yourself into thinking they are slower than an upright.

A lowracer recumbent is the fastest layout available.

Matt

Re: Aerodynamics thread?

Posted: Aug 03 2008 12:58pm
by D-Man
Can't you get more pedalling leverage on a recumbent vs upright with a backrest and everything?

Re: Aerodynamics thread?

Posted: Aug 03 2008 1:37pm
by recumpence
Yes, somewhat.

One thing to consider, as well, is the fact that a recumbent does not require any muscle input to hold your torso. Therefore, with a recumbent, you always have all your nervous system energy devoted to pedal power. With an upright bike, the most power is available when you stand up. But, that standing reduces your available power for pedalling. So, with a recumbent, you have maximum power available to the legs all the time. Then if you go with a lowracer, you have lower frontal area as well. That is why they are so fast.

Recumbents have poor visibility, though. It is hard (on a lowracer) to turn your head to look around. That is one of the main drawbacks.

Matt

Re: Aerodynamics thread?

Posted: Aug 04 2008 3:10am
by paultrafalgar
recumpence wrote:Yes, somewhat.

One thing to consider, as well, is the fact that a recumbent does not require any muscle input to hold your torso. Therefore, with a recumbent, you always have all your nervous system energy devoted to pedal power. With an upright bike, the most power is available when you stand up. But, that standing reduces your available power for pedalling. So, with a recumbent, you have maximum power available to the legs all the time. Then if you go with a lowracer, you have lower frontal area as well. That is why they are so fast.

Recumbents have poor visibility, though. It is hard (on a lowracer) to turn your head to look around. That is one of the main drawbacks.

Matt
No argument about superiority of recumbent aerodynamics, Matt. Add to this comfort (seat doesn't crunch the gonads and neck isn't cricked by stretching back to view road ahead) and the only disadvantage is PERHAPS the visibility. How about a fibreglass pole which typically has flag but instead has a police-style rotating LED about 6 foot from the road? Would the battery drain be too great? I think not. I've not patented the idea, so feel free to exploit it :D
Regards,
Paul

Re: Aerodynamics thread?

Posted: Aug 04 2008 9:37am
by John in CR
I was talking to one of my employees over the weekend about ebikes, and I find out he's into competitive downhill racing. They do a few km in a few minutes, so avg close to 60km and that includes slower stretches through the technical stretches. I said at those speeds a fairing will help him go faster, and would likely be far more beneficial than spending a fortune trying to save 100's of grams here and there. Anyone want to help me design something that could hold up to those rigors? The only similar thing I could find through searches is the fairings the gravity bike racers use, but that's just coasting down hills on streets at insane speeds.

John

Re: Aerodynamics thread?

Posted: Aug 05 2008 9:10am
by TylerDurden
Safe was a gravity racer. You might be able to pry some info outta him. :lol:

Re: Aerodynamics thread?

Posted: Aug 26 2008 9:42pm
by truckerzero
i know alot of people useing coroplast to make fairings its light and strong
its that stuff like corragated cardboard but is plastic and they make politcal yard signs out of it
it can be baught at local printing companys for 20 bucks for a 4 foot by 8foot sheet just call around to local printers and tell them you want
a sheet in 4mm thickness
try calling smaller print shops a lot of the bigger ones would not sell to me not worth their time i guess
i made a radio controlled airplane out of it and its tuffer than any one elses plane and not much heavyer

Re: Aerodynamics thread?

Posted: Aug 26 2008 9:46pm
by TylerDurden
Coroplast is good stuff. Watch the heat though, it can get soft over 160F.

http://www.coroplast.com/resin.htm

(The small sign shop in my town sells 4'x8' white for ~$15. :mrgreen: )

Re: Aerodynamics thread?

Posted: Aug 26 2008 10:07pm
by Zoot Katz
TylerDurden wrote:Coroplast is good stuff. Watch the heat though, it can get soft over 160F.

http://www.coroplast.com/resin.htm

(The small sign shop in my town sells 4'x8' white for ~$15. :mrgreen: )
This is what I did with unclaimed campagain signs.
Dinos Against Fossil Fuels.

Re: Aerodynamics thread?

Posted: Aug 26 2008 10:12pm
by TylerDurden
Nicely done... who needs a tailbox, when you have a 2m tail??? :mrgreen:

Re: Aerodynamics thread?

Posted: Aug 26 2008 10:39pm
by Zoot Katz
TylerDurden wrote:Nicely done... who needs a tailbox, when you have a 2m tail??? :mrgreen:
The tail is only ~65" but works okay for towing kids on skateboards.

Re: Aerodynamics thread?

Posted: Sep 01 2008 11:17am
by Mathurin
So i've played around with a recumbent handtrike, a Speedy Laser

http://www.speedy.de/laser/laser.htm
laser.jpg
laser.jpg (28.73 KiB) Viewed 1421 times
Big fun but terribly impractical. You have to come to a near complete stop anytime there's a risk of cross trafic cause you can't see shit, captn'. I'd guess cars couldn't really see me well either, but dunno. Can't take the slightest bump, couldn't make it jump over stuff, forget about hopping curbs eh, gotta slow down to a near stop for sidewalk lips. I guess it would be neat on a long distance closed circuit with no other traffic or something, but in real life it kinda sucked. Aero really isn't everything.

Re: Aerodynamics thread?

Posted: Feb 06 2018 5:46pm
by eCue
a Old thread with some good suggestions and great title

The first post is my sentiment exactly , improve the aero rather then add more battery and larger motor. I may end up on a recumbent they look fun as a go cart and life is short

I adjusted this aftermarket 1/4 fairing to be less street warrior and more aero

Image

Image

So far ive noticed a about a 2kmh top speed improvement and its nicer pedaling against the wind.

Image

I am going to do coast down tests on a little steep hill that goes down to a bridge and back up the other side in a gentle yet steep flow. I tag in behind cars on it and hit 75kmh on the pedal bike , for this test i will lift my feet and coast with and without the fairing on

Image

With it picked up 2kmh from 38 to 40 on the above straight stretch although on different days so it was not a tightly run test.

I need run back to back test on a hand picked still day

Re: Aerodynamics thread?

Posted: Feb 06 2018 7:12pm
by wturber
Only the second image is visible. All others have a circle with a dash. I'm guessing the problem is images size?

I'm all for fairings if they can be made practical. My limited experience is that they are more trouble than they are worth. OTOH, since I've added a front basket to my bike, it has caused me to wonder what I could wrap around it to smooth the air flow. Since I already have a area carved out, a limited fairing might actually work.

Re: Aerodynamics thread?

Posted: Feb 06 2018 7:37pm
by eCue
John in CR wrote:
Jul 29 2008 12:58pm
OK, I've had it with the wind slowing me down. My good road routes put me directly into a headwind to start every ride. While it's great for the return trip, it's time to get sleeker. In addition to a small front fairing and a tailbox, I want to do some little things that will hopefully add up.

Tires- These knobby off-road tires have got to go. I don't like them in the curves anyway, and they must be a real aero thief too. Whenever I lift the tire off the ground for a spin test it's like I'm turning on a powerful fan.

Front suspension- I forget the exact relationship, but something I learned in my sailboat design research is that a cylindrical form has the same aero drag as proper foil that is 3-4 times thicker. I want to build some AL or fiberglass sleeves to turn those front shock housings into air foils, along with something similar for any exposed tubular shapes.

John
This is the info I need to push me into action as I have been thinking on making aerodynamic shields for in front of the suspension fork and down down tube behind the front wheel.
I will definitely make the tube fairings now that I know they will reduce their drag upto 3x

not sure if I will but thinking of making a coroplast rear wheel fairing that starts at the seat tube and surrounds the rear wheel so its a full fairing fender.

Re: Aerodynamics thread?

Posted: Feb 06 2018 7:53pm
by eCue
I tried to fix the photos logged out and could view them so Im thinking they are visible now. A aero shield should help about every circumstance Im thinking anyways. I know they would not be allowed in competition :D

big bulky aero shields are not needed imo a bullet head is good enough :D

Re: Aerodynamics thread?

Posted: Feb 06 2018 8:00pm
by wturber
I can view the photos now.

Re: Aerodynamics thread?

Posted: Feb 06 2018 8:20pm
by eCue
Nice , thanks for letting me know I had no clue.

Re: Aerodynamics thread?

Posted: Feb 06 2018 8:52pm
by eCue
Im finding at 30 to 40k the air hits the shield and keeps going off in the direction it was headed. It does not turn back in on you like at highway speed . As it is I search around with my nose to find the air stream as its send off and around. Despite being a small fairing it does not perform small at low speeds.
On a sunny day i will take photos of the garden hose spraying it

Image

Re: Aerodynamics thread?

Posted: Feb 06 2018 10:13pm
by Papa
Non transparent farings are a real bad idea - especially in a tuck when it's most beneficial.
.

Re: Aerodynamics thread?

Posted: Feb 06 2018 10:34pm
by wturber
Papa wrote:
Feb 06 2018 10:13pm
Non transparent farings are a real bad idea - especially in a tuck when it's most beneficial.
.
I guess it depends on how high your head is and such. It looks to me like you can sight down the slope of that fairing and not have your view obstructed any more than my my front basket.

Here's a "cafe racer" fairing that costs a mere $35. I'd have to raise my headlight to make it work on my bike and basket tho.

Image
Bike&Basket.jpg
Bike&Basket.jpg (159.7 KiB) Viewed 795 times

Re: Aerodynamics thread?

Posted: Feb 06 2018 10:48pm
by eCue
Motorcyclists and bicyclists have a lot in common both benefit from wind protection and both require unhindered vision.
You will find the 9 out 10 Motorcyclists cut their windshield down with in 1 week of putting it on.

Why ? because they cant see clearly through it nor can I they suck. First thing I do with a motorcycle windshield is cut it or take it off. As do 95% of Motorcyclists. The remaining 5% don't last long :mrgreen:

Don't listen to Naysayers who pretends to know topics :D Obviously he does not know what he talking about , some people like to pretend. The beauty of a fairing is you look over it. Its NOT A WINDSHIELD lol

Re: Aerodynamics thread?

Posted: Feb 06 2018 11:15pm
by eCue
Thing with the fairing is the normal riding position is wind protected tucking down becomes unnecessary. The fairing allows you to ride a regular position and enjoy the scenery heads up.

Re: Aerodynamics thread?

Posted: Feb 06 2018 11:21pm
by eCue
I have a idea , a kids Halloween captain America shield , painted to match the bike. :D Im trying...

Image

About all i come up with is to add domed front shield