Aero mudguards. Yes they look gastly but they do work.

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Logic11

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bikerumor.com

EB15: Birzman Guards Against Spray With World's Most Aero Fender?

We’ve come to expect an array of beautiful tools from Birzman, but fenders? That’s a new one. But of course it’s not just any fender.…
bikerumor.com bikerumor.com
birzman-fender-aerodynamic-faster-7-600x399.jpg


nullwinds.com

AERODEFENDER™

AERODEFENDER™ wheel fairings simply shield only the uppermost portion of the wheel to effectively minimize overall vehicle drag, while simultaneously increasing steering traction for more predictable control at high speed. • MINIMIZE Vehicle Drag for Unmatched Speed Gains Slice through...
nullwinds.com
IMG_4165_large.JPG


I know whats going to happen:
Bikers are going to take one look and due to the looks are going to have a negative emotional reaction so powerful that their ability to think rationally will be temporarily overridden.
Decision made; imaginations spring into action coming up with every ingenious reason why they don't/wont work.
(It's a shame imagination is seldom kicked into high gear for any other reason but that's just how it is... :) )

The top of a wheel is traveling forward with 2X the speed of the bike. (while the bottom is standing still relative to the ground)
Aero drag goes up with the square of speed and the power required to overcome said drag; with the cube of speed.

As as horrible as these look, they will in fact give you more speed and/or range.
Probably not as much as a good looking fairing, designed with the help of Airshaper, but they will... once you are able to deduct the 'Revulsive Drag' :)

I think these may fit better with the looks of recumbents and velomobiles..?
After all just about anything will help improve the looks of what looks for all the world like a giant wheeled dildo! :D
 
$499 for aerodynamic carbon mud guards? Yikes.

I've seen people give away old broken down cargo bikes, Yuba Boda Boda or something like that, with full upper wheel guards in back before. I could get a pair for $50 dollars and spend the remainder to double my battery size and max battery amps, ha.
 
I'd happily equip my recumbent with these if someone can prove they're effective on an ebike application ( above normal bike speed ). Where's the third party tests? as usual, not finding any. Aerodefender claims a 10-20% gain, which seems high.

$499 for some special shaped pieces of plastic/carbon fiber is insane. Show me a 100 watt reduction and that's still too expensive. These people are smoking crack.

Are any of these kinds of units sanely priced and third party tested?

Seeing the prices of these things makes me so mad. I immediately want to buy some blocks of foam and make molds for which to melt coroplast over, lined with strips of aluminum to make a poor man's version & test it myself on the road. Once proven successful, hand out the plans as DIY instructions.

Partially so that i can find out if the prophecy is true, partially to snub people asking prices like this if the effort is successful.

How much do regular, cheap fenders improve aerodynamics?
 
Nothing new here really.

bikerumor.com

Null Winds Aerodefender aero fenders slice headwinds faster than aero wheels!

Null Winds' Aerodefender upper wheel fairings may be the ultimate in aero gains, claiming to be faster in a headwind than aero carbon wheels & more stable!
bikerumor.com bikerumor.com

Here's an abstract from the technical paper. There was apparently no actual physical test. This was all done using computer modeling.

Effect of Fender Coverage Angle on the Aerodynamic Drag of a Bicycle

While riding cycles, cyclists usually experience an aerodynamic drag force. Over the years, there has been a global effort to reduce the aerodynamic drag of a cycle. Fenders affect the aerodynamic drag of a cycle to a large extent, and fender coverage has a pronounced effect on the same. In this art
www.sae.org www.sae.org

The paper's title is: "

Effect of Fender Coverage Angle on the Aerodynamic Drag of a Bicycle"
​

I'm not a scientist or engineer. But my real world experience tell me that a computer model is useful to inform directions of investigation. Wind tunnel testing will give some idea of practical effects, but may exaggerate them given that a wind tunnel does not precisely mimic real world conditions. Actual real world tests are the final proof - but are seldom performed or performed well since it is hard to control conditions.
 
neptronix said:
I'd happily equip my recumbent with these if someone can prove they're effective on an ebike application ( above normal bike speed ). Where's the third party tests? as usual, not finding any. Aerodefender claims a 10-20% gain, which seems high.

$499 for some special shaped pieces of plastic/carbon fiber is insane. Show me a 100 watt reduction and that's still too expensive. These people are smoking crack.

Are any of these kinds of units sanely priced and third party tested?

Seeing the prices of these things makes me so mad. I immediately want to buy some blocks of foam and make molds for which to melt coroplast over, lined with strips of aluminum to make a poor man's version & test it myself on the road. Once proven successful, hand out the plans as DIY instructions.

Partially so that i can find out if the prophecy is true, partially to snub people asking prices like this if the effort is successful.

How much do regular, cheap fenders improve aerodynamics?
Click to expand...
I never even looked at the prices. They're nuts!

I believe the Birzman fenders do have some numbers:
"...After designing the fender with extensive CFD testing, the finished prototype was taken to the Southampton University wind tunnel to test it against various wheels and other fenders. The results prove the fender to be 2 to 3 times more of an advantage over 50mm toroidal shaped deep wheels with drag numbers of 0.077 for a normal wheel, 0.076 for a deep wheel, and 0.074 for a normal wheel plus Aeroguard at a steady 30 mph..."
​

I would look at making a proper carbon and/or glass fiber fender neptronix. It's really easy actually:

See this wax sheet made specially (soft at room temps) to put over a shape, like a tire:

From there you sculpt the fender shape you want (Airshaper) out of whatever (more wax), finishing it perfectly.
Then you make a female mold out of cheaper glass fiber, to keep both the shape and finish.
Then you whip it off and make the carbon or glass fiber fender from the inside of the mold, keeping the mold for later sales.
Adding black pigment to woven glass fiber makes an end product that looks like carbon fiber.
There are a couple of extra steps, but all pretty easy if you have the cash, product access and postal service. (neither of those here anymore)
 
'we computer modeled it' while real world, instrumented tests would be better is the biggest red flag, lol.

Logic11 said:
I never even looked at the prices. They're nuts!

I believe the Birzman fenders do have some numbers:
"...After designing the fender with extensive CFD testing, the finished prototype was taken to the Southampton University wind tunnel to test it against various wheels and other fenders. The results prove the fender to be 2 to 3 times more of an advantage over 50mm toroidal shaped deep wheels with drag numbers of 0.077 for a normal wheel, 0.076 for a deep wheel, and 0.074 for a normal wheel plus Aeroguard at a steady 30 mph..."​
Click to expand...

0.003 difference in what number? CDA?
Sounds like nothing from here, like it doesn't translate to a single mph gain.

Logic11 said:
See this wax sheet made specially (soft at room temps) to put over a shape, like a tire:

From there you sculpt the fender shape you want (Airshaper) out of whatever (more wax), finishing it perfectly.
Click to expand...

Interesting, how do you make the wax solid? what is an airshaper?

Why not just make v1 with a sheet of coroplast or some other soft plastic and a heat gun laying on top of the target wheel?
 
E-HP said:
What’s the deal with the spokes on the second bike?
Click to expand...
Those are actually VERY clever, if too cheaply designed and made:
They weathercock, making the spokes more aero, no matter which direction a crosswind is coming from.
ie: Your ride will be less unsettled by crosswinds.

Even Better!:
IF these were lightly sprung to return to center; any side wind would be turned into a tiny bit of forward rotational force by them..!
ie: A very slightly wind powered bike that's less affected by crosswinds!

NB that something similar could be done to any vertical-ish round bar of the bike frame..!

I would say that proper (design) carbon fiber doodats similar to this would be ... interesting!
 
It is somewhat insightful to notice that only the top chord of the wheel is traveling at airspeeds up to 2X the bike's road speed, and if you shield that fraction of the wheel, you mitigate the most energetic airflow anywhere on the bike.

But it looks dumb and it doesn't even keep crud off of your butt.
 
neptronix said:
'we computer modeled it' while real world, instrumented tests would be better is the biggest red flag, lol.



0.003 difference in what number? CDA?
Sounds like nothing from here, like it doesn't translate to a single mph gain.



Interesting, how do you make the wax solid? what is an airshaper?

Why not just make v1 with a sheet of coroplast or some other soft plastic and a heat gun laying on top of the target wheel?
Click to expand...

Cd or CdA:
Don't know.
I just know the physics makes sense and that I'd love to experiment with the whole story.

Wax:
It is soft enough at room temperature to take the form (+ X mm) of whatsoever's underneath it, while keeping it's thickness.

AirShaper:

Make:
I have no experience with chloroplast so cant speak to that.

I would probably use wax to get the minimum distance from the tire and rim and make a rough mold over that.
I'd then add something sandable like plaster of paris to get the exact desired shape and automotive paint to get the shiny finish.
Then mold release agent, then make the female mold over that.
ie: Once you have the mold; any subsequent fenders made from it come out already finished and shiny, requiring only a trim and hand sand of the edges.

But that's old school.
Nowadays you'd probably just 3D scan the wheel and fork, design the thing in CAD and then 3D print or mill the plug from which to make the multi use female mold.
 
Last edited:
Logic11 said:
Bikers are going to take one look and due to the looks are going to have a negative emotional reaction so powerful that their ability to think rationally will be temporarily overridden.
Click to expand...

30 seconds later.....

Logic11 said:
I think these may fit better with the looks of recumbents and velomobiles..?
After all just about anything will help improve the looks of what looks for all the world like a giant wheeled dildo!
Click to expand...
 
Papa said:
30 seconds later.....
Click to expand...
Yep! :D
Looks mean a lot! :) And I wanted to make it clear that I'm not immune.
I do get that once you go low and aero there's really one shape you end up with. And there's a kind of beauty to that.
 
Logic11 said:
Yep! :D
Looks mean a lot! :) And I wanted to make it clear that I'm not immune.
I do get that once you go low and aero there's really one shape you end up with. And there's a kind of beauty to that.
Click to expand...
.....
 
Having done hundreds of coast down tests look to find a winning edge in Human Powered Racing (streamlined recumbents) . . .
I have no doubt these fenders do improve aero efficiency.
Is it enough extra efficiency to offset a poor tire choice ?
No
These fenders are designed for the hunched forward cyclist on performance light weight bikes.
Not much use for an upright beach cruiser rider or an average e-bike rider.

Image0050.JPG
 
My knowledge and experience w/bicycle aerodynamics is probably a drop in the ocean compared to what @PaPaSteve knows.

My intuition tells me the dude is on the money..
Upright bike with lycra clad racer tucked into a forward position reduces the human body's frontal area significantly as a portion of the total CDA.. at this point, improvements to the bicycle itself start to actually add up.. before that point, they don't make much sense.

I think the biggest bang for the buck on a typical upright electric bike would be a front bubble and a tail fairing like what's displayed. Only after that point on an upright bike, would a modification like these fenders put a dent in things..
 
Chalo said:
It is somewhat insightful to notice that only the top chord of the wheel is traveling at airspeeds up to 2X the bike's road speed, and if you shield that fraction of the wheel, you mitigate the most energetic airflow anywhere on the bike.

But it looks dumb and it doesn't even keep crud off of your butt.
Click to expand...
Right. That's surely the key reason that the benefit seems to come from having the top portion of the wheel covered. Drag increasing with the square (or is it cube?) of speed, 2x can really matter.
 
Papa said:
.....
Click to expand...
Let me put it this way:
My head says: "Aero, no matter the looks, is good!" (for range and speed)
My heart says: "That aero velo: Giant wheeled dildo! Giant wheeled dildo!"

I can get my head to override that initial emotional response, but it remains...
and I know a lot of people who CANNOT override initial emotional responses and immediately go looking for excuses for decisions based on them.
If you don't want to lose said audience in your writing; how do you do it?? :)
 
PaPaSteve said:
Having done hundreds of coast down tests look to find a winning edge in Human Powered Racing (streamlined recumbents) . . .
I have no doubt these fenders do improve aero efficiency.
Is it enough extra efficiency to offset a poor tire choice ?
No
These fenders are designed for the hunched forward cyclist on performance light weight bikes.
Not much use for an upright beach cruiser rider or an average e-bike rider.

View attachment 361528
Click to expand...
That's a damn nice aero recumbent! Love it!

I NB that the top of both wheels, where they are mostly moving forward at 2X the bike speed are in fact faired in...
However most recumbents dont have the above fairings.

One a similar tadpole recumbent for eg; I think Aerodefender style fenders may well improve the looks.
IMHO the Birzman fender with sides over the very top bit of the wheel may give better Cd numbers and look better..?
 
Logic11 said:
Let me put it this way:
My head says: "Aero, no matter the looks, is good!" (for range and speed)
</snip>
Click to expand...
Whatever spins yer spurs I guess. But I don't race bicycles. I ride them for pleasure, utility and for exercise and fitness. So small gains in aerodynamics don't matter much to me. I'm riding an old Trek 770 road bike. It has a moderately modern 9 speed rear wheel that just barely works with the original Campagnolo friction shifters and derailleur. When I ride with groups, nobody is leaving me in the dust because I'm riding a really old and not particularly aero road bike. When riding solo, nothing much changes in my world if I get home a minute or two sooner or later.

And for my ebike riding, I value fenders that actually catch mud, water and the like far more than I value an aero advantage. After all, I do have a motor and batteries. So I'll sit up and be comfortable while pushing a lot of air around - for the price of maybe one cents worth of electricity.
 
neptronix said:
My knowledge and experience w/bicycle aerodynamics is probably a drop in the ocean compared to what @PaPaSteve knows.

My intuition tells me the dude is on the money..
Upright bike with lycra clad racer tucked into a forward position reduces the human body's frontal area significantly as a portion of the total CDA.. at this point, improvements to the bicycle itself start to actually add up.. before that point, they don't make much sense.

I think the biggest bang for the buck on a typical upright electric bike would be a front bubble and a tail fairing like what's displayed. Only after that point on an upright bike, would a modification like these fenders put a dent in things..
Click to expand...
Yep I agree.
E-bike and recumbent etc aero is a case of a whole lot of little things adding up.
The biggest little thing being a fairing. Preferably one designed with the help of CFD software like Airshaper.

Another interesting rabbit hole to go down is DBD: Dielectric Barrier Discharge.
Its used (or is being tested) on Boeings and things as a means of decreasing the aero drag on the landing gear without any fairing in etc.

Its basically 2 strips of aluminum tape; one stuck to the top of piece of Kapton Tape and the other to the bottom of the same piece of Kapton Tape.
Then you apply high volts/low amps to the aluminum tapes, (the equivalent of static electricity really)
So it's easy, if 'Ouch!-ey', to experiment with. :)
It should look cool as hell at night too.


This paper has some great pictures/diagrams to look at and is a more logical and easy way of doing DBD IMHO:
www.nature.com

Successively accelerated ionic wind with integrated dielectric-barrier-discharge plasma actuator for low-voltage operation - Scientific Reports

Electrohydrodynamic (EHD) force is used for active control of fluid motion and for the generation of propulsive thrust by inducing ionic wind with no moving parts. We propose a method of successively generating and accelerating ionic wind induced by surface dielectric-barrier-discharge (DBD)...
www.nature.com www.nature.com

More discussion here:

Dielectric-barrier discharge (DBD) for drag reduction - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

I was looking into research on using Dielectric-barrier discharge (DBD) to minimize or eliminate the reverse flow in fan shrouds/ducts caused by wing/b
ecomodder.com

NB that uBlock Origin will save you from all the adverts and crap neptronix. I was unaware the ecomodder was even a problem!
ublockorigin.com

uBlock Origin - Free, open-source ad content blocker.

uBlock Origin is not just an “ad blocker“, it's a wide-spectrum content blocker with CPU and memory efficiency as a primary feature. Developed by Raymond Hill.
ublockorigin.com ublockorigin.com
 
What i find interesting about riding recumbents around town is that random people on the street are nuts for it, i get compliments constantly. I'm suddenly a celebrity riding one.

But they will get totally ignored in any gathering of bicyclists or in a bike shop.

Regardless of what other people think, i have a mid drive on the blue bike pictured that does a max speed of 34mph on flat ground, but only hits 28mph on an upright with the rider in a semi tuck. They're also many times more comfortable to ride than an upright.

I enjoy the comfort, extra range, and speed regardless of what others think. I still don't understand why recumbents are so polarizing.

img_20201202_152836243-jpg.283422


dialectric barrier discharge sounds kinda impractical, i'd rather just put a bubble up front!

ps - i use brave browser, has ad blocking built in. Yeah, most forums are nightmares of advertisement, it's pretty sad.
 
wturber said:
Whatever spins yer spurs I guess. But I don't race bicycles. I ride them for pleasure, utility and for exercise and fitness. So small gains in aerodynamics don't matter much to me. I'm riding an old Trek 770 road bike. It has a moderately modern 9 speed rear wheel that just barely works with the original Campagnolo friction shifters and derailleur. When I ride with groups, nobody is leaving me in the dust because I'm riding a really old and not particularly aero road bike. When riding solo, nothing much changes in my world if I get home a minute or two sooner or later.

And for my ebike riding, I value fenders that actually catch mud, water and the like far more than I value an aero advantage. After all, I do have a motor and batteries. So I'll sit up and be comfortable while pushing a lot of air around - for the price of maybe one cents worth of electricity.
Click to expand...
Yep. In your case there's no reason to weigh your rides down with fiddly fairing bits.
But many people, like Toecutter for eg, are trying to replace cars as a means of high speed long range transport with something WAY more efficient.
Others want to do 100mph on an E-bike for the hell of it or race them.

So ye; Different folks...
 
neptronix said:
What i find interesting about riding recumbents around town is that random people on the street are nuts for it, i get compliments constantly. I'm suddenly a celebrity riding one.

But they will get totally ignored in any gathering of bicyclists or in a bike shop.

Regardless of what other people think, i have a mid drive on the blue bike pictured that does a max speed of 34mph on flat ground, but only hits 28mph on an upright with the rider in a semi tuck. They're also many times more comfortable to ride than an upright.

I enjoy the comfort, extra range, and speed regardless of what others think. I still don't understand why recumbents are so polarizing.

img_20201202_152836243-jpg.283422


dialectric barrier discharge sounds kinda impractical, i'd rather just put a bubble up front!

ps - i use brave browser, has ad blocking built in. Yeah, most forums are nightmares of advertisement, it's pretty sad.
Click to expand...
Yep I read and enjoyed your build log for the blue one.
Lots of 'practicle' I have no experience with.

It's the style of bike I like. Especially PapaSteve's but I take issue with the tail.
Thats where a much shallower less crosswind prone, DBD 'cool starship propulsion' look comes in. :)

The pic on the right, turned vertically, on a stubbier, cut off, cool looking tail design of some sort, that's as effective as PapaSteve's.
It's bound to provide a lot of: "What's this? Ouch!" entertainment too! :D
41598_2019_42284_Fig6_HTML.png
 
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