Drag reduction for upright bicycles
 

Consistent with aerodynamic improvements made to other vehicles I would like to see more done to reduce drag and energy consumption of common commuter bicycles. A typical bicycle has a frontal area of 4 sq. ft. and a drag coefficient of 0.6. A rider's body acts like a pump vane. A front fairing and tail box can offer weather protection, cargo capacity, and drag reduction.
I have been experimenting with simple fairings using cut and fold methods of 4 mm Coroplast. The wind load on a fairing attached to the head tube compresses the top of the fairing. The sight line needed to view the speedometer can be blocked. I am continuing to reinforce the front fairing with various forms of tubing. I do coast down tests on a hill where there is a 30 ft. drop in 0.1 mile. A full body fairing that resembles a sailplane fuselage with a Kamm tail can be designed using the HPV body shell software at recumbents.com. There is provision in the software to make a shell for uprights. The file can then be used in CFD software to evaluate the shape.

We probably need to exclude some options if they're not going to be available.

- Recumbents are out?

- Small wheel bikes are out?

- The fairings have to be simple to make and cheap?

https://ecomodder.com/forum/attachme...p;d=1601066932

I like the form of the PVC frame. Will the next generation have some taper in plan?

There is already much being done for recumbents so my focus is on the more common upright. The small tired folding bikes would use a similar shell. The wheel base of 41 in. for an adult bike is typical. The weight would need to be around 6 lb and cost of materials to be under $100 USD. The shell would be from the rider's shoulder to the upper calf. The overall length would be about 60 in. I started this originally as a middle school student project. Wheel treatments would be a disc in the rear and faired spokes on the front. The bike pictured has the same coast down speed as the naked bike.

I just bought some rigid 1/2 in PVC pipe and 45 elbows for a frame. Side panels are also being considered that hinge to the upper part "lambo" style. A full shell will need turn signals.

I quite like this.

https://www.lightningbikes.com/_asse...0/f40-red2.jpg

Fibreglass nosecone and zipped stretchy cloth side/rear fairings.

Something like the red cycle is what came to mind when I saw the title of the thread.

Bending down can reduce frontal area by a bit but not everyone wants to ride a bicycle with their head touching the handlebars.

I've thought about fairings along the side and wheels similar to the red concept above, with the driver sitting upright. A tapering storage area would be behind the driver's back, either for storage or a battery system for an electric bike. Maybe an aero helmet? although I'm not exactly sure how much aerodynamic benefit that would have.

http://donbur.co.uk/gb-en/images/uploads/aerohelmet.jpg

I've always liked the idea of making an electric bicycle and improving the default horrible aero of a bike and rider, but I don't really have a practical use for one.

PVC is such nasty stuff. It creeps and shatters.

What about a welding rod frame with a Dacron skin?

I have a supply of 9 mm aluminum honeycomb but that is not as available as PEX tubing, Lexan, or Coroplast. I went to PEX first due to crash concerns as the neck is vulnerable. I might try short pieces of PEX filled with foam along with the elbows. Fiberglass was used by Craig Vetter on motorcycles but that requires building a mold. I used 1 inch hex wire mesh bonded between 0.005 in. plastic tarp material on the rear cover. Again the need for a rigid space frame. I will look into 1/2 in. foam insulation board bonded to plastic or aluminum sheet. Cloth lycra has been used and I would like to see something waterproof. Padding at the should and hip would be a plus. I appreciate the suggestions.

I think to get decent results you're going to need something with compound curves at the front. I'd probably try blowing a dome from acrylic sheet. Acrylic domes are also available off the shelf in lots of sizes.

https://www.allstarplastics.com.au/w...rylic_Dome.jpg

In the past I have cut one up with a 1mm cutting disc in an angle grinder.

Rick Tegelaar interview: Meshmatics Chandelier for Moooi | Design Dreams | Dezeen

At 1:11 you can see his techniques for forming compound curves with [rather high-end] chickenwire.

Or just get a timetrial bike and skinsuit. They are pretty unstable, not good for turning...because of the geometry but they produce good aero

The requirement was for a commuter bike, and - if we're up for outright low drag - a recumbent velo would kill a time trial bike.

(Basically all fast, low-drag pedal machines are banned from competition. It gets me very cross, because people then assume that fundamental bicycle tech stopped in about 1920.)

This is state of the art in low drag cycling, not a time trial bike...

https://www.designindaba.com/sites/d...?itok=u3s2xI7H

It still brings me out in goose pimples watching this:

https://www.youtube.com/watch?v=qYeuTXj1FY8

Are the cameras in that stalk? Awesome.

duckduckgo.com/?q=ant+farm+media+burn

What goes 'round comes 'round.

The nose section has to be strong in compression both because of pressure and for crush space in a collision. One can make a set of aero bars from a pair of bar end grips, some aluminum angle stock, and tubing that fits on a flat handlebar. The speed limit for most roads commuters use is 25-30 mph. Back angle will depend on riding style and traffic conditions. A low drag shell is needed to get energy consumption down to 0.1-0.2 hp. The ground clearance of the shell would be much higher so that a rider can put a foot down at a stop. The simplest set up is a parabolic nose and a conic tail piece ala Oscar Egg's Rocket.

Doval, Peter Nicholas, "Aerodynamic Analysis and Drag Coefficient Evaluation of Time-Trial Bicycle Riders" (2012). Theses and Dissertations. Paper 28.
Cd listed at around o.6 at 0 yaw.

But don't feel bad matt36415 - as I said, because proper aero bikes are banned* from pretty all competition, most people have no idea of what is really possible.

(*By that I mean: no small wheels, no recumbents, no fairings. Some of these have been banned in competition for over 50 years!)

I know it is late, but I would add that it would nice to think of things that:
1: is compact enough for inside commuter trains.
2: can survive a trip on the front of a bus.

I know those are tall orders.
I did a year of combined commuting to Seattle from Puyallup. Some days and legs required a bus trip, most involved stowing in the train.
Here's my commuter for those days, as it sat on the train. I had to carry it up 3 flights of stairs when I got to Seattle.
https://i.postimg.cc/1tZgD6sn/commute.jpg

That would be the basis of an aero commuter. I worked 6 years for a company that made the interiors for commuter train cars. Our regional buses have front racks for bicycles. An aero shell would not have to be much longer than the overall length of a typical bicycle. A commuter bike does not have to follow UCI rules. There are plans of sailplanes that could be sized and shortened to a Kamm tail.

I beat myself back into bicycle shape that year, then took a hard fall and tore both rotator cuffs bad. I kept riding but eventually had to get surgeries.
The train commute was great. I could ride the train in, and then ride as far as I wanted back home on bike paths that ran with the tracks more or less. I would ride as far as I felt like, then get on the train to get to my car.

You should see what happens when it hits 88 mph.

https://www.youtube.com/watch?v=nUcyURXe5yU

JJ

For more upright fairings than you may ever want to see. Visit this long thread. I see that many of the photos no longer exist, but there are still a few around.

The Recumbent Bicycle and Human Powered Vehicle Information Center

JJ

I see the OP is a contributor to to that thread so he's probably aware of all of the designs (even when the pics worked)!

But it gives me a chance to post these:

https://i.postimg.cc/wT67cTny/Moulto...ecord-1985.jpg

https://i.postimg.cc/G3zsfyFJ/Moulto...-in-aciton.jpg

Uprightdave did display a road bike that used a Zzipper front piece and lycra stretched over a foam tail section. He cruised at 27 mph. I have a photo somewhere. I also have a National Aerocargo front piece that attaches to the handlebar and fork. It is the combination of a nose cone and a tail section that gives the best results. Sailplanes use either a space frame and aluminum skin or a composite monocoque. The SZD-9 bis Bocian 1E sailplane plans are available free (sheet 1) and I would look at making the Kamm tail at bulkhead 6.

The Moulton faired bikes hit 50 mph.

Just over, in fact.

https://i.postimg.cc/XYnDL1CL/Moulto...-Card-1986.jpg

One design criteria is easy ingress/egress. I am 67 yrs and throwing a leg over the top tube of a diamond frame is difficult. If I want a full shell then I can add side doors to my current design on a step through frame. The other option is to have a one piece shell that hinges near the nose and rotates forward.
As for a clear windscreen I would look for a piece from a motorcycle sport bike.

I've go a scar on my left elbow for proof.

I think it's probably time to start building and testing your ideas!

It sounds like you're aiming for a step-through (lady's?) bike with a development of what you've already been trialling in the coroplast.

I'd be using a blown acrylic dome and lightweight frame (laminated plywood strips?) with stretchy cloth and zippers, on one or other of these:

https://i.postimg.cc/RhYfM5B5/IMG-0868.jpg

(My restored/modified 1960s Moulton "billiard cue")

or

https://i.postimg.cc/pT6yjf1K/IMG-0867.jpg

(My work-in-progress Moulton space frame.)

But neither is common or particularly attractive to many people.

Good luck - I think it is a great project. (I never realised how hard it is to improve the efficiency of a machine until I started working on pedal-powered vehicles... makes car stuff look easy.)

www.bikeboom.info/efficiency/: How the bicycle beats evolution and why Steve Jobs was so taken with this fact

I like the space frame. Can you use the trusses as a luggage rack?

HPVA bicycle drag table
 

Before the HPVA became the IHPVA, they published a rather comprehensive drag table to aerodynamically-modified bicycles, including measured Cds for each configuration depicted.
I printed mine from online years ago.
The table is entitled: HUMAN POWERED VEHICLE PERFORMANCE
it shows 20-configurations.
upright and recumbent :)

The front luggage rack mount (takes a Brompton block) and rear luggage carrier are my constructions.

The birdcage X-member was stock?

I'd imagined you modeled it with soldered wire and vice grips.

Yes, stock Moulton.

What Cd is needed to a get 0.40 meter sq. frontal area machine to achieve 50 kph using 100w of power? I will continue to reinforce the nose section and add side panels. Cost down tests to measure the effects.
"If was easy anyone could do it and they wouldn't pay us the big bucks."

Looking at the table I posted, and remembering that required power goes up with the cube of the speed (ie your nominated speed of 50 km/h will require 2.7 times the 36 km/h aero power shown in the table), I wouldn't think you'd be able to get the Cd down sufficiently to achieve that outcome.

Using the table, at 36 km/h, a bike with a frontal area of 0.35 square metres and a Cd of 0.13 requires a total (aero + rolling resistance) power of 50W (of that 24W is aero power, so a total of 90W at 50 km/h).

So that would imply that to meet your criteria, you'd need a Cd of something like 0.13 - pretty hard.

Happy to have someone check my maths - never my best area.

Yes, a really important citation. And what if we gave a bike decent aero drag, and a recumbent position to reduce frontal area?

About 15 years ago I fell in love with recumbent trikes - most of the efficiency of a bike, but with vastly more comfort and stability.

https://i.postimg.cc/9FYYLSyX/GT3-2.jpg

In short:

... I rode a Greenspeed recumbent trike...
... loved it...
... bought a secondhand one...
... felt I could do better...
... found I couldn't...
... designed and made another...
... got closer...
... designed and made another...
... was getting better...
... designed and made another - and was mostly happy.

https://i.postimg.cc/C5mdqjf0/opener.jpg

I didn't do any aero at all (we then lived in Queensland - think Florida for climate), and no canopy would have been bearable.

But I remember my initial absolute arrogance - how I was just soooo going to improve on the Greenspeed (little did I then know that the late Ian Sims was one of the very best engineers I've ever met) because I just knew about proper design like suspension. After years of development, I got to the point of shaving anti-roll bar brackets for reduced mass - every gram was so critical. But it did have what I think was probably the best pedal vehicle ride comfort in the world.

It was fun, and a great engineering exercise. It was also a bit like on this group: the main recumbent discussion group in the US very soon became cross with me when I challenged their longstanding, prevailing wisdoms. What prevailing wisdoms? Boom flex, ride comfort, construction techniques, handling assessments, etc.

They kept on insisting their trikes handled so well, and in the end I did a simple circular skid pan test that easily showed maximum sustainable lateral g's. Certainly not the be-all and end-all of handling, but a comparison starting point. To do well, you had to be able to pedal hard, hold the steering line, and go fast. One guy, who had a tilting trike, was going to smash me. It was very interesting - I waited with great anticipation. Then nothing happened. (Looking at his machine, I think he couldn't pedal at the required steering lock.)

https://i.postimg.cc/QMx4gDPr/skidpan-rear.jpg

Some investor heard about my projects and sent his expert to ride one of my recumbent trikes. It was very weird. The guy plunged down my local hill at full speed and then yanked on maximum steering lock. Not surprisingly, the trike did a barrel roll...

I also built a long wheelbase, full air suspension recumbent bike (not trike), but I hated it.

https://i.postimg.cc/FFj6QT08/LWB-riding-first-test.jpg

But now I am mostly into bikes, like my Moulton.

https://i.postimg.cc/fypyCM5q/7-21.jpg

And I wrote a book on small wheeled bikes, but almost no-one has bought a copy!

https://i.postimg.cc/P5RH8S3K/cover.png

But if you want engineering at its absolute purest, no rules and no restrictions, pedal-powered bikes and trikes are it.

(And a last pic - my first trike. Far too heavy - the start of my learning curve!):

https://i.postimg.cc/Dyc1rMXr/JET-fr...rter-small.jpg

How do upright bikes with fairings behave in crosswinds? (That one bike looked like a rigid sail basically)

I haven't specific experience in changing the stability of a bicycle but...

It depends on where the main 'side' area is with regard to the centre of gravity. So the centre of gravity on a bike is going to be (basically) at the middle of the person riding it, so we want more 'side' area behind the person than in front. (Think feathers on an arrow.) It's why all the speed record motorcycles run rear fins.

Lovely NSU example:

https://i.postimg.cc/DfpR6x3X/IMG-2770.jpg