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-   -   Drag reduction for upright bicycles (https://ecomodder.com/forum/showthread.php/drag-reduction-upright-bicycles-38621.html)

Grant-53 09-25-2020 06:04 PM

Drag reduction for upright bicycles
 
4 Attachment(s)
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.

JulianEdgar 09-25-2020 06:30 PM

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?

freebeard 09-25-2020 06:55 PM

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?

Grant-53 09-25-2020 06:56 PM

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.

Grant-53 09-25-2020 07:01 PM

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.

JulianEdgar 09-25-2020 07:28 PM

I quite like this.

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

Fibreglass nosecone and zipped stretchy cloth side/rear fairings.

mpg_numbers_guy 09-25-2020 09:06 PM

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.

freebeard 09-25-2020 10:21 PM

Quote:

I just bought some rigid 1/2 in PVC pipe and 45 elbows for a frame.
PVC is such nasty stuff. It creeps and shatters.

What about a welding rod frame with a Dacron skin?

Grant-53 09-26-2020 12:38 AM

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.

JulianEdgar 09-26-2020 01:02 AM

Quote:

Originally Posted by Grant-53 (Post 631957)
Fiberglass was used by Craig Vetter on motorcycles but that requires building a mold.

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.


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