Aero project for a diamond frame road bike

[low&slow]

With my interest in vehicle aerodynamics and efficiency I wondered about how effective simple partial streamling would be for conventional diamond frame road bikes. I decided to apply the same approach that I have used with my Silveraero/aerotrunk moto. I made a handlebar windscreen of coroplast over a wire framework and a tailtrunk of coroplast and doorskin ( very thin plywood). The tailbox was a bit of a challenge to finally get mounted rigidly enough so that it stayed in alignment behind the rider. I was finally able to test it last week and found that it worked fairly well. The improvement was most notable as I cruised at higher speeds (15 mph + ) and particularly on a downhill run where I exceeded 34 mph. The only downside was on steep uphill climbs where the added wieght ( 2-3 lbs) was a factor. I rate this project a success and will keep working to refine and improve it. Like my aerotrunk project , the tailbox can carry a lot of stuff without increasing air drag.

The reaction from other bicyclists was mixed; some shaking thiers heads , others suprised. I usually get a wave or a thumbs up from other motorcyclists
but I haven't received that feedback yet from another bicyclist. What do you think?

[Grant-53]

Vic, I have been working on a very similar design. There are refinements to be made but the concept is correct. I have made front sections for flat handle bars that attach to the frame. They are cut and overlap fairings resembling the Windjammer. They extend from the knees to the shoulders. The tail box can mount to a standard rear rack or a piece clamped to the seat tube. I angle the upper section to match the rider's back angle. I have some old briefcases to strip for hardware. Current mods include mounting car mirrors and hinged side panels. The closing the gap between the rider and tail box is critical just like the Vetter Challenge machines.

I have had many men stop and ask me if I plan to patent my design but I expect to sell plans instead. Folks are concerned about cross winds but this is cured by mounting to the frame instead of the steering.

[renault_megane_dci]

I really wonder if the trade off between frontal area and drag reduction is really that good.

I am led to believe that the rear end helps no matter what but the front I am not not so sure (except as a more comfortable ride)

[low&slow]

@Grant-53, wow, great minds think alike!
Thanks for the suggestions, I definitely need to close up the rider/tailbox gap. I like your idea of making the front fairing frame-mounted rather handle-bar mounted like mine.

@renasult_megane_dci, My front fairing is pretty close to having the same frontal area as without. It does show an improvement at higher speeds and I hope to get more out of it as I work to optimize it.

[Grant-53]

My fairing as pictured is primarily for protection and needs a tail box and sides for drag reduction. A year on the road has been logged. Next I am adding side mirrors and side panels. A step through frame is in the shop for me to add the tail box as I am not as limber as I once was. My target is a 25% reduction in drag and noticeable improvement under 20 mph in coast down tests.

[Sven7]

You might want to peruse these:

IHPVA - International Human Powered Vehicle Association

It's mostly recumbent-oriented but you do see a few articles about streamlining diamond frame bikes. The first issue has a lot of DF pictures.

When you're riding in the drops, how does your face line up with the fairing there? Or, more concisely, are you tucking behind the fairing?

[Grant-53]

Sven7, the link to IHPVA didn't come up tonight but I will try another approach. We have a upright thread under Technical/Bike Building at recumbent.com and I use the same handle. It looks like Vic's chin would be close to the top of the fairing when on the drops. When I went to using a full face Bell motorcycle helmet this winter I had to trim an arc section out of the top of my fairing.

[Sven7]

http://www.ihpva.org/HParchive/PDF/01-v1n1-1977.pdf

Does that work? That's just the first issue. I'm attached some screenshots of the bikes, but mind you there are about three times more upright streamliner photos in the issue than just these.

They give you some idea of the relative speediness of certain designs, partial fairings, etc. because the recorded speeds are listed.

If it were me, I'd look at extending that egg pod down a little to cover your legs, put an aero disc over a wheel and find a bulbous shaped piece of material to use as a nose cone. But then again, I'd just buy a recumbent.

[Grant-53]

I recommend that the fairing extend to just below the knees for two reasons. First the calculations I made indicated that drag from the calf and feet is less than that of an extended body to enclose them. The cross section of the legs on an upright is smaller below the knee. The other reason is the need to put a foot down easily when stopping.

[Sven7]

Interesting. We really do mainly battle the problem of a vehicle in which every part moves in the airstream. Nearly every problem on streamlined uprights seems to stem from this. Recumbents aren't as bad, and velomobiles are downright doable.

Maybe those teardrop speed-skier pants would be effective on a DF, if you could keep from sweating. It's so hard to piece-meal the entire vehicle around a moving rider.