asgelle

Are you being deliberately obtuse or can you not see that a windmill, sail, or disk wheel are all ways of extracting energy from wind? And yes, we do extract energy from the wind in a headwind, in that case the longitudinal component of the force vector happens to be directed against the direction of motion. For other combinations of geometry and wind direction, this component is in the forward direction. Why is that concept so hard to grasp? Perhaps a review of vector arithmetic might help.

Ih8lucky13

Hey, how exactly is a rainbow made?



How exactly does the sun set?



How exactly does the posi-trac
rear end on a Plymouth work?



It just Does.

DocRay

Sure, when the windmill, sail or disk are stationary or slower than the wind speed.
The point of cycling is too go faster than the wind.
Please tell me your not an engineer. For F--k sakes, you may as well be comparing dynamos to cucumbers.

asgelle

O.K. after reviewing vectors, take a look at frames of reference.

Kachunk

The ignorance in this thread hurts my head. Would all of you who have not had at least one course in fluid dynamics please shut up and listen to asgelle? He is the only one who has consistently been correct in this thread. And DocRay, I don't know anything about your ****ing bottom bracket, but that's ok because you don't know anything about aerodynamics.

The human powered vehicle folks have been taking advantage of negative drag for a lot of years--they design the bodies so that with typical crosswinds they get a small amount of propulsive force. Just exactly like a sail. prendrefeu, apparently you don't grasp the concept of airspeed vs. groundspeed. Air is not fixed. In a crosswind the direction of your airspeed and the direction of your groundspeed are not the same. Your airspeed is towards the upwind direction from the direction of your groundspeed. The angle between your airspeed and groundspeed is known as the yaw angle.

Oh, and the claim of 11 Watts extra power is only true if those 80g of negative drag are produced at ~30 mph. I suppose that's legitimate because that's a typical speed for a good TT.

DocRay

Sorry, but we know how all those things exactly work.

But, "there's things we don't want to know, important things!"

Ih8lucky13

Thank you.

chzman

i try to smile when i'm on the harley... dimples clearly reduce the force required to hold my head up

DocRay

Asgelle is misusing terms like a sophomore engineering student, and now is telling us that we can gain energy from wind as we pass through it, like a windmill. And, engineering can do anything, including break the laws of thermodynamics.

Sounds like some guys need to re-take some fluid dynamics 101 and basic physics 101.

Engineering is one of the few professional degrees one can get without a practical exam. Good to know when you're driving home tonight and need to hit the brakes.

Sorry, yes, disc wheels are faster than spoked wheels under ideal lab conditions and some TTs, but Zipps discs are not better than any other brand. Instead of working on negative drag, they could try working on some reliability.

The idea that any of this is anything but total BS comes from the fact that those wheels have "zipp" relief-stamped in them. Are you seriously telling me that dimples need to be 'Zipp' shaped?

waterrockets 

While I would say it's Zipp's responsibility to demonstrate that forward force is generated on this disk wheel, I still say it's possible.

Stationary windmills and sails going slower than the wind are relative to the ground, not the wind. They're all moving through the wind's frame of reference. A sail can create enough lift in the forward direction, leverage that against the keel to slide along an edge, going into the wind. It's no stretch to replace "keel" with "tires" and have an edge to slide on and resist sideways drift.

So the only question remaining is: can a rotating wheel moving 30 mph into 15-degree apparent wind generate any lift in the forward direction, using the wind as an input?

It doesn't seem that far-fetched that there is some wheel-arc shape that when slung across the top of a wheel at 60 mph could generate some lift from a crosswind. Since the top of the wheel is moving between 30 and 60 mph (for a pro TT), maybe some eddies can be created that, when blown by a crosswind, try to move forward along the wheel's surface and push forward on the contours.

I dunno. I'd like to see some test results. I'd have no trouble believing it's total crap either, but there are no data in either direction.

BTW: I think the dimples are bunk too -- they're for blunt objects. I'd be interested in a dimpled aluminum baseball bat, and maybe a hammer

Rutnick

you can put a dress on a pig and well...it's still a pig. I believe that was one of the smart *ss remarks you made to me when I bought some ceramic bearings for my Neuvation SL2 wheels.

OMG...you have ceramics in that BB? Pig in a dress DEFINITELY! Ti in that BB? Lipstick too!

I used isis for about 5k miles when I was just getting back into road riding. I STILL have a bike with an ISIS BB that I'm getting ready to replace. The bike has zero miles on it and won't be ridden until the cranks are replaced. Since I had surgery on a broken Fibula, that might be 3-4 more weeks.

As a MTB RACER, I used square taper FOREVER. Race Face Turbines were on my race bike until this year. That's a LONG time using the same cranks and BB. Updated the frame over the years but the square taper BB and cranks remained.

This year I bought a full Ultegra bike. My first experience with the new design and outboard bearings. I was VERY impressed. It was my 3rd year back on a road bike and I really dug it. Stiff as hell and I could feel it. Got my campy bike out and was riding it and noticed flex in the cranks or probably bb spindle (square taper). After seeing that, I sold and replaced the cranks with the new campy design and the bike felt even faster. With square taper, I could actually look down and see the flex in the down stroke.

With all that said, my race MTB now has the new shimano cranks too and it paid off. Right before I was hurt, I turned my fastest hot lap on a trail I was getting ready for a 12 hour race. Was I stronger? Maybe but my shifts were better and the cranks felt like more power was going to the trail. Even loving my Race Face and square taper like I do, I could tell a difference on that bike.

I'm not some shimano ***** but I can tell you definitely after using square taper, ISIS, octalink, shimano's external setup and campy's offering that it is better than ISIS and square taper.

I wasn't a big believer in square taper vs ISIS or Octalink but I am of the new setups. Personally, I feel you are using old tech. I don't care if it has ceramics, Ti and covered in chocolate. Like I said, Chris King developed ISIS and they dropped it because they couldn't get it to work up to THEIR standards. Chris King headsets have a 10 year warranty. I trust THEIR judgment unless you think that is marketing BS too.

For me, while I am not a believer of all things shimano. I do believe in their new cranks and the shifting of their cranks. I think they shift better than any offering I have used and that includes some carbon cranks I have had. I do also believe that the design of the campy cranks is better but the shifting isn't as good as the shimano offering.

This all comes from a guy that was using down tubes and bar ends until Feb 2006. I was friction shifting 9 speed road bikes. I've used a lot of tech since then.

So I will say it one more time...not freaking impressed with a Ti ISIS BB with ceramics. I've used ISIS. Not impressed.

So if I say that about Shimano and why use Race Face cranks? Because at the time, they were the lightest cranks I could get. Still lighter than what they replaced but man...the shifting is so much better now and it does feel stiffer.

Ih8lucky13

What practical exam did you have to take, for your PHD in chemistry.

gcl8a

For those who care to learn something, here is a very crude schematic of what's going on. It's really not that difficult, nor mysterious, just basic fluid mechanics:



Please ask questions, but please stop insisting that it is impossible, when you have no idea what you're talking about. It is not.

mollusk

+1.

I teach aerodynamics on occasion and now my brain hurts after reading this tread.

ratebeer

I'd like to see a few wheel companies chip in to have third party labs test their wheels. Heck you could probably have Bicycling and Triathlete magazines chip in to either get the shared or exclusive info. It would sell more magazines and bring in a lot of web traffic and incoming links (great for search engine rank).

As it stands now, my gut feeling is that Zipp's own research is as pie in the sky as it can possibly be without causing an uproar, which another BF-slammed retailer has pointed out as being around 5 - 10% for his products.

biffstephens

I sure do like the way they look!!!

Kachunk

Oh thank god. I was afraid I was going to have to do that in mspaint.

patentcad

In that case, you should feel right at home.

gcl8a

My self-imposed, cold-turkey exile from Bike Forums lasted a whole two days because of this thread. Reading it is like watching Miss South Carolina answer that question on YouTube, but without the hooters...

jooaa

Here's your dimpled baseball bat:
https://web.mit.edu/newsoffice/1994/bat-0302.html
With wind-tunnel testing showing the drag reduction due to dimples.

DocRay

LOL..this coming from the guy with famous brain-tickling threads.

patentcad

How would that impact you?

DocRay

OK, here's a question: does any of that work on a wheel actually on a bicycle?

Looks fine if you ride backwards without cranks and your legs tucked up around your chin. But explain to me, oh wise theorists, how air that clean hits a rear wheel of a pedaling cyclist's bike.

This is now in the domain of Honda ricers who mount Pepboys airfoils on back bumpers.

Maybe I'm just too old and remember the old Shimano ads in the 80s where they would put individual parts in a windtunnel and claim less drag.

Or, maybe I read too many academic studies that show that a TT helmet and not wearing gloves makes more real difference than any wheelset.

ANY OTHER TRICKS OF THE TRADE YOU'D CARE TO SHARE?

Cote: Most people don't realize that a nonaero helmet creates four times the drag of a nonaero wheelset. So you can spend two thousand dollars on a wheelset, or spend two hundred on a helmet and be faster. How you put your race number on matters more than having an aero wheel; today, we glued on our numbers to get them to fit flatter. Then there's water bottle placement: On a round-tubed frame, having a bottle on your seat tube is more aerodynamic than not having one at all, and it's much more aero than putting it on the down tube. And wearing gloves in a time trial will slow you down more than using a nonaero front wheel.

https://www.bicycling.com/article/0,6...4995-1,00.html

Or, maybe I watch to much real world racing, where Lance Armstrong famously won a windy TT when he removed his aero wheels for normal rims.

But please, continue, explain to us all how negative drag is going to solve the energy crisis with simplistic diagrams and analogies to sailing.

Ih8lucky13

Can you ever admit you are wtrong, or even maybe that you might be wrong ?

You will change arguments and make sarcastic responses,(instead of dealing with the facts at hand).

You are a bitter person.

gcl8a

Sure. The numbers will be different if you include a rider, and I don't know if Zipp included the effects of the frame, but there is no reason why the wheel cannot provide thrust under the given circumstances. In fact, I was recently wondering why no one had optimized their wheel to take advantage of this effect. Looks like I missed the boat.

I'm just trying to explain the theoretical basis for making such a claim. It is possible, without violating any laws of physics. Whether or not this particular implementation works in the real world, I cannot say.