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NoCom aerodynamics

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T O P I C R E V I E W
Victor Ragusila	Posted - 05/26/2012 : 09:31:58 Hello Everyone I raised the issue of the NoCom chain stays being aerodynamic devices to shield the rider. I am opening this can of worms in a separate thread at the good advice of Sean. So the rules say that : "The vehicle construction shall be such that its shape does not overtly direct airflow around the rider's body, nor attempt to reattach the airflow behind the rider by use of tail fairing devices. The only exception being the use of an aerodynamic shaped helmet. The vehicle can incorporate aerodynamic fairings to make its structure and components more aerodynamic. Allowed fairings are: rotating wheel covers and splitter plates." Now my question is two-fold: 1) first, are the chaistays able to re-attach the flow? I do not have a NoCom unfortunately. A tuff test on the chaistays would indicate whether the airflow is attached (all the tuffs are nicely pointing backwards) or detached (the tuffs are randomly moving along). The M1 Lowracer that Mike rides has even bigger chainstays, and it would be interesting to see whether that one has any attached flow. 2) If the flow IS attached, are the chainstays legal? I see an argument possible for each possition: ProChainstays: They are a necessary bike structure, not an extra tail fairing that is there to only improve aero. Their big cross-section is necessary for structure stiffness. AntiChainstays: They could be much narrower and have the same structural properties, yet they are shaped that way to improve the aero behind the rider, specifically to fair the torso. I am curious if anyone is able to do a tuff test. I can try to set one up at Kenosha or next year Michigan, if anyone wants to volunteer their M1 or NoCom. The tuffs are easy, we would need someone with a decent camera riding besides the NoCom at low level to film it. I do not raise this thread to bring anyone's records down. I want to understand the aerodynamics behind these bikes, as well as the rules regarding each class of competition. Victor Edit: Reading my original entry in the thread about Aure's record attempt, I realize that I was implying that there is a double standard in the technical specs. This was NOT my intention, and I do apologize that i sounded that way. I do not think it is anyone's intention to have a double standard. I was not clear on the rules, and I realize that there is a lot of interpretation that needs to be done.
25 L A T E S T R E P L I E S (Newest First)
randy	Posted - 06/19/2012 : 14:41:44 Damn, I edited that last sentence and screwed it up in the process making me sound more retarded than usual.
randy	Posted - 06/19/2012 : 14:38:39 What the WRRA does is their business. I'm speaking, philosophically, as a fan of recumbent race bikes. Broadening the class (everywhere, not just the WRRA) opens up the design possibilities much more which I think is a good thing. Besides, who does it hurt? Not Aure, he's over 2mph faster than the best tailfaired rider. Look at the HPRA partially-faired results. Is there any point having a separate division for them because of the supposed aerodynamic advantage? From now on the only way to have a viable chance at breaking the "unfaired" record is to adopt a flat-as-a-board supine position. Personally, I would like to see Aure's position and bike go head-to-head with the likes of Razz-Fazzes, Birk Comets and the like.
Speedbiker	Posted - 06/19/2012 : 14:14:15 How about actually leaving nonfaired, nonfaired(a novel concept). Add shoe fairing and whatnot to tailfaired. Making it partial faired.
randy	Posted - 06/19/2012 : 12:44:30 I like "anything goes behind the rider". In front, "any INDIVIDUAL part (including shoes) may be faired". Combine the tailfaired class with "unfaired" because riding flat on your back is a horrible way to ride a bike.
Speedbiker	Posted - 06/19/2012 : 10:57:36 Obviously, higher pressure(relative) ait is trying to join the lower pressure(high velocity) air rushing over the top of the rider. Regardless, I like the Randy Rule. Nothing outside lines drawn from the body to a verticle line created by the rear axle. Unfortunatey, the M1 is outside this definition, but John can fix that! Yes, some clarification may be needed.
alevand	Posted - 06/19/2012 : 10:27:36 Flow looks separated, coming up from under the seat. Would be good to fill in this area. C: Tony Levand
Larry Lem	Posted - 06/19/2012 : 08:59:38 As some folks say the NoCom seat stays are way too small to help the bike go faster and therefore aren't a tailfairing, and that tailfairings have to be really huge, starting wider than the rider's shoulders to be effective, then are intermediate-size tailfairings such as the M5 tailbox not to be considered tailfairings with respect to the WRRA rules? How big does a fairing need to be to be considered a tailfairing? I am not looking for a specific answer. I am pointing out the possible need for more-specific rules regarding fairings to prevent confusion in the future. We should not rely on "We all know a tailfairing when we see one." as there is obviously a difference of opinion there already. Randy suggested some rules. Maybe these should be discussed further. Larry Lem
warren	Posted - 06/19/2012 : 05:56:59 Nice videos Sean!
sean costin	Posted - 06/18/2012 : 17:50:19 Video links to yarn tufts on the Nocom. Air flow directly behind rider is perpendicular to the direction of travel. Note interesting upward flow behind my neck. Probably not what you expected. Sean http://s274.photobucket.com/albums/jj262/scostin/?action=view¤t=IMG_1445.mp4 http://s274.photobucket.com/albums/jj262/scostin/?action=view¤t=IMG_1451.mp4
mhelander	Posted - 06/07/2012 : 22:29:14 quote: Originally posted by Larry Lem Don't believe Strava on power. It thinks you're riding an upright bike. I won't. But it gives kind of ballpark figure. I'm trusting RChung's CdA & Crr calculations more. Not done those yet for my lowracer, still waiting Ultremo ZX 451 tires to got shipped... Cheers, -Mika MetaPhysic 700c @ 2011, M5 CrMo Lowracer @ 2010
Larry Lem	Posted - 06/07/2012 : 12:59:14 Don't believe Strava on power. It thinks you're riding an upright bike. Larry Lem
mhelander	Posted - 06/07/2012 : 11:44:21 quote: Originally posted by Speedbiker Yeah, nobody believes Sean's wattage. I think he's dyslexic and it's actually 320... Huh, that saved my day... did just 10 km TT leg to push little steam out, time was not sub 15 minutes but Strava estimated (using HR, speed and vertical data) 283 W and 164 bpm HR averages. Cheers, -Mika MetaPhysic 700c @ 2011, M5 CrMo Lowracer @ 2010
Zyzio	Posted - 06/07/2012 : 09:51:46 LOL... PeterB
Speedbiker	Posted - 06/07/2012 : 09:38:06 Yeah, nobody believes Sean's wattage. I think he's dyslexic and it's actually 320...
Zyzio	Posted - 06/07/2012 : 09:22:12 Sean, Wow! 29 on 230 watts - I need a Nocom. I agree about the concave shapes not being as representative, but I envision a high pressure bubble forming in the cavity and the air stream flowing around that. Perhaps the flexible lycra tail fairing (as well as the overall shape) is not as effective. I remember seeing M5 tests, which were also done on an indoor velodrome with a power meter and they claim a 9% improvement (to their low racer). Granted, it's a manufacturer's claim, but my 5%-8% improvement seems to confirm those. I guess another thing to consider is the body shape of the rider, seems that tall, skinny guys should race in the more horizontal position and the short, stubby ones may need a tail fairing. PeterB
sean costin	Posted - 06/07/2012 : 04:59:41 29 on 230 watts. Sean quote: Originally posted by warren Sean says 230 watts is good for 30 MPH on his NoCom. -Warren.
sean costin	Posted - 06/07/2012 : 04:58:22 21 and 22- because they are concave in the front are not nearly as representative. Note that their drag is also considerably higher despite having the tails. John Burrell is an experienced local rider I spoke with last weekend at the time trials at Bong. He has a relatively upright carbent bike which he has been experimenting with a commercial fabric tailsock. John used a powertap power meter on the velodrome and was not registering any improvement. He want back and forth with the manufacturer with recommended adjustments and still did not receive any benefit. quote]Originally posted by Zyzio Sean, Thanks for posting the drag coefficients for the various shapes, it's very useful. You mentioned 16 & 17 and 18 & 19. How about 20 & 21? There is a 4% reduction between those two. [/quote]
Speedbiker	Posted - 06/06/2012 : 19:11:31 It all depends on how aero he gets it. If I recall, Sean went faster on less watts. But Byron probably won't go knuckle to knuckle, narrow drum brake hub, bonded in bb, and all Sean's other mods. Which is too bad because Sean claims his bike is comfortable and handles great. Will Byron's elbows be sticking out, I wonder?
warren	Posted - 06/06/2012 : 18:21:23 Larry and I met with Byron Grimley last night and outlined what components he would need to order to get his "new" NoCom up and running. He is looking to set some long distance records next year. We'll get the bike built up for him and he'll start getting acclimatized to it this year. He said he can put out around 270 watts for an extended period of time on an upright. Sean says 230 watts is good for 30 MPH on his NoCom. -Warren.
Speedbiker	Posted - 06/06/2012 : 16:06:39 But, did you ever hear van Vulkenburgh speak? Those were the days! Abbott, McCready,.etc... Wow.
Speedy	Posted - 06/06/2012 : 15:57:27 If you consider the bicycles drafting behind trains in the mid thirties ... drafting and it's effects have been noted well before Paul Van Valkenburgh gave his talks to the IHPVA. Not to diminish Paul's and his brothers contribution to the early days of HPV racing and design. Any upright bike rider who has ridden any distance with a good drafting partner will attest to the benefit that can be felt from either position ... front rider or back rider. Do note that some tri bikes / events water bottle are not permitted to be place behind the seat as it's considered a turbulence decreasing device that increases performance.
Speedbiker	Posted - 06/06/2012 : 14:12:30 Oh, and if my junk memory is correct, it was the Van Vulkenburg effect(turbulent behind a vehicle "pushing" another vehicle) that was credited for Howard's 167 mph. That, more so than drafting. Your own turbulence never pushes you. It has no energy to do so. Sean's diagrams relate entirely to how different shapes minimize or compare the turbulence that causes drag. As Weaver simply put it to me, how large your turbulence is equates to how big your effective size is, aerodynamically speaking.
Speedbiker	Posted - 06/06/2012 : 14:04:56 Good points Steve. As for #3, as far as bicycles are concerned, I believe the effect is immeasurable. Perhaps nonexistant. In stock car racing it appears true, as Van Valkenburg predicted. Funny how things change. I believe race car aerodynamicist Van Vulkenburg spoke at a very early IHPVA seminar.
Speedy	Posted - 06/06/2012 : 13:09:34 a few aero rules of thumb Laminar flow ... whatever aero mess gets started on the leading edge can not be corrected downstream ... so ... by this statement a rounded leading edge on a shoe should be a wise move. For every 1 wide go 2 long ... by taking the width of the rider and taking it 2 times in length there will be a reduction in drag. I know this to be a true rule of thumb. So if the frame structure was done in this way it will provide advantage. So by taking Randy's suggestion of a straight edge from shoulder to rear axle an aero benefit will be seen. Drafting ... by getting as close as possible to the lead rider the second person reduces their drag and it reduces the suction to the front rider allowing for a faster pace. Obviously filling the space behind a rider in any manner is a good thing.
n/a	Posted - 06/06/2012 : 11:26:42 quote: Originally posted by Zyzio I'm very curious about the performance of Alan's NoCom with the factory tail fairing. Peter, If I can get a 28 mph avg at a TT then I'll put the TF on and see what happens. At present, I'm still tweaking the steering. I modified the handlebar with rounded plugs on the ends. Allows more leverage with better hand grip. Better control in wind. Worked rather well last night. Need to keep working on this steering tweak.

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