Aerodynamics / Aerodynamic Cost / Aero parts

Does anyone know what causes disc wheels to make a woozy noise. My guess would be the hollow wheels amplifying noise caused by vortices being shed from the legs. Anyone know of any studies/solid sources?

I think the majority of the noise is simply from it acting like a drum and amplifying the noise from the tyres on the road.

https://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/New_bars_from_LOOK_(adjustable_Speedbar'ish)_P6926210/?page=unread#unread

New shiv tt has a very minimal seattube/ no wheel cutout:

Seems kinda odd, but then so did those "extra wide" forks that BC were using on the track.

No wonder I'm am slow I cant get into the 70's extreme position or the TT bike (mainly because I crashed the last one and put myself in hospital).

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It looks like the gap where the lunchbox on the Tri version goes, but seatstay looks lower and there’s a solid chunk below the stay on the Tri version...

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The tri version is for going 20mph with a spoked wheel (misguided Kona regs), the TT version is for going 30mph with a disc

Still seems a bit odd given most bikes try and get the wheel closer to the seatpost. Do they explain the gap anywhere?

it's a visible change that's easy to sell as faster when backed up by data from the win tunnel?

I was just surprised they are using a different mould for the TT version, would have thought it makes sense to cross over the frame....

Appreciate the difference between yaw angles experienced between tri and tt.

Interested that they haven't brought out the mass production version of the Shiv Tri disc yet given that it was launched as a limited edition last October and has presumably long sold out by now...

edit: apparently not as specialized is showing stock in their concept store in plymouth and harrogate

Do they explain the gap anywhere?

I'd expect explanations as part of the marketing launch, which won't be for a few months yet. About a decade ago, Look offered an explanation for increasing the gap from fag-paper clearance to 10-12mm; cutting the amount of drag in the shear layer trapped between the moving tyre and the static frame made more difference than the slight change in form drag from having a slot between the two elements. I wonder whether the Specialized design might act as a leading edge slot which increases the lift generated by crosswinds hitting the disc.

surprised they are using a different mould for the TT version

They have been doing that for years, surely? Others do the same (P5/P5X, BolideTT/BolideTR+, DA/IA etc.), because the different requirements and regulations mean you can't have one bike for both and expect it to be competitive in both markets.

Nice detail from new aerocoach wheel:

Someone will try to copy it I'm sure :D

The Burrows/Thompson Soup Dragon recumbent HPV has now evolved into the Velociraptor. A lot more design and effort has gone on over the past year, while keeping the original shape and minimalist design of the machine inside, although it’s now a monocoque. They should be ready for BM19, too. Wonder if someone will break 90mph this year?

https://www.aim93.com/

Do you have any pictures of the disc brake hub (and drag numbers...)?

and why not stay at 20 spokes for disc but upgrade to dt swiss new aero spokes (1.1x3.3mm). There should be the same drag for cx-ray and them (better aspect ratio but slightly thicker).

why not stay at 20 spokes for disc

Because a 20H disc hub would never work. Oh, hang on...
http://www.wheelsmith.co.uk/product-page/wheelsmith-20h-front-6-bolt-disc-hub-quick-release-only

I'm a bit surprised that a narrow 20H hub is an improvement over a wide 16H hub, and it wouldn't even need to be full width with that rim depth considering how reliable my Shimano RS30s have been with 16 spokes of 3.0×0.9 cross section.

We didn’t want to mix and match spokes and so stuck with Sapim. Number of spokes isn’t as important as where they’re placed in the airflow we found

We wanted the ZEPHYR wheels to have a bit more versatility than just out and out aero so 24x front and back meant that you can really hammer them if you want

We wanted the ZEPHYR wheels to have a bit more versatility

I can see that, but surely the Titan is an all-out TT wheel

It’s actually UCI/ITU legal as well, when we were making our final decision the mixed relay tri in Tokyo was quite important. That Rolf does look nice though, maybe something to play with as a one off?

maybe something to play with as a one off?

I'm probably going to build a 65mm Light Bicycle rim to a narrow 16H hub, I'll let you know how it goes 😳

You want to use my old 32h 65mm rim to test it out on? Disc brake though, I'm afraid so probably no good if you're TTing.