Are FLO wheels really this slow...??

[Balor]

Thanks for indepth reply, though I don't think that is what I meant... or I'm not understanding what you are trying to say more likely. Still, you may try my proposed experiment sometime, when you don't have much to do and feeling adventurous . This effect was confirmed in practice, btw, as some bentrider reports indicate (Some NoComs came with negatively offset wheels as much as I recall).

As for sail effect studies, here is an interesting one, though I presume you must have seen it:

https://www.sciencedirect.com/science/article/pii/S1877705812016189

 

[ed72]

I don't think I can change much on the geometry of the front end of my bike, I guess I need to re-read your proposed experiment better. I must have misunderstood.

I did see that article. I remember an older study done in New Jersey ostensibly for HED H3 aka the original Specialized Tri-spokes.

I had Specialized Tri Spokes in the 90's. In Circuit road races, I would go off the front hard just before a corner that had a strong cross wind from the left. I knew two things. I could gutter anyone else but a few other riders would also go. I also sensed my wheels were giving me a benefit in the crosswind although I could not quantify. Then, I would suck the wheel into the wind of the small break. I would "attack" with the crosswind and we'd have a small echelon. Knowledge was the only way I could do well against stronger riders. The 2-spoke feels similar but even much more so. In a strong cross wind or slightly into me, I seem to get a strong sail effect.....more than a disc for sure.

I am going to repeat the testing using my other powerhub. Maybe a better way to compare is a coast down test. Wheel A vs Wheel B.

 

[ed72]

I think we are talking about different things here. I'm talking more about *stability* than that aerodynamics per se... 35 watts is definetely not something you want to lose, but I cannot afford a 1000$ wheel either, 20$ monokote works for me .

As for steering angle - the article is indeed vague here. It is not the angle that is important, but resulting positive wheel offset you need to prevent from having way too much wheel flop.
Let's assume 55 deg steering, 20" racing wheel with full faring and low-trail geometry people often use on LWBs.

You need about 130! mm of positive offset to keep trail and flop to manageable levels (22mm trail, 10mm flop).

That way, you don't *just* get CoP massively shifted forward, but the wheel acts kind of like a windwane and wants to turn 180 degress to align with air flow at the slightest opportunity - that's what I mean by 'negative aerodynamic trail'.
In a way, this effect is already present on MBB bikes due to boom being, well, 'positively offset' from steering axis, but flat plate drag of disk wheel (laterally) is MUCH higher than that your legs anyway - though you might want to think hard before installing huge TT chainrings with no holes on MBB... but your control over the bars on MBB (given 'Cruzbike cockpit' or wide superman bars, not gunners) is much greater than on most recumbents anyway and while you cannot have too much 'aero', you totally can have too much control if it hinders your performance in other areas - you need just *enough*.

I went back and re-read the recumbent article that you linked. Some of the numbers don't quite add up but for the most part it is spot on, in principle.

We are both talking about stability.

We are however thinking about different perturbations.

I cannot redesign my bike, so, I have what I have. Taking the tailbox off would make me faster in cross winds and also a little more stable but where would I put my rain gear, food, spare tire, tools, and water? So, I am stuck with that limitation. I am focused on the front wheel.

It is hard to know where the pressure vortexes are located WRT to the steering axis as the wind comes off the front wheel. The location and magnitude of pressure changes cause a moment that is felt in the handlebars and can be seen by laterial movement in the path (sort of a damped oscillatory effect). When I say moment, I mean a torque or twisting force, sorry if deemed pedantic.....I know English is not your first language. One way to get a feel for this is to read accounts of triathaloners at Kona where crosswinds are gusty although the cycling speeds are much less than on a recumbent but they do get going on the downhills. Triguys will test various wheels one after another in gusty winds to find one that they are comfortable enough to hold their position in the aerobars. What they are doing is finding the lowest peak moments that they can handle due to the forces from the changes in flow separation...and all wheels/tire combinations are different. I'll try to find a velomobile video clip where the rider was getting blow 6-8 feet by crosswinds. At the time of viewing, I thought to myself quietly that the rider is not skilled. It is similar to this transient response that I speak about. Not exactly the same but the effect is. I could gain more weight as ballast or put a lesser wheel up front or put a big honking handlebar on, but those are slower.

WRT to dynamic effects of the FLO60, it is too subjective to comment. I know the condition likely to cause stability issues to due to crosswinds and/or turbulent conditions but it doesn't always happen. So, it is not predictable. I know one hill where it comes out of the trees and if I let it go to 50 mph, once I hit the area of open fields and if there is wind, I am screwed.

 

[Balor]

GL with the cone project. I forget if I wrote but my little handlebar bag for randonneuring on my upright lowered my drag. I would not go too big but I am sure you know what to do.

Yea. Too big does not affect Cd much but makes overall drag high due to increased A.

Bike alone:

Approximate model, things are even more grim on aero front.

With large front cone:

Btw, if I wanted to simply attach a hemispheric (or, "better" yet, a square like your bag) fairing and call it a day, that would be a disappointment to be sure:

On the other hand, a small fairing like 'Windwrap' seems to provide noticeable improvement:

Aero is tricky. I wonder if I'll be seeing a similar improvement 'in the field' though

 

[ed72]

The second one is about what I was thinking with maybe slightly higher handlebars.

Aero is very tricky. Also as you probably know if doing field testing aka Chung, the Crr is hard to nail down and if you don't have it right, the assumed CdA from low to high speeds will diverge. For instance.....my fast tires on a very good road are only 0.0044 to my best estimates. On my half pipe testing course, the pavement is much courser. The Crr is more than 0.005 and maybe 0.006 but I have not nailed that one down. The Chung analyzer said it was 0.009 but i find that hard to accept.

I wish I had the higher angle stem to get my forearms smoothing the airflow around my shoulders more. It would also potentially even get my elbows more tucked in.

 

[Balor]

Very likely that CRR goes way up on coarser asphalt - Heine, while might be a bit disengenious when it comes to role of compounds, is spot on about "suspension losses", in was independenly confirmed many times now.
Hard to measure though - is is likely highly dependant on your body composition...

Anyway, I find "CRR" depends on so many conditions in practice that I find it not useful.

 

[ed72]

As an aside, it is interesting how the same M5 can require 150 watts to go a given speed on day 1 and either 100 or 50 watts on day 2 with essentially the only differences being different wheels/tires, helmet, kit on day 1 compared to day 2 with skinsuit, fast tires, fast helmet, a few optimizations, and then comparing two different front wheels. I really don't have the extra money to go to a wind tunnel but it would be fun, well maybe not as much as figuring all this out myself. Some newbie riders think they can just buy a V20 or M5 and presto, magic they are as slippery as those who have sweated out the details to integrate the big blob (one's body) into the most optimum position possible and then they have the unmitigated gall to suggest the fast guy is wrong because they need more power on the "same" bike.

When I look at Larry's optimized V20 (the longer one with the plates in front and rear), it makes sense to me why he gets seriously low CdA values. There is no joy following his wheel; it is like he cuts thru the wind like a knife and there ain't no leftovers to grab onto.

Three areas for me to explore is how the airflow might be disturbed by the ribs in the underside of the seat. I had had a spare tire stuffed down there. Taking it out lowered my CdA. The second area is my brake levers and cables although being behind my knees, the air is already so turbulent there that it might not matter what I do. The third is losing 30-40 pounds of blubber.

Before I sell the FLO wheels on fleebay, I am going to do one more comparo.

You mentioned the NoCom, the fairing built for it made it slower as I read. When I read the rules on fairings and how one on the rear is allowed but they give size limits, it seems to me that they got it all wrong.....not that it matters.

If I may suggest. Your CFD diagram shows the head fairly upright. I used to get pissed off how the M5 headrest put my neck way back. But, I got stronger and it actually reduces pain on my cervical nerve roots at the foramen. What I learned (for me), it opens my airway better, too. I had made my own neckrest but have gone back to the stock rest. If your rest is like the one pictured, may I suggest messing around with neck angles to improve breathing. Lay on the couch at different angles and see which make the intake and exhaust of air from the lungs easier......this is one of those breathing lessons learned that I had had. The other is not to be such a belly breather, how one expands the chest in conjunction with the diaphram is important on a bent . Too hard to explain. GL

 

[ed72]

Very likely that CRR goes way up on coarser asphalt - Heine, while might be a bit disengenious when it comes to role of compounds, is spot on about "suspension losses", in was independenly confirmed many times now.
Hard to measure though - is is likely highly dependant on your body composition...

Anyway, I find "CRR" depends on so many conditions in practice that I find it not useful.

Agree. As long as testing speeds are very close and on the same route when doing aero tests, whether Chung or steady speed/power tests, the high Crr does not matter.

It is interesting how a slight coating of water can make a road extremely fast.

 

[Balor]

Well, here is my real position, I have two hand positions actually: one wide "cruzbike" like with shifter and brake access, and the other is not unlike Larry's aero position.
I think I should try and optimise the fairing profile for both.

 

[ed72]

Gain more weight or tighter jersey.

 

[Balor]

Oh, I have lowered the the bars since then. And gone shorter cranks yet - 140mm. And didn't change the seat position... and picked up quite I bit of extra aero AND power, as evidenced by a few PRs both climbing and sprinting.

That implies a was reaching to pedals too much...

 

[ed72]

I wish I had such perfect Pave.

 

[ed72]

I was going to say your feet are kicking up a lot of air down there, 140 mm should tighten it up.

Bottles look ok

 

[ed72]

Getting rid of the gloves is marginal but measurable

Bent riders never fall

 

[Balor]

Gain more weight or tighter jersey.

Yea, it also has a habit of rolling up to my chest. I have some one-piece clothing, but I wear it only for "record attemts".

 

[ed72]

A different helmet with face shield and more reclined neckrest would lower CdA a lot or at least from the blazzing fast picture, it looks like some gains there

 

[ed72]

Yea, it also has a habit of rolling up to my chest. I have some one-piece clothing, but I wear it only for "record attemts".

Need help getting my jerseys on, I bought them when I was 180-185 pounds and now at 220, let's just say they complement the aero belly

 

[ed72]

That bike must be amazing on bad roads. It would be the ultimate for the Silk Road 1200k although the new cruz S40 looks like a Killer Rando bike

 

[Balor]

Need help getting my jerseys on, I bought them when I was 180-185 pounds and now at 220, let's just say they complement the aero belly

Maybe that's where you breathing trouble come from, eh? (Only half kidding). Women were known to faint wearing corsets that your aero suit must be trying hard to emulate...

That bike must be amazing on bad roads.

90 kg of suspended weight on front wheel makes for very plush ride indeed. This is about 2-3 kms of newly paved road that is bordered by a stretch of 'pit upon a pit' from one side and dirt road on the other...
Rear suspension is much worse - lots of stiction in wallmart bike 'metal on metal' bushing plus much less unsuspended weight. (about 40 kg). I'll be doing something about it eventually, maybe 'S30' like leaf spring + elastomer bumper, no stiction there!

 

[3WHELZ]

I still feel faster on my FLOs, and have no plans of giving them up. I have set of new HED wheels that I have left in the box.