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Side-wind resistant streamliner.

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Balor View Drop Down
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    Posted: 23 January 2019 at 3:58pm
I am contemplating a 'streetable streamliner' (as in - streetliner), because I participate in brevets and just like long-distance cycling. I am affected by blood pressure drop in elevated legs and high BBs just don't work for me, and fairings is one of possible means of solving relatively low speeds that I experience on a bent.
It is supposed to be something like Traylor's Critical Mass or Picuponcho no Torq - basically, a small step up from a combination of a nose cone and tail fairing, not a true 'flying coffin' type of a racing streamliner, likely even less extreme than Rotator Coyote.
 
Still, I intend to ride on all sorts of roads and in all sorts of conditions, hence susceptibility to side winds and 'truck suck' is extremely important (plus I'm relatively clumsy and just like making weird stuff, admittedly).
 
When it comes to 'side winds' only, when you lean into the wind on a streamliner so not to be blown over, your form gets not unlike an airfoil with significant angle of attack and start to generate lift. Given strong enough wind and light enough rider, especially if your bent is low (ekranoplan effect) you can generate enough lift for takeoff... not good in our case. I'm not a light rider, but I don't want even a theoretical possibility of this.
 
So, what can be done about it, beside minimisation of lateral area and Cd, obviously (which is an other project)?
 
1. Make CG as high as possible, while CP as low as possible.
Kills two birds with one stone - you don't have to lean into wind as much, and tilting moment of inertia is increased, making you a wider window for steering corrections.
 
Of course, you cannot make CG higher than CP... without some technical ingenuity.
For instance, one can take something heavy and prop it up as high as possible, maybe even on a mast - think 'bulb keel', but a 'bulb mast' instead... say, a lead-acid battery.
 
Given than moment of inertia goes up with a square of radius, same mass two times as high will affect your moment of inertia 4 times as large.
 
This 'bulb' can serve as a place to mount DLR lights for visibility as well, serves much better than a flag for a fraction of a drag penalty.
 
2. A refinement of the idea above.
 
Make this 'aerodynamics device' in form of a wing, or, better yet, a lenticular shape.
Something like this:
 
 
This way, when leaned into a wind, this 'wing' will generate downforce, as opposed to sides that will generate lift, somewhat cancelling out this effect.
 
Of course it will generate more lateral drag, with L/D ratio that gets worse the higher lean angle is... not sure how much of a 'refinement' would that be, maybe I should play around with CFD.
 
3. An other idea that makes sense, but not sure how much it works in practice:
 
Make the pressure-recovery 'tail' be somewhat flexible laterally, for it to reorient itself for side wind load, somewhat reducing lateral CdA. I think latter may even add to 'sail effect' in crosswinds.
Anyone tried that before?


Edited by Balor - 23 January 2019 at 4:25pm
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russellbridge View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote russellbridge Quote  Post ReplyReply Direct Link To This Post Posted: 23 January 2019 at 9:00pm
I think you’re fighting against the natural form that a human and two wheels take up too much - it’s impossible to minimise the side area. Have you thought about building a three wheeler with electric assist - stable and very fast...
See Geoff Bird’s amazing Vulcan trike for what’s possible by a (very talented) home builder.
Russ
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Balor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 23 January 2019 at 10:43pm
Yea, that is indeed an aerospace-grade project! Way out of my reach, so far I'm experimenting with a nose cone on my MBB and some small stuff like composite headrests...

https://pp.userapi.com/c845521/v845521202/188ef3/QlUUx_cE7UM.jpg

Electric assist is out of the question though - brevets are purely HPV, even though any conceivable HPVs are allowed (a kickbike once successfully completed PBP... I bet he did not have any 'saddle sores' either :)).
Plus, there is no way it would be able to fit into my elevator, I don't have a garage and live on 7th floor, not to mention that full suspension that is required for any faired apparatus (especially out there) is an extremely complex affair on a trike.

I'll be experimenting with other means of getting around my physiological limitations like a combined arm/leg drive and adjustable geometry, to attack it from different angles and adopt the most successful one.
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atlas_shrugged View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote atlas_shrugged Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2019 at 9:45am
Have you considered 'storm strips' - these are placed length-ways along the top of an HPV and are said to disrupt sideways laminar flow over the top of the HPV.
 
I have no personal experience of using these storm strips.
 
I wonder in the future if we will use hybrids with bikes turning into trikes/quads when the need arises. This will compromise weight and simplicity but may improve safety.
 
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Balor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2019 at 11:27am
Makes total sense - basically, like a turbulator wire in a classic experiment with spheres (or golf ball dimples)... provided, of course, the air is not already turbulent over the top, depends on reyonold's number (and other factors) obviously.
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Balor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2019 at 11:46am
Originally posted by atlas_shrugged atlas_shrugged wrote:

 
I wonder in the future if we will use hybrids with bikes turning into trikes/quads when the need arises. This will compromise weight and simplicity but may improve safety.
 

Not likely without heavily adjustable geometry.
Best-behaving two-wheelers are high.
*Safe* 3+ wheelers are very low.

Simply having a few wheels lowered will not work... and tilting trikes do not combine 'best of two worlds' - more like 'worst of two worlds' if you ask me, once you get to truly analyse how they work :(.


Edited by Balor - 24 January 2019 at 11:46am
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Balor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2019 at 6:51pm
By the way, if you think about it, having a set of 'training wheels' of sorts that ONLY get engaged during relatively significant lean might be a good compromise - otherwise they hover a few cms from the ground (which allows for suspension to work on main wheels as well).

They can be extremely small (say, 10cm polyurethane skating wheels) and castering  - hence it will not affect your efficiency much even when engaged. I think I saw something like that before...

It gives you passive stability, tip-over protection, yet for all intents and purposes your bent is two-wheeled with some (not much) aero penalty if you use wheel spats like on some aircraft with unretractable landing gears.

Making them if not 'retractable' (way too much complexity), but at least somewhat 'storeable' or quickly removeable may solve the 'size' problem as well. Hmm.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2019 at 7:52pm
Hmm... it would lead to rather confusing dynamics though - some curves could be negotiated leaning into them like on a bike (before inner wheel contact), but in others you'll have lean out of the turn and ride outer wheel instead like on a trike. Tricky...
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Balor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 25 January 2019 at 5:50pm
Ok, it seems everything is invented already :))
 
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Balor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Balor Quote  Post ReplyReply Direct Link To This Post Posted: 25 January 2019 at 6:51pm
http://www.autocycles.org/pulseoutrigger.html
Problems encountered with outriggers on this design suggest it might be suboptimal for a HPV unfortunately :(.
High tire wear sound like a lot of rolling resistance.
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