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 Control surfaces on streamlined bikes
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/09/2019 :  00:59:22  Show Profile  Reply with Quote
Wings are obviously not viable (will scrape in turns), but a tail rudder makes sense to me:

I already considering a 'visibility aid' like on Stuart's carcycle:
https://microship.com/bob-stuart/

But wouldn't making it an actual tail rudder achieve pretty much the same what Robert Horn was trying to achieve with his two-wheel steer lwb motobent (faster steering response given long wheelbase) and exactly when we need it (at high speeds)?

No need to have complex arrangements by steering the driven wheel or variable steering direction/ratio (otherwise you'll get greatly increased steering radius). Obviously, no help with low-speed maneuvers, but I plan on having a reverse gear anyway.

Are there any precendents of people attaching control surfaces to their bikes? It makes sense for other reason - your traction may fail, but air is always there.

Edited by - Balor on 12/09/2019 01:00:29

harv
recumbent enthusiast

429 Posts

Posted - 12/09/2019 :  15:04:53  Show Profile  Reply with Quote
IIRC Craig Breedlove had a rudder in his engine exhaust, but when his engine shut down, he had no steerage and went into a lake at the salt flats and almost drowned. Wind direction will have an effect of a rudder. Head wind would make it more effective and a tail wind, less.
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warren
human power expert

USA
6560 Posts

Posted - 12/09/2019 :  15:29:22  Show Profile  Visit warren's Homepage  Reply with Quote
Also remember that the more exposed side area that your vehicle has, the more likely you are to get blown into traffic or off the road.
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/10/2019 :  01:00:59  Show Profile  Reply with Quote
Well, that makes sense, but lots of lateral area is inevitable for a streamlined vehicle, and I've seen pictures of streamliners actually adding 'tail fin stabilizers' (rudderless), as I understand to shift CP back for better control during wind gusts, even at expense of overall lateral area (wind trying to topple you is bad enough, but when it tries to actually steer you - does not seem fun)... not sure it is required on an LWB liner though, it's CP seems balanced between wheels (though weight distribution isn't). Obviously, it will not be a huge rudder too, Stuart's 'tailfin' seems a bit of an overkill.

I've been deeply impressed by this article:
https://www.motorcyclespecs.co.za/model/yamaha/yamaha_morpho_ii.htm

Robert Horn has abrasive personality to be sure, but I'm also sure he can be trusted with his reports of better control on his LWB motobent with all wheel steer.
I'm not sure I actually *need* this because I do not intend to be competitive in racing, but seems interesting to try. Obviously, I do not intend this to *replace* my steering, and like Rohorn's bent was perfectly rideable w/o RWS, so would my bent: effect should be subtle, but positive... and if tailwind will largely nullify it, that's ok... obviously, it should be set conservatively lest a head wind will switch me into 'rear steering' mode which does not sound good!
I'll likely simply adapt an RC servo solution that could easily be removed in case it would not work, and leave the 'rudder' as 'visibility aid'.
Will not be a high priority project though, I need to complete my leaning quad first (and make sure that leaning concept work, otherwise rudder will be useless).

Edited by - Balor on 12/10/2019 01:07:28
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/10/2019 :  03:00:20  Show Profile  Reply with Quote
P.S.
In case of fully Pulse-like streamliner with actual wings and multitrack dynamics, adding ailerons to produce a 'counter-roll' moment should negate *some* body roll in turns, at the cost of air resistance of course (according to lift/drag ratio). Given that lift to drag is 20 at the best of circumstances, one cannot expect to add much, and wings will have to be really long to provide enough momentum, further adding to drag (not to mention road space)...

Hmm, if you think about it, it does not only provide resistance to body roll, but actually provide active tipover resistance at high speeds, so in theory it should allow narrower track/higher CG... but, again, at the cost of air drag and given that your wings are wide enough to begin with.

MAY be viable in special circumstances when dealing with fixed track width and twisty track, but simply lowering CG as much as possible will work as well... when combined with suspension it gets more viable though.

Edited by - Balor on 12/10/2019 05:00:16
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/10/2019 :  05:36:33  Show Profile  Reply with Quote
Even more interesting idea is to utilise existing body roll to provide "ekranoplan" effect on the tilted wing.

https://en.wikipedia.org/wiki/Ground-effect_vehicle

It seems to be much more efficient lift-to-drag wise, and if you locate your 'wings' just high enough (and have them wide enough) it should give this effect (by suspension body roll) passively,
I wonder if Pulse also worked like that...
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warren
human power expert

USA
6560 Posts

Posted - 12/10/2019 :  09:34:03  Show Profile  Visit warren's Homepage  Reply with Quote
Fins were mostly added to correct issues with CP being too far forward. A well thought out design should negate the need for these band-aids.
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Speedy
recumbent guru

USA
950 Posts

Posted - 12/10/2019 :  12:54:32  Show Profile  Reply with Quote
Most motorcycles have two wheel steering by the skilled application of brakes and throttle.
Understanding this concept comes from trying an ABS equipped bike for the first time.
Of the 50+ motorcycles I've owned only two have has ABS. Not a feature I have adapted to very well.

Edited by - Speedy on 12/10/2019 12:59:05
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/10/2019 :  13:07:54  Show Profile  Reply with Quote
A well-thought out design for a *practical* faired HPV has much more constraints than BM streamliner where only speed is paramount.
Admittedly, minimising steering reaction time is likely also a feature most useful for racing, but we'll see. If something helps racing by generally improving hanlding, it will help for non-racing purposes as well, otherwise I'm quite willing to sacrifice speed for handling and safety, provided it will not nullify fairing benefits (which is all too possible...)
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/10/2019 :  13:18:27  Show Profile  Reply with Quote
quote:
Originally posted by Speedy

Most motorcycles have two wheel steering by the skilled application of brakes and throttle.
Understanding this concept comes from trying an ABS equipped bike for the first time.
Of the 50+ motorcycles I've owned only two have has ABS. Not a feature I have adapted to very well.



Hah, 'skilled application' and I don't mix well. My own foray into bent design started exactly because solutions that work for a lot of people don't work for me! I cannot say for a lack of trying - I'm way above 10k miles into bents, which is not particularly impressive to be fair, but I am trying not to delude myself about my strengths and weaknesses.
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alevand
human power expert

USA
3726 Posts

Posted - 12/13/2019 :  16:25:57  Show Profile  Visit alevand's Homepage  Reply with Quote
May be hard to do in practice, as both hands are on the handle bars and feet on the pedals in windy conditions. I think it would just complicate things. It may be good for sailing.

C:
Tony Levand
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/14/2019 :  02:47:28  Show Profile  Reply with Quote
quote:
Originally posted by alevand

May be hard to do in practice, as both hands are on the handle bars and feet on the pedals in windy conditions. I think it would just complicate things. It may be good for sailing.

C:
Tony Levand



Basically, add a potentiometer to the steering and steer the rudder accordingly - will obviously take some experimenting to get ratio right.
And yea, it might very well just complicate things w/o significant benefit, but it would be interesting to try it out.
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alevand
human power expert

USA
3726 Posts

Posted - 12/14/2019 :  06:48:21  Show Profile  Visit alevand's Homepage  Reply with Quote
Ailerons may be better in controlling roll than rudder, though one may be in the slip stream, unless mounted higher up or forward. Yous need some type if inertial sensor, processors and actuators that could compensate for the gusty conditions (auto pilot).

C:
Tony Levand

Edited by - alevand on 12/14/2019 06:57:14
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/14/2019 :  13:09:34  Show Profile  Reply with Quote
Hmm, ailerons on a 'tail fin stabilizer' (instead of elevator)?

That might work, though will provide less roll moment that on wings, obviously (but wings are unviable unless multitrack, and then you don't need this stuff except for high-speed twisty descends to compensate for body roll... 'airbrake' function will come in handy too! Otherwise - not so much).

Using control surfaces to battle wing gusts/truck suck is interesting! Cheap arduino IMU should be able to detect sudden roll moments not caused by steering (provided you have that potentiometer and the system knows whether you are actually steering or not) and be programmed to react accordingly.

I think it should be particularly effective against truck suck exactly because of 'air ram' effect that will make control surfaces more effective as well due to greatly increased airspeed.

IN FACT, it might be possible to make this system semi-automatic by mounting air pressure modules on the sides and having it auto-bank into region of higher pressure, compensating for lateral wind/truck suck only and disregarding inertial data that might be pretty tricky to parse for a bike given potholes, etc.
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Balor
recumbent guru

Russia
991 Posts

Posted - 12/14/2019 :  15:22:51  Show Profile  Reply with Quote
Hmm, when it comes to truck suck in particular, it is possible to make entirely passive system - add lift-generating wings (may be relatively stubby) to the sides, with large lift to drag coefficient to prevent them from adding too much drag.
Truck suck is due to Venturi effect of air speed getting greater as it is forced into a relatively small opening between you and overtaking vehicle, accelerated and the side facing the truck getting in drop in relative pressure compared to freestream velocity due to Bernulli principle.
So we get 'sucked' towards the truck and hence develop a roll moment into the truck depending on your CP height (and steering moment depending on location of CP along the wheelbase).
Now, since the wing in Venturi effect will also develop more lift compared to wing in freestream, it should provide a counter-roll moment, and if you balance wing lift with lateral area, the arrangement might cancel this effect out completely (though this is highly unlikely).
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Balor
recumbent guru

Russia
991 Posts

Posted - 01/20/2020 :  07:24:23  Show Profile  Reply with Quote
I think I will go with a high-mounted rudder will provide the most 'anti-roll' moment for least drag and highest visibility boost.
In theore, even a very dumb system that simply tries to correct for any uncompensated (as in - not into a turn) lean should be enough, provided not too powerful to overpower my own efforts to lean into turns (and into the wind).

At first, I'll make it electronically using a servo and arduino-controlled accelerometer. If that works (after all, I need something that HELPS me to control for side winds, briging it to manageable levels like on an unfaired bike for instance, not a fly-by-wire full autopilot) - I may recreate it with a mecanical system using a pendulum.

If it does not, I'll keep the electronics and start adding more sensors - wind speed sensor (with Pitot tube), air direction sensor (basically a weatherwane), steering direction sensor and maybe even air pressure sensors like I've said above.
All of above cost only a few bucks, only good waterproof air pressure sensors are more expencive.
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