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View Full Version : a raaaid like question... :)

GAU-8
07-02-2006, 12:04 AM
I confused myself in the pea sized noggin, going over thrust/weight ratios. and somehow i came up with this. not that it would/could/did work..but something i might do for fun.

toy rubber band powered aircraft lose power after it uwinds its stored energy. then it glides back down.

what "if" (no idea how plausible..it may be??) design a motor to just WIND the rubber band while the plane was in flight? whether it was a REAL AIRCRAFT, or a toy..would the basic principle work on SOME sort of scale? my thing..

. you would have to have the winding motor be timed for maximum thrust. if it continously overwinds, the band will snap. factoring in stretching rates/overwinding you would have the motor programmed (doesnt matter how..) to turn off intermittenly so to not pop the banded powerb source. or will it plainly not work on ANY LEVEL, stictly because if a motor is spinning a loose object, and that loose object will always be at the same RPM as teh item trying to spin it?

it doenst have to be strictly limited to a toy. just wondering the basic principle of my idea had any kind of working, if not worth it merit.

GAU-8
07-02-2006, 12:04 AM
I confused myself in the pea sized noggin, going over thrust/weight ratios. and somehow i came up with this. not that it would/could/did work..but something i might do for fun.

toy rubber band powered aircraft lose power after it uwinds its stored energy. then it glides back down.

what "if" (no idea how plausible..it may be??) design a motor to just WIND the rubber band while the plane was in flight? whether it was a REAL AIRCRAFT, or a toy..would the basic principle work on SOME sort of scale? my thing..

. you would have to have the winding motor be timed for maximum thrust. if it continously overwinds, the band will snap. factoring in stretching rates/overwinding you would have the motor programmed (doesnt matter how..) to turn off intermittenly so to not pop the banded powerb source. or will it plainly not work on ANY LEVEL, stictly because if a motor is spinning a loose object, and that loose object will always be at the same RPM as teh item trying to spin it?

it doenst have to be strictly limited to a toy. just wondering the basic principle of my idea had any kind of working, if not worth it merit.

diomedes33
07-02-2006, 12:27 AM
Isn't this the same principle that govern a diesel electric? Diesel generators (your motor) charge batteries , batteries (rubber band) power electric motors that drive props wheels, etc ...

GAU-8
07-02-2006, 12:58 AM
i dont know. http://forums.ubi.com/images/smilies/35.gif

lol

for clarity what i am trying to say,

could it be possible, if the rubber band was long enough you could "spool up" the rubber band to tight knots, let it unwind to your set RPM. then at a determined time, the motor knows when to kick in before losing that particular set speed. and of course the motor would change its RPM according to the speed you set/wanted.

it sounds redundant to have two motors for sure. but, for efficienty of flight in genral, is it something that could work? and if so, could it be that efficient? im thinking of something like a human powerd aircraft, very lightweight.something like that criteria.

but im not limiting it to a "pure rubber" based type band. it could by hybrid stuff in the realworld. my concern is you cant truely "what if" ideas...and to get a correct answer, if your using real material but in a remove "X" principal/equasion (no offence raaaid)

so if some of you deal with this math stuff, and your ideals were met to make it potentially work...depending on the material, length and property of band, type of motor, and real world mathematics... could you it work in theory?

dont worry its not a project, im not trying to have you guys do the work, and i come out with a new toy you developed. http://forums.ubi.com/images/smilies/88.gif

im just science minded..but lacking in the science http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

Taylortony
07-02-2006, 01:34 AM
weight is a factor, also why have to sources of thrust, you would simply remove the band and have the motor drive the prop direct........

Remember the energy you put into twisting the band is always going to be more than what you get out of the band power wise, otherwise you would have produced the mythical perpetual energy, the dream of man for many a year, where you have a source of energy that is greater than that put in to produce it.......

what you would ideally want is a way for the airflow to perhaps by the prop to retwist the band slightly after it runs out of energy, this will not attain your unattainable, but will sustain your flight time for just a little longer

GAU-8
07-03-2006, 10:56 PM
thats the thing, the rubber band would not be allowed to completely unwind. the basic idea is that the motor wouldnt have to stay on constantly like a regular A/C engine. it would be something more or less as......... i dunno.. i think weird sh@t at times..

carry on http://forums.ubi.com/images/smilies/35.gif

WB_Outlaw
07-03-2006, 11:10 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Taylortony:
what you would ideally want is a way for the airflow to perhaps by the prop to retwist the band slightly after it runs out of energy, this will not attain your unattainable, but will sustain your flight time for just a little longer </div></BLOCKQUOTE>

This wouldn't increase your flight time. It would simply remove some kinetic energy from the aircraft and store some of it in the rubber band (the rest would be lost as heat). It would allow you to use that energy at a more opportune time such as landing but you wouldn't be able to extend your flight time. For maximum flight time, you need to remove the entire power system entirely once it's delivered all the energy it can. That's why high end rubber band powered models have props that fold backwards under aerodynamic forces and lock in place once the rubber band is done.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by diomedes33:
Isn't this the same principle that govern a diesel electric? Diesel generators (your motor) charge batteries , batteries (rubber band) power electric motors that drive props wheels, etc ... </div></BLOCKQUOTE>

AFAIK, diesel electric locomotives are driven by the generators directly, there are no batteries. Diesel electric subs are driven by the diesel directly when possible and only switch to batteries when sufficient air is not available to run the diesels.

GAU,
Don't take this as gospel but I can't think of any situation where any type of regenerative/supplemental power can be applied to a human powered aircraft b/c the weight restrictions are just too tight. According to a study I read, a "first class" athelete can only generate a sustained 0.4 horsepower for an eight hour period. Increasing output to 0.5 horsepower results in only 40 minutes of power before exhaustion. I believe that adding any type of supplemental power system would make the aircraft so heavy that no human could power it for any amount of time. Thus, your supplemental power is now the human, not the power system you added.

--Outlaw.

GAU-8
07-04-2006, 04:41 AM
no problem outlaw http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

it was just one of those thoughts that went to an idea..and that lead to something else which lead to a twisted.."ok there is no real purpose..but it could be done..couldnt it?" thought http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif