Alt-BEAM Archive
Message #10583
To: beam@sgiblab.sgi.com
From: Dave Hrynkiw dave@solarbotics.com
Date: Mon, 21 Feb 2000 14:13:35 -0700
Subject: [alt-beam] Re: Torque and propellers
At 01:56 AM 2/21/00 , Timothy Flytch wrote:
>I'll answer your little fame.... one more time...
>Try opening up a history book... look up the "FockeAchgelis Fa 61" it was
>the first true helicopter... It had two side by side rotors that were NOT
>counter rotating... Anna loved it, even flew it inside a gym!
Ummm.. Not according to this little quote:
"Two lateral pylons supported gear boxes on which the three-bladed rotor
hubs were fixed, rotating in opposite directions."
http://helicopter.virtualave.net/fw61.htm
http://www.rotor.com/rotor/Fall97/Octrhtml/historic.htm
>Then try the "H21C FLYING BANANA " It was a tandem (inline) production
>helicopter that did not have counter rotating rotors either... Later
>models were changed to counter rotation to shorten the fuselage by over
>lapping the rotors...
Hmmm. According to a blurb at
http://www-acala1.ria.army.mil/LC/cs/csa/aahist.htm
the military version Shawnee... "The Shawnee had two tandem fully-articulated
three-bladed counter-rotating rotors. The CH-21C was powered by one
Curtis-Wright R1820-103 Cyclone supercharged 1250 hp piston engine. The
CH-21 had a speed of 128 mph (110 knots)."
If you guys REALLY want to see it in action, I've just built a model with
the RPM and props to illustrate the point. Let me know, and I'll
shoot the video, digitize it, reduce it, and post it on the website.
The model has 2 motors on a beam, suspended by the midpoint. Pops have been
tweaked to give NO THRUST (ie: blades in the vertical, not for generating
thrust). Motors running BOTH CW makes the beam rotate CCW. Both motors CCW,
makes beam go CW. Motors running counter-rotation, NO beam rotation.
>While you are in the library grab a book on gyro copters... you will see
>that there is NO full size twin rotor gyros, only models use them...
That's because no power is applied to the rotors on a Gyrocopter, other
than to get them spun up to flying speed, but they DO NOT provide active
lift from power transferred directly from any engine. The lift from a Gyro
comes from the forward velocity of the aircraft, which passes air through
the rotors from underneath, like a giant pin-wheel.
>Try this... Take a paper plate and punch a hole through the middle ... put
>a side of the plate ... you will notice that the plate dose not dip were
>you blow but about 90' later in it's spin ... That is gyroscopic precession...
Explained well here:
http://www.copters.com/aero/gyro.html
I was using the "Top" analogy because it's the most obvious example people
will recognize. The little "wobble" I explained is due to gravity pulling
down more on one side of the top, which in turn makes it "wobble" around in
a circle. For those who want to know, take a boo at the above link, and
imagine gravity pulling down on one point. The resultant force is about 90
degrees further around the top.
>I just have to ask what is a "crap-load" anyway??? How dose that equate to
>Lb/Ft???
Huge props: Crap-load. Small props: peanut-load. Gotta be open to more
descriptive terms! ;>
>I'll attach a couple of pictures for you ...
Came thru, but with no extension. What type of pics?
Regards,
Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com
10584 Mon, 21 Feb 2000 16:25:22 EST [alt-beam] Re: MPJA geared motors beam@sgiblab.sgi.com BUDSCOTT@aol.com really!? that's interesting, but since i'm such a stubborn bugger, i'll try
anyways. why would that be that they are soo inefficient, never heard that
bout worm gears before. i'm gonna have to breadboard the circuit anyways so
i'll check them then, i do have backups that are old old display motors that
my grandfather used in his liquor store (boy was that back in the day!).
anywho i'll have the rest of the misc. parts today, resistors and capacitors
ya know that crap, and probably have it all bread boarded tommorow, now all i
need is a good power supply any suggestions? thanks a ton!
-Spencer
10585 Mon, 21 Feb 2000 16:30:45 EST [alt-beam] Re: Breadboarded solenoids beam@sgiblab.sgi.com BUDSCOTT@aol.com yup, that's my suspision too, under saturated base. i think i'm just gonna
need to find better solenoids, cause otherwise it would be unbearably slow
and way too inefficient. i kinda wanted to experiment with the mechanics of
using something other than motors, just so people don't get bored, could be
use for a very strange bicore app. if you used a master/slave 2 bicore
thingy, i think (from my understanding of the charecteristics of a bicore)
you could hook up the solenoids using some sort of diode system so four
solenoids could be triggered like the legs on a walker, ohwell just a
thought! thx!!!
-Spencer
10586 Mon, 21 Feb 2000 16:37:21 EST [alt-beam] Re: More solenoid junk beam@sgiblab.sgi.com BUDSCOTT@aol.com that's pretty cool. perhaps i could go to a camera store and ask round about
'em. if you could send me pics that'd be cool, i'd like to keep the stuff as
light as possible other wise it would hinder its ability to hop. thanks for
the input!
-Spencer
10587 Mon, 21 Feb 2000 16:39:20 EST [alt-beam] Re: MPJA geared motors beam@sgiblab.sgi.com BUDSCOTT@aol.com mine don't have plastic casing actually. there pretty hardcore surplus junk.
looks almost like they're a "removed from equipment" item. oh well, thanks!
-Spencer
10588 Mon, 21 Feb 2000 14:05:12 -0800 [alt-beam] sonoma county california alt-beam@eGroups.com "Paul Stimson" any beamers near santa rosa?
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