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Author Topic: Science in pics  (Read 24197 times)

Online Dave_Trible

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Science in pics
« on: October 28, 2013, 09:09:27 PM »
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Online Dave_Trible

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Re: Science in pics
« Reply #1 on: October 28, 2013, 09:09:57 PM »
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Online Dave_Trible

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Re: Science in pics
« Reply #2 on: October 28, 2013, 09:10:28 PM »
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Re: Science in pics
« Reply #3 on: October 28, 2013, 09:10:59 PM »
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Re: Science in pics
« Reply #4 on: October 28, 2013, 09:11:38 PM »
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Re: Science in pics
« Reply #5 on: October 28, 2013, 09:12:12 PM »
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Online Brett Buck

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Re: Science in pics
« Reply #6 on: October 28, 2013, 09:17:41 PM »
Oh, you're going on a list for sure, now!

Offline Tim Wescott

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Re: Science in pics
« Reply #7 on: October 28, 2013, 11:07:57 PM »
People are still going to think that moving the bellcrank without moving the leadout guides is going to affect stability somehow.  When it's all magic, it's all -- magic.
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Online Howard Rush

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Re: Science in pics
« Reply #8 on: October 28, 2013, 11:25:04 PM »
We can't see what's going on with the tail of that airplane.  It's beyond the left edge of the picture.  We'll never know the truth.  There's no way to find out the truth.
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Offline phil c

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Re: Science in pics
« Reply #9 on: October 29, 2013, 09:24:38 AM »
Nice Dave.  A picture is always worth a thousand words, even more than doing it yourself.
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Offline BillLee

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Re: Science in pics
« Reply #10 on: October 29, 2013, 09:47:18 AM »
People are still going to think that moving the bellcrank without moving the leadout guides is going to affect stability somehow.  When it's all magic, it's all -- magic.

No, Tim, not magic. It's "STUNT PHYSICS"!!!  LL~ LL~ LL~
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Offline Doug Moon

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Re: Science in pics
« Reply #11 on: October 29, 2013, 02:44:57 PM »
What I find most impressive about this is the motor mounting system!

I am trying this very technique myself as of a few days ago....see below....
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Offline Tim Wescott

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Re: Science in pics
« Reply #12 on: October 29, 2013, 02:48:16 PM »
People are still going to think that moving the bellcrank without moving the leadout guides is going to affect stability somehow.  When it's all magic, it's all -- magic.
Cynicism aside, that's a great series of pictures, and something that I've felt like putting together myself for the edification of the troops.
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Online Dave_Trible

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Re: Science in pics
« Reply #13 on: October 29, 2013, 03:14:57 PM »
What I find most impressive about this is the motor mounting system!

I am trying this very technique myself as of a few days ago....see below....
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Online Howard Rush

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Re: Science in pics
« Reply #14 on: October 29, 2013, 03:51:36 PM »
Cynicism aside, that's a great series of pictures, and something that I've felt like putting together myself for the edification of the troops.

Check out http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=360459&mesg_id=360459&listing_type=search#360815 .  Start with post #12.
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Offline Doug Moon

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Re: Science in pics
« Reply #15 on: October 29, 2013, 08:52:25 PM »
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Offline Igor Burger

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Re: Science in pics
« Reply #16 on: October 30, 2013, 12:41:08 AM »
perfect video Doug  LL~ it proofs that:

1/ combat cannot fly straight  VD~

2/ that guy who invented PID regulator was right that P regulation is not enough  H^^

3/ people do not act rationaly in stress, so many times he almost broke his legs and still did not find that turning that chair 180 degrees will make it much easier to jump back safely  n~

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Re: Science in pics
« Reply #18 on: October 30, 2013, 07:29:41 AM »
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you forgot to add a 20 knot crosswind .  S?P

Offline Tim Wescott

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Re: Science in pics
« Reply #19 on: October 30, 2013, 09:16:39 AM »
2/ that guy who invented PID regulator was right that P regulation is not enough  H^^

I was trying to figure out how to add some damping to that classic exponentially increasing sine wave, but couldn't figure out an easy way to do it mechanically.  Perhaps just start with a calmer airplane?

3/ people do not act rationaly in stress, so many times he almost broke his legs and still did not find that turning that chair 180 degrees will make it much easier to jump back safely  n~

Or just stand stock straight and let the airplane whiz by, inches from his shirt!
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Offline Igor Burger

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Re: Science in pics
« Reply #20 on: October 30, 2013, 09:29:14 AM »
couldn't figure out an easy way to do it mechanically

yes, not so easy to integrate and derivate with mechanic components ... someone said we can use electronic and servos in stuters? :- )))

Online Brett Buck

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Re: Science in pics
« Reply #21 on: October 30, 2013, 12:34:54 PM »
this was also not bad :- )))

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=127959&mesg_id=127959&page=&topic_page=5

   Yes, that does bring back many fond memories. I seem to recall that this was the thread where it was proclaimed that understanding the mechanics of a leadout guide was above "that guys head", where "that guy" = Paul Walker. You couldn't make this stuff up.

     Brett

Offline Igor Burger

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Re: Science in pics
« Reply #22 on: October 30, 2013, 01:18:42 PM »
I had on mind especially some pictures from that thread ...  n~





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Re: Science in pics
« Reply #23 on: October 30, 2013, 01:38:34 PM »
I had on mind especially some pictures from that thread ...  n~






Igor
May have to factor in "wall friction " in to your formulas on this one ;-)

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Offline Igor Burger

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Re: Science in pics
« Reply #24 on: October 30, 2013, 01:43:57 PM »
or tail weight :- ))))

Offline Tim Wescott

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Re: Science in pics
« Reply #25 on: October 30, 2013, 02:03:25 PM »
I think this thread is teaching us something about science.

I don't think it's about leadouts -- I think it's about doing your own @#$% experiments, particularly when you're surrounded by jokers.
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Offline Igor Burger

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Re: Science in pics
« Reply #26 on: October 30, 2013, 02:10:50 PM »
hopefully those @#$% experiments will provocate non believers to do non @#$% experiments  ;D

Online Howard Rush

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Re: Science in pics
« Reply #27 on: October 30, 2013, 04:49:41 PM »
That was my motivation. 
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Online Brett Buck

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Re: Science in pics
« Reply #28 on: October 30, 2013, 09:08:31 PM »
That was my motivation. 

   Those windmills are not going to tilt at themselves!   A noble goal, nonetheless.

    Brett

   

Offline Serge_Krauss

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Re: Science in pics
« Reply #29 on: October 30, 2013, 10:40:59 PM »
A-r-r-r-r-gh...

I'm not sure how wise it is to keep posting the jokes, when the people who don't understand the main idea ALSO haven't even figured out that sometimes they're criticizing things no one has even said. I know the main idea behind kicking rational scientific/engineering thought out here to the south forty was probably to bury it unread by the true believers, but this unexplained humor just sits here in cyberspace ready to confound more passers by. Yeah, it's entertaining, but...

Online Howard Rush

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Re: Science in pics
« Reply #30 on: October 31, 2013, 12:38:16 AM »
A-r-r-r-r-gh...

I'm not sure how wise it is to keep posting the jokes, when the people who don't understand the main idea ALSO haven't even figured out that sometimes they're criticizing things no one has even said. I know the main idea behind kicking rational scientific/engineering thought out here to the south forty was probably to bury it unread by the true believers, but this unexplained humor just sits here in cyberspace ready to confound more passers by. Yeah, it's entertaining, but...


I did the original one out of disgust with people arguing for hours over something they could have determined for themselves with a simple experiment.  It probably had three effects: 1) to make fun of people who believe something bogus with no experimental evidence even after having the physics explained to them, 2) to amuse those who got the joke, and 3) to cause people to do the experiment themselves.  I think all three are good, but as we've previously discussed, I am not as nice a person as you.

One thing I hadn't counted on is a person not accepting that one can use gravity as a surrogate for centripetal acceleration.  We do, but I see now that it's not obvious to everybody.  It's probably something you went through every semester.  I guess you could either try to prove that equivalency to the doubter, or he could do a somewhat more elaborate experiment with a control line airplane with a relocateable bellcrank.
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Offline Trostle

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Re: Science in pics
« Reply #31 on: October 31, 2013, 02:04:43 PM »
Commendations to Dave Trible for going to the trouble to show what has been explained countless times before as shown by the several references to other threads/forums over the years.

The Bill Netzeband column from American Modeler, Oct 62, has often been quoted where he explains tht the CG will always fall in line with the center of the line lead-out spacing.  In that column, he provided photos of a simple test device to show what he clearly explained.  It is interestings to observe those who cannot accept this physical fact.  The photos from that article over 51 years ago.

Keith

Offline Trostle

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Re: Science in pics
« Reply #32 on: October 31, 2013, 02:51:13 PM »
I guess you could either try to prove that equivalency to the doubter, or he could do a somewhat more elaborate experiment with a control line airplane with a relocateable bellcrank.

And that has been done.  Reference Walter Williamson's article in American Modeler, Jul 66, Case of the Wandering Bellcrank with photos.  His test plane was an all wood trainer with a sheet-covered crutch.  The controls were all external where he could place the bellcrank in nine different places along the length of the fuselage, from 6 inches in front of the CG to 10 inches in back of the CG.  The leadouts at the wing tip could be moved to different positioned, some in front of the CG, some in back of the CG.  His tests showed that what matters is where the leadouts are located relative to the CG, the bellcrank position had no affect on the way the airplane flew.

This test plane maintained the bellcrank essentially in the same vertical plane.  However, the position of the bellcrank relative to the position of the vertical CG will have no effect on the way the airplane flies, just as its longitudinal position relative to the CG will have no effect.  A good example to prove this is the bellcrank position on a semi-scale stunt ship that uses a noticeable amount of dihedral, i.e. the Rabe super semi scale stunt ships like his Mustangs, Bearcats, and Sea Fury's.  The bellcrank in those models are near the bottom of the fuselage, well below the vertical CG.  Yet, the leadouts are carefully positioned near the vertical CG through the dihedralled tips.  (Al recognized the need to position the leadout near the CG postion, both laterally and vertically when he started those creations of his in the late 60's and has written about it extensively in his stunt column of many years ago and his many articles and posts since.)

Some may wish to discount the writings and published demonstations of Bill Netzband, but who can differ with the real and proven applications and successes of Al Rabe including two National Stunt Championships and one second place at the World Championships?

And through all of this, it is still logical to position the bellcrank where there is room to do so, where it is structuraly sound, and to have it positioned to minimize flex and wear of the leadouts through the leadout guides and that those guides are optimally positioned with regard to the CG.

KT
« Last Edit: October 31, 2013, 04:56:33 PM by Trostle »

Offline RC Storick

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Re: Science in pics
« Reply #33 on: October 31, 2013, 04:22:31 PM »
I see the Netzaban bullet is pulled again. What about centrifugal force?  What about inertia when changing attitudes? These tests mean nothing! Just put the bell crank anywhere you want.

I get a kick out of some people. Funny how all I ever hear about is CG and never the centrifugal force imposed. Must have come from a book in the 1960 TYS.

If you look at this picture

And imagine a engine on the front of it flying at 60 MPH circling to the left. Do you not think that all 3 points will want to line up? Do you not think that if everything was moved closer inline with the concentrated weight (engine) If would have less effect while turning left. Let alone up and down? I guess those hundreds of planes I have experimented with must all been wasted experiments.
« Last Edit: October 31, 2013, 05:29:28 PM by Robert Storick »
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Re: Science in pics
« Reply #34 on: October 31, 2013, 06:28:16 PM »
Think I'll try this just once.  If you accelerate the airplane and create centrifugal force to say 10Gs,  yes that is 10Gs trying to force the nose out.  I think what is being forgotten is that the tail is also getting the exact same 10Gs pushing the tail out EXACTLY the same, perfectly counteracting each other about your tether point so the relationship doesn't change no matter how fast or how heavy.  That logic would then have to say that the faster you fly the airplane the more nose heavy it gets.  Don't think so. 

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Offline RC Storick

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Re: Science in pics
« Reply #35 on: October 31, 2013, 07:15:31 PM »
That would be true if you had a sinker in the tail of course I don't have a clue. Like I said I wasted all my 45 years building (at least 5 a year) different configurations and didn't learn a thing.

There is a sweet spot for everything and when you end up finding it you know you have it right Usually with in the first 5 laps.Its all about weight anyway. If some one doesn't think so next time you buy a engine or wood don't ask what it weighs just buy it and use it.
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Offline Serge_Krauss

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Re: Science in pics
« Reply #36 on: October 31, 2013, 09:25:11 PM »
"Do you not think that all 3 points will want to line up?"

No.

The handle and center of mass (c.g.) will line up radially, regardless of where the bellcrank is, and the leadout exit positions will determine the yaw angle of the plane relative to it's flight path.  Keith pointed out that Al Rabe's planes, among many others with dihedral, prove this every time they fly. That's also why you have adjustable leadouts, and moving them does re-position the bellcrank along with the rest of the plane in flight. This is required by Newton's First and Third laws of motion and requires no math or "formulas" to verify. If it were wrong, then the entire structure of modern science and technology is wrong, and what we've accomplished just hasn't happened. Structural, wear, and weight distribution advantages of particular bellcrank locations have been noted ad infinitim.

Really!!!!  You need to READ these posts! Everything you have just said was covered thoroughly by Howard, Keith, and me in the last few posts:

1) The picture was made as a joke.

2) You've criticized things that were not claimed; no one questioned that things turn better with smaller polar moments of inertia.

3) Howard just again discussing the equivalence of gravitational and centrifugal forces and what to do, if you doubt it: just do the actual experiment with CL planes flying in a circle. You will see as others have demonstrated, that the bellcrank does not align itself between the c.g. and the handle, nor must it lie along the flight circle radius. Line drag will be shown to be the only difference between circular flight and simply hanging models by their leadouts. Einstein even based some of his explanations of the general theory of relativity on equivalence of gravitational and centrifugal forces. The very nontrivial "formula" E = mc2 is the result of that reasoning.

4) Bill is far from the only person to show that bellcranks do not have to line up. Some, as shown have done these experiments in flight and many others, including me, have done the equivalent simple demonstrations that dictate the "no" answer above. Personalities are irrelevant here.
 
No one has questioned your being a skillful builder of marvelous planes, which may fly quite well, but denial of basic principles upon which all science and technology is based does not explain whatever fine flying qualities your planes may have. Any plane built well and accurately to reasonable dimensions will fly well. That it will fly well does not invalidate basic principles not understood by its builder. (Edited to add the word 'not' in the last sentence)


« Last Edit: November 01, 2013, 08:39:39 PM by Serge_Krauss »

Offline RC Storick

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Re: Science in pics
« Reply #37 on: October 31, 2013, 09:42:22 PM »
As I have said before do as you wish.
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Online Brett Buck

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Re: Science in pics
« Reply #38 on: October 31, 2013, 09:49:02 PM »
I did the original one out of disgust with people arguing for hours over something they could have determined for themselves with a simple experiment. 

  I gave up after an two-week discussion about what power actually means with multiple self-styled "engine experts", which followed on the heels of the absurd  thread where someone nobody ever heard of was lecturing 3-4 different national champions about how ignorant they were and that they didn't understand how to trim airplanes. In the "power" thread I actually did real experiments with calibrated dynos and thrust scales that showed exactly what was predicted, and they still didn't "believe" it.

    Brett

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Re: Science in pics
« Reply #39 on: October 31, 2013, 11:24:07 PM »
was that a water dyno or a friction dyno? Or just a fish scale??

 The idea was later used by James Watt to help market his improved steam engine. He had previously agreed to take royalties of one third of the savings in coal from the older Newcomen steam engines.[7] This royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute). The wheel was 12 feet in radius; therefore, the horse travelled 2.4 × 2π × 12 feet in one minute. Watt judged that the horse could pull with a force of 180 pounds. So:
P = \frac{W}{t} = \frac{Fd}{t} = \frac{(180 \text{ lbf})(2.4 \times 2 \pi \times 12 \text{ ft})}{1 \text{ min}} = 32,572 \ \frac{\text{ft} \cdot \text{lbf}}{\text{min}}.


This was rounded to an even 33,000 ft·lbf/min.[8]

Corn bread are square and pie are round
« Last Edit: October 31, 2013, 11:49:48 PM by Robert Storick »
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Online Brett Buck

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Re: Science in pics
« Reply #40 on: November 01, 2013, 12:40:42 AM »
was that a water dyno or a friction dyno? Or just a fish scale??

 The idea was later used by James Watt to help market his improved steam engine. He had previously agreed to take royalties of one third of the savings in coal from the older Newcomen steam engines.[7] This royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute). The wheel was 12 feet in radius; therefore, the horse travelled 2.4 × 2π × 12 feet in one minute. Watt judged that the horse could pull with a force of 180 pounds. So:
P = \frac{W}{t} = \frac{Fd}{t} = \frac{(180 \text{ lbf})(2.4 \times 2 \pi \times 12 \text{ ft})}{1 \text{ min}} = 32,572 \ \frac{\text{ft} \cdot \text{lbf}}{\text{min}}.


This was rounded to an even 33,000 ft·lbf/min.[8]

Corn bread are square and pie are round


   It was an air-brake dynomometer which measured torque and was calibrated before use. The thrust stand that was also calibrated by known weights. I used a TNC Tachometer that is good to 5 ppm at 100,000 rpm

     I am familiar with the notion of horsepower. And in any case, the difference between the two cases we investigated was a *factor of 2.5*, which means that a fine calibration was absolutely unnecessary to resolve the question at hand.

     Conceptually the power is a measure of the rate at which work is done which leads to some interesting effects that would surprise the unwary.  Work is the force x distance (horse lifting 550 lbs one foot, 550 ft-lbs of work) or in rotational terms the torque x the number of revolutions. Since it's the rate of work, it's the derivative of the work with respect to time, hence force x velocity (horse lifting 550 lbs by one foot in one second, 550 ft-lbs/second - same as 33,000 ft-lb/minute)  or torque x the rpm.

Here's a horsepower calculation quiz question for the assembled group. A Saturn 1B rocket with a total of 1.5 million lbs of thrust. A launch it weighs 1.3 million lbs.  What is the HP at the instant of release? It burns out after about 1 minute and a half at a velocity of 5000 feet per second and an altitude of 100,000 feet, and weighs 500,000 lbs.  What is the horsepower at the instant of burnout? For sake of argument the thrust is the same in both conditions. 

     Same question except for airplanes. At launch on the ground, an airplane has a weight of 54 oz, a PA65, and a 13-4 3-blade, 10000 RPM, thrust is 4.5 lbs. What is the horsepower being applied to the airframe while being held? Then the airplane is released, and accelerates to a steady 80 feet/second in level flight after 3.5 seconds. At that condition, the drag of the airplane is 2.5 lbs, the engine RPM is 11,000. What is the horsepower being applied to the airframe in level flight?  On the next flight, the prop is repitched to 3.5" and is otherwise the same. The ground launch RPM is now 11,000, the static thrust is now 5.0 lbs, and the airplane accelerates to 80 FPS in 2.5 seconds. What is the horsepower being applied to the airframe now?

    Brett

Offline Tim Wescott

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Re: Science in pics
« Reply #41 on: November 01, 2013, 12:58:37 AM »
Here's a horsepower calculation quiz question for the assembled group. A Saturn 1B rocket with a total of 1.5 million lbs of thrust. A launch it weighs 1.3 million lbs.  What is the HP at the instant of release? It burns out after about 1 minute and a half at a velocity of 5000 feet per second and an altitude of 100,000 feet, and weighs 500,000 lbs.  What is the horsepower at the instant of burnout? For sake of argument the thrust is the same in both conditions. 

Horsepower where?  At the instant of launch the power being transmitted to the exhaust out the nozzle is a function of the mass flow rate and the pressure (and I lack both data and motivation to work it out).  The average power being transmitted to the motionless (on average) rocket frame is exactly zero, and the vibrational power being transmitted to the rocket frame is probably far more than a Shelby Cobra.

The horsepower at burnout is way bigger, but again, I'm too lazy to work all the conversions -- but it's
  (thrust) * (speed) / (silly conversions because you're not using metric).

Same question except for airplanes. At launch on the ground, an airplane has a weight of 54 oz, a PA65, and a 13-4 3-blade, 10000 RPM, thrust is 4.5 lbs. What is the horsepower being applied to the airframe while being held? Then the airplane is released, and accelerates to a steady 80 feet/second in level flight after 3.5 seconds. At that condition, the drag of the airplane is 2.5 lbs, the engine RPM is 11,000. What is the horsepower being applied to the airframe in level flight?  On the next flight, the prop is repitched to 3.5" and is otherwise the same. The ground launch RPM is now 11,000, the static thrust is now 5.0 lbs, and the airplane accelerates to 80 FPS in 2.5 seconds. What is the horsepower being applied to the airframe now?

Again, zero average power on release, with some non-zero vibrational power if someone wants to be a smart-ass.  You're not giving enough data in flight: you're missing the thrust in flight, and simply giving prop pitch, RPM and airspeed does not make up that lack.
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Offline Avaiojet

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Re: Science in pics
« Reply #42 on: November 01, 2013, 06:23:46 AM »
I was taught to place ALL my bellcranks on the CG, told this in the late 50's.  ;D

Fast forward to present day, I still place all my bellcranks on the CG, no matter what I'm told.

With everything that has been said "and proven," and I'm a believer in science, yeah right, then why on earth are "everyone's" leadouts adjustable?

Science? They don't even know where the moon came from.  LL~ LL~ LL~

Bottom line, if you don't mind, I'll have adjustable leadouts and my bellcranks will be on the CG.

Am I doing this wrong?

Charles
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Online Dave_Trible

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Re: Science in pics
« Reply #43 on: November 01, 2013, 07:24:59 AM »
I was taught to place ALL my bellcranks on the CG, told this in the late 50's.  ;D

Fast forward to present day, I still place all my bellcranks on the CG, no matter what I'm told.

With everything that has been said "and proven," and I'm a believer in science, yeah right, then why on earth are "everyone's" leadouts adjustable?

Science? They don't even know where the moon came from.  LL~ LL~ LL~

Bottom line, if you don't mind, I'll have adjustable leadouts and my bellcranks will be on the CG.

Am I doing this wrong?

Charles
Charles, not wrong at all.  Everything will work just perfect.  BUT,  you could have mounted the bellcrank inches forward or behind the CG and you couldn't tell any difference which was the original point of this experiment and thread.  Thinking that bellcrank location is some magic spot is where technical error lies.  It's wasting time worrying about it.  Leadout placement is where the 'secret' trim issue is,  set in conjunction with the CG.  Being able to set it vertically as well as horizontally would be a plus.  It has always been that you might build five airplanes but have one that seems to fly best off the bench.  Assuming that one aspect such as bellcrank placement was the trick can be misleading.  It's usually more that proper alignment and ideal trim settings all came together. Sometimes we never really completely understand why that airplane was special, it just was.  It's not always about the lightest airplane either.  Heavy airplanes aren't good  but something in between will feel much more solid on the lines and penetrate the wind better in a pinch ( like a Nats flight you have to fly NOW and can't choose your weather).
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Offline Trostle

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Re: Science in pics
« Reply #44 on: November 01, 2013, 09:01:50 AM »

 It has always been that you might build five airplanes but have one that seems to fly best off the bench. 

Dave

All of those airpanes that fly "right off the bench" were used up by the mid to late 50's.

Keith

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Re: Science in pics
« Reply #45 on: November 01, 2013, 10:05:02 AM »
Horsepower where?  At the instant of launch the power being transmitted to the exhaust out the nozzle is a function of the mass flow rate and the pressure (and I lack both data and motivation to work it out).  The average power being transmitted to the motionless (on average) rocket frame is exactly zero, and the vibrational power being transmitted to the rocket frame is probably far more than a Shelby Cobra.

The horsepower at burnout is way bigger, but again, I'm too lazy to work all the conversions -- but it's
  (thrust) * (speed) / (silly conversions because you're not using metric).

Again, zero average power on release, with some non-zero vibrational power if someone wants to be a smart-ass.  You're not giving enough data in flight: you're missing the thrust in flight, and simply giving prop pitch, RPM and airspeed does not make up that lack.

   C- for mentioning metric but more or less right. It's the same case as the recent F1 engine revival thread.

     F-- for the airplane case. Level flight HP applied to the airplane, for the first case, is .415 HP (you can convert to PS for your metric fetish on you own time).  Double F- for missing the point.

     Brett

Since no one else seems willing to risk it, the answer for the "inflight hp applied to the airplane" in the second case is also .415 HP. So all the other changes are irrelevant despite the fact that the shaft HP is higher (roughly 30% higher) inflight for the second case compared to the first. The secret bonus question was to determine the likely difference in propellor efficiency but you have to make some assumptions for that one. Of course it's ~30% higher in the first case Maybe 65% efficient for the first case and 50% in the second. The numbers are made up for this case but are relatively close to real. Bottom line being you are always going to be using the same HP in level flight at the same speed no matter how much "power" you have or how big or small your engine might be. So it's a matter of how the power varies in maneuvering that you are choosing, not the level of HP.
« Last Edit: November 01, 2013, 02:49:18 PM by Brett Buck »

Online Dave_Trible

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Re: Science in pics
« Reply #46 on: November 01, 2013, 10:56:49 AM »
All of those airpanes that fly "right off the bench" were used up by the mid to late 50's.

Keith
Well, I've read about them in fables.

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Re: Science in pics
« Reply #47 on: November 01, 2013, 11:24:59 AM »
You have a 33.33 record spinning and a fly lands on it. How far will the fly ,fly off when the record stops.

ANSWER

There are many families of flies in North America. Although the life cycle of a fly can range from days to years depending on species and conditions, all flies undergo a complete four-stage life cycle that consists of egg, larva, pupa and adult stages.

The adult housefly can live up to one month in the wild. The fruit fly also lives for approximately 30 days after reaching adulthood. Flies survive longest in warmer temperatures and their ideal temperatures—between 75 and 80 degrees—are those found in most American homes.
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Offline Tim Wescott

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Re: Science in pics
« Reply #48 on: November 01, 2013, 02:46:43 PM »
     F-- for the airplane case. Level flight HP applied to the airplane, for the first case, is .415 HP (you can convert to PS for your metric fetish on you own time).  Double F- for missing the point.

Whoops -- I missed the drag figure.  Yes, you do have sufficient information in there.
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Offline Serge_Krauss

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Re: Science in pics
« Reply #49 on: November 01, 2013, 09:14:57 PM »
I was taught to place ALL my bellcranks on the CG, told this in the late 50's...I still place all my bellcranks on the CG, no matter what I'm told.

With everything that has been said "and proven," and I'm a believer in science, yeah right, then why on earth are "everyone's" leadouts adjustable?

Bottom line, if you don't mind, I'll have adjustable leadouts and my bellcranks will be on the CG. Am I doing this wrong? Charles

Hi, Charles. The point is that of course you're not doing it wrong; it doesn't matter where you put the darned thing. You can't be wrong.

...UNLESS, you deliberately misconfigure a plane to fit one in there, when it would not otherwise fit. Of course, you know that no one is going to get it perfectly on the c.g , and the c.g. is probably outboard of, above, or below wherever most guys think it is anyway. Although this has been discussed here before, I ought to remind that adjustable leadouts are necessary for varying flight conditions, speeds, and c.g. locations, and changes in the model from day to day and as it ages. Fortunately, the bellcrank location still doesn't matter. Finally, it's nice to know that if space or structural problems dictate, you can re-locate it a bit without fear of doing anything but perhaps wearing the lines more - or less. I have two designs on the board - quite unconventional - that dictate bellcrank positions both ahead of and behind the longitudinal c.g. position, for two quite different reasons. I'll deal with the wear and not worry about control. Scientific truth does not always make things more complicated.


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