Rf6 == Fail

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prototype3a said:
Maybe but you did fail to notice that the acceleration of gravity in RF6 is less than half that of the real world.
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Eh, no. You just don't understand that the sim does not ramp up the physics after a reset immediately.

"dropping" an object by positioning it in the air, and saving it's position, then hitting reset, does not "start the clock" immediately, this is by design to make certain things work properly on a reset.... otherwise our planes would drop out of the sky on a reset....

You're clocking TIME elapsed, not actual acceleration over time, so your figures are in error and your observations are specious.

Given that you don't actually OWN the sim, you are best off reserving your observations until you do buy it so you have a chance at understanding how it actually works.
 
td9cowboy said:
Maj. I don't think prototype is going to be upgrading any time soon. He keeps quoting 200 bucks for the upgrade when everyone else with G3 and a working interlink can upgrade for fifty bucks. OHH....Wait!!
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Good point !
I think I see where you're going
If he really does own 3.5 and had been to the LHS to try out 6 he would know that the price point is well below what hes quoting for an upgrade
maybe he does not even own RF at all or has never gone to a local kiosk
explains why he needs the opinions of others even when speaking of 3.5

Just another one of those folks who either works for or , has a loyalty to an inferior RC Sim that comes out of the woodwork's every year around this time
to bad mouth RF with inflammatory, incorrect assumptions and statements .

Thanks TD9 I see things more clearly now :D
 
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If I can weigh in and make an argument for the age of the physics engine as I have done before. I believe that the problem lies in different speeds of different rigs.
Something like gravity in a sim like this is calculated per physics frame. A physics frame is one read through the code. On each read or frame the position of the falling object is updated and compared to the preceding. The distance between the two positions would be perceived as the speed of said object. Since the speed at which a computer can go through the code one time varys from machine to machine the perceived rate of decent will vary.
Seeing as prototype3a made his observations from a HS display machine that was probably issued with G2 or G3 running a sim optimized for newer more powerful rigs is the reason for the discrepancy.
Phranks experiment suggests and supports my claims. It's just a natural limitation that is experienced with almost any other sim or game on the market.
It is possible to see a read of the Physics frames versus the Graphics frames by editing the nav guides gadget to display them. My machine while running 3dsmax, photoshop, and chrome in the background and with windows Aero is 100 plus. So I never have experienced the slow gravity you describe. I highly doubt an old HS rig can boast Physic frame rates over 50.
I don't say any of this in defense of RF 6, but merely to explain what I think is going on from a programming point of view.
@prototype3a if your computer is powerful enough for some of the modern games I can reassure you that the condition you describe does not exist on a sufficient machine. FWIW
 
I was going to mention terminal velocity when I saw the first unread reply to this thread, but then I saw someone mention aerodynamic drag (I think Td9). I think Opjose makes a good point about how things behave when reset.

I would like to run my own experiments, but unfortunately I've had zero time lately to get on my PC. I still haven't even updated RF6 to the latest beta from 11/29/2011 and I never go longer than the next day to have it installed.

I don't know if there is a way we could take a sample model with zero aerodynamics percent and drop it resulting in no drag whatsoever. We could, like the Mythbusters, drop the model from an airport object setup with black and white horizontal stripes each one foot thick. Record the drop with FRAPS so we could calculate the rate of fall.

We could verify the time from the recording when the object actually starts falling to when it hits the ground. We wouldn't have to rely on when the button was pushed this way, which would help eliminate human error. The model could be made with thrusters which are balanced with gyros. the exhaust exit velocity should drop instantly when the throttle is cut on the thrusters, but that needs confirmed. We could always subtract the throttle servo response of .01 seconds since that is the shortest response time increment to use. Hand launched will not work since it always throws the object.

Dr.Moo created a UFO quite some time ago which holds it's position perfectly in place. This model could be used as reference for this experiment. If I could find the time, I would make the airport object myself. It just sounds fun to do even if we've moved past this once I'm done writing this post.
 
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Boof,

That's an interesting theory but it doesn't work that way.

The sim can correctly predict such things even on very slow machines.

It's a challenge to explain how it can do that. You can google "integration solver" maybe to find some reading material.

It seems like everyone here is entertaining a wild allegation. If something as simple as gravitational acceleration is off, it will be child's play to prove this.

Jim
 
phrank said:
:p uhhh, yeah, what he said! :p

My main motivation here is that when I do grow a pair and try to auto my 450,
that I have reasonable and trustworty sim practice to start with. ;)
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Phrank,

I didn't even own a sim capable of performing auto-rotations when I made my first auto with an Esky Belt CP from 50 feet up. I somehow was able to do it and land in one piece by only having read how to auto from RCHelimag and various other sources on the web.

I believe in you Phrank. Just go nose into the wind and land on soft ground.
 
It takes a 50ft drop for a ball baring to reach terminal velocity, (32ft per second
per second, (not a typo), or 200mph note that an aircraft has WWWAAAYYY more
drag than a ball baring. also, the weight in an aircraft is more spread out.
There for, an aircraft is going to fall slower at first, and is going to take more time
to reach terminal velocity.(if it ever does.)
 
brields said:
It takes a 50ft drop for a ball baring to reach terminal velocity, (32ft per second
per second, (not a typo), or 200mph note that an aircraft has WWWAAAYYY more
drag than a ball baring. also, the weight in an aircraft is more spread out.
There for, an aircraft is going to fall slower at first, and is going to take more time
to reach terminal velocity.(if it ever does.)
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Sure,
But note that the Major's jet took the "right" amount to fall vs the test mass I used.
That jet certainly has it's weight more spread out.
Kind of the opposite. :confused:

Not ready to eat that crow yet. ;)
 
A 50lb. object with all its weight concentrated on one point will fall faster than
a 100lb. object with its weight spread out. (example).
 
Success

Oh Dear, how embarrasing. I'm ready to eat that crow now. :eek:
I'm getting consistent results regardless of weight/size.
I'll post test Mass and airport after further confirmation.

You'll be glad to know RF6's gravity is indeed "True to life" :D
 
brields said:
A 50lb. object with all its weight concentrated on one point will fall faster than
a 100lb. object with its weight spread out. (example).
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If we dropped you, prototype3a, and master22 off of a 200 foot bridge, you'd all hit dirt at the same time.
 
brields said:
A 50lb. object with all its weight concentrated on one point will fall faster than
a 100lb. object with its weight spread out. (example).
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Ahh, warm fuzzy feeling to know that all those dollars spent on an engineering degree were a total waste. :rolleyes:

In leiu of education, Google "Galileo Galilei".
 
He's a kid, so at least the upper levels of the educational system are not to blame.

However I wonder where his physics teacher went wrong?

:D
 
You mean Isaac Newton?? http://en.wikipedia.org/wiki/Isaac_Newton

OK Both!

Or Nicole Oresme in the 14th century

All agree that the weight does not make a difference and was proven on the moon with a feather and a hammer. See, I did get something for that high priced education I paid for.

dhk79 said:
Ahh, warm fuzzy feeling to know that all those dollars spent on an engineering degree were a total waste. :rolleyes:

In leiu of education, Google "Galileo Galilei".
Click to expand...
 
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brields said:
A 50lb. object with all its weight concentrated on one point will fall faster than
a 100lb. object with its weight spread out. (example).
Click to expand...

It seems like you are getting some flak from others for this statement. It seems true to me, but maybe not worded in the best way.

It's true, everyone, gravitational acceleration is constant.

In a vacuum there is no aerodynamic drag to oppose gravitational acceleration, so two spheres the same distance from a third, larger object, experiencing no other forces, will accelerate at the same rate regardless of mass.

However, in an atmosphere the aerodynamic drag opposes gravitational acceleration. Therefore, the net acceleration depends considerably on the object's mass and shape.

I'll modify brields' comment to make it more clear, because I think what he meant was something like: In an atmosphere, a 50 lb solid sphere will accelerate in a free fall faster than a 50 lb hollow sphere of greater diameter.

Imagine how much farther you can throw a coke can if you crush it. It's the same thing.

Like most lessons in physics, finding the right visualization makes it much easier on the brain.

Jim
 
It's probably worth mentioning, then, that RealFlight does take all of this into account.

If you lock a plane at altitude and blow it up then release it (using the destroyVehicle and lockPosition commands), you'll be able to test it out. I predict you'll see that the wings do not reach the ground as quickly as the fuselage.

This is because most wings will tumble on the pitch axis. They get a bit of lift from this, and some unequal drag assuming the tip is narrower than the root. They will typically reach terminal velocity quickly, continuing in a tumble and tracing a spiral pattern to the ground.

The stabilizers do much the same thing but not as stably since their aspect ratio is so small.

Meanwhile the fuselage, wheels, and other odd-shaped bits will generally fall straight down.

Jim
 
jbourke said:
However, in an atmosphere the aerodynamic drag opposes gravitational acceleration. Therefore, the net acceleration depends considerably on the object's mass and shape.

Jim
Click to expand...

eh....

Gravitational effect ( acceleration ) is constant on both objects .... we wouldn't be here otherwise as the universe would be a very different place if this were not true.

Reduction in observed or clocked, acceleration amounts due to air drag only kicks in as the two objects start approaching a good percentage of the terminal velocity for a given surface area.

However true acceleration due to gravity is ALWAYS the same, though the observed behaviour can be affected by air resistance...

Once you start to get to terminal velocity, given a hollow 50lb ball versus a solid one, the increase in size of the hollow ball to be able to observe differences in acceleration due to resistance from air, requires a ratio increase of over 30:1 if not even far far more.

A ball has a good aerodynamic shape in terms of air penetration, so relative to the weight for the area presented it has to be relatively light for it's surface area to see terminal velocity effects.

A "light" 50 lb ball is going to be large, compared to say a small 8" 50lb cannonball. You are looking in the neighborhood of 3 feet or so.

If you took an 8" 50lb cannonball and a 50lb hollow 3 foot sphere, both would hit the ground at the same time if dropped from say 400'.

BTW: Mythbusters had an episode on this...
 
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Aerodynamic drag is a factor as soon as we consider the mass and shape of the object.

If RealFlight has an error in the rate at which things fall, it is an error in the aerodynamic drag. It is not an error in the gravitational acceleration.

I would need a reproducible example within RealFlight before knowing what to do.

Jim
 
I think the OP is too literal in his timing technique.

He's probably using a stop watch or timing function on the computer and thinks that somehow RF is off because his observations "must" be right... :D

He's using the "P" function to position an object then times the fall after the reset button is hit.

That's not a good way to gauge acceleration in the sim so he's seeing values that don't conform to reality.
 
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