0
Groundbound

Car drops?

Recommended Posts

Can anyone explain why the cars and other vehicles I see in the vids move about so unpredictably?
I figured they would roll in a regular fashion, or maybe a repetitive oscillate - but from the looks of what they are doing, unprovoked by any weight shifts it seems unexplained by known science!

Share this post


Link to post
Share on other sites
Quote

Can anyone explain why the cars and other vehicles I see in the vids move about so unpredictably?
I figured they would roll in a regular fashion, or maybe a repetitive oscillate - but from the looks of what they are doing, unprovoked by any weight shifts it seems unexplained by known science!




***


Quick suggestion~

This site has volumes of information available,
through the 'search posts' option...

You may want to take some time and
look through EVERYTHING in there...

You will be the best informed 1st jump
student in your class!
B|

you don't want to go over the 10 question per
year limit so soon in your jumping career.

Enjoy & have fun!
;)










~ If you choke a Smurf, what color does it turn? ~

Share this post


Link to post
Share on other sites
>Can anyone explain why the cars and other vehicles I see in the vids
>move about so unpredictably?

Because cars make poor aircraft. They do indeed 'fly' in a sense but are horribly unstable. The odd oscillations you see are a result of the same aerodynamic forces that allow a plane to manuever, but since car designers don't design for those forces the same way airplane designers do, the oscillations are often unpredictable.

Share this post


Link to post
Share on other sites
If you mean the motion of large quantities of car in the streets I can assure you that this topic has been covered in physics research (I know someone who did it ;)). It turns out that the model describing this motion also applies to getting cornflakes out of the package, or getting a stampeding crowd out of a shopping mall.

My question to you is now. Where does this fit into "General Skydiving Discussions" :)
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

Share this post


Link to post
Share on other sites
Quote

My question to you is now. Where does this fit into "General Skydiving Discussions" :)



i'm assuming he watched the same video I did - with the guys skydiving with a car (and I'm assuming the video was genuine...)
Skydiving: wasting fossil fuels just for fun.

Share this post


Link to post
Share on other sites
Quote

... it seems unexplained by known science!



It is explained by known science. It is called turbulent flow. Don't confuse the science you know with the science others know. You can experience similar behavior in freefall. Give it a try...

-- Jeff
My Skydiving History

Share this post


Link to post
Share on other sites
Quote

Quote

My question to you is now. Where does this fit into "General Skydiving Discussions" :)



i'm assuming he watched the same video I did - with the guys skydiving with a car (and I'm assuming the video was genuine...)



The video I know about showing this is Joe Jennings' "Good Stuff". They chuck the cars out of what I believe are CASAs outside Eloy. (At least, they showed Eloy.)

Based solely on what I saw in that video: they drop the cars in parts of the desert where they don't expect anyone to be. They clean up their messes. They prepare the cars (according to the video) to a great degree, probably to make them lighter, safer to ride in, and easier to clean up. They sometimes have injuries from the car beating them up, but sometimes they get a car that decides to fly real nice.

It's all in Good Stuff, which if I may plug, is cheap and a fun watch.

Edited to add: this video is why I'm a skydiver right now. :)

-=-=-=-=-
Pull.

Share this post


Link to post
Share on other sites
Here is one of the videos with the cars doing maneuvers I would not have expected, or could not have explained.
http://www.skydive.tv/golf.mov
It is from a link someone else provided here
http://www.joejennings.com/
which has plenty of interesting skydive videos.

Someone asked 'why this forum?' and it may not be the right one, I apologize if I was wrong but look at the choices:
General
Safety and Training
Gear
Instructors
Incidents
Wind Tunnels
Events
History
I just didn't see a better place to discuss aerodynamics.
(How about it moderators? Tell me where I should have asked this question, or if I should have at all. You will find me a very compliant participant!)

And I am getting a few comments that indicate some don't like to hear my questions. I apologize to you. I myself have worried when I joined DZ.com if the long-time members would tolerate the Q's of a newbie... and I have asked repeatedly if there is some other place to go, to learn about skydiving.. like a new guy forum. (with no reply so far) Too bad this software doesn't have an "Ignore" feature so the experienced guys don't have to be tortured by the questions of a new guy. If questions are unwelcome here then I will ask the mods to indicate so and I will disappear in a flash... if not then I ask the tolerance of others... perhaps you could just skip over posts that are "Authored" by me, "Groundbound"?

Maybe I will make my titles more obvious so you will know what is coming and can just skip over and save yo time and grief? How about a capital N in brackets to indicating goofball Newbie post?!:D
There, I have adjusted this title.
Thanks

Share this post


Link to post
Share on other sites
you might want to include the term 'junk day' in your search. don't know if it's an annual event or what, but they've chucked all kinds of stuff out of airplanes over the desert.
"Hang on a sec, the young'uns are throwin' beer cans at a golf cart."
MB4252 TDS699
killing threads since 2001

Share this post


Link to post
Share on other sites
Back to the original question on the car, if anyone has any knowledge about it I am interested.

Seems to me that an object will tend to fall with its CG (center of gravity) as close to the force of gravity as possible (hence the 'arch' position skydivers assume?)
And an engineless car has its CG in the lower half of the vehicle, and midway from the front to the rear.

Until that point that it is falling fast enough to develop air resistance on its surfaces. I can see how it may oscillate about its CG if it starts down in an unbalanced or unstable manner. But what stabilizes or destabilizes oscillations? I believe you skydivers probably know the answer to that, having experienced such airflows personally. Any ideas here?
Thanks.

Share this post


Link to post
Share on other sites
Quote

And I am getting a few comments that indicate some don't like to hear my questions. I apologize to you. I myself have worried when I joined DZ.com if the long-time members would tolerate the Q's of a newbie... and I have asked repeatedly if there is some other place to go, to learn about skydiving.. like a new guy forum. (with no reply so far) Too bad this software doesn't have an "Ignore" feature so the experienced guys don't have to be tortured by the questions of a new guy. If questions are unwelcome here then I will ask the mods to indicate so and I will disappear in a flash... if not then I ask the tolerance of others... perhaps you could just skip over posts that are "Authored" by me, "Groundbound"?

Maybe I will make my titles more obvious so you will know what is coming and can just skip over and save yo time and grief? How about a capital N in brackets to indicating goofball Newbie post?!:D
There, I have adjusted this title.
Thanks




Dude, forget em. There are people in the sport we refer to as "Skygods". Those that are too "good" to be bothered with such issues and normalcies that all beginner skydiver deals with. Some are assholes about it, and some dont want to be your friend for a while, until you have "proved" yourself. Either way, just give them thier space and try not to take it personally right off the bat. It's not how I operate, and I dont agree with how they choose to treat others, but whatever, ya cant change them right?

Well, there is the same phenomenom here on DZ.Com. I'm not quite sure what you could refer to them as....maybe "PostGod, PostWhore, or GeekyInternetFucktard". But nonetheless, they are there. Its the ones that forgot what it was like when they just started anything new and exciting. Some have tact.....most dont. If anyone gives you shit for a question they deemed irritating, just ignore them and go about your biz...

There are ways though to make your introduction to DZ.com as smooth as possible.

1. Lurk a while and get a feel for it. There are definitely a "few" interesting characters here.
2. When you have a burning question, toss it into the search posts link first...you will be amazed at all the useless crap we talk about here.;)
3. NO ALL CAPS!
4. And last but not least, realize that with every post, no matter how much sense you make, ie proven laws of physics...there will be some clown that will argue with you anyways, just because their job sucks ass and they have nothing to do at work, except give you shit.
5. Laws of Gravity will be excempt from #4. If they do argue with that, then they arent a skydiver anyways and your wasting your time talking to a whuffo.;)

Welcome to Dramazone.com and don't feed the trolls....

Share this post


Link to post
Share on other sites
Quote

I myself have worried when I joined DZ.com if the long-time members would tolerate the Q's of a newbie...



I admire your excitement - every time I see a post I think, "there he goes again" - but with a smile on my face because I had just as many questions as you, and now that I have 75ish jumps, the questions are still commn'.

But, I think it is time you go out and get jumping and post some replies to how much fun you had, along with 50 more questions!!! Whatcha doing this weekend, because if the sky is blue, you gotta tell us how the jumps went.:P I just say that because 5 years ago I lurked on some skydiving forums and got overwhelmed and never jumped... Then one day I snapped and went to the DZ and did my first jump and got hooked... Sometimes jumping is eaiser than talking about jumpn'.B|

Share this post


Link to post
Share on other sites
I'll add one thing to what Jose said above.

Use the Search function

Many of the questions asked by those that are new have been asked and answered many times.

I was away from skydiving for 16 years and came back a couple of years ago. In that time lots of things changed. One of the best things learning tools was this forum and the search function.

I found that most of what I wanted to know could be easily looked up and it meant that I got immediate answers to my questions without having to wait for someone to respond.

Give it try, it works like a top:)
"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy

Share this post


Link to post
Share on other sites
>but aren't things like cars very unsafe both for the skydivers and,
> um, the people on the ground, especially if their movements
> through the air are so unpredictable?

Yes. Hence the efforts to do such drops far away from people in the desert.

A few years back I was at an event where a snowmobile was dropped from a Skyvan over a massive field. The jumpers took it out the back, rode it for a while, then deployed. It assumed a stable nose-down attitude, started to 'track', and ended up landing (exploding, actually) about 50 yards from some cows at the far end of the field.

Objects such as cars and snowmobiles can indeed do unpredictable things, and a lot of caution/planning is required if you want to pull off such a drop safely.

Share this post


Link to post
Share on other sites
>Seems to me that an object will tend to fall with its CG (center of
>gravity) as close to the force of gravity as possible . . .

Not really. If that were the case, aircraft such as Cessnas would always be pointed straight down, so their engines (the heaviest parts of them) pointed down.

>But what stabilizes or destabilizes oscillations?

A million things. Even stable aircraft exhibit what is called a phugoid oscillation - a longitudinal oscillation that, ironically, is due to its inherent stability.

But in a car - who knows what might happen? Perhaps the curve of the hood combined with the slope of the windshield will combine to generate lift such that the front end of the car comes up. Then the front end 'stalls' and it drops again, but this time it goes completely over, and falls top-to-earth. Then the wind catches the side of the car and it rolls 180 the same way the wind turns a Savonius windmill. Then it stops for a split second, but now the wind starts generating a low pressure area on the trunk . . .

Or something completely different could happen. It would not be at all hard to design a 'drop vehicle' that would be marginally stable; there are a dozen ways you might accomplish that, from ballast to fins to a drouge. But without that effort, I think the actions a car take in freefall are pretty unpredictable.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account. It's free!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
0