SKYDIVE@f15.n233.z1.FIDONET.ORG (SKYDIVE) (04/12/91)
Reply-to: Dave.Appel@p30.f30.n231.z1.fidonet.org (Dave Appel)
Fido-To: all
This is just a mental excercise, and I am asking if
any structural engineers or architects out there would
like to help me.
I am just dreaming about building a special purpose
platform dedicated to bungee jumping, and BASE jumping
(jumping with a parachute). Here's a very rough sketch.
/-I-\ I-\ ^
/ I \ I \ |
/ I \ I \ |
/ I \ I \ | 500-600'
/ I \ I \ |
/a I a\ I b\ V
front view side view
All I have so far, is a 3 legged structure, with a
platform on top, and the platform is 500' to 600' off
the ground, and capable of holding 2,000 lbs of people
and equipment. The 2 front legs are in the vertical
plane, with the 3rd back leg at a sharper angle. This
would give 180 degrees of freedom for parachute (BASE)
jumpers. The platform would have a railing.
I envision the platform being 10' wide by 6' deep.
To make the structure safe for parachute jumping,
there shouldn't be any guy wires. All 3 legs would
consist of 3 or 4 bars or angle beams with cross-
bracing. Sorry, I don't know the technical terms. One
leg would have steps with hand railings on both sides
for access to the platform.
I don't know what angle "a" should be. I am
guessing somewhere between 60 and 45 degrees. I'm
hoping 60 degrees would do. I also have no idea what
angle "b" should be for the 3rd leg (that leg is in a
plane perpendicular to the plane of the front 2 legs.)
I'm guessing 45 degrees.
We would also need to take lightning protection
devices into account.
Would anyone like to help me on this dream project
with some figures for dimensions, angles, kind of
steel to use, how deep to sink the cement footings and
estimates for cost of materials and labor. Like I
said, this is just a dream project. But with people
paying up to $90 for a bungee jump, and lots of base
jumpers looking for legal jumps, this project just
"might" become reality some day.
--- XRS!% 4.10
--- eecp 1.45 LM2
* Origin: The Drop Zone, Dave Appel, 1:231/30.30 (Quick 1:231/30.30)
--
SKYDIVE - via FidoNet node 1:233/13 (ehsnet.fidonet.org)ryoder@en.ecn.purdue.edu (Robert W Yoder) (04/14/91)
In article <2756.28075041@ehsnet.fidonet.org>, SKYDIVE@f15.n233.z1.FIDONET.ORG (SKYDIVE) writes: > Reply-to: Dave.Appel@p30.f30.n231.z1.fidonet.org (Dave Appel) > Fido-To: all > > This is just a mental excercise, and I am asking if > any structural engineers or architects out there would > like to help me. > I am just dreaming about building a special purpose > platform dedicated to bungee jumping, and BASE jumping > (jumping with a parachute). Here's a very rough sketch. > > /-I-\ I-\ ^ > / I \ I \ | > / I \ I \ | > / I \ I \ | 500-600' > / I \ I \ | > /a I a\ I b\ V > > front view side view > > All I have so far, is a 3 legged structure, with a > platform on top, and the platform is 500' to 600' off FIVE HUNDRED to SIX HUNDRED FEET!? I would expect the mechanical details to be trivial compared to the legal hassles with local ordinances and FAA regs. Of course, if you can convince them you are building a radio station, it might help in getting the permits. :-) Robert Yoder "It's 10 o'clock. Do you know where your child processes are?" 306 Hawkins Graduate House Internet: ryoder@ecn.purdue.edu West Lafayette, IN 47906 Bitnet: ryoder%ecn.purdue.edu@purccvm (317)495-6845 N9CON UUCP: {purdue, pur-ee}!ecn.purdue.edu!ryoder Just curious
kas@hpcvia.CV.HP.COM (ken_scofield) (04/15/91)
From: SKYDIVE@f15.n233.z1.FIDONET.ORG (SKYDIVE) Subject: BASE and Bungee Message-ID: <2756.28075041@ehsnet.fidonet.org> > This is just a mental excercise, and I am asking if > any structural engineers or architects out there would > like to help me. I'm not an architect, but as a mechanical engineer, I can give some generalizations... > I am just dreaming about building a special purpose > platform dedicated to bungee jumping, and BASE jumping > (jumping with a parachute). Here's a very rough sketch. > > /-I-\ I-\ ^ > / I \ I \ | > / I \ I \ | > / I \ I \ | 500-600' > / I \ I \ | > /a I a\ I b\ V > > front view side view > > All I have so far, is a 3 legged structure, with a > platform on top, and the platform is 500' to 600' off > the ground, and capable of holding 2,000 lbs of people Compared to the weight of the structure itself, this load is peanuts. Your main concern will be to make the structure sufficiently strong to support its own weight. I suspect each leg would weigh several tons, so a few hundred extra pounds per leg is negligible. > and equipment. The 2 front legs are in the vertical > plane, with the 3rd back leg at a sharper angle. This > would give 180 degrees of freedom for parachute (BASE) > jumpers. The platform would have a railing. > I envision the platform being 10' wide by 6' deep. > To make the structure safe for parachute jumping, > there shouldn't be any guy wires. All 3 legs would > consist of 3 or 4 bars or angle beams with cross- > bracing. Sorry, I don't know the technical terms. One > leg would have steps with hand railings on both sides > for access to the platform. > I don't know what angle "a" should be. I am > guessing somewhere between 60 and 45 degrees. I'm > hoping 60 degrees would do. I also have no idea what > angle "b" should be for the 3rd leg (that leg is in a > plane perpendicular to the plane of the front 2 legs.) > I'm guessing 45 degrees. In general, you want all of the angles to be as large as possible (i.e., approaching 90 degrees. In fact, just about the only force you are designing for, other than the structure's own weight, is wind loading. Anything that is several hundred feet tall is going to have substantial "sail" area. (To over-simplify a bit, in a perfectly calm environment, the ideal solution to your problem would be a giant flagpole, not a tripod.) It's impossible to give you the "best" angles to use without actually doing the complete design, because the design determines the amount of wind drag which will occur, which in turn affects the angles needed. But, using the Seattle Space Needle as an example, it's obvious that the angles can be near-vertical. Perhaps a bigger issue is how much lateral movement a bungee jumper would experience due to wind. While near-vertical legs would be sufficient to support the structure, a rebounding bungee jumper in a crosswind might end up colliding with a leg. Something to think about. > We would also need to take lightning protection > devices into account. A) Anyone on the tower in a lightning storm deserves what they get... ;-) B) With a sufficient ground rod attached, lightning isn't going to hurt the tower. > Would anyone like to help me on this dream project > with some figures for dimensions, angles, kind of > steel to use, how deep to sink the cement footings and > estimates for cost of materials and labor. Like I > said, this is just a dream project. But with people > paying up to $90 for a bungee jump, and lots of base > jumpers looking for legal jumps, this project just > "might" become reality some day. The real answer to these questions is this: You're going to have to get permits to build something like this, especially if it will be open to the public. The powers that hand out such building permits will demand that you have card-carrying engineers design the structure -- at no small expense. Any "free" advice you get from me or anyone else is worth what you paid for it. (Sorry if I'm raining on your parade, but nothing is ever as simple as we'd like it to be.) > * Origin: The Drop Zone, Dave Appel, 1:231/30.30 (Quick 1:231/30.30) >-- >SKYDIVE - via FidoNet node 1:233/13 (ehsnet.fidonet.org) Ken Scofield C-9355 SSI #453890085 ^ Hewlett-Packard, ICO Phone: (503)750-2426 |----/-\----| 1020 NE Circle Blvd. (kas@hpcvia.CV.HP.COM) | Gone | Corvallis, OR 97330 (ucbvax!hplabs!hp-pcd!kas) | Divin' or | | Jumpin' | Cute Disclaimer: Nobody ever listened to me before, |-----------| so why start now?
SKYDIVE@f15.n233.z1.FIDONET.ORG (SKYDIVE) (04/21/91)
Reply-to: Dave.Appel@p30.f30.n231.z1.fidonet.org (Dave Appel) Fido-To: uiucuxc!hpcvia.cv.hp.com! In a message to Skydive <17 Apr 91 17:40> (Ken Scofield) uiucuxc!hpcvia.CV.HP.COM! wrote: > The real answer to these questions is this: You're going to have to get > permits to build something like this, especially if it will be open to > the public. The powers that hand out such building permits will demand > that you have card-carrying engineers > design the structure -- at no small > expense. Any "free" advice you get from me or anyone else is worth what > you paid for it. (Sorry if I'm raining on your parade, but nothing is > ever as simple as we'd like it to be.) > Ken Scofield C-9355 SSI #453890085 Naturally. Who in their right mind would attempt to build a structure in the 100's of thousands of dollars range without permits and "real" engineers? I mainly wanted to start a useless discussion about a useless topic along the lines of bungee-jumping from a jump plane, but something we could more easily apply numbers to. I also get burning questions in my mind and need to ask them and get *some* sort of answer to lay them to rest. Sort of an adult version of "why is the sky blue?" type of thing. Thanks for your info, stuff like "sail area" and all that. BTW, I saw some bungee jumps on tape. A group from the local DZ took a road trip to a certain bridge to do bungee jumps. The pendulum-like swings of the person at the end of the bungee seemed to be 20 to 30 degrees each side of vertical. --- XRS!% 4.10 --- eecp 1.45 LM2 * Origin: The Drop Zone, Dave Appel, 1:231/30.30 (Quick 1:231/30.30) -- SKYDIVE - via FidoNet node 1:233/13 (ehsnet.fidonet.org)