Geometry for frame... (Full Version)

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wulfgarw -> Geometry for frame... (3/22/2008 9:58:55 PM)

Ok, for those of you whom have built a frame, I have a couple geometry/ measurements questions and a related materials question. I'm planning a wooden gallows type frame that can disassemble.  I don't plan on doing full on suspension.  http://www.saroftreve.com/workshop/frames.shtml

Question #1.
   I have a 8' cieling, so the top height will be about the 7' 9" mark and total width will be 6 to 7 feet wide.  To support a weight range of 600 lbs (me x 2), how wide does the base need to be to keep from tipping in the heat of the moment.  Is there a equasion that will help determine this length?  I was thinking of a 5' long base and that would give me a  height to base ratio of 1.55  Will this be long enough, or will it need to be longer?

Question #2.
   The uprights I'm planning on will be doubled 2x4's glued and bolted together with eyes to provide attachment.  Rather than permantly attaching this to the base piece (4x4) and its accociated braces, is there a better way that will allow disassembly without sacrificing strength?

Question #3.
    For the top crossbar, I was thinking of utilizing a 2.5 to 3 inch square tubing fitting and bolting into a mortise in the upright.  Does anyone have any ideas as how to shore up this connection short of a angle brace welded to the top bar bolting into the upright?

My thanks to all.



kittinSol -> RE: Geometry for frame... (3/22/2008 10:07:49 PM)

I've no idea what you're talking about, but I advise you to counterbalance all that hardware with some soft plush cushions [8D] .



wulfgarw -> RE: Geometry for frame... (3/22/2008 10:20:11 PM)

That's where the suspension cuffs come int play...after 'the device' is built.  I was (still is) a decision between this or a St Andrews Cross...




CalifChick -> RE: Geometry for frame... (3/22/2008 10:32:49 PM)

The standard size for the base is AT LEAST half the height.  If you're at 55%, you just over minimum and should be good. But I'm no expert.

Cali



wulfgarw -> RE: Geometry for frame... (3/22/2008 10:42:04 PM)

If I divide the base by height, that gives me .64935 or 65%.

Thanks!



Justme696 -> RE: Geometry for frame... (3/23/2008 2:26:43 AM)

I would go for option B.
Iti is eassy shape wise and can be contructed easily.    The top horizontal part I would fit in 2 u-shaped metal (Stainless steel) parts that are connected to the 2 verticle parts.
Drill a hole in both parts..so you can "Lock" them with a bold and nut.
Bit hard to explain because I don't know the english words.
I can show you some pictures..of the metal parts..to give you a clue. ( if needed I can sketch hem)
http://www.destil.nl/CatalogusMenu.asp?Niveau1=50

btw....dimension are important for 2 things....the heigt of the person..and momentum when people sling...you don't want to break it..or fall over.
If you make the base wide.. (side ways..too) then you are pretty safe. But don't forget the connection, those are more important...if the connection breaks..then you end in the hospital.
If you are done..try with with a big filled with sand..or something.

ps could you give an explanation of  point 3 ?



Focus50 -> RE: Geometry for frame... (3/23/2008 3:24:48 AM)

Well I have an engineering background (not a degree but a life of hands-on get in and design and build whatever is needed) and I doubt anyone could seriously answer these questions without actually being on-site and fully understanding it's purpose - it's gibberish! 
 
Anyway, if in doubt, build it out of steel tubing - it's much stronger than timber, is more readily strengthened and supported if it's not initially up to design and is easier to build so that in can be disassembled without compromising strength and rigidity.
 
And a 3 inch square tube cross bar - are you intending to also lift locomotive engines on the side??? 40mm SHS (1.5" square tube) with a 3mm wall thickness will easily handle 600lbs load, maybe up to 2inch squ if you're intending to drill holes through it.
 
Building big n beefy is easy - I torture myself by forever designing my stuff so that it's also light-weight and easily disassembled, too!  Arrggghhhh!!!!!  Still, I am somewhat proud of my fold-up and fully adjustible A frame - it only took a year and 3 prototypes to finish what was supposed to be a "simple" toy....!  But a lesson was learned - steel tube is the way to go for combining strength and rigidity with portability and lighter weight.
 
Focus.



Justme696 -> RE: Geometry for frame... (3/23/2008 3:35:05 AM)

steel will be as good as the worst connection made. I am worried about the welding connections.
( I am an engineer ..profession and a title.....do know shit about wood..but do about connections and welding of stainless steel).
A weld often covers it real purpose..the connection.

PErhaps round tube allows you to use screw connections. Like any fences use.

quote:

  Still, I am somewhat proud of my fold-up and fully adjustible A frame - it only took a year and 3 prototypes to finish what was supposed to be a "simple" toy....! 


lol..hobbies are great :P



Focus50 -> RE: Geometry for frame... (3/23/2008 3:49:33 AM)

quote:

ORIGINAL: Justme696

steel will be as good as the worst connection made. I am worried about the welding connections.
( I am an engineer ..profession and a title.....do know shit about wood..but do about connections and welding of stainless steel).
A weld often covers it real purpose..the connection.

PErhaps round tube allows you to use screw connections. Like any fences use.

quote:

  Still, I am somewhat proud of my fold-up and fully adjustible A frame - it only took a year and 3 prototypes to finish what was supposed to be a "simple" toy....! 


lol..hobbies are great :P

Aesthetically, stainless makes for a better looking job , assuming you can weld and take the time to polish them after....  However, stainless is not so good for handling stress, most esp even quality welds, and I would imagine a frame used for vigorous BDSM activity is gonna move and put pressure on the joints, no matter how rigid its design.
 
For that reason I prefer simple mild steel gal tube and, much like my A frame, it came up looking like a treat after I had it blasted and powder-coated....  Since this required involving outside contractors, I designed it so the attachment eyes could be screwed on later and is thus not so pleasing to the eye compared to simply welding them on initially.  Lol, I hate compromises and 3 rebuilds was ENOUGH...!
 
Focus.



Justme696 -> RE: Geometry for frame... (3/23/2008 4:41:34 AM)

lol  yes 3 times sound indeed enough.  Powder coating surely is needed with mild steel..and it looks tidy  and professional.



QuietDragon -> RE: Geometry for frame... (3/23/2008 4:56:19 AM)

Hi Wulf,

Take a look at http://www.keesystems.co.uk/index.php?option=com_wrapper&Itemid=8 and http://commercecenter.keeklamp.com/Main.asp for ideas about just how many pipe connectors you could potentially work with. Some of the brochures can be downloaded as PDFs too.

Steel tubing of various diameters and both based metal and powdercoated in many colours can be sourced either through local builder's merchants or through specialist steel stockholders. Most will also cut it to required lengths for a small extra charge prior to delivery.




TreasureKY -> RE: Geometry for frame... (3/23/2008 5:34:06 AM)


quote:

ORIGINAL: wulfgarw

... To support a weight range of 600 lbs (me x 2), how wide does the base need to be to keep from tipping in the heat of the moment.  Is there a equasion that will help determine this length? 


Isn't the internet great?  [:D]

Center of gravity explanation.

How to calculate the center of gravity.



Justme696 -> RE: Geometry for frame... (3/23/2008 5:40:56 AM)

yes there are calculations for it
but hmmm..people go to school for that. it is not easy

IF you have space..I would make the base as long as the height for now.That way it won't tip over. (perhaps you can make the base 2/3 of the height)
DOn't forget to support it sideways too. Mostly construction are build only to support force to front and back. But if you sling it can tip over side ways yoo of course. The side way support, because side ways force propably will be smaller, can shorter.... 1/3 of the height.

http://www.antonine-education.co.uk/Physics_AS/Module_2/Topic_7/topic_7__momentum.htm







DesFIP -> RE: Geometry for frame... (3/23/2008 9:24:39 AM)

I'm not sure your weight times two is sufficient. From what I've heard it needs to be more because this isn't dead weight. You'll be twisting, turning, jumping, moving. It needs to handle those stressors/



littlebitxxx -> RE: Geometry for frame... (3/23/2008 1:39:54 PM)

<FR>
For suspension cuffs, I went to an Athletic outlet and got weightlifting cuffs.  Designed for lower pulley work like abductors/adductors, they are rated for about 100 lbs each.  Very wide nylon, sticky velcro and solid D-rings.  They work great!  Add in some ratchet straps at various spots for larger girls...et voila!



PhoenixRed -> RE: Geometry for frame... (3/23/2008 2:05:06 PM)

I agree with QuiteDragon.  I made a cube from 2 5/8" diameter galvanized steel fence post (got it from a local fencing place), and used aluminum fittings as connectors (got those from an online industrial supply company).  The square design (4 upright posts) supports weight from all sides, and won't tip over.  I used 2 long poles across the sides, which are adjustable, to give it extra support and attachment points. The side poles extend past the cube and I made a shelf to put on them to hold equipment. You can use pipe fittings as attachment points, or drill into the pipe and tap the holes to use eye bolts/screws.  Using flanged base fittings or side fittings allows you to bolt it to the floor or walls.  If you plan appropriately for the space you want to set up in, you can figure out what the standard pipe lengths offered are, and in my case, they did cuts to spec for 50 cents each cut.  It was worth it the time and effort for them to do it at that price!  For fittings you never want to remove, use red locktite on the set screws.  Other than those fittings, the rest can be easily unscrewed to vary the height of fittings, etc.  Viola!, you have something that's sturdy, easy to disassemble and transport.  Admittedly, it isn't the lightest thing around (not as light as aluminum poles), but is strong.  Enjoy and have fun!



khem -> RE: Geometry for frame... (3/23/2008 3:12:24 PM)

quote:

Anyway, if in doubt, build it out of steel tubing - it's much stronger than timber, is more readily strengthened and supported if it's not initially up to design and is easier to build so that in can be disassembled without compromising strength and rigidity.


I have been lamenting how I was going to set up my new dungeon and build a st andrews cross without access to a table saw - so this is sounding really good until some lovely person with a saw starts volunteering to make and deliver my bondage furniture [:D]



khem -> RE: Geometry for frame... (3/23/2008 3:17:41 PM)

Err wait, no drill either.

I'm just going to start trolling for a mechanically inclined, tool-owning slave instead [:D]



DesFIP -> RE: Geometry for frame... (3/23/2008 4:50:38 PM)

quote:

ORIGINAL: khem

I have been lamenting how I was going to set up my new dungeon and build a st andrews cross without access to a table saw - so this is sounding really good until some lovely person with a saw starts volunteering to make and deliver my bondage furniture [:D]



You can rent a table saw from Home Depot.



khem -> RE: Geometry for frame... (3/23/2008 5:10:01 PM)

quote:

ORIGINAL: DesFIP

quote:

ORIGINAL: khem

I have been lamenting how I was going to set up my new dungeon and build a st andrews cross without access to a table saw - so this is sounding really good until some lovely person with a saw starts volunteering to make and deliver my bondage furniture [:D]



You can rent a table saw from Home Depot.

Oooooo, thank you for the info



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