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chillenfish
May 2, 2005, 2:38 AM
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Sweet wall man, looks like you can have a good time on that thing. The only thing i question though esp. when getting into the lower deg on the wall (ie. away from 90) is that those support posts will hold up right. All of the weight will be pulling on them in a funny angle and wasn't sure if they were connected to the wall behind them or not. Just something to look into or watch out for.
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spikeyhair13
May 2, 2005, 2:53 AM
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yeah, those posts concern me as well. even at that angle it seems like they would bend alot. is this the case? maybe they are strudy, i just dont think they look strong enough. but i guess you will fing out. :twisted:
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xprompt
May 2, 2005, 3:02 AM
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They're plenty strong, plus theyre 5 feet cemented in the ground
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johnathon78
May 2, 2005, 3:55 AM
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Sweet woody. Whats the cost on that, minus the holds?
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xprompt
May 2, 2005, 4:03 AM
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about $300 with the paint and wood and cement and chains. however i got some good wood for free cuz they're building a house next door to me so i probably spent around $100-150 on it. just look for deals.
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112
May 2, 2005, 4:06 AM
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I think your wall looks pretty cool. Congrats. But I am curious how do you know:
In reply to: They're plenty strong, plus theyre 5 feet cemented in the ground
Did someone help you design it, or are you that good that you know how to design cantalever beams? Is your dad a Civil Engineer or something. I swear I am not trying to be mean, I am just curious.
I finished framing my wall (it still needs a bondo surface finish), and I am enjoying it, but yours is much bigger. Very cool
Ken
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xprompt
May 2, 2005, 4:11 AM
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haha. its cool. i just used common sense. my uncle did tell me to put a foot of pvc in the bottom with cement around it so when it rains the wood wont rot. make sure you do this. (my dad's actually in the restaurant business.) my dad helped me but thats all the advice i got. other than that 100% me
minus the help to lift it
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scottquig
May 2, 2005, 4:36 AM
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In reply to: haha. its cool. i just used common sense.
I'm gonna laugh when you lower the wall to 60 degrees, put your weight on it, and the 4x4's shear off at the ground.
You'd be very well advised to put in a sturdy triangle truss from the top of the 4x4, down to the ground about 5 or 6 feet out from the base, and then back to the 4x4.
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xprompt
May 2, 2005, 4:44 AM
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actually i already have that for greater angles except... it is bolted on the wall to the ground with a 2x4 on each side. its plenty strong.
thanks for the concern
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korntera
May 2, 2005, 5:06 AM
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Bad ass, i am hopefully building a small wall this summer, that looks good.
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yamama
May 2, 2005, 6:00 AM
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Just wondering how u did the bottom, like where the wall touches the ground. I was thinking about making one just like it but in a barn with concrete floors. I was thinking about making it connected to the floor some how...
...any suggestions
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xprompt
May 2, 2005, 7:05 AM
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its just sitting on the ground. the weight of the wall keeps it stable. your could just get some big hinges and bolt them to the ground and wall.
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lnmego
May 2, 2005, 4:33 PM
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Yeah, I "unofficially" bet that those will breack if you lower your wall to >45 degrees and a 200 pounder lands a dyno. I'll do the numbers tonight. I'd be happy to see someone else's too.
Edit: I can't find the minimum requirements for shear force of 4x4 lumber. But all it takes is one low placed knot on the same side as your high roof jug to cause a possibly career ending accident. I wish you luck.
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edge
May 2, 2005, 4:42 PM
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As an engineer with extensive construction experience, I too fear for your life.
Not trying to be mean, just trying to help.
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cintune
May 2, 2005, 5:12 PM
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http://www.rockclimbing.com/...p.cgi?Detailed=29730
At least you've got a nice crash pad in place.
But seriously, over time those posts are very likely to give, and no one wants you to end up squashed under that thing. It probably wouldn't kill you, but could hurt a lot. Adding some 45-degree braces like Scott said would be smart. You might also want to bolt some steel cables through the tops of the posts back into some kind of anchor on top of that brick structure. Think Redundant. My wall is the same size, but it's not adjustable and I've still got it anchored down three ways, just in case.
http://www.oldnewspublishing.com/climbingwall.jpg
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keinangst
May 2, 2005, 5:12 PM
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I'm not an engineer, but that photo looks like something you would photoshop and submit to a "how to kill yourself" thread.
Even if those 4x4 posts hold, the flexion won't be reassuring. In the "locked" upright position, what's holding the wall in place? Some kind of pins or bolts through the uprights and the frame?
The only thing I could envision that would inspire any confidence--assuming you can't build anything behind that brick wall (neighbor's house?), would be this:
An offset A-frame that straddles the entire rig. You would need uprights that are greater than 12' tall, using those current locations. Then run diagonals down around 30 degrees+ (a 15' above-ground diagonal) to offset the load on the wall when angled. The cross beam would have to be huge, like double 2x10 beams, and be sure the joint was extremely secure. Hook your chains to that cross-beam, near the joint, and you'd be good to go.
Again, not an engineer, just using some common sense. I hope you'll add a little beef to that frame before working on steep overhangs. You really don't want 300# or more to fall down on you as the chest-level jugs snap ribs and pucture lungs.
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anjinsan
May 4, 2005, 4:11 AM
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I would not put that wall lower than about 20 degrees without some serious supports to those posts. I have been looking for the shear modulus for wood in all my structures books and none of them list wood for anything but compression loading. The weight of you hanging on that board at any decient angle will result in a large moment at the base of that post. I will run the numbers as to the strength of those posts as soon as I find the shear modulus of wood. My opinion, and Ive done quite a bit of structures, is that your wall has a high probability of bringing your climbing career to a crashing hault.
Matt
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kurplunk
May 4, 2005, 5:38 AM
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I like the idea, but have to agree the posts are not safe at significant angles. Maybe the cantilever concept could be salvaged if the posts were replaced with galvanized steel pipe, but that might be over $100ea - unless you score at a salvage yard. Additional wood framing might be cheaper.
Consider having additional people review the plans. The City (Burbank?) could help with safety, height and property line distance requirements.
Happy climbing.
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greenketch
May 4, 2005, 3:37 PM
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xprompt, I am going to weigh in on both sides of the fence. I like the looks of the wall. It looks to me like it pivots such that you cannot achieve much more angle than is shown. Doesn't the bottom hit the wall behind it? This would be a very good thing as the others are right about the shear on the posts if much more angle was achieved. I think that if you ran some chain from your upper bolt to the top of the masonry wall that would be significantly better. Use a turnbuckle in that chain so that you can preload the link a bit and it should prevent flex (and shear) in the posts.
Thanks for shareing you project
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lucas_timmer
May 4, 2005, 3:59 PM
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Goddamn Cintune, you're wall is wicked !!!
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freeskicolorado
May 4, 2005, 4:05 PM
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In reply to: I will run the numbers as to the strength of those posts as soon as I find the shear modulus of wood.
http://www.matweb.com is your best bet for finding the shear modulus. I believe 2X4's and probably 4X4's as well are made from pine. Material property data for North American Loblolly Pine Wood is provided at http://www.matweb.com/....asp?bassnum=PTSA600
If I have a chance, I'll work the numbers myself and see what I come up with (I'm a mechanical engineering student). xpromt, it would be very useful to know how tall the 4X4 posts are.
My intial thought is the same as many other have already said - that structure is most likely not strong enough to be safe.
Jeff
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cadaverchris
May 4, 2005, 4:26 PM
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xprompt - How long are the chains? In other words, how low can you lower the wall?
I think more than enough people have told you there is a high likelihood for serious injury if you climb on that thing with any angle steeper than what is shown.
PLEASE, fix it!
bolt the uprights back to the concrete structure in 2 points each. tension that rigging with a turnbulcke as someone above as Greenketch has said.
or build an A-fram on each side to deal the direction of force from the wall.
editted once for spelling
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onsight_endorphines
May 4, 2005, 5:23 PM
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To those of you that had nothing NICE to say about the OP's new wall, please STFU. I don't care if it was made of balsa wood and duct tape, at least offer a "cool man" or "looks nice" before you tear into his design and tell him he's going to kill himself. Shit people, get a grip.
To the OP: What does the wall feel like? Have you done a real-world test at high angle to see if things flex, make cracking sounds, etc.?
Obviously, be careful. Rig something to catch the wall if the posts snap...several friends may be handy for this.
I'd grab the top of the wall, and WANK on it as hard as you can, and evaluate things like that. A dyno to the top is good. Anyway, it's better to break it under controlled circumstances...
However, the wall looks pretty sturdy to me.
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freeskicolorado
May 4, 2005, 5:30 PM
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I did some calculations. Obviously, these are rough numbers because I had to make several assumptions to be able to solve the problem.
I calculated these numbers based on the wall being lowered to the point where the chain is directly horizontal, because that would result in the greatest moment about the base of the beam. This position occurs when the wall is tilted about 20 degrees from vertical. I also assumed that there is a 200 lb person hanging from the top of the wall, and the wall itself weighs 300 lb.
As a note to the other person who said they would run the numbers - this is a beam bending problem, meaning the beam experiences tensile, not shear, stress. By my calculations, the tensile stress in the 4X4 post at a wall angle of 20 degrees would be 737.5 psi. The ultimate tensile strength of pine wood is 464 psi.
In simple terms, that means the post WILL break if the wall is tilted 20 degrees and a 200 lb person hangs from the top of the wall. Please note that you could easily put much more force on the top of the wall while climbing than that even if you weighed much less than 200 lb. That means it would be even more likely to break. I didn't calculate what the limit is for how far you could tilt the wall before the post would break because there are just too many unknowns to provide a definitive answer. It's safe to say that you could very well be risking breaking the posts even in the configuration shown in the photo.
Long story short, my engineering knowledge tells me that your wall is not safe. In my opinion, you need to add some supports and braces to the structure to make it strong enough to climb on. I'm not telling you this to be mean, or bash your building skills, or anything like that. I just would really hate to see you get hurt.
EDIT: the guy who posted above me has a good point. Let me apologize - I definitely think it's a cool wall and it looks like you'll have a lot of fun on it. I wish I had the space and money to build one myself :D I just want to help you out and make sure you don't end up with the wall on your chest.
Jeff
*edited once for a typo*
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