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Red Heads / Diving board platform

775 views 18 replies 5 participants last post by  Mr_Andy 
#1 ·
Someone please agree with me here. SWIM is replacing a 30 year old diving board (8ft) base because one of the rotted anchors finally snapped and it's time to replace. His solution is to hammer drill 3 new holes and epoxy in whatever corresponding size Red Head and call it a day. An 8ft long diving board. I told him he could save a little money if he used Elmers glue instead, neither adhesive is gonna make a difference with that shear load. The new base even comes with a (imagine this!) 4" deep #4 rebar 'basket' with fastening points designed to be sunk in the new concrete. This helpful suggestion to the installer is being ignored. Too lazy to jack out the pad (3x5) and replace.

He has 2 kids with a pile of chitbird friends that use that diving board all the time too...

Social Darwinism and the thinning of the herd has begun :)
 
#2 ·
Your not talking about the Hilti anchor epoxy? Just like a blend that he made on a piece of ripped cardboard? Or we talking along the lines of some type of expandable anchor? FWIW, I used the Hilti brand anchor adhesive, which was used in no less than an 8" deep hole a few times, once being to hold a piping tower approx 16' in the air with multiple 4" concrete lined ductile iron pipes, and when used properly, I would trust that... but being that it's a patio pad and probably no more than 5" deep, I would definitely be jacking it out and pouring a new one....

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#3 ·
Hilti is the Coke to Red Head being Pepsi.. it's a patio pad, so you're lucky to get 4"

They make great vertical load fasteners, since I'm talking about pool garbage here say the slide would do great set with Hilti's... But that load is always pressing down and there's little side to side or pulling (shear) load. A springy diving board produces a strain at that fastening point that increases in direct proportion to the increase in distance the load moves away from that point. Turd needs things to do, maybe he could set that function up.
 
#4 ·
all about torque about a point! no more difficult that multiplying your foots and your pounds! that means it's proportional! just like a see-saw (spelling?)

if i understand the situation correctly:
torque applied to end of board (fata$$ x length from point of simulated rotation[leading edge of mounting base somewheres]) = torque applied at the fastener(s) in question [from that same originating point described earlier]).

i.e. bigger fatt-a$$ jumping on board is proportional to a bigger shear experienced along the annulus on the bore hole that the fastenner/epoxy are in!

another i.e. since we're multiplying fass ass's weight time the distance away from your 'point of rotation', we could also take a board twice as long with an a$$ half as fat and get the same result! Proportional!
 
#5 ·
I did some simple math using a fall calculation and a lever calculation. A 200lb man jumping 2 ft in the air at the end of the board should be around 7500lbs of force at the diving board. I wouldn't trust that in a 4" slab.

I am pretty positive that my calculations are off but it gives the idea of the force applied.
 
#10 ·
you know i got to thinking, since the board is a spring, and springs have characteristic rates, total jumping force could be theoretically calculated by measuring the time it takes the board to lift the fat-a$$ from bottom of stroke to mid stroke (1/4 of a total period) U use the spring constant if one exists (or can be calculated) to derive the force.

another thing we could do, we could simply measure the acceleration (guesstimation might be close enough) and then since force = Mass*Accelleration...

OR we could just get an accelerate mounted on the end of the board. BAM done.

ok i'm done now
 
#6 ·
lol if he's got some monster quads, calves, and really utilized his ability to 'sling' his torso & arms like in a weighted clean/jerk headed to the sky, with diving board springing back at you... you can put a lot of force on there!
 
#7 ·
any whoo, just that 200lbs of fat standing still on the 8ft mark of a board, where the faster being ripped up out of the ground is only 12 inches behind - all relative to the 'point of rotation' as it breaks loose - that's 8ft*200lbs = 1600ftlbs of torque, and coincidentally (because it's only 1 ft) 1600 pounds of force pulling the fasteners up out of the ground.
Now, MAKE HIM JUMP! sh#t escalates quickly!
 
#9 ·
So yeah, my calculations set the pivot point at 5' of board and 3' on the ground. And that's just 200lb falling. Not to mention jumping back off of it.

Turds math is way better than mine but it's quite a "load" put on the 3 little anchors
 
#12 ·
So with all this math and such. I was getting at was, make sure you have your camera ready when he goes to try it and ends up pulling the anchors out and everything ending up in the pool
 
#14 ·
This stuff...
If im reading the tech sheet properly it says that a 5/8" bolt rod drilled in a 3-3/4" deep hole can stand 5665 lbs of tension in 2500psi mix and is rated to not shear until 12200 lbs... I downloaded the PDF and i doubt your buddy is using this lol so please hide a camera and post the video [emoji631]
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#16 ·
With or without the lovely beard? I agree, 2500 is lightweight especially for a pool deck, its more like a grout... the chart specs all the way up to 6000 psi and the more dense the concrete, the better hold power for the injectable anchor.. I'll see if I can zoom in on the chart and post it up...

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#17 ·
maybe a click and zoom? Best I can do from the phone...

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#18 ·
we have mounted houses in rock with the epoxy and redheads...they hold pretty friggen good. remember the pullout factor is per redhead also. What the engineers do fail to include in the calcs is what we would refer to the pendulum effect. Big woman hits end of board, compressing it toward the grand, creating the pullout factor, however as the boob swing catches up with the frame there is an extra pullout factor creating slightly more stress in the pullout area. The same pendulum effect helps to propel her higher in the air than a male with the same size buddy, unless he has matching size manboobs.
 
#19 ·
Yeah, how does the oomph factor factor in? Like say Santa Claus goes and runs off the end much like a gay stepchild running for the ice cream truck. He's in his 60s and to call him a 'big guy' would only referring to the physical volume his mass takes up. He's got 20lbs on me but it's not at all a 20lbs you'd be proud of bragging about. His 280 rolling off the end of the board and plopping in the water HAS to be a weaker force than my lesser 260lbs but more intense load in the final seconds when prior to the very end of the board I take that forward hop, bounce, and SPRING up/forward/out.

No?
 
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