has anyone out there made these using a "swiss ball" or gym ball, just wondering if the ball was cut off neatly from the dried concrete whether it could be rejoined using cable ties to make the next one.
gpg58,
May 12, 8:04pm
Not done it, but i would have thought you would make a mold using ball inside an upper and lower frame, then separate to remove ball, and simply refill with concrete using a release agent on mold (even glad wrap would work).
krames,
May 12, 8:24pm
make a box (30mm larger than the swiss ball). centre the ball in the box , drill a few holes in the box. pump expanding foam into the box (this will make a mold) let the foam harden . cut the box and foam down the center remove ball strop or clamp the box tight (put a release agent on the mold) pour a viscous pour of concrete into a hole in box,tap box to remove air bubbles. let set remove strops/clamps =1 concrete ball repeat
bill1451,
May 12, 10:25pm
yea the good old space invader foam, thanks for that ,will certainly try it.
also filling a ball with concrete would not end up round, also due to weight.
cinderellagowns,
May 13, 7:53am
OK I have to ask - what do you do with your big concrete balls?
krames,
May 13, 10:12am
gpg58 fair call. you probably will get a degree of warping I suggested this method as it is achiveable for a compent diyer. Another method that requires a fair amount of skill would be to get 2x 250 thick pieces of timber. set up a router on a piece of string dead center above and rout out the curve to match the ball=a long process but
bill1451,
May 13, 6:15pm
I tell ya it makes walking very difficult at best and worst painful. Nah yea, give it a go, despite all the naysayers, I have a secret ingredient to add. make a few of different sizes, bigger ones more suited to larger gardens, cast in a thread for lifting eye, with some sort of winch off a trailer for delivery.
bill1451,
May 13, 6:20pm
that would be an interesting exercise, how would laying fibreglass and resin go.
gpg58,
May 13, 6:29pm
sounds ideal. Another thought i had, was make mold, but for making actual balls support a smaller ball (cheap) inside mold(perhaps use foam), and fill, which would give a hollow much lighter product(you would need a new small ball each time, and to fill support holes once foam removed, - or use as connection points for a water feature) Or perhaps you could deflate inner ball and remove thru hole?
bill1451,
May 13, 7:43pm
yes my thinking as well, obviously requires a bi thinking outside (in this case outside the sphere)or even a series of plywood squares with circles cut out smaller than the diam of the actual ball nto give support on the bottom half. weight of concrete 130 to 150 Lb per cu ft.
bill1451,
May 13, 9:27pm
just looked on u tube, make 2 hollow half spheres, say 30mm thick and when they dry glue together with 2 pot "hume bond" or similar. some are plastering gym balls with a mix of some sort of mesh, but this wastes a ball each time and would quite time consuming. think I,ll stick to the expanding foam idea and make in two halves.
the-lada-dude,
May 14, 7:55am
Well I gotta ask the question .
cinderellagowns,
May 14, 12:45pm
Yeah nobody has given me an answer yet (other than the obvious joke). I really am curious as to what the concrete balls are for. Giant game of marbles? Massive "unsteal-able" globes for an outdoor geography themed playground? Art installation about the futility of life on this small planet in the middle of a vast universe? Medicine balls for the ultimate tough guy gym?
ira78,
May 14, 1:51pm
Well, let's see. If he makes a 500mm ball and paints it yellow as the sun then he'll have to put the nearest star. Where is my calculator. Let's see that would be 1/2,782,032,000 scale So the nearest star would be 13,600km. So from Wellington would put the nearest star about on the outskirts of Detroit. Closer than I thought.
oh_hunnihunni,
May 14, 2:50pm
Why not add a bulker to the concrete mix to lighten the finished ball, a la 'hebel' mix? Plastic pellets maybe, or waste glass pellets?
bill1451,
May 15, 7:30pm
just google it Cindy, mostly used for a bit of "out there" landscaping, small balls for small gardens, bigger balls for bigger spreads. and with different finishes they look quite effective. Smaller ones could have a hole through them and threaded on a rod for that vertical look.
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