I'm building a radio-controlled soccer ball. The electronics will be installed in a hamster ball since it's rigid, comes apart in halves, and is smaller diameter than the soccer ball. It will be gearmotor driven, not hamster driven. Anyway, I need to cut the soccer ball in half so it slides over the hamster ball. I cut out the air bladder and then filled it with expanding foam. Then I planned to cut the ball in half, and carve out the foam just enough so the hamster ball fits. But the foam cured wonky and there are flat spots on the ball. I'm toying with making two rigid frames to keep the ball spherical, then cut it in half, then add something to the insides of both halves, then remove the exterior frame. Any ideas?
Can you fill the ball with foam under pressure before you cut it in half? i.e. squirt foam through the valve hole and use the pressure of the expanding foam to keep the ball round? (Will the foam "set/harden" while inside the ball?) Alternatively, mix some fiberglass resin with catalyst and squirt into the valve hole, then rotate the ball to ensure the resin coats the entire inside while it hardens, then cut in half. In both cases, you'll need to glue the ball to the "hardened" bladder after you cut it in half.
I did the foam idea. It seemed to work well except that it didn't form a perfect sphere. The resin and catalyst idea sounds like a good idea.
How about using an inflated ball to make a mold, then suspending your motorized widget in the middle of the mold and casting something like Nerf material around it? It'll look like a soccer ball, but when the widget craps out you can cut it out, repair it, and easily cast it into a new ball.
I would think it you're going to fill a soccer ball with foam, you'd need a vent to let the air escape allowing space for the foam.
Just use real foam. Get some ferm enough to hold the ball tight and hallow it out for the hamster ball and stretch the soccer ball over it. The more foam you stuff in between the stiffer it will be and the right foam will give it some bounce.
I've been trying to make weighted medicine balls that bounce. Tried a pumping 4 lbs of urethane glue into a basketball followed by some air and spinning it by hand while it dried. Didn't work, it is a very odd ball when it rolls.
Thanks for all the ideas, guys. I think I will inflate the ball just enough to get it round and then glass/resin the outside to make a mold. Then cut it in half, then double-side tape the ball, in halves, back into the mold. Then I can build up the inside, with foam/epoxy to the outside diameter of the hamster ball.
What is your radio-controlled soccer ball going to do? Will it have wheels? Or a motorized flywheel inside so it rolls? Please post a video when your finished.
Just roll Mostly to screw with people. It will have a gearmotor drive and weight-shift pendulum for steering.
