How much sand do you leave over the casting I lifted the sand on one today it was 11/2 inches of sand over it The other side has a 1/2 inch angle Thanks Todd
It's a hydraulics problem: an object with a fair bit of surface area being fed by a dense material like iron with a head height is going to produce an up force. You need G or F clamps or weights to counteract the lifting. Edit: At first I thought you had 11.5 inches of sand over it, that much head height would produce a fair bit of pressure.
On a wood flask it is very easy to simply use a piece of 3/4" plywood across the flask on either side of the sprue. Screw it down to the flask with a single drywall screw on each side of the flask. I usually use two pieces with one about 4 or 5 inches wide one on each side of the sprue. It would take hundreds of pounds of pressure to lift each piece of wood. I also screw tabs of 1/2" plywood on two or four sides of the flasks bridging the cope and drag. Again a single screw into the cope and one into the drag on each tab provides enormous resistance to lift of cope off drag. Quick, easy, and effective. I also like the idea that the tabs and boards are low-profile so that they do not limit easy access for pouring. Denis
Thanks The box is only 7INCHES SQUARE 1 1/2 tall The parton was casting was all in the drag 1/2 thick and 4.5 square
I did a rough back of the envelope calculation: if you had a 1 square inch runner feeding that 4.5 inches square casting then that's more than 20 times the surface area so the hydraulic force is 20 times the head pressure of cast iron at 1.5 inches high: roughly 7.5 lbs of up force assuming cast iron has a specific gravity of 7. You should get a collection of steel or aluminium plates to put on top of your moulds and then weight or clamp down to prevent the mould from blowing out.
I don't know about everyone else, but I've never made a flask out of wood smaller than a 1 x 4. Usually rip the drag down to 2 1/2 to save sand and weight. The only thing in the drag is the runner.
