Weights
I want to do this but I couldn't find a cost effective way to start. So I'm going to try making concrete weights.
Weights
- Bar - $35
- Chicken Wire - $6.25
- Quikrete - $3.80 x2
- Nylon Rope - $4
- Clamps - $1 x4
- Paint $3.75
Total: $61
Plan
The bar is galvanized steel, which I will fill with concrete. The bar will be cut to 7ft. The bar should have a strong tensile strength while the concrete has a strong compression strength. I'll put two clamps (plus probably duct tape) as weight stops. The other two clamps will be used to hold the weights on.
Cast weights in 1, 2, 4, 8, 16, 32 lb plates. To cast a weight, measure out the correct amount of dry concrete. Make a mold from cardboard and plastic. Build an insert from chicken wire that is about the size of the mold. Wrap the outside in nylon rope, and add nylon rope spokes. Put the insert in the mold and cover with wet concrete. Let set for a few days. When the weight is ready, remove from the mold and paint it.
Power Rack
Total: $44.05
Basically, this. The big change I'm going to make is that the two sides will only be loosely held together. That way if I need to take it apart, the two sides can be moved separately. I have the wood I need to build the rest of the supports and a basic bench. I also have a bunch of paint left over.
Grand Total
$105
Build Log
Actual cost: $107
Quikcrete
Quikcrete: 3/4C = 323g 1lb = 435.5g 1C = 14.44 in^3 431.7 g/c 29.9 g/in^3 14.57 in^3 / lb
Plastic pipe
408g 1 5/8 in outer diameter 24 5/8 long 16.6 g/in
I'm going to start by casting a 1lb weight. It will take a while to set, but if it doesn't turn out, I can throw it out without worrying. And it will give me some information about working with the concrete.
The math for a plate is
v = h*π*(o^2-i^2) o = ( (v/h*π) + i^2)^0.5
For 1lb plate
v = 14.57 in^3 h = 1 in (chosen arbitrarily) i = 0.8125 in Which gives o = 2.3 in r = 14.45 in
I want the diameter of the plates to increase linear, and will adjust their thickness to fit. A 64 pound plate with a 15in diameter would need to be 5.3in thick. going up to 16in drops it to 4.7in, 17in:4.14. I think I'll go to 17in. So I'l leave the 1 lb plate at 2.3in r, but for 2lbs, we'll go to 3.5in r and increase by 1 in every step up. Checking the math, a 32lb plate will be 15in wide and only 2.7in thick. Pretty good.
Plate Diminesions
- lbs radius width
- 01 2.3 1.00
- 02 3.5 0.80
- 04 4.5 0.95
- 08 5.5 1.25
- 16 6.5 1.78
- 32 7.5 2.67
- 64 8.5 4.15
I'm designing the width bar for 600lbs, not that I'm sure the bar could handle it or that I'll ever get there. That's 300lbs/side. Plates 4x64 + 32 + 8 + 4. So the total width would be 21.5in. But is that the widest? What about 3x64 + 1 of every other? Nope, 20.9 in. I measured my grip and 45in felt wide. So the bar needs to be 88in long (7ft 4in).
My first 1lb weight, well... Too watery. Should be 2T of water per lb of dry concrete. I set everything up to be watertight, and that's not really necessary or good. And in doing so left all sorts of depressions in the surface (I did smooth them out later). I'm going to take some scrap plywood and sand it out really smooth and paint it and mark down all the weight radius's. I can just work right on there and clean it between. I can use cardboard with a layer of duct tape around the outside. I'll also cut some scrap wood for imprints. My fingers are about a 1/2" wide, so I want a 1/4" gap about 2" deep around the outside of each plate. I want the weight pressed into each side. And the decorative spokes.
After getting everything set, put the wood up on some 2x4 chunks and put one of the power tools up against it to make the whole thing vibrate. That will help it settle.
Full set is supposed to be 28 days. For the bar, I'm assuming it will be much longer. But for the plates, I need to wait at least that long to paint them. Also, concrete should be kept wet for 5-7 days, so I'll need to go spray them down occasionally.
It's hard to get the weight just right and it's hard to get the plates round - so go over by just a little, then sand the plates round and to the correct weight.