Homemade Calf Raise Machine

My son likes working calves, but we don't have an easy way to isolate them. He's been doing standing calf raises with the barbell, and also one-legged calf raises while holding a dumbbell, but I wanted a way for him to really hit them.

I believe in the big, compound exercises, but machines are a great way to work muscles in isolation. A calf machine is a good example of this. So, still flush with success a year after constructing our power rack, we we decided to build our own calf machine. 

I semi-sketched out the plans, but most of it was in my head. The first stop was the local Lowes for the materials: 

The wood: three 8-foot 2x4s and one 2x2. We hand-picked the straightest ones. In the picture below, I've already cut two 36 inch sections off two of them 2x4s.
The hardware: One utility hinge (so far unused), one 6-inch carriage bolt (2 washers and 2 nuts), a 2-inch bore drill bit, and a pack of wood screws (#10 size, 2.5 inches in length). Not pictured (because I forgot to take a picture of it)  is a 24-inch length of 2-inch PVC pipe. You'll see that later. 
As I mentioned above, the first thing I did was cut two 36-inch lengths from two of the 2x4s for the lever arm:
I then cut two 32.5-inch lengths for the base:
Next up was four 16-inch lengths; these are supports and cross-pieces:
Lastly, I cut a 32-inch length for the lever post:
Here's the base assembled: the two 32.5-inch base pieces with the lever post and a 6-inch leftover spacer between them, with two of the 16-inch pieces fastened T-style at either end. My son screwed it all together using the wood screws and our battery drill:
Another view of the base:
Assembling the lever arm. We used a scrap piece to space the lever arms part, held the shebang together with a clamp, and fastened one of the remaining 16-inch cross pieces on one end. This cross piece will end up being the flat surface that rests on your knees for you to press up:

We drilled a 1/4 inch hole in the top of the lever post and the end of the lever arm (opposite the cross piece), then fastened the lever arm to the post using the carriage bolt:
Taking shape now. We fastened it on to check fit/length before using the bore bit to drill the hole for the weight bearing post.
We took the lever arm off and used the 2-inch bore bit to drill through them to make the hole for the PVC pipe to hold the weight. This was a pain, as the bore bit was only about 1/2 inch deep. So it was drill and then use a flat head screw driver to knock out the wood so we could drill more. We repeated this process until we got all the way through,
And here's the finished product. I ended up re-drilling the weight bar hole because the first one came out crooked and the weight bar was slanted. So I reversed the lever arm and redrilled the weight bar hole and the hole for the bolt at the end. If you look, you can see the old holes. 
Right now, the lever arm is held up with a simple stick. I've been brainstorming a better way to support the arm while weights are loaded/de-loaded and you position yourself. The wood is pretty hard on your knees; right now we use a folded towel for padding, but I've ordered some large sponges that we'll duct tape on.
More pictures coming in the next few days.... using it, the new supports and the sponges added.... stay tuned!

OK, some continued refinement. You can see in the photo above that we were using a stick to support the lever arm. Not the greatest, and we wanted something more stable, we we made support arms using the 2x2, some wood screws, 2 strap hinges, and some string. 

The supports:
One of the strap hinges (I used a total of two)
Attaching the hinges. They're attached on the outside of the bottom piece you put your feet on. 
One of the supports attached. 
Both supports on now!
But how do we keep them from flopping to the floor? String my friend. Some twine attached to the support and to the lever arm keeps the support from flopping all the way down to the floor. 
The wife puts the calf raise through it's paces.
All that's left is to attached the sponges for padding. The sponges felt a little damp out of the package, so we're running them through the wash and will let them dry before we put them on.
OK, finally done with the rack. It took a bit of tinkering, but we got the "padding" installed. You can see the picture of the sponges we used above; here they are again:
We had to cut the corners out because of the two support arms we installed. You can see the one of the sponges (the left one) shrunk a lot more than the other. Don't know why. 
Originally, we'd tried to use duct tape, but that was a not go. See, the thing it, the sponges compress and actually move a bit as you use the machine, so we needed something flexible. The result as an Ace bandage. The Ace bandage is stretchy and has some give, perfect for what we needed.
Here's a final view of what the padding looks like from underneath.
And that's it! 

We really enjoyed building our wooden calf raise machine. If you decide to tackle something liek this yourself, I hope our documenting our experience is helpful.