Now that our leg assembly is built, we will need to add a clevis mount to the bottom of the rear brace as shown in the photo above. To achieve this I cut the top off of a 1" X 2" piece of tube steel and then chop off 1" of the larger bottom section. I rounded the top edges and then drilled a 1/2" hole through both pieces now sticking up to hold the 1 1/2" piece of 1/2" solid steel rod I will be attaching my air cylinder to. In this photo on the right you can also see two 1/4" holes drilled in the bottom of the U, and squared off, allowing us to attach this to the leg brace with 1 1/2" x 1/4" carriage bolts. Now we make our connector pin for the air cylinder from the steel rod and drill a 1/4" hole in the center and then more hitch pin holes on each end as we did for the knee axles. Once again, space them to fit snug to the clevis with one washer on each side to minimize wear as the pin pivots in the mount. Mount this on center to the brace. 

   Next we turn to the mounting bracket for the skeleton so we have a place to put our leg assembly. I started with a 2" X 4" piece of steel tube that I cut to 4" long. Next I made one cut lengthwise on both sides, revealing two identical mounts that are 2 3/4" tall each. I recommend de-burring all of your steel pieces as you go for safety.  Now clamp these two pieces back to back to make sure your hole will be perfectly level and measure 2 3/4" up from the bottom to drill your 1/2" pivot rod hole on center to the bracket. Finish your brackets by drilling two 5 /16" holes through the bottom so they can be bolted to the top of the seat box. Now cut a 14 1/4" length of 1/2" solid steel rod to slide through the bracket, then through a 1/2" flat washer, then the leg and over to the other leg and bracket. Shown here are some collars I am using on the ends of the rod to keep it nice and snug against the brackets to prevent side to side movement. Hitch pins could have worked here as well, but the ease of using the collars appealed to me. Next we need to get this attached to the chair seat so we can get on to the torso of our condemned creep.

   This animation will be rather demanding on the chair that we are bolting him to, so it is important to insulate the concussion of his movements from distressing the wood or the joints. I decided on mounting him to the chair with steel springs to absorb this constant abuse so the chair should stand up to years of use. At first I used a lighter weight spring than shown here in the photo and it simply didn't do the job, so I recommend you find a Century spring #C-892 or similar. This is a heavy duty spring that has an inside diameter of 3/4". This comes into play in a moment. We will need to cut off 4 pieces 3/4" long each as shown below. Since our 5 /16" bolts are no where near 3/4" diameter to keep the springs from migrating off of the washer we will be placing between the spring and the wooden seat surface, we will need some sort of spacer. I found that standard 3/8" rubber air hose was not only the right size outside, but would fit snugly around the bolt to keep the springs right in place. You will need four of these cut to about 1/2", eight 5 /16" flat washers and four lock nuts. The bolts are 5 1/16" as mentioned and 2 1/2" long. Also, something not shown in the photo above are some rubber washers that I decided to use for further insulation of all of the concussion pieces that would be mounted to the chair such as the air rams and of course the skeleton. Called 5 /16" Tank Bolt Washers and made for your toilet tank connection, you can find these in, you guessed it, the plumbing section of your local hardware store! These will be placed underneath the bottom washer below the spring to keep the steel washer from coming into contact with the wood which would eventually wear through if left in contact. Hopefully with this layer of belted rubber this will never be a wear point on the chair. Remember to also place one of the rubber washers between the flat washer and the wood underneath the seat as well. Here is the spring assembly just before placing the leg assembly down to complete the attachment.  And here is how it will look fully assembled. It is important to note here that you will not be tightening the nut down on the bracket. Just bring the nut down until it is firmly seated so you allow the spring to do it's job to absorb the vibration. No part of this build I feel is more important than this connection, that's why so much time has been spent in it's discussion here.