Shoulder Hydraulic

The next piece I needed for the shoulder was the shoulder hydraulic.

I made this is three parts, the round central shaft and the two blocks at either end that hold it to the shoulder. To make the shaft I turned to a pretty specialized piece of equipment. This is a Unimat mini machine lathe. I rescued this one from my father’s basement where it had been water damaged. It took a lot of WD-40, rust remover and scrubbing to get it taken apart and cleaned up. I also got replacement belts from Toms Tool Store. With this tool I could have made the shaft from metal, but I am more comfortable with wood so that is what I went with.

I started with a dowel that matched the largest diameter of the finished part. Using the measurements of the plans I marked the location of each section that needed to be cut. Once the piece was mounted in the lathe I spun the dowel and marked the lines all the way around.

Next I used a couple different cutting bits to cut each section. I use a pair of calipers to check when the correct diameter had been reached.

Here is the piece after the lathe cuts had been made. For now I did not cut off the ends because I needed to put it back in the lathe later for one more cut.

The hardest part of making this was the knurling around the one section. I tried a couple way to do this and the technique I ended up with produced a pretty satisfactory result. To start I used a CAD program to general a series of parallel lines with the spacing I wanted for the knurling.

I used spray adhesive to glue the pattern onto the part.

I also made a block to hold the part while I was cutting the knurling. When making the cuts the tools are going to tend to come off the end of the knurled area, so I wrapped some electrical tape around the part to protect it.

To make the cuts I started with a straight edge and an X-acto knife. Next I used a sharp dental pick to widen each cut. Finally I used to a diamond shape needle file to get the final size and shape of each cut.

With the knurls cut and the rest of the paper pattern cleaned off I put the part back on the lathe to make the groove in the middle of the knurled section.

I my next post I will show how I finished it.

Shoulder Buttons

In this post I will show how I made the shoulder buttons. Like a lot of these detail parts you can buy resin or aluminum versions of these online, but one of my design goals was to build as much as I can from scratch.

I started by cutting a dowel into pieces the correct thickness. I then used a centering tool (see my last post) to find the center of the dowel. Normally I wouldn’t worry about the angle between the two lines but in this case I also need them to locate the small holes at the edge so I made sure they were 90 degrees to each other. Finally I marked the centers of the edge holes.

I put the dowel in my clamping jig (again see my last post) and drilled the two edge holes.

I also drilled a larger hole which I will need for the raised button in the center.

For the button I used a premade wood plug. These were pretty close to what was needed but the actual buttons are a little more cone shaped and these are a more domed.

To fix this I drilled a small hole in the center of the button and attached it to the end of a dowel with a nail. I then used my small bench belt sander to refine the profile.

Here is it looked like before (on the right) and after (on the left).

Here is the button glued into the base part.

Once the glue was dry I drilled the center hole. Here is the final product with a couple coats of grey primer on it.

Working with Dowels

There are a couple details on R5 that I made using wooden dowels. When making these parts I needed to drill holes in the center of the ends of dowels. This required a couple special tools that I will talk about here.

The first thing I needed was way to mark the center of a dowel. Here is a store bought centering tool that I got as a hand me down. It has a V-shaped slot on each side that you put the dowel into and then mark along the straight edge. You need to mark at least two lines to get the center, but I always mark a third just to be sure that I didn’t mess up one of the other two lines. You can buy one of these from here, among other places.

Another option is to make your own centering tool. This is made with two pieces of plywood glued together at a right angle and a piece of style cut with a 45 degree angle. For this to work properly you need to be sure the angles are as accurate as possible. Be sure the two pieces of plywood are square to each other, be sure the styrene is exactly 45 degrees. This is used the same way as the store bought one.

 

The second thing I needed was a way to hold the dowel while I was drilling it. To do this I started with a piece of 1”x3” pine and drilled holes for each size dowel I would be drilling. I then cut a slot through the center of the holes with a band saw.

To hold the piece, I put it in the appropriate size hole and then clamped the end of the board which squeeze it tight around the dowel holding it in place. Before drilling the dowel I used the centering tool to mark the center and then used a nail to put a small guide hole at the center.