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.

Completing the Horseshoes

The next step on the horseshoes was to skin the edges with styrene. I used the same technique I used on the legs, attaching the styrene with a 2-part epoxy. I used some clamps and painters tape to hold it in place and worked one section at a time.

Be careful with the end of the styrene strip that isn’t glued down yet, you don’t want to do this…

Fortunately no harm was done in this case. Here is the styrene taped up all the way around. I left the piece long and trimmed it when everything was dry.

I was having a hard time getting the bottoms of the two square holes clean, so I decided to glue in some pieces of styrene to give the bottom of a pocket a clean finish. The other hole was large enough that I was able to get it smooth with some sanding. Here is the complete horseshoe with a couple coats of white spray paint.

Horeshoes Continued

A while back I showed how I made the segments for form the should horseshoes.

The next step in making the horseshoes was to glue these up. Once again I build a jig to help with this process. The jig is composed of a piece of plywood with three 2x2’s screwed to it which forms an area that is exactly the size of the horseshoes. This allowed me to stack the four layers and be sure they were perfectly aligned.

I placed the first layer, and then applied a coating of wood glue to the back of the second layer, stacking it in the jig. I repeated this process with the other two layers. Once this was done I screwed a piece of scrap plywood to the plywood which acted as a clamp.

The next step was to cut the pockets into the surface of the horseshow that will hold the shoulder details. This is the process I used to cut them, but I was not entirely happy with the results I got from this. It required a lot more hand working of the cut outs to get them to look good.

I made these cuts using a router with a straight cutting bit and a guide collar. I made  template out of luan plywood that would guide the router. I didn’t want to screw the template directly to the horse shoe so I screwed some blocks down to my workbench in various positions to firmly hold the part and then screwed the template to one of these blocks. Since this was a deep cut I made multiple passes to make the cut.

It’s been a while since I made these so I can’t remember exactly how I did the square holes. Since there is a small hole in the bottom of each one I may have started the hole using a forstner drill bit and the finished it with the router and template. I did make a template to cut both of the square holes with one template.

Once the router cuts were complete I used a chisel to clean up the corners and did a lot of sanding and patching to clean up the holes.

Shoulder Hubs Part 3

 

The next step in making the shoulders hubs is to drill the holes needed to mount the hub to the leg. This required a bunch of different size drilling operations that all need to line up perfectly when they are done. To do this I started by drilling a small hole in the inner leg layer that will be right in the middle of where the hub will go. On the back of the leg piece I used a compass to mark a circle for where the holes will go and then marked the position of six holes even spaced around the circle. Next I used a nail to get the hub aligned with the leg, and then screwed both sections of the hub to the leg. With everything screwed together drilled small holes all the way through all three layers to mark the position of each bolt.

The first drilling operation was to drill shallow holes using a forstner on the back of the leg to accommodate the flange of the t-nuts.

Next I drilled the holes for the body of the t-nuts. The body of the t-nuts is a little larger then the bolt so be sure to measure them to get the right size drill.

The next holes were the large holes on the inside layer of the hub. I made these large enough to accommodate a socket wrench to tighten the bolts. Next I drilled the bolt holes in each larger whole and through both layers of the hub.

The bolts I am using to hold the flange on are not totally flush with the surface of the flange so I drilled some very shallow holes on the other side of the flange to accommodate this and allow the to sections to come together tightly.

I did some reading to see how others mounted the flange to the hub and I found that a lot of people used a metal plate on the back instead of washers. I am not sure what the advantage to this is, but I decided to still do it that way.

For the metal plate I used what most people seem to use, a cover plate for an electrical box. I started by marking the positions of the holes on the plate and drilling the holes. As always I put marks on the plate so it ended up back on the same hub and in the same position.

The plate needs to fit within a hole in the leg so I needed to trim the plate a bit. Since the plate already had rounded corners I only needed to do a little bit of trimming. I did the trimming with a hand held jigsaw with a metal cutting blade.

To hold the hubs to the leg I installed T-Nuts in the holes in the leg layer. The t-nuts have prongs that hold them into the wood, but since these will eventually be inside the leg and in-accessible, I took the extra precaution of securing them with epoxy.

There will eventually be some more assembly work on the hubs but I won’t do that until I am closer to doing the final assembly.

Shoulder Hubs Part 2

 

The shoulder hub are a little tricky to build. They require quite a few drilling operations and some of them have to be done in a specific order.

The first step in building the hubs is to cut the disks. These are made from 3/4 plywood and two are needed for each leg. I cut them using my router table and circle jig just like I did with the frame disks.

Once the disks are cut the next thing to do is mark them so you know which ones go on each leg and which is the inside layer (nearest the body) and which is the outside layer (nearest the leg). As I have mentioned before, if you are really accurate with your drill holes, which one goes with which leg isn’t important, but since these operations sometimes aren’t as accurate as we want it’s better to keep things matched up.

Next I worked on mounting the flange to one of the disks. I didn’t want to measure to the outside of the flange since it isn’t machined and is a little inconsistent.  Since the threads in the center are machined it was a more accurate place to make measurements. I put a nail in the hole in the disk and used calipers to measure around the nail to be sure it is centered. Once it was centered I marked the position of the holes. I also put a mark on the flange and disc so they could be put back together in the right orientation.

With the holes marked I drilled them with a drill press.

On the other layer I needed to cut out a 3/16” deep area to accommodate the bottom part of the flange. To do this I used a fly cutter in my drill press to make a template. This cut out doesn’t need to be perfect so I made the template slight larger then the diameter of the flange to be sure it would fit properly. I marked the position of the flange on the disc and then screwed the template on. Finally I used a router with a guide collar to cut out the area within the template.

With that cut-out complete I used a 1 5/8” forstner bit to drill a hole through the center of the disc to accommodate the smaller portion of the flange. The area where smaller part of the flange meets the larger part is slightly rounded so you may need to file the inside edge of the hole so it will all fit together properly. There was also some raised lettering on the flange which I had to grind down a bit to make everything fit. Here is the flange sandwiched between the two discs. If done properly the disc should fit tightly together.

Shoulder Hubs

 

The next thing I want to show is how I built the shoulder hubs. There seems to be two parts on a droid that are referred to as shoulder hubs. The first is show here, that silver part within the shoulder horse shoes:

The part I will be talking about in the next couple posts is this one, the hub that attaches the legs to the body.

After doings some research I found that attaching the legs to the body was one of the trickier parts of building a droid. The legs need to be able to rotate so that the droid can be switched from two leg position to three leg and when in two leg position all the weight of the droid in on this connection point. One of the most popular ways of doing this is what is called the “gas pipe method”. To do this, two different size steel gas pipes are used, one screwed into a flange on each leg and then slipped inside each other. The hard part turns out to be finding pipes that will slide into each other but not be to loose. You will find that these pipes often have a ridge down the inside of the pipe that prevent them from filling together.

I eventually found pipes that will work at Home Depot, but did a slight variation of this method. Instead of using two different size pipes on the legs, I used the same size, and then used a third large pipe to connect them together. Here is what the finished product will look like.

Here is a diagram of the hubs I built. It starts with a metal pipe flange that the pipes will eventually screw into. The flange is sandwiched between two plywood discs and bolted to the one that is closest to the leg. The entire assembly is then bolted to the leg with t-nuts installed on the leg. In my next post I will start to describe how I made the hubs.

Horseshoes Part 2

In my last post I showed how I created the the tempalte for the horeshoes, in this post I will show how I used the template and a pattern cutting bit to cut the actual parts. The first step was to cut a series of blanks out of 1/4” MDF and to trace the pattern on to them.

I then used the traced lines to rought cut the parts on the bandsaw.

Next I screwed the template to the first of the blanks. The template doesn’t need to line up perfectly with the traced lines as long as there is wood from the blank sticking out all the way around the template.

Cutting MDF puts out a lot of fine dust so I wanted to take some precautions before I made the cut. I used some cardboard to make a dust catcher that extended all the way over the cutter. I cut a hole in the back of the dust catcher to put the hose from the shop vac and tapped everything down to the router table. Even with this I still used a dust mask while making the cuts.

In my post on cutting the leg parts I talked about the importance of using a guide pin to start cuts on a router table. In this case I found the pin was really getting in way so I chose not to use it. If you don’t use the pin you just need to be very careful when you start the cut. With everything setup I cut all the pieces.

The final operation I did on the horeshoes for now was to form the ridges that are along the inside edge. To do this I used a pattern cutting bit in the router table just like I did to cut the shape. The difference for the ridges is that I replaced the bearing on the bit with one that was slightly smaller the the diameter of the bit.

I then set the depth of the router so the cut will be exactly half the thickness of the horeshoe pieces. Since the groove is only half the thickness of the part the template isn’t needed, you can just run the pieces without it and you will get perfect groove along the edge.

When stacked together you get the ridge effect.

On the horeshoe part nearest the leg I made this cut all the way around the piece. This provides the groove that is between the horesehoes and the leg frame.