Monday, January 11, 2016

Captain America Ball Chair Project Part Four

The days have been flying by here at the workshop now that the holidays have come and gone.  I have been making steady progress with the Captain America ball chair project so I thought it best to get everyone up to date on where I am with everything.

This week I want to show you the progress that I have been making on the base assembly for the project that will be similar to what you see in the image above. This was an early rendition of what I had planned and like anything I design and build changes sometimes need to be made to make the design work better and make the assembly easier to put together.

In this underside view of the base the outer face of the base was designed to be one inch thick.  It looked good at the time but in reality would be a pain to create. Instead I will have a similar looking base but it will only have an out skin that is a quarter inch thick.  This will be strips of 1/4 inch foam that are wrapped around the eight leg supports on the underside of the base.  It will look similar to what is pictured here but will be easier to make in the process.
In this portion of the project I started work on the assembly for the base unit for the ball chair.  This base is simple to look at but has a lot going on for it.  The slot in the top of the dish shaped top is where the ball section of the chair will be mounted. 
This dish section of the base is made up of several different pieces and will take some time to put together properly to get it to work correctly in the base assembly.

The underside of the dish section of the base shows some of the different shapes that are cut out in the assembly as well as the mounting points for the bearing ring.
This bearing ring is mounted to the lower portion of the base and also to the upper dish assembly that is inserted into it.  This bearing will give the chair the capability to swivel when it is being used. 

The bottom of the lower section of the base unit shows an array of leg supports that will give the base a good strong framework to hold the ball chair safely when it is being used. The hole in the center of the assembly will allow assess to moun to the base to the base section of the chair.  The opening will also be used to route electrical power to the chair for accessories such as lights for reading.
I started the base construction with the a simple cardstock template of one of the leg supports.  I printed this off of my computer full size.

Using this template I traced the eight leg supports for the base on to one inch Styrofoam.
I then fiber glassed both sides of the foam panels.  I let these cure over night and then cut the parts out using my band saw.
Only two edges of these parts will be exposed once the assembly is completed so I removed a quarter inch of the Styrofoam and then filled this void with a mixture of fiber glass resin and micro-balloons.  This seals the edges of the foam and gives them nice clean edges.  You can see the white faces of these parts in the image above.

This section of the base assembly is the lower portion that will hold the azy Susan bearing assembly and will be where the leg supports will be added in the final assembly.  The lower base assembly is made up of one blue one inch thick foam panel that is 19 inches in diameter. Two pink rings make up the upper portion of the lower base and each ring is two inches thick.  These parts will be fiber glassed together when all the base components are combined and checked for fit.

In this series of photos is the assembly process that I needed to do to make the base plate for the upper portion of the base for the ball chair.  This 17.5 inch diameter disc of Styrofoam was first designed on the computer using free Fusion 360 software.  I then printed out a drawing of the part and then transferred the dimensions on to a piece of foam and cut it out using my hot wire table and my hot knife that you see here.  The hot wire table with my wheel jig made quick work out of making a perfect disc for this portion of the assembly.  Then I used the hot knife to cut out the key like opening that you see here.  This opening will allow access to the bolts that will hold the ball section of the chair to the base unit when it comes time to put these assemblies together.
This is a photo of most of the components that make up the upper portion of the base assembly. Again there is a blue circular base part.  Several more rings and semi-circle foam parts are then added to the lower cylindrical base.  The top blue circle of foam along with the two pink semi-circle parts are tapered toward the center to allow for a fiber glass dish to be mounted so that the ball assembly of the chair will mount perfectly.
This is a photo of the end cap for the ball chair where the star for the Captain America paint job will end up.  I fiber glassed this dome and then covered it with strips of Dacron cloth to make it nice and smooth for the steps that needed to follow in this portion of the assembly.
After the fiber glass had cured I covered a section of the dome with blue painters tape. 

I then laid the mating ring for the base assembly on top of the dome and traced out a circle to match the outer diameter of this ring.  This will be the exact size that will be needed for the dish for the base assembly.

Next came a lot of fiber glass.  I wanted to make sure that this portion of the assembly would be plenty strong for the base assembly.  I laid the fiber glass over top of the painter tape so that this part would match the dome but could be removed from the dome and not be permanently bonded to it. 

Once the fiber glass dish had cured again over night  the next step was to remove it from the dome. This took me about twenty minutes which really was not to bad.  I used popsicle sticks and paint stir sticks wedged between the two parts and after I had gotten a dozen or show sticks pried between each part they finally popped loose from one another. The dish shape is perfect and is plenty strong but I still needed to remove all of the blue painters tape.

With the use of a Dremel grinding cone  and an orbital sander I was able to clean up the dish and also get it nice an smooth for the next step.  Here you can see what the dish looked like after half of the painters tape had been removed.  The outer edge I did not bother with as this will be removed once the dish is cut to the correct diameter for the base assembly.
To make the ball chair swivel I am using a nine inch diameter Lazy Susan bearing ring.  This ring was quite cheap at only around $10.  It is perfect for the project as it is well made and the perfect size.  Also the fact that it can handle a load of 750 pounds is way more sturdy than what it will ever have to handle.  Works for me.

To mount the upper and lower assemblies of the base unit hard mounts needed to be made so that the bearing ring could be installed.  I glued up a couple of wood strips with 1/4 inch wood scraps to make up strips that were exactly one inch thick to match the Styrofoam panels they would be used in.  The wooden strips were then marked and drilled for wood screws and then cut into individual mounting blocks.
Eight wooden blocks were needed for this part of the assembly. The blocks were mounted to the bearing ring and then marked and cut further to match up to the circular openings in the bearing ring.

The foam disks that make up the base plates for the base assembly were fiber glassed on one side first.  Then Styrofoam was marked and removed at the center of the disks so that the wooden mounting blocks for the bearing ring could be epoxied into place for a perfect fit.  Once the bearing mounting blocks had cured over night again the assembly could proceed to the next step.
Here the next three pieces to this rather intricate assembly are ready for fiber glassing. In the photo above you can see the fiber glass cloth laying behind the dish, and the two foam disk parts. The bearing assembly was removed at this point as it was not needed and would be in the way at this point in the assembly.

Here is the dish assembly once again.  Before and after the fiber glass cloth had been wetted out .  The additional fiber glass cloth worked out perfectly and will make a simple task out of getting a nice smooth seamless inner surface for the dish.

Lastly I fiber glassed the two foam disk for the base assemblies.  This again was a simple task as I glassed over top of the now installed mounting blocks for the bearing ring.  I  checked for any voids around the blocks before the glassing was done.  Any that I had found I filled with the same resin putty mixture I  had used earlier in the assembly of the base leg supports.
So you can see that I've been busy working out the little details in this portion of the project.  I am really pleased with how things are going so far.  The bearing ring assembly works perfectly and to do the final assembly of the base for the chair should go smoothly with the hard work already completed.  Once I have this section finished I will start fiber glassing the ring sections of the ball chair to get them ready for assembly to each other and the base.  I'll let you know how all of that goes once I get further along.  Total time so far on the project not including design time is now at 51.5 hours. Great having it starting to take shape. Enjoy the photos and have a good one.


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