Making Accumulator End Caps

Posted Sat, 03/27/2010 - 17:16 by Brian

This post describes how to make the end caps for a cannon accumulator. Because of the unusual shape of Nassau's accumulators the end caps I made a larger than would normally be needed. However, the exact same principles hold for other accumulator end caps - the only things that change are the diameters.

Disclaimer

This worked for me - it might not work for you. I do not describe how to use these tools safely. For example, the pictures were taken with chip guards removed. I am not saying you should remove them. It is your responsibility to use your tools safely.

It is your responsibility to determine if the parts you make are safe to use. It is possible that this design is fundamentally unsound. I am not an engineer and can not claim this design is safe to use.

Copyright

No one has permission to copy the information contained here. Please feel free to link to this page but do copy its contents or embed it into your site.

Part of Series

This is one post of a series describing in some detail how I made the cannons for my battleship SMS Nassau. Here are links to the entire series (including this post):

Materials Needed

These parts are probably most easily made using 2.5" round PVC (type-II). However, because of the combination of tools I have (and don't have) I use 2.5"x0.75" rectangular bar stock.

Step A: Make Blanks

The first thing I do is make the blanks that I will make into caps. I basically rough out some 2.5" diameter cylinders out of the 0.75" PVC (type-II) stock and then turn them down into 2.24" cylinders on the lathe. Each of these blanks will become two caps.

If you are making more than one part you should repeat this step for all of them before moving onto the next step.

Step B: Turn Lips

To increase the area of contact for the PVC cement I turn a lip that will be pressed into the accumulator bodies. I do this by turning 0.2" of each end of the cylinders we made in Step A down to 2.0" in diameter.

If you are making more than one part you should repeat this step for all of them before moving onto the next step.

Step C: Reclaim Volume

I do not believe that the caps need to be 0.3" thick (but I am not an engineer) so I remove 0.1" from the center of each end of the cylinder. Be careful to leave at least 0.1" rim around the edge.

If you are making more than one part you should repeat this step for all of them before moving onto the next step.

Step D: Cut in Half

The reason we have been working both ends of the cylinder is we are making two caps. Its now time to separate them. It is important that you cut the cylinder in half very close to the center. Otherwise one of the caps will be too thin to use.

Depending on the size of the caps you are making and the tools you have you may be able to use a parting tool for this. Below is an old picture I had where I used a parting too to separate the caps. Now I generally cut part way through the cylinder with a parting tool and then use the slot to guide a band saw the rest of the way through.

If you are making more than one part you should repeat this step for all of them before moving onto the next step.

Step E: Face Part

You can now face each cap so that its overall thickness is 0.3". This will allow 0.2" of depth for PVC cement and 0.2" of PVC to resist the internal pressure.