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ZB-1, ZB-2: Scratch Build Cylinder design for limited Production by Zero Bubble.

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  • ZB-1, ZB-2: Scratch Build Cylinder design for limited Production by Zero Bubble.

    Hello all,

    I decided last year that I would give the design and development of Sub kits a break for a year or so. I would spend 2020 fine tuning the kits I have, selling them and adjusting some smaller parts and
    just generally lifting the quality of parts, here and there. I am happy with how my latest design , the Delta has turned out and don't think I need to develop a new kit. I guess I'm running out of Russian boats that I like..

    I have received emails from people who want to know about the best cylinder to fit one of my boats. I have referred them to subdrivers and other vendors according to the needs that they outlined. However I have been thinking for some time about building a basic cylinder design that could complement the kits I have and make another option available for the market. I have decided to concentrate on one basic design that as much as possible will be interchangeable. The design will feature a single shaft stern end cap "ZB-1" (Zero Bubble-1) for the MIKE, BOREI and RESOLUTION and a twin shaft equivalent "ZB-2 for the PAPA and DELTA.

    I intend to go down the same manufacturing path as HWSNBN with regards to Casting the endcaps. I have been curious about doing this for some time. I think that over the past couple of years I have developed the skills and familiarization with this medium and what you can do with it. I realize that this will be low production and the cost of producing these castings is a fair outlay but we do this for the passion.I certainly do. I will be prototyping the endcaps out of Renshape. This is great since Hardrock (Scott) moved down to Nowra (south of Sydney) and left me with a stupidly be piece of Renshape. Thanks Scott, it's awesome!.

    I am still in the research phase of this project and have been watching HWSNBN's write ups on cylinder prototyping in "todays work" and " the subdriver becomes modular". I have especially been looking very closely at how everything to do with the shafts are done. I have spent and will continue to spend hours looking over parts lists for seals, o-rings, oilite bearings, bushes, shafts, motors and Polycarbonate tube. I have started ordering parts in bit by bit and started playing around with fit. I have also started doing the sketches to get my ideas right and looking closely at the ones HWSNBN has appear in some of his pics.

    My design will be similar to the arrangement I currently employ in my boats. It will use a pressurized system with a single cylinder, no partitions, a pump at the front and the water going to an isolated PVC type ballast tank further forward. A simple, old set up that works well. I am allocating about a year to develop these designs. To what level of detail I will go to with regards to internal components and layout I'm not sure yet. I will at least design and make enough to stop the water coming in from either end!

    There is an enormous amount of work to do, innumerable avenues I could go down. Any number of parts options i could take and truckloads of prototyping, testing and development. I am setting myself about a year to do this.

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    I don't think that contributions for this endeavour will appear as my regular friday night write up. Yep, my social life rocks.... It may be a bit more intermittent. It will be interesting to see what these two designs look like when I have finished with them.

    I will start getting into more detail of specifics in the next write up. I will certainly be throwing out the odd question when stumped.


    David H



  • #2
    Excellent, David. I stand ready to assist any way I can, sir.

    David
    "... well, that takes care of Jorgenson's theory!"

    Comment


    • #3
      Hello all,

      Thanks David, I am sure there will be lots of questions.

      I am awaiting poly carbonate tubing. I ordered it a while ago and will pick it up this week. I need it to finally work out the diameter of the end caps. Then I can really start to move forward. I have in the meantime turned some end caps to approximately the right size. I know the ID of the poly but have turned the end caps slightly big and will then put them back on the lathe to take off the last mill or two.

      I have been thinking about how to do the shafts geared or direct drive. I have decided to do geared for the single shaft endcap and a direct drive for the twin. The intention being that the user only needs to buy one cylinder with a common front end cap and then can swap out the rear end cap and tray depending on whether they are driving a twin or a single shaft boat. I am actually focusing most of my initial effort in the twin, I am currently using several materials to turn up and prototype lots of the small parts, Renhape, Brass and Acetyl.

      I may make two front end caps, a simple one which as limited features and a second one that will have a bracket to hold the 12v pump that I use for my ballast system.

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      I do have a question for you David.

      I have been thinking about some way of testing the watertight integrity of various prototype components at various stages and then finally the fully assembled assembly before committing to tooling and production. In order for this to happen I need to be able to assemble the prototype in such as way that it is sealed and that the components not only don't leak but also don't absorb water. My biggest query with this is with Renshape, If I were to assemble an end cap and test it would the Renshape absorb water ? potentially expanding ruining the end cap and other Renshape parts? I intend on sealing the Renshape with a resin, like what you do. Should I test it after this or not at all? Bad idea?


      Thanks,

      David h




      Comment


      • #4
        Originally posted by Davidh View Post
        I do have a question for you David.

        I have been thinking about some way of testing the watertight integrity of various prototype components at various stages and then finally the fully assembled assembly before committing to tooling and production. In order for this to happen I need to be able to assemble the prototype in such as way that it is sealed and that the components not only don't leak but also don't absorb water. My biggest query with this is with Renshape, If I were to assemble an end cap and test it would the Renshape absorb water ? potentially expanding ruining the end cap and other Renshape parts? I intend on sealing the Renshape with a resin, like what you do. Should I test it after this or not at all? Bad idea?

        Thanks,

        David h
        RenShape and water get along fine. The material is a very tightly packed polyurethane or epoxy foam (I use 'RenShape' as a generic term describing all 'dense machinable foam mediums) of the closed-cell type. Water will not migrate into the substrate.

        And I like what I'm hearing about your upcoming testing methodology, David. And your shop drawings are showing off some good, sound engineering chops, sir.

        Now, if you would only learn how to scribe without use of shovel and back-hoe. Your scribing work is, HORRIBLE!

        David
        Last edited by He Who Shall Not Be Named; 01-25-2020, 09:49 AM.
        "... well, that takes care of Jorgenson's theory!"

        Comment


        • #5
          One more thing about sizing your bulkheads. Leave all of them oversize. Lexan has a stupidly large margin of physical tolerance. Size your bulkhead master larger that the largest diameter of Lexan you'll ever find and make that your standard and what forms your tools. You will be required to lathe-shave each and every production casting to fit a specific length of Lexan.

          You wouldn't shake a freshly cast engine-block out of the green-sand and expect the cylinder liners to fit without some careful boring would you? No! Same with your bulkheads and Lexan -- you gotta machine things to fit. You got a nice handy-dandy, wonder-lathe: make the appropriate holding fixtures to fit your face-plate and the sizing work will go quickly.

          And that is that! And just one reason these things cost so god-damned much: the labor. And when you sell these things, don't be shy to get back the money you put into it as well as a king-size profit! If you don't, I will find you! (should be easy, all I have to do is head south-east and follow the smoke).

          David
          "... well, that takes care of Jorgenson's theory!"

          Comment


          • #6
            The Lexan tube outside diameter is it closer to tolerance than the inside diameter?

            Comment


            • #7
              Yes, at least from the German Vendors i know.

              Comment


              • #8
                Hello All,

                I finally got hold of the Polycarbonate tube that I want to use for my design. I ordered it a while ago and simply had not had to time to go and pick it up. In the mean time as you can see from the photos I had already started turning up Renshape end caps in anticipation, knowing the approximate ID I turned down close to the specified ID of the PolyCarb and stopped it at that. Two of my end caps look like they have an identical OD. However, upon receiving the Polycarb, one slides in with a firm fit and the other doesn't quite make it. It must be a hair thickness…

                I think that I will have to make two end caps for each end. Both will be prototypes. The reason for this is due to the need to oversize the OD of the end cap that fits into the Polycarb. I can make one end cap as a working prototype, turn it down, slip ‘O’ rings on, and press fit it in with all the drive shafts and push rod prototype parts in place and test the operations of these and their watertight-ness.

                That’s great for testing the components and all the goings on at the end of the end cap however, I can’t simply scale up that end cap to meet the requirement of then having an over sized cap to shave down to size for the given fluctuation in Polycarb ID’s I may encounter in the future. Hence the need for a second end cap. Then once all testing is done I can get the same end cap design, slightly over sized and then copy the features of the slightly smaller end cap onto the over sized one and use this as the tooling master.

                I hope this makes sense David…

                This brings me to the main question I need to ask, How much oversize is realistic? I have no problem having to shave each individual endcap as needed, I enjoy turning and I ain’t going to be the Henry J Kaiser of the Model sub world turning out hundreds of these. I’m guessing rules of thumb may come into play here. Could I estimate a third of the thickness of the polycarb? To give an example if that doesn’t make sense, Say the ID of the polycarb is 76mm (which it is, 3mm thick ) the OD is 81.. Should I make the OD dia of the endcap about 77mm or should I make it only just, not fit, so 76- point something?

                Can anyone estimate percentage wise how much deviation there is in Polycarb stated to be of the same spec? I know this is a curly question, I hope it makes sense, It’s one of those small things that’s a major thing.

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                Thanks,

                David H

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                • #9
                  David, i do not know what the variance of the tube you got, but I can share the variance of the ones I buy.
                  https://www.mcmaster.com/polycarbonate-tubing
                  If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                  Comment


                  • #10
                    Find a piece of Lexan tube with an inside diameter larger than all other like-sized cylinders in your racks. That's the standard. Now, make your masters radial flange over-sized from that; about 3/32" oversized. That accounts for tool shrinkage, casting shrinkage, and will still be an interference fit to your biggest diameter cylinder.

                    David.
                    "... well, that takes care of Jorgenson's theory!"

                    Comment


                    • #11
                      Some experimental endcap ideas!

                      So if your ID varies could you make a cast ring to glue in the tube to accept a ID endcap? The cast ring should be a part that comes out repeatable.
                      Yes this will decrease ID at end opening.

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                      If ODs are more precise on tubes could a endcap that fits outside the tube work most times. Or again make a glue able ring to fit the tube.
                      Yes this is a increase in diameter at each end of the WTC.

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                      • #12
                        Just like to point out that only the o-ring seals on the tube so only the o-ring groove needs adjusting for the different tube internal diameters. Size the other diameters of the end cap so you never have an interference fit.

                        Comment


                        • #13
                          Originally posted by type7 View Post
                          Just like to point out that only the o-ring seals on the tube so only the o-ring groove needs adjusting for the different tube internal diameters. Size the other diameters of the end cap so you never have an interference fit.
                          The breadth of diameter tolerance between lots of cylinder precludes making the fix that simple. Often the shaving extends to the radial flange itself AND the o-ring groove. But, hey … what do I know?

                          David
                          You Can Only Lead 'em To Water You Can't Make 'em Drink
                          "... well, that takes care of Jorgenson's theory!"

                          Comment


                          • #14
                            You can go to a “fatter” o-ring. It will give a little more variance, but stick to what David says. He has more wtc out there than probably anyone.
                            If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                            Comment


                            • #15
                              Hello all,


                              Thanks for the feedback. Most response I've ever had. Scott T thanks for the drawings. Got me thinking. Thank you all. I am also pretty confident that the supplier I have can get tube that is pretty consistent,
                              but am thinking of an end cap that just doesn't quite fit. Then shaving down and adjusting the O ring grooves and O rings accordingly.

                              I will continue thinking this one through so keep up the ideas. I will still keep with the idea of making two end caps to prototype each final design.

                              Thank you all,

                              David H

                              Comment

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