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

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  • #61
    Hello all,

    Been a busy time,

    So, after machining the Stern end cap up and getting to be a tight fit with "O" rings all I needed to do was to assemble the unit. This is pretty simple as the parts are at hand. All the cast pieces done, just some screws in and some silicon in place. Take the two motors and their respective 2.6mm bolts. push through with shaft extension and then bolt into place.
    After this, I assemble the shaft support housings, These comprise of 5 parts mostly held together with Silicon and may be a drop of superglue. So I take an Oilite bush. I don't know Why I haven't used these before, they are fantastic. I then push this inside the cast inner seal support. Get some grey silicon onto the outside of the Seal support and press it up inside the outer ring. Press these parts up until they are just below the surface of the rim. This will make room for the u-cup seal.

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    I also needed to drill out the two holes on the sides of the flange where the Sheet metal plate will be affixed. At the same time I have also made up the push rod seals. The bent over push rods just make it easier to push in and out. These seals are glued in with Silicon.

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    An assembled motor shaft support. The base of the support meets the surface of the end cap with a rim of Silicon. The U-cup seal has been seated and then I paste a generous lathering of Silicon, making sure that it covers the outer rim of the U cup seal. Then I press down the 'shaft support housing' which is probably not the best name for it as it sounds like it does more work than it actually does. This cap simply keeps the silicon in and makes it look neat.

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    Hey presto, back end done. Dunk it in the water and find no leaks... happy..

    Now I have to repeat this process all over again with the front End cap. YAY...

    I started the process of molding the front end cap around the same time as the Stern end cap. But for the sake of clarity thought that I would show the development one after the other. I steill had to resolve how to mark out the pump mounting bracket that would attache to the front of the end cap. This pump bracket will be optional, but I one the less wanted to work out how to mark it onto the end cap in such away that would not be too obtrusive to the design is not needed but would also show exactly where to glue it if needed. I would either do this in the workshop or leave it in the kit for the customer if they want to do it.

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    Initially I had a go at scribing the outline on the front of the end cap, but whilst doing so the words of HWSNBN haunted me about such endeavours.... I then decided on a raised styrene section slightly smaller in area that the molded bracket so that the bracket would fit over the area. Subtle but effective. That's what I wanted... a bit like HWSNBN really... At the front can be seen the renshape profile of the bracket. The back has been hollowed out to make way for a 4mm stainless bolt that will be embedded pointing forward to take the clamp at the front.

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    Here you can see the final finish and shape of the styrene profile for the bracket to mount onto. Just like the previous end cap, Play- Doh is awesome for separating the mold halves with holes and the like. I then press a light layer of Play Doh all over the outer face before face planting it to the base of the plywood molding board. The large holes are for the Electrical conduits and the smaller ones the Pump silicon lines for in and out.

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    Press a little bit of Play-Doh into the hols in the outer tray supports, or you could pour the silicon and find that the master wont come out as its held by siliocn passing through the holes or maybe the silicon
    wont make it that far because of the trapped bit of air in the middle...

    Ok, Enough for now, back to writing up the instruction manual. This thing is going to be a door stopper......

    Comments, thoughts..

    David H


    • #62
      Very good work, David. It's all coming together, my friend.

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


      • #63
        Thanks David, any chance I could get that write up on the shaft extension technique?

        Yes, I'm pretty happy with how it's going. The procedure and method that I'm going through is giving the results and the finish and the quality of the end caps is something I am amazed with.

        As you can see I have used Play-Doh to fill in the holes as I go about the mould making process for the front (Bow) end cap. This end cap will have the option of having some extra parts that will hold onto a pump if the builder so wishes. Once the end cap is down in the plywood base, I placed masking tape around the edges, if i didn't then the Play-doh would get into the register holes and I would have to spend time picking out the chunks from the holes. I then press the Play-Doh into the grooves around the sides of the mould to seal in and get a good part.

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        The dis-colouration of the surface on the model is deceptive. Its incredibly smooth after layers and layers of primer and spray putty and then up to 1000 grade grit. I press the Play-Doh down so that
        it is only to about half way up any given hole. These round pieces are so much easier to mold as I have a bad habit of liking to make boxy square molds for all my other regular pieces. I know I could do this way for all those other parts, call me stuck in my ways.. Time for a piece of PVC!...

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        Once again I have made sure that there is an irregular square raised bit otherwise you could spend a while rotating to get the right fit.

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        Glue down the base of the PVC with some silicon, wait for it to dry. I've started doing this more and more. Rice is a great way of working out the quantities. Just be willing to spend time picking out the odd pesky bit that sticks. This is a good accurate and simeple way of not wasting the silicon. It's spency stuff.

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        Pour in the resin, let the bubbles pop or have fun popping them.

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        Give it a couple of hours and then pull the master off the base by simply pulling the PVC pipe off the base. Then push the big chunk of silicon out of the PVC pipe.
        It may not be too clear here but the register points for the holes in the side of the supports are just visible in the molds. The trapped air inside the holes meant that the silicon did not join each side causing a potential diplomatic incident with me where the master piece would not come out due to the Silicon 'tunnel'.

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        Trim off any flashing and then do the whole process all over again.. Minus the Play-Doh.

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        I like to rub lanolin over the silicon mold. I also wipe a thin layer over the master front face. PVC pipe time.

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        I will be using less Silicon because there aren't really the flanges of the other side. Rice and a simply determination of the amount of Silicon, then pour. I like watching Silicon pour. It is almost as
        mesmerizing as watching a log fire. (well, for me anyway).

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        It is amazing how the light of the late afternoon can make something that is grey, look Blue. The two parts have turned out great. Really happy with them.
        I was concerned that air bubbles might stuff up the polyurethane resin getting into the far corners of the bracket. So I poured a small amount of resin into these spaces
        and then planned to close up the mold and pour the rest. I then needed to cut the reserviour /channel, this is the red series of lines at the top to match the same spot on the
        other mold half.

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        Button up the two halves and pour the rest of the Resin. These end caps take a fair amount of Resin. When I see the amount of end caps David punches out where there are twenty to thirty on a table, I'm thinking about how much resin that is....

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        Finally I have the front and the end Caps. Happy with the result. Machining and fitting next...

        David H


        • #64
          What a process and skill level it takes to manufacture these type pf parts! This is a skill that I hope never gets lost through time! You and David M. sure do fine work! Thanks for sharing!


          "Firemen can stand the heat"


          • #65
            Hello Rob,

            Thanks for the compliments. Just doing my bit to keeps the skills alive. I really do enjoy the design and development journey that a project like this puts you on. It has certainly pushed my skills and abilities. There is still a lot more to do but I hope that I can produce a reliable and effective cylinder for the market. You are right, Dave’s stuff is incredible. It is beautiful watching the engineering that goes into his work.

            David h.


            • #66
              Hello all,

              The end caps come out of the mold with little variation from the masters. Obviously there may be a few air bubbles, but most of these are encountered when I start shaving off the excess and they are tiny. I have found that when machining the end caps, there is very little needing to be shaved off. I spend most of the time just getting the cap to sit centered on the fixture. I haven't got it perfect but I've got it very close.

              The fixture that I use for the front cap is the same as the rear. The Screws are just located in a different position. I also have to use collars on the screws to make sure that the butterfly nuts are raised above the rim as they are too close to the radial flange and won't go any further.

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              Once the cap is centered I can move the cutting tool in an smooth down the radial flange.

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              I find that even though the O ring grooves are molded in, I generally will have to take the flange down beyond the depth of the grooves and I will have to re-cut them. Soon enough I get to the point where I have to take the lexan tube, place it over and take off only the tiniest amount.

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              The fit of the tube over the cap is free, its not tight. That will be the job of the O rings as they compress and provide the seal. RC submarines would be very different without O-rings. Take the parting tool that I usually use to part off pieces and cut the grooves. Give a little sideways movement to widen the groove and give it some sideways space as it gets compressed.

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              Then a groove cut for the second O ring and a slide of the tube over. Then onto machining the second groove.

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              I then took the cutting tool to the very edge of the fixture and shaved a little off the end rim of the end cap.

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              You can clearly see the rectangular raised section that outlines the position of the bracket for the Pump. Also clear are the two holes for the electrical connectors and the nitro tube in and out points for the pump Ballast system

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              David H


              • #67
                Very Quiet,

                So now I have completed both end caps, assembled the direct drive shafts for the twin motors and the push rod seals. Now I just have to create the molds for the pump bracket that will be mounted on the front end cap. This bracket as shown previously is made up of two brackets. A large one mounted directly over the rectangular profile on the front of the end cap and a smaller one that bolts down over the front of it to hold the 12v pump securely.

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                The pump secured in the masters for the bracket. This pump is a standard sealed 12 v pump that is used in windscreen washers. The outlet pipe you can see over to the far left. I needed to bend this up wards so It would not stick out too far off the side and get in the way of the hull. So take a brass rod, push it up into the nozzle, heat up the end of the plastic nozzle with a heat gun and gently bend. I have hollowed out the section in the rear of the bracket in order to save urethane material, but also to produce a deep recess for the 4mm bolt to be set into the molds.

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                So after the usual processing to get the parts, just smicko, I then prepared the mold board for the two bracket parts. Once again the layout would mean that the parts would be angled so that the highest point of the part would be just where the channel would be.

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                Here you can see the first part of the mold has been done. I have had to place brass rods into the space for the bolt to pass through. I have also had to mount the stainless bolts in the main bracket. Once again the yellow Play-doh creates the funnel for the pouring reservoir for the urethane. The mold is given a rub of lanolin and then placed back in the mold box, ready to pour.

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                Pour and have fun popping the bubbles. Leave it overnight. Once done, pull the molds out and clean up. I usually run scissors around the edges and trim off the excess silicon. I pull out the play-doh and run a knife down the grooves to re-establish the air vents needed. Then I can spray the mold with release and press up. Strap the mold halves together and place plywood hardbacks and rubber bands on. Pour Urethane and pressure cast. Done.

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                The inner surface of the main bracket is a bit ugly but you ain't going to see it once glued to the front of the end cap. The bolts are embedded into the front of the bracket.

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                Here you can see the brass inserts that will have the silicon tube from the pump, going in and out. Bracket glued to the front of the end cap over the rectangular profile. A light bit of sanding around the curved recess where the pump is mounted up against.

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                I used a small amount of thin plastic tape around the pump where it clamps to the bracket. This tape is compressible and helps tighten the grip around the pump. Tighten the nuts and its done.

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                Pretty happy with how the whole thing looks. I Like the colour of the end caps. I know that the sun fades the end caps, then they turn a faded darker shade, almost a light brown, keep it out of the Aussie sun, UV's a killer here.. literally.

                David h

                Attached Files


                • #68

                  Maybe this was embedded earlier in the thread, but what is your ballast system going to look like? That looks like it might be a centrifugal pump?


                  • #69
                    Hi Bob,

                    that’s correct, it is a centrifugal pump. It is basically the ‘sheerline system’ as it has sometimes been referred to. The pump pushes water into a loop immediately inside the cylinder. There is a servo acting as a pinch. I am sure that you are familiar with the system. Having the pump on the outside seems to be an Australian thing. I have never seen it anywhere else but here and may have originated in Queensland. Correct me if I’m wrong. I first saw it at the Canberra subregatta a long time ago. I was influenced by a friend from Queensland, an older gent called Jim Russell. He has been selling a version of the 688 class that uses an external pump on the cylinder for years.

                    Anyway, the tube comes back out the front of the end cap and then goes to a PVC sealed Ballast tank in front. As much as it has its drawback I really like the pressurized system.
                    When I was first developing cylinders 15 years ago I used the same system with a internal pump (inlet hole in the front of the forward cap) then a middle tank. If you needed to replace the pump it was a pain. Externally fitted makes replacing it really easy. This design reduces the amount of potential flood points and gives users a simple ballast system that they can set up themselves and feel confident to fix if there are any problems.

                    No system is perfect.



                    • #70
                      Great work Gave. Really impressive.


                      • #71
                        Fat fingers Scott here. I'll try that again. Great work DAVE!!! Not many people can make something out of nothing.


                        • #72
                          Much appreciated Scott,

                          How is the South Coast treating you? Putting you ridiculously big piece of Renshape to good use....
                          Am going to start the single shaft design soon,however I am waiting on parts that are taking forever.



                          • #73
                            Hello all,

                            Now that the front and stern end caps are done, I need to add the smaller bits. Starting with the connections for the pump I connected up the wires to the top of the pump and pushed them through the watertight connections. I soldered the two wires to the top of the pump and then covered both connections with watertight electrical goo. I repeated the process for the main electrical connection that is on the other side and is pressed into its hole.

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                            These wires curve down to the bottom of the end cap and go through the electrical connection. Once the wires are pushed through the connection I then super glued them and ran some silicon around the outside of the connector then pushed it through the hole in the lower front of the endcap and pressed it in.

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                            I have used heatshrink to help seal the connections and to help keep the wires together. Here the other main power connection has been installed in the same way.

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                            The pump’s terminals originally come pointing upwards with a plastic housing around it. I cut that off and press down the terminals. Solder the connections and use the electrical insulation.( liquid electrical tape). After this I cut and insert the two brass tubes that make the inlet and outlet pipes for the silicon tube for the ballast system. These simply get super glued in place.

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                            Now it is just a matter of silicon tunes. Here a tube connects the output of the pump to the inlet nozzle above, then the loop around to the other side and then out the other side. The long tube going to the PVC ballast tank that will be in front of the cylinder.

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                            David H.

                            Attached Files