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Tool time.

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  • #76
    Hello David and all.

    David I have a couple of questions for you regarding my tooling for the upcoming project 667. I am on the cusp of producing some silicon moulds for the 667. The rear appendages and some of the reactor coolant scoops. However I will soon also be creating the moulds for the stern horizontal planes. As you know the 667's stern planes featured fences, (plates at either end of the movable surface.) I am concerned about how to best arrange them on my moulding board arrangement and designing the mould to eliminate the possibility of trapped air bubbles in the outer edges of these really thin sections. I have never moulded parts with such thin plate sections before and I am concerned that because of their thin-ness they may be susceptible to bubbles if the air venting is not well designed and I think this could be greatly helped by their orientation.

    This first picture shows my typical mould board set up with the movable surface with the leading edge upwards. The sprue (dark shaded in section) attaching to the leading edge where the foil is thickest. The thinking being that the plates are pointed upwards therefore allowing one vent placed at the top tip of the plate to allow air to move out as the resin fills up. The downside is that the resin will be pouring into the mould immediately over the brass rod insert, thus hampering a clear open space to pour into. What do you think of this?

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    Second photo shows the movable surface in the more conventional position that I would usually have it with the plates in a horizontal position, My concern being that the air will not be able to escape out the sides of the mould as my vent lines only really run up the split surface. Should I be concerned about extra venting lines or is it really in your experience, not an issue? This is how I would prefer to mount the piece as it allows the brass insert to be away from the pouring sprue. It also means I can have the air vents on a easily sandable flat surface rather than on the curved thick end of the foil.


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    Or is this all not really an issue?


    Second point.


    This has to do with you Fin build on the November class that Scott is developing. I really wanted to see what happened with the rest of the Sail/ Fin fabrication. The reason why I am so interested in this is that I am considering a one piece mould for the 667's fin. However I am thinking of creating a moulded part but out of Glass rather than moulding it out of Polyurethane.. You got up to splitting the mould in two with a knife and then were about to lay up cloth and then that's where I was left hanging....


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    I am thinking of producing my 667 fin mould as a one piece exactly like above however instead of cutting it in two, just brushing in gel coat and then layers of cloth. I am going to have to make a added section on the rear of the sail to create void where the missile deck would be and to make sure that the piece could be pulled out. I hope this makes sense. Do you see any problems with this?



    Regards,

    David H

    Comment


    • #77
      I would cut down int the number of vents you are using. I try to position the parts as such that I only need one vent. For the hinge for example if you angle the part you will not need a vent at the hinge.

      Below the mould I made for the new diveplanes I did for the AKULA, only one vent/part.

      Grtz,
      Bart

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      Practical wisdom is only to be learned in the school of experience.
      "Samuel Smiles"
      http://scale-submarine.com/index.html

      Comment


      • #78
        Hello David,


        Iím gone back to looking at vac pumps and am confused by the stats needed. I realize 29 inches of mercury and also -1 bar with about 8 CFM. However when I look up pumps, they all say how many cfm but none tell the amount of vacuum pulled in any meaning ful reference I can get my head around.They certainly donít mention 29 inches or -1 Bar , they may mention microns. Iíve looked up conversion scales but Iím just getting more confused. Any further advice?

        regards

        David H

        Comment


        • #79
          Originally posted by Davidh View Post
          Hello David,


          Iím gone back to looking at vac pumps and am confused by the stats needed. I realize 29 inches of mercury and also -1 bar with about 8 CFM. However when I look up pumps, they all say how many cfm but none tell the amount of vacuum pulled in any meaning ful reference I can get my head around.They certainly donít mention 29 inches or -1 Bar , they may mention microns. Iíve looked up conversion scales but Iím just getting more confused. Any further advice?

          regards

          David H
          I've seen the same things on 'new' pumps I've been pricing (the one I've got and is still working is nearly 40 years old and I bought it new); nothing I've looked at denotes degree of vacuum expressed in inches of Mercury. WTF!? I blame you metric-tramps across the waters for this horrible situation. A pox on your houses!

          OK, that out of my system Ö...Ö.

          Kevin Rimrodt is a calibration technician. If there's a conversion scale that converts microns per whatever-to-inches, he's the guy. I'll get back to you, Dave.

          David
          Resident Luddite

          Comment


          • #80
            Thankyou David.

            Comment


            • #81
              Hello David,

              its been a while while since I asked you some questions, but right now I am stumped. I am still having a problem with shaft extensions, they are the single biggest drama I’m having at the moment with my cylinder design. I know that you posted a heap of pics a couple of months ago about how to turn then and press fit them with a hammer onto the motor shafts.( I cannot for the life of me find those pics or which thread it is in.)

              Anyway, I am finding them near impossible to get them absolutely centered so there is no vibration. I drill a hole in the stainless steel shaft and then lightly grind the motor shaft and then tap them with a hammer, but unless I concoct some kind of extremely tight accurate jig to hold everything absolutely in line I cannot see how I’m going to get the shafts absolutely centric...

              it it makes me want to drop the ZB-2 design and just go with geared end caps...

              i could take pliers and try bend it slightly that either makes it slightly better or a lot worse. I am worried if I do that then I could slightly bend the shaft inside the motor.

              Help..

              Thanks

              David H

              Comment


              • #82
                Originally posted by Davidh View Post
                Hello David,

                its been a while while since I asked you some questions, but right now I am stumped. I am still having a problem with shaft extensions, they are the single biggest drama I’m having at the moment with my cylinder design. I know that you posted a heap of pics a couple of months ago about how to turn then and press fit them with a hammer onto the motor shafts.( I cannot for the life of me find those pics or which thread it is in.)

                Anyway, I am finding them near impossible to get them absolutely centered so there is no vibration. I drill a hole in the stainless steel shaft and then lightly grind the motor shaft and then tap them with a hammer, but unless I concoct some kind of extremely tight accurate jig to hold everything absolutely in line I cannot see how I’m going to get the shafts absolutely centric...

                it it makes me want to drop the ZB-2 design and just go with geared end caps...

                i could take pliers and try bend it slightly that either makes it slightly better or a lot worse. I am worried if I do that then I could slightly bend the shaft inside the motor.

                Help..

                Thanks

                David H
                There are three tricks to getting the motor shaft extension to line up with the motor shaft.

                First is to insure your lathe is set up so the head stock and chuck are centered (run-in) so that the work does not spin 'wobbly'. You bore out one end of the stainless steel shaft extension with a bit that will produce an interference fit to the motor shaft -- that bit held in a chuck supported on the carefully dialed in tail-stock. You shave the motor shaft as the motor rotates at high speed to a slight tapper. Use a hammer or hand-press to set the extension to the motor shaft.

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                The second is to use a dial-indicator to find any offset of the motor-shaft extension unit -- correcting it by slightly bending the motor shaft itself.

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                If need be I'll impart onto you the secret, discusting, out-of-left-field third method of insuring shaft extension unity with the motor shaft -- too horrible to relate at this time.

                David

                Attached Files
                Resident Luddite

                Comment


                • #83
                  Thankyou David,

                  Im pretty much doing most of that. I should probably use the dial gauge a bit more. Definitely doing step one. Step two grinding Down the outer shaft with motor spinning and fixed grinding. Wheel, am doing this but using a way to big grinding wheel. Will use small disc and third ,standing by for unspeakable business.

                  thankyou David for your schpeedy -ness..

                  dave h

                  Comment


                  • #84
                    How bout using brass tubing instead? 3mm OD; 2mm ID
                    Last edited by redboat219; 09-27-2020, 03:18 AM.
                    Make it simple, make strong, make it work!

                    Comment


                    • #85
                      Motor shaft is 2.3mm

                      Comment


                      • #86
                        Originally posted by JHapprich View Post
                        Motor shaft is 2.3mm
                        Do believe there are 2.3mm i.d. tubing available.
                        If not, just take off 0.15mm all around the shaft.
                        If you're in a hurry get a torch to the brass to soften it and just force fit the shaft.
                        Last edited by redboat219; 09-27-2020, 04:41 AM.
                        Make it simple, make strong, make it work!

                        Comment


                        • #87
                          when it comes to static (Oilite) and dynamic (roller) bearings you want hard against hard or hard against soft. Soft against soft quickly wears away the surface of the bearing AND shaft. Bad ju-ju!

                          David
                          Resident Luddite

                          Comment


                          • #88
                            Beats drilling and grinding
                            https://www.anmlawj.xyz/index.php?ma...ucts_id=494647
                            Make it simple, make strong, make it work!

                            Comment


                            • #89
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                              Make it simple, make strong, make it work!

                              Comment


                              • #90
                                Click image for larger version

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ID:	144007 Thanks David and everyone,

                                I have another series of questions that I hope you don’t mind answering, even though some aspects we’ve been over. I suppose I just need a little further clarity.

                                Leaks in drive shafts.

                                David, do you guarantee that your shafts don’t leak? Or is this a hot potato? I can vouch I have one of your older SD’s and it don’t leak. But are you that confident in the product?

                                My latest design hasn’t leaked until today, So I was really disappointed and I am assembling the first ZB2 for a customer and am currently checking the shaft seals and Uh oh, a leak.

                                Now you know my seal design is similar to yours, I use an Oil lite Bush with an outer housing and a U cup seal lightly glued to the top of the outer housing and the shaft is pushed through. My biggest unknown is how much grip should the lip of the cup seal push around the shaft. Obviously when you push the shaft through the lip it should flex outwards and wrap around as you push the shaft up. I am still trying to work out the fine balance between how tight this should be.

                                I am guessing that if it’s tighter then the motors just pull more amps? But also if you run the motor for longer periods out of water then the lip rubbing against the shaft will cause wear?. Do you not run the shaft out of the water for any length of time?

                                I am am convinced that there is something really subtle and tiny that I have missed, maybe it’s just getting the tightness of the lip on the shaft just right? Maybe my lip seal isn’t tight enough?

                                I have some pics here of my set up if it helps, I have looked at all your photos of the shaft arrangement that many times. I hope my line of enquiry make sense.

                                Thanks for your time,

                                david H.

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