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WW2 mini sub build EmptyMon Nov 29, 2021 5:25 pm by timgarrod

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WW2 mini sub build EmptySat Nov 27, 2021 4:50 pm by geofrancis

» What 3D PROGRAM (S) do YOU use/ How You use it/ What can be done with it?
WW2 mini sub build EmptyThu Nov 25, 2021 1:35 pm by ccclarke

» UHF radio control for submarines (openLRS, LoRa, FSK etc. on 458Mhz and 433Mhz )
WW2 mini sub build EmptyMon Nov 22, 2021 2:22 pm by david f

» Deep Dive submersible
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» WW2 mini sub build
WW2 mini sub build EmptyFri Nov 19, 2021 5:26 pm by SimonH

» Radio ideas -27Mhz
WW2 mini sub build EmptyFri Nov 19, 2021 3:26 pm by tsenecal

» Dorji 1278 BDM modules for 458Mhz - Not working
WW2 mini sub build EmptyMon Nov 15, 2021 9:59 am by david f

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WW2 mini sub build EmptySun Nov 07, 2021 8:33 pm by geofrancis


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    WW2 mini sub build


    Posts : 40
    Join date : 2020-09-29
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    WW2 mini sub build Empty WW2 mini sub build

    Post  SimonH Wed Jun 09, 2021 11:06 pm

    After some preliminary design & build I thought I'd share the fun(!)
    I've always been interested in submarines and even though about building a human sized version, but probably best I didn't my boatbuilduing skills are not that good in plywood.....
    However, as covid lock-down struck in 2020 I was was made redundant so decided to see what I could do with the CAD package FreeCAD, and based on photos & other drawings from the internet I generated some reasonable representations of Seehund & X-class as both appeal to me as models. I find the modern subs a bit anonymous, a bit like steam trains vs. diesel, possibly contentious but thats my preference. I then realised I had designed as full size so had to repeat a lot of the work to scale them down to about 1m, based on 110mm drain pipe fro the centre sections.
    WW2 mini sub build X-clas10


    WW2 mini sub build Seehun10

    Neither will be museum standard, I subscribe to the 'measure with a micrometer, mark with chalk, cut with an axe' philosophy, but I aim to give areasonable likeness.

    Starting from scratch, I have no box of bits to raid, so the first task was a workable radio control system, bothered me less than mechanical stuff as I work in electronics. So the autumn to spring '21 was getting the 458MHz system going, with less time available now as I am back at work. I'm not going to add much on that as most is on the UHF radio control forum. For interest I use the EagleCAD package for electronics & PCB design as it is also free up to about 100mm x 100mm or so.

    Current plan is a peristaltic pump & bladder type system having discounted the idea of using a bicycle CO2 system as too risky and dangerous for a 1st model, but I decided I would build the inards up bit by bit and see how long a WTC I needed, based on a 75mm dia tube.
    Since I don't have a 3d printer the end caps are probably going to be cast resin based on a simple wooden master and all fitted into an outer hull made from 110mm drain pipe with fibreglass end sections. I don't want to go to the effort of making a complete mould for the fibreglass so I'm thinking of moulding over foam that I can then cut away rather than trying to disolve in acetone or similar solvent.
    The Seehund appeals as it has the lower tube to the pressure hull that I might use to hold the batteries to keep them central as they may be a major weight.

    After help from the brushless motor forum I have gone for the G2 Hydra15 system and now have the basic motor and gearbox with a 9:1 reduction using timing belts.

    WW2 mini sub build Dsc02715

    I shall probably re-make a lot of it, but the basic setup seems OK.
    I have found that freecad is difficult to cut & bash metal from, so I use SolidEdge a free 2D drawing package to create traditional style drawings of the various peice-parts.
    Fortunately I have had for many years a myford ML10 lathe so boring the brass bolts for the shafts & layshaft ball-races is fairly straight forward.

    Current task is the brackets that hold the servos & routing the control rods past the motor & belt drive pulleys. Again made from aluminium sheet which can bolt onto the fwd end of the moter/gearbox assy.
    In front of that I intend to switch to perspex for the support of the ESC and PWM servo board.
    But that will be another post.

    david f, subkraft, Robbert de Rouw and Seehund Willy like this post


    Posts : 40
    Join date : 2020-09-29
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    WW2 mini sub build Empty ESC & servos added

    Post  SimonH Sun Jun 20, 2021 10:13 pm

    I've now added the servos & control rods and some supports for the ESC & PWM driver board. I use the PWM board to drive the servos & on/off channels rther than generate in the Rx, so the Rx feeds data to the PWM board that generates actual servo controls.
    WW2 mini sub build Dsc02717

    As you can see the only way I managed to get the servos (mini size) in is back to back with one control rod either side,that seemed to be the only spare space in the 'gear box' area.
    Originally I intended to mount the servos on top the frames, but I moved them outwards so they didn't foul the rubber grommet I fitted to the hole used for the motor wires. Having though about it I think I will move them back inwards and simply not mount them direclty to the fwd motor frame, but on top of the end nuts as they currently are. That means I don't loosen the motor/belt drive frames if I need to remove them.
    At the moment one control rod has an O-ring between the brass bolt and cap nut, but I need to make another a test it for water-tightness as I am not convinced it will work as:
    1. the inside of the cap nut is not a good finish, and being stainless steel I'm not sure I can get in there to machine it flat
    2. the thread of the cap nut is also not perfect so I'm not sure the cap nut will screw right down onto the end of the bolt
    3. the only groove for the O-ring would be a simple counter sink on both parts.
    I'm thinking of either trying the bellows option or using a bigger control rod a it passes through the seal, I've tried to leave enough space for a bigger bolt for the seal, so could try either.
    WW2 mini sub build Dsc02718

    I've changed to 'perspex' for the ESC/PWM board mount as I don't need the mechanical strength or rigidity, but I think 1.5mm is a bit lightweight. As the servo mounting plates have moved outwards and the PWM board supports are longer than intended you can see it wouldn't fit in the intended 75mm tube envelope, so I need to re-make the servo plates and revise my 3D model to get it centred a bit more. I was hoping to get the ESC capacitor tucked inbetween the servo plates, but the capacitor is at the opposite end to the motor wires so maybe not.
    WW2 mini sub build Dsc02719

    WW2 mini sub build Dsc02720

    I didn't make the ESC mounting plate longer as I have not fixed as to what comes next. The idea is to have the Rx right at the bow end, with the ballast pump in the middle, so the next task is to get the perristaltic plump & control relays and see how they can be fitted. The relays can be driven by the same PWM board, but I am half expecting to have to design a solid state relay board as the standard relay boards might be too big to fit, but we'll see.

    david f likes this post


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    WW2 mini sub build Empty Re: WW2 mini sub build

    Post  SimonH Sat Jul 17, 2021 10:23 pm

    I've now managed to get all the control functions onto the prototype inards:
    WW2 mini sub build Dsc02721
    From the right are motor & 9:1 belt reduction gear, servos, PWM servo board & ESC behind, dual 5V relay module to control pump, 12V pump, another relay module (intended for an emergency rescue float), 458MHz reciever and finally a 12V master on/off relay. The last item is from '12V planet' and seems to be a standard auto type, but it has an integrated fuse holder, supplied with a 20A car fuse. I may replace  that with a 5A to 10A though.
    Not that vissible are the 0V & 12V busbars, one either side of the pump, basicaly 2 aluminium strips with M3 screws as terminals. At the minute the connections are a bit rough, but M3 crimp terminals seem to be on long leadtimes! In the final version the master relay will be controlled via a reed relay and magnet so I don't need another hole in the WTC. Electrical connections to the WTC will probably be via M3 screw terminals rather than a proper waterproof connector.
    The glass at the back is to check the pump works, and the 12V lead-acid battery is in the forground.
    The total length is about 575mm, so a WTC of about 600mm x 75mm dia which is a bit longer than I hoped. I can save some space as there is a bit of a gap between the antenna and the master relay. I did think about trying to fit the relay down the side of the antenna, but decided against it as I didn't know what effect on reception it might have.
    All electronic systems I have worked on have always had power protection of some kind to limit fault damage, so I was getting a bit twichy about have no fuses, but at least I have one now. I was thinking about designig a PCB to hold a few minitaure car blade fuses as the only option seemed to be the inline fuse holders , but even they are quite big, but I don't think the benifits are worth the effort & space.
    I think for the real thing I will use GRP sheet, as the perpex is easy to work but very floppy and doesn't seem to glue very well, some of the joints have already come apart. possibly with a solvent based glue it might be OK.
    Obviously the bladder is external to the WTC and I think I'll have another sealed resovoir as I'm not keen on pressurising the WTC. This is because I'm intending to swap to 4mm for all shafts and use 4x9x2 seals which might vent if the internal pressure is higher than outside. The Seehund would be just the job with its double tube hull design, but we'll see.  
    I'm also intending to go with a 'wet' lead-acid battery. The one shown is a 12V 2.3Ahr and the current is about 1.8A at max motor speed which seems like a good match.

    Next job is to finalise the shaft seals......

    david f likes this post

    david f
    david f
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    WW2 mini sub build Empty Re: WW2 mini sub build

    Post  david f Tue Jul 20, 2021 9:15 am

    Looking very good.
    Just a few "Keep It Simple" type comments. Fuse definitely a good idea. I use a 15 amp car type. You may be able to eliminate the master relay if you are happy to connect at the battery. (One advantage of having a battery in the wet.)
    You maybe need to think about where the bag is going to go - simplest advice is centered around the periscope.


    SimonH likes this post


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    WW2 mini sub build Empty Re: WW2 mini sub build

    Post  SimonH Sat Sep 18, 2021 9:32 pm

    Having got the basic mechanics working and the shaft & control rods seals sorted I decided to start on the WTC. In the end after reading various threads I opted for 75mm polycrbonate tube and end caps machined from 5mm & 10mm polycrbonate sheet. One reason for using polycarbonate tube is I can see whats going on inside, as its my first foray into sub building.
    Having received 1m x 75mm dia tube I measured the inside dia of one end as 69.38/69.36mm, 69.37mm (average), based on 2 measurements taken at 90deg. I also got 2 sizes of O-rings; 1.5mm x 66mm ID and 2.0mm x 65mm ID both Nitrile and with an outside dia of 69mm.
    The plan was to make an inner endcap from 10mm disk with a single O-ring groove bonded to a bigger outer endcap with tie-rods outside the WTC as that means less holes. Based on published data that meant O-ring grooves (for the 1.5mm x 66mm O-ring) of 2.1-2.2mm wide, 1.26-1.32mm deep(total) but with a clearance of 0.1mm. However, when I came to machine the groove I realised that my vernier can't measure the diameter of such narrow grooves, though it could measure the depth. As a result I had to calculate the total depth allowing for the claculated clearance (tube ID - inner endcap OD). I was starting with the 1.5mm O-ring on the basis that if it failed I could enlarge for the 2mm O-ring!

    I did think about dual O-rings, but most of the literature seemed to imply that a using 2 O-rings should have a vent (or cut O-ring) in between to prevent pressure build up so I decided just to use a single.

    Obviously machining a disk 10mm x 69mm dia in a standard 3-jaw chuck was not viable so I used a 6mm bolt as a mandril. That was obviously was going to leave a 6mm central hole, but that would be sealed by the 5mm thick outer end cap and by design the holes for the shaft & control rod seals would miss that central hole so not a problem as long as the 2 parts were fully bonded.
    I also had to hand file a bevel on the inside of the WTC to provide a lead-in for the O-ring on assembly.

    Having machined the outer endcap I decided to test it by pushing into the tube, holding vertical on the ground to prevent the endcap poping out and filling with water. Not a success as a steady stream of water leaked out. Investigating further I realised that the groove finish was rough and the O-ring was quite loose, and re-measuring everything I calculated that the total groove height was 1.31 to 1.33mm, a bit on the loose side with a clearance of 0.13mm. Also I had used a 1.5mm parting tool to cut the groove, using several cuts, at a speed of some 840rpm and the tool tip was a bit under parr shall we say. so onto plan B a 2mm O-ring.

    This time I reduced the speed to 128rpm and re-ground the tool and tried for a groove 2.6-2.7mm wide x 1.72-1.79mm deep (total). In the end I have a groove 2.46mm wide x 1.46mm deep which judging by the effort to fit into the tube is still a bit undersized. The finish is much better, though not vissible in the photos. Using water as lubricaton I managed to fit it into the tube (increasng the bevel as well) and this time the water stayed put, so passing a pressure test to 1m water. I had intended to seal the mandril bolt with a 6mm dowty washer but I didn't bother and it seemed to seal, possibly because of the protective plastic film still on the polcarbonate sheet.

    WW2 mini sub build Dsc02813

    The patterning on the tube by the way is not crazing but the protective clingfilm it was shiped with.

    The outer endcap I shaped by hand, but using 400 & 1500 'wet&dry' gave a good surface to the edges, and also on the machined inner part:

    WW2 mini sub build Dsc02814

    The outer endcap still has the protective film on it.

    To bond together I used EMA pastic-weld with a weight used to hold the parts together, using a small paintbrush to transfer glue to the joint edges, i.e. following instructions!.
    WW2 mini sub build Dsc02815

    I'm not entierly happy with the joint as I can't see where the glue has spread to, the bond & sealing round the edges is crucial. I think the next one I will not use such a heavy weight, so hopefully more glue will get sucked into the joint.

    Having managed to pressure test I'm happy that the design is OK, so off to make 2 more. Actualy only one, since I don't want to make the 2nd unitl I have cut the tube to length. As has been commented on before the internal diameter is not precise, the other end gave diameters of 68.90 & 69.30mm, so not quite so circular which is more of a problem. I think I'll stick with 2mm x 65mm O-rings as they seem to work. I did notice that without some lubrication the O-ring can get forced into the clearance gap, but hopefull increasing the depth will sort that out. I could try redfucing the clearance, but if the tube is not circular then I might not be able to.

    I'm also going to use the 5mm sheet as internal supports for the electronics so I might make a number of blanks at the same time.
    The round blanks are machined from square blanks but for the next batch I will use a lower speed. The problem is that machining polycarbonate rasies horrible burrs, reading around its probably due to heat melting the material, so reducing the speed should help. Many recomendations refer to lubrication, but my lathe hasn't got that and I don't fancy using water based lubrication anyway.

    I will also machine the 6mm bolt mandril so the head is round but concentric with the thread. The one I used was a standard bolt, but the thread was not quite concentric with the head, so taking it out for any reason meant it didn't always go back exactly the same.

    The biggest issue I feel is not being able to directly measure the groove diameter, even my calipers won't fit in the groove width.

    david f likes this post

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    WW2 mini sub build Empty Re: WW2 mini sub build

    Post  Tom(ADMIN) Mon Sep 20, 2021 4:17 pm

    I used to use 1/16" (in USA) or about 1.6mm for my endocarps, but I do not do that now. I use 1/8" or about 3.2mm o-rings. Why? There is such a variance in the Lexan tubes that a 1/16 mostly works but if the tube has a large deviance, the contact became iffy. With the larger o-ring, I have zero issues with inner diameter changes. My pistons will be changing too. While not wanting large amounts of friction, I may move to 3/32" about 2.3mm for the piston to give me that extra sealing.

    Love what you are doing and will definitely steal some of the photos and re-post on FB. Keep up the great work!

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    WW2 mini sub build Empty Re: WW2 mini sub build

    Post  SimonH Fri Nov 19, 2021 5:26 pm

    After a bit of a break for the summer hols its back to subs!
    I've re-made the gearbox/motor assmebly this time using new 1.5mm ali plate and using 4mm ID ali tube as spacers as fidling about with nuts was a pain to assemble. I also made the blanks for the new end caps but decided to follw Tom's lead and go to 3mm O-rings to allow for more eccentricity, and the blanks for the bulkheads for the electronics tray.
    The original idea was that the gearbox assy is fixed to the end cap via the bushes/seals of the prop shaft and the two control rods with clearance holes in the inner part of the end cap, however after making the gearbox I realised that due to the larger O-ring seal plus positiional miscalulations these clearance holes would have broken into the O-ring groove, not good. As a result I have mad a new spacer from the same 5mm polycarbonate that fits between the end cap and the gearbox assy, but now the roughed out seals (25mm bolts x M6 & M10) are a tad too short as you can see.
    The photos show the new gearbox fitted to the prototype end cap still with the 2mm O-ring.
    WW2 mini sub build 20211110

    WW2 mini sub build 20211111

    WW2 mini sub build 20211112

    You can see there is not much thread on the seals, and then I need a bit more for the dowty/bonded washers to provide the outer seal.
    Obviously the seals are not complete, the control rods will use a thin brass tube and siliconne tube and the prop shaft a commercial cup seal recessed into the bolt head.
    I couldn't work out how to (easily) fit ball races & seal to the propshaft, but as its quite slow due to the 9:1 reduction I'll stick with a plain brass bearing!

    I did have to reduce the length of the layshaft bearing and use a half-nut so it was within the 5mm allowed by the spacer, but thats OK, and still has the ball races in the bolt heads.
    Overall I'm quite pleased with the result, its a lot cleaner than the prototype.

    Next job is re-making the brackets for the servos that bolt to the free end of the gearbox assy, whilst I wait for some new 30mm M6 & M10 bolts for the seals.

    david f likes this post

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