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    CNC boat kits...?
    ".......I am on a bitof a learning curve at the moment........" A few lessons I learned: 1 - Get a good, solid base-board which isn't warped. The local timber yard may have off-cuts of 3/4" ply. You will want to assemble the mechanics on a proper base, and it helps to have it available first. You will want to paint it anyway, so it will need time to dry. 2 - Get a dial indicator. An easy way to check for precision in assembly is to attach a dial indicator to the end of the Z axis and run it over the base board. It's good for other fault-finding and calibration as well. There are cheap ones on Ebay. 3 - Plan out all the wiring. I put my limit switches in as an afterthought, and found that I had wires which couldn't go in the places I wanted them to go. 4 - Wiring loom control. Consider Drag Chains, Heat-shrink tubing and Braiding. All items are very cheap from Ebay. If you don't put the wiring in at assembly you won't be able to put it in later once everything is connected up... 5 - If you use a drag chain for the USB connection, you will either have to make sure that it's wide enough to take a USB plug passing through it, or cut the plug off, pass it through and re-solder it afterwards. If you do the latter, note that the shielding in a USB cable is aluminium, and won't solder. So you will need to use a connector plug which has a physical connection to the shielding, because interference can ba a problem on these
    machines
    ....
    1 month ago by DodgyGeezer
    Forum
    CNC boat kits...?
    While it helps to be accurate, the final trimming of the work holder is done by the machine itself. Here I am cutting the edges of the holder so that a sheet of 4" balsa will be neatly held. That's about 1.6mm wider than a 100mm sheet, so I will need a packing strip if I use the metric sizes. It's surprising how precise these
    machines
    are - I'm moving the cutter in by 0.1mm each pass, but it can move in much smaller steps - one microstep is 6.25 microns, which is about 2.5 ten thousandths of an inch. The balsa will be held between some raised sides made of hard balsa, so that they can be cut easily by the machine if I get a command wrong and move the cutter out of the work area. I expect to put a 2mm felt layer below so that the cutter will have something soft if it goes completely through the workpiece.
    2 months ago by DodgyGeezer
    Blog
    Gina 2 Billing Boats Fish Cutter - Restoration & Conversion
    As promised (or threatened?😁) stage two of the hull work and thoughts on motorisation. The hull was sprayed with two coats of grey primer/filler. Pic1. As usual this showed up the remaining imperfections (pics 2 & 3), but I'm not going to worry about them until I've got prop shaft tube and rudder stock sorted out and permanently fitted πŸ˜‰ After my attempts to make and thread a 3mm prop shaft went awry Martin (Westway the Mechanicals MasterπŸ‘) stepped in and made me a decent one complete with a bushed stuffing tube πŸ‘ Vielen Dank Meister😊 I did however manage to make a 4mm to 3mm reducer so that I could fit a Rabeosch 35mm prop as seen in pics 2 & 3. The tube and shaft from Martin, arrived Saturday an' he only made it on Monday😊, have been dry fitted so that I can start setting up the gears, necessary to bring the drive down to the prop shaft fitted very low down in the hull, and motor mount. Pic 4. Motorisation: (Remember folks - this kit was designed and built as a static model!) I want to use the old 1950s Taycol Target motor which my Dad originally fitted in the Sea Scout which I have renovated and upgraded to work forward and reverse with a standard ESC. See Build blog 'Sea Scout - Jessica' Many of you will know that the Taycol motors were field coil motors, meaning that they have no permanent magnet around the rotor coil, and thus reversing the battery connections to the brushes had no effect on the direction of rotation, as this simply reversed the magnetic fields of both stator and rotor coilsπŸ€” To counteract this so that the motor could be used in both forward and reverse with a conventional brushed ESC I modified the motor slightly (separated the two coils) and built a simple converter board to connect it to the ESC. Again see the Sea Scout blog for the details of the conversion. Basically; once the field coil and brush-gear (rotor coil) have been separated a simple diode bridge can be used to apply the output of the ESC to the motor. This enables the reversal of EITHER field OR rotor coil polarity, depending on how you connect the converter to the motor. Thus reversing the direction of rotation of the motor. Beneficial side effect is that the diodes also suppress the commutator sparking😊 In my case, with the Taycol Target, I also cleaned, flattened and polished the commutator. Thus significantly reducing the potential for spark generation in the first place! A peculiarity of the Taycol motors is that they all use metal brushes, pressed phosphor bronze strip, so they need oiling! DO NOT oil conventional brushed motors with carbon brushes unless the brushes are exchangeable or you want to have to buy a new motor!!!!! Pics 5 & 6 show the proposed position of the Taycol in Gina 2 and pic 7 the prototype converter board I knocked up to test the motor, together with a Graupner Navy V30R Marine Brushed ESC. Details and results in the Sea Scout blog, including video of the sparks and oscilloscope pics of the drive waveforms before and after conversion! The latter showing the spark suppression effect of the converter😊 Some samples attached - last 3 pics. Pic 8 pic shows a more compact version of the converter, one of a few types I'm doing for Martin's various Taycols as a trade for the prop shaft he made for me and some useful material he sent. Thanks mateπŸ‘ Next steps will be 1) mounting the gears correctly on the shafts, requiring the manufacture of a 3/32" to 4mm adaptor and a 1/8" to 4mm adaptor, and keying them to the shafts - Hooray for mini milling
    machines
    πŸ˜‰ 2) manufacturing bushed end plates to hold the gears in place, 3) fitting the motor mounting platform. I'll probably borrow from my experiences of real shipbuilding and do this as a suspended 'false floor', i.e. mounted on stiff springs to enable adjustments to optimise the gearing mesh! On real naval ships this is done to improve shock resistance and to minimise engine noise / vibration conduction to the hull, thus significantly reducing the acoustic signature of the ship. Not that I'm tooo worried about being torpedoed 😁 Worth a tryπŸ˜‰ Pic 9 shows the cleaned up and renovated Taycol Target motor. Pic 10 shows the drive waveform complete with sparks before modification.πŸ€” Pic 11 the cleaned 'forward' waveform with the converter board. Pic 12 the cleaned 'reverse' waveform, no suppression capacitors needed πŸ˜‰ More soon folks, Cheers, Doug 😎 PS Along the way a new keel was fitted as can be seen in pics 1 to 3. The original builder had 'buried' the keel in the hull planking! 😲
    10 months ago by RNinMunich


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