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The last gadget to be added to complete the Crash Tender refit is the searchlight.
The body is made from a short piece of 15mm copper water pipe. A domed piece of copper soldered to one end closes off the body. The tube is just the right size to take a 1W LED and lens. The front cap was made from a ring of copper cut from a Yorkshire fitting which slides over the body of the light. Two small nuts (8BA) soldered 180 degrees apart on the circumference of the body provide mounting and pivot points. The body is mounted to a U shaped brass bracket which in turn is soldered to a brass tube.
In addition to being able to rotate the searchlight, I wanted the challenge of making it elevate. A mechanism mounted under the wheelhouse roof provides both the rotation and elevation mechanics. A small servo provides the rotation function. Two plastic
, salvaged from a defunct inkjet printer, couple the servo to the brass searchlight mounting tube. The gear ratio gives the searchlight a rotation of 270 degrees.
To provide the elevation function, a pushrod passes through the centre of the searchlight mounting tube. As this pushrod is moved up and down, it adjusts the elevation of the light via a wire connected to an arm on one of the searchlight pivots. The pushrod is hollow and tapped with an M2 thread. A length of M2 studding threaded into the end of the pushrod is rotated by a small stepper motor. As the motor rotates the studding pushes or pulls on the pushrod, thus elevating the light. A small scratch built electronic module converts the demand from a receiver channel into step commends for the stepper motor. The motor was salvaged from an old floppy disk drive.
The completed assembly was primed and then painted with Tamiya Gunmetal Grey. The LED is driven from an RC switch and constant current source and is quite bright, even in full sunlight.
4 months ago by Graham93
MFA 919D series geared electric motors
If they are metal
yes - a few drops of light machine oil from time to time.
Helps to keep 'em quiet as well😉
If nylon or plastic
NO! But on the shaft bearings / bushes if metal YES!
Cheers, Doug 😎
5 months ago by RNinMunich
Perfect hobby machines, I'm in the wrong country!. We used to have a lot of small new lathes for sale here in machinery outfits for around $1200 NZ but I haven't seen any for a while. I could do with a small lathe especially for boat stuff. We had a Triumph 2000 (lathe not car) and a Bridgeport mill and all the gear when I was in the site services dept in the big woodworking co I worked for.
I made good use of those, plus in my workshop I had 2 German RS2000 tool grinding machines which were great for touching up all your router bits and saw/ planer blades etc and a Chinese mill which I reco'd when the other guys didn't want to use it. Made my sons cars' frame and running gear (all 10 speed bike
modified etc', -everything adjustable for growth) while I was there . Sure great if you have the gear!
8 months ago by jbkiwi
Stern Module assembly
This weekend I decided to do more work on the Gato Submarine. Now I am starting to realise how big this job to build the model is, let alone the WTC which I am thinking about and starting to plan in tandem.
I have been working on the stern module today trying to get the rudder and aft planes in a working state. I have followed the video made by a kind soul on the internet which I am finding very helpful. To make them fit properly has resulted in a lot of filing and reshaping particularly on the rudder. All of the edges were interfering all over. After a considerable amount of adjusting, they now fit and work perfectly. A hole was carefully drilled right through the height of the rudder to allow for a shaft to be inserted for operation. Small holes were also drilled through some waste material to produce two running bearings for the rudder shaft.
There has had to be a considerable amount of material removal inside the stern module halves to allow for the planes and rudder to work. This was done using a burr in the Dremel and files. Great care was taken not to remove too much and go right through the part.
I am having a little problem with warpage of one of the stern halves. You can see the gap between the parts in one of the photographs. It might be that they will glue together without incident if I fix them well with bands during curing. Does anybody have a cunning plan to straighten this part before gluing?
I have purchased the propeller shafts and tubes so further work on this module will continue when they arrive, probably towards the end of July.
I have now purchased my chosen motors. They are MFA 360. I have also ordered the raw materials to make the motor mount and servo trays. I wonder if I have to put the usual three suppressors on the motors if running a 40Mhz transmitter.
Next time I am going to work on the bow planes. I will have them working and retracting. I bought the
for the retracting mechanism today but have found them to be too big on diameter to fit two side by side in the bow module. The
are perfect in every other way so I think I will reduce them to quadrants which should fit nicely. More cad design work for me I think.
9 months ago by MouldBuilder
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 😉
After my attempts to make and thread a 3mm prop shaft went awry Martin (Westway the Mechanicals Master👍) stepped in and made me a decent one complete with a bushed stuffing tube 👍 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
, 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 coils🤔
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 mate👍
Next steps will be
1) mounting the
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 😉
2) manufacturing bushed end plates to hold the
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 try😉
Pic 9 shows the cleaned up and renovated Taycol Target motor.
Pic 10 shows the drive waveform complete with sparks before modification.🤔
Pic 11 the cleaned 'forward' waveform with the converter board.
Pic 12 the cleaned 'reverse' waveform, no suppression capacitors needed 😉 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! 😲