|Feb 05, 2010, 11:13 PM|
Making Torpedoes for my S-100.
This is how I am doing it. I borrowed a lot of ideas from others on the forum and added my own twist.
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|Feb 05, 2010, 11:25 PM|
How I made torpedoes that work for my S-100 Schnellboot.
The first thing I did was gather all the materials that I thought I was going to need. I hate starting something then having to wait for parts! I used a lot of different sources for my parts, and sometimes you can find local retailers handling the parts, depending on what is available where you are, and most of the stuff was also available online.
1. 1” ID plastic tubing from a fish tank store.
2. Aluminum cigar tube, a 3x3 Chruchill tube is what I used.
3. Magnetic reed switch, HSI-HSR 630RT.
4. Magnets to operate the switch.
5. Wood Dowell to fit inside the plastic tubing.
6. Wooden Popsicle or hobby stick.
7. 3 v lithium photo battery.
8. Brass propeller ¾” Dia.
9. GW/EDP-50XC helicopter tail rotor motor.
10. 1x1 balsa block 1 ¾“ long.
11. Brass tubing of four sequential sizes starting at 3/32” to make the air shaft, propeller shaft, and the stuffing box with bushings.
12. Air tank, line, filler, and distribution valve from a retract system.
13. ¼” Plastic strips for the fins.
Making the Torpedo
The torpedo is pretty straight forward. I absconded with ideas from various threads added my own ideas in order to come up with something that would work for me. Mine are launched by air pressure, and the electric motor starts when it leaves the tube and the influence of the magnet on the reed switch. They do roll some in the water, but bending the ends of the fins helps to counteract the spin of the propeller. They still look great IMHO.
To start, cut the 1x1 balsa into 1 ¾ in lengths and mark out where you need to drill and cut for your stuffing box and fins. Then drill and cut them. I then cut the cigar tubes threads off at the raised rim and sanded them square. The balsa ends for the tubes are then sanded to shape so they are a tight fit in the tubes. Make the stuffing boxes out of the largest sized brass tubing, about 2 1/8” long, by soldering ¼” brass bushings into each end and insert them into the end caps. Insert the plastic fins and cut them to the length of the stuffing box. Epoxy all of the wood to make it water tight
Cut the blades off of a propeller hub that came with the motor and slip the hub onto the motor shaft. It will help hold the fuel tubing flex joint to connect to the propeller shaft.
Drill out the threads of the brand new brass propeller to fit the prop shaft. The shaft should be made from the second smallest size brass tubing and just fit into the stuffing box bushings. The prop shaft should be about ¾” longer than the stuffing box. Solder the shaft into the drilled out section of the propeller. Cut off the other side of the propeller hub and drill/grind it out to make a tapered hole all the way into the shaft. This will make it easier to load in the torpedo tubes when you can’t see into them. The smallest size brass tubing (3/32”) should have a nice slide fit inside the propeller shaft with no binding. Plug up the motor end of the propeller shaft by soldering it shut with a ¼” plug. Don’t forget to grease the stuffing box and run it in so it runs smoothly.
Remove the two wire plug from the motor wires and solder the black wire to the single side of the magnetic reed switch and shrink-wrap it. Solder a section of tubing to act as a conductor to the end of the red wire. Solder a short wire (1”) with a small section of tubing soldered to the other end to the normally closed side of the magnetic reed switch and shrink-wrap it. Isolate the other wire, the normally open side, from the reed switch and insulate it too.
Use a section of the popsicle stick to attach the motor to the end cap with the prop shaft lined up. I cut a slot in the end cap and epoxied it into the proper alignment. Use a section of fuel tubing to make a connection between the prop shaft and the hub on the motor shaft. Use electrical tape to secure the popsicle stick to the motor. I also used electrical tape to attach the magnetic switch to the side of the popsicle stick and the other end to the battery. I also used electrical tape to connect the two wires to the battery. Now, unless you have a magnet holding the switch open, your motor should be running. The magnet will open the switch stopping the motor. If it is turning the wrong way, reverse your battery.
Stuff everything except the magnet into the cigar tube and check the flotation and spin of the torpedo. Put the magnet close to the torpedo to shut it off and remove it to turn it on. Bend the last ¼” of the plastic fins to help counteract the propeller spin a bit and allow it to go in a straight line.
I believe air pressure is the easiest way to launch torpedoes, and it is an authentic method used in WWII. It has one moving part, the air distribution valve that is servo controlled.
I cut the 1” plastic tubing to a length that included the angle at the bow doors, the length of my torpedoes, and the rear plug. The angle at the bow will be determined by your model. Add ¾” to the length for the wooden dowel plug for the rear and make sure that your torpedo is completely enclosed by the tube.
Find the center of your wooden dowel plug and drill a hole through it that will hold the 3/32” brass tubing. Measure the length of the inside of the torpedo prop shaft and add 1” to it. That will be the section that delivers the launching pressure to the torpedo. Glue the brass tubing into the hole in the plug and glue the plug to the plastic tube. You should have about ¼” sticking out of the back of the wooden plug to attach your air line to. You can also add parts to hide the air tube and make it look like the rear of a real torpedo tube like I did. I soldered a 90 deg. tube to it so the tubing can be hidden under the deck.
You can install the air tank, fill valve, and air distribution valve where ever it is most convenient for you. Attach the air lines and check that everything works.
Glue a magnet to the outside of the plastic tube so that it shuts the motor off while it is in the tube and where it won’t be seen. Slide the torpedo into the tube so that the 3/32 tube slides into the propeller shaft and rotate it so the magnet keeps the motor shut off. Fill the air tank and test the operation. Don’t be surprised if it takes a lot of pressure to launch them. They are not the lightest of torpedoes.
Have fun and amaze your fellow boaters, just don’t sink them!
|Feb 07, 2010, 05:25 PM|
Working on video. I'm still installing the new tubes in my S-100 and I am only about half done. Everything has worked flawlessly on the bench which is why I did the post.
|Feb 20, 2010, 11:26 PM|
The installation of the tubes has been almost completed. I still have to adjust the servo throws for the doors and the air valve. I have also adopted some of my static torpedoes to launch with the air system. They are all working well so far. I will make a video as soon as I can get someone to film it.
|Mar 07, 2010, 07:55 PM|
I have uploaded a .mov file on the water test of my torpedoes. I need to increase the fin area to counteract more of the spin from the propeller.
|Mar 11, 2010, 10:37 PM|
I have downloaded a video of launching static torpedoes from my
S-100 in the boat video section. They won't let me post it here because of the file extension of .mov.
|Mar 20, 2010, 02:05 PM|
Through experimentation and burning out some of my synapses, I have gone to small 3.7 Li-Po batteries from the small helicopters. By encasing them in the cut off fingers of latex gloves, I will be able to keep them dry just in case any of my torpedoes spring a leak. So far, none have. The motors are faster and the torpedoes are lighter than with the 3v camera batteries.
|Mar 20, 2010, 07:48 PM|
GreenOne - Lipos are encased to keep out air, so they are already waterproof. I run my floatplane w/o any percautions, and the battery gets wet every time I dump :-). If you wrap them in a glove finger, be sure to open it after returning home so as to let out any trapped water or humidity from a waterdroplet - this is to stop corrosion. I just let my plane lipo's dry on the bench. My rx is wrapped, and needs protection. My esc has glue (GE siliconII) in the ends of the shrinkwrap since esc's will fry if they short.
|Mar 20, 2010, 10:15 PM|
Thanks Brooks! For awhile there I was wondering if I was going to be the only one to comment in this thread. I'm wrapping them just for my own piece of mind, and intend to unwrap them upon return to the dry dock.
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