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Thanks for pointing it out. I apologize; I meant 0.25 L - 250 ml!
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Alberto,
Please share more info about your Type VII.
Thank you.Make it simple, make strong, make it work!Comment
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congratulations!Who is John Galt?Comment
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Absolutely. Thanks for asking, and sorry for the delay.
The model is the Revell Type VII, 1:72. I have to say though that it is a very messy project and after seen the quality of work around here this will look like a Dr. Seuss artifact! When I started a few years ago my experience was zero, and I was not aware on this forum. Hobby stores in my area were clueless about RC submarines, so I figured thing out as I was going.
To resume, the biggest challenge by far was trying to achieve a practical way make the joint between the hull and deck and, at the same time off course, keeping the parts easily detachable in order to access batteries and systems.
I tried attaching a rubber lip in the hull, which would be compressed by the deck held tightly in position with magnets, but water leaked. I also tried attaching small surfaces on the inside of the hull, where holes could be drilled and tapped, therefore, once the deck was put in place, would be secured it with screws. This idea failed due to the space needed for the parts involved.
Finally, giving up, I just sealed hull and deck with a ream of silicone, achieving an effective seal...which had to be cut away every time I wanted to re-open the hull! This eventually ruined the sides of the submarine and the deck.
The watertight glands for rudders and forward diving planes was achieved by using 2.35 mm diameter steel rod and 3.2 mm OD copper tube. They created an effective seal due to the small allowance between the surfaces. A bit of vaseline lubricates and ensures that no water over time leaks in.
The after diving planes was a different story: I figured that if I tried to install the same glands as the rudder and forward planes, there could not be too much room for a firm attachment of the the copper tubes, thus creating the risk of ripping them off in the event of collision at sea or while moving the model around. Instead, I copied the Biber midget submarine system, in which the push rod passes through the hull, and it is attached to a linkage on the plane itself, with the variant that my linkage was attached to the plane's shaft. Not orthodox, but it worked well. Both bow and stern planes are operated by one servo, while the rudder uses one servo with push rods.
The propulsion shafts are on-the-shelf Graupner units, and the twin motors just cheap brushed units, which actually perform really well.
The ballast system is made of a vented tank (a piece of PVC pipe sealed at both ends) with water suction/discharge through a two-way gear water pump and solenoid valve, and two check valves. When pumping in, the air discharge (and eventually water overflow) goes overboard through an alternative outlet under the water line, while when pumping out, the air suction is achieved through a pipe on the conning tower (installed on the location of the sky periscope).
An electronic switch operates pump and solenoid valve with one channel.
As for the power, I used two 7.2 V, 1800 mA NiCad batteries in parallel. The ESC is turned on/off with the aid of a Reed Switch. The plant runs for at least 1.5 hours.
The Tx/Rx is a 6 Ch. Futaba 72 MHz, of which I only use 4 channels (Throttle, rudder, planes, ballast). The Rx is installed on top of the ESC and the antenna runs along the length of the hull. The disturbance is really bad, and the servos twitch a bit...sometimes even the ballast pump runs by itself for s few seconds! I was to try ferrite rings, but I don't know if it would make any difference.
I will try to attach some pics and diagrams.
Alberto.Attached FilesComment
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Lots of failure points. So which one caused you to lose your boat?Make it simple, make strong, make it work!Comment
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Some more...Comment
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The suction/discharge fitting on the ballast tank got loosen due to failure of the epoxy glue, so when I pumped ballast in, water partially flooded the dry hull.
As you correctly said, a lot of points where failure may happen.
By the way, these pictures uploaded as thumbnails...they are too small!
AB.Comment
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What a relief that you have retrieved your sub! Congratulations.If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.Comment
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It was multiple reasons. My pump motor was acting funny. I should not have made the sub run the next day until I replaced that motor. The other issue is I had it trimmed so a little of the conning tower was above water. When the sub went down, probably from a radio being turned on (surface boat), it dove deep. past 4 feet the compression on the foam made my positively buoyant sub no not so positive buoyant. The last part did not bother me because the pump would bring it up if I could not get it. Well this time the pump failed again under a perfect storm situation. I did not add a gas emergency tank to the sub. It is still in in the lake (I believe). Hopefully the fire department up at Keystone will do a search and rescue for it. They wanted to search last year, but a forest fire called them away.Last edited by trout; 06-16-2016, 06:50 PM.If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.Comment
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That your system got activated by someone else's random command is unfortunate...I hope you retrieve it some time soon.
Cheers.Comment
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