Internal Workings of an R/C Submarine

[GBerger]

Here are some photos of my 1/32 Balao when it was operational at Mt. Trashmore in VA Beach. Yes, it did have a short stint as the USS Sea Tiger at a SubCommittee regatta up at Groton some years back. Since then it was repainted a more traditional color. I'll post more in time and some construction photos. Now it currently sits on a shelf while I entertain myself with other projects.

[greenman407]

Crosman penetrator

[greenman407]

Dont let Mr. C see this.

[greenman407]

Also........quite alarmingly I picked up again on a Hobby that I havent indulged in for years. Air guns. Yeah Ive been relaxing in the evenings blasting Pellets thru 1" thick wood boards. Unlike the BB guns of my childhood, the modern Break Barrel guns will drive tacks into wood for sure. Many people use them for hunting Racoons and such, especially the 22 cal models. I, however dont shoot at anything alive.
They have a pellet these days which are just like the "Sabot" anti-tank rounds. The projectile is housed in a plastic body that seals to the inside of the barrel while the projectile is much heavier and smaller than the bore. They call them Penetrators. While a BB or a lead pellet will bury itself into the wood and stop, the penetrators blast there way all the way thru.

[greenman407]

Hey Al! Yep, its been some time. The Oscar is just sitting on her display shelf. That seems to be the nature of the hobby for me. If you are always working on a project, then it stands to reason that your other past projects are just sitting there, waiting to receive some attention again.
Im about at the point of starting another one. Ive been promising to start up on the Skydiver. Also been promising starting on the Skipjack. Not to mention, I like the looks of the Bronco type 23 and am contemplating the Type IX. So with so much aspirations as well as the ocassional desire to spend some time with my model speed boats, im kinda ..................fully booked.

[Anuci]

Hey Al! Good lookin out!

Hey Mark,
Don't know that I should be thanking you right off, as I really can't say I was able to decipher your comment as posted. Is this comment like a Cryptogram ?
Will I need an Enigma machine. :wink: How's your Oscar II doing, its been a while.

[greenman407]

Hey Al! Good lookin out!

[Anuci]

Hello Andy,
That's a good question, and I'm glad to hear you haven't experienced any such issues with your set-up, and maybe this incident is isolated to me.
First let me say because of the arragement of the various cylinders within the hull of this particular boat of mine, it may be a bit unique, in that there are three (3) separate wtc's within the hull. There is a cylinder which is used to house the Bowplane Retract Mechanism, another for the Main Battery Compartment, and then there is the actual Sub-Driver (WTC) itself. The wiring is externally located and interconnected between these various components for purpose of utility. Each unit at times may require servicing and removal from within the hull eg. to access the battery, etc, thus the elecrical wiring and connectors are removed from there respective electrical bus. to permit such removal. Over time water corrosion, and general wear encountered in the removal and re-attachment of these particular wiring connectors, they will then become brittle and the inner wire strands subjected to fraying.
The end result is what has been described in my previous post. I'm sure there may be another way of skinning this cat, such as maintaining the connection to the external power bus. and using a different type of intermediary connector such as a deans or the like to connect and disconnect, and I may look to do just that in the future, as this may prove to limit the wear and tear to the actual connectors POS/NEG mounting to the outer face of the cylinders end cap.

Hope I'm being clear with this explanation.

Regards,
Al

[Subculture]

I've never experienced many problems with cabling over the years- perhaps I've been lucky. Do you pull the wires about a bit?

[Anuci]

I'm beginning to think I should start off these posts with " Once upon a time", but I simply thought I'd pass this info on as a pretext to how electrical connections and the water they are subjected to can be at the route of much of the evil we experience from time to time in this particular hobby.
I had recently found that while all the accessories intalled within the motor compartment of my sub-driver were working fine, the motors themselves would not respond to command of the TX. While I continued to throtle up power on my transmitter I further discovered the servo's would begin to glitch. While in the process of diagnosis, I not only made a preliminary visual inspection of the boats wiring, but also conducted a test with my voltmeter to determine if electricity was making its way to the various electrical bus terminals as well as the electronics within the motor compartment. I found that upon using another externally connected battery, and one which was connected directly to the motor bulkhead power bus, this revealed positive results, and all worked fine.
I was prompted to then pull the 11.1V lipo battery from within the battery compartment of the boat, and conduct a direct connection of that battery to the motor bulkhead power bus, as I did earlier with a 7.2V Nimh battery pack. I was happy to see everything then working as it should.

With this new info. and eliminating suspected possible issues with the battery or maybe even the ESC as the source of the problem, I then went on to re-examine all the remaining electrical wiring connectors within the boat much more closely, rather than depending entirely upon the readings from my voltmeter to determine how much power was being provided to the various bus terminals. This closer inspection revealed two of the battery connectors while visibly appearing OK, internally they were most likely compromised by broken wire strands, obviously not permitting the full power from the battery to pass on as it should.

What I learned from this examination process was that although the voltmeter had indicated sufficient voltage passing through the wiring from point (A) to point (B),
ultimately there was insufficient voltage to power the motors while under load. As result, I then replaced the connectors on the battery compartment bus. and proceeded to conduct further testing of the main power to the motor compartment and various electronics which only then revealed positive results.

Hopefully this info. will be of use to someone with a similiar concern, and help with diagnosing such issues. If I have learned anything in these diagnostics steps is that you be well served to look at the simple cause rather than jumping to conclussions. Replacing or addressing items which are least costly first, and then moving on to the next possible culprit in the series of offenders should help keep repair costs down.

Until next time, "Keep a steady bubble".
Al,

[Anuci]

In a follow-up to my earlier posting, this regarding my decision to install a stand alone BEC.
Let me begin by saying all is fine and running well for the most part at this point. This as result of changing out one bec for another which Caswell was stocking. However, as I'm sure the instalation of a stand alone BEC will ultimately be for the better, I'm not exactly sure of a couple things which I found as result of this instalation.
First off, although all of the electronics appear stable and glitch free, I am now finding some variation in motor speed at pre-set speeds. The RPM of the motors appear to increase and decrease slightly when running at these pre-set speeds in a pulsating manner, as this was not realized when previously using the bec which was built into the speed controller.
Second, upon initial power-up of the motors there is a slight hesitation both in forward and reverse , and the speed of the motors are less controlable at low end, accelerating quickly at the slightest throttle-up. I may look to re-program the speed controller to determine if there is any substantial change to any of these conditions.
Let me first point out that my decision to use a stand alone BEC rather than the bec unit incorporated within my ESC was more of a precautionary measure, and not because of any direct or indirect issue I had been experiencing with any of the electronics within the motor compartment, this and as a direct result of the number of on board devices drawing power off the low amperage output of the BEC built into the speed controller I had been using .
To finalize, at this point I fully intend to continue with the set-up as is, looking to further evaluate the operation of the boat when out on the pond. If I feel the need, I may decide to simply return to the previous set-up, using the ESC's battery eliminator circuit.
The BEC unit was by far one of the least expensive devices purchased thus far, so, no harm no foul were my thoughts.

Until next time,
Keep a steady bubble!

[Anuci]

Subculture has graciously provided an explaination between the two types of battery eliminator circuits ( BEC's ) in these following comments, and further pointed out that the BEC presently stocked by Caswell is of the switchmode style of voltage regulator. Thanks for this easy to read explaination, Andy.

A switched mode supply basically works by switching an inductor coil in
and out very quickly (usually about 400 times a second). They can be
configured to drop or increase voltage, called buck and boost respectively.

A magnetic field is induced in the inductor when it is doing this, and
it is that which makes them electrically 'dirty'.

Best quality units will have a grounded metal shield around them, steel
being best, but aluminium works and is lighter. That deals with the
inductor on the unit. Also a ferrite is usually wound around the output
lead to nix any nasty frequencies induced into the wiring by the conversion.

A simple analogy would be to imagine you're watering the lawn with a
hosepipe. The water pressure is too high, and you can't adjust with the
tap, so what could you do? Well you could add a bypass, and shunt a bit
of the water off down the drain, that's your linear BEC. Or you could
get some one to squeeze the hose on and off with their foot, that's the
switched mode. The latter mode doesn't waste any water, although energy
is expended by the person doing the squeezing- hence switched mode
supplies are never 100% efficient.

Linear converters don't create any dirty fields, but they generate a lot
of heat when the voltage differential is high and the current demands
are great.

For example. Lets say we have a model submarine operating off 12 volts,
and we want our usual 5 volt feed to the radio kit. Let's also assume
the current required is 1A, which is adequate for two or three servos if
they're not stalling, or thirsty models.

To see how much power is wasted in heat, we subtract 5 volts from 12
volts, which is 7 volts, and multiply that with the current, which gives
us 7 watts of power wasted in heat. That's 140% greater than the power
being delivered. Can you say inefficient? Plus you'll need a sizeable
heatsink to get rid of the heat if the regulator is to survive.

If the model was operating on a lower voltage, say 7.2 volts, then
things become much more benign. 7.2-5= 2.2, times that by the current
equals 2.2watts, under a third of the power wasted. Hence why linear
regulators work best in low voltage boats.

An equivalent switch mode supply will only use about half a watt.

[Anuci]

Hello all,

I'm revising an earlier posting here regarding my latest addition of electronics to my Gato boat.
Well it has been a while since I've installed the stand alone BEC ( battery eliminator circuit ) to the mix of other electronics within the motor compartment. This is the unit used here: http://www.activepowersports.com/cas...ing-regulator/
While initial testing of the various on board equipment after the instalation of the BEC appeared to all perform satisfactorily, later testing resulted in glitching of other various devices with either negative or pulsating power surging of the motors, this both while running in forward and reverse, At first, I thought this issue was the result of low battery voltage as it appeared to temporarly correct itself later when a fresh battery pack was used. However, when at long last I had found some time to take the sub to the pond, and while making preparations to do just that I discovered this problem resurfaced, showing its ugly face once more. Oh brother!, needless to say the mission was cancelled. Long story short, I disconnected the bec and found all ran well once again. Yea, I don't have a clue. Having said that, I do remember there being a difference between the various bec devices, eg switching vs. linear. Along those lines, I'm not quite sure if there is in fact any direct relationship with the type of bec used and the issues which developed after installing the Castle Creation BEC mentioned here. As an alternative, and when in doubt, I generally try something else. In this case I've ordered a battery eliminator circuit as advertised here on the Caswell forum and will give it a shot. I'm of the understanding it is of the linear type and I'm hoping to get around this issue with this particular type of BEC. Stay tuned!
In the mean time I've removed the previously posted info. regarding the Castle Creation 10A switching regulator, simply to play it safe, as this particular device may not, and I repeat may not be best suited in with the mix of other various electronic components crammed into the confines of your subs motor compartment, this due possibly to excessive noise output within the unit itself.

[Kazzer]

Great - so we can buy these from Caswell? Any specs on these please?

J

http://www.sub-driver.com/battery-eliminator-circuit.html

[Slats]

An excellent observation as to the receiver bus needs of our submarines, John. Clearly the stock ESC's (specifically, they're BEC circuit) are not up to the task of supplying device current load at the 5-volt needed off the receiver bus. Other than 'robots' I can't think of any other r/c vehicle out there that presents a higher current draw off the bus than r/c submarines. It has been through Andy's and your prodding that finally convinced Mike and me to secure, offer, and promote use of a dedicated BEC within our SD's. Thanks, guys.

David

Great - so we can buy these from Caswell? Any specs on these please?

These are the one's I use:

http://www.hobbyking.com/hobbyking/store/__4319__TURNIGY_3A_UBEC_w_Noise_Reduction.html

J