HMS Astute: More curious receiver/electrical problems

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and a couple more

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Thanks, will give this a go.

[JWLaRue]

While you have an 8 Amp-Hr battery it's highly unlikely you are consuming 8 Amps!

I do believe that you found the (major?) source of your problem with the battery not being fully sealed to water.

Ralph is spot on regarding antenna alignment issues.

Regarding "The 'pulses in water' issue is likely caused by parasitic or induced currents flowing in the water surrounding the pressure hull"....what kind of water are you running in?

-Jeff

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While you have an 8 Amp-Hr battery it's highly unlikely you are consuming 8 Amps!

I do believe that you found the (major?) source of your problem with the battery not being fully sealed to water.

Ralph is spot on regarding antenna alignment issues.

Regarding "The 'pulses in water' issue is likely caused by parasitic or induced currents flowing in the water surrounding the pressure hull"....what kind of water are you running in?

-Jeff

Hi there, so far she has had around 17 or 18 diving sessions: three in a chlorinated pool and the rest in fresh water lakes/ponds. The pulse issue was worse in chlorine but present everywhere. The water round here comes from chalk springs though, so it is very rich in calcium - i.e. 'hard water' - which might, conceivably, make a difference?

But otherwise, as I said, the problem is trying to devise any kind of explanation when the obvious things - components - tested negative. If the aerial is fully sealed, which I believe it to be, (the problems remained even when I put the old aerial inside the wtc) then I assume there is likely some kind of electric field in play, which is somehow enabled by the presence of water, working with the wiring layout and/or unsealed batteries.

If not, then perhaps the unsealed battery/s where achieving enough of a short through an inch or so of water to the prop shaft to mess with the motor? But how this took place via the only available connection - i.e. two working capacitors attached to the motor can - I don't know.

But again, as I said earlier, the properly sealed pack solved the pulsing when water reached the shaft... but not when the wtc itself, or aerial, was submerged. Meanwhile, no problem was exhibited when the front end of the wtc entered the water, until it reached the aerial that is.

Alternatively, or perhaps at the same time, the presence of water attenuated the signal below which the receiver could work. But this is distinctly odd since the Corona company sets great store by the very long range of their units, being, apparently, up to a mile (in air): one of the reasons, other than the very small size, that I chose it.

Pretty darned mysterious, the whole thing.

On the bright side, being forced to check everything helped me improve a number things in the original design. For example, I close twisted the main battery cable and fitted a small ferrite choke to the lines in and out of the esc. And I'm pleased with the result overall. She is very quiet, will hover well if coaxed and, apart from filming the local fish, is sufficiently docile in handling for my 12 year old to enjoy using her. The hydrophone is entertaining too and will be great fun if I get to any kind of club meet.

[sam reichart]

my thanks to the collective brain trust here for their assistance and knowledge given to this poster. brand new person on the boards, and lots of responses. you guys rock.

[JWLaRue]

Hi there, so far she has had around 17 or 18 diving sessions: three in a chlorinated pool and the rest in fresh water lakes/ponds. The pulse issue was worse in chlorine but present everywhere. The water round here comes from chalk springs though, so it is very rich in calcium - i.e. 'hard water' - which might, conceivably, make a difference?

Alternatively, or perhaps at the same time, the presence of water attenuated the signal below which the receiver could work.

Given the water conditions you have described, it would not surprise me that the level of chlorine or calcium is causing severe signal degradation. We experience this in the indoor pool we use to float our boats at the end of every season....before the pool gets emptied and refilled. The level of particulate matter (plus the chlorine) causes some boats to lose signal when no more than 10 feet away and 2-3 feet deep.

But again, as I said earlier, the properly sealed pack solved the pulsing when water reached the shaft... but not when the wtc itself, or aerial, was submerged. Meanwhile, no problem was exhibited when the front end of the wtc entered the water, until it reached the aerial that is.

I'm still thinking that there is still some exposed component tied to the power bus or the aerial was not sealed (when you had it outside the WTC). I would still like to see a photo of the front of the bow end cap.

-Jeff

[eckloss]

Can I just say something....

When I got my own 1/144 Astute kit, I too had dreams of r/c'ing it. But My talents are lacking when dealing with very small stuff. Probably no way I could have pulled that off.

Very, very well done! Superb job, Sir.

-erich

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Given the water conditions you have described, it would not surprise me that the level of chlorine or calcium is causing severe signal degradation. We experience this in the indoor pool we use to float our boats at the end of every season....before the pool gets emptied and refilled. The level of particulate matter (plus the chlorine) causes some boats to lose signal when no more than 10 feet away and 2-3 feet deep.



I'm still thinking that there is still some exposed component tied to the power bus or the aerial was not sealed (when you had it outside the WTC). I would still like to see a photo of the front of the bow end cap.

-Jeff

Hi Jeff, picture of the front attached



The red button looking things are the brass screw caps respectively for the battery postive and the postive-switched circuit - for torpedo pump or cameras or whatever. the corresponding ones on the other side are battery negative and negative-switched connections, the latter of which is the negative terminal for every system on the boat. the slotted end things are the brass wtc retaining collars. These and the rods they are attached to are electrically isolated and carry no charge - last time I checked anyway. The hexagonal brass thing is just a stop to replace a schrader valve I had installed for leak testing - before it occurred to me that this design self-pressurises! Besides, it started to leak itself.

Was quiet for a while as I fitted a new esc. The same make, a mtroniks viper 10. No real change except slighter smoother responce when you increase the turns. Also removed a brass reinforcing strut that passed just in front of the forward end of the wtc. Slight signs of corrossion where it was near the negative terminal. I also fitted a new better battery pack. All these changes seem to have improved the radio performance a lot although not quite to the standard I had hoped for. Nevertheless she is now serviceable.

Erich, thanks for kind comment. If anyone ever produces an affordable 1/96 ish version of one of these I'll be a taker. Working with all the room available in a 3" wtc would be a real pleasure.

And to everyone else many thanks for taking the time to share your valuable experience.

I'll be back next year some time with a trumpeter Seawolf into which I hope to add a working active sonar. Thanks to the marvel that is cheap Chinese technology parts, I have some very small adjustable signal generators, a small speaker, loads of tiny microphones and the smallest oscillascope you've ever seen. And I've already established that fm signals work really well underwater for the distances needed in that project. Fingers crossed.

[JWLaRue]

It's difficult to tell from the photo, but it appears that your battery terminals are exposed to water? That could cause some issues.

Also, for the external antenna....how did you waterproof the far end?

-Jeff

[salmon]

I agree with Jeff. There are several areas of concern.
There is heat-string tubing in several locations. I do not know if it is for bundling cables but there appears to be a couple where that is not the case. Those need to be sealed because water will get inside. Something that I do now is put a bit of silicon rubber on the wire at the location of a soldered area (making sure the solder is good) then slide some heat-shrink over it then let it set for a few moments, not long, then use a heat gun to shrink the tube. You should see silicon ooze out each side. I also do this at the end of my antenna. Did you modify or cut your antenna?

Your battery connections/terminals as Jeff mention need to be sealed too!

All of these will cause problems.

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Hello again, managed to find some time to do a bit of experimenting. I got an FM radio and tuned it to 87 mhz - the closest you can get to 40Mhz on a conventional set here in the UK. Leaving the aerial fully retracted - I only wanted to pick up stuff close by - I passed this closely over the model while powered up.

There was a lot of noise generally but the noise from the after end, over the stabilizer, was extreme - sort of like morse code with a rythmic thrum in the background. This would explain the total loss of signal when I previously tried to move the boat's own aerial toward the aft. Interestingly the main power line - the one I close twisted with a drill - was actually very quiet. The worst offenders, after the stablizer, were the servo leads.

So, I covered the stabilizer with 'cling film' or sandwich wrap, then some aluminium foil and then another layer of cling film. This killed the noise totally.

Then I moved as much wiring as possible to the 'lower deck' - there was much too much near in the top half of the cylinder, then I reduced the remaining cable to as much as was practical and braided some servo leads.

The result is that my radio, a Futaba, F14, now works - with its aerial fully down (telescoped in) - out to about 33 feet or so, up from the nine or so feet previously. I think that is probably as good as I can hope for...

Couple of other things.

Exposed contacts: these seem to feature in one form or another on quite lot of other models. It is not a great set up, I know, but there is little room to do things any other way. Also I am reluctant to put cables through the end caps because these are hard to seal and incovenient when you need to remove the end caps for inspection. Do we know of any good, small waterproof connectors that might serve in this set up?

Heatshrink seals: Salmon the method you describe is exactly what I do. I sealed the 'mission electronics' this way and thus the camera transmitter and radio are all still working after several dives.

Motors: I decided to refit the mtroniks motor in the end because the operation was smoother and the batteries last an hour or so in use. The MPA motor I tried out is faster but drains the batteries so flat in 15 mins or so that it is difficult to get the boat back in. When I rev the motor you could see the needle drop from the power draw on the little ammeter I fitted. but with the mtroniks unit there is barely a flicker, even at full throttle. It seems to run on nothing.