Thunder Tiger Neptunes troubled first voyages.

[Schmitty1944]

I've never really liked the Thunder Tiger Neptune. It's not a scale model. It's layout doesn't even make sense. What is the bubble on top? why do the side windows have a cage over the outside that isn't even touching the window? shouldn't that be on the inside? It has ugly external linkages. worst of all it just looks like a cheap plastic toy. But after I watched Bob's videos with the steampunk conversion and he said how fun it is to run I thought I should give it another look. I bought a used one in the usual clapped out condition. All batteries DOA, appears to have been painted yellow (don't know why since it is already yellow). Upon taking it apart I was very impressed with its internals. The WTC is very well designed and looks like it could handle some real depth. Here's where my troubles with it began.

After replacing the batteries I found everything to be in working order. Backyard pool test #1 showed it to be completely functional but way out of trim (very stern heavy). I also found that anytime I submerged the radio would loose signal frequently. So I took it back apart and range tested the radio out of the cylinder. The radio was the original Ace Sea Commander and although it generally works well I found the range to be rather short and sometimes the radio would just start glitching even when at very close range so I changed it to a Futaba PCM. I also moved the ballast farther forward and cleaned up the wiring inside the hull.

Backyard pool test#2 shows it is still heavy in the stern even though I've got all the ballast as far forward as it is designed to go. I also find that although considerably better the range is still not very good and often looses signal when submerged. After about 10 minutes I find the model is still going but will no longer surface. I lift it out of the water and the ballast pump is not running at all either direction. Bring it back on the bench take it all apart again. No sign of leaks. when turned back on now the pump works fine again but the main drive motor has stopped working. The original Ace Veloci ESC seems to not detect the receivers output. What is going on with this thing?

My main question is about the antenna. As designed the receivers antenna makes a few laps back and forth and around the inside of the WTC. The cylinder itself has a wall thickness of just under 4mm and the end caps are nearly 7mm thick. That's a lot of plastic for the signal to penetrate. Is this a known issue for this model? have others experienced short radio range? would putting the antenna outside of the WTC likely solve this issue? My pool has salt/chlorine in it but not much. I have run other subs in it without any real trouble.

Any ideas why the ballast system shut down while on patrol? battery was good. Can't find anything wrong. On the plus side I can see that when working properly it is a great pool toy. It turns incredibly sharp and in general has good characteristics. Sure is easy to see in bright yellow plus this one has flood/nav and strobe lights added that can be turned on and off from the transmitter.

thanks for any thoughts
Jason

[SubDude]

My son's, (Bob's old Neptune) works great to the point that I have not had a reason to have to take it apart yet. I have heard of issues with the stock ESC and people replacing it with something different. His doesn't have any tail heavy issue. The salt in the pool certainly doesn't help but to what extent I am not sure. Have you tried it in some plain fresh water to see if it makes any difference?

[Subculture]

Electronic issues were very common on the early Neptunes. i think they straightened out their quality control on later versions, but that won't help you much now.

The ballast tank control board is a relay based affair, which tend to be more failure prone than transistorized units, in addition many suffered from cold soldered joints, so it can pay to have a gander at the board with a magnifying glass, and re-sweat anything that looks a bit suspect. Sticking relays and cold solder joints often manifest themselves as intermittent failures.

Some owners ditch the board and fit an esc, fair enough but you'll lose some of the functionality without mods e.g. pressure sensor connection, failsafe and water detector.

The ESC can also be a bit dodgy, worth fitting a better make and also a separate switchmode BEC.

[Schmitty1944]

Thanks for the input. I had replaced the lead acid battery with Nimh because it was slightly cheaper, has quite a bit more capacity and a little safer so had to make up the weight difference with more ballast. You can see in the picture how far forward the weight ended up being to get the trim level but it does work well now.

I did run the antenna out of the pressure hull through a tube in the stern sealed with silicone fuel tube on both sides. I chose the stern end cap because this rarely needs to be removed. Further tests show the occurrence of loss of signal have been greatly reduced but not completely gone. Must be the salt in the pool. I have not run the model anywhere else yet mainly because I don't trust it to run in the wild so far due to its proven unreliability.

The next morning after test#2 the original ESC was working again but I swapped it anyway. The one I put in (I just had in my parts bin) is a duratrax blast. It's only rated for 8 cells but so far seems to work fine at 12v. I looked over the ballast control board and can't find anything wrong at all. No suspicious solder joints etc. When it stopped working there was absolutely no response at all. No Leds, no relays clicking...nothing. I didn't think to just turn the boat off and back on until after I had it on the bench in pieces. since that one incident it has worked perfect so it's still an unsolved mystery.

I ran the model in the pool twice yesterday without any trouble at all except for the occasional loss of signal. This is with a PCM radio so when signal is lost I have the failsafe set to turn on all the lights stop the drive, center all controls and blow ballast. The pool is about 3 foot deep. It would occasionally momentarily loose signal when at or near the bottom.

[He Who Shall Not Be Named]

Seal the outboard end of the antenna or water will work its way through the conductor and into your receiver -- will take a year or two, but will happen.

When you open up the boat, turn it on, and if everything is working flex the control board and look for drop outs. If they occur start pushing the board with the eraser end of a pencil till you identify the bad solder joint(s). Fix! You don't need this problem haunting you as you can be assured it will all go belly-up the moment you sail over deep, uncharted waters!

David

[Schmitty1944]

Thanks David. I did in fact already seal the outer end of the antenna. I have heard of that problem coming up before. Good idea to try flexing the ballast control board to find faults. I haven't tried that yet but will. You are absolutely correct, just as I'm crossing the Marianas trench is when the radio will lose signal and the ballast system will go dead again.

Jason