SD25G sub-driver - more info please

[Bob K]

I am hoping someone can help me, I am a little stuck assembling the electronics in my SD25G WTC

The PDF assembly information on the Caswell site is really useful, but illustrations show the Seaview version of the motor compartment which is completely differerent from my Gato one. I am building a K Class submarine.

I am trying to figure out how to mount the servos, micro-ESC, etc. It looks like the only way is by cutting the mounting lugs off the servos and sticking them in with double-sided or tie wraps? Does anyone have a photo of the Gato version of the WTC assembled please, also if possible a connection diagram showing how all the numerous electrical assemblies go together. I have a WFLY Tx/Rx.

6 servos were with the kit. I assume I need at least 4, possibly 5 with one in the battery compartment for the front diving planes. I understand that the auto leveller works the front planes, connecting between that servo and the Rx unit.

Rx channels ? - I have 6 channels
1 Motors via ESC (no servo)
2 Rudder - via servo
3 Rear diving planes - via servo
4 Front diving planes - via servo & angle driver
5 Snort system via snort PCB (no servo)
6 Retracting funnels & front diving planes - via servo in battery compartment?
7 Gas ballast blowing, not sure

Because my K hull is extremely tight for space around the WTC I was hoping to build and bath-test the WTC before cutting holes in the hull and epoxying control components in place. I can't move large holes or epoxyed shaft / bearing tubes in hindsight. Also, If I build the hull first, fixing the shafts into a correct scale position I could inadvertantly end up with part of the WTC sticking outside the hull unless I get the WTC built first.

Once I can get the WTC operational I will be a lot more confident in constructing the rest of the boat.

Bob

[He Who Shall Not Be Named]

The GATO SD you have, I gather, has the old style device mounting rails. I have since dropped the rails and now sell that SD with an improved device mounting tray and servo mount. Give me your address and I'll send you one. The below shots will show you how to install the servos and servo pushrods.

Unscrew the old device rails from the motor bulkhead and discard. Install the new device tray with attached servo mount using the single stud on the bottom of the motor bulkhead -- insert the insulating washer to prevent contact of the antenna lead to the aluminum structure. Note that it is made fast with a thumb-nut.



The servos are made fast with RTV adhesive. The 1/16" pushrods are carefully bent to shape so that they clear the centrally mounted SL-8 receiver (discard your WFly receiver as it is unsuitable in this application). Use a servo setter or the r/c system to insure your pushrods run through the pushrod seals with minimal resistance.



The SEAVIEW and GATO device hook-up is pretty much the same other than you have a dedicated channel for the retract mechanism, and there are no servos up forward, they all are located in the after dry space.

The ADF angle-keeper hooks up to the stern planes, not the bow planes.

Don't get fancy with this K-class model yet -- keep it simple. Here are your r/c system channel assignments:

ch-1 rudder
ch-2 bow planes
ch-3 throttle
ch-4 blow/vent
ch-5 stern planes
ch-6 LPB

Buy yourself an SL-8 receiver.



David

[Bob K]

Huge thanks David, greatly appreciated. In fact the cast resin servo mounting looks very much like mine, rather than the folded aluminium one with tie wraps I had been looking at.
This makes things a lot clearer. So I do need to cut the servo lugs off and mount with RTV sealant. It appears that all electrics, except battery, go in the aft motor compartment. Assume ESC goes under the plate, with ATF on top between the servos, and that Rx and snort pump with PCB mount forward of the aluminium bulkhead? ie: Keeping Rx away from motors & ESC.


Glad you said to use an SL-8 receiver as I was going to fit the one that came with the WFLY. I will order one from Caswell. I know the Rx aerial needs to connect to the external one via the stud terminal under the motors.

With all controls coming out aft this should make removing WTC for servicing and battery recharge easier, and more easily defines how I position mount and operate planes and rudder etc.

This is beautifully compact, which is good as it is all going to be a very tight fit inside the K Class hull, hence my caution having never built a sub before. My WW1 cruiser only uses two channels !

Bob

[He Who Shall Not Be Named]

As to device placement:

The receiver goes atop the servo mount, sitting in the center, between the tops of the servos. The ESC is mounted to the forward face of the aluminum bulkhead. The ADF and Lipo-Guard are servo-taped to the sides of the servos. The LPB with attached MPC fits below the servos.

All that stuff, so tightly crammed in next to those motors, demands the finest receiver in the world -- that's why the Sombra Labs recommendation.

David

p.s. Mike: why the hell dosn't this damn 'spell checker' work?! You trying to make me look like a dope!?...

[Bob K]

I just checked out the spec for the Sombra Labs SL-8. It is available for either 72/75MHz or 50/53 MHz.
70 & 50 are not legal frequencies here - Sorry
In the UK we have to operate on 40MHz, which is why I got the 40MHz WFLY Tx/Rx.
Problem ?
PS: I assume "Lipo Guard" is to protect the batteries, another unit I need to source?

[He Who Shall Not Be Named]

Damit!

You Brit's!?....

Another receiver is the SL-6. It's crystal controlled, so you'll have to come up with a mini-crystal within the band you can operate over there. But I don't see it available on the 40mHz band -- I'll give Aroosh a shout and see what he can do for you.

Please, stand-by.

David,

[He Who Shall Not Be Named]

Went to Aroosh's site and found this:

Upcoming Products


SL-8 EURO Version (Spring 2008)

No crystals, no glitches!. A low cost synthesized ultra-light, ultra-small 8-channel receiver with advanced DSP signal detection, noise control and glitch suppression algorithms. This is a fully programmable Rx that will offer many advanced features will now be available on European frequencies 35/36/40/41 MHz.

It's not featured in his catalog though. I've sent him an e-mail asking about this Euro version of his SL-8. I'll get back to you the minute I hear something.

David,

[He Who Shall Not Be Named]

Bad news:

Just got an answer back from Aroosh. He says that Sombra Labs dropped production of the Euro version of the SL-8 owing to a near non-existant market for the product.

Sorry.

Here's what you do:

Take that nasty WFly receiver and mount it well forward of the ESC -- the new motor bulkhead leaves you about three inches of unused space between the ESC and the after face of the after ballast bulkhead -- this gives you enough distance (remember, RF noise and such diminishes as a square of the distance) between the receiver and motors (the big RF noise source) to give it a fighting chance of not being swamped by electrical chatter.

Keep me informed.

David,

[Bob K]

Thank you David. I saw that on their site, and that no one seemed to stock it.
OK, I am now in build mode !
Cheers
Bob

[He Who Shall Not Be Named]

Thank you David. I saw that on their site, and that no one seemed to stock it.
OK, I am now in build mode !
Cheers
Bob

Go get 'em, Tiger!