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More questions - Need advice

R/C Submarine modelers

Postby Ahab » Tue Sep 16, 2003 3:42 pm

All the replies I've gotten have been really helpful. Including the replies on the posting I have in the General catagory. I do, of course, have a few more questions.
1. What type of radio should I get? I've been told the Robbe F14 is good because it is expandable. Or is there one out there that's better?
2. I'm playing with the idea of making my own piston ballast system. Have a plunger compress the air in the tank, which allows water to enter. Retract Piston, to allow air to expand expelling water.
3. What kind of electronics are involved. I know about engines and cirvo's. But I'm a complete beginner when it comes to transmitters/recievers and anything else that the sub might need. Including automatic leveler. Can anyone steer me to a good book?

Thanks in advance.
Mark
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Postby Ramius-II » Tue Sep 16, 2003 8:39 pm

Hi Mark:
Personally I think the F-14 is the most versitile. If you go to the Ships N' Things website: http://www.shipsnthings.com/
, you can see all the possible options. From my experience with some radios, adding simple on/off switches can be a challenge. Most are modified aircraft types with internal computers to program, etc. ??? If later you need more channels (like an 8th channel) Al can provide this for you if you send him your receiver or just order it with 8 channels to start with. Hope this helps in your decision.

Best, Ed
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Postby Sub culture » Wed Sep 17, 2003 8:25 am

Hi,

The F14 is a nice outfit, with lots of bells and whistles, which are handy if you want lots of auxillliary functions on your sub, boat etc.. Other than that, it's a bit expensive, and somewhat over specified IMHO.

I have an FC16 which is similiar to the F14, but has computerised memories and mixers- these are genuinely useful for all models, especially so for subs, but unless you can pick one up cheaply (as I did) then once again a little over the top.

What you need to look for is a good four channel set on surface frequency. If you want some auxilliary functions, budget for a six channel set.

You really don't need anything more, especially at the beginners stage of the hobby, and the money would be better spent on a leveller and ballast control electronics, which really will make a difference to the running of your sub!

Airtronics, Futaba (Robbe) and Hi-tec all make very good outfits.

Your ideas on Piston tanks are nothing new, and you will find a good design/drawing in the Picture gallery of this site, which was submitted by Lothar Menz.

The piston tank system is possibly the most accurate way of trimming ballast in a model sub, but it does have some drawbacks which need to be considered.

The system needs plenty of power to submerge and surface.

The seals can leak and require careful maintenance and greasing to avoid this.

The layout of the boat needs to accomodate the tank. If you have a single tank and mount it longitudinaly, you will need to make a mechanism to shift a counter balance (the drive battery usually), or trim the boat in a peculiar fashion to allow for the shift in the C.O.G.

Twin piston tanks, one at each end of the boat, can be used to overcome the above issue, but these can be quite tricky to balance and also make sighting of the motor and propshaft/linkages etc. rather awkward.

Control systems for Piston ballast tanks are available commercially from both Norbert Bruggen and Engel. These either use relays in a bang-bang fashion (no proportional control) or use a servo feedback system for the ultimate in ballast control. Not surprisingly the latter is the most expensive route.

You may want to consider purchasing a copy of Norbert Bruggens book "Model Submarine Technology".

Be warned it's not for the faint hearted, it does get quite technical in places, however I have found it a valuable reference in this hobby. You will find most of your answers in that book.

A whole chapter of the book is devoted to piston tank design, and a circuit is presented for a DIY servo controlled ballast tank unit (never built this, so can't vouch for it's reliability).
I do know other folk who have attempted to build the leveller designs, also featured in the book, and they required modification before they would function correctly, so beware.

You can purchase the book at Amazon, or direct from Traplet publications

http://www.traplet.com

A leveller is needed on any model sub generally travelling above a snails pace.

Some boats cope better than others, I ran a Seehund for about four years without a leveller.

Keeping it at periscope depth for more than a few feet was tricky at slow speed, and impossible at any higher speed.

There are some brilliant levellers on the market now, and they're getting cheaper all the time.

I use one of Solid-State's designs in my Seehund, which is precise, tiny requires no calibration and is very affordable.

http://www.modelcontrollers.com

I'd also recommend Subtechs leveller which I believe uses the same acclerometer chip as the Solid State leveller (Analog devices ADXL202) . Engel also supplies a good leveller based on that chip.

A basic list on the electronics needed in a model sub-

3-4 channel radio set with two or three servos and receiver (3 channel minimum for a dynamic diver, 4 for a static diver)

ESC (Electronic speed control) preferably with BEC (Battery eliminator circuit) you'll need a controller capable of at least 10A continuous rating in any decent sized model.

Failsafe- ESSENTIAL. This will perform a set function if the radio signal is lost i.e. blow all ballast! Some ballast controllers come with an inbuilt failsafe.

Ballast tank controller (If using a piston tank). Also some compressed air systems use a dive manager for control of the compresser and water level.

Leveller. Not essential, but a very nice luxury. You can always add one later when funds allow.

Other components needed depend on whether you are purchasing a Kit, or going the DIY route, or somewhere in between!

For motive power, I seriously suggest visiting your local scrap yard and taking a peek at the electric motors you will find in the heater systems of most cars.

The vast majority make excellent motors for medium to large craft, and are far better built, more efficient than your average Speed 500 (etc.)

They deliver bags of torque at low revs (perfect for marine applications) and can be picked up for a pound or two (absolute bargain).

Cheers

Andy




Edited By Sub culture on 1063801957
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