RCABS - How do they work?

[Guest]

Hello Al,
I've seen your

Hello Al,
I've seen your video and have now read your MSN page. It looks very promising indeed. I too have one of those blood pressure monitors and one my first thoughts when using it was "mmm could I use this in a sub?" But I expect most model submariners view the world around them, with a view to using things in their boats. Has anyone convert a Small world Models boat to using this system. (Asks because I'm after a Trafalgar)

[Guest]

Where is the Edit button?

Where is the Edit button? Sorry Art its not Al.

[Guest]

Hello,
John Darnell used a

Hello,
John Darnell used a similar system in his kits in the early 1980's. He used a steam engine driven by a motor to take air out of a bag and store it in either the pressure hull or a purpose built chamber. I remember it had two basic problems. At depth there was sometimes not enough air pressure to re-inflate the bag vs outside water pressure and his steam engine acting as a compressor sucked the batteries dry in less than 1/2 an hour. It looks like this system is a vast improvement. Does it suffer from depth/pressure problems? or are these new little pumps quite powerful?

I think Darnells system first originated in the '60's.

Most modellers who purchased his kits modified the system by replacing the USE steam pump with a modified tyre inflater compressor. The mod involved adding pipes to the compressor valves and replacing the juicy motor with a smaller variant.

The folk I've seen using this system, inflate the bags onshore. The Compressor sucks the air from these bags to dive, and stores the air in a small cylinder located in the free flood area of the boat.

To surface, a schraeder valve is operated by a servo and the compressed air relased back into the bouyancy bag.

This has the advantage that the compressor is only required to operate when you wish to dive.

Nick Burge refined this sytem further by incorporating a fixed tank and using the forward part of the WTC as an air reservoir.

This system was further developed by Brian Cornelius (Craycraft) and was used in Craycraft/OTW kits for some time.

Andy

[Guest]

I first saw his (Johns)

I first saw his (Johns) subs in Marine Modelling in the early 80's. I had no idea he was making subs earlier. I have an example of an even earlier type, which is a tin submarine toy from the 1930's that used a bladder to dive/surface. Although not really controllable in any other sense.
Pics here]http://www.akula971.com/Tinsubs.htm[/url]

[bigdave]

Jeff,
They were made from

Jeff,
They were made from buna-n. They are the only ones I could find from McMaster in the H type. The same ones Jim Butt uses. Dave.

[sam reichart]

I like RCABS, and remember

I like RCABS, and remember seeing it on Art's Alfa back about 5 or 6 years ago.

Just curious- how well can one "hover" their model using the RCABS systems?

Sam

[Guest]

Hovering the boat is difficult

Hovering the boat is difficult with any compressed air system in my experience.

However it is possible, but IMHO a piston tank system is better for very accurate ballast control.

Andy

[JWLaRue]

Sam,

Since there is no 'metering'

Sam,

Since there is no 'metering' capability, an RCABS system would be better than a gas system but not as good as an Engel piston system.

Depending on the speed/volume of the pump, the RCABS *could* yield control similar to a piston. My experience with both the OTW dive module (which, in effect provides the same level of control as RCABS) and the Engel piston is that hovering is possible but not as easily *repeatable*.

-Jeff

[sam reichart]

Sam,

Since there is no 'metering'

Sam,

Since there is no 'metering' capability, an RCABS system would be better than a gas system but not as good as an Engel piston system.

Depending on the speed/volume of the pump, the RCABS *could* yield control similar to a piston. My experience with both the OTW dive module (which, in effect provides the same level of control as RCABS) and the Engel piston is that hovering is possible but not as easily *repeatable*.

-Jeff

Jeff-
yeah, you read my mind...your hybrid system utilizing the Engel tank vs. an RCABS system in the OTW XXIII... I'm still considering both. You know me; the engineering aspect of the model is not my forte!

I'm still torn between the simplicity of the RCABS system, (along with the cost savings), versus the more finite control of the model using your piston hybrid (bearing in mind the higher cost...)

I would love to have a model that could actually hover, after having a bunch that dove and surfaced but didn't have that type of control. Closest that came to it was the first XXIII, I guess...

Sam

[Guest]

You could use RCABS, but

You could use RCABS, but instead of using an inflatable bladder, use a bellows/gator- the kind you find on the end of a car steering rack.


This could be inflated and retracted using a compressor, and an arm could be fixed to the end of the bellows to provide elecro mechanical feedback using something like Bruggens piston tank controller.

Food for thought?

Andy

[Guest]

I can dial in the

I can dial in the controls for my RCABS boats to hover, but not for very long. It seems like the slightest turbulence will send them down, and then I have to balance the air pump/release signals all over again to achieve neutral buoyancy. It might be a little easier with a Clippard valve instead of the servo actuated Schraeder (tire) valve, but still not as easy as a screw piston mechanism.
I trim my models to a very slightly negative buoyancy when the bladder is flat. That way, going deeper does not further compress the already flat badder.

[Guest]

You could fit a valve

You could fit a valve on the bottom of the ballast tank - known as a 'kingston' valve apparently.

This would prevent water pressure compressing the air inside the bag.

It would mean the addition of another channel and servo, which complicates things somewhat, but this does give an improvement in performance.

Andy