Topic: Bob's H.M.S. Polyphemus (Read 263694 times)

derekwarner · « **Reply #250 on:** March 01, 2013, 11:30:12 pm »

Sorry Bob......in OZ we have different translations for different words

Technical would in this case apply to motors & pumps & valves & RC linkages or any thing nautical but normal

...however using abbreviations or words like RC Control is considered akin to the supernatural like ....... Black Magic......

I also enjoyed the posting by raflaunches................. although I did not understand that the reported increase of 1480 ihp [5520 to 7000] = a 27% increase in power, however this translated to produce an increase of just 0.15 knot [17.85 to 18] which is only an approx 2 1/2 % increase ???????????????................Derek

raflaunches · « **Reply #251 on:** March 02, 2013, 12:01:35 am »

You're not the only one confused by this Derek!
I copied word for word in the book and couldn't quite understand the difference either. The only other thing I have seen similar to this is the speed references regarding the Queen Elizabeth class Battleship HMS Warspite after her re-construction in the 1930s. It stated that she could achieve 23knots at normal speeds under normal circumstances but at forced draught she could achieve 24.75knots at overload speed which seemed to me as weird because I assumed that an over load speed would increase the speed dramatically not just by 1.75knots. Perhaps someone else could explain how this works because I have no idea that pumping that much extra power would only increase the speed by such as small percentage!

derekwarner · « **Reply #252 on:** March 02, 2013, 01:35:29 am »

Nick B...there is such a thing as maximum hull speed design & irrespective of the extra power provided is of little increase in resultant speed
I sort of understand this

but the % as shown do not answer my quandary either.....
The only Naval Architect I am aware of as a Mayhem member is XION [sorryfor the incorrect spelling] ......a French ex Naval Officer possibly could shed some light here.........Derek

Beagle1831 · « **Reply #253 on:** March 02, 2013, 12:50:31 pm »

Hi Bob
Could you use one of the action 'servo morph' thingys to increase the sweep angle of your servo to operate your valve lever?
Very much enjoying this build!
James

Arrow5 · « **Reply #254 on:** March 02, 2013, 01:06:10 pm »

Xtian, is Christian`s name on Mayhem.

Subculture · « **Reply #255 on:** March 02, 2013, 01:18:08 pm »

To get 90 degrees of motion from 30 degrees of servo movement you just want a three to one lever e.g. 45mm larm on the servo, 15mm arm on the valve

Bob K · « **Reply #256 on:** March 03, 2013, 10:34:24 am »

My technical head-scratcher:- Trying to explain the problem is not easy. If it were just translating the full swing of the servo arm into a full quarter turn of the valve handle then it would just be arranging arm lengths to achieve the desired movement.

However, the valve handle needs to be operated by just the full left to neutral position portion of the servo arm movement, without being pulled further when the servo arm moves from neutral to full right.

It seems like I may need a cam plate, sprung bell crank, or something like that. The diagram below shows how just linkage arms will not work.

It could end up as another creative solution, like my bow rudders mechanism.
Bagpuss Hat mode commences

Subculture · « **Reply #257 on:** March 03, 2013, 11:00:53 am »

I see. Perhaps the valve could be operated from a cam on the servo instead of a crank, and the valve returns via a sprung loaded plunger- e.g. the way poppet valve on a four stroke engine works. it would require a bit of expermentation with spring tension to ensure the valve fully returns each time. If you used tyre valves, which I think I originally suggested, this is already done for you.

Another way is electronic. A microcontroller between the servo and receiver would throw the servo when the stick is moved one way, to actuate the valve. When the stick is thrown the other way, the servo is kept in it's closed position, and a transistor or relay is operated to switch on the pump.

Shipmate60 · « **Reply #258 on:** March 03, 2013, 11:33:34 am »

2 servos on a "Y" Lead operating seperately?

Bob

Subculture · « **Reply #259 on:** March 03, 2013, 11:56:56 am »

Don't see how that will solve the problem Bob. Two servos off separate channels would work fine, not very elegant, but dead simple, if you have the channels to spare.

dreadnought72 · « **Reply #260 on:** March 03, 2013, 01:03:26 pm »

Quote from: Bob K on March 03, 2013, 10:34:24 am

...sprung bell crank, or something like that.

I agree with subculture's mechanical method.

A spring strong enough to drive the air valve to the closed position.

A 180 degree motion of a servo arm.

"max right" the servo arm operates the pump switch.

"middle" the servo arm is just touching the valve in the "closed" position.

"max left" the servo arm has driven the valve (against the work of the spring) to the "open" position.

Going the other way, the spring moves the valve back.

Andy

essex2visuvesi · « **Reply #261 on:** March 03, 2013, 01:23:29 pm »

what about using a solenoid type air valve?
http://www.ebay.co.uk/itm/RC-Submarine-MINI-Solenoid-valve-L-DC4-8v-24v-/281051675420?pt=US_Radio_Control_Control_Line&hash=item416ffc3b1c

would be a lot neater

Bob K · « **Reply #262 on:** March 03, 2013, 01:49:46 pm »

Interesting suggestions and good food for thought. Thanks.

Not sure if the servo can 'turn' the valve plus overcome spring tension too, but I can try it.

I do have 6 channels on my F14, including a slider plus a 3 position switch, so using 2 channels would indeed be simpler.

2 servos on a Y lead would break it into two 'easier' seperate problems, but would still need to overcome cancelling out the Neutral to RH arm swing.

I will check out that solenoid link, might be large but would come down to just two microswitches.

Plenty of ideas to be working on. Many thanks

grendel · « **Reply #263 on:** March 03, 2013, 06:02:37 pm »

what about something like this instead of the servo - http://www.dimensionengineering.com/products/picoswitch, plugs in like a servo but is a direct on off switch...
Grendel

grendel · « **Reply #264 on:** March 03, 2013, 06:05:57 pm »

whole bunch of similar stuff here, one might even do both functions.
http://www.technobotsonline.com/interfaces/radio-controlled-relays.html
Grendel

Bob K · « **Reply #265 on:** March 08, 2013, 10:17:34 pm »

A couple of setbacks, but some good progress as well.

Mastic

Still having problems with the white mastic sealant, springing leaks even after three thick layers. Now using fibreglass to line compartments.

Change of Tack

My ballast mass calculations went out the window after it turns out the new “24VDC” charger will not charge 24VDC batteries after all.
A bit miffed, I thought I had it all sussed out at last.

So, out go the three 12VDC battery packs, one was for the air pump and two in series for the mister, being replaced by a single large12VDC SC NimH pack. This saves 80 gm but now I have to squeeze in a 300 gm 12 to 24V DC converter. No choice but to fit it on top of the 6V SLA.

DC / DC Converter

The changes also forced me to move equipment between compartments, largely negating my trim trials.
The new 5 Ah pack just shoehorns in alongside the air pump and Rx, with neoprene foam sheet between.

12V battery, pump and Rx

Even more equipment being fitted.

‘Dive’ Controls

Pneumatics plumbing installed. Flexible 4 mm I/D silicone tubing. Brass tube stubs epoxied through bulkheads. Aquarium T pieces opened out for max air flow. Aquarium sealant around joints. Intake and vent are via the funnel outer tube.

After a day playing with a large box of springs and my quarter turn air valve I opted instead for a slightly larger version of the solenoid air valve suggested. A servo cam operates two micro-switches.

servo cam assembly

RH stick down to vent air from the two ballast tanks. RH stick up to pump air in.
Not quite a submarine (with any luck).

Reballasting

With everything fitted, bar the P64 sound system, it was back to the bathroom for trim testing. Surprisingly the changes still had her floating correctly and stable. In fact a little more ballast will eventually be required both fore and aft to achieve vented deep waterline. Bank coin bags are handy, one can hold up to three quarters of a Kilo of lead shot.

derekwarner · « **Reply #266 on:** March 09, 2013, 12:03:25 am »

Bob....I have never see so much Red & Black spaghetti

...keep up the good work

..........Derek

Bob K · « **Reply #267 on:** March 09, 2013, 12:16:53 pm »

Derek: I was considering some scale replica Bolognese sauce, but couldn't find a home workshop DNA tester.

What makes this look complicated is having external controls and the ability to charge in situ. Avoids having to frequently dismantle watertight panels both at home and pond-side.

Only bit I am worried about is that although the solenoid valve has 4 mm OD outlets the holes were under 2 mm. I might have to open those out or it could take ages to vent two and a half litres of air.
I had considered another pump, but that could end up spraying water from the funnel when the tanks become full.

Subculture · « **Reply #268 on:** March 09, 2013, 12:54:19 pm »

You could fit two working in parallel. Or use the tyre valve like I originally suggested- cheap, easily replaced and plenty of area.

Bob K · « **Reply #269 on:** March 09, 2013, 01:23:33 pm »

Subculture: Two in parallel would indeed double airflow. I will see how it goes.

I really did like your idea of using a tyre valve, but what I could not work out is that if it was operated by a cam etc then it sounds like it would vent into the volume where the valve/cam was fitted. Apologies, maybe I'm not quite seeing what you mean, but when the tanks become full I am visualising water coming through next?

Subculture · « **Reply #270 on:** March 09, 2013, 03:29:42 pm »

The valve would be fitted on top of the lid at a 90 degrees- right angle. A cam also mounted outside run through the lid into the watertight enclsore to connect with the servo.

Bob K · « **Reply #271 on:** March 21, 2013, 02:31:20 pm »

All up weight is now 8.3 kg ( 18.3 lb ). Final mass calculated for around 20 lb, so allow 2 lb max for deck and the fairly minimal superstructure. It should be within limits.
Without ballast tanks an extra 2.5 kg would be needed.

Air solenoid works OK. A little slow to vent tanks, but acceptable.
Air pump superb. After just a short time tanks blown, then bubbles from slots under hull. Raises waterline approx 20 mm.
Yet another leak. More delays whilst stripping and fibreglassing another compartment.

Batten Down The Hatches

With ballasting having gone well it was time to start fitting the six waterproof hatches. Strips of s/a MIL grade expanded neoprene were fitted to the under deck, trimmed to suit the hatch profiles, and spotted through with a fine bradawl for the stainless countersunk screws.
At least with the hatches on the interior looks better.

After hatch

Sound System

The last item of electrics to be fitted, a P64 ‘micro’ multi cylinder steam sound unit.
A bit of lateral thinking here. I am using a 20 mm section from a 65 dia down pipe connector to mount the speaker under the motors hatch. Clips fasten the speaker, with an RTV seal around the speaker beading.

A 40 mm tube passes through the hatch, to go up inside the aft superstructure. The drain pipe connector thus forms a tubular ‘sound box’, with the opening about 80 mm above the waterline. Even if water were to broach into this assembly it can only get as far as the speaker cone.

Sound box, underside

The aim is for the engine sound to be audible when close to, not from 3 m away which would be unrealistic.

Funnel

Another 40 mm tube passes through the mister hatch, concentric with the mister exhaust tube. The inner tube emits ‘smoke’ whilst the space between the tubes draws in air. I still need to separate air inlet and steam exhaust to prevent recirculation.

Funnel

essex2visuvesi · « **Reply #272 on:** March 21, 2013, 03:03:34 pm »

I hope you are bringing this to wicksted!

looks great

Bob K · « **Reply #273 on:** March 23, 2013, 01:23:47 pm »

Quote from: essex2visuvesi on March 21, 2013, 03:03:34 pm

I hope you are bringing this to wicksted!
looks great

Wicksteed may be possible. Albeit in a rather unfinished state.

Sound System

Full marks to ACTion, their little P64 may not be as versatile as their Noisy Thing but does what it says on the tin well. A very compact unit. Set to minimum volume, maximum rate.

Control Panel

Hopefully no longer looking like a ‘Gerry Anderson’ creation. Fitted, and with soft rubber bungs protecting the various charging connectors. Simple two switch controls, one for the main 5V and the other for the 12 and 24V systems. Four LED status indicators. Quite a bit of wiring involved.

Two brass strips locate the panel against the seating beads, with a little aquarium sealant around the edges. Front strip wedges under hatch edge, rear strip screwed down. Being a sloping panel the aim is for water to run off it.

Control Panel

Bow compartment is my favourite. Picture below shows forward steering gear and ballast controls

.Bow Compartment

Shot along Polyphemus’ under decks. Reminds me of the torpedo systems I used to design PCB’s for a long time ago.

Under decks

Next: Hull preparation, including further detailing, ready for spraying.
Then comes construction of the removable main decks.

( Sorry, the 'new' Photobucket is a disater IMO, randomly turning images through 90 degrees on uploading!
Even after editing back, shows correct in Photobucket but the link spins it back again )

tghsmith · « **Reply #274 on:** March 23, 2013, 02:51:32 pm »

what are the plans for hull colors, because of some recent research I've done have found that many ships of this vintage had green anti-fouling paint on the underwater body, most of the colorized prints of the period show red, thinking that the printers didn't want to make another plate for the green, red was already present in flags. I resprayed my VESUVIUS this week and think my cruiser Brooklyn will get the same. keep working on the strange stuff..

News:

Author Topic: Bob's H.M.S. Polyphemus (Read 263694 times)