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Double ended rudders

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dragoncity:
Tony,
won't you have a problem with the last position of the 'tuned off' servos
rudder ? It will probably cause unusual handling situations :-)

I think you may need to 'autocenter' that servo ( somehow) before or after
turning off.

Cheers,
Brett

Tony Mattson:
There is certainly potential for very unusual handling if the switch-over occurs while the ferry is in motion. I think I will need a bit of discipline in how I go about the switching process.

The prototype had twin rudders that were separately manually engaged and disengaged by a deckhand at the end of each run, i.e. berthed at a wharf with passengers embarking or disembarking. Of course if the deckhand changed the rudders over during the run then the ferry would have suffered significant handling problems as you anticipate.

The disclipine in controlling the model will come in chosing to change directions/ends only when the model is at rest just like the prototype - and with Tx rudder joystick at neutral, and rudder servo likewise in response.

So then in order to make this a meaningful function I suppose now that I'll also need to construct two or three scale wharves or piers for the model to commute between!!!

As I said, it'd be way simpler if I just ran both rudders all the time! Of course if anyone has other ideas then all will be very, very gratefully received.

Cheers
Tony
Auckland, NZ

Derek Warner:
Hi Tony - I have been reading this subject with interest - are you going
to use action man proportional electronic controls for independent
wheels? - I ask this as my experiments with PS Decoy were a little out
of keeping - the proportional wheel controllers would be great for twin
screw models, but were very jerky in operation with Decoy & say 10
degrees rudder movement off neutral had her going near sideways in
circles & looked pretty silly - in the end I disconnected the servo to
rudder bell crank connection but that made little difference

I am still going to maintain the independent twin electric motors, but
coupled to one action man kit speed reducer & steam sound module etc

When I first looked at your Britannia snaps [high & dry] [eight months
ago?] I could just see & note the rudder size & thought that you would
maintain both rudders to get some steerage as they are not barn door
sizing - keep us posted - Derek

Tony Mattson:
Hi Derek, et al.,

I wasn't entirely satisfied with the electronic motor mixer
performance in PT Reliant. On applying forward power one motor kicks
into life almost immediately while the other starts only when the
throttle joystick is at half speed or more. Same in reverse but on
the opposite sides. Because of this my slow speed turns were pretty
much 'haywire'.

I suspect this relates to my motor installations.

Due to the limited space in the hull one motor operates in reverse to
the other when both paddles are going in the same direction. With my
limited understanding of electric motors I believe that this results
in a somewhat unbalanced output between the two motors especially at
start-up.

I suspect that the electronic speed controller was designed for
matched motors where both run in the same direction when power is
applied. Perfect for a twin screw model - extrapolating this to a
paddler, this would mean locating both motors so that they run the
same way when forward power is applied. i.e. output shafts from both
motors pointing towards the same side of the model.

I didn't have room for this in PT Reliant so have scrapped the motor
mixer approach and am currently using independent joysticks.

I really am betwixt and between on the drive system for Britannia: a
full-on commitment to reproduce the original would mean running both
paddles on a single shaft and relying on rudder(s) for steerage. But
then I'm faced with a much larger turning circle and a less
manoeuvrable model. So having both rudders permanently connected
would be useful, esp. as Britannia's were not that large.

Because there are no plans, my Britannia will really be a stand-off
scale version - so the super-scale approach of using a single shaft
drive train is not critical to the model and independent controls
would work fine.

So will I be able to locate both motors so that the output shafts
point to the same side of the model? The hull's not much wider than
Reliant, but it may be possible. If I can do this, then I'll try the
Action Motor Mixer again. If not then I'll revert to independent
joysticks for Britannia as well.

Unless of course I try to reproduce PJ's design for a wiper-board
mixer from his drawings in the file section.

So many options - so little ability!

Whatever happens I'll surely keep you posted.

Cheers
Tony
Auckland, NZ

Paulrjordan:
Hi Tony...I have to throw this at you as I always try to take a
pragmatic approach to these modeling challenges, so consider it for
what it's worth.

I believe there is considerable challenge in developing an electro
mechanical system to replicate the deck-hand lifting and dropping the
rudder locks when the vessel changes direction of travel.

Consider the following:

Are you actually going to build two docks to accommodate double ended
operation?

Is anybody going to actually see the rudder mechanisms working under
water?

Since "Britannia" is virtually identical at both ends, will anybody
be able to tell which way she is going or indeed to tell if if she's
going for'ard or astern? Consequently, does it really matter if she
has two rudders? She will look exactly the same going in both
directions anyway, so why not just concentrate on one direction and
lock the "for'ard" rudder permanently.

This same challenge would exist in a British excursion paddler
equipped with a bow rudder, and I have tried to figure this one out
too without much success. Switching between the two rudders is
easily done with micro switches acting as selectors between the two
servos, but developing an integrated locking/release system is quite
a different matter unless the servo has sufficient strength to auto
centre and hold the rudder in a central position against the opposing
force of water. It is quite possible that certain servos may well be
strong enough to self lock and this would avoid the requirement of a
mechanical locking/release system.

I believe the finished model of "Britannia" will be so spectacular on
the water anyway, she won't need any special rudder "effects" and I'm
honestly trying to save you from following what may well be the
proverbial "red herring". If on the other hand you thoroughly enjoy
the technical challenge of doing something I don't think has been
done before, then go right ahead!!! It's a fascinating topic anyway
and I look foward to hearing your further thoughts.

Best regards

PJ
Victoria, BC Canada

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