Swing meters wtf?

Our rivertronics units up on the lakes are extremely sensitive. You can watch the needle just start to move well before you can see a relative change out the window. Comes in really handy when we ride the bow down the lock entrance wall and want to keep a certain distance off the stern. Once you get to a heading you can just use very slight wheel to keep her steady.

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As promised earlier I talked to the second local supplier of ROTI’s which is also not familiar with the name ‘Swing Meter’. They have heard of it and think that it is just another name for the same instrument.

What is important, apart from the name, is that for the helmsman the ROTI is a very valuable instrument to make a proper turn while maintaining speed, using less fuel and arriving with a minimum of overshoot at the end of the turn. For a safe turn, it is necessary for a vessel to determine her wheel-over position or point, the execution point wherein the ship starts to turn and overcomes the inertia of the ship. If that value is unknown one ship length, sometimes 0.2 nautical mile, is used as an approximation.

The constant radius turn technique is based on the following formula:
(1 radian/60) * V/R where:
V= Ship’s speed over ground, in knots and,
​R= Radius of the turn in nautical miles.
Simplified: 0.96 * V/R

We have here a fleet, due to the extensive waterway system of a country in a delta area, of thousands of inland waterway ships. As from 1st of January 2016 the AIS is a compulsory navigational instrument for commercial inland waterway ships. However, only the inland waterway vessels who trade on the river Rhine are obliged since 2014 to connect the AIS and ROTI to the electronic chart display, the Inland-ECDIS.

If an inland waterway ship is equipped with an AIS system and a Rate Of Turn Indicator, then the latter, which has to be provided with an IEC 61162 interface, must be connected to the AIS to send the rate of turn to other vessels. This makes it easier for other vessels to interpret the manoeuvre of the ship.

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My current understanding is that ROTI and a swing meter is not exactly the same thing. Any display that indicates ROT is going to be a ROTI including the display on the ECDIS or on the steering stand.

A swing meter (as described on this thread) is a specific type of ROTI, it may obtain data from a separate unit independent from the main gyro and does not necessarily indicate degrees per unit time.

Deep-sea in my experience the conning officer controls ROT via helm commands. The rate can be kept within a small range by eye or feel.

Rate of Turn Indicator is the proper professional nautical term.

“Swing Meter” is Mississippi River boatman local vernacular.

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It could be true that there is something like a Swing Meter with a better angular sensitivity but they are hard to locate on the internet. As an example Alphatron’s Basicturn is advertised as Rate Of Turn / Swing Meter.

IMG_2479

The only ROT’s that are highly accurate and sensitive are those based on a ring laser as measuring instrument. They are proven to have more accuracy than traditional rotating mechanical gyroscopes. During any movement of the aircraft, or on other vehicle it is mounted on, the angular rate is measured by determining the frequency shift in the laser beams. The RLG provides digital output linear with angular rotation. It has high sensitivity and stability. The reaction time to respond to rotation rate is quick. The ring laser gyroscopes are insensitive to acceleration, which makes them very suitable for use in a F-16 jet fighter, Airbus etc. and are immune to environmental effects. Price-wise they are very expensive.and I expect not to be seen on vessels for quite some time.

Now I don’t think this is right, the ECDIS and steering stand displays don’t meet the definition of a ROTI, they would be 'other means"

This is from SOLAS:

a rate of turn indicator, or other means, to determine and display the rate of turn; and…

As described a swing meter doesn’t meet these requirements.

Here’s the requirements:

2 Operational standards

2.1 The ROTI should be capable of indicating rates of turn to starboard and to port of the ship to which it is fitted.

2.2 The ROTI may be self-contained; alternatively it may form part of, or derive information from, any other appropriate equipment.

2.3 Indication

2.3.1 The indication required should be provided by a centre-zero analogue type indicator (preferably circular). Where a circular scale indicator is used, the zero should be uppermost.

2.3.2 A turn of ship to port should be indicated on the left of the zero point and a starboard turn to the right of the zero point. If the actual rate of turn exceeds full scale deflection, this should be clearly indicated on the display.

2.3.3 In addition, an alphanumeric display may be provided. Positive indication of port and starboard should be provided on such displays.

2.3.4 The length of scale in either direction from zero should not be less than 120 mm. The sensitivity of the system should ensure that a change in the rate of turn of 1° per minute is represented by a distance of not less than 4 mm on its scale.

2.4 Range scales

2.4.1 A linear range scale of not less than ± 30° per minute should be provided. This scale should be marked in intervals of 1° per minute on both sides of zero. The scale should be marked with figures every 10° per minute. Every 10° mark should be significantly longer than the 5° mark which in turn should be significantly longer than the 1° mark. The marks and figures should preferable be red or a light colour on a dark background.

2.4.2 Additional linear range scales may be provided.

2.4.3 Damping of the ROTI should be provided with a time constant which may be varied during operation in the range zero to at least 10 seconds.

2.5 Accuracy

2.5.1 The indicated rate of turn should not deviate from the actual rate of turn of the ship by more than 0.5 degrees per minute plus 5 per cent of the indicated rate of turn of the ship. These values include the influence of earth rate.

2.5.2 Periodic rolling motion of the ship with an amplitude of ± 5° and period of up to 25 seconds and periodic pitching motion with an amplitude of ± 1° and period of up to 20 seconds should not change the mean value of the indicated rate of turn by more than 0.5° per minute.

2.5.3 The ROTI should meet these accuracy requirements at all ship speeds up to 10 knots.

No ROTI in the wheelhouse. ROT can be called up on the screen of the ECDIS via the menu. No silhouettes that I’m aware of, seen it on the pilots laptops.

Even if I had it I’ve never gotten in the habit so not much use for me but I think it would be useful for mates, especially new one. I try to train them to conn from near the center line where they can see the compass. If I was to refer to the ROT on the ECDIS they’d plant themselves there for sure.

I have a swing guard installed on my tug now and also run another boat with a Dehart. Both units have their own gyro in them
.
The swing meter tells me if I’m going straight or turning left or right. It’s not always apparent visually. It allows me to correct sooner, keeping me straighter and consuming less fuel.

Doing certain maneuvers requires me to “swing” the boat and tow around, usually one way then the other, on a single screw tug swing is everything. I can’t “walk” the boat like a twin screw can. The meter tells me if i’m moving and if so which direction. It’s not always apparent by looking out the window.

Years ago when I was a helmsman on a Coast Guard cutter we could listen for the clicks on the gyro repeater. I haven’t been on a boat with audible clicks in a few years. The tug I’m on now uses a satellite compass.

I have also found a swing meter invaluable when there is no visibility by either fog or darkness. It allows me to do a controlled change of course, rather than letting the boat swing quickly and then correcting.

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Me neither and I miss that feature on the old gyro repeaters. Some of the pilots I get that still use Raven electronics can set an audible click on their pilot unit. It brings me back

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Good point, my brain has been recalibrated for a house forward.

Yes, that clicking was very helpful, It wasn’t something you had to remember to check, it worked almost like an audible alarm if the was clicking too fast or too slow.

Here is old beat up Swing Guard 2B It has an electric motor on the back the spins a disk with magnets mounted on its circumference. Through the theory of gyroscopic procession, when you turn the ship the disk deflects from its axis, when that happens the magnets induce current into coils and it reads on the needle. The patent is expired and it looks easy enough to knock off.

This is DeHart. Works on similar principal except it contains a much more elaborate gyro. I have not had it apart to reverse engineer it yet. I only unboxed it for testing before she gets mounted in my wheelhouse.

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Posting to this old thread because the information contained has changed. This thread comes up in a google search, so the updates are for the benefit of those searching for swing meters.

DeHart Marine Electronics has gone out of business. Jimmy DeHart got old and his wife just closed it down.

The green DeHart Swing meters (which are the best) are obsolete and no longer supported. They are slowly disappearing off of boats. It was actually manufactured by Radio Zeeland in Holland and imported and sold exclusively through DeHart. The Dehart Sigma 300 is also no longer supported. Radio Zeeland now offers the Titan 300.

You can buy them through Radio Zeeland dealers in the US:

DBS Electronics Inc.
6869 Rainbow Lane,
Port Arthur TX 77642

Contact: Mary Burdine / Claude Roberts
PH# 409.962.8747
E-Mail: mary@dbselectronics.com
E-Mail: claude@dbselectronics.com

GMENI Marine Electronics & Supply
5815 Benton Road,
Paducah, Kentucky 42003
Contact: Donnie Calvin
PH# 270.898.6018
E-Mail: d.calvin@gmeniinc.com

Expect to pay about $4700 and wait indefinitely, apparently Kirby bought them all up.

Rivertronics and Swing Guard info remains the same.

There is one other option out there called Alphatron Basic Turn. If have no info, no have I ever seen one in the wild.

I am in New York and these are not universal up here like on the rivers. I think this is a great way to comply with Subchapter M and SIRE vetting that is actually useful. Unlike a magnetic compass, which isn’t worth a crap on a steel tug with a barge alongside.

Personally I would not take a unit up to Albany in Spring without one.

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Dutch inland waterway tanker with Titan 300 rate of turn indicator integrated into the navigation console.

Just noticed my offspring also has a analogue rate of turn indicator in the upper console, admittedly a bit off from the immediate field of view of the helmsman:

Most ships I’ve been on have only had digital displays which presumably get their input from ECDIS.

That doesn’t go well with our analog brain and I don’t know what the regulations have to say about this. They are subject to type approval. They are in use here already since the late seventies. With all the bends in the rivers it is an ideal instrument to accurately and effortless navigate these bends, especially for those long train of barges.

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I admit I can be mistaken here. I guess it may also be possible to call up an analogue ROTI to one of the digital displays.

No, you are not mistaken. I found that in 1995 a digital ROT indicator was sold by Radio Holland to a client. Furthermore the Mk8 ROT indicator was already sold in 1965 usually together with a Kelvin Hughes 17, for the first time fully transistorised, river radar.

The old gyros that clicked were great for judging swing, too. The swing meters (I have used both the Dehart and Rivertronics models) can be a great aid, particularly in low visibility where you don’t have your visual marks to help judge your turn.

IIRC, the Rivertronics unit could be adjusted in sensitivity and woe to the mate who tweaked it after the Old Man set it to his liking at spring fit out.

So was the helmsman coughing to cover up the clicking gyro.

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On Dutch ships, to keep up their helmsman’s skills, AB’s had to take turns at the helm for a couple of hours, mostly during the evening and night. Especially during the dark hours they sometimes dreamed away and the ship wandered off course. We could identify that by the increasing frequency of the gyro ticks and startled him by giving a shout: ‘Hey, wake up!’