Calling all pushboat guys.
I recently ran a tug at another company that had a Dehart swing meter, and I want one on my tug.
The regular captain there said it came with the boat. He said you can’t buy them anymore. You can only rent them. Googling around I found Swing guard. I spoke with guy and they want $45 a month for rentals no sales.
I haven,t been able to reach anyone at Dehart yet.
What’s the deal with these things? Where can I buy one at reasonable cost?
I got a few google hits with “rate of turn indicator.”
There is an old Sperry unit on eBay for $500 plus shipping.
https://www.ebay.com/itm/Vintage-Sperry-Rate-of-Turn-Indicator-P-N-03956-1858105/201596538419?hash=item2ef0170e33:g:CgkAAMXQgwNSIlf3&vxp=mtr
These Simrad units run for $640
https://www.waveinn.com/nautical-fishing/simrad-is70-rot-indicator/560373/p?utm_source=google_products&utm_medium=merchant&id_producte=624251&country=us&gclid=EAIaIQobChMImNzbwrPj2QIVEqvsCh2jTgF0EAkYASABEgI4CfD_BwE&gclsrc=aw.ds
I see in the description that a swing meter is for rate of turn for inland vessels. Based on that, it’s the same thing as a modern rudder angle indicator in a way?
Or because it’s gyroscopic based, it’s a completely separate animal?
This is the model we had on the ship I was on. The Captain and mates thought highly of it.
https://www.ebay.com/i/142409945730?chn=ps
or was it this one…
https://www.ecrater.com/p/17517874/digital-gyro-repeater-lr40-of-scandinavian?gps=1&id=81021731659&gclid=EAIaIQobChMI957yhbXj2QIViuNkCh2n1A6BEAkYECABEgL93vD_BwE
It’s a completely different animal than a rudder indicator. it measures how fast your ship is turning, regardless of how much rudder you are using.
Don’t know what kind of equipment the tugs you’re working have, could be the information needed for RoT (rate of turn) is already available. Deep-sea I get RoT from the AIS (and the ECDIS of course) which I believe originates from the gyro.
Even if the data is available might not be worthwhile, the swing meter might be the only practical solution.
One tug i worked had a Rivertronics.
It did the job. The main unit sat in the galley on top of the refrigerator, with the display in the wheelhouse
Rivertronics is what we mostly use up on the Great Lakes. Compared to ROT given by ECDIS it is very sensitive and you can see the vessel starting to turn before the gyro moves or you can see anything out the window.
Is there any difference between a swingmeter and a Rate of Turn Indicator? See the ROT on a lot of foreign vessels, mostly tankers, but some bulkers too. Nice to have in fog…
Not really they do the same thing. Some have their own gyro in them, some work off the ships gyro or some other nmea source or ROT.
Is there any difference between a swingmeter and a Rate of Turn Indicator? See the ROT on a lot of foreign vessels, mostly tankers, but some bulkers too. Nice to have in fog…
Swingmeters are much more sensitive, and react much sooner than ROT indicators. Other than that, no
Most modern rate of turn indicators use a gyro sensor. In essence it is Vibration gyro sensor which senses angular velocity from the Coriolis force applied to a vibrating element. The picture shows the Cytron S-300 gyro sensor assembly which costs 15,61 dollar. Small price compared to a real spinning gyro!
The same type of sensor is used in video cameras to stabilize the movie against vibrations.
Guys, guys, guys! Silverbk, what you are looking for is a DeHart Swing Meter and they are most certainly still available. Their phone number is (901) 523-0945. They discontinued the model I think you’re talking about but their Sigma system replaces it. As a builder of towboats, I have also found that the Rivertronics system is a very good system. I’ve installed plenty of them and the boat captains like them a lot. Talk to Mike at Rivertronics. His number is (618)254-1910. Great guy. Very responsive to your requests.
Is there any truth to the rumor that you cannot buy these outright only lease or rent them?
Ok I had time to speak with all 3 companies I could find.
Swing Guard 2B is $45 A month lease only no sales.
DeHart sigma is $3875.00 FOB Memphis plus shipping and about $1.00 A foot for the interconnect cable.
Rivertronics is $4195.00 plus shipping comes with a 35 foot interconnect cable. Runs on 24v.
The second two companies offered outright sales, Swing Guard does leasing only and will not support “lost” or “stolen” units.
I wonder how much more sensitive a swing meter is then a standard rate-of-turn indicator?
There is a paragraph in “Shiphandling for the Mariner” about the ROT indicator,
Discussing how the helmsman can use it to aid steering
"As soon as swing is indicated hte helmsman use sufficient rudder to check that swing, often applying the rudder before any movement of the bow to the right or left can be detected by eye."
Very small changes can be seen by eye so that sounds very sensitive.
As far as I know there is no real difference between a swing meter and a rate of turn indicator, although maybe there is, read further on. It seems that the internet has no information on the subject, in any case I could not find it. The biggest supplier of ROTI’s in the Netherlands is Alphatron and their product Basicturn is labeled ‘Rate Of Turn/Swing Meter’. I telephoned with the tech in charge but he said that he is unaware of a product that is more sensitive than a Rate Of Turn Indicator and that the term Swing Meter is just an American name for a ROTI.
I learned from him that their instrument still uses a real spinning gyro as that has the greatest sensitivity compared to the solid state gyro sensor. Maybe that explains it, a Swing Meter has a real gyro and is more sensitive than a ROTI with a gyro sensor. Well, that is just a little theory without proof yet!
Tomorrow I will call another, also a rather big supplier for that kind of equipment and see what they have to say. Keep you informed.
Rate of Turn indicators are fairly normal on large ships, providing an output in degrees per minute, so that you can provide a fixed rate radius turn. Particularly useful in zero visibility pilotage conditions. Also on the cruise ships, excessive RoT above manoeuvring speed will result in the vessel heeling which is obviously a dangerous situation, so the helmsman are trained to be able to steer to RoT commands and the navigator or pilot can shed some of his workload to the helmsman.
For those people less inclined to purchase a ROT indicator you could count the amount of time taken to pass between degrees.
ROT on ships is universally expressed in Deg/minute
The mathematical equation would look something like this
ROT = 60 seconds / ? seconds per Degree
Example
10 Deg / 60 sec = 1 Deg / 6 sec
15 Deg / 60 sec = 1 Deg / 4 sec
20 Deg / 60 sec = 1 Deg / 3 sec
30 Deg / 60 sec = 1 Deg / 2 sec
