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Trireme "Olympias" by Richard Braithwaite


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Continuing to add canopy sections. On the full size ship the sections were kept separate so as to minimise stress in the lightly built canopy as the ship flexed in a seaway. On the model I have left the outer rail continous so that alighment is maintained.

44622984_P3270360small.thumb.jpg.b66ed5ba8767d2a9549656430f0af2dd.jpg

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Richard, what a wonderful model!  The planking is superb! I have contemplated in my wildest dreams making an RC galley. There is a picture of a large model "Liburnian" galley in Vaughan Williams' "Introduction to RC Scale Sailing Models". They don't go into the rowing mechanism though.

 

I actually went through the exercise of designing a mechanical drive to provide an oval motion. It was quite complex since you want the oars synchronized on both sides when rowing forward or backward, yet able to be reversed on one side for rapid turns. You either need mechanical reversing mechanisms or a way to synchronize two separate motors (I picture microswitches with momentary contacts which are pressed by the oar beams at the end of their stroke, generating pulse streams which could be put into the phase detector of a PLL whose filter output controls the speed of one motor to exactly match the other; doable but unwieldy because the PLL would have to be incredibly slow with such infrequent phase updates from the uswitches). Then I saw somewhere or other a different idea:

 

Have four fairly high torque servos. The oar drive beam on each side is driven by two servos; one to provide the back-and-forth motion, the other to provide up-down motion. And this is the clever part ----> you plug an Arduino board into your RC RX to read your "throttle" and "rudder" channel PWM streams, and program the Arduino to provide four PWM streams for the four servos, with each oscillating back and forth to provide repetitive oar strokes. So for example, if you push your "throttle" stick to "full ahead" the oar drive beams on each side move quickly, in unison; if you move the rudder right you can have the Arduino slow the right-side beam down, or stop it, or even reverse it given a sharp rudder stick position.  It's all controlled by the program you write which can be in BASIC to keep things simple. You can design the PWM streams to the "stroke" and "elevation" servos to give elliptical motion or any other you care to experiment with. Arduinos are available with multiple PWM generators (where you simply enter the period and duty cycle). No electric motors, no drive belts etc.

 

LATER EDIT: I read up a bit on this topic as I am seriously considering making an RC galley next. It's actually PIC microcontrollers for which there is an available BASIC compiler. Arduinos employ "arduino" language which is a sort of "C" coding. I know zero about "C" but the Arduino commands look pretty simple; for example once you declare an internal timer is to output a PWM stream and set up the clock to get a 50 Hz repetition rate, a simple write of an integer value into a register sets the PWM output's duty cycle and hence servo position. All one needs to do is to write gradually increasing or decreasing integer values at regular time intervals and the servo arm sweeps accordingly. The Arduino "Nano" board sports up to six PWM outputs and several analog inputs to an internal Analog-to-Digital converter which could be used to read the DC value of the throttle and rudder outputs from the RC receiver, suitably low-pass filtered by an external R-C circuit you provide.

 

From my brief reading, getting started with an Arduino is easier than with a PIC; just my novice opinion. The Arduino Nano measures 18 x 45 mm, draws 19 mA, costs less than $25, and is hooked up to your PC via a mini USB to download programs you write using the user friendly and open-source Arduino IDE (integrated development environment).

 

It's still in the back of my mind for when I finish my current static model, but I also would really like to make an RC square rigger. Around here a square rigger would draw a lot of interest, but a galley would be unique I am sure.

 

I'm interested in how you joined the oars to the drive beam. I wondered how to have them attached, able to rotate at the joint during the stroke, while being unable to spin on their axis and throw the blades off vertical. At one point I pictured U-joints as used in RC electric motor boat prop shafts but it would cost a fortune to buy multitudes of them. Can't quite make it all out in your video.

 

I will follow your log with great interest. Thanks.

Edited by Ian_Grant
added some arduino information
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Ian, somebody's actually done it on MSW - see https://modelshipworld.com/topic/6207-greek-bireme-by-bensid54-radio-finished/page/16/

 

I think the rowing action on this one is particularly good. I don't know how it compares with what you had in mind, but Bensid explains his mechanism in some detail, and you might find this of use. (All W-A-A-A-Y over my head, I'm afraid).

 

Steven

 

Edited by Louie da fly
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Steven, thanks for pointing me to this build log. What a great model! I was greatly interested in his linkage design at the oar looms and the racetrack operation.

 

LATER EDIT: the following paragraph was augmented.

 

A large part of the complexity of my all-mechanical pseudo-design (I priced it at about $300 worth of parts from servo city!!) was driving both sides from a single motor so the oars on the two sides would be perfectly in sync when rowing straight, yet allowing for moving in opposite directions when turning. Bensid remarks several times in his videos that he has trouble "driving" his galley and I think it stems chiefly from having two motors drive the two sides with no means of having them run at exactly the same RPM, and even that does not guarantee the oar beams would be in sync as well. Very difficult to achieve with a purely mechanical solution.

 

It was shortly after that I read (somewhere?) about the Arduino/servo system. The two sides can be kept perfectly in sync because the Arduino is sourcing all the servo PWM streams. Again, and this is huge, there is no need for any racetrack or other way to shape the stroke because servo interaction defines it. I did not go to the lengths of sketching a possible mechanism but after watching these videos I can see maybe needing two servos on each side for the up/down motion; one at each end of the beam and plugged into the same Arduino output channel with a Y-harness, filling the function of the drive-belted sprockets. Still the same Arduino requirements: read two PWM streams and generate four.

 

I should add that as some people have mentioned, a drumbeat would be cool. Well an Arduino could also be programmed to automagically drive a speaker with a sound burst once per oar stroke.

 

It is to dream....

Edited by Ian_Grant
added thought of speaker drum sound
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Not drumbeats - that's a Hollywood stereotype. Apparently low-pitched notes get lost among all the noise of rowing the vessel - what they used to give the time was flutes - this is a Byzantine representation, but as far as I'm aware the ancients used flutes as well.

 

image.thumb.png.29e7a7ff9aebe5e45e5c4c0940191549.png

 

Steven

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21 hours ago, Louie da fly said:

Not drumbeats - that's a Hollywood stereotype. Apparently low-pitched notes get lost among all the noise of rowing the vessel - what they used to give the time was flutes - this is a Byzantine representation, but as far as I'm aware the ancients used flutes as well.

 

image.thumb.png.29e7a7ff9aebe5e45e5c4c0940191549.png

 

Steven

A flute would be used for keeping the timing of the oar strokes for the same reason whistles are used on life preservers today.  The high pitched note would be heard over the roar of the waves much easier than a shout or a low frequency drumbeat.  

Edited by DARIVS ARCHITECTVS
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16 hours ago, DARIVS ARCHITECTVS said:

The high pitched note would be hear over the roar of the waves much easier than a shout or a low frequency drumbeat.  

 

And over the low-pitched sounds of the oars grinding against the tholes, the creaking of the ship itself etc. According to the video of the Olympias sea-trials, they had hoped to try out various means of setting the time (presumably from contemporary records) but ran out of time and settled for the coach speaking through a microphone and a series of loudpeakers throughout the vessel.

 

Steven 

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Posted (edited)

Continuing with planking the canopy....

The cutting tools from my Unimat Lathe make convenient weights for holding down the planks while the epoxy dries on the current section. The gap between planks across the sliding joints is kept consistent with the spacing jig as shown.

The fastenings on the last section have still to be trimmed and sanded down (which is why they look a little conspicuous).

 

P7050220a-MSW.thumb.jpg.ace9a96eb8702e4040bf8c5ec54eb456.jpg

Edited by Richard Braithwaite
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Had a go at go at focus stacking to get full depth of filed down the gangway. There are some artifacts and out of focus areas. Could probably do better selecting and stacking the images in Photoshop rather than letting the camera do it automatically...

 

P7060269-MSW.thumb.jpg.f44ca84032148fdb9121a7dd26f822e7.jpg

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Posted (edited)
On 7/7/2021 at 7:10 AM, mtaylor said:

Now that's a photo we don't see often in this era.   Gives a sense of being inside and not having any idea where the ship is going.

 

From the Olympias sea trials 1990. See also the video of the sea trials earlier in this thread.

 

oarsmen Olympias 1.jpg

 

1868778215_oarsmenOlympias5.jpg.1ce7323cca315415af8cb09cb441c686.jpg

 

1192816393_oarsmenOlympias8.jpg.ba92145dea7cc2739772666bc8cb27e8.jpg   996743825_oarsmenOlympias10.jpg.c12cd2267956cdfb086eb23ed3ce2cd7.jpg

 

Steven

 

 

 

Edited by Louie da fly
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Hi everyone, is there anyway that you know how to find the plans that Richard had posted sections of, with such a high resolution. I would like a collection of these plans at high res as I am planning a miniature model of around 1/28 or 1/192 scale of the Olympias.

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2 hours ago, Johnny.D said:

Hi everyone, is there anyway that you know how to find the plans that Richard had posted sections of, with such a high resolution. I would like a collection of these plans at high res as I am planning a miniature model of around 1/28 or 1/192 scale of the Olympias.

Richard posted just recently.  Hopefully he'll be back.   You might try sending him a PM.

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Plans were available from the Trireme Trust organization which has been wound down now that Olympias is out of the water etc.  When I tried to get plans last winter, I got a reply that they were looking to hire a new librarian and to try again in the spring. I never did, but you could try them again now.

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On 10/1/2021 at 12:27 PM, Ian_Grant said:

Plans were available from the Trireme Trust organization which has been wound down now that Olympias is out of the water etc.  When I tried to get plans last winter, I got a reply that they were looking to hire a new librarian and to try again in the spring. I never did, but you could try them again now.

Oh really, I got that same automated reply and I contacted them only a few days ago.

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I took down the photos of my model on this thread and have posted them up in a gallery on my profile. I have some more detailed and up close shots of my project currently for my highschool woodwork major project.

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Hi everyone, I've been doing some researching and digging around for the availability of the Olympias plans as well as the availability of the Trureme Trust. I had contacted Boris Rankov which is highly involved in the Olympias and this is what he had to say...

 

"I’m afraid the The Trireme Trust was wound up in 2019 and no longer exists. Together with the whole of the Trireme Trust’s archive, the plans by John Coates have been lodged with the archivist at Wolfson College, Cambridge (archivist@wolfson.cam.ac.uk) who now administers the provision of plans and photographs, as well as copyright issues, on behalf of the College and the Coates family."

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Posted (edited)

Still planking canopy sections...10 out of 12 done so far. Embarked on another project to fill time while glue on planking is drying. The fairing piece between the quarterdeck and the stern is shown in John Coates drawing no 23 (excerpt below):

 

Plan-23-Quarter-Deck-extract.thumb.jpg.50718b625b2e23d01d0c6320cbc0ad78.jpg

In plan view the faring runs in line with the gunwale as it curves into the stern and also needs to be vertical so that it mates with the vertical stanchions supporting it along its span. This makes it quite a complex shape to lay out.

 

Edited by Richard Braithwaite
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