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Old Jul 27, 2012, 06:15 AM
Tally Ho!
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Help!
Information wanted on working oar system Roman Warships

Hello all,

I am building two warships of the Roman era. The 1/72 Academy Roman warship:



And the Zvezda 1/72 Bireme :



Now I would like to know how to make a working oars system. I might not use these models to make RC but the Zvezda one is 50 cm in length.

I would like to construct a Roman warship with working oars system.

Any info on how to make it will be very welcome !

Best wishes,

KM
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Old Jul 27, 2012, 11:18 AM
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http://www.rcgroups.com/forums/showt...&highlight=oar
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Old Jul 27, 2012, 02:01 PM
Webmaster, MMCNE
Acton, MA USA
Joined Feb 2000
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I've given a lot of thought (daydreams, doodling) to this idea over the years. Some (random) thoughts:

First off- have you ever rowed a boat? If you haven't, get out there and try it. Pay attention to how the inboard end of the oar moves as you row along. You'll see that your hands move in what could best be described as a "squashed circle".

If you move your hands in a true circle, it isn't as efficient, but you can still move along pretty well. I always figured that implementing a circular motion for the inboard end of the oar would be easier to do on a model.

The geometry is important-- the pivot point (oarlock) needs to be roughly a quarter to a third of the way down the oar from the inboard end-- you want the oar blade to be moving in a much larger circle than the one traced by your hands.

I was thinking about a wheel or crankshaft to power the oars. Imagine how you'd power just one oar, to work out the geometry, then extend the concept to a whole bank.

You don't need a wheel or crasnkshaft to power every oar in a bank of oars-- I'm thinking of a mechanism like the wheels on a steam locomotive. You have a wheel at each end, connected by a rod. As the wheels rotate, any point on the rod moves in the same diameter circle. Put a wheel at each end, with the oars attached to the rod. Now, they'll all move in synch together.


Like all operating models, the scale effect comes into play-- you can't scale down the behavior of the water. A 1/72 scale model could be made to work, but would need flat calm water, as the oars would only be a half inch or so above the surface of the water on their return stroke. (If they hit the water on the return, they act like a brake.) A larger scale model of a smaller prototype will perform better for a given model length .

I would stay away from mulitple banks of oars on a first effort-- that is going to increase mechanical complexity.

Hope this helps....
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Old Jul 27, 2012, 02:09 PM
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Sure helps a bit I have found little information on how to do it. There are some people who have made it work but the videos are sketchy at best.... An oval movement would be best imho. I am just contemplating how to do it since my TX is a Dx7 for airplanes... So I probably have to fiddle about with some channels. Also I am in doubt whether or not to use one motor for both oars and a rudder underneath I could make it into steering oars by separating the two but still.. that seems cumbersome to me. I also want to have working sails.

KM
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Old Jul 28, 2012, 12:01 AM
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United States, ID, Rexburg
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I found this one after a quick search on oar powered ships (I thought I had seen something like this on youtube!).
Mike Sheppard's Trireme (1 min 27 sec)
Found this one of a full scale trireme showing the oarsmen and the setup aboard.
SeaTrials of the Trireme Olympias (14 min 17 sec)
I also found this one.... http://richardsmodelboats.webs.com/ Hope any or all of this is of some help.
Foo
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Old Jul 28, 2012, 12:08 AM
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Multiple working oar systems

We have had 3-4 models made in the LA area, with the systems you are wanting to make. All the models have been made through trial and error, by some VERY skilled scratch builders. All of them had machining skills, or had a friend that did. I would not attempt it, not that I could not do it, but the amount of engineering, and fabrication is massive. Just to let you know, I have 20+ yrs., in custom fabricating and machining, of parts for Show Cars, and Race Cars. I am not trying to deter you, just to let you know what you are in for. CaptCB
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Old Jul 28, 2012, 03:49 AM
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I know it will be difficult I saw one topic on here and in a ship builder forum of one of our members apparently succeeding,

http://www.rcgroups.com/forums/showt...ighlight=birem

There were more pics and a small vid of his rowing setup but I still do not understand how he did it...

KM
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Old Jul 28, 2012, 04:29 AM
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Quote:
You don't need a wheel or crasnkshaft to power every oar in a bank of oars-- I'm thinking of a mechanism like the wheels on a steam locomotive. You have a wheel at each end, connected by a rod. As the wheels rotate, any point on the rod moves in the same diameter circle. Put a wheel at each end, with the oars attached to the rod. Now, they'll all move in synch together.
The trick is to ensure that the row of holes in the connecting rod matches exactly the row of holes in the hull for the oars, and thus the row of fulcrums for the oars.
When I look at the models, I sometimes wonder at the accuracy of the length of the oars - if they were as long as some show, it would be like the rower on each one working a telegraph pole, bearing in mind the shortness of the inboard length, and there would be more energy put into lifting the oar out of the water than spent driving the boat forward, add to that the energy spent overcoming the inertia of all that weight of wood with each change of push and pull.
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Old Jul 28, 2012, 04:55 AM
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Well the sizes of the oars are known from ancient literature. Here is a diagram of the rowing positions :





The oars on the models most of the times are not very accurate indeed.

KM
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Old Jul 28, 2012, 11:54 AM
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Km

I will see if any of our guys have photo's around, the guy with one of the nicer models, doesn't come to the pond much anymore. I think at least one of the models, was in Scale Ship Modeler, and the artical had photo's with the deck off. CaptCB
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Old Jul 28, 2012, 01:10 PM
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That would be ever so helpful ! !

Thnx !

KM
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Old Jul 28, 2012, 02:33 PM
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Trieme

Here are some pictures of the Trieme static model I made a few (cough, cough) years ago. Hope they help, but not mechanically operated.

Herman
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Old Jul 29, 2012, 05:00 AM
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On the 16 (post #9) the inboard guys must have done a heck of a lot of running, while the outboardmost must have been nearly spectators. Of course, the inboard one or two might have been the counterweight to lift and return the oar, even so, it seems a cumbersome arrangement. Maybe why it didn't catch on in a big way? The smaller number of longer oars has got to be easier to arrange in a working model, though. Fewer working parts, fewer holes to drill in the connecting rod.
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Old Aug 05, 2012, 12:34 PM
Webmaster, MMCNE
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Joined Feb 2000
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Some additional thoughts:

You mentioned you want to add sails-- I've thought aboujt that, but I just don't see it as a viable option in a model. The problem that those ships really only used the sails when going downwind-- you won't be able to sail into the wind at all.

Back in 2008, I attended the International Model Boat Show in the UK. In one of the indoor pools, they had a couple of large oar powered ships. The boats worked reasonably well, in part because the pool was absolutely flat calm. Like paddlewheelers, oar powered vessels have to deal with the fact that you can't scale water down-- adn the slighest breeze is like a gale on the pond.

I did see one square rigged sailing model that had a very clever, effective "cheat". While it had working sails, it also had a hidden auxiliary power source-- a water pump. The outlet was embedded in the keel, and provided some additional thrust and flow over the rudder- not as effective as a prop, but much less noticable, too. That technique could be adapted to an oared boat......

In regards to control systems, I think independent control of the oars is essential-- like you'd have in any rowboat. This can be done with a 2 channel radio-- using a mixer like they use in RC tanks.
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Old Aug 05, 2012, 02:45 PM
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Ah yes that is indeed a good idea.

About square riggers, there is an entire topic devoted to that on RCGroups and they work wonderfully well. If I would add sails to the Roman ship I would of course cheat and make a keel....

KM

http://www.rcgroups.com/forums/showt...ht=hms+surpris

http://www.rcgroups.com/forums/showthread.php?t=611006
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