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Old Dec 18, 2012, 04:05 PM
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Help with motors for plastic model Fletcher Destroyer

My dad recently finished a 1:125 "Blue Devil" Lindberg model of the Fletcher class destroyer. He modified his to have the actual markings and signal flags of the USS Fletcher. Anyway, we want to turn this into an RC boat with some interesting twists. I have a little bit of experience mucking around with RC, but not a lot. I'm familiar with the concepts of the transmitter, receiver, and ESC. I've scratch-built a foam-carved boat using junk I scrapped from a park flyer and actually successfully used a PC case fan as its motor (rather than the motor from the park flyer). It wasn't fast, but it worked. You can see the video here:
PC Fan RC airboat final competition (0 min 47 sec)


Anyway, as I mentioned, there are a few twists with our destroyer project. First off, we want to use 2 motors (and 2 ESC) for independent engine control. I pretty much already know how to do this. Where things get interesting is we will be building an engine telegraph on the transmitter for each engine. Instead controlling the pots for the throttles directly, we will be selecting what we want the engines to do via a simulated telegraph. The options will be:
All Stop
Ahead 1/3
Ahead Full
Ahead Flank
Back 1/3
Back Full

And both engines will have all 6 options. I'm not sure if we're going to employ a lever for each engine, a slide pot, a rotary encoder, or a set of microswitches. The input for each engine will be read from the Arduino and the Arduino will operate 2 microservos to physically turn the 2 throttle pots. The reason for this is I will be programming the Arduino to slowly change the speed of the engine. If you are at "All Stop" and you order "Ahead Flank", we want the engines to slowly engage and get up to flank speed like they would in real life. I'm also putting a 2x16 character LCD display which will show the current engine orders. The left side of the LCD will be for the left engine and the right side will be for the right engine. When an engine order has been given, the display will flash the new order while the engine is transitioning. When it reachs the new order, the display will stop flashing and an MP3 player will play a sound effect like "Engine room answers Ahead Full".

Anyway, long story short. Here's where I need some help. I don't know what to use for the engines. This is a small model and we don't need or want the model to go fast. The screws (props) are pretty small -- maybe just over 1/2" in diameter. We're trying to keep cost down. What motors and ESC would you recommend? I'm kind of lost here. Keep in mind that we need 2 motors and 2 ESC's.

We're probably going to use something like this for the transmitter and receiver (we'll gut the TX for our purposes):
http://www.hobbyking.com/hobbyking/s...x_Mode_1_.html

Thanks for any help.
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Last edited by Skystream; Dec 19, 2012 at 08:38 AM. Reason: Correcting model information
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Old Dec 18, 2012, 06:28 PM
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The Arduino telegraph project sounds like fun, I've thought of similar before for steamboats.

You may find that the dual control is of limited use, as the long skinny Lindberg Fletcher (about 3' long actually) may not respond noticeably to the differential thrust of two closely spaced props.

The Fletch is easy to overpower... a couple 380 motors of suitable voltage may be fine... though you may find it easier to get slower motors in a larger size... look up my thread on "Integy Lathe Motors" here.
How slow is needed? I think the kit props are closer to 1" (I could be mis-remembering...). See my gearing article http://matthewsmodelmarine.wordpress...all-geared-up/ for useful info there, and if you don't use a gearbox, that just means you have a 1:1 speed ratio.
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Old Dec 19, 2012, 07:34 AM
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Joined Feb 2006
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At 4 ft long, that makes it a 1:96 Fletcher (Deans marine?).
I have just measured the props on my 1:125, 18" long minesweeper - they are 1/2" diameter. I suspect that for a larger, faster larger scale boat the props would be considerably bigger than that - think about 1" to 1-1/4". Driving these would need a pair of 380/400 motors on their full rated voltage, if it is the Lindberg at 1:125, that would be about 3 feet, same motors, maybe a lower voltage battery.
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Old Dec 19, 2012, 08:35 AM
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Sorry, the model is actually the Lindberg "Blue Devil" 1:125 scale, which is 3' long, not 4'. My dad made his into the actual U.S.S. Fletcher and used the correct signal flags and numbers for the Fletcher.

So what does 380 and 400 mean? I guess that's where I need to get educated. What voltage battery would you use? Would you recommend using 2 battery packs (obviously disconnecting the BEC from one of the ESC's)?
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Old Dec 20, 2012, 08:59 AM
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I'm still stuck after spending hours surfing the web and reading tons. I've figured out that 380 & 400 are "can" sizes, but a lot of websites don't seem to use these values. I still don't know what to buy. Do I want a brushless inrunner? HobbyKing lists motors by mm, but by the can size. I don't know how to correlate the two. Can sombody suggest a couple of motors (with actual links) that I can take a look at?
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Old Dec 22, 2012, 08:51 PM
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Nah, you want brushed motors. Brushless are high speed and meant for low displacement speed boats.

http://www.rcgroups.com/forums/showthread.php?t=1501148
http://www.rcgroups.com/forums/showthread.php?t=1237484
Many resources on RCGroups, just have to search.

Here's a buildup I particularly like: http://www.modelboatmayhem.co.uk/for...?topic=37890.0

He used 2x 280 motors from http://www.mfacomodrills.com/motors/280.html

Are you aware the USS Fletcher was an early, round, high bridge Fletcher class? Did your father convert it to round bridge? Not as if it really matters as the Lindberg kit is not very accurate to begin with, but it would be nice to see it if he did.
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Last edited by Harquebus; Dec 22, 2012 at 08:56 PM.
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Old Dec 24, 2012, 09:23 AM
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Thanks for the links. Yes, we're aware the real Fletcher had the round bridge. My dad thought about trying to make a rounded bridge from balsa and I suggested maybe styrene, but he decided he didn't want to try to tackle this. So we have the flat bridge that the kit comes with.
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Old Dec 24, 2012, 01:12 PM
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Quote:
Originally Posted by Skystream View Post
Thanks for the links. Yes, we're aware the real Fletcher had the round bridge. My dad thought about trying to make a rounded bridge from balsa and I suggested maybe styrene, but he decided he didn't want to try to tackle this. So we have the flat bridge that the kit comes with.
Skystream -- the early Fletchers had round bridges, but the later ships in the class had the lowered open bridges, as depicted by the Lindbergh kit, so unless you are building a particular round bridge ship, you can leave the kit parts pretty much "as is."

For a wealth of information on the Fletchers, go to this link: http://www.navsource.org/archives/05idx.htm Then go to "Gun Destroyers" and start looking at the ships from DD445 (Fletcher) to DD 691 (USS Mertz), those are all Fletchers. The open (square) bridge ships start at about DD 596 (Shields).

There were also at least two configurations of the open bridge Fletchers. A number of the earlier ships were given an emergency anti-aircraft refit, where the forward torpedo tubes were removed and an "island" with the 40mm directors was installed in that area, the aft twin 40 mm were moved forward and replaced with quad 40 mm guns and the 20mm guns were replaced with twin 20mm guns -- those being the most obvious changes. But if you want a look at the configuration depicted by the kit, you can find the USS Melvin (DD 680) herself, and a number of sister ships in variious camouflage schemes in the photo index.

Some of the "bulwarks" in the kit were actually canvas-covered railings. This earlier Fletcher conversion article is quite accurate regarding what bulkhead areas to remove and replace with railings:

http://www.steelnavy.com/BDFletcher.htm

You can also find a lot of information and photos at this site: http://www.shipmodels.info/mws_forum...hilit=fletcher

I would strongly recommend the build on Model Boat Mayhem recommended by Harquebus. It is an excellent conversion, and uses the photo-etch parts specifically designed by Tom's Modelworks for the Lindbergh kit. There are a number of links in that build to other conversions, as well, and a link to Toms Modelworks, where you can order that photetch set.

Finally, if you want some inspiration, check out the models built by Fine Art Models. Go to this link, http://www.fineartmodels.com/fineart...com/Ships.html then click "Fletchers, Fletchers2 or Fletchers3" and you will see some stunning modeling.

I wish you the best of luck on your build. Keep us posted, and Happy Holidays!

Pete G.
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