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Old Mar 04, 2013, 06:12 AM
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Ballarat, victoria, Australia
Joined Oct 2007
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Bismarck electric set up 1.7mtr

Please Help.
i am trying to help my friend with his scale ship that his granfather has built from scratch.
i have had a few years bulding elctric planes but no nothing of boats.
these are the details i have
1.7Mtr long 240mm wide
aprox 11Kg
3 props ....32 mm diameter with a 30deg rake(2 props spin right 1 prop spins left)

what my freind needs
4-6ch TX and RX
3 motors
3 esc??? needs forward & reverse
rudder servo and maybe 1 or to others for extra's
Battery/charger to suit

i am into Lipo & brushless motors but not sure if this is the go for boats of this size.??
i was thinking of maybe a Hobby king tx/rx 6 ch

please help
cheeers
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Old Mar 04, 2013, 06:47 AM
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Blackpool, Lancs
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Motors, 3 of, RS545, to run on about their stated voltage.
ESCs 3 of marine types capable of 15A, say Mtronics Viper 15s. Other makes are very suitable, but generally avoid the extravagant claims of some of the oriental manufacturers.
Any standard size servo will be OK for the rudder.
If the motors are rated for up to 15v, a 12 volt SLA will provide plenty of power and the required ballast as well as offering relatively simple care. If required, more than 1 can be fitted, might be easier for size and weight distribution (1 per ESC?)
To work 3 motors, simplest way is to have all 3 on one stick. Not many radios have 3 sticks suitable for individual motor control, so mixing is then useful. I'll let somebody else talk about transmitter mixing. It is possible to get hardware mixers for the RX end, but not all work with all 2.4GHz sets. Most were designed with AM/FM sets in mind, which distribute the signals to the channels sequentially - 2.4GHz sets often send the information for all channels as a single block, decode it for the channels and offer it to all channels simultaneously. This creates confusion with many mixers.
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Old Mar 04, 2013, 09:49 PM
Central Alabama RCShips, Sails
WingRider05's Avatar
United States, AL, Odenville
Joined Feb 2006
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Check here for motor mixers, allows you to operate 3 motors off one channel. I don't believe you'll have any problem with a 2.4 Tx/Rx. Check out the P40D.

http://www.action-electronics.co.uk/mixers.php
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Old Mar 05, 2013, 06:14 AM
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Ballarat, victoria, Australia
Joined Oct 2007
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Ok had a look at your suggestions they recommend separate batteries for each motor ? Do you think this is needed?

Could I maybe run 1 battery for everthing?

Also I am in Australia do you think they will ship or is there some other suggestions?

Thanks for all your help
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Old Mar 05, 2013, 07:51 AM
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Australia, WA, Garden Island
Joined Nov 2010
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Originally Posted by Snibo179 View Post
Ok had a look at your suggestions they recommend separate batteries for each motor ? Do you think this is needed?

Could I maybe run 1 battery for everthing?

Also I am in Australia do you think they will ship or is there some other suggestions?

Thanks for all your help
You could, but that depends on the capacity required, which will effect the size, especially the height, of the battery. Also consider it's weight and the point loading it will put on parts of the hull structure beneath it.
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Old Mar 05, 2013, 11:32 AM
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Blackpool, Lancs
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Within limits, when you buy batteries, you are paying for capacity - a battery with twice the capacity might be cheaper than two (or three) smaller ones, but not that much cheaper. In a large model, although it might be able to carry one large battery, you might well be limiting yourself to putting that battery somewhere inconvenient. More than one, you have the opportunity to spread the weight out and put the centre of gravity where it is needed. This also helps the model ride the waves more realistically.
SLA batteries are commonly used in things like alarm systems. I expect that there will be suppliers, even in Oz. Don't use automotive (car or bike) batteries. They tend to vent acid fumes which eat electronics.
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Old Mar 05, 2013, 02:40 PM
Central Alabama RCShips, Sails
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United States, AL, Odenville
Joined Feb 2006
544 Posts
Snibo179

A lot of guys used SEALED lead/acid batteries in their boats. I agree, don't use an automotive/cycle batteries. They vent hydrogen gas and may even cause an expolsion. As large as your boat is, you may consider using three small sealed batteries ( http://www.batteryspace.com/sealedle...ry6v45ahs.aspx )for 6 volt, or (http://www.batteryspace.com/sealedle...cylightss.aspx ) for 12 volt. (Suggestions, you may want to go larger or smaller in amp/hrs.) The volts will depend on the motors your using. At about 5 feet long, consider 3, 12 volt 700 series motor. You don't want the boat to plane, but you do need the torque of a 12 volt motor. I assume that you are running the motors with direct drive and not a gearbox.

Use an automotive style charger for the sealed lead/acid battery. The ESCs will have to be matched with the voltage and the amps pulled by the motors.

You may want to use one large 6 - 12 volt battery. Run a bus for the + (positive)and another for the - (negative). From the bus connnect a lead to each ESC, then hook up as required. One of the guys in our club runs a Mr Darby tug on 12Volt sealed lawn mower battery!

If you don't want the lead acid consider LiPo. They are more expensive and you can get by really well without them.

I would use the lead/acid myself. If you have room, I'd go with the 3 seperate batteries. Install your running gear and see if they'll fit. You'll probably need something for ballast anyway.

I've ordered from Action Electronics before and have not had a problem with overseas service. I don't think you will either.

The Hobby King radio will work great with your model, just be sure it's 2.4 GHz.

I hope this helps.......

Post some photos and show us your pride and joy!!

Jared
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Old Mar 06, 2013, 03:09 AM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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If you wanted to go Lipo and brushless with that size prop a 28 mm diameter out runner to give you about 6500-9000 rpm unloaded, so a 1200 Kv on 2 cell or a 800 Kv on 3 cell li-po. you should not need any-more than a 15-20 amp ESC, the cheap Hobbyking car ESCs have worked for me.

One battery is fine to run all the motors, Gel Cell is appropriate, if 6 volt battery is what you endup using the Kv of the motor will need to be increased slightly, I see even Supercheap sell them these days

Cheers
Nick
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Old Mar 06, 2013, 05:30 AM
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Ballarat, victoria, Australia
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Hmm now you have me thinking should I go lipo and brushless ....do u think I need to worry about changing prop speeds when turning?
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Old Mar 06, 2013, 05:40 AM
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Australia, WA, Garden Island
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Originally Posted by Snibo179 View Post
Hmm now you have me thinking should I go lipo and brushless ....do u think I need to worry about changing prop speeds when turning?
The only problem that i'm finding with brushless motors is that their low-speed operation, especially on low kv motors is crap (lots of cogging), unless you can get a sensored motor. In all the prior-preparation i'm doing, finding a sensored outrunner.... well I haven't found one yet

Brushed should do the job just fine, and prop speeds wont matter. Are you using independent throttles for the outer props? then you can just reduce revs on the motor on the inside of the turn if you have to, for a tighter turn when needed. Or at low speeds/port maneuvering, even reverse it to assist with turning the ship.
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Old Mar 06, 2013, 06:01 AM
NeverAgainVolunteerYourse lf
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I generally don't have problems with low speed, sometimes the ESC makes a difference and sometimes just a little too much friction will affect the slow speed, I've had in my springer the motor ticking over so slowly you could count revs ie about 50 RPM, this did not move the boat

Nick
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Old Mar 06, 2013, 06:07 AM
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Australia, WA, Garden Island
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Originally Posted by nick_75au View Post
I generally don't have problems with low speed, sometimes the ESC makes a difference and sometimes just a little too much friction will affect the slow speed, I've had in my springer the motor ticking over so slowly you could count revs ie about 50 RPM, this did not move the boat

Nick
That's very interesting. Everything else iv'e read says that low speed operation on the non-sensored motors is quite bad
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Old Mar 06, 2013, 06:20 AM
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Blackpool, Lancs
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Use an automotive style charger for the sealed lead/acid battery.
I would not do that, SLA require the correct type of charger, and one of these is much cheaper than buying a replacement battery then getting the right charger. Auto types are not well enough regulated for SLAs, and if used, need constant supervision to prevent destructive overcharging. Overcharging leads to venting, when an SLA has vented you find that the "S" means "Sealed", which means that you can't top it up.
As to size, the completed model floating at waterline, should weigh about 33lb - this should help give some clues as to what size of battery or batteries to fit.
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