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Author Topic: Beginner needs help  (Read 2558 times)

overfall

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Beginner needs help
« on: August 18, 2007, 03:11:11 PM »

Please forgive my ignorance before i start,I'm a complete beginner in this Hobby,and this is my first post.I have purchased two fibre glass trawlers each measuring 30"x10"and both have electric motors ,one brushed and one unbrushed.Because I have no history of the boats,never having met the previous owner,I have no idea of model or motor size etc.Can anyone tell me if there is a formula for calculating engine size based on model size?.Would it be a better option to start from scratch and install my own motors and again if so what size.I've attached a couple of pics of the motors,hopefully someone may be able to give me some idea.Thanks. Jim
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overfall

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Re: Beginner needs help
« Reply #1 on: August 18, 2007, 03:14:27 PM »

Here are the boats

 JIM
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cbr900

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Re: Beginner needs help
« Reply #2 on: August 18, 2007, 03:58:04 PM »

Welcome to the Forum,
 Not to sure on the brushless but the other looks like a standard Tamiya 540 can...........

Roy
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overfall

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Re: Beginner needs help
« Reply #3 on: August 18, 2007, 04:05:45 PM »

Many thanks on that Roy,at least thats a start.
PS Roy it has to be a Ninja. ;)
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Ghost in the shell

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Re: Beginner needs help
« Reply #4 on: August 18, 2007, 04:10:38 PM »

i think that second motor may be brushed, possibly an old train motor
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overfall

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Re: Beginner needs help
« Reply #5 on: August 18, 2007, 04:19:34 PM »

Thanks for that Ghost in the shell,It is indeed brushed and is quite large 3" in diameter,would it be better removing it and replacing it with a newer motor.
Jim
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FullLeatherJacket

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Re: Beginner needs help
« Reply #6 on: August 18, 2007, 05:51:14 PM »

Jim

For the potential problems that these motors may cause you - particularly the brushless one - and the relative cost of replacing them with something known/cheap/cheerful you'd be well advised to bin them and start again. A couple of tame Mabuchi/Sun 540s will cost you a fiver apiece, plus a quid (tops) for the suppressors. Run them on 6 volts and you can use a fairly lowly speed controller - I'd guess 10A as an absolute maximum.

Good luck - they look nicely made. Send me a PM if you need any specific advice.

FLJ
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Ghost in the shell

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Re: Beginner needs help
« Reply #7 on: August 18, 2007, 06:14:41 PM »

Thanks for that Ghost in the shell,It is indeed brushed and is quite large 3" in diameter,would it be better removing it and replacing it with a newer motor.
Jim

i have a belief that if they work, then they need not be replaced, power them up and see what happens.  if your radio goes schitzophrenic then they may be in need of changing. as for what to, that could be anyones guess, however a 545 or similar may be ideal, like FLJ says,
A couple of tame Mabuchi/Sun 540s will cost you a fiver apiece, plus a quid (tops) for the suppressors. Run them on 6 volts and you can use a fairly lowly speed controller - I'd guess 10A as an absolute maximum.
, modern motors aint that expemnsive.

see how they go first
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overfall

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Re: Beginner needs help
« Reply #8 on: August 18, 2007, 07:09:06 PM »

Thanks lads, the information is very much appreciated.It goes against the grain to discard anything,I'm the one at work who tries to repair everything when everyone else fits a new one from the store,but the motors are a bit of an unknown quantity.I'll probably go for motors, with matched speed controllers,something like you've suggested,at least I'll know what I'm dealing with.
Jim
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kiteman1

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Re: Beginner needs help
« Reply #9 on: August 18, 2007, 09:08:19 PM »

The second motor looks like a car heater blower.  I used similar ones from a Cortina some years ago.  Maybe the best idea would be to follow advice already posted............
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overfall

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Re: Beginner needs help
« Reply #10 on: August 19, 2007, 08:39:50 AM »

Thanks Kiteman 1. I presumed these motors would have been motors designed for models but obviously not.I suppose the origin of these motors could virtually be anything.
Cheers,Jim.
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malcolmfrary

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Re: Beginner needs help
« Reply #11 on: August 19, 2007, 12:45:08 PM »

No doubt real naval architects will have a formula, but I usually look at the assumed, or published horse power of the original and the scale.  I then multiply the HP by 745 to convert it to watts.  Then take the cube of the scale and divide the watts by that.  To be on the safe side I usually multiply that by 1.5. 
Then I look at the current draw of motors that I know, and then for a 30" long trawler I put in a 385 or a 5 pole 400 rated for 15 volts and run it on about half that. 
If there is a bit too much power, no worry, just remember that you don't have to run with the wick turned all the way up all the time.
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Ghost in the shell

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Re: Beginner needs help
« Reply #12 on: August 19, 2007, 01:15:07 PM »

No doubt real naval architects will have a formula, but I usually look at the assumed, or published horse power of the original and the scale.  I then multiply the HP by 745 to convert it to watts.  Then take the cube of the scale and divide the watts by that.  To be on the safe side I usually multiply that by 1.5. 
Then I look at the current draw of motors that I know, and then for a 30" long trawler I put in a 385 or a 5 pole 400 rated for 15 volts and run it on about half that. 
If there is a bit too much power, no worry, just remember that you don't have to run with the wick turned all the way up all the time.

however that extra bit of power is always handy for getting you out of trouble.
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overfall

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Re: Beginner needs help
« Reply #13 on: August 19, 2007, 07:02:22 PM »

malcolmfrary and ghostintheshell thanks for that information.Its good to get an idea of what other more experienced people actually use,and then at least I have somewhere to start from.Because the models were bought without any relevent information and not having any previous model boat experience its nice to know there is someone willing to help,and all this because the youngest son was given a kit a Christmas which involved building a DC motor from a kit and installing it in a small plastic boat.But if I were to be honest I always had a hankering after a boat anyway and,well it was too good an opportunity to miss.Although if I had had my way I would have built a kit,because i love building.
Many thanks.
Jim.
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kiteman1

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Re: Beginner needs help
« Reply #14 on: August 20, 2007, 07:59:47 PM »

It's all very well putting low powered motors in a model but if you get a good blow there's a lot to be said for a bit of extra power in hand. 
It's like buying a 1200cc car, putting five people in and loading the boot up too and then expecting an easy ride on the M1................

You need that power in hand for the unexpected squall coming out of nowhere .........
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