Speed control

[Guest]

Re: Speed control

Alright. I'm begining to get this. So my next question is this. How do you decide the size of prop and shaft? I'm thinking of getting two 18 to 20 amp motors. With two ESC's that can run up to 30 or so amps just in case I want or need to upgrade. So does that help with the shafts? IS THERE A CHART??? LOL.

I want to say thanks to everyone who helps! The knowledge is being used. And I will be posting the build. May even do a small website for it.

mark

[Guest]

Re: Speed control

This is more than I wanted to spend. But! it looks good.

http://www.ebay.ca/itm/Hacker-Combo-A20 ... 20c640e44c

[JWLaRue]

Re: Speed control

I'd really like to know more about the size and weight of the sub that you are planning on building before offering any thoughts on the motors that you are looking at. I say that primarily because even with the larger subs being built, assuming that you are running 20 amps through a motor is a *lot*.

-Jeff

[Guest]

Re: Speed control

Wait. What? 20 amps is a lot? Really? I'm thinking two foot hull. I was going to get a esc that was 8 amps and it was too little.

I'm ready to purchase these things so I can get this thing going.

[JWLaRue]

Re: Speed control

Okay...are you looking to design a hull around a motor or select a motor to fit a hull size?

So...the 20 amps. Here's an example of one of my subs. It's a 1/72nd scale Skipjack which is 42 inches in overall length. I run that with a single Graupner Speed 500 motor. At full speed (probably about twice scale speed) I am only pulling around 3.0 amps. I use a 12-volt, 6-AHr battery, which easily yields me 2 hours *if* I were to run a full throttle. Actual use is several hours over that.

-Jeff

[Guest]

Re: Speed control

Some ESC specs can be very optimisitic. This can be especially true of some of the cheaper ESC's from the Far East.

If the controller is well made and designed, then it's unlikely you need anymore than 10A in the vast majority of installations. To power a submarine of modest size at moderate speeds only needs a few watts usually. These days it can be quite difficult to find a controller in production with such a low continuous current rating unless it's very small. Most controllers start at 15A and go upwards. The controllers I use allow 25A continuous operation, and are small enough for most models.

Having a larger controller doesn't hurt, but no sense in paying over the odds for a controller that can deliver more than what you require.

For a boat of around two feet a shaft size of 1/8" or 3/16" is more than adequate. Here in the UK, we tend to use metric sizes,a nd 4mm is a popular size for shafts, with smaller models sometimes dropping to 3mm.

I recommend you get this book if you're serious about scratchbuilding a sub- http://shop.traplet.com/product.aspx?c=294

It's a tough read, especially if you lack a technical background, but most bases are covered in this book. It deals largely with theory and concept, there is little in the way of instruction on how to prqctically build the items beyond a few hints and tips. What it does allow you to do is calculate things like hull strength, displacement, sealing, power requirements and ballast systems. It is by no means exhaustive, and I'd avoid building any of the electronics in the book, as they are rather dated, with out of production components listed, plus some of the schematics are a bit suspect.

[Guest]

Re: Speed control

Well guys I have to thank you for all the help. I know what my next step is. I'm going to a sub with some brush motors and brushless Esc''s FOR NOW...why? To save money while I learn what the hell I'm doing. When this sub is floating and working. And I'm ready to go the next step I'll go brushless. I will go with Mtroniks at that time for sure. They seem to have a great product. I have aquired some very good, good torque brushed motors.

Now for the ESC's. Ebay is full of them. And I want two wthat have two way control with BEC's. Can't seem to find anything that is cheaper than a Brushless one. Or any auction that has the info I need. And sellers are not replying.

Any suggestions?

[greg w]

Re: Speed control

if you are going with a brushed style motor you will need a brushed speed control. some of the brushless esc's can run a brushed motor but most do not. Greg

[Guest]

Re: Speed control

Brushless motors are great, but in this application, unless they're sensored they will have a number of disadvantages over a brushed set-up, owing to their start up characteristics. I would say nearly all model submarines I've seen are powere by brushed motors, and their owners are very happy with the performance.

Some brushless ESC's can be used with brushed motors e.g. CAstle Creations range. however these controllers are quite expensive.

Mtroniks controllers are quite inexpensive, but if the list price is too much for you, have a look at their ex-demo range e.g. http://www.mtroniks.net/details1.asp/Pr ... EXDEMO.htm

BTW a sub based on a single motor with rudder and rear hydroplanes will be easier and cheaper to set-up. You only need one ESC, one motor, one stuffing box, no mixer etc.

You can get some good items off ebay. But you can also get some complete rubbish. Caveat.

If you use two ESC's with BEC, you only connect up one of the BEC's, otherwise they interfere with one another.

[Guest]

Re: Speed control

Lol. You guys are killing me. Just when I figure a direction to go SOOOOO many options are opened back up to me. I need to make a decission. I think i'm going to go with a base kit. I'm thinking either the bluefish or the Akula I can get them up and running pretty fast compared to what I was planning. I just want a ballasty stystem.......

Lord help me. I"m hooked.

[Guest]

Re: Speed control

You're referring to the Dumas kits, right?

I'd give 'em a miss if I was you.

Good starter subs are available. Thunder Tiger Neptune, Robbe Seawolf, or you could look at some of the plastic kit conversions like a Trumpeter Kilo, which is a nice small sub that handle well and isn't very expensive.

The neptune in particular has a high level of build quality. You can only get it as a ready to run in the States. It is available as a kit here in the UK.

As standard they look a bit toy like IMO, but you can soon alter the appearance of these boats to something more suited to your own tastes.

[giovanni]

Re: Speed control

Take a look at the Caswell submarine kits.

http://www.caswellplating.com/rc-modeling.html

[Guest]

Re: Speed control

Well I checked out those subs. And they look great. But money is an issue here. I can't spend large ammounts on something I've never tried before. On a whim I went to my local hobby guy (only one in my town of 150 000) And he happened to still have the Dumas Akula he had 6 years ago. Still sitting there. In box. Covered in dust. Now with shipping I can get one of these for 230 bucks sent to me. He said I could have it for 120.
As my first project...I can't pass that up. No matter how crappy the kit is. It will teach me WTF I'm doing.

And at that price I'm going with a brushless ecm and motor combo from Mtroniks.
Thanks for the help guys. I'll keep you all posted.

[giovanni]

Re: Speed control

Caswell has the Moebius USS Skipjack for only $85.00.

http://www.caswellplating.com/rc-modeli ... -1-72.html

[JWLaRue]

Re: Speed control

He's looking to build a r/c sub model. That is a static model. Any internals to make it a functioning r/c sub would be in addition to that price.

That said, there's nothing wrong with the Dumas Akula as a first-time r/c sub. SC member Crazy Ivan has a great example of one that has been built, run, and then served as a platform for upgrading.

-Jeff