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Speed control

R/C Submarine modelers

Speed control

Postby Ahab79 » Fri Jul 06, 2012 11:46 am

I'm new to this forum and I'm building my first sub. I'm starting from scratch and my first build is going to be very basic.

I've got a Futaba transmitter with receiver. I'm presently shopping around for two Electric Speed Controllers and two brushless motors. I'd like to get some that just fit into the Futaba reciver with out much splicing/soldering. I know next to nothing about R/C's so I'm self teaching at this time. Any suggestions? I'd hate to buy something and try to wire it all up and find out that what I purchased just isn't compatable.

Thanks

Ahab79
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Re: Speed control

Postby salmon » Fri Jul 06, 2012 12:20 pm

Welcome. How old is your Futaba? Do you know if the frequency is still good for surface/boat usage? The old style (G style) servos had pins (male) that would go into the receiver (female). Current style (J Style) is the opposite it is pins on the receiver. Other brands of modern servos are the J style. You can see a picture here: http://forum.sub-driver.com/showthread.php?1652-Newbie-no-more-Building-the-Revell-1-72-Gato/page11&highlight=futaba. There are cables out there that will convert the old style to the new one..... Tell us about the Futaba you are going to use, what model, frequency?

Curious, What are you wanting to build? The use of two speed controllers is not unheard of, just not common or not necessary.
Are you going to use static or dynamic diving system?

There are easy subs to build and there are difficult subs to build. Price can be all over the place. Depending on your skills, starting to build a sub from scratch can be very frustrating, but we will help as best we can. For your first sub, my suggestion is go simple and just get it to work. That alone will help you from getting caught up in so many different ways you can build a sub. I see many start, but few finish because there is a lot to learn and challenges to overcome. If you start chasing all the different do-dads that you can put on your sub, you increase the chances of stalling and putting it on a shelf to collect dust.

Tell us more about what you are going to do, the more you provide, the better the guidance we can offer.
Peace,
Tom
Oh, and post your build here.
If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.
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Re: Speed control

Postby Ahab79 » Fri Jul 06, 2012 12:46 pm

Thanks for replying Tom.
Wow where to start? This has been a dream of mine for almost 15 years. But I know my limitations. I live in Northern Ontario Canada. So resources are slim to non. Local hobby guy can be....upitty.

O.k. I'm building a sub based on plans I bought off ebay. IT'S NOT THE SUB I WANT. But!!!! It will teach me the basics. Learn to walk before running right? So I'm going with two motors port and starboard for thrust and direction. Going to build a ballast system to dive. ONCE I GET THIS RUNNING. I will move on to phase 2. I will build a more "traditional" sub. I'd like to go with a Upholder/Victoria class sub. But considering England sold us Canadians some defective products it might be a good idea to go with something else. (Insert smile)

My transmitter is for air not surface! Futaba FP-T7NFK Conquest 7 Channel. I'll be using it at my local pool or at the cottage wichis pretty remote. But for the time being it won't be making it into the water any time soon.

And the connections are J. It's an older transmitter. 7 channels. But it came with 5 servos. Reciever the whole nine yards. I got it for a killer price and I eventually want to make a sub that fires torpedo's. So 7 channels was too tempting.
I'm thinking for my reciever battery pack of buying a few battery boxes and stringing them together and putting rechargeable Lithium batteries. I can then take them out and Charge at home. But for all I knwo that's a dumb idea too. I knwo it will cost me space but for now I'm just concerned with getting the inards running. Then i'll start on trays hulls and so on.

So... what do u think about the ESC's? I'm finding all sorts of stuff on e-bay. I think i'm gong to buy some J connects and attempt to splice them if possible.
Thanks.
Mark
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With a face that was launched to sink.
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Re: Speed control

Postby Ahab79 » Sat Jul 07, 2012 10:00 am

I can't argue with the price on this.....but is it a piece of crap?

http://www.ebay.ca/itm/330731186124?ssP ... 1438.l2649
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Re: Speed control

Postby JWLaRue » Sat Jul 07, 2012 11:05 am

A couple of things come to mind......

That ESC is only rated for 8 amps. Unless you are building a very small sub I would look for one with a higher rating. Also, that only has a forward capability, no reverse.

It does have a BEC, so it would eliminate the need for a separate battery for the receiver.

May I suggest that you check out the line of speed controllers made by Mtroniks? That is one of the brand that gets used in a lot of r/c subs.

Finally, if you could provide us with some general specs for the sub you want to build, that will help in providing advice.

-Jeff
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Re: Speed control

Postby Sub culture » Sun Jul 08, 2012 11:48 am

Running a boat on an aero frequency isn't a very responsible thing to do, no matter how remote you are. Radio equipment is very cheap these days, so there isn't much excuse. The frequencies we have today were hard fought for, if the authorities had their way we wouldn't have anything.

I suggest building your boat first, you'll almost invariably find there is more to it than you think. Not sure what plans you have for a DIY sub. Some are good, many are very poor. The best designs will be based around a cylindrical pressure hull. Good working submarines can be built with watertight box arrangements, but you have to be very methodical with the construction if the boat is going to be reliably watertight.

Concentrate on getting the fundamental aspects right like a watertight hull, with good watertight control linkages and motor shafts. I recommend you purchase ready made glanded shafts unless you have access to a lathe and know how to use it. The seals and pressure hull strength are the most critical aspect of design- get those wrong, and your boat will always be a source of trouble.

Don't build too small- two to four feet is an ideal size, being big enough for most equipment, but still a manageable size for transport.

With all the mechanical aspects in place, it will be easier for us to advise on the best equipment to put inside.

All too often we get a newcomers brim full of enthusiasm, with a raft of questions on how to do this and how to do that.
We take the time and trouble to answer, the person finds things a little more difficult than they first envisaged, and they vanish into the ether.
'Why are you staring at an empty pond?'

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Re: Speed control

Postby Ahab79 » Mon Jul 09, 2012 7:06 am

First off I'm late for work and still sending this post. So trust me. I'm in it for the long hall. this has been a dream of mine for years.
Second. I did some checking. In Canada my radio is legal for use on grand vehicles such as boats and cars. So I lucked out there.

Third I'm learnign tons!!!! Thank you guys. What I'm having a hard time is figuring out my "budget" for my amps. I can buy an esc with a amp limit of 20 so that meens I can get a 20 amp motor. Gotcha. But what about the rest of my servo's? I don't want to ask you guys a million small questions. So where do I get a model electronics for dummies book?

Mtronics is AWESOME!!! Thank you. Will be purchasing from them for sure. Once I figure otu what I need.

My major confusion is batteries at this point. Is it possible for me to use a battery box...pruchase at electronic stores.... and plug in some expensive home use rechargables? Just till I can get a proper cell? And is a BEC totally necessary? I can see the benefits but it is more for saving space in the limited hull?
thanks
ahab.
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Re: Speed control

Postby Sub culture » Mon Jul 09, 2012 8:38 am

You need to take a step back and read carefully some of the replies you've been given on this thread and the other thread you started.

Before we can offer any really useful advise on equipment, you need to show us what it is you're intending to build, include the dimensions, and the performance you want with regards to speed and endurance.

Really these days, technology has reached a point where there are very few limits as to what you can or can't build. Fifteen or twenty years ago, the choice was much more restricted.

the advantage with BEC, is that you only have one battery to charge and maintain. Without it you need a separate receiver pack, which could be faulty, not taking a charge well etc. There are pros and cons to each system, I like BEC, and I reckon the vast majity of model submariners out there use that system. The only time I would advocate a non-BEC system is if the main battery was 6 volts or lower.
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Re: Speed control

Postby JWLaRue » Mon Jul 09, 2012 10:56 am

Ahab79 wrote:What I'm having a hard time is figuring out my "budget" for my amps. I can buy an esc with a amp limit of 20 so that meens I can get a 20 amp motor. Gotcha. But what about the rest of my servo's? I don't want to ask you guys a million small questions. So where do I get a model electronics for dummies book?

My major confusion is batteries at this point. Is it possible for me to use a battery box...pruchase at electronic stores.... and plug in some expensive home use rechargables? Just till I can get a proper cell?

In order to figure out how large a battery you need, there are principally three things that you need to determine:
    - how many motors you will be using
    - the amp draw per motor when connected to the prop shaft and in water, and
    - how long of a run time you'd like out of one battery

At that point it's simple math to figure out the size, in amp-hours, of the battery. You can basically ignore the power draw from the servos at this point, as that will be a minimal power consumer when compared to the motor(s).

The best place to get a "model for dummies book" is right here! That plus a membership in the SubCommittee so as to gain you access to the quarterly electronic magazine, which has loads of useful information. (Yea, I know....shameless plug. But it's only $15 a year. :D )

You can use one of those battery boxes as a temporary expedient to power your build-in-progress, but the type and size of battery to eventually be used needs to be based on the size of the sub, the size of the dive module (or dry space), and your desired run time.

-Jeff
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Re: Speed control

Postby Ahab79 » Mon Jul 09, 2012 11:17 pm

I had no idea that other post went through so thanks for the heads up. WOW. Looks like the more answeres I get the more questions I have. I get paid friday. Will get a membership then. I'm going to give a SHORT...SHORT! out line of what i"m doing.

1. I plan on piecing together the majority of the electronics I need first and testing them out to see what i'm doing. (including balast system)
2. Then build the interior tray and start mounting the electronics at the same time doing number 3
3. Build my hull.

As for the hull. I have a 3 step plan for that as well.

1. Build a bare bones functional hull out of pvc pipe. It will have tw exterior motors mounted left and right a few inches away from hull. These two props will provide forward motiona nd if I use one forward and one back...hopefull some control.
2. Second hull will be more traditonal with dive planes and rudder.
3. Work on those torpedo's i've been dream of firing.

And here I am. I have a transmitter. 5 servos and a NEED to build this sub. I'm going to purchase some Futaba J connectors And try to figure out what ESC to buy as well as which motors. I'd like some powerful motors if at all possible. Put it all together on my kitchen table and see if I know how to wire the dam thing.

Ahab (mark)
Well I know, I miss more than hit
With a face that was launched to sink.
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Re: Speed control

Postby salmon » Tue Jul 10, 2012 12:45 am

Here is a heads up on using your Futaba, the newer receivers might not work with it. So, if your sub is going to be smaller, you may want to consider buying a new transmitter. Some are as low as $70.
The reason I mention this is I tried what you are doing. I bought the connectors to connect the old style receiver to new style servos. Unfortunately, the receiver did not fit in the tube. Later I found out the Futaba I wanted to use was subject to interference.
If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.
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Re: Speed control

Postby Sub culture » Tue Jul 10, 2012 5:16 am

Incompatibility tends to occur with very old R/C equipment, e.g. stuff that was built in the 1970's. 1980's onwards you're generally fine. Also with older equipment, don't mix manfuacturers, as some stuff doesn't work well with each other (with the advent of computer sets that became an irrelevance).

I would forget about torpedoes for the time being.

PVC pressure hull sounds good- inexpensive but sturdy. I would advise going for a larger diameter. Here in the UK 11cm (4.5") is a popular size, and gives you room for the largest of equipment. You can also purchase inspection covers which have a screw cap and rubber seal. These are solvent welded into the pipe and with a cap on the other end- you have a watertight tube for just a few pounds. Won't look as snazzy as the purpose built items but will work just as well.

For twin motor, tank style control you will need two speed controllers and a mixer. You can purchase items like this with all the stuff you need on one board. A little more expensive but makes life easier when hooking it all up.

e.g. http://www.dimensionengineering.com/pro ... ooth2x12rc

A less expensive solution is to use a single speed controller with a servo and micro switch set-up. A little less elegant bu still extremely effective.
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Re: Speed control

Postby Ahab79 » Tue Jul 10, 2012 6:34 am

My transmitter is from 1990's. The reciever seems to work fine with the 5 servos I have. I've tested it out. If it doesn't I'll upgrade later on.

So I need a mixer? Great. Gonna spend down time at work today google what the hell that is! lol.

I think I've found the motors I want to use. I don't want a boat that is slugish and I don't need anything super fast. How many amps do u think?

And don't worry about the torpedo's....those area at least a year or two down the road.
Well I know, I miss more than hit
With a face that was launched to sink.
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Re: Speed control

Postby Ahab79 » Tue Jul 10, 2012 6:37 am

Sorry I got one more question I forgot to ask. I have about 8 brushed motors from a R/C upgradeable car from Radio shack. CanI start with two of those just to help teach me the general stuff? Do I need an ESC for those?
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With a face that was launched to sink.
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Re: Speed control

Postby Sub culture » Tue Jul 10, 2012 7:49 am

Motor size is dependent on the size and pitch of prop you run. How much current the motors draw is dependent on the motors winding, the voltage you drive them at, size of prop it is driving, and also whether any gear reduction is used.

The speed of the boat is dependent upon the shape of the boat- streamlined forms are better, and the wetted area- larger boats will need more power.

I can't give you any advice on random motors selected from your R/C car collection. They may or may not be suitable for the craft you're intending to build. You will need an ESC(s) to control the motor speed. The alternative is old fashioned micro switches or resistance based controllers, and I don't really recommend either of those- I think we should have moved on from those bad boys.
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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