HOW TO CHOOSE a MOTOR BASED on the MODEL WE WANT to BUILD

HI,

I intended to build , for example one of the TRAFALGAT , ASTUTE , KILO , VICTOR , AKULA , OSCAR , Los Angeles class sub ,or any other sub scale betwen 1/72 thru 1/96 ,

1) how do I choose the motor? ;
2) direct drive PRO/CONT ;
3) if geared motor WAY and at what ratio ;
4) what is/more/impotant : Rotation Nr.....Torque.....voltage.....current ;
5) or any other ? ;

or is necesary and IMPORTANT WHAT TYPE of Sub is going to be build and dossen't matter the motor?!


PLEASE tell more in details of Why you choose for a particular version ..... what reason are observable ...... even if they are related to the efficiency versus financial

THANK YOU

Direct drive brushless motors work well and are very quiet.
In other words do not create receiver interference.

http://www.westbourne-model.co.uk/acatalog/Roxxy_Bl_Outrunner_4250_07_Robbe_Roxxy_Bl_Outrunner_4250_07_pt_no_4781-1859-ext.html

I would still tend to favour good quality (many poles, many ball races!) brushed motors with a reduction gear (toothed belts are best - efficient and quiet.) The range of MFA geared motors are generally a good choice too.

Brushless are fantastic motors but still seem to be best for high speed, performance craft. Brushless still seem to be rather high revving for our purposes. (High revs can be unkind to shaft seals, for example.)

It is very difficult to be to hard and fast in motor selection because of scale effects for models. A true scale speed looks rather slow and boring in a model.

Prop selection is also critical. Some people have tried to make this more scientific but it is still subject to trial and error. My first test in a scratch built model is: Does the model go at reasonable speed? Does the rudder turn it?

So no easy answers, I'm afraid Marius.

David

Agreed, Marius...for most of my bigger boats (now out of bounds, my doctor tells me) I normally start off with either a high torque, low drain, 540/550 sized motor, or a geared 380/385 type, and run it with a large (45-60mm scale prop).

For my smaller boats, such as the Seawolf, Kilo, my submersibles, etc...I'll start off with a 380/385 size motor with a smaller prop, around 30-35mm diameter. As David rightly says, it's largely a matter of trial and error...for example..my first Kilo had a 380 motor on 7.2v with a 30mm scale prop...it was practically uncontrollable, far too much power. The second Kilo had a 280 size motor on 6v, with a scale 20mm prop...that was much better, with a nice scale speed.

The one I'm building now, a 16" submersible, is having a direct drive 385 motor, a 30mm two blade prop in a Kort nozzle, and will be using a 11.1v LiPo battery. Hopefully, that will give me ample power to dive, then I can back the power off when it's submerged.

As long as you have enough power to submerge and stay submerged, and with a little extra in hand should an emergency crash dive be required, that's all you need.

Trial and error...those are the keywords.


Richard

I think we are getting a rule of thumb here.

If it just about fits in the car and you can just about carry it then 540/550 brushed.

It it fits in the car and you can carry it quite easily then a 380/385 brushed!

I am joking a little but there is something in that. You can characterise brushed motors. That is still one of the difficulties with brushless motors - there are so many different types.

David

The saga of the brushless motor is something I compare to black magic, to try and find a brushless motor to compare to say...a 380 brushed motor is a nightmare. Check out the HobbyKing lists, there's dozens of brushless motors listed...to choose the one that's suitable for your boat is really difficult. I was going to fit a brushless motor to this boat, but I just couldn't choose which one I needed, so I stuck with what I know, the good old 385. Whether or not I'm right we won't know until the boat hits the water for the first time...

Alexander Engel Models is a great place to sort out the "Black Magic".
http://www.engel-modellbau.eu/catalog/product_info.php?cPath=108_217&products_id=2426

They are using them in their RC submarines with great success.
Mr. Engel will answer any questions about motor sizing and ESC pairing.

Thank you all for answers,

Now I have more opinions to study .... but I saw no comment on the report quality price and by that I mean : what is the most common method of choosing a motor according the model.
- Brushless motors are in my opinion are designed to operate at high speeds , and propeller diameters up to 40mm not to mention the fact that BEC require speed controllers and more lipo batteries everyone uses them for power ... and in that I saw require cooling , and on the submarine is more difficult to achieve this ..... not to bring up their price is not low at all ......
-  brushed motors are designed for a low speeds but greater torque when stopped by any obstacle but this implies a higher consumption power ...... accept any barriers to any type , and any the speed controller ....not to mention you can find them enyware.....
That's what I remember from what I read so far ..... if there are other opinions I'd like to hear.

MARIUS

Brushless motors are available with lower RPMs per volt, now.
The ESCs are programmable, as well. ESCs can now be programmed for your exact battery type and number, soft motor speed starts, battery voltage level safety shutoff, as well as governing speeds.
A submarine does not overheat the BL motor, especially at the lower speeds and loads. Remember, the motor is surrounded by water.
The BL motors are more expensive than brushed motors but is light years ahead in performance, power and efficiency.
There is no static from brushes that causes interference with the receiver. They even can run submerged in water and there is no need for a gear reduction drive system. There is not very much more expense when you consider that the gear reduction system is not needed.
I have used brushed motors for years. I'm approaching 64 years of age and we can all complain about progress and the status quo but I will accept progress if it helps my submarine perform much better.
It is the same with batteries. Over twenty years ago I was advocating using nickel metal hydride batteries that were being used in my cell phone but everyone said that it would cause an explosion. Look at how everyone started using those.
I used them with great success. I advocated using lithium batteries over ten years ago in submarines. Now many submariners are starting to use them. The newer motor and battery technologies are here to stay, prices are becoming affordable and components are easier to understand how to combine.

If we decide to choose a brushless motor ,what motor we choose according to supply voltage that we have it on board ... what charecteritics should wo look for and what speed controller looking for him?

You may want to post here your submarine WTC, submarine and prop dimensions. You can also send these to Alexander Engel and they can provide you with exact component sizing and model numbers. They were very helpful to me when I emailed them. They do take a few days to reply by email.

info@engel-modellbau.de

TAHNK YOU very much for the info.

Unfortunately I have a bad experience with my fisrt sub.
I'm ashamed to say but in 2010 I spent all the money raised in many years 2500EURO!!! , for 212A type sub from Engell .... a complex product that I have not succeded yet to make them fuctional , and is lying for 2 years on a closet gathering dust!!! ..... so sad experience bakground with it, now I'm take it easy to study, and gather information. study how to approach the problem to not repeat that expensive mistake again .... mistake was entirely mine for I thought that if it is a ready to assemble product I manage to make it faster fuctional to enjoy my investment..... it was not so , for I could not make them understand each electronic device, my lack of knowledge in this area!.

So that's my story
hope my story will be helpful to everyone who wants to enter in this beautiful area

Wow!
You really have a large investment in your model.
You may as well build it nice.
That same model now comes with a Robbe brushless motor and programmable ESC option.

If I could find some one willing to buy it , tomorrow I would give him as it is now!....than sitting on the closet useless.

You just need to build one piece at a time.
Try not to scale the mountain in one climb.
You need to make many small climbs to finish the build.