Motors & Batteries

[Bernard AllenParticipant @bernardallen88612]

Hello,

I am not knew to Model Boats having built static, but I am on a learning curve with my first R/C Clyde Puffer

This is now built but has yet to sail( I will not bother you with the problems) So whilst waiting I decided to have a go with Balsa and I choose the plan in the Magazine for the Off-Shore Supply Vessel which will be named "Lilla Anne".

Every thing in the build is written down for you so there is no problem. However I shall probably wish to build another from scratch, no instructions other than what is on the plan.  My query is this:- In choosing to build a particular size how do you calculate Motor size, Battery power and diameter of the prop or do you use:-"Just about Right!!".

I would like to read anybody’s thoughts on this. Many thanks, Bernard.

[KristophParticipant @kristoph]

im looking to run 2x SPEED 600 RACE MOTOR 8,4 V (#6312 Graupner), but im at a stuck as to which speed controller(s) i should be using with these, and the best battery(s) for a good ‘run’ time… any help would be much appreciated. Thank you

[KristophParticipant @kristoph]

im looking to run 2x SPEED 600 RACE MOTOR 8,4 V (#6312 Graupner), but im at a stuck as to which speed controller(s) i should be using with these, and the best battery(s) for a good ‘run’ time… any help would be much appreciated. Also is it possible to fit the universal gearbox (1141.15 graupner) to the mentioned motors, and which ratio? 1,5:1 or 2:1, and how does this affect the power drain/output. Thank you

[Alan SmithParticipant @alansmith52971]

 Hi  Bernard

Good luck with this and let me know how you eventually make a decision. I too am thinking about this for a model I am building. So far I have been to various retailers and even within the same shop I get totally opposite opinions. I’m beginning to think I should get as many opinions as possible, choose the most popular one, but leave room in the boat to make changes if it doesn’t work.

Regards,

Alan

[JC Uknz 1Participant @jcuknz1]

Ethan … I feel that I know very little more than yourself but what I have gathered so far is that if you run the motors in series you will use less current, that if you gear down the motors likewise,  If you run a motor on a voltage below its ‘rated’ voltage you use less current.   I found quite a lot of useful info on the pamphlet which came with an Electrolize controller I bought.

My ignorance on the subject is becuase my models are of a size [40"] that will carry a 7.2Ah 12v battery which I use to power a  24volt motor salvaged out of old photocopying machines.  I can run ‘all day’ and some with my set-up using a homemade old fashioned style Bobs Board controller which merely introduces a resistance [electrical] to slow the motor at low and medium speed.  That wastes current but it doesn’t seem to matter.

My wife’s boat, scratchbuilt 500mm Puffer from MB plans of two or three decades ago, runs on little 1.2Ah batteries and a similar motor but the problem has been the propellor and having had to increase the pitch to get some speed [all it would do was a gentle ‘scale’ speed unlike all the other models wizzing around the pond]  I have learnt that you should never connect a motor directly to the propellor the way I have been doing things to date.

Quite possibly I have some misconceptions above and somebody with some knowledge could correct me .. so far when I have tried to implement what the local experts tell me things have not been very successful [with regard to the Puffer]  

When you want to know what a word means I find Wikipedia usually an easy to understand answer.

[JC Uknz 1Participant @jcuknz1]

Some of the traps I have fallen into as follows.

Propellor size detirmined by the clearance between  the shaft and the hull.

Propellor pitch [that is the angle the blades make to the shaft]  Big angle is more powerful and works at lower revs.  Fine pitch more revs.  So if you gear down you can pick a large piutched propellor.  To date I have usually bought the cheaper plastic props available in the shop, except when I wanted to build a twin screw with contra-rotating props .. it wasn’t a successful model [ WWI Medway class monitor which swamped in anything but a deadflat calm. half-inch freeboard if that]

The ‘Puffer’ has a level propshaft which is hard to keep watertight.  SWMBO insists that HER boat should not leak and packs grease into the shaft with rubber ‘O’rings both ends to reduce seepage.   better plan is to solder an oil reservoir onto the tube with a small hole into the tube and fill with oil.  better still is to have the shaft angled and long enough so that the inboard end is above the waterline.    With such a set-up you can have the propshaft connected to the motor with a gearbox* with the motor lower than the propshaft.   In most of these thoughts I am talking about scartchbuild set-ups rather than what is available in the shops.  *else a couple of pulleys and rubber band for a scale boat which I would find either in a model or an electrical shop in my town. 

 It depends on if you want to impress your freinds when they look inside your boat … to me the joy is in the making and I only run to provide a ‘show’ when my Club has an openday.  latest model is a scatchbuilt Nelson’s Navy cutter at x2 size and based on the available kit but as a sailing model.   So no motors for her, just questions about centres of sail area and hull so that she is reasonably balanced.

[Bernard AllenParticipant @bernardallen88612]

Hello  Alan,

A long delay but I have been so occupied with this scratch build that I had forgotten my contibution to the Forum.

I took my model of the ORSV to my model shop the owner just happens to be a member of the Boat Club I have joined. His recommendations which I purchased  are Battery-"Tornado RC2000" Motor "Torpedo 400 45 – 15v. My prop is 2-blade 40mm dia. The ESC is a Mtronicks 15. I set this all up and it does luck about right in the dry run stage.

As you are probably aware this model out of the Magazine comes out at approx 66cms overall length. I have added my own touches to the boat such as glazed windows and brass scuttles. My big winch is just being finished of and is made with the drum being a wine cork and my gears are from an alarm clock I bought of Ebay and pulleys are made of Dowelling. As I have some scap poly sheet, I am thinking of a crane but again I do not want to much clutter at the first attempt. Bernard.

[Bernard AllenParticipant @bernardallen88612]

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