Brushless recommendations

[Martin Field 1Participant @martinfield1]

Hi all,

I have three similar-ish speedboats on the go and would like to use brushless motors in them to keep their performances similar. I don't want to spend a fortune on these. I know they can be had for a tenner or so with about 17 quid for ESCs, but all I can find are aeroplane motors. Hobbyking have a heat sink for a BL 2815 motor, but I can't find the motor!

I have an inrunner for a CNC ally outboard, which is nice, but can't find that either and I only bought it recently!

The boats are all around 26" by 10 beam, single stepper vintage monohulls. Prop recommendations would be good too. I have always made static models and all this new tech. has me scratching my head. Alternatively, of course, if cheap and cheerful 540s will do me, I'll go for those.

Cheers,

Martin

[Martin Field 1Participant @martinfield1]

[Colin BishopModerator @colinbishop34627]

No doubt Mr Milbourn will be along with some recommendations. My SLEC Fairey Huntsman kit uses his recommended Turnigy 2830/11 1000Kv motor on a 11.1v Lipo battery and it goes rather faster than I would like even with the cheapie 2 blade nylon 35mm prop supplied. No heat sink or water cooling needed.

**LINK**

But you may be able to buy it elsewhere.

Colin

[Martin Field 1Participant @martinfield1]

That's just what I was after, Colin. Cheap and good for a heavier build (which mine tend to be). And a nice cheap 30A ESC will go too.

Many thanks,

Martin

[Colin BishopModerator @colinbishop34627]

I was quite amazed by the amount of power it puts out.

Colin

[Martin Field 1Participant @martinfield1]

That's really all I need as these are strictly for fun, on my own (no clubs here, but nearby river). I'd like them to go reasonably well, but not like a mad duck on acid. They are scale models after all.

Many thanks for your answer, Colin. Makes a lot of sense. It was all the Kv options that had me confused.

Cheers,

Martin

[Dave MilbournParticipant @davemilbourn48782]

My choice of prop is a 1315 [that's 1.3" dia x 1.5" pitch] General Scale pattern 3-blade job from Protean Design. Current price in the UK is £14 incl P&P. Excellent price for a thing of such beauty. Simon Higgins, who is Protean Design, has a page on Facebook. **LINK**

Now – heads down for an incoming Harry "The Larrikin" Smith, who is a notable proponent of mad ducks on acid.

Dave M

[Martin Field 1Participant @martinfield1]

Hmm, I have such a beast, Dave. Well a 3 bladed brass of 32mm diameter, so close if not such a thing of beauty, although only yesterday I turned the knobbliness off the boss into a more pleasing bullet shape. It has been around my bits collection for decades! 4BA, bless it. Fortunately I have 4BA shafts too.

Thanks for the info.

I seem to recall a Mr. Smith liking his mad ducks.

I have a 2212 which I will give a go in one of the boats just in case, as I have 2 of them and they're still available. May be too small, but you never know until you try it.

Although I do like the Turnigy suggestion earlier as it's a make I know is popular.

Cheers,

Martin

[Markku HokkanenParticipant @markkuhokkanen40095]

93 cm LOA, displacement pleasure craft, scale 1:9,5. Original is powered with 38 hp inboard petrol engine.
HexTronik DT700 brushless outrunner 700 kv.
HK X-Car 120A rock-crawler ESC. Default settings but minimum brakes, no fan, soft start.
50 mm brass Raboesch 162-22 or 156-10 3-blader.
2 cell 4200 Lipo.

Tested in water:

1000 rpm: 4 watts, 0,4 amps.
1500 rpm: 7 watts, 0,8 amps.
2000 rpm: 12 watts, 1,6 amps.
2500 rpm scale top speed: 19 watts, 2,4 amps.
3000 rpm emergency speed: 33 watts, 4,5 amps
4000 rpm warp speed: 70 watts, 9 amps.

Need to re-wind the motor to smaller kv, say 500.

-Markku-

[Martin Field 1Participant @martinfield1]

Marrku,

that's very useful info. Many thanks. I am just back from my local model shop, where I bought a 3S Overlander battery pack and connectors, as my motor has non standard small bullets and my 60Amp ESC no connectors at all.

I have built a mount for the outrunner in aluminium to help with cooling and am about to make a coupling and shaft.

This is all very new to me. I have never actually made a working model before, always having done statics.

I also bought some lightweight glass cloth as the balsa top cover for the Darby One design is in balsa to save weight, but it marks and digs too easily. I also just received (finally) an answer from the Lowestoft and Oulton Broad Motor Boat Club with some more pictures from their archives which clearly show, for the first time that the top cover fixed portions are indeed a la airframe…..stringers and fabric, so a single sheet of epoxied glass cloth over some very shallow dummy stringers will do nicely to add some strength to the structure. I will also make the removable engine cover in aluminium and glue that over the balsa one. The aluminium will go well with the blue of the cover and still be lightweight.

All we have to do then is hope that the little brushless can handle the slightly heavy single stepper.

Cheers,

Martin

[Markku HokkanenParticipant @markkuhokkanen40095]

When considering a direct drive brushless setup to a model scale ship, a few things is needed to understand about the motor and ESC specs:

Max current of the ESC is better to choose at least several times bigger than the max current of the motor under load. No need to save here: 120amp esc doesn’t cost that much more than a 40A esc. Better be safe than sorry. That plenty extra gives safety margin for weeds and other obstacles hitting the prop, and you can remove the whining fan from the ESC heatsink.

The ESC type: better choose an ESC that has a ”Rock Crawler” mode ( forward/instant reverse, no brake) that is optimised for low throttle driving. Boat esc’s are usually optimised for full blast driving and has poor low speed throttling behaviour.

Outrunner motor specs: Voltage range, kv-value and outer diameter are the key specs here. The battery voltage and motor kv mainly defines the rpm the motor will run, and the power the motor must deliver to turn that prop at those rpm.

The diameter of the motor should be close the diameter of the prop. No more than 10 mm less than the prop diameter if the motor is of top quality one. Diameter gives the motor the ability to deliver enough torque the motor needs to stay in sync with the esc when running under full load. Smaller diameter motors start lagging under load and that means that more of the input energy turns to heat. If the motor falls out of sync under load ( loud screeching noise ) the motor stalls, can not turn the prop and deliver any power, all input power turns into heat, motor or ESC may burn.

My homebrew formula in choosing a direct drive outrunner setup to a scale displacement hull:

1. Define the target scale speed in meters per minute

2. Divide those meters with the pitch of the propeller => theoretical rpm needed to advance that distance in one minute

3. Add 20 % for prop slip, motor losses etc => calculated rpm

4. Divide that calculated rpm with the voltage of the motor battery under load = kv target

5. Choose an outrunner that has about the same kv as target, and outer diameter near the same as the prop diameter. Max continuous power must be about 2-3x the max operational power of the setup to get a motor that operates at the best efficiency.

-Markku-

[Hadria Guy 1Participant @hadriaguy1]

Hi….with respect to suggestions, I've generally loved Castle. Be that as it may, everything relies upon what batteries you need to run. You can get up to 70 mph reasonably effectively on 2 – 3s lipos yet you'll need to truly watch temps particularly on more modest engines.

A manor sidewinder 4 with a 3800kv is a typical combo and can approach 3s Lipo. In spite of the fact that you'll need to watch you temps with that 1410-3800 engine.

In the event that you need they likewise make a combo with the sidewinder 4 and a 1415-2400kv engine. The engine is alittle greater and can deal with more force and equipping, temps will be better. The 2400 is appraised to 4s lips yet the sidewinder will just do 3s.

[Chris FellowsParticipant @chrisfellows72943]

I think you're a bit late to the party as regards this thread!

Chris

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