Brushless motor help

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Associated on 13/04/2016 13:57:02:

Would this be a more suitable motor and esc ?

Fusion 2815/24 1100kv outrunner and hawk bl 30a speed controller

That sounds a little small to me – I'd go for a 2822 or a 2866. The 2815 has a max output of about 40W/5A? I think you should be looking for something which can do 8-10A, perhaps 100W max. Depends how sprightly you want your boat, of course, and what voltage you want to run at.

In my experience, brushless motors can take as much power as you can put into them, until they melt. The reason for picking a bigger one is not so much to take advantage of the greater power, but rather to be able to run it in that part of its envelope where it's quite cool and needs no extra ventilation….

[AssociatedParticipant @associated]

Want it quite nippy but mainly use with throttle between half and 3/4 and looking lipo 2 or 3 cell.

Matt

[AssociatedParticipant @associated]

Think I'm starting to confuse myself here found there is rpm kv and kv of the motor itself , which one am I looking for to be around 1000?

[Dave MilbournParticipant @davemilbourn48782]

Every picture tells a story… In this case there's a video, too **LINK** (The music's not my choice but pleasant enough).

Prop used is a Prop Shop 3-blade 1315 LH General Scale bronze one. LiPo is 3S 2200maH but I could probably get away with a 2S with this 1050kv motor because the model is built very light – it's just over 1.1kg fully loaded.

Even after ten minutes thrashing round the pond for the video, mainly at full throttle, neither motor nor ESC were even slightly warm.There's no water cooling in there, BTW. I subscribe to the Malcolm Frary Theory i e. don't put unnecessary holes in your hull; they'll only leak.

Incidentally I set Reverse up on the transmitter to be 50% of full ahead speed. Swamping the transom is another good way to fill your model with water.

DM

Edited By Dave Milbourn on 13/04/2016 15:15:23

[AssociatedParticipant @associated]

Thanks Dave sort of speed I want . Is the higher kv rating more power = more sped and on a smaller boat would make it to lively ?

If was a bigger boat would you use lower kv for more torque or more power ?

[Dodgy Geezer 1Participant @dodgygeezer1]

KV is ENTIRELY about revs per volt. Though low KV tends to mean more torque, that's only with everything else equal. I tend to look at Wattage if I'm interested in power. Typically, very small low power motors have a high KV (giving them amazing power for their size, but not a huge amount for a decent sized boat. Bigger boats mean bigger props to shift more water, which tend to need to turn slower…

KV data is possibly more important for aircraft? And racing boats that want very high revs. At the sporting end you probably want around KV1000. I have motors KV900 – KV1700..

If Dave's motor/esc wasn't warm after a good full-throttle run – that's the way you want it. If things start getting hot you can certainly go for water cooling, but you are starting to push the limits and moving into the racing world, where things get complicated and the threat of fire is ever-present…

Edited By Dodgy Geezer on 13/04/2016 16:28:24

[AssociatedParticipant @associated]

Ahhhh starting to make sense , so higher wattage means more speed correct ?

[AssociatedParticipant @associated]

If put a different way what wattage should I be looking for ? Did someone say 500w ?

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Associated on 13/04/2016 21:32:31:

If put a different way what wattage should I be looking for ? Did someone say 500w ?

 

The first motor you picked could take 600W. We thought that was a little high – I suggested a 500W one. (Note that this does NOT mean the motors HAVE to run at that – just that they can. Running at full whack would almost certainly require good cooling.)

Dave pointed out that his boat was quite sparkly with a motor around 100W, and showed you a video. You then came back suggesting a motor at about 40W. You could probably get good performance of a 40W motor, but you would be using it at the top of it's capabilities, and would need to cool it extensively.

100W sounds fine. 200W would be ok – it would just run cooler and cost a bit more. Going higher would just cost more money for no obvious benefit. Going much lower would either mean running a slower boat or adding a cooling system.

Note that the above data is a guess not an informed prediction. And that Ashley's point about different props still applies – getting the right one can make a huge difference, easily comparable to having a different motor… and really the driving issue is what kind of battery will you use – what voltage and what amp delivery…?

 

As an example – I quite like this supplier – how about this at 150W:

http://rclife.co.uk/Brushless-Motors/Brushless-Outrunner-Motors/DYS-D2826-13-1000KV-G-Power-Series-Brushless-Outrunner-Motor?sort=rating&order=DESC&limit=100

 

 

 

Edited By Dodgy Geezer on 13/04/2016 23:07:33

[AssociatedParticipant @associated]

Yes that's it , 600w compared to 40w is a big difference, I expect 600w be fine for a boat around 35" but 26" a bit ott.

Around 100 – 200 should be fine . There so much to pick up on the subject

[Dave MilbournParticipant @davemilbourn48782]

Sooner or later you're going to have to dip your toe into the water, m'duck. You'll only learn more now by trying things out for yourself.

Open your wallet and recite the following: "I'll have one of those, please".

DM

[AssociatedParticipant @associated]

Ha ha ! Yes Dave I have just done that , ordered a motor and battery from hobbyking motor 1080 and 146w , battery 2.2a 30c .

Motors are cheap enough to buy to play about and see what different wattages do . As I understand the higher kv mean quicker they spin correct ?

[Dave MilbournParticipant @davemilbourn48782]

Given the same voltage yes. Speed is a product of the voltage and the kv.

DM

[Dave MilbournParticipant @davemilbourn48782]

If you've not bought from that supplier before then take great care that you order from their UK warehouse. If the goods come from outside the EU then you run the risk of being stuck not only with an extra 20% VAT but a hefty £8 handling charge from the Post Office. That could well negate any saving you might otherwise have made. The goods can also take a long time to get here from China!

Ask me how I found this out………………:0(

DM

[AssociatedParticipant @associated]

Ah I did not know that it's from international warehouse I don't mind taking a couple of weeks as got to build the hull 1st . Anyway cancelling order ?

[Dave MilbournParticipant @davemilbourn48782]

I've no idea, but I very much doubt it. Bang your head here **LINK**

Dave M

[AssociatedParticipant @associated]

I've sorted it can get a refund before goes to be packed at warehouse but only refunds into the HK loyalty account . So clicked onto uk warehouse and re ordered similar items…. No head banging needed just yet lol !

[Paul TParticipant @pault84577]

Hi Matt

How is the Twinkler build coming on?

Paul

[AssociatedParticipant @associated]

Had a bit of a break other things came priority . But yes just finishing off painting etc , even daughter taken a interest with it but keeping an eye as she only 7 and has a habit to break things .

[Paul TParticipant @pault84577]

The build is looking very business like and judging from your photos you haven't encountered many problems.

Paul

[AssociatedParticipant @associated]

Not too many issues just the filler didn't try at one point

[Paul TParticipant @pault84577]

We have all suffered from non setting filler at some point, its one of those times when you grit your teeth, kick the cat (not the dog as they bite back) and start again.

Disclaimer: The views expressed in this posting do not represent the opinion of the site owner, no cats were injured during the making of this post.

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