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Author Topic: Newby motor and esc advice please  (Read 2595 times)

david w

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Newby motor and esc advice please
« on: August 30, 2013, 09:45:02 pm »

Hi all, I have just got one of these http://www.hobbyengine.com.hk/catalog/product.php?product_id=6 ( hobby engine San tropez), but it is in need of a new motor and esc, as I am into other rc stuff, cars and planes, I have radio gear and lipo batteries but have no idea what to get in terms of a motor and esc.


I gues that like cars and planes that the gearing or prop size is importand and will change on motor power / size.


I am looking for something suitable for me to play with but not so fast my little lad won't be able to use it!


Any advice please?


Thanks!



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pompebled

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Re: Newby motor and esc advice please
« Reply #1 on: August 30, 2013, 10:22:21 pm »

Hi David,

Why are you in need of a new motor and ESC if I may ask?

Is the stock propshaft and prop still present, if so what size is the prop (Ø)?

The hull is capable of handling 20 - 25 mph, but will need some driving skills to stay upright when turning at speed.
A standard 540 should work nicely, if you want more speed, go for the Graupner Speed series, as an example, the 3302:
http://www.graupner.de/en/products/5c5b118e-afc6-4ee2-b03a-c3f2e91947c1/3302/product.aspx
On 8,4V the motor will give you close to 10.000 rpm under load.

If this proves too fast for your lad, get a smaller prop to reduce the top speed, or run the boat on 2S.

You'll need an ESC that has a LVC for Lipo's; the Speed 600 I mentioned will pull up to 40A in spikes (getting out of the hole and accelerating out of a turn), so the ESC will have to be able to handle that.

Keep in mind that running on lipo's usually provides more 'oomph' and runtime, so overheating could be an issue.
As most Speed motors have an internal fan, it's important that the cooling slots at the shaft side aren't blocked, airflow through the armature is crucial.

Also, brushed motors need to be broken in by running them under water (half submerges if the motor has a ballbearing on one side) on 3V or less until the water turns dark(ish), stop and check if the brushes have taken on the curve of the commuter, if you're satisfied, dry out the motor (compressed air works well) and put a tiny(!) drop of oil on the rear bearing and you're good to go.

If you're going to use high capacity lipo's and the runtimes get really long, some form of watercooling for both motor (brushtab cooling) and ESC would be nice to keep the heat at bay.

As I'm not familiar with which ESC's are available to you, others will have to chime in.

Regards, Jan.
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david w

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Re: Newby motor and esc advice please
« Reply #2 on: August 31, 2013, 08:01:15 am »

The standard prop is with the boat but the esc is blown. I was thinking of going brushless to keep up with modern times.
I will check the prop size later, thanks.
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malcolmfrary

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Re: Newby motor and esc advice please
« Reply #3 on: August 31, 2013, 08:32:45 am »

The motor that came with it is probably near what the hull can handle, if its still in working order you can just use it.  This can be checked by just connecting the motor to the battery direct and seeing if it spins OK (something that can't be done with brushless).  If you do this with a meter connected and the prop in water, you find out what size of ESC is needed.  A couple of rules of thumb for prop/motor with direct drive - the diameter of the prop should not exceed the motor can diameter, the motor should not have less poles than the prop has blades.
The radio sounds like a "proper" one, so should have standard connections to ESC and servo.  If the motor is a standard 540, with a fairly sensible prop, an Mtronics Marine Viper 15 will do the job very adequately.  Higher capacity NiMH packs are available for longer run times - if you want to have the option of restricting power, a pack with one less cell would do the job very simply.
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pompebled

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Re: Newby motor and esc advice please
« Reply #4 on: August 31, 2013, 10:08:16 am »

Hi Malcolm,

Actually the hull can handle a lot more power, I've found video's of a Saint Tropez with a 3600Kv brushless motor installed that created a 'vapour trail' behind the boat at full speed...

I agree this has little to do with running at scale speed and turning with only the prop and the last inches of hull in the water won't go well.

@David: While there is no need to go brushless, something like this motor on 3S already exceeds the stock brushed set-up, close to 10.000 rpm on 3S:
http://www.hobbyking.com/hobbyking/store/__18229__Turnigy_D3536_9_910KV_Brushless_Outrunner_Motor.html

To get an idea what 10.000 rpm on an underwater prop does for a 43,3" hull, check out this video (turn up the volume really high):
http://www.youtube.com/watch?v=-igDcvLySEM&feature=youtu.be

Regards, Jan.
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Circlip

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Re: Newby motor and esc advice please
« Reply #5 on: August 31, 2013, 12:51:25 pm »

Quote
but not so fast my little lad won't be able to use it!

   ?????????
 
   Regards  Ian.
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pompebled

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Re: Newby motor and esc advice please
« Reply #6 on: September 01, 2013, 02:51:31 pm »

Hi David,

Regarding the motorchoice your father posted here:
http://www.modelboatmayhem.co.uk/forum/index.php/topic,44614.new.html#new
Did you read my reply #4?

Regards, Jan.
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Tug-Kenny RIP

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Re: Newby motor and esc advice please
« Reply #7 on: September 01, 2013, 07:11:18 pm »


Can you continue in the MOTORS section now please.


ken

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david w

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Re: Newby motor and esc advice please
« Reply #8 on: September 03, 2013, 10:01:18 pm »

Thanks for the replays, thinks are starting to make a bit more sense now!  :-))
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