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Author Topic: Brushless outrunner suggestions for big tugboat  (Read 4890 times)

desktoprover

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Brushless outrunner suggestions for big tugboat
« on: March 24, 2017, 12:34:10 AM »

Hello everyone,
I have always been running all of my tugboats with geared brushed motors.  They have always been working nicely.  My latest model is a large 35lbs tugboat and I feel like it could be a little more powerful.  Right now it is powered by two 540 motors geared 6:1 on 6 volts.  I would like to replace them with a direct drive brushless outrunner motor.  The props are 85mm four blades.  These are quite large.  Right now the rpm at the props is about 1250.  Around 2000-2500rpm would be my new target.  So I was thinking about two Turnigy Aerodrive 5045 450kv brusless motors direct drive on 6 volts.  Does that sound like a good choice?  Maybe too powerful...or not enough?  Thanks for your help!
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Martin [Admin]

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Re: Brushless outrunner suggestions for big tugboat
« Reply #1 on: March 24, 2017, 08:37:53 AM »


Hmmm,  very little posted expertise in the area is there!

 Not a cheap motor but I would say that's say that's a good starting point......   6 x 450 = 2,700 ( + throttle - efficiencies )
 

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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #2 on: March 25, 2017, 01:02:27 PM »

Thanks for your reply Martin.  Brushless motors are not very popular in big scale boats yet!  I want to give it a try!
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Martin [Admin]

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Re: Brushless outrunner suggestions for big tugboat
« Reply #3 on: March 25, 2017, 04:42:24 PM »

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Umi_Ryuzuki

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Re: Brushless outrunner suggestions for big tugboat
« Reply #4 on: March 25, 2017, 05:25:09 PM »

I seem to recall that Leen was using Turnigy 480kv outrunner in  his Maersk Topper.
So I think you have the correct range.

 :-)

desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #5 on: March 25, 2017, 05:33:29 PM »

Thanks for the link Martin.  I looked at it yesterday from the link you posted on Facebook!


Thanks Umi.  The difference is that he runs it on 12 volts with a 2:1 reduction.  My goal is to go direct drive at 6 volts  :-)
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cos918

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Re: Brushless outrunner suggestions for big tugboat
« Reply #6 on: March 25, 2017, 07:16:47 PM »

Hello everyone,
I have always been running all of my tugboats with geared brushed motors.  They have always been working nicely.  My latest model is a large 35lbs tugboat and I feel like it could be a little more powerful.  Right now it is powered by two 540 motors geared 6:1 on 6 volts.  I would like to replace them with a direct drive brushless outrunner motor.  The props are 85mm four blades.  These are quite large.  Right now the rpm at the props is about 1250.  Around 2000-2500rpm would be my new target.  So I was thinking about two Turnigy Aerodrive 5045 450kv brusless motors direct drive on 6 volts.  Does that sound like a good choice?  Maybe too powerful...or not enough?  Thanks for your help!


If it is this motor on hobby king you can not run it on 6 v . Speck say 5s to 7s which is 18.5 v to 25.9 v . 5s it is 450 X 18.5 = 8325 rpm . 7s it is 450 x 25.9v = 11655 rpm. This is to high for 85 mm prop .


John


https://hobbyking.com/en_us/turnigy-aerodrive-sk3-5045-450kv-brushless-outrunner-motor.html
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cos918

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Re: Brushless outrunner suggestions for big tugboat
« Reply #7 on: March 25, 2017, 07:20:57 PM »

I would think it is going to be hard to find a motor suitable to turn an 85mm prop on direct drive .A prop that big on direct drive will cause big current pull and that mean higher cost . A option would be keep the 6:1 reduction which means you can run motors with higher KV or voltage limits and lower watts


John
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unbuiltnautilus

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Re: Brushless outrunner suggestions for big tugboat
« Reply #8 on: March 25, 2017, 09:18:30 PM »

I am also looking into scale use for brushless motors. You can certainly run brushless motors below their recommended voltage, I have been trying out brushless in a Perkasa. Not just suitable fast scale options, but also low end, low voltage uses. I have comfortably run a 3s/4s specified motor down at 6v, or just shy of half its recommended voltage input, with no noticeable issues. This was with a smallish diameter 36mm prop.
 There may be issues as the load increases with bigger props ( A fellow Mayhemmer on here has tried brushless, down and dirty, in a rock crawler, but found the low end torque was very poor, at low voltages, through the reduction drive compared to traditional brushed motors. ), but I found the current drain down below motor specifications, was very low.
 I am looking for that pot of gold option, lower current drain than either geared or blower type motors. I am currently looking at the 'pancake' style brushless used by bigger quadcopters as a possible option. Big diameter can should equal flywheel like torque effects. But my first job will be to over prop and under volt the Perkasa ,hook up a watt meter and see what we shall see.
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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #9 on: March 25, 2017, 11:04:03 PM »

I have seen someone run a NTM Prop Drive 42-58 500kv in a Carol Moran XXL on 6 volts.  The prop is around 88mm.  He says that he has to lower the end points of the esc to about 75% since it is too powerful at 100%.  I feel like a similar set-up should work nicely in my tug.  Even the brushed set-up for large tug like mine are quite limited!
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unbuiltnautilus

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Re: Brushless outrunner suggestions for big tugboat
« Reply #10 on: March 26, 2017, 07:53:36 AM »

I have found with brushless motors that there are many theories, but not many people actually trying these theories out. Brushless is aimed fair and square at hauling aircraft and quads and helis round the sky, which is why their specs sometimes seem 'out of reach' for model boat use. Too high a voltage, revs too high etc. However these specs refer to the sweet spots for these motors, at which they give their maximum and best performance. We don't need that, we need their performance way down the graph, where flyers never lurk! The only way to find out what we need is trial and error, so that is what I am hoping to do. I will get a U-Boat fitted with a brushless set up, AND increase it's run time over pretty efficient Pittman motors already fitted. Well that is the plan anyway O0
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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #11 on: March 26, 2017, 02:01:27 PM »

I have found with brushless motors that there are many theories, but not many people actually trying these theories out. Brushless is aimed fair and square at hauling aircraft and quads and helis round the sky, which is why their specs sometimes seem 'out of reach' for model boat use. Too high a voltage, revs too high etc. However these specs refer to the sweet spots for these motors, at which they give their maximum and best performance. We don't need that, we need their performance way down the graph, where flyers never lurk! The only way to find out what we need is trial and error, so that is what I am hoping to do. I will get a U-Boat fitted with a brushless set up, AND increase it's run time over pretty efficient Pittman motors already fitted. Well that is the plan anyway O0


Great!  Do you have a brushless motor replacement in mind for the Pittman motors?
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unbuiltnautilus

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Re: Brushless outrunner suggestions for big tugboat
« Reply #12 on: March 26, 2017, 08:09:43 PM »


Great!  Do you have a brushless motor replacement in mind for the Pittman motors?


Nope.




But hope springs eternal :}
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canabus

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Re: Brushless outrunner suggestions for big tugboat
« Reply #13 on: March 27, 2017, 07:31:51 AM »

Hi
You may have a bit of a mix up with your voltages as per Lipo batteries.
1s=3.7volts, 2s=7.4volts, 3s=11.1volts and 4s=14.8 volts.
The 3s batteries do charge up to 12.6 volts and the 4s to 16.5 volts.
You cannot run two brushless motors on one ESC, but, you can have one battery.
As for direct drive you would be better staying with the geared setup and looking for 35mm brushless motors.
A few I looked on the Hobbyking site are NTM Prop Series 35-42A 1250kv(500watts on 11.1 volts(3S) and 600watts on 14.8 volts(4s) or the Turnigy Aerodrive SK3-3542 1250kv(755watts on 14.8 volts(4s).
The 1250kv on 3S battery gives rpm of 13875 at 11.1 volts and as for power these brushless are about 5 -7 times more powerful.

If I am right and I maybe totally wrong with the gear setup this times the power by your reduction (6 times).

So you would end up with a very powerful tug!!!!
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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #14 on: March 28, 2017, 02:22:22 AM »

Thanks for your reply.  I'm not using lipos, I'm using a 6 volts sealed battery.  Do you have a suggestion for a brushless motor gearboxe?  Something like 2:1 would be nice but they seem hard to find plus the motor shaft diameter is 5mm on most brushless motors.  Not easy to find a 5mm pinion gear.


Thanks
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derekwarner

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Re: Brushless outrunner suggestions for big tugboat
« Reply #15 on: March 28, 2017, 02:48:31 AM »

IKB/Alex is using 5 mm shaft diameter metal pinions in his 1/16 Trent Refurb O0........on this page....... Derek
__________________________________________________________________________

extract from his WEB thread..........

•The gears I am using are the same as I am using in my jet drive boat, which at present is producing 2083W, running with a little bit of shaft grease, these hardened steel gears only suffered minor polishing to the mating surfaces: http://www.ebay.co.uk/itm/162149776688?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
•The tooth width is nice and wide at 8mm, the Overlander motors I am using are very good with next to no end float and very good concentric running
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gra2

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Re: Brushless outrunner suggestions for big tugboat
« Reply #16 on: March 29, 2017, 09:53:51 AM »

Hi my experience using a brushless motor with a sealed battery was a failure.
As soon as I pushed throttle forward for more power motors cut out.
Switched to lipos no problem.

Gra2
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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #17 on: March 29, 2017, 12:17:21 PM »

Hi my experience using a brushless motor with a sealed battery was a failure.
As soon as I pushed throttle forward for more power motors cut out.
Switched to lipos no problem.

Gra2


Thanks everyone.


I believe this is linked to the esc cut off voltage.  It is supposedly programmable.
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steamboat66

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Re: Brushless outrunner suggestions for big tugboat
« Reply #18 on: March 29, 2017, 08:37:06 PM »

smaller SLA batteries may suffer from severe voltage drop when high currents are drawn from them, hence the cut out. LiPos don't suffer any where near as much. brushless motors can draw huge currents when powered up. i would only use LiPos with brushless.
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tsenecal

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Re: Brushless outrunner suggestions for big tugboat
« Reply #19 on: March 29, 2017, 09:29:41 PM »


If it is this motor on hobby king you can not run it on 6 v . Speck say 5s to 7s which is 18.5 v to 25.9 v . 5s it is 450 X 18.5 = 8325 rpm . 7s it is 450 x 25.9v = 11655 rpm. This is to high for 85 mm prop .


John


speck is irrelevant.  like any other electric motor, the only real issue you need to consider is if you are trying to run a motor designed for 12v on 24v.   a brushless motor with a spec indicating 5s to 7s will run just fine on 2s.    450 x 7.4 = 3330rpm...   i still feel that 3330rpm is a bit high for an 85mm prop, i would think for a tugboat running a 85mm prop, half that would be a good top speed.


as to SLA batteries, yes, they can not handle more than 1s load, meaning if your motor/esc combo draws 3 amps at max load, then you need an SLA battery rated at greater than 3ah.


how do i know this?  i have been running a Dumas Mr. Darby (48" long tugboat) with twin brushless outrunners rated at 600kv on a 2:1 belt drive, with 6v 38ah SLAs, driving large 3.5" brass four bladed props for several years now.   the reason i went with 38ah SLAs was due to weight.  the two batteries weigh 40lbs, and will run the boat for more than 30 hours before needing to be recharged.
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unbuiltnautilus

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Re: Brushless outrunner suggestions for big tugboat
« Reply #20 on: March 29, 2017, 09:55:47 PM »

Now THAT is what I call useful information. Your motors must be running at pretty low amps for that sort of run time.
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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #21 on: March 29, 2017, 10:50:24 PM »


speck is irrelevant.  like any other electric motor, the only real issue you need to consider is if you are trying to run a motor designed for 12v on 24v.   a brushless motor with a spec indicating 5s to 7s will run just fine on 2s.    450 x 7.4 = 3330rpm...   i still feel that 3330rpm is a bit high for an 85mm prop, i would think for a tugboat running a 85mm prop, half that would be a good top speed.


as to SLA batteries, yes, they can not handle more than 1s load, meaning if your motor/esc combo draws 3 amps at max load, then you need an SLA battery rated at greater than 3ah.


how do i know this?  i have been running a Dumas Mr. Darby (48" long tugboat) with twin brushless outrunners rated at 600kv on a 2:1 belt drive, with 6v 38ah SLAs, driving large 3.5" brass four bladed props for several years now.   the reason i went with 38ah SLAs was due to weight.  the two batteries weigh 40lbs, and will run the boat for more than 30 hours before needing to be recharged.


Well said.  I'm using a 6v 24ah SLA battery, so lots of power available.  Boats are not pulling as much amps as airplane do.  I feel like somewhere between 1800-2500 rpm would be perfect.


What motor are you using on your Darby?
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tsenecal

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Re: Brushless outrunner suggestions for big tugboat
« Reply #22 on: March 29, 2017, 11:21:27 PM »

Now THAT is what I call useful information. Your motors must be running at pretty low amps for that sort of run time.


so low that they don't register on an eagletree data-logger until i am at about 60% of full throttle.  each motor at full throttle pulls less than 2 amps.
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tsenecal

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Re: Brushless outrunner suggestions for big tugboat
« Reply #23 on: March 29, 2017, 11:26:38 PM »


Well said.  I'm using a 6v 24ah SLA battery, so lots of power available.  Boats are not pulling as much amps as airplane do.  I feel like somewhere between 1800-2500 rpm would be perfect.


What motor are you using on your Darby?


a brand that is no longer available in the USA, they were labelled as a "60" size IC equivalent - 50mm diameter by 80mm length, 600kvm.  about the same physical size as the original dumas 12v pittman motors.  if i could do it over again, at the time i bought them, i had a choice of 600kvm or 400kvm, i bought the 600, should have bought the 400


depending on the pitch of your 85mm propellers, 1400 to 1800 rpm on the prop is what i would aim for.
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desktoprover

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Re: Brushless outrunner suggestions for big tugboat
« Reply #24 on: March 30, 2017, 01:45:33 AM »


a brand that is no longer available in the USA, they were labelled as a "60" size IC equivalent - 50mm diameter by 80mm length, 600kvm.  about the same physical size as the original dumas 12v pittman motors.  if i could do it over again, at the time i bought them, i had a choice of 600kvm or 400kvm, i bought the 600, should have bought the 400


depending on the pitch of your 85mm propellers, 1400 to 1800 rpm on the prop is what i would aim for.


Thanks for the information.  I'm glad to have someone who tested brushless in a tugboat!


50-80 that's big!  Why would you lower the kv?  1800rpm looks very reasonable to me.  My props have quite a lot of pitch.  With my current brushed set-up I have around 1250rpm.  I tried the the same motors on 12v (2500 rpm) and is was wayyyy overpowered.  The motors overheated.  My goal is to have a little more power with the brushless.  I found a Aerodrive SK3 320kv at HobbyKing.  I feel like it would do the job at 1920rpm.

There it is:

http://sylvainrioux.zenfolio.com/img/s6/v138/p1324013757-4.jpg
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