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Author Topic: Another brushless bowthruster question  (Read 3126 times)

Capitaine LaGaffe

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Another brushless bowthruster question
« on: August 08, 2012, 07:56:07 PM »

Greetings,

Does anyone know of any brushless motors that you can replace the SPEED 400 in the common commercial smaller bowthrusters with? Why? Well, why not; I like to stick to one type of motor (nuts, I know); and a 7.2V SPEED 400 might not like being run on 10V (3S LiFe) or 13V or more (4S or 5S, if I can find a suitable ESC that can handle that) though I used to run 6V SPEED 400 on 8 NiMH/NiCd cells (that is, about 8V at 10A) in planes once upon a time (not very efficient). [I really want to avoid having a separate ack for the bowthruster.]

Or any other way to end up with a smallish brushless bowthruster?

tia/tm
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Tug-Kenny

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Re: Another brushless bowthruster question
« Reply #1 on: August 08, 2012, 07:59:31 PM »


Not really heard of a brushless bow thruster before, especially smaller ones.  Would it not run too fast and cause turbulence ?

I'd be interested in the response here.

Cheers

ken
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Stavros

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Re: Another brushless bowthruster question
« Reply #2 on: August 08, 2012, 08:20:29 PM »

PLEASE PLEASE PLEASE dont do it you seriously DO NOT want to go the brushless Motor route on a Bowthruster they are far to POWERFUL to be used on a bowthruster,why not get an electronic device to reduce the voltage to the thruster then you DO NOT have to use a brushless motor,if you are intent on using one then you will need to know what the max rpm is of the 400 then find a suitable sized brushless motor of the same size but YOU will have to calculate how many revs per volt off that particular motor.EG if you are running 10v and your 400 revs to its max at say 13000 then you will therefore need a brushless motor that gives 1300 rpm/Volt


Dave 
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nick_75au

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Re: Another brushless bowthruster question
« Reply #3 on: August 09, 2012, 08:57:18 AM »

A 22 series out-runner, 28 mm overall diameter has the same bolt pattern as a 400, a 1500 Kv motor or less for the higher voltage, the Speed 400 7.2V has a Kv of 2200 approximately, to be exactly the same on 10 volts a 1500 Kv motor is equivalent.

"xxxxx" about being too powerful, seriously, the motor will only pull as many amps as the propeller requires, brushed or brushless at the same RPM and prop will pull similar amps.

Cheers
Nick
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Subculture

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Re: Another brushless bowthruster question
« Reply #4 on: August 09, 2012, 10:23:46 AM »

Yes what Nick said.

Why do people keep equating brushless motors with high power levels? They're just electronically commutated motors, and if you want equivalent power levels, you just go smaller!

Very low kv's in small can sizes can sometimes be tricky to find, or expensive, but equivalents for the speed/mabuchi type motors are a cinch.

Bear in mind that most small reversible brushless controllers are generally configured to run 3S.

malcolmfrary

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Re: Another brushless bowthruster question
« Reply #5 on: August 09, 2012, 10:48:43 AM »

Or if the mount is already there, while a 6 volt speed 400 will be upset by excess voltage, a 15 volt version is the same price, will fit the same mount and will be quite happy.  Another alternative to calm a low voltage 400 down is to wire a resistor in series.  Yes it wastes some power, but a bow thruster is probably only going to run for a fraction of the time.
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Capitaine LaGaffe

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Re: Another brushless bowthruster question
« Reply #6 on: August 09, 2012, 07:51:41 PM »

PLEASE PLEASE PLEASE dont do it you seriously DO NOT want to go the brushless Motor route on a Bowthruster they are far to POWERFUL to be used on a bowthruster,why not get an electronic device to reduce the voltage to the thruster then you DO NOT have to use a brushless motor,if you are intent on using one then you will need to know what the max rpm is of the 400 then find a suitable sized brushless motor of the same size but YOU will have to calculate how many revs per volt off that particular motor.EG if you are running 10v and your 400 revs to its max at say 13000 then you will therefore need a brushless motor that gives 1300 rpm/Volt


Dave 
Eh? Too powerful? Well, I used to push SPEED 400 motors too about 80W (in at that level, the efficiency wasn't much to write home about) in parkflyers many years ago. The brushless outrunners in my tug on the other hand, about 25W (in) at full throttle (measured using Mpx sensors); about half the size of a SPEED 400 and capable of handling 240W.

I've spent many a happy hour calculating suitable motors, using paper & pencil or software such as MotoCalc. I'm no expert, but I'm not completely lost either.

/tm
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Capitaine LaGaffe

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Re: Another brushless bowthruster question
« Reply #7 on: August 09, 2012, 07:58:47 PM »

A 22 series out-runner, 28 mm overall diameter has the same bolt pattern as a 400, a 1500 Kv motor or less for the higher voltage, the Speed 400 7.2V has a Kv of 2200 approximately, to be exactly the same on 10 volts a 1500 Kv motor is equivalent.

Cheers
Nick
Which 22 series outrunner? The ones I've found (Hyperion, Scorpion, AXI, ) all have 3mm or 3.2mm shafts or a rather high Kv. Being used to aircraft motors, I'm probably looking in all the wrong places (plenty of nice motors, but with the wrong combination of Kv and shaft dia.).
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Capitaine LaGaffe

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Re: Another brushless bowthruster question
« Reply #8 on: August 09, 2012, 08:11:36 PM »

Or if the mount is already there, while a 6 volt speed 400 will be upset by excess voltage, a 15 volt version is the same price, will fit the same mount and will be quite happy.  Another alternative to calm a low voltage 400 down is to wire a resistor in series.  Yes it wastes some power, but a bow thruster is probably only going to run for a fraction of the time.
Basically. I'm just perverse (and if at all possible, I'll stick to brushless).

Where do you find a 15V Speed 400 (that a Mabuchi 380 what exactly)? The places where I usually shop don't sell any Speed 400 motors at all these days (and almost no other brushed motors: they sell mostly aircraft stuff).

I wouldn't bet on the percentage of time the bow thruster would run: The general idea is to spend as little time as possible going forward in more or less a straight line; all about having fun trying to tie the boat into a knot. ;-)
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malcolmfrary

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Re: Another brushless bowthruster question
« Reply #9 on: August 09, 2012, 09:24:06 PM »

Basically. I'm just perverse (and if at all possible, I'll stick to brushless).

Where do you find a 15V Speed 400 (that a Mabuchi 380 what exactly)? The places where I usually shop don't sell any Speed 400 motors at all these days (and almost no other brushed motors: they sell mostly aircraft stuff).

I wouldn't bet on the percentage of time the bow thruster would run: The general idea is to spend as little time as possible going forward in more or less a straight line; all about having fun trying to tie the boat into a knot. ;-)
http://www.howesmodels.co.uk/RadioControl/viewProduct.php?ProdID=1069
If your shop has stopped selling useful motors, it's their loss., and yes, a 400 = a 38x.  A "simplification" that has created confusion beyond the wildest dreams of any marketing people.  Remember that bow thrusters are relatively ineffective on a boat that is moving forward or backward, so really for spinning on the spot / moving sideways.
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nick_75au

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Re: Another brushless bowthruster question
« Reply #10 on: August 10, 2012, 06:58:41 AM »

The 1000 Kv I got there came with a 3mm and a 2.3 mm replacement shaft in its kit of accessories, it was a Pulso KA22-20L 1000 Kv.
whether they or others still supply it i dont know, I've got a spare one around some where :}

Nick
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Re: Another brushless bowthruster question
« Reply #11 on: August 10, 2012, 10:45:37 AM »

Most brushless motors tend to come with single digit metric shaft sizes e.g. 2,3,4mm etc. Can be a pain if you're trying to do a direct swap for brushed mabuchi canned motor.

Brushless motors aimed at the car brigade tend to come with  3.2mm shafts for compaitbility with pinions etc.

Capitaine LaGaffe

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Re: Another brushless bowthruster question
« Reply #12 on: August 10, 2012, 05:34:01 PM »

The 1000 Kv I got there came with a 3mm and a 2.3 mm replacement shaft in its kit of accessories, it was a Pulso KA22-20L 1000 Kv.
whether they or others still supply it i dont know, I've got a spare one around some where :}

Nick
That's a hard to find motor, and just about the only one with a 2.3 mm shaft I've been able to find with the exception of heli motors with a high Kv (> 3000). And there is the Hacker A10 series with 2mm shaft. I wonder if it would be possible to build a bow thruster more or less from scratch

Well, it was an idea: for the next project, a smallish freelance river tug/workboat/something/else, the Raboesch Mini Bow Thruster seems to be the best choice (312V).

(A 15V Speed 400 wasn't useful in a plane when Speed 400 was a popular choice; today a small brushless outrunner is much smaller, lighter, & efficient.)

Car motors tend to be large, heavy, and sensored
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unbuiltnautilus

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Re: Another brushless bowthruster question
« Reply #13 on: August 10, 2012, 06:05:46 PM »

How about an MFA Como Drills RE385 motor. A five pole variant on the 400 type motors. Lower Kv, greater voltage range ( up to 15v ) and all the same screw fittings and shaft diameter. Just a thought...
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malcolmfrary

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Re: Another brushless bowthruster question
« Reply #14 on: August 10, 2012, 09:25:32 PM »

How about an MFA Como Drills RE385 motor. A five pole variant on the 400 type motors. Lower Kv, greater voltage range ( up to 15v ) and all the same screw fittings and shaft diameter. Just a thought...
Thats whats in the link in reply #9.....
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Re: Another brushless bowthruster question
« Reply #15 on: August 10, 2012, 09:36:18 PM »

Worth pointing out that the MFA 385 is a very mild motor when compared with say 6 or 7.2 volt Graupner speed 400.

unbuiltnautilus

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Re: Another brushless bowthruster question
« Reply #16 on: August 11, 2012, 09:09:32 AM »

Thats whats in the link in reply #9.....

Good point, well made. I didn't see 385s mentioned in the text and didn't follow the link..
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