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Author Topic: large boat motors  (Read 13476 times)

Jerry C

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large boat motors
« on: July 02, 2011, 02:20:13 pm »

Hello mermod here , I would like an opinion on motors for my star perseus.
the boat is 1.6 metres long and quite heavy ( car battery on board ) it currently runs 2 car blower motors and 65mm props it runs ok but is very sluggish, I was wondering how 2 robbe power 1000 motors would work as i have heard a lot of good things about these motors and the robbe odin seems to perform quite nicely on one.
If anyone has repowered a blower motor driven vessel with the robbe motor i would love to hear how it went and if it would be worth the expense (about $100 each down here)

Martin (Admin)

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Re: large boat motors
« Reply #1 on: July 02, 2011, 02:32:26 pm »

What type of boat is the Star Perseus?

BTW: Robbe power 1000 motors are simply IC starter motors with the switch and pulley removed... and 4 x the price!
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nemesis

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Re: large boat motors
« Reply #2 on: July 02, 2011, 04:19:59 pm »

Hello, A car blower motor run generally at 3000rpm, which may be too slow for you, have you tried 18volts? it may do the trick. Another thing to look at is, are the props a wee bit too big? and not allowing the motor to rev freely. You have 2 parameters to chose from. Change one at a time, Nemesis
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ayrshire andy

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Re: large boat motors
« Reply #3 on: July 03, 2011, 01:02:11 am »

Hi mermod,

GO BRUSHLESS! Here in the UK you can buy even a 6 KILOWATT  brushless motor for under £100, so you should be able to find an what you need for a good bit less, with brushless you can enjoy zero brush and commutator friction/wear because there are none, higher electrical efficiency, higher watts per gram motor weight and size and more watts per dollar motor cost, true you have to buy a new brushless ESC but a big boat deserves a proper powerplant, good luck and please don't spend a fortune on heavy, underpowered and overpriced conventional motors...unless you really want to! Do let us know how the re-engining goes!

Andy
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Re: large boat motors
« Reply #4 on: July 03, 2011, 02:10:05 am »

Im running similar, two fan motors ,direct drive ,twin 65mm L/R ,3 blade,Type "A" brass props from Raboesch..On a 42lb, 36inch Dumas Shelley Foss.. Its a powerful set up . I can wash the decks under full throttle..


your ship weighs more than  35kilo's by what your describing. and big :-))

The only thing ive been able to find is the DSV Star Perseus.

The blower motors are torque so spinning a larger prop up to 85mm should not be a large order. That's all subject to the ship.
Or use a 65mm prop with a larger pitch.

It would be nice to know what type of prop you are using now,pic's maybe. Your props may well be useless after 5000 rpm depending on the style. A faster motor may only destroy them, or injure you.
If they are plastic stock Robbe,Graupner,or Billings Your ship may benefit from a prop exchange

visit these two places to get a better idea

http://www.prop-shop.co.uk/index.php?section=home

http://www.raboesch.com/

http://www.raboesch.com/CATALOGUS_2-2010_WEB.pdf


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nick_75au

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Re: large boat motors
« Reply #5 on: July 03, 2011, 02:22:38 am »

http://www.modelboatmayhem.co.uk/forum/index.php?topic=170.0

Is This It?

Martin, I had to modify the brush gear on my "starter motors" as the cheap starters have plastic brush holders, they melt under any sort of sustained load, I wonder what the brush gear in the Robbe motors is like?
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Re: large boat motors
« Reply #6 on: July 03, 2011, 02:33:02 am »

Funny you mention that Nick..

Generally starter motors are for intemitant use with a particular duty cycle..hence the burnt brush holders..reminds me of the 11hp Brigg's and Stratton engine i got ..brush holder melted in the starter. Over used and underloaded current wise.
 it is possible to underload a starter motor when the rated voltage drop's and current is lost that to can burn the brushes.
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Jerry C

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Re: large boat motors
« Reply #7 on: July 03, 2011, 05:45:42 am »

she is the diving support vessel Star Perseus which is now HMNZS Manawanui A09.
The props are Rivabo 65mm 5 blades in steerable nozzles ( the nozzles arent on the original but should help manouverability  with such a long boat )
The current motors a from a holden and draw approx 3.8 amps on the bench ,but the shafts are new and you can hear it running more freely every time it runs.
As an interesting sidenote i have had these motors for about 20 years , they were found in two half buried cars in the sand dunes at a place called Sharks Bay in Western Australia , after pulling them apart they were found to be as good as the day they were made.

DaveB

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Re: large boat motors
« Reply #8 on: July 03, 2011, 07:18:09 am »

Hi Mermod
I used to run Flying Phantom on a car blower motor with a 100mm kort nozzle she'd do okay but would run hot, i managed to get hold of a robbe 1000 and i could'nt be happier motor runs cool and plenty of run time go for it.
Dave
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nick_75au

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Re: large boat motors
« Reply #9 on: July 03, 2011, 07:43:54 am »

You will want to run the motors at around 3800 RPM under load, so a motor that spins at 5-6000 RPM unloaded is what's needed.

The Robbe motor if I have the specs correct is about 7500 - 8000 RPM at 12 volts, Yes it will give you more power, Ideally it would need a slight reduction to bring the efficiency up but running a car battery that's a non issue.

Unfortunately I found another spec. that mentions only 2500 rpm (i think possibly incorrect) which would be slower than the blower motors and my modified Prolux starters spin at 4000 rpm.

Another option is use geared 700's, John Darke is the man to contact to get these motors.

johndarke1  (at) tpg  .  com  . au

cheers
Nick
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Jerry C

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Re: large boat motors
« Reply #10 on: July 03, 2011, 08:10:09 am »

thanks for the advice nick 75  I have used darke horse motors in my typhoon sub at 1.8m and they are fantastic, however , after a particularly nasty warranty issue with this dealer I will not be using his products under any circumstance.

Jerry C

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Re: large boat motors
« Reply #11 on: July 03, 2011, 08:14:07 am »

ayrshire andy would you be able to supply any links for these brushless motors?

nick_75au

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Re: large boat motors
« Reply #12 on: July 03, 2011, 08:36:28 am »

If you want to go brush-less  you should look at around 500 Kv motors, you don't need a 6 kilowatt motor %) Your maximum draw is going to be no more than 15 amps at full throttle (regardless of  brushed or brushless) Because low Kv brush-less are usually large, the smallest 500 Kv motor will still have enough power.

An AXI 4120/18 at the expensive end of the spectrum or a

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6231

at the inexpensive end, you will need to replace your speed controls as well the 30 amp car ones should be adequate.

cheers
Nick
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Jerry C

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Re: large boat motors
« Reply #13 on: July 03, 2011, 09:06:42 am »

food for thought nick 75 , i still have trouble getting my head around the fact that a motor thats only 60 mm long could power my big girl, I have been looking at the motors available here in Australia through Model Engines (www.modelengines.com.au) I see that os will be releasing a range aimed at larger models , if you have the time Id like to hear what you think about the motors on offer there as they are easy to get through aussie hobby shops , what speedies would you reccommend with fwd and reverse for brushless ?

nick_75au

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Re: large boat motors
« Reply #14 on: July 03, 2011, 10:06:44 am »

I had a look, the hi mark 515Kv and OS 490Kv are the ones you want to look at (multiplex page wouldn't open for me) if you want to go that way. Hobby King will save you a packet over the hobby shops though, the other motors I have seen in the hobby shops are the E-flight range power 46 at 670 Kv or Power 60 at 400 Kv though both are a little out of what I think would be the best Kv for your boat . ESCs are a little harder if you are unwilling to go on-line, The Castle stuff is good from most reports, I have no experience with any of the "brand name" stuff though.

I've used a brand called Pulso, and the Hobby King 30 amp car ESC,s and helped out with the Seaking brand.

One of our club members is running the 500 Kv Hobby King motor in a HDML on only 6 volts and it is only pulling 10% of the amps the motor is capable of ok2

Cheers
Nick
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ayrshire andy

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Re: large boat motors
« Reply #15 on: July 03, 2011, 12:04:07 pm »

Thanks Nick for the bundles of good info, my knowledge did not extend as far as brushless suppliers in Oz,  :embarrassed: Hi mermod, brushless motors are indeed little tornados in a box so even a 60mm long one will give you horsepower with a little more internal space to play with, good to see those steerable Korts to more effectively turn your new-found watts into bollard pull, I did wonder from the photos could you further reduce the clearance between blade tips and nozzles ie how big a prop could you fit in there and still have running clearance? I have yet to use Korts and just wondered what others have found can be done to increase propulsive efficiency so that you can have lots of power and as much run time as possible. Excellent boat, keep us posted!
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andyn

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Re: large boat motors
« Reply #16 on: July 03, 2011, 01:09:36 pm »

The obvious answer is a pair of MMB 900's..... With brushless, you're gonna end up spending 300 quid on something that will draw so many amps it isn't worth it at all...

Watch the sparks fly as I get told off for putting in a point about something I know a lot about  {-)
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ayrshire andy

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Re: large boat motors
« Reply #17 on: July 03, 2011, 02:45:21 pm »

Have found that Giant Cod are well worth a visit to see the current state of the art with brushless, you can have a miniscule motor weighing 7 grams taking up to 18 watts input for £10 at one end of the scale, right up to a 6.5kiloWatt beastie weighing 1750g for £91 odd :o...I am not connected merely a happy customer who recently bought something a bit more midrange, a cracking little A2208/8 20Amp capable 2600kV brushless for £6 which weighs in at only 36G grams but could provide you with nearly 200 watts of output...brushless has come a long way but we as a model boat community have maybe been a little slower to exploit the great potential that they offer...of course you have to buy a brushless ESC if you have n't already but you can get one capable of handling 90 Amps continuous and 21 Volts for £49, with far smaller and far bigger capacities available depending on how much or how little you would like to spend... %) but brushed I am sure will always have a place! ok2  
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CF-FZG

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Re: large boat motors
« Reply #18 on: July 03, 2011, 03:27:22 pm »

The obvious answer is a pair of MMB 900's..... With brushless, you're gonna end up spending 300 quid on something that will draw so many amps it isn't worth it at all...

Watch the sparks fly as I get told off for putting in a point about something I know a lot about  {-)

Andy, if you know so much about brushed/brushless then you'll realise what a misleading and wrong statement you made at the top of the quote.  There's no reason a correctly selected BL motor will draw more Amps than the brushed motor it would be replacing - after all, if the voltage is the same and the watts output is the same, why would the Amps drawn be any different %)


Mark

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andyn

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Re: large boat motors
« Reply #19 on: July 03, 2011, 04:45:18 pm »

Watch the sparks fly as I get told off for putting in a point about something I know a lot about  {-)


You find me a brushless motor then Mark that on 24v will swing a 55mm plastic prop and draw less than 6 amps continuous then? {-)
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Dekan

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Re: large boat motors
« Reply #20 on: July 03, 2011, 06:09:13 pm »

I had a look, the hi mark 515Kv and OS 490Kv are the ones you want to look at (multiplex page wouldn't open for me) if you want to go that way. Hobby King will save you a packet over the hobby shops though, the other motors I have seen in the hobby shops are the E-flight range power 46 at 670 Kv or Power 60 at 400 Kv though both are a little out of what I think would be the best Kv for your boat . ESCs are a little harder if you are unwilling to go on-line, The Castle stuff is good from most reports, I have no experience with any of the "brand name" stuff though.

I've used a brand called Pulso, and the Hobby King 30 amp car ESC,s and helped out with the Seaking brand.

One of our club members is running the 500 Kv Hobby King motor in a HDML on only 6 volts and it is only pulling 10% of the amps the motor is capable of ok2

Cheers
Nick


I have acquired a Eflite 46 brushless motor from a aeromodeller friend, who's giving up. Im saving it for a 46" sea commander :-))
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RaaArtyGunner

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Re: large boat motors
« Reply #21 on: July 03, 2011, 10:07:02 pm »

in the sand dunes at a place called Sharks Bay in Western Australia , .

Trivia.
A beautiful spot and renowned for the dolphins which come in to be patted in shallow water.
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nick_75au

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Re: large boat motors
« Reply #22 on: July 04, 2011, 05:05:39 am »


You find me a brushless motor then Mark that on 24v will swing a 55mm plastic prop and draw less than 6 amps continuous then? {-)

Show me a measured RPM and watt meter holding the boat in the water at full throttle, I will find you that motor :-))

Put your money where your mouth is OK

Only just looked it up  The MMB 900 is about 540 Kv so has a RPM of 13000 at 24 volts unloaded.
My money is the motor will be pulling a minimum 25 amps with the above set-up

Cheers Nick

P.S.
I have a motor that under load draws 5 amps full throttle holding the boat still in the water with a 100 mm Raboesch 4 blade prop on 24 volts, there's a trick in that one Wink
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Jerry C

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Re: large boat motors
« Reply #23 on: July 04, 2011, 12:44:01 pm »

Thanks everyone for all the ideas , its a bit hard to turn your back on the tried and true brushed motors we all know so well , but  i must say that the specs on that turnigy brushless are very interesting indeed , and the prices on that website are amazing I can assure you that their retail price is well below the wholesale price of similar products here in Australia, no wonder the local shops are suffering so badly , as for my decision , as soon as funds become available I will be experimenting with brushless in the perseus , the motors i need appear to be on back order at the moment but when I proceed I will post more pics and keep you guys updated, thanks again.

Jerry C

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Re: large boat motors
« Reply #24 on: July 04, 2011, 12:51:30 pm »

hey nick 75 what do you think of the turnigy dlux 70a bec brushless controller on the hobbyking site, this looks like it would be a good match for the tr 42-60c motor , it appears to have forward and reverse and at 70 amp it should be a safe option ( rather have higher amps than needed just in case)
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