Model Boat Mayhem
Mess Deck: General Section => Tugs and Towing => Topic started by: bill stafford on May 30, 2015, 01:11:49 pm
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dear gents,
I need some help, for a change.
I read on this site were some people were using brushless to drive 60mm props, via 6V battery, a hobby king SK-3 motor, but little mention of there speed control
I am about to try brushless for drive motors ,and the other mayhem members seemed to know all about these motors in tugs,so I wish to ask about speed controls
what do you use, are the hobby king ones any good for scale tugs?? are the hawke any better.
I have a rc car/buggy version to play with, but it tends to be "lumpy", and not briliant ,for scale tugs.I intended to use brushless w 3:1 gear boxes, home made , to make them "throttle" better
thanks for any help
bills
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Go direct drive, please. No need to use the dreaded gearbox with BLDC motors.
What prop exactly are you going to use ? What manufacturer (Prop Shop, Raboesch ...) ? What type and what pitch ?
I'd go with a 500kv motor under 6V. If your tug has 60mm props, I assume you could fit a couple of nice big 6V SLA batteries.
Here's a big nice SK3 motor at HK : Turnigy Aerodrive SK3 - 5045-500kv Brushless Outrunner Motor (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=41512&aff=1225438)
There's also a 450kv version of the same (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=30966&aff=1225438). Might be even more suitable.
ESC-wise we've used these with great success once programmed with the right settings:
HobbyKing® ™ Brushless Car ESC 45A w/ Reverse (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=31780&aff=1225438)
HobbyKing® ™ Brushless Car ESC 60A w/ Reverse (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=11743&aff=1225438)
There's also the Trackstar 1/10th 60A car ESC which works great but is currently out of stock.
Smooth throttle response. Very low rpm start. Standard forward/reverse with no brake.
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Oops didn't notice your were down under and put links to the UK warehouse. But you should be able to find all that stuff either from the Aussie warehouse or their international/HK warehouses.
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I use the Hawk speedies and love em, do get the programmer though.
Phill
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If you get a chance have a look at my stan tug build, i used hobbyking sk3 motors and hawk esc's, plenty of low end control but i do run them on 12volt. http://www.modelboatmayhem.co.uk/forum/index.php/topic,42633.200.html
I know the importers of Hawk in Aus and they have excellent backup as far as warranty, if you have trouble getting Hawk then the new range of OS esc's are exactly the same and use the same hawk programmer, might be worth a look here....http://www.worldhobbies.com/home_rc_radio_control_models_os_engines_castle_page.html.
Phill
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gday gents ,
thank you so VERY much , this info was exactly what I was asking for, its hard to beat experience!!!
I will get some of these motors+probably the Hawk s/c soon.
I have my own drawing for the ocker white tug, approx. 750/800mm loa, 1/32 scale , that I have drawn up ,simplified ,aimed at beginners, that will make a nice test bed,as its not a copy of the other tug,I called it " ocker white".
Phil I love you tug, so much detail!! I have also built your white tug in the back ground, mine has 55 mm 4 blade prop+decerperm for power,but I'm not over happy w its power, I feel it needs 2 props, what drives it
regards bill
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ps page , sorry gents , i mucked up the repley,
tug name is knocker white , as the original tug ,my version , i have tear dropped the hull form, simplified hull shape and drive area,but I had low detail on the engine casing area+stern,so I took a bit of a guess?? it is aimed at a intermediate beginner , looks like a tug ,so must be a tug LOL most details /hard ware home made
I was originally intended to go w 545 drive , via tooth belts of 3:1 ratio , to nozzle w 60mm brass prop, plenty of grunt!!
i also use brass props on my models , Raboesch breed , more pitch and bite than plastic props
on my current G Guest paddle tug, im building a becker rudder, to help turn the beast
regards bill s
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The Raboesch #174 prop gives great pull. I'll use two of them, 55m dia, in Kort nozzles in my next twin screw springer.
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Don't the SK3 aero motors need any sort of cooling, being contained in the hull ? I'm assuming that in their 'airborn' function they would be in a very good airflow.
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If you run them at 6V and props < 70 mm definetly no {-)
At 12V with 100 mm Prop yes
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If you run them at 6V and props < 70 mm definetly no {-)
At 12V with 100 mm Prop yes
Hmmm, I thinkI should forget about running them on a 5S Lipo (18.5V) with a 50mm 3blade propshop prop. It may get a bit warm in there.
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Well, a 40" tug boat can reach a speed of 2.8 mph. It won´t get faster!!! no matter what you do (extreme overpowering to bring it to planing excluded :} )
On a "usual" 50 mm brass prop with pitch ratio of around 1 you´ll need exactly 2150 rpm to reach that speed.
You will want to add around 20-30% to that to create a giant bow wave on the hull --> 2800 rpm.
Any higher rpm will just increase the current (and slightly the waves created by the hull) but do NOTHING ELSE.
On 5S the motor would need 150kv or with the given kv of 500 you should run the SK3 motor on around 6,2V to reach the 2800 rpm (free wheeling rpm * 0,9 to get rpm under load).
With the 40" tug at estimated 40-50 pounds weight I estimate the current draw:
at 6V around 10-15 Amps --> around 60W outgoing power on the prop
at 5S at least 30-50 Amps --> at least 600W drawn out of the battery {-)
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Thankyou Time Bandit. I've got my head around it now.
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Any higher rpm will just increase the current (and slightly the waves created by the hull) but do NOTHING ELSE.
Well you'll probably get more bollard pull which is nice on a tug.
With the 40" tug at estimated 40-50 pounds weight I estimate the current draw:
at 6V around 10-15 Amps --> around 60W outgoing power on the prop
at 5S at least 30-50 Amps --> at least 600W drawn out of the battery {-)
Probably more than that. Propeller type is as much a factor as is the diameter, I suspect.
A 45mm #174 prop on a SK3 3542-800kv under 6V draw around 10.5A (66W).
Under 11.1V (3S) current is around 29A and we're way past the max rpm suggested by Raboesch.
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Well you'll probably get more bollard pull which is nice on a tug.
Probably more than that. Propeller type is as much a factor as is the diameter, I suspect.
A 45mm #174 prop on a SK3 3542-800kv under 6V draw around 10.5A (66W).
Under 11.1V (3S) current is around 29A and we're way past the max rpm suggested by Raboesch.
Bollard pull is not affected too much by rpm, the prop starts to cavitate pretty soon during bollard pull tests, normally way below the rpm for "hull speed" is reached. Main factor here is the prop itself (blade area...)
You´ll see that if you measure the bollard pull at different rpm, it has a maximum somewhere and the get´s lower again if you increase rpm.
A "usual" displacing hull needs between 2W and 3W per kg of the boat´s weight (output power not input) to reach hull speed and a "nice" bow wave, IF the rpm and prop pitch (diameter is not such a big factor) match the possible hull speed of the boat.
That´s why I came up with the 10-15A.
If the rpm is too high the current increases to create "waves".
Not sure about the "5S current", could be way more, but I intend to believe that the prop will not have enough grip to produce currents over 50A.
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Well, under 5S it would probably be useless.
I'll try and check BP at various engine speeds. I have only measured it at full throttle (which is below max recommended RPM) so far
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hello gents,
what uni`s do you use on brushless,I notice the damen tug has a different version , to what im used too seeing.
if I use a 12V battery+50/65mm prop , do I have to water cool motor ?? and what about speed control , I read some s/c units need cooling
in the motor section of the SK-3, there is a water cooled mount, radiator+water pump, any good??
thanks for all your help,
regards bill s
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It goes the other way around.
What tug are you building ? What scale ? --> what is the original props' diameter ? --> get the right props from Prop Shop or Raboesch --> choose the right motor/battery
You won't need water cooling on a tug.
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gday calimero,
thanks for your help, I havent decided on the next project yet,but I want to try brushless.
I have self drawing for the knocker white tug ,approx 750mm loa, 50/60mm prop in a nozzle, in 1/32 ,and this will probably be the test bed for the brushless drive, props.[size=78%] raboesch[/size]
i do most of my models in 1/32, typically 50/65mm props, some twin ,some single,so I`m trying to get some ideas for a future model , using brushless for power , in the past 545w 3:1 tooth belt gear-boxes
hope this makes sense
regards bill S
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Depending on the weight of that model, Bill, you should be absolutely fine with an SK3. But possibly think about 6v rather than 12. Those brushless motors have a lot of torque and will give a very scale performance at 6v unless the boat is very heavy.
Alex
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thanks for your help, I havent decided on the next project yet,but I want to try brushless.
I have self drawing for the knocker white tug ,approx 750mm loa, 50/60mm prop in a nozzle, in 1/32 ,and this will probably be the test bed for the brushless drive, props.[size=78%] raboesch[/size]
For a 60mm prop, I'd go with a 400-500kv outrunner under 6V
For a 50mm prop, you could go a little faster. There's a 620kv 42mm outrunner in the SK3 range.
I was actually going to use two of those 620kv 42mm outrunners with 6v SLA batteries in my twin screw springer tug (with 55m #174 Raboesch props). I even already have the motors (nicely built, as are usually the SK3) but I've changed my mind and will switch from SLA batteries to 9.9V LiFePo4. Those 620kv motors are then of course too fast.
Thanks to the drone guys HobbyKing now has small and slow brushless outrunners. I got a 360kv 35mm motor in the mail to test it. So light I'll be able to completely forego any motor mount. I'll replace the motor shaft with ... the propeller shaft and be done with it. No alignment problems !
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With the 40" tug at estimated 40-50 pounds weight I estimate the current draw:
at 6V around 10-15 Amps --> around 60W outgoing power on the prop
at 5S at least 30-50 Amps --> at least 600W drawn out of the battery {-)
with approximately 540W of the 5S setup being sent out of the system as heat.
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gday gents,
tug weight ,im guessing a bit , but,4.5/6 kg approx. ??
it is only 750mm loa,draws about 65mm of water , typical thames river tug ,w limited/non sea going duties, its a bit hard to be more accurate[size=78%],as its not built yet[/size]
all of my other models are 12 v battery , so plenty of 12 V chargers , not so in the 6 V area, so I would prefer to use 1 battery , of the 12 version ,but I am flexible
thanks for all the help , I have read EVER word , and am taking it all in
bill S
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if you want to stick to 12V you should get a 300kv Outrunner.
Like the Robbe Roxxy C35-30-45 with 300kv. Has enough power for a 10 kg boat.
The SK3 seems to big for such a boat anyways.
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gday tobias,
i dont trhink I can get robbe motors out her , in australia, but hobby king is available
most brushless are to high in Kv revs,aimed at model planes ??, but i will look around.
I think there were some low kv at hobby king,but for helo`s. but B IG bucks !!I am price shy,at this stage ,as I havent got brushless to compare too,what I do have are for planes.
alimero, were are those quode motors at hobby king?? and what part no.??
most have large shafts through motor,and 4/5mm prop shafts couldnt be mounted easily to them
I am ordering 2+SK-3 w500Kv ratings, I will play w them ,soon to get hawk 50A s/c +card
that will give me a starting point, either 6 or 12V SLA batteries , but if I can avoid saddle pack batteries, I will
regards and thanks heaps bill s
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Search through the Multirotor > Motors entry in the menu.
Even though they're slower, I think most are still too fast for 12V operation, unless you're going with smaller props (say < 50mm).
For 6V operation there are a few more options a little smaller than that big 50mm SK3:
Quanum MT Series 4108 475KV Brushless Multirotor Motor Built by DYS (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=67030&aff=1225438)
4108-480KV Turnigy Multistar 22 Pole Brushless Multi-Rotor Motor (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=41624&aff=1225438)
Keep in mind that if your tug is twin screw, you need one ESC per motor. You can't wire two motors to a single ESC like brushed motors.
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hello Calimero,
thanks for the info , the site im looking at here,doesnt seem to have a multi rotor section, could be I missed it ??
I knew about the twin motor,twin s/c , thats why I havent rushed into brushless for tug drives, costs $$
I have ideas of a small tg , 220mmloa+100/125mm beam , I havent drawn it up yet, but those small brushless , might be a option , i was thinking of twin 380 to 25mm props , could even be done w a single motor/prop, due to small size , weight is a issue , its the little tug at Niagara falls, little maid ?? has being unkindly called a shoe horn iron !! LOL
simple hull for,w flush decks and large pusher block on the bow, but im light on details
due to work/family/farn issues, i tend to plan my future models yrs ahead, and I like to know were I`m going, other wise , i dont get there
thanks every body for all your help
bill s
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Bill
The 380 is a racing motor (3-pole) and will run at maybe 18,000 RPM on 7.2v. You would be better to use the 385, which is a 5-pole version and much slower. I wouldn't have thought that a 220mm-long tug would be much use on anything choppier than a flat calm.
DM
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thanks for the info , the site im looking at here,doesnt seem to have a multi rotor section, could be I missed it ??
When on the http://www.hobbyking.com/ homepage, "Multirotors" is the third entry of the menu on the left side.
I knew about the twin motor,twin s/c , thats why I havent rushed into brushless for tug drives, costs $$
On the other hand, what's the point of building a twin screw tug if you can't have independant control of the motors ?
Maneuverability is so much better with independent throttles. I'd rather have independent throttles than a bow thruster, for example.
I have ideas of a small tg , 220mmloa+100/125mm beam , I havent drawn it up yet, but those small brushless , might be a option , i was thinking of twin 380 to 25mm props , could even be done w a single motor/prop, due to small size , weight is a issue , its the little tug at Niagara falls, little maid ?? has being unkindly called a shoe horn iron !! LOL
I've designed and 3D-printed a small springer tug/push boat. 190mm x 85mm. Weight ready to sail is 180 grams. You have to build really light (and add some ballast as low as possible).
(http://rc.noalia.fr/files/microspringer/20141230/tn/microspringer03.jpg) (http://rc.noalia.fr/files/microspringer/20141230/microspringer03.jpg)
(http://rc.noalia.fr/files/microspringer/20150105/tn/microspringer03.jpg) (http://rc.noalia.fr/files/microspringer/20150105/microspringer03.jpg)
I'm running a 1700kv brushless on a single cell LiPo (3.7V) with a 20mm prop (low pitch: ~ 11mm!).
Here's a video on Youtube: Microspringer launch day (https://www.youtube.com/watch?v=PZ92AC9zggQ).
And here's the project page on my site, with parts list, designs, build log ... 3D-printed Microspringer (http://rc.noalia.fr/boats/microspringer/).
From a single 3.7V/1200mAh battery (approximately the size of a AA battery) I get around 30-40mins on run time. And each battery costs like $3 ...
I'm probably going to print a twin screw version, probably the same length but a tad wider.
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Bonjour,
Tiny but mighty this micro Springer (https://www.youtube.com/watch?v=-llV3cAlrXc) isn' it :-))
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Raphael..."1700kv brushless"".........she sounds like a gas turbine engine O0........Derek
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Ha ha ! It's great fun sailing her around. She whizzes all over the place. She can hide in between larger docked boats. {-)
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Good low KV outrunner.
http://hobbyking.com/hobbyking/store/__70365__Multistar_Elite_3508_268KV_High_Voltage_Endurance_Motor_UK_Warehouse_.html
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calimero... have you considered putting the micro-springer up on shapeways?
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calimero... have you considered putting the micro-springer up on shapeways?
All the files have been uploaded on Youmagine and there are instructions (http://rc.noalia.fr/boats/microspringer/printit01) on my site.
You could get the files from Youmagine and upload them on shapeways. But it seems shapeways' website is a little dumb and is unable to scale down the files (they have to be scales down 1:10).
But you can probably easily find tools to scale STL files down. It's purely a mathematical operation.
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hello gents,
inertia, i cant get 385 easily in au, but off the shelf 360/380,we don't have much choice out here , in Oz
even though the 380 can be a battery killer,big motor ,and small prop , is OK
Calimero, I LOVE your little springer , it does sound like a turbine ,I have a friend in geelong ,who has built almost the same model , and used brushed motor ,and it also is a power house,for such a ;little model .
we do a public display, every 6 months , and the small models are fun ,as its not that big portable pond,and kids love water squites+novaltie models
due to my big hands, i normally build models to 1/32+750mm+ loa, much easier to get into for repairs, but its a challenge to build a small, dry, tug
now ,I can add brushless into these builds ,thanks guys
bill