Model Boat Mayhem
Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: desktoprover on March 24, 2017, 12:34:10 am
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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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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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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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Also See: https://youtu.be/QaIjdgTiP0o?t=11m45s
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I seem to recall that Leen was using Turnigy 480kv outrunner in his Maersk Topper.
So I think you have the correct range.
:-)
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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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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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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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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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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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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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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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Great! Do you have a brushless motor replacement in mind for the Pittman motors?
Nope.
But hope springs eternal :}
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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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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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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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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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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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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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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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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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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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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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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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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 (http://sylvainrioux.zenfolio.com/img/s6/v138/p1324013757-4.jpg)
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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 (http://sylvainrioux.zenfolio.com/img/s6/v138/p1324013757-4.jpg)
one big difference between brushed and brushless motors is that brushless motors do not slow down under load. your 1250 unloaded rpm for your brushed motor is probably closer to 1000 rpm when the boat is being pushed around in the water. the 1800 rpm of the brushless motors will be more like 1750 rpm under load. you will be happy with brushless outrunners that run the props at 1400 rpm unloaded.
this phenomenon is due somewhat to the slightly larger amount of torque the brushless motors have, but mostly to how the brushless ESCs operate.
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That's great information, thanks a lot!
Since it will be a direct drive set-up I wonder if they will slow down a little more than 50rpm?
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That's great information, thanks a lot!
Since it will be a direct drive set-up I wonder if they will slow down a little more than 50rpm?
nope. my knowledge is limited to what i see, no electronics theory here, but to me, all the magic is in how the speed control feeds electricity to the motor. if you ask for 1200rpm, its going to do everything it can to give you 1200rpm. you will either get 1200rpm or you will get smoke. really good speed controls will refuse to kill themselves, so instead of smoke you will get nothing, analogous to tripping a circuit breaker. cheap chinese speed controls will probably give you smoke if you ask too much of them.
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Understood. I don't want smoke :-))
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One more question. What is the deal with the programming card? Is it possible to program the esc without it or do I need that card absolutely?
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that depends on the card and the speed control. some of the cheaper speed controls offer no programability, so no card, others offer more programability if you use the card instead of the throttle stick on the radio. some are so convoluted to program using the throttle that you will lose your mind if you don't use the card.
my preferred speed controls don't use cards, but the manufacturer has windows software that allows you to program even more features than a card does.
i use the castle creations mamba micro or sidewinder micro for any scale model i care about. they are much more expensive than the speed controls you can buy at hobbyking, but i feel they are well worth it. (you can find the sidewinder micro for $50 to $55) to use the software, you need to get a special usb adapter that plugs into the speed controller. ($20) I like them because you can do all kinds of things like set an exponential curve to the throttle, allowing for a low speed bias, with the throttle stick being more sensitive towards neutral. you can also set them to have no "stutter" between forward and reverse. lastly, if your motor spins too fast at maximum speed, you can reduce the actual output to a percentage of true potential in single digit increments (so, if 90% of true output is what you want, 90% of true maximum can be set) because i have model submarines that in real life run extremely slow, i have used the speed control to use only 30% of the maximum power.... another way to limit your maximum rpm at the prop.
if you do buy a cheap speed control that offers programming via a card, the cards are generally less than $10, which makes them better to have than not have.
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Big thanks again for your help.
Would you consider this one to be cheap? That's the one I was thinking about.
https://hobbyking.com/en_us/turnigy-brushless-esc-60a-w-reverse-prog-v2-2.html
I can't find what's the max amp rating of the Castle Creation Sidewinder Micro?
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This is the card for it and check the postage as it is in HongKong
[/size]https://hobbyking.com/en_us/turnigy-speed-controller-programming-card.html (https://hobbyking.com/en_us/turnigy-speed-controller-programming-card.html)
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yes... even though it is over $40, you can tell it is "cheap" by the fact that its associated programmer only allows you to alter 3 settings. and it mentions nothing about having a "stutter" to go from forward to reverse, which generally means that it has this functionality.
the "stutter" is what i describe as some sort of hindrance that the speed controller invokes to keep you from going directly into reverse. either having to press reverse twice, or sit in neutral for a predetermined fraction of a second. this is something that helps protect gearboxes in cars, but doesn't help in any way for boats.
most car speed controls that offer this label it as something like "rock-crawler" mode.
the castle creations speed controls allow you to enable or disable neutral "stutter" functionality using the software.
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Very instructive again, thanks.
Is that the one you are using? I can't find how many amps it can handle?
http://www.castlecreations.com/en/sidewinder-micro/sidewinder-micro-2-esc-010-0150-00
I do have that stutter thing on a Mtroniks Viper Marine ESC (brushed) and I hate that. I want to make sure I can disable that function.
Thanks jaymac for the link.
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yes, that is the model i use for the vast majority of my model boats and subs... i believe i have 14 of them now. you will never find an official quote from castle creations on how many amps the speed control will handle, but most educated users claim it will handle 25 - 30 amps. as i said earlier, my 4 foot tugboat with 6v SLA draws less than 2 amps per motor. another note that my not have been stated earlier in this thread is that you need a single speed controller for each motor. in brushless setups, you cannot share a single speed control across multiple motors.
the other CC speed control i own several of (6 or so) is the mamba micro.
the only real difference between the CC sidewinder micro and the CC mamba micro pro boils down to these:
1) new mamba micro X can support sensored motors.
2) mamba micro has heat sinks on the FETs, it can handle slightly more amps +5 over the sidewinder micro... if that small difference in amp rating makes the difference between you buying the mamba micro or the sidewinder micro, you are probably going to want to use the full size sidewinder instead.
3) new mamba micro X has an auxiliary second channel that can be used for things like altering the max rpm setting. nice in theory, but basically useless in real world usage.
for anything over 30 amps, i basically use the "cheap" chinese speed controls, they are either for cars or fast (50+ mph) speed boats, so going for a 200amp speed control that might last two seasons before dying, makes me look for something that can be replaced affordably.
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Thanks, this is very appreciated.
The specs for the motor I'm looking for states that the max amp is 65A. It feels pretty high to me. I'm pretty sure I'll never reach that but.... Do you think the Sidewinder micro could handle it? Or maybe I should go with the full size Sidewinder? Do they have a protection for overheating or too high currents?
I always use one esc per motor on all of my boats so that's not a problem for me.
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This is the main problem we, as boat modellers, face. 65 Amps requires a large speed control, but that is probably turning a 14" aircraft prop at something between 14 and 20 volts. We are hardly pushing these motors at all, as detailed above. So we have to reconcile the use of a small speed control on a potentially big current motor. This is the stumbling block where many modellers who are used to 'old school' thinking fall over. Not helped by motor suppliers skewing their data towards the peak performance capabilities of their motors.
Which puts us either into the hands of the slavish specification followers, or those willing to take the plunge and find out through trial and error. I know whose opinions I value.
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desktoprover, i agree completely with unbuiltnautilus... the specs regarding the 65amp max that the motor is rated at are more like the boundaries... do not exceed 65 amps at 6s (42 volts) which can be better stated as 2700 watts. if you try to push more than 2700 watts through that motor, it will let out the smoke. there is nothing we can do on purpose with a 4 foot long tugboat that would draw more than 10 amps with a 6v SLA, and if we are smart, we will put a 20 amp fuse between the speed control and the battery, just to make absolutely sure.
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That makes perfect sense. Thanks a lot to both of you. I'm sure this thread will be very informative for others to refer to in the future.
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desktoprover, i agree completely with unbuiltnautilus... the specs regarding the 65amp max that the motor is rated at are more like the boundaries... do not exceed 65 amps at 6s (42 volts) which can be better stated as 2700 watts. if you try to push more than 2700 watts through that motor, it will let out the smoke. there is nothing we can do on purpose with a 4 foot long tugboat that would draw more than 10 amps with a 6v SLA, and if we are smart, we will put a 20 amp fuse between the speed control and the battery, just to make absolutely sure.
All perfectly true unless you get a rope or something tied around the prop where suddenly those high load amps start to apply. It then becomes a matter of what gets destroyed first. It might be the battery, the wiring or the controller, so you need put a fuse after the battery.
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6S is more like 22v surely.
Ned
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All perfectly true unless you get a rope or something tied around the prop where suddenly those high load amps start to apply. It then becomes a matter of what gets destroyed first. It might be the battery, the wiring or the controller, so you need put a fuse after the battery.
Using a fuse between the esc and battery is always a good idea.