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Author Topic: Have I made a big mistake?  (Read 2967 times)

edinsteve

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Have I made a big mistake?
« on: February 16, 2020, 01:17:30 pm »

Just finished building a Northlight puffer and bought an Mtroniks 600 motor and Viper Marine 15 ESC. Power is a 12v lead acid battery (mainly to add ballast) and the propshaft is the one supplied with the kit. I replaced the useless white metal prop with an identical sized plastic one. On the recommendation of the ESC I fitted a 10amp fuse for the 15amp ESC but when powering up the motor the fuse blows. Presumably the motor which quotes a startup current of 21 amps so presumably this is what causes the 10amp fuse to blow. So do I go for a 25 amp ESC and a fuse to match or a smaller motor as the cheaper option. Or am I barking up the wrong tree altogether?
Hope someone can help.
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coch y bonddu

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Re: Have I made a big mistake?
« Reply #1 on: February 16, 2020, 01:42:38 pm »

Personally I wouldn't bother with Mtronics but would defo go ACTion 20amp speed controller but thats a personal opinion as ive had many Mtronics catch fire OK other havnt but thats my take on it




Dave
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Re: Have I made a big mistake?
« Reply #2 on: February 16, 2020, 01:57:38 pm »

As I understand it your Viper marine is "6 to 12 volt Operation" Your fully charged 12v battery is putting out around 14.4v. I would confirm with Mtronics that you are safe to use this combination.

The Northlight's that I have seen have tended to be powered with a 385 motor with a 1.25in prop on 6v giving around 4500rpm unloaded ay around 1.25A. An Mtronics 600 motor is specified as having 15000rpm on 12v. To my way of thinking this is the wrong motor for a Puffer but rather is suitable for planing hull. A Puffer is a slow model so a much lower revving motor would normally be fitted. I don't know what prop you are using but I suspect that it is too big for the motor which is loading up & blowing fuses.


It might all work on 6v but first tell us about the prop details - make, diameter etc.

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edinsteve

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Re: Have I made a big mistake?
« Reply #3 on: February 16, 2020, 02:36:32 pm »

Thanks for the suggestions so far and it sounds like I should be going for a less powerful motor and run it on 6v. Reading other posts I wonder if my propshaft was binding causing the motor to stall. I have locked the nuts each end as tight as poss. as I wonder if they were spinning down on the thread and tightening everything up. I have run it a few times and now working but I still think I should follow the advice on motor and battery. I have contacted Mtroniks about the setup so will see what they have to say.
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Tug Fanatic

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Re: Have I made a big mistake?
« Reply #4 on: February 16, 2020, 02:52:13 pm »


......................Reading other posts I wonder if my propshaft was binding causing the motor to stall. I have locked the nuts each end as tight as poss.....................


The correct adjustment for the prop shaft is to tighten it just enough that it turns completely freely but does not have the freedom to move forward & backward. You should not have screw thread going into the bearings at either end of the propshaft. The nut at the prop end should be locked to the prop and I would always use a collet at the motor end which achieves the same thing.

If you do need to replace the motor you might be better off with a low revving 540 (eg an 80 turn Rock Crawler motor) that had the same sized shaft & motor mount as your 600 rather than move to a 385 where a new coupling and motor mount would be needed.


Again I ask for details of the prop. 
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chas

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Re: Have I made a big mistake?
« Reply #5 on: February 16, 2020, 03:34:15 pm »

Hi, I can confirm that the Viper is designed to work on a fully charged 12 volt battery, it's in some advertising and I do this myself. As Dave says, opinions vary about ESC brands, I've never had a problem with any Mtroniks unit, in 20 years.
   I think your problem is simple, the 600 motor is way over the top for a small boat. Try either a 385, these are OK up to 15 volts, I use them in 2 models, a 45 inch cruiser and 2 in a Bardic ferry, 42 inches long, both run on 9.6 volts so you should be fine.
If the 385 doesn't appeal then a 540 LN  ( NOT a standard 540)is probably a straight swap but is probably overkill.
Chas

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edinsteve

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Re: Have I made a big mistake?
« Reply #6 on: February 16, 2020, 03:38:04 pm »

Don’t know make of the prop - this is it - https://www.modelboatbits.com/3-BLADE-PLASTIC-PROPELLERS-M2-AND-M4 - RH plastic 40mm. The boat hasn’t been in the water yet so no idea how effective or otherwise.
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malcolmfrary

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Re: Have I made a big mistake?
« Reply #7 on: February 16, 2020, 04:00:33 pm »

If the locknut is done correctly, it is locked to the prop at that end.  Done correctly (prop in place, held firmly, nut tightened against the prop, DO NOT HOLD THE SHAFT), it can't walk and cause binding.  The shaft should spin freely by hand, and any endplay (and there should be some) should be minimal.  I usually like to have a brass washer or two between the locknut and the end bearing as a thrust bearing.  This also reduces the chance of the locknut being snagged by anything and unlocked when reversing.
Having the right combination of motor and pro helps.  The much repeated rule of "prop smaller diameter than the motor can, and fewer blades than the motor has poles" is still very true.  An overloaded motor is converting battery energy into heat, rather than motion.  A motor intended to rev fast being forced to run slow is also a recipe for heating the inside of the boat.  A 385 driving a 40mm 3 blade prop should be fine for a Puffer on 6 volts.  The slightly large diameter should be made up for by the fine pitch.
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Re: Have I made a big mistake?
« Reply #8 on: February 16, 2020, 04:11:04 pm »

Or you could go with one of these that lets you keep your 12v battery (assuming mTronics say it is OK) and will slip into the mount & coupling that you have already purchased, installed & set up. There are throttle settings other than flat out but this is little quicker than a 385 anyway (385 on 6v = 5800rpm and 555 on 12v = approx 5900rpm)

https://www.componentshop.co.uk/mabuchi-555-dc-motor.html
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edinsteve

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Re: Have I made a big mistake?
« Reply #9 on: February 16, 2020, 04:31:16 pm »

Thanks for that, the motor sounds an option.
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edinsteve

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Re: Have I made a big mistake?
« Reply #10 on: February 16, 2020, 04:33:30 pm »

I have tightened locknuts at either end against the coupling and the propeller. There is only slight endplay, enough to prevent binding and a brass washer each end of the tube as a thrust bearing. Motor definitely sounds too big so will be downsizing. Bought it early in the build as unsure if there would be room to fit later. You learn as you go along.
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Re: Have I made a big mistake?
« Reply #11 on: February 16, 2020, 04:39:11 pm »

It isn't that your motor is "too big" (unless it won't fit in the model) but rather that it delivers its power in an inappropriate way. The 555 motor that I have linked is pretty well identical in dimensions, other than being slightly shorter, to the motor that you already have but it is very different in power delivery.
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edinsteve

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Re: Have I made a big mistake?
« Reply #12 on: February 16, 2020, 07:57:57 pm »

Sorry, “too big” is the wrong description but you suggestion of a lower rated motor is definitely more suitable for me. Thanks for all your help.
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Akira

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Re: Have I made a big mistake?
« Reply #13 on: February 21, 2020, 01:30:35 pm »

EdinSteve,"You learn as you go along."  Good for you! Yes that is how it is suppose to work and how so many of us progressed in this hobby. Ythe ears ago when many of us started in this hobby, there was no internet, no social media, no YouTube, to guide us. Just a few, mostly gone now, magazines. Stick with it. There are not a lot of basics to learn and after you do, it is tricks, and other ways to skin the cat.Speaking from across the Pond, sadly most here are not willing to expend the time to "learn as you go along" Instant gratification is the name of the game here. Hats off to you and your fellow UK and European builders who are keeping the art alive.
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edinsteve

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Re: Have I made a big mistake?
« Reply #14 on: February 21, 2020, 09:01:30 pm »

Thanks for your encouragement, Akira. Being new to the hobby I assumed I would need to install equipment at an early stage and bought without asking the sort of advice a site like this can give. It is gratifying how helpful everyone has been and, hopefully, I can help some other down the line in a similar situation.
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Tug Fanatic

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Re: Have I made a big mistake?
« Reply #15 on: February 22, 2020, 09:34:27 am »

.................. Being new to the hobby I assumed I would need to install equipment at an early stage ............................
/quote]

You wern't wrong for some models. In models with more complicated access and where the sides of the boat are fitted after a basic core structure has been built it is easier to fit the drive train whilst you can easily see it and make sure of perfect alignment.

PS I am assuming that you have ensured perfect drive train alignment.
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edinsteve

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Re: Have I made a big mistake?
« Reply #16 on: February 22, 2020, 03:22:52 pm »

Well I have “down-sized” the motor and battery and it is now an Mtroniks 400 and a 6v lead acid battery. I had to modify the base it is attached to to keep the drive train in line and everything seems to work OK now. So fingers crossed  :-))
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Re: Have I made a big mistake?
« Reply #17 on: February 23, 2020, 09:54:02 am »

How hot does the M400 motor get when you have run it for a few minutes?
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edinsteve

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Re: Have I made a big mistake?
« Reply #18 on: February 24, 2020, 08:56:18 am »

I couldn’t tell you but I will give that a try and get back. :-))
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Re: Have I made a big mistake?
« Reply #19 on: February 24, 2020, 09:52:47 am »

Just to be clear I meant run with the prop in the water at full throttle. If it gets pleasantly warm that is OK but if it gets very hot then you are overloading the motor.
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edinsteve

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Re: Have I made a big mistake?
« Reply #20 on: February 24, 2020, 09:57:52 am »

Will have to wait for a run in the water but did a test run for about 10 minutes at full throttle. Motor was pleasantly warm to the touch but not excessively so. Nothing else got hot. A bit of vibration which I put down to coming from the universal joint but wouldn't consider excessive, i.e. can be felt at touch but not visibly noticeable or shaking anything.
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Akira

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Re: Have I made a big mistake?
« Reply #21 on: February 24, 2020, 01:46:10 pm »

Steve, Please do make sure that your prop shaft is well lubricated when you run her out of water. The water acts as a lubricant as well as a coolant for you prop shaft so out of water it is a bit out of it's element, so to speak.You do not want too ruin a good set of shaft log bearings by running them without lubricant.Sorry my comment is late in the process.....
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edinsteve

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Re: Have I made a big mistake?
« Reply #22 on: February 24, 2020, 02:24:14 pm »

Yes, I invested in a tube of lithium grease, actually to lubricate a dremel flexi-drive and made sure the prop shaft was well greased as well.
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Akira

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Re: Have I made a big mistake?
« Reply #23 on: February 24, 2020, 06:04:35 pm »

Well done. You are a step ahead.
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RST

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Re: Have I made a big mistake?
« Reply #24 on: February 24, 2020, 06:47:38 pm »

Are you getting stuff from wonderland or marionville models or on-line? Bits will come in handy for next model anyway!
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