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Author Topic: MFA Motor Problem  (Read 4393 times)

Marty

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MFA Motor Problem
« on: May 15, 2015, 02:06:33 AM »

Hello guys

I'm running my tug on tank steering using two mtroniks ESC of a 12v battery powering two MFA 6:1 geared motors.

Tonight i noticed that the starboard motor seems to be a bit jittery when full astern is applied. I've calibrated my radio gear to the esc on both motors but still the starboard one seems jittery. This only happens in the water on this particular motor.

Anyone come across this problem, if so any advice would be greatly appreciated.

Cheers

Martin
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derekwarner

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Re: MFA Motor Problem
« Reply #1 on: May 15, 2015, 02:24:04 AM »

Welcome Martin...should be relatively easy for the first trouble shooting operation  :-X

Swap the motors over from side to side.......DO NOT swap any other component in the individual drives apart from the motors

With an indelible pen, mark or number the motors so in the future you don't get confused  :embarrassed: as to what is what

Please come back with the results...... :-))... Derek
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Derek Warner

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inertia

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Re: MFA Motor Problem
« Reply #2 on: May 15, 2015, 09:24:33 AM »

These motors are notoriously "noisy" electrically. Although they are supplied with one suppressor capacitor across the brushes I always fit addition capacitors between the brush terminals and the motor case. 0.01uF disc ceramics are fine. I'd recommend this even if you are using 2G4 radio.
That said, Derek is right in that you need to find out whether the problem is with the motor or the ESC. If the problem follows the motor then it's that motor which is the cause. If it stays with the same ESC then that's the culprit.
DM
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Marty

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Re: MFA Motor Problem
« Reply #3 on: May 15, 2015, 07:18:00 PM »

Right guys! Thanks for the info last night.


I've just returned from the pond with my tug and its not the motors. I disconnected the esc and changed them over from the starboard to port motor and now the jittering is now on the port motor.


I'm thinking it maybe down to the fact that I'm running two motors off one 12v battery because the jittering only happens when I'm using moderate power on both motors for manoeuvring.


Any ideas guys, I've got myself a second 12v battery that I'm going to rig to one of the motors and see what happens.


Marty
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Colin Bishop

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Re: MFA Motor Problem
« Reply #4 on: May 15, 2015, 08:13:39 PM »

Batteries are extremely unlikely to cause jittering. as Inertia says, it is almost certainly down to the speed controller on the affected side.

Colin
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Marty

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Re: MFA Motor Problem
« Reply #5 on: May 15, 2015, 08:41:35 PM »

I'm running on one side a 20amp and on the effected side 40amp.


The 20amp difference between ESC, could that be causing the jittering?


Marty.
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Colin Bishop

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Re: MFA Motor Problem
« Reply #6 on: May 15, 2015, 08:46:28 PM »

Possibly but why on earth would you fit mismatched speed controllers in a boat?

Colin
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Marty

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Re: MFA Motor Problem
« Reply #7 on: May 15, 2015, 08:49:39 PM »

Im new to the hobby a mtroniks told me it would run fine alongside the 20amp.


Guess they were wrong.
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Colin Bishop

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Re: MFA Motor Problem
« Reply #8 on: May 15, 2015, 09:04:12 PM »

Bit of a gamble really. Might work, might not. Always best with electrical setups to keep everything in balance. In your case it is possible that one speed controller is affecting the other in some way which could account for the jittering. It will be interesting to see what others think.

Colin
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Subculture

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Re: MFA Motor Problem
« Reply #9 on: May 15, 2015, 09:08:47 PM »

Have you isolated the BEC on one of the controllers?

Colin Bishop

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Re: MFA Motor Problem
« Reply #10 on: May 15, 2015, 09:36:10 PM »

Subculture has a very good point. If you are relying on the main battery to power the speed controllers without a separate supply then if both controllers still have the BEC wire enabled then you would experience the problems that you have.

Colin
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Marty

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Re: MFA Motor Problem
« Reply #11 on: May 15, 2015, 10:02:08 PM »

I've removed the red Bec wire when I installed the electrics in the tug from the 40amp ESC.
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Colin Bishop

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Re: MFA Motor Problem
« Reply #12 on: May 15, 2015, 10:07:24 PM »

A bit problematical then!

Hopefully we will have an expert opinion.

Colin
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derekwarner

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Re: MFA Motor Problem
« Reply #13 on: May 15, 2015, 10:21:33 PM »

Marty...so from this we assume you are using an external Rx power supply?....

[it always assists to tell all at the onset :o...is there any other curio in the setup you have not mentioned?]

You have also proved that the jitter is now in the port side circuit, however this does not necessarily conclude that the motor from the stdb side is the culprit  >>:-( as the motor only presents a profile to it's control equipment

A BAS [black art specialist] someone like DM may suggest electronic check valve thingies in the wiring as clearly an unbalanced back EMF could be the root cause of the jitter

I understand that money does not grow on trees.......however if the motor current draw is not an issue with the 20 amp ESC & if funds permit one option is to purchase an IDENTCAL specification ESC....by careful as mtronics offer three versions of their 20 amp marine ESC.......good luck........... Derek


 
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Marty

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Re: MFA Motor Problem
« Reply #14 on: May 16, 2015, 12:28:53 AM »

Derek! Thanks for the words of wisdom.


I've decided to remove the 40amp and replace it with a 20amp. I'm quite sure that it's causing the problem.


I'll be in touch soon hopefully with this issue resolved, thanks to everyone who's given some input it's much appreciated.


Cheers


Marty
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Subculture

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Re: MFA Motor Problem
« Reply #15 on: May 16, 2015, 07:41:00 AM »

I generally find that the best solution to problems with Mtroniks controllers is to use one or more of these.

malcolmfrary

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Re: MFA Motor Problem
« Reply #16 on: May 16, 2015, 08:01:30 AM »

It might well be that the 40A one has a different response to that of the 20A and might give a bit of mid range jitter without any outside interference.  Two matched ones should cure the problem.  Unless it's in the supply to what was the 40A one.
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inertia

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Re: MFA Motor Problem
« Reply #17 on: May 16, 2015, 09:18:28 AM »

I have handled several of the 20A MTroniks ESCs and I'm afraid I have to say that I was not impressed. They all seemed to have very poor control at higher speeds and the motors tended to "hunt" at full speed. The 10A and 15A ones don't do this.

An ESC transplant would seem to be be sensible. 20A continuous current-handling is more than enough for these motors; 40A is well OTT. I'd chuck 'em both into the same drawer. Unfortunately I believe that Mike has stopped making the FR40 ESC, but for twin motors this is a no-brainer http://www.componentshop.co.uk/p94-dual-esc-and-mixer-2-x-20-amps.html
There's a helluva lot of 'em about!

Dave M
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Marty

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Re: MFA Motor Problem
« Reply #18 on: May 27, 2015, 01:37:00 AM »

Hello guys

Thought i should give you an update on the ESC and motor issues i was having.

Today i installed two new ESC's, 20 amp viper marine and installed a second 12v battery, so now I'm running two motors each with it's own individual battery. I've also removed the power wire from each ESC and rigged a 5v power supply direct to the receiver. I was advised to this as i believe it prolongs the life of the ESC's, this was suggested to me after a very intresting phone call with a member here on the forum.
I tested the motors and ESC's in the bath and everything is running smoothly.

I've also installed two new props which has greatly improbed her towing ability. So looking forward to sailing her tomorrow on the pond

Thanks to everyone for there help.

Cheers

Martin
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derekwarner

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Re: MFA Motor Problem
« Reply #19 on: May 27, 2015, 03:50:48 AM »

Hi Marty..............good to hear that that glitch is gone  :-))...however by installing a second independent 12 volt battery ...you have introduced a new potential for the black arts to jinzx your electrical system

If the second battery was for either ballast or and longer running times, a black art member may suggest an alternate way to wire both batteries to ensure each motor sees the identical voltage & current storage available........................... Derek
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malcolmfrary

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Re: MFA Motor Problem
« Reply #20 on: May 27, 2015, 09:57:47 AM »

If each ESC is now powered by its own battery, there is little scope for them to annoy each other. 
If the RX supply is also a separate battery, that has little scope for creating problems other than forgetting to charge it.  OTOH, if it is derived from one of the drive batteries, that battery will have that bit of extra load on it.  The ground line from the battery to that ESC needs to be REALLY good.  There is scope for the ESC to get its ground return via the RX wiring, which is not a good thing.  At best, this gives some strange control issues, at worse, it vaporizes the metal in the ESC-RX black wire.
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