motor and speed controller trouble

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8 April 2009 at 16:52 #20046
Queequeg Quint
Participant
@queequegquint38270
I have a 35 inch model lobster boat hull. Motor is MFA Como 540 Torpedo with 2.5:1 gear reduction. Electronic speed controller is Mtroniks 15 marine. Battery is 12 volt with 12AH. Propeller is 45mm in diamater, 4-blade brass prop.

Here’s the trouble. When I go forward, the motor stutters alot. Sounds like it’s going on and off rapidly. This happens at all speeds. When I go reverse, the stuttering is much less, motor runs more smoothly. But it stil isn’t perfect. This happens in the water, or on the workbench.

I put gear grease on the metal gears hoping that would solve the problem. That solved the problem for a while. But then after I ran it in the water for about 30 minutes, the stuttering came back.

I don’t know what the problem is. Not sure is some water splashed into the motor, maybe that’s the problem.

Any advice would be helpful!!

Queequeg
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8 April 2009 at 16:52 #5032
Queequeg Quint
Participant
@queequegquint38270
8 April 2009 at 18:17 #20049
60watt
Participant
@60watt
Unless you mean the deleted Como Drills RE540/2 there is probably nothing faulty other than the 540 is too much for the Marine 15 esc.

A power choke rated at 100uH, 10 amp might solve the problem by smoothing out the current drain.
8 April 2009 at 18:33 #20050
Queequeg Quint
Participant
@queequegquint38270
It is the MFA Como Drills RE540/1 (Torpedo 500).

Is there another ESC that might work well with this motor?

I’m thinking about the FR15 by a company called Electronize.

http://www.electronize.co.uk/model_electronics_frames.htm

Thanks
8 April 2009 at 19:10 #20051
60watt
Participant
@60watt
I gave a £1 remedy to what I think is the likely problem.An email to Tony of Mtroniks might get you more info.

Myself,I would change the motor rather than the esc but I wouldn’t do that either.I’d try a choke.Toroids are available from Maplins and in any old radio or computer equipment,enammelled copper wire can be obtained from transformers.If you don’t know the background then trial and error will sort it.

Good luck
9 April 2009 at 04:27 #20060
Queequeg Quint
Participant
@queequegquint38270
When you say the 540 is too much for the Marine 15 esc, do you mean that the esc doesn’t have a high enough amp rating?
9 April 2009 at 09:52 #20068
60watt
Participant
@60watt
If your motor is not boiling hot after two minutes on twelve volts the average current will be below 10 amps.

A low inductance DC motor,pulsed at low frequency,has current surges on a par with the stall current. If you can’t change the esc frequency you can add a series inductance to smooth out the current demand to a flat,average value.
9 April 2009 at 10:48 #20071
Telstar
Participant
@telstar
Hi A different look at the problem, do you have any form of suppression on the motor? is the radio equipment close to the motor?

Interferance from the motor brushgear sparking can cause problems.

Just a thought Tom
9 April 2009 at 15:21 #20075
Queequeg Quint
Participant
@queequegquint38270
Thanks. Here’s a video I took. You can hear how the motor sounds. It was hard to hold the camera and the radio so that’s why the picture is so unsteady.

The motor does have complete supression. I also moved the radio reciever far away from the motor. I put some gear grease on the metal gears, and that solved the problem but only for a while. In fact, after I put gear grease on, it ran perfect. I ran boat for about 30 minutes, then it started stuttering again.

Also, the motor does not get too hot. Just a little warm.

I really don’t know much about “series inductance” or a choke and toroid. So, if a different ESC would solve the problem, I would go that route. I like the motor (when it works) so I would like to keep that. Unless maybe the motor itself could be defective???

Here’s the link to the video.

There’s a few other youtube videos by “OrcaBoat3” that were taken when the boat was working perfect. This link is a video of when it is stuttering a lot:

http://www.youtube.com/watch?v=LQp9jz8XCug&feature=channel
9 April 2009 at 16:59 #20079
60watt
Participant
@60watt
Motor sounds fine to me.The high pitched whine suggests it is happy.

That and the moderate temperature tells me you could go down to six volts and fit a bigger prop to compensate.That will halve the stall current.

The esc is OK too it just won’t tolerate your kooky arrangement .

I guessed you fitted 3 capacitors to the motor.The two capacitors to the motor case don’t filter out anything unless you lead a wire back to the supply negative.Better still,connect that to the water via metal fitting.
9 April 2009 at 17:40 #20080
Queequeg Quint
Participant
@queequegquint38270
Thank you.

Yes, the motor has 3 capacitors which came attached in the fashion you mention. Unfortunatley, I cannot put a larger prop on the boat becuase there is not enough space.

So, if I understand you correctly: To make everything happy, (and I keep the motor, 12 volt battery, and prop) then I change the ESC to a higer aperage? Mtroniks makes ESCs at 15amps, 20amps, 25 amps, and 40 amps.

If you have any better ESC reccommendataions, let me know!! Thanks.
9 April 2009 at 18:03 #20081
60watt
Participant
@60watt
The fact you have a gearbox and the motor is in the high audio frequency and motor temperature tells me your average current is low.Your peak current is high because the esc is a low frequency type driving a low inductance motor.The addition of a choke will smooth out the peaks.
9 April 2009 at 19:11 #20084
Queequeg Quint
Participant
@queequegquint38270
Thanks. Can you tell me how to install a choke?
9 April 2009 at 19:52 #20087
60watt
Participant
@60watt
It is just an extra 12 inches of wire in series with the motor.Break open one of the esc to motor cables.

You wind about 10 to 40 turns of 1mm square (=10 amp) enameled copper wire round a Nickel Manganese or powdered iron toroid.That should give a 10 to 100uH inductor.The formers that fit over USB and peripheral dc power cables are ideal.

I’m not even going to mention saturation….oops
10 April 2009 at 03:36 #20095
Queequeg Quint
Participant
@queequegquint38270
All this sound very complicated and difficult. Do you think that a different ESC would solve the problem altogether. And if so, what one would you reccommend? Thanks so much for your time!!!
10 April 2009 at 08:32 #20101
60watt
Participant
@60watt
I sent you a message of where and what to get but this case only calls for a 50p Nickel Manganese ring core.Do you live near a Maplin or R.S. counter?

P.S.

Maplin do free delivery till Tuesday but ,honestly, it is a 20p ring core

http://www.maplin.co.uk/Module.aspx?ModuleNo=3631

Edited By 60watt on 10/04/2009 09:03:30
12 April 2009 at 23:33 #20175
Dave Milbourn
Participant
@davemilbourn48782
It’s more usual to use a 6v supply through that motor and gearbox, especially with a prop of the size you have fitted. The 6:1 combo is generally recognised as the 12v one.

MFA quote a typical current draw of 2.8A for this motor, so you should not require anything more than a 15A ESC – if that.

A 6:1 Torpedo ran very nicely on 12v through an ACTion Condor 20A ESC in my Envoy (I just happened to have one spare), and that’s a big brass prop and moved a lot of water. Nothing got remotely warm and certainly the motor didn’t stutter.

There are other manufacturers of electronic speed controllers than MTroniks and Electronize, you know

Dave M
14 May 2009 at 01:48 #20853
Queequeg Quint
Participant
@queequegquint38270
Problem solved! (I think…) I loaded the gear box with petroleum jelly. That took away the stuttering. Somehow, the metal gears (which are bolted drectly to the motor), cause some kind of electic interference. I pulled the motor out and held it far away from the receiver. But it still stuttered. Upon loading it with grease, the stuttering went away.

Anyone ever have that problem before???
14 May 2009 at 01:48 #20854
Queequeg Quint
Participant
@queequegquint38270
Problem solved! (I think…) I loaded the gear box with petroleum jelly. That took away the stuttering. Somehow, the metal gears (which are bolted drectly to the motor), cause some kind of electic interference. I pulled the motor out and held it far away from the receiver. But it still stuttered. Upon loading it with grease, the stuttering went away.

Anyone ever have that problem before???
14 May 2009 at 03:28 #20856
60watt
Participant
@60watt
All the time,but don’t blame the gears.
20 May 2009 at 01:14 #21007
Queequeg Quint
Participant
@queequegquint38270
Well, the stuttering came back. So…. I did an experiment. I put 3 more capacitors on the motor (for suppression), and the stuttering was substantially reduced. Then, I put another 3 capacitors on the motor. Stuttering is now eliminated. I ran the boat for over one hour and it ran perfect. So, I have a total of 9 capacitors on the motor!!!! Is this OK???

What exactly do the capacitors do??

One thing, after running the boat full throttle for almost an hour, the motor was very very hot. But not hotter than any motors I’ve used before on RC cars.

The other thing, full throttle didn’t seem as fast as before I put on the other 6 capacitors, but it seemed only a little bit slower.
20 May 2009 at 03:42 #21009
60watt
Participant
@60watt
You are doing exactly the same job as the choke by adding high value capacitors.You are not adding rf suppression but you are filtering very high current switching spikes which causes the esc to shut down.That is why I suggested to contact the manufacturer to say if the 15 amp one is suitable for a geared 540 on 12.He could tell you if he has tested his esc on that with success.

You could have got a single 1uF polyester capacitor and soldered it between the brushes. Forget about putting any more from terminals to the case.

The grease helps by lubricating the gears.

Where do you see sparks other than on the motor brushes? Certainly not on the gears.
20 May 2009 at 17:35 #21018
Queequeg Quint
Participant
@queequegquint38270
Now a new problem. Yesterday, the boat ran fine. Full throttle for almost an hour! Motor was a bit hot, but not too hot.

Anyway, I recharged the battery (12V, 12AH) overnight with a charger that switches to trickle when it’s fully charged.

Today, I ran the boat. Everything looked and sounded great. But after about 20 minutes, my full throttle got quite a bit slower.

I brought the boat in. Opened the hood and I could feel the heat coming off the motor and it smelled like it was burning! I wet my finger and touched the motor and the water boiled away right before my eyes!

Speed control was nice and cool. (it’s now Mtroniks Viper Marine 20 amp… I accidently ruined the 15 amp one…don’t ask me how but I killed it)

So, something has happened between yesterday and today that has caused the motor to get super hot.

-Maybe something wrong with the battery? the motor? could the extra capacitors be messing it up? oh man!!!!
20 May 2009 at 18:14 #21021
60watt
Participant
@60watt
Plenty of info but the other information listed below would help.

What kind of capacitors were they? A capacitor failure could be a low resistance short.

If you can’t tell the capacitor type and values what are the shapes and what are the numbers.

Did you have a fuse and is it possible to connect the esc with the wrong polarity?

If the capacitors were ceramic types 10nF to 470nF from motor suppression kits they were not to blame.

What does the esc blurb say about short circuit protection? What do you use for rudder servo and receiver power?

Do you have a multimeter in your toolkit? They can be obtained for a few pounds and can tell you quite a lot. For example you can tell what current you are drawing.Whether or not your drive train is seizing. but motor revs tell you that. With no ventilation the motors will get hot but,from here,we can’t tell what current you are drawing so what battery capacity do you have and how long does it last.?

One last thing. When you had trouble before was there any sign of the rudder misbehaving or was it purely the esc cutting out on its own?

That is not relevant here but it points to whether the esc was previously cutting out or interference was feeding back to the receiver.The choke I prescribed would solve both kinds of issue.

Are you not near a model boat club with somebody technically minded ? It is easier to pick up things

How did you kill the last one?

Edited By 60watt on 20/05/2009 18:15:56
20 May 2009 at 20:37 #21029
Queequeg Quint
Participant
@queequegquint38270
Thanks. The 6 extra capaciators each say 503 on them. The other three are from MFA, one is larger and say 224Z, the other two say 104.

Well, I thought maybe there was too much grease in the gears, causing the gears to jam, thus putting a huge load on the motor. So, I went in and took out most of the grease and guess what? It worked! Boat was slightly faster and I got about 45 minutes run time out of it at full throttle.

When I brought her in, I saw smoke coming out from under the hood. Opened it up and a cloud of white smoke came out!! Motor was super super hot! Worse, the plastic gear box melted right into the gears!! The motor was so hot that even the solder on the motor was melting away!!!!!!

When I had trouble before, the rudder was fine. No odd behavior.

My battery is 12 volts, with 12 Amp hours. It is heavy, about 10 pounds. At full throttle, when the boat is working, I get about 45 minutes with full throttle being true full throttle; then it starts to slow down.

The motor is in a place which gets little or no ventilation. Should I change that with a fan or something? I have a little fan blowing on the ESC all the time. I use the BEC on the ESC to power the rudder servo, radio, fan, and lights (which I can switch on and off from the transmitter). ESC is correct polarity; but I don’t have a fuse in there.

The last ESC was killed by accident. I was doing some wiring work when I accidently put some wire where it shouldn’t have been. A huge spark went up in the air and then my ESC lost it’s ability to go reverse. I tried all kinds of things to reset it but it didn’t work.
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