Model Boat Mayhem
Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: captain ron on June 04, 2013, 11:55:48 pm
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I've got a pair of MFA 6 to 1 motors in a tug boat. They both sound different and the speed is different.
There running of 1 No 12v 9aH battery. Speed controller on each motor.
When I push both throttles forward they start together but as I keep pushing the sticks forward the one motor just goes faster. Its the same in reverse.
I've tried changing round the speed controllers but its just the same.
Are these motors prone to have a different speed .
Hope someone can help.
Ron
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Ron......with the original setup...we assume one motor turns clockwise & the other counter clockwise... so this could be where your original [speed/sound] variation is from
One way to prove or disprove is connect the second motor for the same rotation with the first
I am not familiar with the MFA geared motors you mention, but motor vehicle ventilation fan motors & wiper motor motors are designed with a single ball as a thrust race/washer....so when you reverse the motors from their intended rotation, back EMF occurs as the shafts bounce off the thrust ball.... >>:-( & the result is different speeds & sounds in reverse.........Derek
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Derek, I've tried something else since the last post.
I tried the battery direct to the motors and both operate at the same speed. Even if I swap the wires the motors go at the same speed in reverse.
But cant understand when I swopped the speed controllers from one motor to the next its still the same motor that sounds diff and is slower
both forward and reverse.
I'll swap the speed controllers to 2 new ones and try again
Also I'm using Action fuse holders between the motor and speed controllers.
Ronnie
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Ron......I noticed that Components Shop [now including ACTion] sell MFA motors....however you have not mentioned specifically which 500 series motor or which brand of speed controller's you are using
Possibly a note to DM [inertia] may pay dividends...as something appears to falling into that BLACK hole <*< of naughty misunderstood electrons...... Derek
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If the same motor runs slower on both ESCs then the problem, if that's the right word, is the motor and not the ESCs. These are not exactly the highest quality motors made (with all due respect to MFA). The armatures are possibly hand-wound on converted treadle sewing machines by Chinese outworkers for ten cents apiece. As such the number and even the thickness of the windings will vary quite a lot - QC not being trendy in the ROC - and this will create variations in back-EMF. This is the reverse voltage generated when a motor is switched on and off, which is the way modern speed controllers work. The more back-EMF there is then the slower the motor will run. In contrast, if you have two ESCs of the same make and type then the likelihood of significant variations on their outputs is very low.
Moral? Change the motors, not the ESCs.
Suit yourself.
DM
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OR... you say when you push both sticks forward. Do you have one motor on the left stick and the other on the right stick of your transmitter? If so, check that your non-ratchet stick doesn't have a dual rate switch restricting its travel. If unsure, plug a couple of servos into the same sockets and see if they both have the same angle of travel forward to astern, if not, dont blame the motors :-) and turn off your dual rate.
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OR... you say when you push both sticks forward. Do you have one motor on the left stick and the other on the right stick of your transmitter? If so, check that your non-ratchet stick doesn't have a dual rate switch restricting its travel. If unsure, plug a couple of servos into the same sockets and see if they both have the same angle of travel forward to astern, if not, dont blame the motors :-) and turn off your dual rate.
Also if you have a more modern TX with extra bells n whistles you could look check the end point adjustment/servo travel
This could be a screw pot somewhere on the TX (for example the Hitec Lazer 6 has the epa adjustments recessed on the front panel) or in the menu if its a computer type transmitter
what type of Transmitter are you using?
Also what type of speed controllers? could be that they need setting up
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To all,
Thanks for your input.
I changed round the motor channels on the receiver and the problem was now transferred to the opposite motor.
The problem is the R/H stick on the TX.
Its a Futaba skysport 6 .
Ron
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have a nose throught the manual and look for servo limits or end point adjustment
http://manuals.hobbico.com/fut/6va-manual.pdf (http://manuals.hobbico.com/fut/6va-manual.pdf)