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PS4002FK amp draw (and "oddity")


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#1 Tex

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Posted 09 November 2017 - 11:54 AM

OK, so I broke in two PS4002FK's on the power supply, to get the brushes fully seated. One motor draws 1.2x amps and the other draws 2.4x amps. Is that a normal variance with these motors? Anyone have good/bad to say about the one drawing 2.4x amps?

 

Now, for the "oddity". It just so happens that the motor drawing 2.4x amps is tapped out for screws of a different size than I'm used to using on these motors!?! I've always used 2mm x 4mm screws. I was installing the motor in my F-1 chassis and kept turning the wrench, and turning and turning and turning, etc. Is it stripped out?! I pulled the motor out of the chassis and had me a closer looksee.... my 2mm x 4mm screw just dropped right into the hole, all the way! The can is obviously tapped for a larger screw. Anyone else ever encounter this? I tried another size and it was too large for the can. Fortunately, I had two(and ONLY two!) self-tapping screws to mount the motor.


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#2 gotboostedvr6

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Posted 09 November 2017 - 12:36 PM

You should send me the one drawing 2.4 amps so I can dispose of it properly.

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#3 Eddie Fleming

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Posted 09 November 2017 - 12:46 PM

I would like to add on to Richards question.

 

Do you use amp draw as an indication of performance of these Pro Slot or RH motors, and do you find it to indicate on track performance?


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#4 Ramcatlarry

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Posted 09 November 2017 - 01:20 PM

bet that one did not come in a blister pak.


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#5 CoastalAngler1

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Posted 09 November 2017 - 01:48 PM

Did you check the hood alignment?  These 'sealed' motors need work.  :sarcastic_hand:


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#6 crazyphysicsteacher

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Posted 09 November 2017 - 01:54 PM

Make sure the can end of the motor is flat and not tweeked.  I have found some to be tweeked and will lead to the high draw.  If the hoods are not lined up, they can cause a high draw as well.  The other issue is if the brushes were bad and they loaded up the comm real good but you are too good for that one.  Also make sure the endbell bushing is pressed all the way into the end bell.  If it is cocked a little, that can lead to the high draw.  Otherwise, hook up the power and let that thing go.  Just remember, it may be faster than you can handle.  If it scares you, I can supply a good place to put it. 😉😎😏


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#7 DOCinCocoa

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Posted 09 November 2017 - 04:09 PM

To answer your first question: Yes.

 

I have 10 Pro-Slot FK motors. The amp draw varies a lot. At 6V on my Trinity motor machine, I see a low of 0.94A and a high of 1.73A. These values are all with the stock PS brushes and springs. No changes to the spring tension. The amp draw is greatly dependent on the spring tension and the state of how well the brushes are broken in. Not the mention the applied voltage.


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#8 Frankie Schaffier

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Posted 09 November 2017 - 07:37 PM

I received some PSFK motors not in the blister packs that were from a bulk shipment for handouts with stripped out threads also. I just used them in solder in cars.
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#9 NSwanberg

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Posted 10 November 2017 - 04:20 AM

I have had two out of 14 PS-FKs that the motor screws would not work with 2 mm screws. One I got 2-56 screws to hold. The other one had to be used in a flexi car and was soldered in place. Such is life for $14 motors.


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#10 havlicek

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Posted 10 November 2017 - 06:41 AM

 

 

OK, so I broke in two PS4002FK's on the power supply, to get the brushes fully seated. One motor draws 1.2x amps and the other draws 2.4x amps. Is that a normal variance with these motors? Anyone have good/bad to say about the one drawing 2.4x amps?

 

 

Do you use amp draw as an indication of performance of these Pro Slot or RH motors, and do you find it to indicate on track performance?

 

Current draw isn't a performance indicator.  It's a measure of how much "input" a motor needs to do what it's doing.  If two of the "same" motors have the "same wind", and one is drawing more current at the same voltage...it could very well be that the one drawing more current has a problem, rather than being a "hotter" motor.

***Take a motor and run it at low voltage on a power supply while reading the current draw.  Now pinch the shaft to put a load on it while it's spinning and watch the current draw go up.  The load you're applying "could" be an analog for a bound-up bushing, a tweaked can etc.

Other things can increase current draw and be really bad too.  If one or both of the brushes are bouncing, that will cause arcing which will lead to higher current draw also...and burning of the com.  Brushes can be seated as well as possible, but an out of round com, bad end bell bushing, an untrue shaft, too weak spring or springs can all prevent the brushes from staying in good contact with the com and cause arcing.  Then too...just bad brushes (they vary) can cause current draw to go up and make a motor run like doodie.

Picking a good motor by looking for high current draw is a crap-shoot.  It *might* work (?) sometimes just by luck I guess.


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#11 Fast Freddie

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Posted 10 November 2017 - 11:11 AM

One more thing you need to be aware of with the PS4002FK "sealed" motors.  The arm sometimes tends more to the endbell and sometimes it tends more to the can bushing.  Rarely are they centered in the magnetic field.  I have had motors where the arm has tended excessively in one direction or the other.  In either case the excessive friction caused by the constant contact of the arm with the arm spacers pressing against the bushings can create frictional drag that could give a higher amperage reading.  Similar to when you hold the arm shaft with your fingers when the motor is running.  I have tried several things to reduce this frictional loss from attempting to shave a small amount of material from the small brass washer on the arm to cutting and removing the white spacer, both of which sometimes worked sometimes did more harm then good.  I have recently gone to soaking the white washer with synthetic oil and that seems to work best.  One more thing that is definitely a must is to glue in the endbell bushing.  In every one of these motors that I have had the endbell bushing was either loose or could be easily pushed toward the comm.  Gluing it in place is a must.  


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#12 havlicek

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Posted 11 November 2017 - 06:37 AM

For sure Fred is correct!  Anything getting in the way of an arm spinning freely in the setup (*and not being centered is definitely one of those things) will be "seen" by the arm as a load, and cause current draw and heat to rise.  Most all of these little motors have strong magnets too...even the ceramics are very strong for what they are, and the poly neos significantly stronger still, let alone the ones with the solid neos.  The stronger the magnets are, the more force they can exert by pulling/pushing the arm against either the can or end bell bushing.  Heat in a motor can be thought of as "waste" or inefficiency.  The motor is turning  electrical energy into kinetic energy...and (unfortunately) heat or thermal energy.  We're not looking to warm ourselves using motors so that heat is "waste".

I think (*the physicists among us can correct me if I'm wrong) that a 100% efficient motor would run dead cool if such a thing existed.  We tend to overlook the heat issue as long as it is manageable and the motor is doing what we ask of it...until it blows up :)


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#13 Kim Lander

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Posted 11 November 2017 - 07:41 AM

Sounds to be the higher draw motor is bound up some where be it ever so slight, ...hook motor up to leads and watch the arm when you put voltage to it, it just might jump towards the endbell or the can end......then slightly squeeze the can on all sides, and see if there is a change in readings and SOUND of the motor......good luck, because unless you can BLUE PRINT the motor it is a crap shoot.


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#14 old & gray

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Posted 11 November 2017 - 08:48 AM

Heat in a motor can be thought of as "waste" or inefficiency.  The motor is turning  electrical energy into kinetic energy...and (unfortunately) heat or thermal energy.  We're not looking to warm ourselves using motors so that heat is "waste".

I think (*the physicists among us can correct me if I'm wrong) that a 100% efficient motor would run dead cool if such a thing existed.  We tend to overlook the heat issue as long as it is manageable and the motor is doing what we ask of it...until it blows up :)

I’m not a physicist, but I am an engineer. I learned my first lessons of slot car motors from my high school physics teacher.

 

The laws of thermodynamics are what you are thinking about. These laws govern the change of energy.

The first law is no system can produce more energy than is put in.

The second law is any conversion of energy will result in a different form of energy and waste heat.

 

To restate these laws as the laws of gambling:

You can’t win;

You can’t break even;

Everyone has to play the game.


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#15 havlicek

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Posted 11 November 2017 - 04:48 PM

 

I’m not a physicist, but I am an engineer. I learned my first lessons of slot car motors from my high school physics teacher.

 

The laws of thermodynamics are what you are thinking about. These laws govern the change of energy.

The first law is no system can produce more energy than is put in.

The second law is any conversion of energy will result in a different form of energy and waste heat.

 

To restate these laws as the laws of gambling:

You can’t win;

You can’t break even;

Everyone has to play the game.

 

 

Well, I'm neither a physicist or an engineer...I didn't even stay at a Holiday Inn last night :)  Anyway, there is no 100% efficient motor (*or maybe even mechanical system of any kind I'm guessing).  All we can do is try to diminish the losses within our control.

 

 

 

Sounds to be the higher draw motor is bound up some where be it ever so slight, ...hook motor up to leads and watch the arm when you put voltage to it, it just might jump towards the endbell or the can end......then slightly squeeze the can on all sides, and see if there is a change in readings and SOUND of the motor......good luck, because unless you can BLUE PRINT the motor it is a crap shoot.

I guess so Kim, but that's only a guess.  I *think* that there's a little confusion here between motors that are "supposed" to draw more current because of hotter winds.  We generally see those as "faster/better" motors.  Then there are motors that aren't supposed to draw more than a certain average amount of current (*a "range" of readings), and then when one is drawing more than the average, it might be seen as a "faster/better" motor.  These things are cranked out in some factory over in Asia to meet a price point, so there are other variables that can make a particular motor a better performer or a "dog".  Slightly different timing, slightly different wind patterns because of simple "chance", poor OR better-than-average alignment, better or worse balance.  

So it's at least *possible* that a higher amp-draw motor IS a better performer, by simple luck...I think.  I sure wouldn't be looking at high amp-draw as a predictor of a better motor is all I'm saying.  Honestly, I still don't see any better way to be sure other than actually putting the motor in a car and running it on the track.


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