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Pablo's FK motor skewed brush orientation experiment


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#1 Pablo

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Posted 07 February 2018 - 08:05 PM

This is part humor, part science. Part serious, part jest.

The fact is, many have complained the brush orientation on this type motor is wrong.

 

My theory is, let's not be so narrow minded to assume what we have been taught about traditional brush orientation applies to these motors. It may. Or it may not. I haven't seen anybody actually test it yet.

At least, not publicly.

 

JK has officially announced it's intention to make it happen. But no mention has been publicly made to announce a successful test of the theory. JK is a smart company. I doubt they would announce an impending change like they did without testing it first. But I'm just guessing.

 

To put it another way, two possibilities:

 

- The Chinese screwed up and don't understand brushes must conform to the curvature of the commutator.

If this is true, there is a big performance gain to be had by fixing this problem. In which case, JK is on track.

 

- These Chinese motors don't adhere to common motor theories. Well, that may, or may not, be true.

 

Let's just disassemble one of these motors and see what I can do.

I have nothing to lose :crazy: Here we have an old, junked, Falcon 7.

 

IMG_8378.JPG


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Paul Wolcott




#2 airhead

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Posted 07 February 2018 - 08:11 PM

​I have to believe the Chinese put the brushes in side ways for a reason, they just won't tell us why.


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#3 MSwiss

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Posted 07 February 2018 - 08:13 PM

FWIW, Bryan tried some factory(?) experimental Falcon 7s, about five years ago, with the correct brush orientation.

 

For whatever reason, they did not perform well.

 

Maybe you'll have better luck.


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Mike Swiss
 
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#4 Pablo

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Posted 07 February 2018 - 08:25 PM

I'd like to see Bryan's info.


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#5 gotboostedvr6

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Posted 07 February 2018 - 09:46 PM

The FK130 brushes are oriented in the "wrong" direction purposely to guarantee motor start-up. Due to the simple design of the endbell and brush hardware it would be impossible to properly line up brushes if turned in the correct direction.

A design change that would help reduce break-in and tighten up motor speed differences would be to have the brushes manufactured with flat faces which would eliminate uneven comm wear.


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#6 Mark Wampler

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Posted 07 February 2018 - 10:34 PM

FWIW, Bryan tried some factory(?) experimental Falcon 7's, about 5 years ago, with the correct brush orientation.

 

For whatever reason, they did not perform well.

 

Maybe you'll have better luck.

 

Franken motor race. 


You can quote me.

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#7 Bryan Warmack

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Posted 08 February 2018 - 01:32 AM

Mike and Pablo,

I've taken dozens of these FK type motors apart over the years to inspect nearly every internal part but I've never did any testing with reorienting the brush alignment... I probably would have if I thought it would have made any difference but from the beginning out here and dealing with the old TSR D3 motors for years I found the "misaligned" brushes made no difference whatsoever in performance. The TSR D3 motors required no break-in and ran just as well with the two little contact points on the commutator as they did when the brushes were fully broken in. I TQ'ed at a Checkpoint with a brand new motor with no break-in. 

The JK Hawk Retros are certainly different in regards to break-in and with harder brushes but I've seen winning cars out here with Hawks that had comms that didn't show a full brush track!....
 
I agree 100% with David Parrotta's view about the flat brushes. I've still never seen a conclusive explanation why the brushes were oriented like this in the first place but I have seen pictures of very large similar motors from decades ago with the misaligned brushes.


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#8 usadar

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Posted 08 February 2018 - 02:11 AM

When I visited a DC motor manufacturer in Tokyo, I asked this brush orientation issue of FK(130) motors to their designer.
He told me the present orientation is right and on purpose.
Those motors are originally designed for moving door mirrors or display monitors of cars.
The less contact between brush and comm makes the less friction.
If brushes were seated perfectly on comms, motors would have more troubles and much shorter life.
Those motors are designed to run less than 8,000 RPM at 12 volt while slot car motors run 40,000 to 50,000 RPM.


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Haruki Kan
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#9 Fast Freddie

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Posted 08 February 2018 - 12:15 PM

Everybody who races these motors knows that the slot car industry isn't their only customer so you can understand where Haruki is coming from.  The motor builder is going to satisfy the parameters required by their most important customer. We are not them. The problems that have cropped up with the FK motors is there by our own doing, we are exceeding the design specs of the motor. Now deal with the problems at hand.

 

I have recently undertaken the two-speed problem. I have tried several FK motors in various stages of brush seating and the problem never seems to go away. I have a H7 that I have put through some real abuse to see if there is a point where the two-speed problem goes away. I haven't found that point yet. This motor has been run for long periods of time at different voltages and the brushes are half worn and fully seated and the problem is still there. This motor has one balance mark on the arm.

 

I have come to the conclusion that the two-speed problem is a result of resonance vibration. In the Navy I was an Engineman and I learned that every rotating motor or rotating piece of machinery has this resonance vibration point. Our fire pumps used electric motors that were very well balanced but at certain points you could hear and feel the vibration, mainly at the lower RPM. That's because the armatures were balanced for the operating RPM range. Once they reached that area they were as smooth as silk. I think that's what is happening here. If these motors have a normal operating range to 8,000 RPM, as Haruki said, then they aren't going to show consistent vibration free operation to 40,000+ RPM. The resonance vibration will appear somewhere between 8.000 and 40,000 RPM.

 

So now I'm thinking "why break-in the brushes at all"? The springs are stronger when the motor is new, the brushes are making limited contact with the comm resulting in less friction loss and longer motor life. Maybe Bryan is right, run them right out of the pack or at the very least follow the manufacturer's break-in instructions.   


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#10 Pablo

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Posted 08 February 2018 - 06:06 PM

Appreciate the input, gentlemen, but let's try and not get any more serious than the situation calls for.

I don't have sophisticated tools to create a complex experiment. Let's just have fun.

I have two FK type motors, I'll call them Foghorn and Leghorn.

 

Foghorn is a well worn original Falcon 7, dug from the bowels of my junk collection.

You can see the metal bits I fished out of it, and I'm sure once opened there will be more :laugh2:

Foghorn's only remaining purpose in life is to show me the basic construction so I'll know what to expect once I open up Leghorn. Ruining something is the best way to understand it sometimes :laugh2:

 

IMG_8394.JPG

 

Leghown is a JK Hawk 7 marked "7777777777" and "H7 Made in China".

Purchased new recently and tested in a JK C11 GTP race car twice.

A real dog. No "two speed", just one speed - dull.

 

 IMG_8395.JPG

 

I ruined the endbell nubs on Foghorn with a Dremel 409 cutoff disc

 

IMG_8397.JPG


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Paul Wolcott

#11 Pablo

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Posted 08 February 2018 - 07:35 PM

Jackpot - Foghorn had three set screws inside :dance3: :crazy:

IMG_8399.JPG

 

Just for the record, Foghorn magnet hole was .550 and the front ends were .352 deep in the can.

Actually, one miked at .352 and the other at .353. That is a tight quality control tolerance, son :good:

Not only are they secured with clips, they appear to be superglued to the can.

Arm OD is about .517

 

I dropped some metal shavings in there to perform another side experiment

 

IMG_8402.JPG

 

Koford magnet Putty is great stuff, but if you need to clean some magnet shwarf, try NEON.

99 cents. Works better than Play-Doh

 

IMG_8404.JPG

 

I was "Oddly Satisfied" with the head-to-head test against the Play-Doh :D


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#12 Pablo

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Posted 08 February 2018 - 08:17 PM

I have no experience being a "motor cheater" so I beg ignorance here.

Now maybe you understand my need to employ Foghorn as a "pre-test monkey" :)

 

The right way to pull the endbell off is grab the shaft and pull as shown here.

The wrong way is to grab the bushing housing like I tried at first.

You can see the gall marks from my erroneous first attempt.

Nobody is completely useless - you can always serve as a bad example :D

 

IMG_8407.JPG

 

 


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#13 MSwiss

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Posted 08 February 2018 - 08:27 PM

On motors, without much of a shaft sticking out, you can push down, on the pinion end.

Mike Swiss
 
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#14 Pablo

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Posted 08 February 2018 - 08:45 PM

Yup, I did a little of can end tapping as well, Mike.

Now we have a clear view of the (alleged) wrong brush orientation on Foghorn

 

IMG_8415.JPG

 

Why Foghorn was residing in my junk box is a mystery, since it obviously hasn't seen much duty.

I can't explain that, but for the purpose of my experiment, it doesn't matter.

 

This is where things may get a little serious, as I have to decide possible courses of action.

That's all for tonight :)


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Paul Wolcott

#15 Bill from NH

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Posted 08 February 2018 - 08:58 PM

Poster putty (for hanging posters without damaging your walls) is quite similar to the Koford magnet putty. In the days of old, before these putties, I would  use a q-tip & coat the magnets with red Stick-it. When I cleaned the Stick-it off with lighter fluid, any magnet swarf was also washed away. I was real handy when we had to sand magnet faces & backs to straighten them. 


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How old should a highway be before you tell it, that it has been adopted?


#16 Pablo

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Posted 08 February 2018 - 09:19 PM

Cool, Bill. But, is it "shwarf", or "swarf"? :D


Paul Wolcott

#17 Bill from NH

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Posted 08 February 2018 - 11:33 PM

Swarf = fine chips or filings of stone, metal, or other material produced by a machining operation.

 

Shwarf= a term coined by dwarfs, meaning a dwarf shorter than the average dwarf.


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Bill Fernald
 

How old should a highway be before you tell it, that it has been adopted?


#18 Pablo

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Posted 09 February 2018 - 06:33 PM

Bill, would you call the Chicken Hawk in this cartoon a "Shwarf"? :roflmao:

 

 

Arm removed, brush legs cut. They are 4 thou thick and I'm guessing it's copper.

The brushes are a wedge fit and pop right out.

 

My first idea is to make my own legs with the brush slot oriented "correctly", long enough to overlap the existing nubs and solder them back on. I used 4 thou brass and JB Welded them in place.

 

Once dry, I'll trim the brass legs and solder them in. We shall see........

 

IMG_8429.JPG


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Paul Wolcott

#19 Bill from NH

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Posted 09 February 2018 - 07:55 PM

Looks like a rooster to me. :laugh2:  Are you re-engineering Chinese engineering? It's much easier to work on 16Ds. :)


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Bill Fernald
 

How old should a highway be before you tell it, that it has been adopted?


#20 Pablo

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Posted 09 February 2018 - 08:36 PM

Good point, Bill :good:


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#21 Pablo

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Posted 09 February 2018 - 09:08 PM

Meanwhile, back at "The Ranch", Leghorn draws a steady .40 amps at 3 volts.

No surprise here, just a noted performance baseline, as Leghorn has already been well broken in.

 

Amp draw provides a window into motor health, no matter what type.

It's a window that has to be interpreted by experience.

It's not pure science - it's part black art. That's the magic.

 

A motor that draws more amps at a specific voltage compared to another motor of same type may indicate:

-a problem, such as, a short, or a bind

-a superior performer

 

The problem motor usually shows it's sickness in a hot running condition.

Tricky part is, better performing motors usually run warmer than tame motors.

Friction creates heat.

 

The superior motor produces better lap times and runs cool enough to not cook.

Tricky business for sure. If this was easy, your sister would be doing it :)


Paul Wolcott

#22 Bill from NH

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Posted 09 February 2018 - 09:30 PM

Years ago I bought a Koford C-can motor kit that had a Grp. 12 arm in it. I built the setup, but the arm drew more amps than volts. It quickly got so hot, you needed gloves to pick it up. Defective from the start. I put a Proslot X-12 in that motor & it ran great. I won't mention that I never ran my two Koford Competitor arms.


Bill Fernald
 

How old should a highway be before you tell it, that it has been adopted?


#23 MSwiss

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Posted 09 February 2018 - 09:44 PM

Dave Crevie PM'ed me to remind me he did virtually the same experiment, for Jerry Kulich, about 5 years ago.

 

To quote him,............"The motors ran cooler and a bit faster with the brushes oriented as they come".

 

Part of the issue with your experiment is the brushes are not square, so you are not just changing the curvature, but also changing the wraparound.


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Mike Swiss
 
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990)
Eight-time G7 King track single lap world record holder
17B West Ogden AveWestmont, IL 60559, ( 708) 203-8003
mikeswiss86@hotmail.com (also my PayPal address) 
Note: Send all USPS packages and mail to: 5858 Chase Ave., Downers Grove, IL 60516
Make checks out to Chicagoland Woodworking, Inc.


#24 Jaeger Team

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Posted 10 February 2018 - 06:07 AM

I love that microsurgery operation! In my opinion you need a tool with the same diameter as the comm to reshape brushes.


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#25 Pablo

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Posted 10 February 2018 - 10:17 AM

the brushes are not square, so you are not just changing the curvature, but also changing the wraparound.

Concur - I hadn't thought of that. But the show must go on :)


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