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Hawk 7 fast after it warms up - any idea why?


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#26 MSwiss

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Posted 12 February 2017 - 10:21 AM

Big thanks, Mark.

Mike Swiss
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Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
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Two-time G7 World Champion (1988, 1990), eight G7 main appearances
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#27 MarkH

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Posted 12 February 2017 - 10:37 AM

Copy, I will box and send this week.


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Mark Horne

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#28 Samiam

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Posted 12 February 2017 - 11:11 AM

This is how it should be done.
 
Mud ducking on social media is useless and solves nothing.
 
Brian's idea of swapping out parts to isolate the culprit is a good idea. It would also work with the push start 4002 FKs.
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#29 MarkH

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Posted 12 February 2017 - 11:15 AM

Yes, sir.
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Mark Horne

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#30 Randy Tragni

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Posted 12 February 2017 - 09:41 PM

I'm guessing that TonyP is right but if not it could also be thermal expansion finally closing the brush hoods and making a better contact. You might want to measure with a digital VOM and see if there is a connection issue.



#31 MarkH

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Posted 16 February 2017 - 06:30 AM

Motors are going out USPS today to Mike and JK. Looking forward to your expert evaluation.


Mark Horne

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"Racing is life... everything else is just waiting." Steve McQueen - LeMans
There are only two things in life that make me feel alive. Racing is one of them.


#32 swodem

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Posted 28 February 2017 - 06:01 AM

...I tend to like the theory that when the motor heats up it is essentially softening the glue around the comm and allowing the timing to shift slightly. I've got no hard data to back up the "glue melt" theory but to me it seems a bit more likely than the spring tension theory.

 

I find that theory impossible to consider;

1. timing movement would have to be wild

2. how could it be so consistent

3. what weird force sneaks in and resets it as it cools?


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#33 MarkH

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Posted 28 February 2017 - 06:08 AM

I sent the motors off to JK and Swiss. When they have reached a conclusion, if one can be found, we will have a better idea what is really going on.


Mark Horne

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"Racing is life... everything else is just waiting." Steve McQueen - LeMans
There are only two things in life that make me feel alive. Racing is one of them.


#34 Racer36

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Posted 28 February 2017 - 11:47 AM

We had an erratic power situation with a RH up here and we finally figured out what was going on. The plastic bushing that holds the terminal and the brush internal was loose and the brush was dancing around on the comm. No idea if it was loose from production or if it was overheated during soldering, but at least we now know what was up.

No need for a federal investigation, just thought I would share what we found.

Cheers


Dennis Dominey

Lifelong half-assed slot racer


#35 swodem

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Posted 03 March 2017 - 12:26 AM

We had an erratic power situation with a RH up here and we finally figured out what was going on. The plastic bushing that holds the terminal and the brush internal was loose and the brush was dancing around on the comm. No idea if it was loose from production or if it was overheated during soldering, but at least we now know what was up.

No need for a federal investigation, just thought I would share what we found.

Cheers

 

I have pulled these motors apart, removed the armature and watched the brush arms while i torture the terminal with a soldering iron - they don't even waver or show any signs of distressing.

 

I don't believe the whole 'soldering the lead wires can change the brush tension' - no way. Not enough heat for long enough by a country mile.

 

And, the heat of an iron (400 degrees) isn't enough to mess with the metallurgy of copper or brass 

 

Next theory please...


Steve Meadows


#36 MSwiss

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Posted 03 March 2017 - 12:43 AM

I got in the motor and put it on the power supply.

Free reving, it didn't seem to change rpm as it warmed up a but.

I even hit it with a heat gun.

No change.

I took the arm out to meter it.

The arm, once I pressed it fairly hard, against the contacts, read normal across all 3 poles.

Whether it required any more pressure to get it to read normal, it's hard to say.

So, really nothing here.

Maybe Tim at JK will come up with something.

He was out of the country on business, so I doubt he's had a chance to look at it.

Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
Eight-time G7 King track single lap world record holder

17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)

Note: Send all USPS packages and mail to: 692 Citadel Drive, Westmont, Illinois 60559


#37 gotboostedvr6

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Posted 03 March 2017 - 10:42 AM

What about hot resistance readings
David Parrotta

#38 Racer36

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Posted 03 March 2017 - 11:00 AM

 

I have pulled these motors apart, removed the armature and watched the brush arms while i torture the terminal with a soldering iron - they don't even waver or show any signs of distressing.

 

I don't believe the whole 'soldering the lead wires can change the brush tension' - no way. Not enough heat for long enough by a country mile.

 

And, the heat of an iron (400 degrees) isn't enough to mess with the metallurgy of copper or brass 

 

Next theory please...

I did not maintain that an issue was created in the metal through soldering, just theorized that the plastic bushing may have been melted during soldering allowing  the brusharm to move around. With the motor on the power supply there was an obvious change in rpm and sound if you put pressure on the negative terminal. If you actually read my post you will see I refer to the plastic bushing.


Dennis Dominey

Lifelong half-assed slot racer


#39 MSwiss

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Posted 03 March 2017 - 11:15 AM

What about hot resistance readings

Thanks for deleting your tactless post and replacing it with the above.

 

I'll address the above question when I have more time.

 

I have a lot of track prep to do right now, for a GL ISRA race, tomorrow.


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Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
Eight-time G7 King track single lap world record holder

17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)

Note: Send all USPS packages and mail to: 692 Citadel Drive, Westmont, Illinois 60559


#40 gotboostedvr6

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Posted 03 March 2017 - 03:33 PM

Functions of erratic motor power output on FK motors ;

Measured resistance changing more then expected from room temp to Operating temperature on one or more poles, excessive TIR of the motor shaft, comm runout induced by the combination of shaft runout and unnecessary extra v block spacing or collet positioning during comm truing.

There are other things but I feel that these are the most overlooked.
David Parrotta

#41 swodem

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Posted 03 March 2017 - 03:48 PM

Functions of erratic motor power output on FK motors ;

Measured resistance changing more then expected from room temp to Operating temperature on one or more poles, excessive TIR of the motor shaft, comm runout induced by the combination of shaft runout and unnecessary extra v block spacing or collet positioning during comm truing.

There are other things but I feel that these are the most overlooked.

 

Wow you can Comm-true a Hawk 7 on your Hudy??

 

I think the above are things that may make a motor perform less than optimum, but not sure how they would make it erratic? Its more likely to be consistently poor


Steve Meadows


#42 swodem

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Posted 03 March 2017 - 03:49 PM

I did not maintain that an issue was created in the metal through soldering, just theorized that the plastic bushing may have been melted during soldering allowing  the brusharm to move around. With the motor on the power supply there was an obvious change in rpm and sound if you put pressure on the negative terminal. If you actually read my post you will see I refer to the plastic bushing.

 

I wasn't making my comments solely on what you posted, but the common theories that the brush arms get less 'spring' due to current and soldering heat....


Steve Meadows


#43 gotboostedvr6

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Posted 03 March 2017 - 04:17 PM

The manufactures that produce fk130 motors true the comm before assembly yes?

They use some method and my investigation has shown it is flawed right from the bag.
David Parrotta

#44 swodem

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Posted 03 March 2017 - 06:23 PM

I doubt it's trued like in a lathe
More like just formed round


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Steve Meadows


#45 JK Products

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Posted 05 March 2017 - 12:15 PM

HI Mark,

 

Sorry to be slow in responding, just getting unburied from being gone. We initially inspected the motor and could find nothing that looked bad (damaged or fouled commutator, etc.) before testing it. On the power supply, with two different loads, we couldn't find a significant change in performance after running for over 10 minutes at different voltages. Like Mike, we tried hitting it hard with a heat gun and again, no significant difference. Do you think it could have been something on the set-up of the cars? When you swapped out these motors, were the other motors fine? If yes, did you happen to put one of these motors back in and did you see them repeat the same change in performance? Was it only when the car was being raced that you saw this (maybe a track power supply change?)?

 

Sorry I can't be of more help but I can't find anything on my end. 


Tim Homola
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#46 MarkH

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Posted 05 March 2017 - 02:35 PM

We run 4 tracks in our series and I have a specific setup for each track. The motor was put in the car first for my track and then setup to run at a second track. It acted the same on both. About 20-25 laps from cold and came to life and was as fast as expected. Clean braid, good wires and solder and a free axle. I did bring it back to my track and run it one more time. 90 amp PS and 2 farad cap by my self.

It is a mystery and I am sure you would have preferred to find something so it could be addressed.

 

The last two H7 out of the bag have performed as expected with no issues. There is hope we will not see this issue for a long while.

Thanks for looking into it.


Mark Horne

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"Racing is life... everything else is just waiting." Steve McQueen - LeMans
There are only two things in life that make me feel alive. Racing is one of them.


#47 gatormark

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Posted 09 March 2017 - 08:24 PM

We run these cheap motors on a 200 ft engleman and everybody has seen the power jump. Now some that have com from a guy that's zaps them and breaks them in under water seem to be more consistent.


Mark Conner

#48 Big Booty

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Posted 11 April 2017 - 05:31 AM

Semi conductor materials have a negative coefficient of resistance.  e.g. Carbon, germanium silicon to name a few.  So hotter carbon brushes conduct better than cold ones.

 

Bare copper comms have a very high coefficient of friction.  Copper oxide coefficient of friction is a lot lower.  As the electrons jump off the brushes and onto the comm the arcing promotes an oxide layer to be formed.  The tension on the brushes then scrapes this layer away.  Too much tension and you scrap away all the oxide layer.  Not good.  Not enough tension and too much oxide layer forms.  Not good.  Get the tension jut right and you scrap away the same amount as you are making.  Perfect.


Rick Smith


#49 havlicek

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Posted 11 April 2017 - 06:01 AM

Seems to me that this is probably not an "issue" at all.  These are just inexpensive, but "high-value" (ie: performance/price is pretty impressive) motors built to a spec that allows racers to "use them and toss them".  That they run as well as they do at all for the price is remarkable.  That some of them may have quirks should be expected.

***People who build motors, even the high-end NASA-spec stuff, know that even a big budget and a lot of work still won't make every motor perform the same.  Sometimes, it just is what it is.


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#50 Tim Neja

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Posted 11 April 2017 - 08:55 PM

I've experienced slow cool motor and speeding up after it heats up with a few motors. I know a few others have seen this as well here at BPR>  I'd estimate it's been less than %2 of the what I've run.  None have been fast enough to race anyway---but it hasn't been a really unusual phenomenon! I'm  NOT complaining--I don't have any problem with the current  Retro Hawks and I hope Tim doesn't make any more changes! Bottom line--we are NOT going to get better motors than we currently have. There's going to be some manufacturing and performance variables in a $13 motor no matter what we do! We have them in $200 motors too!! Welcome to racing! :)


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She's real fine, my 409!!!





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