Jump to content




Photo

Hawk 7 two-speed "wall" syndrome


  • This topic is locked This topic is locked
221 replies to this topic

#1 dalek

dalek

    On The Lead Lap

  • Subscriber
  • PipPipPipPip
  • 259 posts
  • Joined: 25-October 11
  • Gender:Male
  • Location:Central FL

Posted 14 November 2017 - 10:30 AM

There is a phenomenon consistent with JK Hawk 7 (and JK Hawk Retro) motors that I'll refer to as a wall.
 
If you have a "two-speed" or a slug H7 or HR, or just would like to verify what I'm saying, you can perform the testing described below, using your power supply and any Hawk 7 or Hawk Retro motor, whether it's one you're still racing or one that you're not racing any more because the brushes are mostly worn out or the motor has bad brakes.
 
Beginning at 5 volts or less, increase the voltage at the rate of about one volt per 4 seconds. Typically, the motor begins to encounter an internal load, a "wall," so to speak, at about 9 volts, that causes the amp draw to increase but the RPMs don't increase very much.
 
Continue increasing the voltage and then at usually about 10 volts, you will hear the motor RPMs suddenly increase and see the amperage drop back down to normal.
 
I assume that this "wall" syndrome, (or you might call it a characteristic), when it's bad enough in a particular motor, is the cause of what we call a two-speed motor. A two-speed motor is one that causes a slot car to suddenly increase in speed, part way down a straightaway.  We've had a few of these.
 
When the "wall" is really bad, you can increase the voltage all the way to 12 volts and the motor rarely jumps to the higher RPM, so it'll be a slug, all the way around the track (I bought one of these a couple of weeks ago). Last night I discovered that when I get the voltage up to 12 volts, I can tap the motor shaft a few times and get the motor to jump to the higher RPM (and of course the amperage drops back down to normal – about 0.7 amps).   wonder if this indicates there is an armature shaft harmonic vibration occurring inside of the bushings that causes the "wall."

  • Gator Bob likes this
Dale King
 
Home Raceway




#2 Racer36

Racer36

    Race Leader

  • Subscriber
  • PipPipPipPipPip
  • 727 posts
  • Joined: 09-October 11
  • Gender:Male
  • Location:St. Catharines, Ontario, Canada

Posted 14 November 2017 - 10:37 AM

Every single two-speed motor I have seen is as a result of someone using too much heat when soldering wires on and melting the nylon bushing. This de-stabilizes the brush arm and allows the brush to walk around on the comm, effectively changing the timing.

 

Personally I think the rest of your theory is a bunch of crap, but that's just my opinion.

 

And again, you should stop running the voltage up beyond 5 volts with no load.


  • Cheater, race301, MSwiss and 1 other like this

Dennis Dominey

Lifelong half-assed slot racer


#3 MSwiss

MSwiss

    Grand Champion Poster

  • Advertiser
  • PipPipPipPipPipPipPipPip
  • 19,700 posts
  • Joined: 16-April 06
  • Gender:Male

Posted 14 November 2017 - 10:43 AM

Slotbloggers,

 

Do not free-rev your motors to 12v, as the OP indicates he does.

It may damage the motor and does nothing to indicate motor performance on the track.

The motor, under no load, at 12v, will reach much higher RPM than it will running on the track at 12-14v, where the motor has a considerable load from the gear train, tire to track surface adhesion, and downforce from the body.


  • Cheater, tonyp, Half Fast and 4 others like this

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.


#4 Gator Bob

Gator Bob

    Grand Champion Poster

  • Banned
  • PipPipPipPipPipPipPipPip
  • 13,350 posts
  • Joined: 12-April 11
  • Gender:Not Telling
  • Location:.

Posted 14 November 2017 - 11:13 AM

Are the comm tabs crimped (insulation displacement) and soldered ... or just crimped (folded)?


Posted Image
                            Bob Israelite

#5 jimht

jimht

    Checkered Flag in Hand

  • Full Member
  • PipPipPipPipPipPip
  • 1,248 posts
  • Joined: 16-February 06
  • Gender:Male
  • Location:The Alamo City

Posted 14 November 2017 - 11:31 AM

My experience is that a motor that suddenly speeds up at a certain point when unloaded is out of balance, has a bent shaft, loose bushing(s), or an out-of-round comm.

 

Seems that it sometimes can't get past that point (i.e. wall  :) ) on the track and so is a dud, speed-wise.

 

The issue is obviously not easily fixed with a sealed motor.


Jim Honeycutt

"I don't think I'm ever more 'aware' than I am right after I hit my thumb with a hammer." - Jack Handey [Deep Thoughts]


#6 Danny Zona

Danny Zona

    Checkered Flag in Hand

  • Full Member
  • PipPipPipPipPipPip
  • 1,133 posts
  • Joined: 27-July 12
  • Gender:Male
  • Location:Holly Hill (DaytonaBch), FL

Posted 14 November 2017 - 11:52 AM

I've had a few gear shifters lately.

I'm not knocking them. I just have dealt with them lately more often than not.

No biggie to me though.

It's just how it goes dealing with a mass-produced cheap motor. I take the good with the bad as long as everyone is dealing with the same problem.


  • Cheater, MSwiss, tonyp and 3 others like this
Test, test, test and go test some more.
You're never fast enough!!! 💯

Luck is the residue of design.

Be a fountain not a drain.

It's not about being right, it's getting it right.

#7 JK Products

JK Products

    Mid-Pack Racer

  • Subscriber
  • PipPipPip
  • 153 posts
  • Joined: 12-December 15
  • Gender:Male
  • Location:Algonquin, IL

Posted 14 November 2017 - 02:46 PM

JK Products does not support operating our motors in the method described by the the OP and we also disagree with his conclusions. As I indicated in a recent post by the OP, I think the "two-step" issue some complain about is possibly the result of improper gearing. 

 

If your motor is geared too tall (< 3.3 gear ratio), you can experience the car starting the straight slowly and then accelerating quickly as the RPMs finally pick up because they started too slow coming out of the turn.

 

If someone sees the two-step issue, please change the gear ratio to something higher, like 3.5 and check the motor again. If after doing this you believe you still have a two stepping motor, please PM me and we will be happy to investigate the issue.

 


  • Cheater, Samiam and Jesse Gonzales like this
Tim Homola
JK Products

#8 dalek

dalek

    On The Lead Lap

  • Subscriber
  • PipPipPipPip
  • 259 posts
  • Joined: 25-October 11
  • Gender:Male
  • Location:Central FL

Posted 14 November 2017 - 03:10 PM

Here is a YouTube link of a video I made of one of the good performing Hawk 7s I bought a couple of weeks ago.
 
It seems to show the tendency of the Hawk 7 motors to inherently be two-speed. 
 
I did the same test using an old Falcon 7 motor and the RPMs increased steadily all the way from 2 volts to 12 volts and, as expected, the amperage increased evenly also.
 


Dale King
 
Home Raceway

#9 JK Products

JK Products

    Mid-Pack Racer

  • Subscriber
  • PipPipPip
  • 153 posts
  • Joined: 12-December 15
  • Gender:Male
  • Location:Algonquin, IL

Posted 14 November 2017 - 03:49 PM

Dale, please do track testing as everyone has recommended.


Tim Homola
JK Products

#10 Racer36

Racer36

    Race Leader

  • Subscriber
  • PipPipPipPipPip
  • 727 posts
  • Joined: 09-October 11
  • Gender:Male
  • Location:St. Catharines, Ontario, Canada

Posted 14 November 2017 - 03:54 PM

The audio reminds me of a trip to the dentist. In fact the whole thread is about as pleasant...


  • elvis44102 likes this

Dennis Dominey

Lifelong half-assed slot racer


#11 olescratch

olescratch

    olescratch

  • Subscriber
  • PipPipPipPipPip
  • 730 posts
  • Joined: 19-July 13
  • Gender:Male
  • Location:Ravenna, OH

Posted 14 November 2017 - 05:21 PM

Just the sound of that motor revving gave me chills! I was waiting for the smoke! Not a good practice in my opinion???


  • tonyp likes this
John Stewart

#12 dalek

dalek

    On The Lead Lap

  • Subscriber
  • PipPipPipPip
  • 259 posts
  • Joined: 25-October 11
  • Gender:Male
  • Location:Central FL

Posted 14 November 2017 - 05:35 PM

Dale please, do track testing as everyone has recommended.

 

I *have* done track testing – that's what got me here.

 

I believe I'm conservative saying that one out of 20 Hawk 7s have problems on the track.


Dale King
 
Home Raceway

#13 dalek

dalek

    On The Lead Lap

  • Subscriber
  • PipPipPipPip
  • 259 posts
  • Joined: 25-October 11
  • Gender:Male
  • Location:Central FL

Posted 14 November 2017 - 05:41 PM

Here is the link to a video I made of the bad Hawk 7 I bought last week.

 

I bought three. Two are good in my JK Indy car, and one is not.

 

The previous video is of one of the good ones but shows the inherent "two-speed" tendency.

 

This video is of the bad motor. The text in the video explains everything.

 


Dale King
 
Home Raceway

#14 JK Products

JK Products

    Mid-Pack Racer

  • Subscriber
  • PipPipPip
  • 153 posts
  • Joined: 12-December 15
  • Gender:Male
  • Location:Algonquin, IL

Posted 14 November 2017 - 05:42 PM

Hi Dale,

 

I really would like to help.

 

From my earlier post:

 

"If someone sees the two-step issue, please change the gear ratio to something higher, like 3.5 and check the motor again. If after doing this you believe you still have a two-stepping motor, please PM me and we will be happy to investigate the issue."

 

Tim


Tim Homola
JK Products

#15 Brinkley47

Brinkley47

    A winner is a loser who gave it one more try

  • Full Member
  • PipPipPipPipPip
  • 829 posts
  • Joined: 18-August 12
  • Gender:Male
  • Location:Murfreesboro, TN

Posted 14 November 2017 - 06:04 PM

Sure, gear the motor to run slow and no surging worries. That makes no sense. This is another issue of the manufacturer dodging the problem or not knowing how to fix the issue. Blame it on the customer. Smart business practice.


  • gfox and Kevin Donovan like this
Will Brinkley
willbrinkley@gmail.com

#16 Dallas Racer

Dallas Racer

    Checkered Flag in Hand

  • Subscriber
  • PipPipPipPipPipPip
  • 1,770 posts
  • Joined: 03-November 07
  • Gender:Male
  • Location:Dallas, TX

Posted 14 November 2017 - 06:15 PM

I don't understand why some of you are giving Dale a hard time.


  • Danny Zona likes this

Phil Smith ® ™


#17 Cheater

Cheater

    Headmaster of the asylum

  • Root Admin
  • PipPipPipPipPipPipPipPip
  • 22,922 posts
  • Joined: 14-February 06
  • Gender:Male
  • Location:Norcross, GA

Posted 14 November 2017 - 06:46 PM

Will, 
 
I guess you're reading a different post than I am:

"If after doing this you believe you still have a two-stepping motor, please PM me and we will be happy to investigate the issue."
 
Wanna explain in English just how that is blaming the customer and dodging the problem?

Gregory Wells

Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap


#18 JerseyJohn

JerseyJohn

    Posting Leader

  • Full Member
  • PipPipPipPipPipPipPip
  • 3,894 posts
  • Joined: 05-September 07
  • Gender:Male
  • Location:Northern NJ

Posted 14 November 2017 - 06:49 PM

OK just my opinion. I have experienced that sudden rise in RPM, drop in amps and smother running in every Series JK Hawk since before the R motors. I believe its either a brush float issue or a balance harmonic. Ever have a tire on your car vibrate at 60, worse at 65, smooth as silk at 70.
 
Also once the brushes are fully seated that two-stage goes away.
  • S.O. Watt and Half Fast like this
JJ TRADE MARK BANNER copy.jpg

John Chas Molnar

"Certified Newark Wise Guy since 1984" (retired)
"Certified Tony P Chassis God since 2007"
" Internationally Know Slot Car Racing Celebrity "
https://www.facebook...nchassisworks/#
Email me
 


#19 Gator Bob

Gator Bob

    Grand Champion Poster

  • Banned
  • PipPipPipPipPipPipPipPip
  • 13,350 posts
  • Joined: 12-April 11
  • Gender:Not Telling
  • Location:.

Posted 14 November 2017 - 06:53 PM

Here is a YouTube link of a video I made of one of the good performing Hawk 7s I bought a couple of weeks ago.
 
It seems to show the tendency of the Hawk 7 motors to inherently be two-speed. 
 
I did the same test using an old Falcon 7 motor and the RPMs increased steadily all the way from 2 volts to 12 volts and, as expected, the amperage increased evenly also.

 
A video is worth a thousand words. Clear to hear the shift.
 
The two-stepping FK deal isn't new or unique to Hawk 7.
All the investigations have not proved out anything concrete to prevent its recurrence... if it's back again.
 
It does make sense to see if it is a 'shifter' motor in the comfort of your own power supply.
Posted Image
                            Bob Israelite

#20 Brinkley47

Brinkley47

    A winner is a loser who gave it one more try

  • Full Member
  • PipPipPipPipPip
  • 829 posts
  • Joined: 18-August 12
  • Gender:Male
  • Location:Murfreesboro, TN

Posted 14 November 2017 - 06:55 PM

Wanna explain in English just how that is blaming the customer and dodging the problem?


if I was a manufacturer, I think these posts on multiple cases warrant an investigation. If he is waiting on a customer to tell him how to fix the problem, he may have a long wait.
Will Brinkley
willbrinkley@gmail.com

#21 Brinkley47

Brinkley47

    A winner is a loser who gave it one more try

  • Full Member
  • PipPipPipPipPip
  • 829 posts
  • Joined: 18-August 12
  • Gender:Male
  • Location:Murfreesboro, TN

Posted 14 November 2017 - 07:03 PM

will.jpg

I am no English major, Greg. Does this sound like blame to you?
Will Brinkley
willbrinkley@gmail.com

#22 Cheater

Cheater

    Headmaster of the asylum

  • Root Admin
  • PipPipPipPipPipPipPipPip
  • 22,922 posts
  • Joined: 14-February 06
  • Gender:Male
  • Location:Norcross, GA

Posted 14 November 2017 - 07:03 PM

Investigate exactly what, Will? Every motor in his inventory?

I haven't noticed that Dale has offered to send JK that motor to check, have you?

Gregory Wells

Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap


#23 Brinkley47

Brinkley47

    A winner is a loser who gave it one more try

  • Full Member
  • PipPipPipPipPip
  • 829 posts
  • Joined: 18-August 12
  • Gender:Male
  • Location:Murfreesboro, TN

Posted 14 November 2017 - 07:06 PM

The surging issues with the new Hawk motors. There are three threads about this topic. Or... you could blame the customer and pretend like nothing is wrong. Ask anyone at the Brawl how many 7Rs burnt up on Friday. Probably the most I have seen at a Premier event. No worries, nothing wrong here... LOL.
Will Brinkley
willbrinkley@gmail.com

#24 Cheater

Cheater

    Headmaster of the asylum

  • Root Admin
  • PipPipPipPipPipPipPipPip
  • 22,922 posts
  • Joined: 14-February 06
  • Gender:Male
  • Location:Norcross, GA

Posted 14 November 2017 - 07:10 PM

Fair warning, Will, you're stepping real close to the line in terms of lack of civility IMO.

Might want to turn the dial a litle more in the adult discourse direction.

Gregory Wells

Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap


#25 Brinkley47

Brinkley47

    A winner is a loser who gave it one more try

  • Full Member
  • PipPipPipPipPip
  • 829 posts
  • Joined: 18-August 12
  • Gender:Male
  • Location:Murfreesboro, TN

Posted 14 November 2017 - 07:18 PM

Facts hurt sometimes. I personally seen ten 7R motors burn and I am confident there were many more. I know one racer who burnt three out of his three hand-outs. How would you feel if that happened to you at a big race?

You are defending a topic you have little experience with. Let the racers handle this one.
Will Brinkley
willbrinkley@gmail.com





Electric Dreams Online Shop