Jump to content




Photo

JK 4-1/2" RTR


  • Please log in to reply
35 replies to this topic

#1 mark1

mark1

    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 160 posts
  • Joined: 22-October 12
  • Gender:Male
  • Location:MI

Posted 04 July 2021 - 08:36 AM

I just started racing a new class at our local track (Downriver Speedway). JK 4-1/2". No modifications allowed. Hawk 7 motor. JK 10/38 gears only. A pretty nice car. Close racing.

 

One problem, though. The motor is in there at a big angle. The pinion engages only about a third of the spur gear. Lots of gears failing. Has anybody discovered a fix for this?


Mark Anderson




#2 Racer36

Racer36

    Checkered Flag in Hand

  • Subscriber
  • PipPipPipPipPipPip
  • 1,330 posts
  • Joined: 09-October 11
  • Gender:Male
  • Location:St. Catharines, Ontario, Canada

Posted 04 July 2021 - 10:11 AM

Simple fix is to allow an angled pinion for the class.


  • MG Brown, Bill from NH and mark1 like this

Dennis Dominey

Lifelong half-assed slot racer


#3 John Luongo

John Luongo

    Race Leader

  • Full Member
  • PipPipPipPipPip
  • 566 posts
  • Joined: 01-August 16
  • Gender:Male
  • Location:Haverhill, MA

Posted 04 July 2021 - 11:01 AM

sounds like a fun class with lots of close racing. i am not trying to be a wisenheimer here, but i would ask the track owner and/or the guy who does the teching how they resolved the issue. otherwise a drivers meeting is in order to address the local rules. may give everyone a few more options and still keep the spirit of the rule and the fun, close racing. best regards


  • mark1 likes this

#4 mark1

mark1

    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 160 posts
  • Joined: 22-October 12
  • Gender:Male
  • Location:MI

Posted 04 July 2021 - 11:08 AM

You're right Dennis! Not likely, though. This spec class is taking the place of the "anything goes" type Nascars we ran for years. Relocated motors, cut up chassis, ball bearings, super 16D. Ahh, the good 'ol days!  LOL!


Mark Anderson

#5 mark1

mark1

    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 160 posts
  • Joined: 22-October 12
  • Gender:Male
  • Location:MI

Posted 04 July 2021 - 11:16 AM

Good idea, John! I'll give it a shot! Meanwhile, (in case the answer is no), anybody have any tips/tricks to get the stock gears to live longer? While close, affordable racing has it's benefit, replacing gears in the middle of a race is frustrating.


Mark Anderson

#6 crazyphysicsteacher

crazyphysicsteacher

    On The Lead Lap

  • Full Member
  • PipPipPipPip
  • 361 posts
  • Joined: 04-March 12
  • Gender:Male
  • Location:NJ

Posted 04 July 2021 - 11:16 AM

Solder the motors in instead of screws. Should help.

Sent from my Nokia 7.1 using Tapatalk
  • Rotorranch and John Luongo like this

Chris Wendel
Silver Side Down Racing
Silver Side Down Graphics

​The Race Place Retro Crew member

"Failure teaches way more than success. It shows what does not work and what to never do again, again..." 🙊🙈🙉  


#7 John Luongo

John Luongo

    Race Leader

  • Full Member
  • PipPipPipPipPip
  • 566 posts
  • Joined: 01-August 16
  • Gender:Male
  • Location:Haverhill, MA

Posted 04 July 2021 - 11:27 AM

an interesting problem just the same. do all brands of gears wear out or just certain brands? i like the angled pinion idea from racer36. if some racers are not experiencing short gear life, what are they doing different from everyone else? great question!


  • mark1 likes this

#8 Rotorranch

Rotorranch

    What's a title?

  • Full Member
  • PipPipPipPipPipPip
  • 1,755 posts
  • Joined: 22-November 10
  • Gender:Male
  • Location:Atlanta, GA

Posted 04 July 2021 - 12:13 PM

Solder the motors in instead of screws. Should help.

Sent from my Nokia 7.1 using Tapatalk

 

 

X 2 for solder it in.

 

Rotor


  • mark1 and John Luongo like this
Jeff Chambers

Posted Image      Posted Image
                                         "Kinky Kar"

#9 mark1

mark1

    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 160 posts
  • Joined: 22-October 12
  • Gender:Male
  • Location:MI

Posted 04 July 2021 - 12:45 PM

The rules state that you use the two screws and you are allowed to solder along the top of the motor mount. Not as solid as I usually mount a motor. Still too much angle, on it.


Mark Anderson

#10 crazyphysicsteacher

crazyphysicsteacher

    On The Lead Lap

  • Full Member
  • PipPipPipPip
  • 361 posts
  • Joined: 04-March 12
  • Gender:Male
  • Location:NJ

Posted 04 July 2021 - 12:53 PM

The other thing to make sure is to mount the Spur gear with the setscrew toward the wheel and not the chassis up right. It means you may need to push the gear farther on the motor shaft but the way the jk chassis is set up makes it hard to get good long lasting gear mesh. The other thing to do is stop using jk gears and move to cahoza gears. They last way longer than the jk.

Now by what you say with the rules, the only other fix would be to solder the can to the chassis at the brush end to keep it from moving during a wreck. When the motor gets out of plane with the Axle gear the mesh is shot and so will be the Spur.

Sent from my Nokia 7.1 using Tapatalk
  • mark1 likes this

Chris Wendel
Silver Side Down Racing
Silver Side Down Graphics

​The Race Place Retro Crew member

"Failure teaches way more than success. It shows what does not work and what to never do again, again..." 🙊🙈🙉  


#11 Rotorranch

Rotorranch

    What's a title?

  • Full Member
  • PipPipPipPipPipPip
  • 1,755 posts
  • Joined: 22-November 10
  • Gender:Male
  • Location:Atlanta, GA

Posted 04 July 2021 - 12:55 PM

The rules state that you use the two screws and you are allowed to solder along the top of the motor mount. Not as solid as I usually mount a motor. Still too much angle, on it.

 

Solder only on the top of the mount? That is not the fix. The end away from the motor mount needs soldered to the chassis. 

 

Rotor


  • crazyphysicsteacher and mark1 like this
Jeff Chambers

Posted Image      Posted Image
                                         "Kinky Kar"

#12 MG Brown

MG Brown

    Grand Champion Poster

  • Administrator
  • PipPipPipPipPipPipPipPip
  • 7,743 posts
  • Joined: 16-February 06
  • Gender:Male
  • Location:The Cumberland Plateau

Posted 04 July 2021 - 01:58 PM

This sounds like a fun class. Just for Info- the USSCA has a 4.5" Flexi Class. You may want to look at and possibly adopt a version of their rules. 


  • mark1 likes this
That's thirty minutes away. I'll be there in ten.
 

 


#13 jokar124

jokar124

    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 113 posts
  • Joined: 25-May 14
  • Gender:Male
  • Location:Cambridge, Ontario, Canada

Posted 04 July 2021 - 08:50 PM

If you are not allowed to tack solder the can at the endbell end, than try using strong, double-sided servo tape to help keep the motor in place.


  • Samiam, crazyphysicsteacher and mark1 like this
Jo Salvaterra

#14 NJ Racer

NJ Racer

    Checkered Flag in Hand

  • Full Member
  • PipPipPipPipPipPip
  • 1,983 posts
  • Joined: 08-March 06
  • Gender:Male
  • Location:Delran, NJ

Posted 05 July 2021 - 08:20 AM

Mark

 

You should post close up photos of your chassis with your motor, axle & gears installed.  


  • Bill from NH and Rotorranch like this
"Ya gotta be in it to win it"

Ray Carlisi

#15 Mike Patterson

Mike Patterson

    Village Luddite

  • Subscriber
  • PipPipPipPipPipPipPip
  • 2,522 posts
  • Joined: 14-October 07
  • Gender:Male
  • Location:Zanesville, OH

Posted 05 July 2021 - 09:48 AM

You should post close up photos of your chassis with your motor, axle & gears installed.  

 

This would be a great help.


I am not a doctor, but I played one as a child with the girl next door.


#16 Pablo

Pablo

    Builder

  • Administrator
  • PipPipPipPipPipPipPipPip
  • 18,354 posts
  • Joined: 20-February 06
  • Gender:Male
  • Location:Cleveland, Tennessee

Posted 05 July 2021 - 10:03 AM

I'm curious to know how the tech inspector can tell the difference between a JK pinion and a similar pinion of same pitch and teeth from a different manufacturer. Handout spec pinions?  :crazy:


  • Rotorranch likes this

Paul Wolcott


#17 John Streisguth

John Streisguth

    Johnny VW

  • Full Member
  • PipPipPipPipPipPipPipPip
  • 5,638 posts
  • Joined: 20-November 08
  • Gender:Male
  • Location:Bangor, PA

Posted 05 July 2021 - 10:15 AM

Instead of an angled pinion, what about an angled spur gear? Since it sounds like people are having to replace them anyway.

 

I can never understand rules that make it harder for beginners, just to maintain a small original wear part. As long as it's the same number of teeth, why not change to a angled pinion that makes things easier for a beginner? It's not like they don't wear out


  • crazyphysicsteacher and mark1 like this
"Whatever..."

#18 W. J. Dougherty

W. J. Dougherty

    Checkered Flag in Hand

  • Full Member
  • PipPipPipPipPipPip
  • 1,303 posts
  • Joined: 27-April 07
  • Gender:Male
  • Location:Charles Town, WV

Posted 05 July 2021 - 10:30 AM

JK doesnt make any angled gears, spurs or pinions, so you can take that suggestion off the table. Most of us know there is a difference between ready to run and ready to race. Track owners are looking at ways to sell cars out of the show case that people can put on the track and go racing. Another suggestion you all could make is that you volunteer your time and parts to take the RTR cars and fix them so they can be raced
  • crazyphysicsteacher and mark1 like this
Yortuk & Georg Festrunk

#19 MSwiss

MSwiss

    Grand Champion Poster

  • IRRA National Director
  • PipPipPipPipPipPipPipPip
  • 25,614 posts
  • Joined: 16-April 06
  • Gender:Male

Posted 05 July 2021 - 12:11 PM

Instead of an angled pinion, what about an angled spur gear? Since it sounds like people are having to replace them anyway.
 
I can never understand rules that make it harder for beginners, just to maintain a small original wear part. As long as it's the same number of teeth, why not change to a angled pinion that makes things easier for a beginner? It's not like they don't wear out

The issue with an angled spur is 15 degrees is probably too much angle and getting a small diameter pinion to reach it within the confines of the screw in motor bracket.

Small diameter gears makes getting a mesh tricker.

Add angled anything makes it even trickier as you are pushing the gears even closer, for the superior tooth engagement.

In a perfect world, for maximum reliability, a spec gear ratio would be figured out, that uses gears with a higher tooth count that are, of course, a bigger diameter.

Something that fits in the relatively small range that the screw in bracket allows.

Use an ARP angled pinion with the JK straight spur.

We get silky smooth, reliable gear meshes using that combo, for our Thursday night GTP racing, using the 4" C21 chassis, albeit sometimes with motor soldered in.
  • crazyphysicsteacher and mark1 like this

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


#20 Pablo

Pablo

    Builder

  • Administrator
  • PipPipPipPipPipPipPipPip
  • 18,354 posts
  • Joined: 20-February 06
  • Gender:Male
  • Location:Cleveland, Tennessee

Posted 05 July 2021 - 12:49 PM

No modifications allowed. JK 10/38 gears only. 

Back to the OP. If his quote of the rules is accurate, I read it as both pinion and spur must be JK products. Looks like a poorly written rule but it is what it is. Maybe he misunderstood or mis-quoted the rules?

 

Again, how is the tech inspector going to know the difference between a JK pinion or, for example, a straight pinion from a different manufacturer? Making rules that are unenforceable don't make good sense.


  • Rotorranch likes this

Paul Wolcott


#21 mark1

mark1

    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 160 posts
  • Joined: 22-October 12
  • Gender:Male
  • Location:MI

Posted 05 July 2021 - 02:07 PM

Thanks for all the ideas everybody! I can understand the track owners concerns, actually. This class is a new one at our track. The previous nascar class had all sorts of rule changes as time went on. He always had somebody in his ear about rules. Once that door is opened, the “requests” never stop! Maybe we can use different gears and leave all the other rules in place? BTW I tried to post some pictures, couldn’t get that to work for me.
Mark Anderson

#22 John Luongo

John Luongo

    Race Leader

  • Full Member
  • PipPipPipPipPip
  • 566 posts
  • Joined: 01-August 16
  • Gender:Male
  • Location:Haverhill, MA

Posted 05 July 2021 - 02:22 PM

Someone suggested installing a workable, durable gear set on the rtr cars in the case.

 

When a racer buys the RTR car it really would be ready to race. Have the correct gear sets available for purchase then everyone, including the guy doing the tech inspection, will have what they need.

 

New cars being sold will match whats being raced. Easy for tech inspection.

 

i still like the idea behind this class.


  • Rotorranch and Samiam like this

#23 Don Weaver

Don Weaver

    Checkered Flag in Hand

  • Subscriber
  • PipPipPipPipPipPip
  • 1,820 posts
  • Joined: 26-October 07
  • Gender:Male
  • Location:Lexington. SC

Posted 05 July 2021 - 04:19 PM

You could just specify a single gear ratio and let racers choose their gear preference.


  • Samiam likes this

Don Weaver

​A slot car racer who never grew up!

 

The supply of government exceeds demand.
L.H. Lapham
 
If the brain-eating amoeba invades Washington
it will starve to death...


#24 Bill from NH

Bill from NH

    Age scrubs away speed!

  • Full Member
  • PipPipPipPipPipPipPipPip
  • 14,274 posts
  • Joined: 02-August 07
  • Gender:Male
  • Location:New Boston, NH

Posted 05 July 2021 - 04:56 PM

In my opinion, since those Hawk 7 motors are all going  to run differently anyway, what's the need for a specified gear ratio? In 1997 we started running Plafit Cheetahs (from the days before Hawks & Falcons) in a 4" flexi. The only gear restriction we had was a  9T pinion  & a 29, 30, or 31T spur. This allowed for limited gear tuning & worked well. But even in those days, some motors were dogs & others kicked a$$. I had both, but I never bought 10 or a dozen motors to cherry pick from.

 

This 4 1/2" class should be a lot of fun, as long as it's not over-burdened with rules. Will you be using the Cheetah 7 chassis with stockcar bodies?  Any restriction on which bodies can be run? There sometimes is. How about a "spec" tire?


Bill Fernald
 
I intend to live forever!  So far, so good.  :laugh2:  :laugh2: 

#25 W. J. Dougherty

W. J. Dougherty

    Checkered Flag in Hand

  • Full Member
  • PipPipPipPipPipPip
  • 1,303 posts
  • Joined: 27-April 07
  • Gender:Male
  • Location:Charles Town, WV

Posted 05 July 2021 - 06:03 PM

JK sells 4.5 stock cars right out of the box. They have modern bodies and they have retro bodies.

 

Mach1 Raceway races this RTR class with the retro bodies. The owners original thought was only to allow rear bushings be soldered in, but otherwise race it as it came out of the box.

 

Ive read all the comments so far and each of you have made good suggestions based on your years of experience. You all are not the intended audience. You have the skills to race higher level classes.

 

This class is intended for the beginner who just walks in the door and rents a car for the first time and then decides they want to go racing.

 

The hardest thing the tech director needs to worry about is keeping experienced racers honest in a class like this.


  • Eddie Fleming likes this
Yortuk & Georg Festrunk





Electric Dreams Online Shop