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JK C43 chassis tune-up and test


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#1 Pontes1

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Posted 22 February 2017 - 05:56 AM

Hey, everyone,

 

I have built the first JK C43, and also some of my friends, but some questions arrise now as we were much used to the JK X25, X24, X11, etc., even the Mossetti 1002, and we are not getting, in my opinion, yet the full potential of this new chassis.

 

Compaision with the older chassis:

 

in general we get less rear grip than the others (X25, Mossetti, X24), the tail is more all around, not so planted as to the others.

 

More forgiving than the others, when abused it stays in the track more, where others eventually deslot.

 

Good low weight, when we compare with the X25; this is a good advantage for the other JK chassis.

 

Revolutionary bar system, even if we at the moment do not yet understand well what to do with those two bars, and in what way the new assorted thickness option bars act or change the handling?

 

The center section normally comes flat as we get it, but the pans when they come twisted are more difficult to put correct than the older versions.

 

There is in my opinion too much side play in the pans as standard; how can we fix this? 

 

In general seems to be a great chassis, but the rear loose feeling is something that I wish to know from you guys that already made set-ups and played with the optional bars, what can we do to get more rear plant (not so loose )?

 

If you can help this discussion, please. do. I think many racers will benefit from it.

 

Regards,


Fernando Pontes




#2 MarkH

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Posted 22 February 2017 - 07:14 AM

We race on club tracks with tighter turns than most commercial tracks. Our track lengths are between 85ft and 108ft just to let you know where my opinion comes from. It may not be applicable to your racing.

 

My observations- with Both Parma Storm and JK Ultimate Peugeot bodies:

 

X-25-3Pc chassis:

1) excellent smooth handling

2) easy to attack the corners

3) relatively easy to feel how the car handles

4) bite bar tuning is simple and repeatable

5) seems to recover well from being over driven

6) bends relatively easy from wall shot-sometimes

7) needs to be flattened at initial build and after rough racing

 

C43-out of the bag:

1) great handling- seems to stick better than X-25- faster lap times than X-25 by 0.1-0.2 seconds at the limit

2) attacking the corner I find is more "HO" like. yes it sticks very good until it ejects

3) car feels like it can do anything - inspires confidence

4) unknown on the bite bars- I have not tuned with them yet

5) same comment at number 2. Once it lets go it is gone

6) takes a wall hit like a tank- very tuff

7) flat out of the bag- the guide needs to be bent up to work properly

 

I actually still feel more comfortable driving the X-25 mostly due to have used it for the past several years. After only around 10 races on the C43 it is becoming easier and I look forward to tuning with the bite bars. I also have found the tires used on the X-25 setup are not as good on the C43. Smaller hub seems to add some "Feel" to the car.


Mark Horne

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There are only two things in life that make me feel alive. Racing is one of them.


#3 bluecars

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Posted 22 February 2017 - 07:47 AM

I advise anyone tuning a JK43 to read Pablo's BUILD of the JK43. It covers more info than anything else I've seen.

 

JK even complements him on knowing what this chassis needs to work.


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Robert "Red" Valantine :diablo: 


#4 Pontes1

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Posted 23 February 2017 - 06:43 AM

Pablo´s post is very good, however this covers only pre-running, and set-up before start.

 

My questions are related more to after...

And the real usage of the optional bars and the recations to several changes, including those bite bars change.

Also these feeling of too much tail movement seen at lesat in two of the cars over here. Is this normal or did we get bad chassis?

Also is it normal to have too much side play on the pans related to the center?

If no, how to solve this...?

 

Thanks for the imputs.


Fernando Pontes

#5 JK Products

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Posted 23 February 2017 - 08:29 AM

Hi Fernando,

 

The large amount of play is by design. Please don't make any assumptions about the chassis set-up. Some people have tried to set it up like an X25 and this is not a good idea. 

 

My #1 recommendation is to do testing once you're comfortable driving the chassis! Start from bone stock and then make changes and measure the results. If it makes the car faster, great. If not, revert and try something else. You can see what modifications others have done as a guide but please test on your own track to be sure.

 

I am confident you'll like the chassis more as you learn it. 


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Tim Homola
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#6 John C Martin

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Posted 23 February 2017 - 11:10 AM

I flipped the bite bars for better weight distribution than they were in the package for (King and Engleman track doughnuts) and lead-on. Back bar heavy part to inside doughnut. Front bite bar heavy to inside of lead-on.

Jigged the rear with adj. bushings for .720"s... geared13/34.

Really have to overdrive to deslot it.

Great chassis... wish it had aluminum pans...

 

image.jpg


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#7 Benno - SAC

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Posted 23 February 2017 - 12:07 PM

Hi Fernando,

 

We didn't have any issues with this chassis and it is very fast. We just build it like described in the PDF from JK. In our first 2017 season race everybody who already had one was impressed. I drove it with very soft tires. It's realy hard to overdrive it.

 

Greetings from the same side of the Atlantic (Germany).  :sun_bespectacled:


Schöne Grüße (Kind regards)

Benno Stolberg

 

www.SAC-Stolberg.de


#8 JK Products

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Posted 23 February 2017 - 09:33 PM

Sometimes wishes come true ... stay tuned. ;)


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Tim Homola
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#9 Danny Zona

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Posted 23 February 2017 - 09:59 PM

Can't wait! LOL.
Test, test, test and go test some more.
You're never fast enough!!! 💯

Preparation leads to separation.

Success is never owned but rented and rent is due everyday.

KELLY RACING 😎

#10 W. J. Dougherty

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Posted 23 February 2017 - 10:15 PM

Sometimes wishes come true ... stay tuned. ;)


Please consider making them a little more stout than the X25 pans.

Also, consider plating them so they can be soldered to...

Thanks...
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Yortuk & Georg Festrunk

#11 Pontes1

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Posted 24 February 2017 - 04:14 AM

Thanks for your coments about my questions! They were useful.
 
This talk about the alu option pans, is something for me strange. Here no one uses them as one is afraid of the crashes and the chassis being too light and not having enought weight to have good grip...
f
Maybe because of the fact we only race on 100% flat tracks, so taking this opportunity I ask: is it a real advantage to get the flu pans? If yes, for all types of track design or only high-speed banked ones??

Regards.
Fernando Pontes

#12 John C Martin

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Posted 24 February 2017 - 10:34 AM

Using a thinner body (CoG better ). Tuning with a small amount of lead (maybe). Trying different tire compounds..

Yes, you will be faster. Should of said first one to the deadman, the rest is up to you... LOL.

Pin tubes on aluminum pans? I use arm spacers soldered to both sides of the tube on the supports. You can even make them jiggle if you like by opening the hole slightly.

Using a small amount of JB Weld in the right places can help with some bending problems as a preventive or to prevent a reccurence.

#13 MSwiss

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Posted 24 February 2017 - 02:05 PM

... or only high-speed banked ones??


Yes. In the US there are many more banked track, than flat, so subsequently there is more racing with this type of chassis on them.

I'm sure when JK comes out with an aluminum pan, it will be very popular in the US.
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Mike Swiss
 
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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


#14 JK Products

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Posted 25 February 2017 - 09:25 AM

We have been trying different grades of aluminum but the strong ones that we would like to make don't conform in the stamping process and the uprights crack at the 90 degree bends.

Still working on it. We may have to go with similar material to the X25 for now.
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#15 gotboostedvr6

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Posted 25 February 2017 - 10:16 AM

A strong light pan could be made from the existing pan/ thickness. Just narrow the "rails."

It would be much stronger then any aluminum option.
David Parrotta

#16 MSwiss

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Posted 25 February 2017 - 10:59 AM

Not a bad idea.

You couldn't do that with the existing punching tooling.

But maybe with lasering apparently now accepted as a legimate way to make a "stamped chassis," an alternative skeleton steel pan could be fabricated, especially if the existing forming tooling could still be used.

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


#17 Dave Crevie

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Posted 25 February 2017 - 03:31 PM

Tim;

 

Your cracking problem is probably from the hardness of the temper of the aluminum alloy. Going softer

will make it form better, but be more prone to bending during use. There are two things you can try;

 

Increase the radii at the bends, to reduce the internal stress at the bend. (preferred)

 

Slow down the stroke of the press at forming. If the company doing the stamping is doing it in a flywheel press,

it might be doing the forming too fast. Ask if they can do it in a hydraulic press so that the stroke can be slowed

down. Aluminum will sometimes work harden during bending, slowing how fast the bend is made often eliminates

the cracking that results from work hardening. 


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#18 Rob Voska

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Posted 25 February 2017 - 06:13 PM

The heat treat of aluminum is critical to forming.  We had a repeat job that after making many times all of the sudden we could not form in a press brake.  Crack ,split, tear and it was not consistent.  We even tried heating nothing. 

Larger radius didn't work either.  Come to find out the material was from Russia & it simply would not form like US made material.  We had the same problem with plate from Africa.  It always meets all the specs until you try to build something with it.


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#19 Geary Carrier

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Posted 25 February 2017 - 06:42 PM

 

It always meets all the specs until you try to build something with it.

 

 

How could that possibly happen?... :laugh2:


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Yes, to be sure, this is it...


#20 Dave Crevie

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Posted 26 February 2017 - 03:31 PM

Most foreign materials don't meet ASTM specs, even if they say they do. Testing the pre-production samples

with a Rockwell hardness tester will sometimes catch an out-of-spec material before the production parts are

run. Aluminum does funny things when it is formed. We found that deep-drawing had to be done very slow, or

the material would actually tear, and this was un-tempered aluminum. That is why hydro-forming has become

so popular for producing formed aluminum parts. 


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#21 Dave Buchholz

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Posted 11 July 2019 - 08:05 AM

I have been looking the the JK pdf file mentioned above, unsuccessfully.

 Can anyone  direct me to a downloadable file?



#22 TallyBernie

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Posted 11 July 2019 - 11:21 AM

The only JK C43 pdf I'm aware of is available at https://abslotsport.biz/JKASETUP.pdf.


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