Author Topic: CG and CP-- distance from one to the other  (Read 2319 times)

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Offline red54studebk

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CG and CP-- distance from one to the other
« on: October 26, 2021, 01:22:39 PM »
car is 1972 Fiat 850 Spider with m cycle engine in rear - about same location as original car engine- wheelbase 79.8 inches- car length is 150.6 inches --- CP is located approx at base of windshield -- about how far  forward from CP should  we have the CG?  we are using lead bars and other lead weights as ballast .. we are looking for stability going down the salt and naturally trying to avoid a spin....i do know the saying... there are 2 kinds of people at Bonneville--those who have spun, and those who have not, but they will, later....thank you for info and help.

Offline Stainless1

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Re: CG and CP-- distance from one to the other
« Reply #1 on: October 26, 2021, 02:01:48 PM »
Where is your CG now?  What does your car weigh now? front weight?  rear weight? balanced left and right?    Bump Steer in front or rear suspension?  Amount of suspension movement?  Have you raced it on the salt?  How did it drive?
All that info and more helps determine what you need to do  :cheers:
Stainless
Red Hat 228.039, 2001, 65ci, Bockscar Lakester #1000 with a little N2O

Offline Dynoroom

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Re: CG and CP-- distance from one to the other
« Reply #2 on: October 26, 2021, 04:58:54 PM »
If you are going to run in Modified Sports you may want to look over section 5.D.4 again in the SCTA rule book...

Engine placement is optional so long as no change is made
to the driver?s location as originally designed. The driver
shall be seated behind the engine,
except in the case of
production and limited production bodies which are designed
for mid/rear-engine locations.
Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...

Offline manta22

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Re: CG and CP-- distance from one to the other
« Reply #3 on: October 26, 2021, 05:18:48 PM »
A Fiat 850 has a pretty short wheelbase. I think that will be your primary problem.
Regards, Neil  Tucson, AZ

Offline Stan Back

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Re: CG and CP-- distance from one to the other
« Reply #4 on: October 26, 2021, 09:29:35 PM »
Stainless -- the motor is in the back stock.
Past (Only) Member of the San Berdoo Roadsters -- "California's Most-Exclusive Roadster Club"

Offline Dynoroom

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Re: CG and CP-- distance from one to the other
« Reply #5 on: October 26, 2021, 10:53:57 PM »
Stainless -- the motor is in the back stock.

Cool, problem solved...
Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...

Offline kiwi belly tank

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Re: CG and CP-- distance from one to the other
« Reply #6 on: October 27, 2021, 12:54:21 AM »
If it spins he'd be behind the engine,.... then in front of the engine,.... :-D
  Sid.

Offline panic

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Re: CG and CP-- distance from one to the other
« Reply #7 on: October 27, 2021, 10:01:27 AM »
Weight between the axles is distributed between them (duh), and increases traction (if only slightly).
Weight ahead of the front axle is much more effective at moving the CG, but is cantilevered, and removes weight from the rear wheels while adding to the front wheels.

Offline Stainless1

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Re: CG and CP-- distance from one to the other
« Reply #8 on: October 27, 2021, 10:31:45 AM »
Thus my questions...
Where are you located... do you have access to a set of scales? 
Stainless
Red Hat 228.039, 2001, 65ci, Bockscar Lakester #1000 with a little N2O

Offline tortoise

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Re: CG and CP-- distance from one to the other
« Reply #9 on: October 27, 2021, 12:13:55 PM »
-- CP is located approx at base of windshield -- about how far  forward from CP should  we have the CG?

You should certainly max out the spoiler spill plates per section 4.CC.8, figure 9 to move the CP back as far as possible. Are you committed to running a windshield? Are you committed to running stock wheelbase?
« Last Edit: October 27, 2021, 12:18:07 PM by tortoise »