What kid of antisquat do the IRS suspensions have?

rupert14

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I am converting a trophy kart elite to a personal fun machine. My kids race the karts and I want to be able to drive with them and help them learn to be better drivers. I bought a TK elite (randy's cabinet car) and it has extensive rear suspension mods making the chain very difficult to manage and it only has 8inches rear travel. I am putting a Raptor 660 motor in it and will be moving the drivers compartment back about 4 inches to make more room. I will be running some kind of IRS in the rear to make more room and allow the motor to sit back in the car. I am considering a dual A-arm setup, trailing arms, and the "three link" like the Redline Revolt uses. I am looking for something that whold work best in the dezert and short course and not just good for one or the other. I race in Whiplash with my rhino and could short course the car or run it in a dezert event like Snowflake where top speed is the name of the game. I have not been able to find out what the antisquat numbers would be for the IRS systems. What would you guys recommend and why? I have the resourses to build whatever I need to so I am not limited by off the shelf parts. Here is a pic of the Revolt's suspension for reference.

thanks
Bob
 

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Triaged

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You don't know how to calculate the anti-squat or you don't know what it should be?
 

partybarge_pilot

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Go 5 link. A-arm like handling and trailing arm wheel path without the axle plunge. Trailing arms have very little squat/anti squat effect. A-arms even less.
 

rupert14

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You don't know how to calculate the anti-squat or you don't know what it should be?

Calculating for a four link solid axle is easy. Making it fit can sometimes be a challenge. I have not seen any calculator programs for any IRS suspension systems. It is such an important factor for a straight axle I thought I would ask about IRS systems. The five link or three link like the Revolt puts the force transfer of acceleration on the side of the car somewhere in or in front of the midline whereas a trailing arm places the forces back by the engine. I know "antisquat" may not be the right term for it but I am posative these type of changes will affect the handling of the car. I definitely want to go with a system that keeps the axles from plunging ( A-arm, three link, or five link) but I thought I would ask the "pros" before I bulit anything.

Bob
 

Triaged

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For suspensions that are "simple" just use the equation in the image below from Milliken & Milliken's Race Car Vehicle Dynamics (not my scan...I found it on the net)

If you had MatLab there files for that. You could also try a trial version of a commercial software like SusProg3D. I own a copy of SusProg. It works well and isn't too hard to learn. Setting up steering however can be a pain if you aren't using a R&P.
 

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rupert14

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For suspensions that are "simple" just use the equation in the image below from Milliken & Milliken's Race Car Vehicle Dynamics (not my scan...I found it on the net)

If you had MatLab there files for that. You could also try a trial version of a commercial software like SusProg3D. I own a copy of SusProg. It works well and isn't too hard to learn. Setting up steering however can be a pain if you aren't using a R&P.
DOes this apply to the rear supsension? I am planning to leave the dual A-arm setup in the front.

Bob
 

FullsizeFun

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Squat/anti-squat does not apply in an IRS car. The only "squat" that exists is purely due to weight transfer from acceleration. The length and front pivot height of your trailing arm along with springrate can effect this.
In IRS setups the diff is mounted solid in the chassis. there is no torque applied to the Trailing arm/5-link/A-arms whatever the setup may be.

Squat in a 4-link on a truck comes from the pinion wanting to "climb" up the ring gear. This applies torque to the rear end housing, twisting the pinion up. This force pulls on the upper links and pushes on the lower links, which are attached to the chassis. The orientation of the links changes how this pushing/pulling effects handling.
 

Triaged

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Squat/anti-squat does not apply in an IRS car.
Not true

The only "squat" that exists is purely due to weight transfer from acceleration.
partially true

The length and front pivot height of your trailing arm along with springrate can effect this.
True...it is called anti-squat!

In IRS setups the diff is mounted solid in the chassis. there is no torque applied to the Trailing arm/5-link/A-arms whatever the setup may be.
That just moves the line of action (from the contact patch to the wheel centerline)

Squat in a 4-link on a truck comes from the pinion wanting to "climb" up the ring gear.
The squat comes from weight transfer due to acceleration and an above ground level center of mass just like with IRS.

This applies torque to the rear end housing, twisting the pinion up. This force pulls on the upper links and pushes on the lower links, which are attached to the chassis. The orientation of the links changes how this pushing/pulling effects handling.
Sure...it is called anti-squat
 

partybarge_pilot

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There is some lift generated on accel from the trailing arms not being parallel with the ground. The more down angle they have on them a ride height the more they will want to rise as the wheel pushes forward.
 

isdtbower

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On another board we discussed anti squat for going fast. The rear was changed from negative antisquat to positive with very good results (New Ultra 4 car. front engine, solid axle, 4 bar.

I have a Jeep with swing arm IRS with little antisquat and generally don't like it except for broadslide turning. Going to a new build and need longer arms for travel. From MC experience landing on the gas tends to help rear end squat, and subsequent toe dragging.

What antisquat % numbers do drivers usually like?
 

5racer

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i thought anti squat was when your lady stood up to tinkel.over engineered
 
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