How would you design a late model ?

[dfhotlm33c]

comet..my point may have been missed amidst my lengthy rant...I was actually claiming the opposite...three wheeling WAS the fast way for 4 or five years..then people figured out how to get around fast without it..and the three wheelers started falling to the back...sorry if that wasn't clear...besides, I always thought it looked dumb...

and also, my point was that nobody will know until they change the rules...

and if they do..i guarandarntee the innovators of the sport will jump on it...

[dirty white boy]

if ya dont think a independent rear suspension will work on mud an dirt,..look at a volks wagon beetle mud buggy,..beem working for years at baja500!!

[Ronin]

The current 4-link live axle setup imho provides a good balance/compromise between forward bite and side bite. The rotation of the differential aids traction, the 4 links provide forward bite and steering whilst the j-bar provides additional side bite. I agree that some of this is a crutch for an imperfect system, but it does work.

The forward movement of the live axle “under” the chassis prevents the front end from “lifting” off the ground (raising the LF is due to chassis roll) and adds traction to the rear wheels. There is very little load transfer to the rear. How will you achieve this with IRS? IRS rely on weight transfer for traction. Having a lot of squat will transfer weight, but that unloads the front wheels (look at dragsters). Adding anti-squat will reduce weight transfer but will not aid traction.

In dirt oval racing the coefficient of friction between the dirt surface and the tyre is very low. You have to transfer a lot of weight to the outside tyres in order to increase the coefficient of friction between the tyre and the surface – remember that the force required to move an item on a surface is equal to the coefficient of friction between them multiplied by the mass of the item. High roll transfers a lot of weight increasing the coefficient of friction. How will you achieve this with IRS?

[Ghopper]

Guys,

3 wheeling - You are all three wheeling off the corner. A 500-700lb LF spring is not touching the spring perch the moment you look at the gas pedel with any lateral acceleration. Just because your tire is touching the ground does not mean there is much load on it. Only the weight of the spindle/hub/wheel +/- damper loading.

Why 3 wheeling - There are 2 drive tires that you are trying to load as equally as possible. Lateral acceleration transfers weight from Left side to Right side, so to keep LR ~= RR you must unload the LF putting all remaining Left side weight on the LR.

IRS would follow the same principle said above and currently done by a live axle. Only with IRS you can have more control over wheel steering angle and camber angle in a lighter package.




Ghopper

[fastford]

there is no way you could achieve the same amount of down force to the rear tires with a lift bar or pull bar on a irs no matter how much the center section rotates, on a live axle rear, the lift bar is lifting much of the cars mass and applying it to the rear tires, on irs the force is being contained within the chassis and would have no effect on the tires. the only place to try and achieve this would be at the hubs, which would mean on a 4 bar type set up,. the upper bar would have to angle down

[Ghopper]

Mr Ford,

We only need enough anti-squat to hit that LR limiter that you use. Then we are near the dynamic wedge used to get out of the corner. Sure there is ~0-1000lb dynamic lbf through the liftarm spring at some places around the track, but dont underestimate how much goes through the four bars.

Maybe in the next few months I can run some tests to get some numbers for the group.

The IRS car would look very similar to a live axle car going around the track, maybe minus as much visual forward movement of the LR....because now you have other ways to steer it.



Ghopper

[Matt49]

In dirt oval racing the coefficient of friction between the dirt surface and the tyre is very low. You have to transfer a lot of weight to the outside tyres in order to increase the coefficient of friction between the tyre and the surface – remember that the force required to move an item on a surface is equal to the coefficient of friction between them multiplied by the mass of the item. High roll transfers a lot of weight increasing the coefficient of friction. How will you achieve this with IRS?

You cannot increase coefficient of friction by increase weight or mass. You can increase the friction force but the coefficient of friction remains constant. You seem to be contradicting yourself by saying that transfer of weight increases the coefficient of friction immediately after outlining the equation correctly. In that equation, mass and coefficient of friction are independent variables. Increasing one has no effect on the other. You can increase FRICTION FORCE by increasing mass but you cannot increase the coefficient of friction by increasing mass. They are two different things altogether.

[Ghopper]

Ronin, Matt49,

Maybe we should switch to "load" or "normal force" instead of mass? Normal force being the force perpendicular to the ground plane. Less confusing and would match tire test data.



Ghopper

[fastford]

Mr Ford,

We only need enough anti-squat to hit that LR limiter that you use. Then we are near the dynamic wedge used to get out of the corner. Sure there is ~0-1000lb dynamic lbf through the liftarm spring at some places around the track, but dont underestimate how much goes through the four bars.

Maybe in the next few months I can run some tests to get some numbers for the group.

The IRS car would look very similar to a live axle car going around the track, maybe minus as much visual forward movement of the LR....because now you have other ways to steer it.



Ghopper

those places around the track would be from the time you pick up the throttle till you let off, and then you gain some advantage braking through the 6 coil which you could not utilize with irs, but please keep us informed of your test mr. hopper , i am interested in your findings.

[Matt49]

Ronin, Matt49,

Maybe we should switch to "load" or "normal force" instead of mass? Normal force being the force perpendicular to the ground plane. Less confusing and would match tire test data.



Ghopper

Normal force on a flat surface is the mass. Calculating the normal force on a race car tire on a banked track would be difficult because centripetal force would then become part of the equation. And considering a track surface isn't consistent, the coefficient of friction is also a moving target. I'm sure the data acquisition technology is out there for all of this but who has the money to invest in it at this level?

[racin6mod]

I've been seaching threw IRS and found the Holden system used down under tobe the best with some forward bite adjustment built in. but here's a couple photos of a jag irs chromed up for a street rod but you can see the possibilties.

[Ronin]

@matt49 - yes you are correct, sorry for my contradiction (was typing faster than I was thinking). Weight transfer would increase the effective vertical force which increases friction force, not coefficient of friction.

[Ghopper]

[QUOTE=Matt49;1460873]Normal force on a flat surface is the mass. Calculating the normal force on a race car tire on a banked track would be difficult because centripetal force would then become part of the equation. QUOTE]

Normal load on a flat surface is only mass (xgravity) when the vehicle is static. Acceleration vector + aero loads would be necessary.

Ford - I will not be testing anything till the rules change. I have enough trouble getting track time with the current rules I am a part-time amateur racer....which means I race every few weekends (I live in Ohio and my shop is in Iowa). I have seen many types of test-rigs and vehicles that gives me complete belief that our community could make an IRS faster than a live axle.


Ghopper

[fastford]

mr. ghopper me and you are pretty much in the same boat, me and my father and daughter pretty much do every thing, my father has been sick for the last few years so my racing has been limited, but they finaly found and fixed his problem, a tumor on the outside of his small intesten where he was losing blood, thank god it wasnt cancer and hes getting better every day, we buy bare chassis from a small chassis builder and do every thing else our selves including building our engines, but thats what we do, build things, and ive always been interested in irs, but for every positive ive found, there is three negatives, but im not saying its impossible