22 replies to this topic

[Rocket714]

So was walking around PPMS Saturday night and noticed one of the rush cars LR had no drop when up on the pit lift and no jack holding it up, but when on the track the car probably had the most drop of anyone. Any guesses on how this is physically possible?

[jo73]

Ahhhhh, DS2 this one's for you...

[Tommy]

So was walking around PPMS Saturday night and noticed one of the rush cars LR had no drop when up on the pit lift and no jack holding it up, but when on the track the car probably had the most drop of anyone. Any guesses on how this is physically possible?

Ive noticed it too.

[bhhracing]

Who is it

[jo73]

3rd base.

[dirtstudent2]

3rd base.

 

Thanks made my day, that's funny

[dirtstudent2]

Is the question your asking and someone else noticed about the distance the axle can travel down on the stands compared to how much the left rear hikes up under acceleration on the track?

 

I asking because I always think about drop as the difference(a calculation) between how much you let a corner chassis travel in total minus ride height.

If the left end of the axle cannot drop down while the cars jacked up then there has to be something else holding it up or the left end of the axle is in a bind which will not occur when at ride height.  

Maybe if it's on the stands and you put a downward thump to it getting past what ever bind is not allowing it to go down,  it would then drop down?

That puts this thought in my mind about it because out on the track when you hit it with acceleration it would get past the bind sort of throwing the left end of the axle into the track?

Isn't the whole deal with lifting the left rear corner about putting a wing to it and using your spring or stiff connection at the left rear corner to push the left rear via you now whole car wing into the track during acceleration?  

 

If you see the left end of the axle up when on the stands and way down when on the track something has to be holding it in place while on the stands or it would drop down.

I think a bind holding it in place which can be normally over come on the track might be a reason.

I don't know what combination of angles at the left rear of a late model might cause it?

Writing this I just thought of this which i'm sure is wrong.  Could you have a link which is compressible?

Might that give you a new adjustment per how strong you make the spring in the compressible link?

Could it then be a way to put a separate spring into the forward movement of rear steer?

Wouldn't that open up a whole new area of adjustment being able to set rear steer travel the same as you do chassis travel in addition to changing angles?

 

I don't know why you would be able to not see the left end of the axle drop down on the stands when you can see it on the track.

Fun to think about it 

 

 

 

 

 

 

 

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[dirtstudent2]

Another idea on it.

 

What if the right end of the axle was super heavy compared to the left end of the axle?

Would the whole assembly be able to rotate down on the right and up on the left when on jack stands?

Then when on the track it could still raise up on the left?

 

Dang you got me thinking on this.

 

What if the chain was located too far out from the center of the axle?

Wouldn't the axle then rotate down on the right and up on the left of where the chain is attached when on the stands?

If it were in close to the center of the axle then there would be at least less rotation.

 

That makes me ask if the rear end hub is normally centered on the center line of the car when at ride height?

Or might you center it somewhere else because of using rear steer which moves the center line of the car in relation to the front of the chassis?

 

again having fun again writing no matter if it's right or wrong 

[bullittwrench]

When ours is on the lift,  the left side is hanging on the droop chain around 13" to 14". The right side lays on the underslung.

[3 link]

When ours is on the lift,  the left side is hanging on the droop chain around 13" to 14". The right side lays on the underslung.

mine hangs the same......I'm thinking they made something to hook on the rear and frame (cause the author of this post said there was no jack under the rear) to hold it up to make tire change easier.....my left rear moves the tire ahead so much when it hangs that my crew struggles to get the tire in under the door panel and on the hub......if the car gets up in attitude on the track what other reason would they want the left rear to not droop on the lift ? ....zero indexing cage will still droop till the chain comes tight .....My right side has no underslung ....it has a chain to never let it come above chassis height

 

I'm pretending to be DS2 now .......so someone tell me what I'm missing here ? !!!!!!

Edited by 3 link, 16 September 2020 - 01:48 PM.

[dirtstudent2]

When ours is on the lift,  the left side is hanging on the droop chain around 13" to 14". The right side lays on the underslung.

 

Thank you the why of it and even possibility of what they saw and how it was compared now seems to make it all clear to me.

 

Drop is one thing, ride height another, up on the bars is another and none relate to where the tire looks to be located between being on chassis stands and under power on the track.

 

I think there comparing where the tires located up in or down from the chassis on the stands and on the track.

But they do not relate to each other in any way except for a visual reference they choose to make. 

 

edit:  holding the axle up for tire removing reasons makes a lot of sense.

 

i'll crawl back under my rock now   

Edited by dirtstudent2, 16 September 2020 - 01:54 PM.

[dirtstudent2]

Only one like for crawling back under my rock?

 

come on now ya'al can do better then that   

[jo73]

Ds2 your missed, thanks for the insightful answer. Makes one think.

[dirtstudent2]

When ours is on the lift,  the left side is hanging on the droop chain around 13" to 14". The right side lays on the underslung.

 

Probably a dumb question but if you had a 4 link chassis would you then want it overslung?

And another dumb question would you then be able to put more wing to it?

 

yep dumb and tryin to learn sorry for the proly ignert questions.   

[bullittwrench]

The underslungs stiffen the rear clip also. An overslung would allow more droop but could allow you to go beyond the rules. I think the series rules dictate both underslungs. Most guys make their LR underslung that bows down in the middle to allow max droop. When on the lift, we also have to jack up the Lr to change the tire. Thanks

[dirtstudent2]

yep dumb thought just popped into this old gray head 

 

I think on a Late Model but don't know so I'm asking this as a statement hoping to get answered that forward acceleration from the left rear as an example is used to both drive the car forward and lift the left rear corner of the chassis.  

What if you could use lateral acceleration to lift the chassis instead of forward acceleration?

If you got lateral acceleration which directly relates to speed and grip involved in lifting the left rear corner, wouldn't it leave more effort available for forward acceleration?

I'm also thinking if you used lateral acceleration to lift the chassis the amount of lift would also then directly relate to available grip and speed. 

Isn't it common to put less lift to it when the track slicks up and speeds are down reducing produced on track forces?

 

Lots more thoughts sneaking into my thought process about how it would effect the way the right rear tire is used, but for not the above dumb stuff is enough to think about. 

[old man d]

Welcome back Ds2.

[Retort]

ie:  "If you got lateral acceleration which directly relates to speed and grip involved in lifting the left rear corner, wouldn't it leave more effort available for forward acceleration?

I'm also thinking if you used lateral acceleration to lift the chassis the amount of lift would also then directly relate to available grip and speed."

 

Ds2,  Have you not just entered the pan-hard bar into the equation?  Geeezz,this racecar setup stuff was easy til you showed up!

[3 link]

here's an old adage I've heard since I got involved with 4 bar cars :  Side bite promotes body roll.......body roll does not promote side bite .....

[dirtstudent2]

here's an old adage I've heard since I got involved with 4 bar cars :  Side bite promotes body roll.......body roll does not promote side bite .....

 

That's a keeper.

 

Something I preach which goes along with it is "you can't have hold or gain weight without first having grip".