19 replies to this topic

[honeybadger1]

jo wants an intelligent discussion so I'm gunna give it to him....

 

Let's discuss the use of progressive/digressive spring stacking with and/or without the use of an additional bump stop/bump spring.

 

Who's using what combination, and what are the dynamic load transfer effects on corner entry, apex, and exit?

[Retort]

People smart enough to even spell that kind of stuff, ain't hanging around this place. Except for Dirt Student...

[dirtstudent2]

I'll take a stab at an answer.

 

Please notice the question marks I don't know the answer just winging it probably wrong off the top of my head with my morning coffee. 

 

Is digressive the same as what's being done today with shock rubbers at the left rear corner of a winged sprint?

 

And wouldn't that make progressive the same as being down on the torsion bars without shock rubbers?

 

Didn't Bobby Allen use a digressive setup many years ago at the right front corner of the car with an added on coil over the shock?

[dirtstudent2]

Just had another thought about it and thanks for the great question though not to me it's fun to think about.

 

Since the weakest spring is always going to operate first and even though it may seem like it's waisted effort operating it and function doesn't come into play until you get into the heavier spring, couldn't you think of using the effort needed to operate the weaker spring to do something for you?

 

What I'm thinking about is the effort to operate even the weak spring has to have been projected towards the tire involved.  By controlling placement of the weak and strong spring wouldn't you also be controlling somewhat the direction forces are coming from to operate the springs and more importantly the direction they end up being applied to the tire contact patch?

 

I think I can see making a choice between them dependent on if your looking to drive a tire into the track a little better or free it up at a particular place on the track because it's in a negative conflict with another tire?  

 

Since you offered the question pertaining to late models is there a particular corner of the car your thinking the use of the setup most likely?  Because I hear so much about bump stops at the right front corner of a late model I'm going to guess, probably wrongly, there probably not as involved at the right front corner???  But then again thinking about maybe they could be used to sort of ease the right front corner onto what ever would be used for a bump stop?   

 

thanks again you offered a totally FUN question to think about.

 

 

edit:  dang this racing thing is just too complicated.  You just made me wander from how to control the movement of a corner mainly worrying about when movement stops to altering the rate through out movement of the moving up or down of a corner of the car.  Now you got me thinking about what IF you used >progressive springs< on the setup you caused us to think about?

Edited by dirtstudent2, 05 August 2019 - 08:54 AM.

[honeybadger1]

Actual footage of dirtstudent2 coming up with all the answers....

 

 

[dirtstudent2]

That's funny 

 

 

here I thought you were going to help me out by saying how I'm spot on with my thinking about it? 

Edited by dirtstudent2, 05 August 2019 - 11:17 AM.

[jo73]

Badger, I think you getting that out there is a good thing ?

Who is using what, hell I have no clue, when I was a pit grunt we used a 1" breaker bar and cranked on the corners. We dropped oil pans and tossed in a good used bearing or pulled the 4 speed out of tow truck and put it in the racer only to do it all over at the end of the night.

I have said it in the past the bashing of tracks really needs to stop. Maybe just maybe if some start intelligent conversations or discuss what a local track and driver are doing. A.J. FLICK winning 12k at the port is in my eyes huge, yet it is struggling to get 10 replies. Chad Kemmanah is driving a second car out of the Garvin garage. Who would have believed that ?

[Walt Wimer]

right on jo!!!

[brad hibbard]

I like the original topic here 

can we start with a clear definition 

correct me if I'm wrong on the first two

 

Linear----gains weight equally per movement (example)  200# spring 1 inch of movement= 200#---2 inches of movement =400#---4 inches of movement=800#

 

progressive--gains more weight for more movement (example) 1 inch =200#---2 inches=425#---4 inches of movement=900#

 

now for digressive (this is where I am not completely clear) but this is what I think---

I "think" it means it gains less and less on movement 

example

1 inch of movement =200#-----2 inches of movement=375#----4 inches of movement = 700#

 

the progressive and digressive #'s are merely and example of how I think the different types of springs work

 

once we establish clear definition then we can begin discussion on application of the different types of springs (or shock)

 

Brad

[dirtstudent2]

found this:  hope it's what's being talked about

 

https://www.hypercoi...rate_slides.pdf

Edited by dirtstudent2, 05 August 2019 - 05:49 PM.

[dirtstudent2]

all described above assumes the springs are constantly operating

 

That is not always the case.  Springs may be setup on the same corner to operate at different times.  And the time each is operated may or may not coincide with when the other or others operate.  

Edited by dirtstudent2, 05 August 2019 - 07:12 PM.

[brad hibbard]

Back up---

 

lets start slow----that link made my hair hurt

 

lets do SIMPLE (captain kangaroo) definition to progressive and digressive

 

let's understand terms before discussing anything about reaction

 

Brad

[dirtstudent2]

"(captain kangaroo) definition to progressive and digressive"

 

 

Interesting you point that out Brad.  I can't figure out why each is called what it is either.  I look at it and try to say one or the other is progressive but then wonder about progressive what the heck are they referring too.  

 

I am lucky to have my own engineer with a ton of common sense to run thoughts by weekly about this stuff.  And yes it's rare but sometimes the discussion or his simple ways of explaining my complications ends up as "it's magic".    I don't care what you race it's about how you need to use the thing and are you capable of using it correctly that sets your position in the pecking order.  And as it is with most the pecking order is usually more towards the back then the front.  

 

The big thing, idea, fact I got out of the article was with any combination of springs the spring rate will be less then the weakest spring.  I guess the formula is proving it.  But it's pretty much a meaningless fact.  Because if you need a particular spring rate to get the job done, because of that fact, your going to have to use combinations of stiffer springs.  A fact not covered in the link which must be keyed in on is the weakest spring will always operate first.  If the progressive/digressive thing relates to spring position it's another who cares thing because the weakest spring will compress or partially compress first.  So my question is who cares where the springs are positioned because distance operated first if the springs are the same is the same distance.  Throwing the bump stop into it is interesting.  That's where sequencing when springs operate can come into play if we replace the stop with a rubber stop.  I don't think it matters if were considering a late model or a sprint the progressive/digressive stuff mainly belongs to the right front and the left rear.  That leaves right rear to be about how hard, how quickly and when you put the tire to the track.  And the left front becomes a needed detour or path for weight needed to the rear during acceleration and path for braking weight and weight needed to holding the right side in when your trying to maintain momentum.  What's still magic for me is not about spring or shock at the right front.  It's about the magic of how leveraging at the right front can be used to control how you detour weight via the left front on it's way back for acceleration.  Seems like lengthening the levers which get the right front operating to assist acceleration in the back shifts efforts towards the right rear.  I relate the length of levers to timing with longer levers appearing to take longer to operate, yeah the engineers will tell ya the opposite, ... back to the magic I don't have a reason why but it seems like if you put more effort into the right front to operate longer levers or more complex parts weight somehow magically goes more directly towards the right rear.  It ain't about roll centers I think the magic is it's more about the path you make instantaneous weight movement take.  It has to be magic if you can make something which happens instantly as in dynamic weight transfer, take a specific and longer path.  It don't matter to an instant happening what path the happening takes .... or does it?   

[dirtstudent2]

jo wants an intelligent discussion so I'm gunna give it to him....

 

Let's discuss the use of progressive/digressive spring stacking with and/or without the use of an additional bump stop/bump spring.

 

Who's using what combination, and what are the dynamic load transfer effects on corner entry, apex, and exit?

 

There is no apex racing dirt oval. 

[racepace]

Back when Bobby Allen ran it they called it a "2 step" .

[dirtstudent2]

Back when Bobby Allen ran it they called it a "2 step" .

 

Thank you

[jo73]

I remember Bobby Allen also built the right side rear suspension with a slightly longer wheelbase. His thoughts back then where when do u see a dirt car going straight on a racetrack. His thoughts if you want it square you squared the front axle to the rear.

Back in the early days of the outlaws his shop was a great place to stop by and see so many of thee travelers taking advantage of his shop. We watched team kinser cut the front clip off his primary car, a Gambler long story, and Steve had welder in hand getting the new one installed. Night 2 at the grove ? Domination, as he did many times.

[honeybadger1]

 

There is no apex racing dirt oval. 

[honeybadger1]

I like the original topic here 

can we start with a clear definition 

correct me if I'm wrong on the first two

 

Linear----gains weight equally per movement (example)  200# spring 1 inch of movement= 200#---2 inches of movement =400#---4 inches of movement=800#

 

progressive--gains more weight for more movement (example) 1 inch =200#---2 inches=425#---4 inches of movement=900#

 

now for digressive (this is where I am not completely clear) but this is what I think---

I "think" it means it gains less and less on movement 

example

1 inch of movement =200#-----2 inches of movement=375#----4 inches of movement = 700#

 

the progressive and digressive #'s are merely and example of how I think the different types of springs work

 

once we establish clear definition then we can begin discussion on application of the different types of springs (or shock)

 

Brad

yes

 

yes

 

and a digressive actually decreases in spring rate as you compress; seldom used.

 

I know these late model guys are spring stacking, ie having 1 spring rate through x amount of travel and when it gets to the second spring you have the combined rate of springs in series, K eff.

[dirtstudent2]

I didn't understand the pdf at all yesterday and I still don't understand it.

 

progressive:  You start out with a combined spring rate because the sliding divider is allowed to move when the springs are compressed giving you a combined spring rate lower then the spring rate of the weakest spring. 

 

When the sliding divider between springs hits the locking ring it stops compressing the weaker spring and spring rate "progresses" up to the spring rate of the stronger spring.  I think I understand that.

 

 

 

digressive:  You start out compressing the weaker spring against the stronger spring because the sliding divider between springs is held in place against a locking collar by the stronger spring. 

 

When the weaker spring compresses enough to push the sliding divider between springs away from its stop it starts compressing the stronger spring and the spring rate drops to combined rate lower then the weakest spring.  

 

Question:  How can you cause the weaker spring to move the stronger spring off the locking ring without having the weaker spring be a progressive spring or be coil bound?  

 

answer:  ?

 

Might the reason you don't see a digressive setup very often be because it's impossible to have a pure digressive setup?

 

I'd like to see it and understand it but I just can't see the parts working in the way described in the pdf.  I'll accept you get results on a spring smasher indicating that is exactly what happens but I don't see the parts being able to give digressive results.  I'll accept it as magic because i'm too dumb to understand it.