Birdcage, Bar position?

[Kromulous]

STD being the 4.5" off center, both bars.

Speaking of the LR, what happens when you move the bar up on the BC to 5.5"?

Considering its a zero index deal, 12 to 6 on the holes, but also fwd 1" on top, 1" behind center on the lower.

Would moving to 5.5" on the top bar give the force generated by the rear end more leverage on the top bar ?

Reading a lot about force based instant centers, i noticed it moves the IC aft a bit and lower, but trying to figure out other side effects.

Thanks, Krom

[MasterSbilt_Racer]

As you move a bar away from the axle centerline, you remove force from it.

[Kromulous]

Thanks, MBR.

Brings up another question LOL.

If it loses force, moving 1 bar out (top bar), does that force get applied to the closer to CL bar (Lower)? or does it get lost or not generated by the rear end?

Which bar would you want to amplify the load on, another question i guess LOL. Being semi-retired these days, gives me time to ponder things, very dangerous...

[billetbirdcage]

Considering its a zero index deal, 12 to 6 on the holes, but also fwd 1" on top, 1" behind center on the lower.

Krom, did you say that backwards? No index is with the top bar backwards and the lower bar forward. STD is more with the bars static on cage at 12/6 ish and no index is 1/7 ish


Would moving to 5.5" on the top bar give the force generated by the rear end more leverage on the top bar ?

Moving the bar on the cage up to 5.5 will significantly reduce the thrust on the entire LR suspension

[billetbirdcage]

https://i.imgur.com/jJE11Ii.png

Blue or red lines going to black circles are the bars and the line from the intersection of those lines to the center of the axle is the thrust angle the rearend puts on the bars. This is only a drawing at ride height and dynamic will be a greater difference in thrust between the 2 (red vs blue)

[Kromulous]

So you say it reduces overall thrust on the entire LR? i have been plotting out the IC on paper today, and my DWG similar to yours shows the same, so moving that IC further aft from the BC reduces the force?

I must be confused = nothing new there. But yes, i am 1" fwd on the top bar, and 1" aft on the lower bar. So as you described i am backwards ? BCs we have a bubble on the bottom, so i just keep the bubble centered at full droop.

Actually i checked it and am just 1" fwd on the top bar, std on the lower.

[billetbirdcage]

https://i.imgur.com/iyribv4.png


Frame side on left and cage on right

There are many ways or things you can do here, but the general std no index deal is this ^^

STD would have bars static close to 12/6 and more like 10:30/4:30 at full hike (close to over centering cage)

No index would have bars static close to 1/7 and more like 11:30/5:30 at full hike (long ways from over centering)


***Note to move bars on cage you have to move on frame or change length of bar or you will move the rear end forwards/backwards and change the static wheel base.

[ZERO25]

Anything to gain with the zero index billet, esp on a 602 crate?

[HuckleberryB4]

Maybe I'm missing the entire mechanics of zero index....but it still makes "zero" sense to me. Even after reading all of the threads/posts on it. How is a zero index setup any different than if I run a LR digressive stack that drops out to zero at full droop? Wouldn't a digressive stack be beneficial over zero index since it helps thrust the car up initially? Again, maybe I'm misunderstanding the purpose of zero index, but I just can't wrap my head around it.

[MasterSbilt_Racer]

Maybe I'm missing the entire mechanics of zero index....but it still makes "zero" sense to me. Even after reading all of the threads/posts on it. How is a zero index setup any different than if I run a LR digressive stack that drops out to zero at full droop? Wouldn't a digressive stack be beneficial over zero index since it helps thrust the car up initially? Again, maybe I'm misunderstanding the purpose of zero index, but I just can't wrap my head around it.

The closer you come to over indexing, the more you have mechanical antisquat. The suspension loses more and more compliance. Your tire becomes all the suspension. Your suspension becomes useless.

[Kromulous]

Then is mechanical anti-squat a bad thing? to some extent? I am gonna say that it is a typical race car deal, its good and bad, just what can you live with kinda thing.

My question is on zero index deal is how much load is on the LR tire, via bar angle (mechanical leverage) via rear end thrust applied thru the IC's or droop load?

IF your digressive, and zero'd out on droop load (at full hike) its all mechanical, via bar angle, applied by the rear ends force. So that would mean you would have some mechanical anti squat, i guess the secret is calculating that number and knowing where you need to be on given track conditions, or am i in left field?

Because i have not gotten to work well so far, but i keep trying LOL...

[MasterSbilt_Racer]

Then is mechanical anti-squat a bad thing? to some extent? I am gonna say that it is a typical race car deal, its good and bad, just what can you live with kinda thing.

My question is on zero index deal is how much load is on the LR tire, via bar angle (mechanical leverage) via rear end thrust applied thru the IC's or droop load?

IF your digressive, and zero'd out on droop load (at full hike) its all mechanical, via bar angle, applied by the rear ends force. So that would mean you would have some mechanical anti squat, i guess the secret is calculating that number and knowing where you need to be on given track conditions, or am i in left field?

Because i have not gotten to work well so far, but i keep trying LOL...

When your chain is tight, there is no relative motion. That means the sum of all forces is zero. The only load is the weight you lifted.

Go back and watch guys hit a hole at Eldora in 2014. They may bounce 4 times. That ain't fast.

[ZERO25]

Tader has a pretty good video on Racer Know How.

Its gotta help some when at full droop, the heims on the trailing arms are very free and not bound up!

[Jking24]

Maybe I'm missing the entire mechanics of zero index....but it still makes "zero" sense to me. Even after reading all of the threads/posts on it. How is a zero index setup any different than if I run a LR digressive stack that drops out to zero at full droop? Wouldn't a digressive stack be beneficial over zero index since it helps thrust the car up initially? Again, maybe I'm misunderstanding the purpose of zero index, but I just can't wrap my head around it.To simplify it a little further. Plain and simple if the bars get close to over indexing (flipping the bird cage) the suspension goes ridged. Kepping aero out of the equation This creates max traction. on a smooth surface but on a rough surface it will cause the car to bounce and you can't have traction when your tire is off the ground. Also when the lr suspension goes ridged your spring rate is infinite you cant tune that so all these fancy digressive stacks become less or not effective

[hunterracing]

What if you lower the lower bar to 5.5 will that move the thrust back fwd?

[Kromulous]

Yeah i would like to know that to Hunterracing, its something i havnt gotten a lot of answers on so just gonna try it LOL!

Also, if these are the bar postions for zero index, top back, bottom fwd, then what is it that the XR1s are running? The ones i look over, the top bar is fwd, and the bottom bar is aft. Seems like that would still be a zero index deal, with a shorter steeper instant center, and thrust angle?

[hunterracing]

I would think if you raised top to 5.5 then lowered the bottom to 5.5 it would kinda equal it self out but guess depends on bar location on frame but not sure I’m right bout it. Wehrs saids raising on cage to 5.5 upper will make tighter in and looser off

[MasterSbilt_Racer]

Yeah i would like to know that to Hunterracing, its something i havnt gotten a lot of answers on so just gonna try it LOL!

Also, if these are the bar postions for zero index, top back, bottom fwd, then what is it that the XR1s are running? The ones i look over, the top bar is fwd, and the bottom bar is aft. Seems like that would still be a zero index deal, with a shorter steeper instant center, and thrust angle?

Ignore where the bolt is compared to other holes. Where are the two birdcage attachment points in relationship to each other? Don't forget the coilover attachment point is working in an arch too.

[cjsracing]

I've been playing with this a lot in the shop lately. Isn't the point of zero index to get more bar angle without over indexing?

[Kromulous]

Yeah, and to keep some compliance with the shock to the track, keep rubber on the road so to speak.

I mapped it out on paper, and the XR1 way seems to allow you more upper bar angle, and still be zero index. It brings the Instant center closer to the rear end, and more upward angle. Plus less lower bar angle, which potentially could allow you to run more droop overall, or with less rear steer. Bar lengths would change, 1" longer lower, 1" shorter upper, so the split in lengths could be closer if you wanted that, depends on your 4 bar plates.

Or am i off in my thinking? LOL wont be the first time...

[Jking24]

The xr1 keeps the bar lengths the same the whole top bar is moved rearward and the bottom is moved forward at ride height. The shock location and the indexing are virtualy unchanged. Basically it just clocks the starting point back

[MasterSbilt_Racer]

The xr1 keeps the bar lengths the same the whole top bar is moved rearward and the bottom is moved forward at ride height. The shock location and the indexing are virtualy unchanged. Basically it just clocks the starting point back

That's one of the deals out there. And what everyone was first calling "zero index". Krom is right there are deals out there using the most front hole on the cage, yet are still 12 o'clock and 6 o'clock at full hike. I'm not sure how those are set up. And I've seen that on rockets as well.

[Kromulous]

Spent all weekend at the North South, looked at every XR1 there and there are all on it. Top bar FWD 1", Bottom bar AFT 1" with the birdcage straight up and down at full droop, not the bolts, the cage is straight up and down. Top bar ends up with some extreme angle in it, and the bottom is somewhat neutral.

Still looking into it.

[Kromulous]

Double post, but i will end up trying it soon.

[Jking24]

Spent all weekend at the North South, looked at every XR1 there and there are all on it. Top bar FWD 1", Bottom bar AFT 1" with the birdcage straight up and down at full droop, not the bolts, the cage is straight up and down. Top bar ends up with some extreme angle in it, and the bottom is somewhat neutral.Still looking into it.Not sure i follow you 100% are you talking about on the cage or the chassis. Their are three sets of holes on each

[Kromulous]

I am speaking of the birdcage holes, fwd set on the top, back set on the bottom. I didnt pay attention to the chassis side.

IF there keeping the bar lengths the same, would make since to have 3 sets of holes on the chassis plates.

Can anyone see this image?

[hunterracing]

If the top bar gives the tire more drive instead of raising up on cage can you not just lower the bottom
To 5.5 and lower it on frame wouldnt this give car more drive and keep it straighter off corner?

[Jking24]

I am speaking of the birdcage holes, fwd set on the top, back set on the bottom. I didnt pay attention to the chassis side. IF there keeping the bar lengths the same, would make since to have 3 sets of holes on the chassis plates.Can anyone see this image?Can't see the image but that is the "standard position" for a xr1 top bar all the way forward bottom all the way back it can be deceiving because the way the birdcage plates are cut. It looks like they are at six and twelve at full drop but they are not. That being said the xr has alot less indexing then the older stuff when all bars, lengths and positions are standard .

[dirtdobberrr]

Listen guys, I fancy myself a setup guy. I do not have alot of experience driving, I did drive a bomber car for 2 years, but I did not have time to work 50 hours a week and race, so 12 years ago I choose to concentrate on helping others with their cars. I feel that I am above average at observing a car of any class go around the track, and I also very much enjoy 3/4 link cars and discussing what makes them work. The first thing I noticed about the Longhorns/xr1's/later cvr'sl capitals was that they rolled the middle of the corner on the throttle MUCH better than the stuff before them. Since the late 1990's, the 4 bar stuff was extremely tight from the middle out. I the 1990's they were almost drag cars that raced twice per lap, on dirt. The newer stuff rolls the middle and out much better on the throttle, which can only be due to a few things............softter effective right front spring rate, and/or more rebound rate on the right front...........or less left rear drive, caused by less left rear drop as measured by total number of left rear drop in inches, or murch more left rear rebound rate, which causes the left rear to drop much more slowly as throttle is applied. Add to this the addition of right front bump stops, and one pretty much has the magic of all these new chassis out there. There are some aero related things that have changed, and rear weight % is probably 5-6% less than it was, and right side is probably down 4-5 percent, and most are running the lift bar spring (5trh coil) back 3-6 inches less than they were 6 years ago. That is pretty much your modern $40,000 late model chassis vs one from 5 years ago. If I am wrong, tell me I am wrong. Also, the modern car bodies are tappered pretty much as much as the rules are allowed, and i mean the (not a nice word)(not a nice word)(not a nice word)(not a nice word)pit is lower, the front end is more narrow, the right front nose piece has been move down as much as the dynamic roll will allow. If I did not work 50+hours a week driving a fuel truck, I would build "Bubba's Fast Ass Chassis". But since I am poor and work alot, I can only reach a few, and only a few of these will listen, most have drank the cool aid and they believe that only the people on tv can help them. Tell me that I am wrong.

[MasterSbilt_Racer]

Are you saying guys are running less than 50% left side weight?

[Jking24]

Listen guys, I fancy myself a setup guy. I do not have alot of experience driving, I did drive a bomber car for 2 years, but I did not have time to work 50 hours a week and race, so 12 years ago I choose to concentrate on helping others with their cars. I feel that I am above average at observing a car of any class go around the track, and I also very much enjoy 3/4 link cars and discussing what makes them work. The first thing I noticed about the Longhorns/xr1's/later cvr'sl capitals was that they rolled the middle of the corner on the throttle MUCH better than the stuff before them. Since the late 1990's, the 4 bar stuff was extremely tight from the middle out. I the 1990's they were almost drag cars that raced twice per lap, on dirt. The newer stuff rolls the middle and out much better on the throttle, which can only be due to a few things............softter effective right front spring rate, and/or more rebound rate on the right front...........or less left rear drive, caused by less left rear drop as measured by total number of left rear drop in inches, or murch more left rear rebound rate, which causes the left rear to drop much more slowly as throttle is applied. Add to this the addition of right front bump stops, and one pretty much has the magic of all these new chassis out there. There are some aero related things that have changed, and rear weight % is probably 5-6% less than it was, and right side is probably down 4-5 percent, and most are running the lift bar spring (5trh coil) back 3-6 inches less than they were 6 years ago. That is pretty much your modern $40,000 late model chassis vs one from 5 years ago. If I am wrong, tell me I am wrong. Also, the modern car bodies are tappered pretty much as much as the rules are allowed, and i mean the (not a nice word)(not a nice word)(not a nice word)(not a nice word)pit is lower, the front end is more narrow, the right front nose piece has been move down as much as the dynamic roll will allow. If I did not work 50+hours a week driving a fuel truck, I would build "Bubba's Fast Ass Chassis". But since I am poor and work alot, I can only reach a few, and only a few of these will listen, most have drank the cool aid and they believe that only the people on tv can help them. Tell me that I am wrong.Couple of problem here, the noses are wider then ever, the droop is more than ever and their actually running more right side weight than previous years

[Kromulous]

Thanks Jking24 on the "STD" bar positions, there are a couple things that XR1's do better than all the other cars out there, and i am trying to decode it and apply it to my situation.

Leftside %, yes getting lower. I made that mistake the last couple years, to much and the car wont dig in on the right side. Plus these droop loads i am running now days are insane, i never would of thought to go that high...

Rear % is another one, you would think higher % would be more traction, but really isnt, and it makes the car swing bad sometimes.

The RF is really simple, but hard to get right. Soft to get in the corner faster, but stiff down in the travel to get off the corner well. The combo to get right is a pain, plus you have to drive it properly. I also think the LR load numbers are crucial, to the equation.

Hunterracing, i think your on to something there, but have no actual testing to back it up. Using MBRs logic, closer to CL rod on BC gets more load, it would make since. Its something else i want to try. I believe it would be a way to keep the car in the proper posture, easier, the upper rod getting more load to keep the LR up, at all times.

[Dirtmod13]

i couldnt open the pic, ill pm you. send it to my email