Another anti roll bar solution

[kabacj]

Using many of the ideas presented by the community for inspiration I came up with the following solution for a front anti roll bar. The goal was to allow for adjust ability as well as a linear a spring rate as possible. No i am not an engineer so I don't have any fancy software to validate if this will work, however I am happy with how it travels through the range of motion as well as the ability to adjust the rate.

The way it is setup now it will allow for 109 to 139 lbs of force at 5 degrees of twist with 10 increments in between. The link is just a piece of black pipe I used for mock up. Ill replace that with a proper link as soon as I can find one I like.

a few pictures.

John

rollbar3b.jpgroll bar 1b.jpgrollbar2b.jpg

[afourcault]

looks good i like the fact that we have so many options for swaybars now.

[kabacj]

looks good i like the fact that we have so many options for swaybars now.

Thanks! I heavily reenforced the front frame to support both the ARB as well as a subframe for a nice tow hook that fits in the grill. I wanted a hook that will still allow the hood to pivot. All the ARB parts are easy to get online the only hard part is bending the arms. If you have a press its not so bad. The only gotcha is you will need to move the struts that raise the hood from the normal location near the upper A arm pickup. I ended up moving them to near the cowl and down the hood to near nose. The benefit of this mod is to lower the effort requred to lower the hood as the struts loose mechanical advantage as the hood lowers. If anybody wants to see that I would be glad to share.

[crash]

Just an FYI...that bend in the sway bar arm will decrease the effective rate of the bar substantially. It is pretty much unavoidable if you want to keep a good amount of steering angle, but I just thought I would make you aware of that if you weren't already. Looks really good.

[kabacj]

Just an FYI...that bend in the sway bar arm will decrease the effective rate of the bar substantially. It is pretty much unavoidable if you want to keep a good amount of steering angle, but I just thought I would make you aware of that if you weren't already. Looks really good.

Yeah, I knew that intuatively however... The way I figured the bend will lower the rate of change over the bent section as you move away from the pivot point, however the rate at say 13 inches and the rate at 10 inches are the same regardless of if the arm is bent or not right? (throw out the change in link angle and measuring perpendicular to the arc of travel) I figured assuming the arm is perfectly rigid... and for my calculations it is.. the only thing that matters is how far from the pivot the link is attached again mostly guessing at the actual engineering forces.

[crash]

I do not think that what you are saying, if I understand correctly, is right.

The bend in the connecting arm will introduce a moment that will change the rate of the bar. Do to the bending properties and the angle of the connecting arm, I do not believe that the rate will be linear either.

All that said, I have alwaysdone what I had to do to get the link as perpendicular as possible and then simply tuned the bar size with the resulting connecting arm until the car performed "properly".

So, yes, I think you are on the right track with what you have there.

[kabacj]

I do not think that what you are saying, if I understand correctly, is right.

The bend in the connecting arm will introduce a moment that will change the rate of the bar. Do to the bending properties and the angle of the connecting arm, I do not believe that the rate will be linear either.

All that said, I have alwaysdone what I had to do to get the link as perpendicular as possible and then simply tuned the bar size with the resulting connecting arm until the car performed "properly".

So, yes, I think you are on the right track with what you have there.

Right thanks for the input. Although its possible to model lots of stuff these days, there are so many factors some times its quicker and easier to guess and test.



John

[crash]

Absolutely agree. As I like to say "The proof is in the pudding..."

[afourcault]

oh lord.. i think i heard bill cosbys voice there for a moment..*shudders* idk why but that guy creaps me out...

[JCHRacer]

Nice work John,

I agree with Crash....try to keep the link as close to verticle as possible to minimize spanwise bending in the bar. Bar bending can sometimes lead to the bar binding up in the pillow blocks and resulting unpredicable handling behavior. What kind of bearings and clearances are you running in the pillow blocks?

My calculations indicated that a big bar was not required for the front (mine is just 3/4 inch diameter hollow tubing)......but numbers are just a start......the real proof is in testing. It will be interesting to see what your size bar does to the balance. Please keep us up to date.

[kabacj]

Nice work John,

I agree with Crash....try to keep the link as close to verticle as possible to minimize spanwise bending in the bar. Bar bending can sometimes lead to the bar binding up in the pillow blocks and resulting unpredicable handling behavior. What kind of bearings and clearances are you running in the pillow blocks?

My calculations indicated that a big bar was not required for the front (mine is just 3/4 inch diameter hollow tubing)......but numbers are just a start......the real proof is in testing. It will be interesting to see what your size bar does to the balance. Please keep us up to date.

Hi Joel,

For bearings I am running Spyraflow Pb4-1000-P self aligning high performance Teflon bronze bearings . They are a good interference fit. I can press them on by hand, however. They allow for 5 degrees of misalignment so hopefully that will allow for some bending without any binding in the bearing. I am running a 36" x 1 " .095 hollow bar.

My theory was that I could lower the front spring rate using my adjustable dampers as well as adjustable ARB to compensate for a more compliant spring. I would try to deal with static load, shock loads and cornering loads somewhat independently . That's the theory anyway. Testing will tell.

Whats your opinion on a rear bar? I figure it would be nice tuning variable to have but am a loss of where to start rate wise. I don't know of anybody who has tried a rear bar setup.

Thanks
John

[JCHRacer]

Hi Joel,

For bearings I am running Spyraflow Pb4-1000-P self aligning high performance Teflon bronze bearings . They are a good interference fit. I can press them on by hand, however. They allow for 5 degrees of misalignment so hopefully that will allow for some bending without any binding in the bearing. I am running a 36" x 1 " .095 hollow bar.

My theory was that I could lower the front spring rate using my adjustable dampers as well as adjustable ARB to compensate for a more compliant spring. I would try to deal with static load, shock loads and cornering loads somewhat independently . That's the theory anyway. Testing will tell.

Whats your opinion on a rear bar? I figure it would be nice tuning variable to have but am a loss of where to start rate wise. I don't know of anybody who has tried a rear bar setup.

Thanks
John

Excellent choice on the pillow block bearings....should eliminate any bending/binding issues.

The big front bar/low front spring rate forces you to run a higher front ride height to keep the chassis off the ground under hard braking. The big front bar set-up makes sense for a street driven car or a race car on a very bumpy track.....for a race car on a relatively smooth track, less so......so it depends on what you are trying to acheive with your car/set-up.

As far as rear bars....kinda the same..... it depends on what you are trying to acheive with your car/set-up. I am not a fan of rear bars on race cars because it decreases traction coming out of corners (very important to lap times).......at most it should be sized to fine tune the balance. For street driven cars makes alot of sense.....since I am building primarily a track car, I haven't put much thought into it.

[kabacj]

Makes sense Joel. My goal is a track day car that I will also register to drive on the street. I'm prepared to compromise the street for a well mannered track car. I am looking forward to the development phase of the car. Although none of us have a million dollar budget to develop the car hopefully we can share what worked with the setup and save us all some time and money.

Thanks for the help.

[kabacj]

Excellent choice on the pillow block bearings....should eliminate any bending/binding issues.

The big front bar/low front spring rate forces you to run a higher front ride height to keep the chassis off the ground under hard braking. The big front bar set-up makes sense for a street driven car or a race car on a very bumpy track.....for a race car on a relatively smooth track, less so......so it depends on what you are trying to acheive with your car/set-up.

As far as rear bars....kinda the same..... it depends on what you are trying to acheive with your car/set-up. I am not a fan of rear bars on race cars because it decreases traction coming out of corners (very important to lap times).......at most it should be sized to fine tune the balance. For street driven cars makes alot of sense.....since I am building primarily a track car, I haven't put much thought into it.

Hi Joel I noticed your roll bar solution in your photobucket link. Once I saw it I rembered back when I was lurking on the other board the discussions that were had about your front suspension setup.

it looks like your solution has the bar runing crosswise just at the rear of the front compartment. I also noticed that you have a shot with the AC evaporator. http://i926.photobucket.com/albums/a...roll_bar_3.jpg How did you get the bar accross without hitting the AC fan? My setup has the fan inside a blow molded housing right in the same location you have the bar on your drawing. Obviously thats a great place for the bar, just wondering how you delt with the AC.