A little 4link help (Inner bars)

[p8ntballer1911]

Im sure this question has been answered but I cant seam to find any info on it. I know the inner triangular bars have to be 30*-35*, the only thing I am stuck on is how i would measure the angles and to be sure they are at the same angle.

Thanks ahead of time!

[Twisted Minis]

I think 35 degrees is really a minimum. I always aim for 35-45, and try to push for the 45 degree side. You generally measure the angle in relation to the axle. This can be done with an aluminum 90, or more precisely with one of those stainless angle finders, and then compared to the fast 90 or an angle finder on a flat surface.

To make sure they are the same, I like to measure from the frame to the bushing centerline. I do this at the axle, and also on the crossmember they mount to, and make sure it matches the other side.

Hope that makes sense.

[Bob@ProAuto]

Less than 45 degrees will allow the rear end to walks driver's side to passenger's side more. The less angle, the more walking.

Take a piece of poster board and cut out a triangle 45, 45 and 90 degrees. Make a transit line, using string. String a line from the center of the rear most cross member to the center of the front cross member. From this line is where you measure the 45 degrees for the bars. As your mocking up the bars the poster board template will help you to achieve 45 degrees.

You didn't specify what you were working on. on the 47-55 (1st. Series) triangulated 4-bars work well. On the 55 (2nd Ser.)-59's, they aren't ideal because the upper bars are so short that you get a sharped arc as the rear moved up and down.

[p8ntballer1911]

I started to mess with it today and I am a little confused on how i would achieve 45* angels. Here some pictures of my set-up so maybe it will be easier to explain. I did make a 45, 45, 90 triangle but it will not come close to it.

[bmeredith]

to achieve 45* with your set-up, you would need to: move your mounts on top of the axle further out, the mounts at the crossmember closer together and more importantly shorten your upper links by about a foot

[p8ntballer1911]

There are far out on the axle as they can go. I guess ill get cutting on them tomorrow!

[p8ntballer1911]

the inner bars can be shorter then the outers, correct?

[Twisted Minis]

In the first picture it looks like they could be moved out about an inch, maybe even two per side. And I would definitely shorten the upper bars. They are too long to get enough triangulation on a frame that narrow.

[FnLow69]

i would gusset those bag mounts alot more as well

[see ten]

When we built the four link under my wifes car we mounted the upper links as close as possible to the center section of the axle. Not saying that yours is wrong...We just did hers like everyone on the Hamb and Alex at Gambino Customs were building theirs.

[p8ntballer1911]

Originally Posted by FnLow69

i would gusset those bag mounts alot more as well

Yea, for sure. I just have those for mockup. Im going to but 2 more plates on each side.

[p8ntballer1911]

I have shortened the bars 10 inches each. Right now I'm getting a 65* angle. So I guess that means I need to chop them more? They are 24in and the lowers are 35in. I am at my shop right now so any quick reply would be great!

[abadsvt]

Here is how i did mine. If i remember right i got about 40degs. That was the most i could get for my setup. I know my bars are shorter than yours but the pinion angle change through my suspension cycle wasn't much at all. Plus i plan on driving it at the ride height so normal driving i might go through 3" of suspension travel. I think my upper bars where 18" +or-. I know you are mounting yours bars different but maybe it will spark an idea. One nice thing about mounting the bars outside aiming inwards is that it allows all that space for mufflers, or batteries and so on. Anyways here are some pics.

Josh

[Twisted Minis]

You might want to consider a wishbone then. If you shorten your upper bars too much, you will eventually end up with a setup that has a lot of pinion angle change. A wishbone, or triangulated 3-link will locate your axle well, and it can take just about any shape you need.

[p8ntballer1911]

Ok. Heres where im at now. Im really not sure what to do. Should i chop the bars more? A wish bone wouldn't be a bad idea, but i already have everything for this 4link so i would like to make it work!

[scotts62]

Hey Twisted Minis do you have a pic to post to help him out a little?

[Twisted Minis]

I might.

It looks like you have enough triangulation there, but you have to be aware of where your driveshaft will come into play. It will hit your mounts where they are at. And if you move them up above the drive line you will possibly end up putting your instant center behind the axle. Not desirable.

It also looks as if you could build a wishbone out of the links you have. If you have one of the threaded ends you cut off, you could build something like this.



Here is another setup. The bars are not a perfect 45 degrees, I think I remember them being about 38-40 degrees

[p8ntballer1911]

Originally Posted by Twisted Minis

I might.

It looks like you have enough triangulation there, but you have to be aware of where your driveshaft will come into play. It will hit your mounts where they are at. And if you move them up above the drive line you will possibly end up putting your instant center behind the axle. Not desirable.

It also looks as if you could build a wishbone out of the links you have. If you have one of the threaded ends you cut off, you could build something like this.

Well that triangle i have in the picture is a 45,45,90*. Maybe im over thinking/looking at this but the angle of my bars are at a 65* angle. maybe im measuring wrong?

[Twisted Minis]

I am for a 70-90 degree angle. I think about 35 degrees per bar is a minimum, but some people say 30. I think the extra 10 degrees total makes a big difference in lateral stability.

Are you against a parallel type setup with a panhard bar or watt's link?

[p8ntballer1911]

Originally Posted by Twisted Minis

I am for a 70-90 degree angle.

What do you mean? Will the 65* angle my bar is at work?

i was thinking about just doing a parallel like you said. I might end up having to.

[Twisted Minis]

It probably will work. But look at what I said before about your pivots and your drive line. They will probably interfere if your link geometry is correct.

[p8ntballer1911]

Yea, i understand that. I guess if i trim the bars another 2in, it will keep the same angle and be out of the way of my drive shaft.

[Twisted Minis]

You should check that with the bushings and driveshaft installed.

[p8ntballer1911]

Yea i can get all that figured out. I just need to be sure the angle I am at will work and not have any major problems. Oh and thanks ALOT for your help and quick replies!

[p8ntballer1911]

Well i'm a little confused. Do you measure the angle from the frame rail or axle? If its from the frame rail then I am at 25* but from the axle I am at 65*