3-Link Build

[Probird]

Looking for some constructive criticism. Do you guys think that my panhard bar mount is strong enough or should I do some additional bracing. The photo's should give you a good idea of what I'm talking about. The tubing is 1-1/4" .120 wall welded on 3/16" plate. Just want to get this right the first time! The car is a 70 Nova.

[Bryce]

I think you need to add more bracing. It needs to be gussetted in the direction of the force add a brace to the opposite frame rail.

[Probird]

That's basically what I was thinking, thank you. I think I'm going to bend some tubing to go about mid way down my existing mount and then tie it into the coilover crossmember instead of going all the way to the other frame rail. Things are getting pretty tight pretty quickly. I think that should do it, I know that I definately need to gussett the axle clamp.

[Bryce]

That should work. Here is an example of an axle brace that I used on my falcon watts link.

https://static1.pt-content.com/images/pt/2011/03/tn_full_DSC03879-1.jpg (http://www.motortopia.com/photos/602791)

https://static1.pt-content.com/images/pt/2011/03/tn_full_DSC03880-1.jpg (http://www.motortopia.com/photos/602792)

[Probird]

That's some nice fab work, good job! I can't wait to get the fabrication done so I can start cleaning things up and get it all painted under there. I was actually reading your build earlier today, still lot's of reading to go. You've definately come a long ways and I really like the aluminum mount on the rear for the watts.

[MrQuick]

im with bryce, gusset that axle housing mount and run a bar from the frame bracket to the opposite frame OR to that coil over mount. That bar sees alot of force.

[Norm Peterson]

Yes, you definitely need to run a lateral brace for that chassis side bracket. Given that it appears you've left lots of opportunity for adjusting the PHB height, I'd make the brace adjustable so that you could mount it no higher than the second hole above wherever you put the PHB.

I'd also brace the axle side post, because it will see the same amount of lateral force as the chassis bracket trying to bend it over and/or peel the clamp up.


Norm

[Norm Peterson]

I'll add that an upper lateral brace for a PHB is original fitment on the S197 Mustangs, which have a 3-link/PHB rear suspension as the OE design. You might see this brace referenced to as being an "upper panhard bar" in the various Mustang forums (incorrectly, as it is strictly a structural component with no kinematic function).


Norm

[David Pozzi]

There is a lot of lateral force on the Panhard bar. It will be equal to the rear weight of the car plus a safety factor. 4000 lbs or so?
I'm figuring a rear weight of 2000 lbs with a safety factor of X2.

[Norm Peterson]

It took me a little searching to find it, but there seems to be some consensus with respect to a "3/4/5 rule", where

3G's is in the lateral direction
4G's is in the longitudinal direction
5G's is in the normal direction...

Those figures are taken at the contact patch(es) and account for impact loading, so for a PHB the main consideration is the 3g's laterally. The other two directions wouldn't see much more load than the 4 or 5 factor times the weight of the PHB itself and could probably be neglected.


Edit - that does not keep you from using a slightly higher figure to account for fatigue, particularly if it is not a race car that gets regular inspection & maintenance. In fact, a race car without much aero downforce and restricted to [relatively smooth] paved tracks can get away with using slightly lower numbers than 3/4/5.


Norm

[Probird]

Thanks for all the great feedback. Norm I really like your idea about making it adjustable, now I just have to figure out how I can do that and not kill my exhaust routing. Running a brace to the other frame rail is out of the question. I had to offset the upper link rearend bracket 3-1/2" behind the center of the rearend in order to acheive a decent length for the third link, it will be around 13-14" when all is said and done. I offset the bracket on the rearend 10-1/2" to the passenger side and routing my exhaust on that side will be tricky at best. I did look at how Heidts ran there panhard for their 4-link and noticed that they made it in a long u-shaped hoop that drops down to almost the center of the rearend, my guess would be it was for exhaust routing. The more I think about it the more I think it will work for me. Just means that I am starting more or less from scratch unless anyone else has a better idea.

[exwestracer]

Since the axle end is non-adjustable, I'm going to go out on a limb and say you are probably never going to want to use the top 2 holes. That would put a LOT of split (angle) in the bar, which is fine if you're circle track racing, but not so cool for turning both ways. I would plate the bracket over those 2 holes (better yet cut the plates off and go to the tube itself) and build a gusset bar to go in there and tie in as far over on the shock crossmember as you can get. The idea is just to take the shear load off the welds.

[Probird]

I just finished doing that exact same thing. I cut the plates just below the top 2 holes and then welded a tube from the crossmember to the panhard bar mount. The axle end is actually adjustable, just loosen the clamp and roll it up or down. I can adjust it 3" up and down, I also gusseted the axle mount. I'm pretty sure the only weak link is going to be the axle bracket itself. The tubes that the bolts run through on the axle clamp will go long before anything else but I figure that since it's a circle track bracket it will hold. I actually plan on welding the bracket to the rearend once I get the ride height set. I figure that the bracket itself is meant to be welded, the bolts are just for mocking things up. Now that almost all of the fab work is done I can move to the front end. I pick up the motor from the machine shop next week. It should take me about a month to get it assembled, +/- a month or two.lol...I'm old school and building a good old fashioned BBC, a 396 bored .090 to be exact. Once I get the motor together I can set the ride height and then drill the holes for my third link to establish my anti-squat. Thanks again for your input and I'm sure you'll be hearing from me again in the near future!

[exwestracer]

I actually plan on welding the bracket to the rearend once I get the ride height set. I figure that the bracket itself is meant to be welded, the bolts are just for mocking things up.

Right. Non-adjustable... :twothumbs

[rustomatic]

For a design to possibly copy, relative to the diagonal support (or possibility thereof) in discussion, check out Maier Racing's adjustable Panhard bar (for Mustangs). I've got one on my Falcon, and it seems to work quite well. It has made my steering feel rather useless, in fact, since the rear axle no longer moves like a pair of chubby hips... Out of embarrassment, I just began the install of a new rack and pinion setup...