Strengthening Front Anti Sway Bar Mounts

[rc's240z]

Jon this is very similar to the solution sold by DP Racing that I have on my 240 Z the mounts for the front rod ends are very much like what you have put together other than the DP Racing bar is hollow and the holes for the endlinks are drilled into the bar already.

 

I like what you are doing retrofitting and existing bar for adjustability. Let us know how it works...

 

Ron

[JMortensen]

I wish DP had all of the crap they sell listed on their website. Oh well, it would probably have cost $1000 anyway, so I probably still wouldn't have bought it. It would be VERY easy to switch this into a tubular circle track style bar down the road, so that will probably happen somewhere down the line, but this is good enough for now.

[JMortensen]

It's been over a year since I got this project done, but I just did some related work and thought I'd share. I wanted to know what my swaybar spring rates were, so I measured it.

 

I had to try a couple different methods to get the swaybar figures. What I ended up doing was bolting the bar mounts to some square stock and clamping that to my workbench. Then I attached the end link to another piece of square stock and set that on a bathroom scale. Then I took a piece of pipe, put it over the free end of the bar and moved it down one inch at the appropriate end link hole and read the scale on the other side to get the bar rates.

 

What I came up with was that the front bar has a min rate of about 105 lbs/in and a max rate of 120 lbs/in. The rear had a min rate of 50 lbs/in and a max of 80 lbs/in.

 

I don't know why, but I was really expecting hundreds of lbs of force there. I was pretty surprised at how light the bars are.

 

Again, these started life as the MSA front bar and the ST rear bar, with all of the modifications listed in this thread for adjustability. The rear bar is surprisingly adjustable, and I was pretty shocked that I could almost double it's force by adjusting from the lightest to heaviest setting.

[JMortensen]

I think Cary and I figured out that my sway bar readings are 1/2 of the actual numbers. I was measuring the force on one side, and not measuring the force on the opposite end of the bar. So I think my numbers should effectively be doubled to 210 to 240 for the front bar and 100 to 160 for the rear bar.

 

Instinctively that sounds better. Anyone know if this is right or wrong?

[johnc]

No, I think the original number is correct. Equal and opposite reaction thing. Hang a known weight off the free end of the bar in the fixture you've set up and read the measurement on the scale.

[tube80z]

No, I think the original number is correct. Equal and opposite reaction thing. Hang a known weight off the free end of the bar in the fixture you've set up and read the measurement on the scale.

 

If I have a known weight why am I measuring it on a scale? Wouldn't I measure deflection of the bar in this case?

 

Cary

[johnc]

We're trying to validate the measurement process. Does a 200 lb. load on one end of the bar show up as a 200 lb load on the scale? It should.

 

If, for some reason, a 400 lb. load on the free end of the bar shows up as a 200 lb. load on the scale, where did the other 200 lbs. of load go? It has to go somewhere and if it disappears into the bar as deflection I think that bar would heat up significantly.

[JMortensen]

I set a 25 lb weight on the very end of the bar and it registered 25 lbs on the close hole on the opposite side. I moved the end link to the last hole and it measured 22 on the scale.

 

So it sounds like the original numbers were right...

[johnc]

Remember, 1" of ARB deflection is 1/2" of suspension travel, assuming equal movement on each side of the car.

[WizardBlack]

We're trying to validate the measurement process. Does a 200 lb. load on one end of the bar show up as a 200 lb load on the scale? It should.

 

If, for some reason, a 400 lb. load on the free end of the bar shows up as a 200 lb. load on the scale, where did the other 200 lbs. of load go? It has to go somewhere and if it disappears into the bar as deflection I think that bar would heat up significantly.

 

It can't disappear as heat. Work or energy can turn into heat (different form of energy) but a force cannot. The original measuring method was the correct one.

If you have X lbs of force on one end of the bar, you have the exact same thing on the other end assuming the bar is free to pivot with respect to the chassis (which your test replicates of course).

OTOH, you can consider that your 100 lbs/in. correlates to 100 pounds of force per inch of total bar travel and not just the travel of one side. So, it depends on what exactly you are defining as your swaybar 'rate'. That may be where your intuition is trying to tell you it should be doubled. It will take 100 to 160 pounds of force to get EACH SIDE of the rear sway bar to move 1 inch for example; or two inches of total travel. I am sure you get what I'm saying.

EDIT: VERY cool thread by the way. Thanks for posting updated info. Perhaps some completed pics of the frame braces and swaybar mounting? Half the pics in the thread went into the internet black hole.

 

Mark

[JMortensen]

Yeah I moved and changed ISPs and all the pics that weren't hosted here went byebye. I'll see if I can't dig them up and just post the important ones.

[JMortensen]

 

 

 

 

 

 

 

 

 

[WizardBlack]

Thanks Jon! That is some series beef you put into it. Hmm, I guess I am gonna have to do this soon; one of my frame rails is cracked at the swaybar mount, too.

 

Mark

[MONZTER]

Here is how I fixed my setup. Same problem with the mounts cracking, as I have been using heim joints on the ends and solid aluminum with 20% glass filled Teflon bushings for the pillow blocks. I wanted to keep a factory look to it so I made the gusset plate similar to the existing gusset on the cross member pick up. I rosette welded it on and through the bottom of the rail. The good part for me was no burned up paint in the engine compartment as it is covered by the frame rails.

 

I saw mentioned earlier about mounting the sway bar end links to the strut, this is how I have mine. Two reasons why I did this. First I could use a longer end link, minimizing the movement of the link, and lessening the chance of binding, and second, by mounting the link on top I could put the bar down closer to the control arm, improving the angle of the bar. I was looking for the bar to be flat when under braking. John, do you remember that article a while back in Race Car Engineering, where they talk about the rate of the bar changing as it rotates and the angle of the end link moves from perpendicular relative to the bar? They suggested that this could be an advantage. Has you read this article? Seems like most of the new cars are done this way, any disadvantages?

 

Here are some pics.

[JMortensen]

I think hooking to the strut has only advantages and no disadvantages. The problem that I had is that I couldn't seem to get it mocked up in a way that would allow full suspension travel without the sway bar hitting the tie rod. If I were to do this project again I would now have different tie rods which aren't bent and would allow a little more clearance, and I'm also planning on running a stiffer spring rate so I probably wouldn't worry as much about binding and would instead just limit the suspension travel.

 

I haven't read the article, just got my first issue of RCE this week. I have heard of the angle of the end link changing the amount of force on the control arm before, which is why I tried to set them up level at ride height, and also why I mounted the lower part of the rear end links under the control arm. That allowed me to lengthen the rear links by about 2".

[MONZTER]

Yes I know what you mean about the bar hitting the tie rod. Keeping the bar close to the frame rails helps with this, but your idea for a different tie rod is perfect. I built some straight tie rods from 4340 with heim joints on the end to adjust for bump steer, as well as give more clearance on lowered cars. Have not tried them yet.

The tricky part about making the tie rods was the fact that one of the inner tie rods uses an m14x1.5 left hand thread. I found that if you call McMaster Carr they can custom make any tap you want for a reasonable price.

 

[JMortensen]

Man your work is freakin awesome... big time jealous of your skills over here.

 

I haven't tried mine either, but here is my solution:

 

 

Here is the thread on them: http://forums.hybridz.org/showthread.php?t=111435

 

Basically I took the stock tie rods, cut off the straight section before the bend and welded that into a circle track style swaged steel tie rod end. I had considered your solution, but I find that tapping a straight hole in a tube is pretty much impossible for me to do by hand. I guess most guys do that part on a lathe...

[MONZTER]

John,

Thanks,

Good solution cutting off the threads on the old tie rods and building them into the new ones. I really like all the interesting ways people find to do the same thing so many different ways on this forum. Great option for people without access to a lathe; where did you find the swaged tubes? I remember seeing them once somewhere, but could never find them again. What is the wall thickness and material spec for those tubes?

Thanks Jeff

[JMortensen]

The tubing is .072" thick. You can find the swaged tubes from Coleman Racing, AFCO, and any number of other circle track parts suppliers.

[ktm]

I had a local shop weld reinforcing gussets I had Baddogparts custom fabricate based on his original design. Instead of an angle plate, mine is more of a C-channel that slips over the top and bottom of the rail.

 

I had the shop cut open the rail and insert steel tubing before welding on the gusset. They then rosiette weldd the plate to the rail.