SidViscous

That's not a bad idea. Hadn't heard of strain measuring Lacquer though.

A digital micrometer (Which is really an encoder) Could come in handy as well. Wouldn't be hard to hack it up and install the readout in the dash.

That would be a heap-o-fun to do and fairly cheap.

hplj123

Hi all!

I am the designer of the KLA Industries strut brace and am very impressed with this thread. I would like to chime in with a couple thoughts. The issue we are trying to help with this brace is not new science. It has been a problem ever since the tire manufacturers introduced tires that had very good sticking qualities. The problem is that in a tight turn the forces on a front (and rear) tire are greater than on the outside tires. With the geometry of the front end being that the strut attachment point is well above the fulcrum, slight flex will induce several degrees of camber change in the outer front tire. The strut braces sole purpose is to transfer the load that the outer strut tower can not hold to the inner strut tower. This will accomplish two things. First is that both towers working together will eliminate the majority of the flex and second is that the strut brace will keep the relative camber of both tires in the same plane for both front tires.

This works much like the torsion bars do for body roll. The torsion bar ties the suspension (left to right) together so in a tight turn much of the stresses from the outside shock to strut is transferred to the inner suspension. In other words, all 4 shocks and struts are more evenly loaded in a sharp turn. The strut brace is doing the same thing. In our strut brace you should see between .002 and .004 of an inch total geometry change between the 2 towers. The only change will be the minimal movement you get in the joints. I am going to make an educated guess that without the brace you will see between 4-mm and 8-mm flex. This difference will totally depend on the adhesion that the tires provide and many other factors that will induce a bending moment into the strut tower.

I love the idea of a test but truly believe that somewhere on the Internet the data might already be out there. Anyway, please forward me the parameters that you use and the results. I would love to see your data. Rennlisters are truly the most innovative and forward thinking people on the net.

Ken Arnold

Thaddeus

We aren't designing a suspension here, we're trying to determine if the strut brace bolsters one dimension of the suspension geometry on the assumption that it should be a static measurement under load. So keep it simple! Take a regulation strut brace, fasten it but loosely on one side, paint the thing with machinist's scribing paint, and let 'er rip. If there's any movement at all, I'd call that too much.

And I still think the things are good for stabilizing an old chassis. These cars are nearly antiques.

My 2 cents. I'm very interested in any results that are forthcoming.

Thaddeus

hplj123

Me too!! Also, before everyone jumps on me for calling a sway bar by the wrong name (torsion bar) PLEASE EXCUSE ME. I'm from the old school where any bar that transfers load via. a torsional bending moment is called a torsion bar. For the record, I was talking about a sway bar.

Ken

944Fest (aka Dan P)

8mm?? Holy smokes!!!

hplj123

Dan,

Keep in mind that 8-mm is my high end guess using very sticky tires and driving very hard in a track situation.

Ken

hplj123

<img src="graemlins/offtopic.gif" border="0" alt="[offtopic]" />
By the way, do you have pics of the charger. I also have a 69 mustang with a 351 clevland and a 68 Comaro with a 327.

Ken

Danno

Remember that strain and stress are not the same thing.

Also would be interesting to measure displacement and rotation around each axis independently as well. Let's say you leave the bolts on the plates slightly loose on one side and you see that there was relative movement between the strut-tower tops.

1. Is this movement because the towers spread under cornering?

2. Or was it because one of them moved upwards when hitting a bump?

It would appear that if it was the second case and the strut-brace pulled on the other tower to keep their tops the same distance apart, you would be messing up alignment on two wheels instead of just one.

Now we're looking at a strain gauge along each axis....

SidViscous

Just for the record Danno. Strain and stress are different. Particualrly since you can't measure stress directly as it is a factor of the material. So you have to measure strain and then apply the material modulus to get the stress.

hplj123

I'm not sure that will tell us the whole picture. I desigen the attach plate to fit with close tolerences to the 4 studs and the center strut lip. I don't think it will show the total amount of twist.

As far as the verticaL movement is concerned, we took the shock loads on a very rough road into account. We used a bearing mount joint to allow any vertical movement to NTO be transfered across the bar. It is designed for compression and tension loads. It is there to keep the strut towers from flexing outward only.

I hope this helps.

Ken

hplj123

Wow, what about the spelling on that last post. My fingers have quit working so I'd better go to bed. I look forward to reading more in the morning.

Ken

944Fest (aka Dan P)

[quote]Originally posted by hplj123:
<strong> <img src="graemlins/offtopic.gif" border="0" alt="[offtopic]" />
By the way, do you have pics of the charger.

Ken</strong><hr></blockquote>

I hate to contaminte this great technical thread with OT muscle car blather, but a few pics of my Mopar can be found here:
<a href="http://home.earthlink.net/~squatch/" target="_blank">http://home.earthlink.net/~squatch/</a>
or
<a href="http://home.earthlink.net/~squatch/" target="_blank">Dan's first attempt at webpages</a>

(MAN, that page needs updated!!)

Bottom line, she's an extremely powerful dinosaur for reliving the good old days that weren't really that good, car-wise. My 4 cyl 2.5 litre runs circles around the "tank" and it's 7.2 litres. The only reasons I still have her are:
1.she cast a spell on me back in high school that I can't seem to shake
2. I've got 2x in recipts what it's worth
3. Man, it does a WILD burnout with 295s and posi

She deserves a web page of her own, bragging about the rare "white hat special" and other options, But I'd rather thumb thru Porsche mags than build a digital shrine to her. Someday, maybe.. I've been gathering parts for the resto.. With a 340 HP Turbo S and a Cooper S to compete with, she gathers a lot of dust.

I'm sure you know what I mean. It looks like you've got a couple of great bowtie/blue oval examples. The choice of Porsche or musclecar to drive is like choosing between Janet Reno and Jennifer Aniston.

Now I return you to your previously scheduled "On Topic" programming...

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

User 41221

A question for the greater minds on the boards... would it be worth making up a few samples of fasteners with known properties (stress, strain and torsional) that are softer than the STB components and measure stretch and twist? That would get you two-axis testing, right? It probably wouldn't be practical, but I was thinking that if you start with a very soft fastener to replace the heim joint, and increase the hardness of the fastener as you run tests ( I am thinking three tests total), you should be able to dial in a point where the resistance of the fastener yields a fairly accurate measure, right? The problem with this would be in duplicating the test repeatedly, but since you are looking for limits here, you should be able to extrapolate the result, given known constants of the fasteners. Or am I just getting too tired?

Buying a strain gauge is starting to sound cheap...

Regards, ...Scott

Matt

It seems to me that we can roughly calculate the cornering side force on the outer strut top - not very precisely, but it should give us a ballpark number for the amount of force the upper strut mount actually sees in steady-state cornering.

Use different numbers if you want, but for the sake of simplicity, let's say we have a 3,000lb car cornering at 1g. That means the tires are developing a total of 3,000lbs of side force.

Let's estimate that the front tires are doing 55% of the work, so that's 3,000lb x .55 = 1650lb of side force on the fronts. If the outside tire is doing 80% of the work in front, that's 1650 x .8 = 1320lb of side force being generated by the outside front tire.

I don't have the info handy to do the rest of the calculation, but I'm sure someone here does -

We need some measurements from a typical strut to get the ratio of [the distance beween the center of the ball joint and the center of the spindle] to [the distance between the center of the ball joint and the center of the top spherical strut mount] at actual ride height.

Once we have that ratio we can figure out how much of the 1320lb side force is taken by the control arm and how much is taken by the top mount.

The #s I used are open to debate, but the I think the concept is correct enough to give us a ballpark number to talk about.

Anyone know the strut measurements?

Matt

hplj123

I hate reading threads like this because I woke up last night thinking about it. Well this is what I came up with at 4:00 am so if is sounds stupid I’ll attribute it to the time of night. Why not take of one end of the bar and cover the tube with masking tape from the end to about 6” up the length. Then find a piece of tubing that will slide over the bar. Drill a hole in the tube to attach to the mounting hole in the bracket. Slide the tube over the bar and bolt the tube to the bracket. This will provide a slip joint between the bar and the tube. Finally drill a hole in the tube so the end of a sharpie can be inserted to mark on the tape. A little mount for the sharpie can be made with duct tape and when the towers flex the sharpie will mark on the tape. Drive the snot out of the car and the measure the mark. This will give both positive and negative movement and be cheep to produce