Need some advice on on steel vs. aluminum swaybar links/arms.

Last time out at VIR the RF bar link broke and sidelined the car for the weekend. After doing some research I found that this is NASCAR tech on our cars and bar links could be had in aluminum and steel versions. I had Panoz get 2 in steel for me, but wasn't expecting them to be so much heavier than the aluminum. The shipping weight says 11lbs... they're easily 5lbs+ a piece, they feel like a dumbell! The aluminum one feels like a feather in comparison. Unfortunately I have no way of weighing them at my house.

Broken one...
http://img.photobucket.com/albums/v627/cobra4b/Panoz%20GTRA/DSCF2346.jpg
http://img.photobucket.com/albums/v627/cobra4b/Panoz%20GTRA/DSCF2348.jpg

New steel set...
http://img.photobucket.com/albums/v627/cobra4b/Panoz%20GTRA/DSCF2426.jpg

I'm a bit hesitant to install them and am considering getting a fresh set of aluminum ones from Panoz, but I hate to flush $200 down the drain.

My knowledge of race car physics is limited to what I've learned from 5+ years at the track and reading "how to make your car handle". Seems to me that the bar link is partially sprung and unsprung weight. Making it heavier will reduce the speed with with the suspension can move up/down but to what degree?

Lets assume the steel bar link ways 5lbs and the aluminum ones are 1.5lbs each. With that assumption how will this affect the car's performance? What do you all think?

A buddy of mine as a degree in motorsports engineering and works for Motec... he posted this on our local car forum:

Wow. I'm not sure how much room you have to work with, but if you have enough to beef up the area surrounding those clamp joints than you could make another aluminum set. The weight of the steel arms won't affect much dynamically depending on where they attach to the suspension. It's unsprung weight, which is your enemy, but how much weight will depend on how far out they are (the closer to the pivot the less moment the weight has around that pivot) and what the rotational inertia of the arm is versus the anti-roll stiffness. It's going to be a lot more than the aluminum, that's for sure. You can't rotate a heavy steel arm anywhere near as fast as an aluminum one, for the same reason that lower unsprung weight (wheels especially) reacts faster. Basically the steel one will be worse in terms of sprung weight and unsprung weight (it's a combination of both because of the mounting) and worse in terms of dynamic response.

That being said, there are a few things to think about. First, you could remove a LOT of weight from those steel arms and still have them be plenty strong. The area around the pinch joint is the weakest part, so you can turn the rest of them into practically nothing without any penalty. The other thing to think about is getting a set of tubular links make instead of solid steel. That's a very common thing to do; the pinch joint looks like the stem on a bicycle (that clamps the handlebar) and that is welded to a sizable piece of rectangular tube. Then the end link is just a piece of flat stock with holes in it just like the steel arms you have, or just some inserts welded into the tubing (for crush resistance when bolted). Some of them just slot the tubing and put a small spacer on either side of the heim joint (on the drop link) with a bolt through it (imagine a box-tube version of the billet piece in the picture below). I have a beautiful picture in my mind of what a fabbed set of curved arms would look like. It's really too bad that you need a specific broach to cut the splines, because the rest of the fab work is nothing special, it's just time consuming (with some machining, welding, and maybe some waterjet work too).

Anyway, it's very strong and pretty light. I'll see if I can find a picture if I get a chance.

By the way, is the bar straight or formed (kinked, humped, etc)? Oh, and how long are the drop links that attach to the ends of the arms? Any idea if those aluminum arms are heat treated or anything like that?

Ok, this isn't what I was looking for, but it's still a representation of making the arms fairly minimalist. I still can't find a pic of the tubular style.. They look like a long rectangular section mountain bike stem with internal splines in the pinch joint though.


So what's the fellow Panoz owner's $0.02... get another aluminum one from Panoz and keep these as spares, or get a fresh set of aluminum ones and chalk it up to experimentation?

Brian,

I view this hobby as cost=fun,how much are you willing to spend to have fun. I would say make the car reliable so you can have fun. When you are at the track broken you are not having fun. HPDE pays zero money but it pays alot of fun.

David

Brian,

I view this hobby as cost=fun,how much are you willing to spend to have fun. I would say make the car reliable so you can have fun. When you are at the track broken you are not having fun. HPDE pays zero money but it pays alot of fun.

David
Yeah I agree... but we spend a good bit of dough to take weight off here/there in these cars and I hate to needlessly add weight and reduce front suspension performance.

Just looking for more input... replacement aluminum arms aren't expensive either.

i would say if you're concerned about reducing front suspension performance, keep the steel ones. Adding a heavier swaybar end link is not going to affect performance enough for you to notice, look at any good performance swaybar, they typically take a thin, spindly, hollow stock swaybar and replace it with a solid, MUCH thicker, in most cases, swaybars and certainly increases the overall weight. and you gain much more performance than you might lose.

however if it were me, I would have just replaced them with aluminum, I could just as easily skip lunch and save a few pounds to make up for the weight difference, but wheres the fun in that? But now that you have the steel ones, go with it.

I will almost guarentee you wont notice a performance difference either way, so it's more a personal preference. You have the steel ones, put them on, and know you won't have to worry about them. Sometimes the car that wins a race is the ones thats most reliable and not the fastest!


and I think what your friend was talking about is a great idea, Drill a few large holes in the center of the arm and shave off a pound or two, just don't drill within 2" of the bend, or the connection points.

IHMO



besides with that sweet new motor we need to slow you down a little ayway ;-)

I would agree with the idea of simply drilling out the steel ones. The high fatigue areas (the ends and bend) will be more forgiving than the aluminum ones and holes will make them look cool! You can drill out 1/3 the width and have no appreciable difference in the bending stiffness. The steel will be much more resistant to fatigue. And, from the looks of the arms, it appears they are the same dimensions as the Aluminim versions. If that is the case, the steel version will be about three times stiffer, so that isn't an issue. Keep the steel....

Thanks for the input guys... are you saying drill all the way through or drill recesses to remove material?

Not sure how I could drill anywhere and not be within 2" of the end holes or th bend... anyone want to get createive with MS paint and show me were i can reduce mass a bit?

Thanks for the input guys... are you saying drill all the way through or drill recesses to remove material?

Not sure how I could drill anywhere and not be within 2" of the end holes or th bend... anyone want to get createive with MS paint and show me were i can reduce mass a bit?


Post the dimensions and i'll try to knock out a quick cad drawing and export it as a jpg.


Width, length, and distance to the bend.

I would do something like this, it should not affect the structural integrity of the piece any, you could also take an angle grinder and round the corners on the length wise top and bottom sections to remove a little more material.

http://www.extremespeedonline.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=96358&g2_serialNumber=1

I would do something like this, it should not affect the structural integrity of the piece any, you could also take an angle grinder and round the corners on the length wise top and bottom sections to remove a little more material.

http://www.extremespeedonline.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=96358&g2_serialNumber=1


ok looking up at your pics above its not totally accurate, but hopefully you get the idea.:banghead:

Ok, maybe a better example... something like this, and then round the top and bottom edges.....

http://www.extremespeedonline.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=96361&g2_serialNumber=1

and then round or bevel the edges between the vertical lines below...


http://www.extremespeedonline.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=96363&g2_serialNumber=1

You could also take them to a machine shop and have the thickness milled down.

I'm confident you will never be able to tell the difference though.

Thanks for all the input guys... I appreciate it :)