THSCC Forums

They are. Speedway engineering for most, with some McMaster-Carr stuff thrown in. I think the better plan is over-the-rack for the arms, rather than under. Seems like to me some are opting to use aluminum for the arms, but that seems like it would make rate calculations difficult given the introduction of two metals with two different modulus numbers.

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

I would use aluminum in a heartbeat, and based on the construction, I would not attempt to account for any differences between aluminum and steel. But that's just me, and I would get all googly eyed over the weight savings.

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In need of car.

Shouldn't matter. Arms aren't twisted.

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2011/2012 Autox VP
2013/2014.5 President
2013 Top Gun

2015 Fit

22R-EC => 4G63 => D16Y7 + D16Y8 => EJ255 + K24Z2 => K20Z3 + K24Z2 => K24Z2 + M54 => L15B

there is a torque at the splines between the torsion arm and center section, yes? That could impact the "spring rate" of the bar given the two different metals? Additionally, over time is there not a risk of metal fatigue at the splines and possible failure? If it's not a big deal, and the Al arm is lighter than the steel arm, then why isn't everyone using Al arms and a steel center section?

<---not an engineer, forgive the ignorance.

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

Cost.

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In need of car.

No torsion on the arms.

_________________
2011/2012 Autox VP
2013/2014.5 President
2013 Top Gun

2015 Fit

22R-EC => 4G63 => D16Y7 + D16Y8 => EJ255 + K24Z2 => K20Z3 + K24Z2 => K24Z2 + M54 => L15B

Yes, there is significant torque applied to the splines, but that torque is transferred directly to the center section via the splined connection, so the result is insignificant impact on spring rate. (The applied torsion twists via the path of least resistance, which, in the case of a swaybar, is the center section due to its comparatively small diameter in the direction the torque is applied.) And if the splines were weak enough to deform due to the torque applied to that connection, the connection would self destruct as gaps would form in the splined connection itself.


Yes, since that connection sees a boatload of twisting force when the bar is fully loaded, the risk of failure is significant. The trick is to design the parts to withstand that loading. For instance, a thinner aluminum arm and/or smaller spline height connection would result in increased risk of failure due to permanent deformation at the splined connection.


As Jason mentioned, it's likely due to cost difference for the aluminum vs. steel arms, but it also may be due to concerns about the strength of the aluminum arm at the splined connection. Aluminum is significantly softer than steel and, therefore, signfiicantly easier to bend/deform. Unless/until the aluminum parts prove themselves to be up to the task, I'd be concerned about spline failure with those (aluminum) parts.


not a doctor (but I play one on TV).

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Keith Q.
2008 Top Gun
http://www.youtube.com/watch?v=KmX8XuZ_DCo&NR=1

Thanks, Keith. Given how people in STR spend $1000 on an exhaust for weight savings, and will spend over $1000 on brakes to save 16 lbs, as well as spending close to $1000 for a front bar+bearing mount setup (Small Fortune Racing), I suspect aluminum is not chosen more for failure/fatigue than cost.

I appreciate your explanation!

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

Bill Schenker uses blade style bars on his CSP car. I'm assuming for the weight reduction.

http://miataroadster.net/sponsorees/bil ... grms2.html


And to totally blow your mind here is a setup that rotates the blade to provide cockpit adjustable sway bar stiffness.

http://forums.pelicanparts.com/porsche- ... -bars.html

The first thing I thought of when I saw the design used an arm attached via spline drive were bicycle cranks, which obviously don't see nearly as much force, unless you're really a badass!



Here's an article about the Nascar style setup and why it might be beneficial. http://www.circletrack.com/howto/ctrp_0 ... index.html

Aren't the upper arms aluminum and the lower ones are steel for this exact reason?

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Club Webmaster
-2014 Mazda 6 SkyActiv DD
-2002 Honda S2000 totaled by deer

Whoa... I think we've met our match!

that's a lot of Silverstone!

BTW, I hear that the Ankeny guy is in development of a blade-adjustable rear bar, priced below the Gendron stuff. Might be worth a look when/if it comes out.

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

Paging Ram Vennam to the white courtesy phone.....

http://raleigh.craigslist.org/cto/2964434822.html

9k AP1. High miles, a few mods

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

That looks like it would be a good autocross car for nine grand. I think this is the first legitimate Craig's List 'willing to trade for..' I've read:
"I'm willing to trade 06+Civic SI and Acura TSX Must be same value." Either of these two earlier year models would be about the price with similar mileage.

I swear sometimes these were made in a 2 to 1 ratio for color production. Silverstone two, everything else one.