[Chrysler300] Statics 101
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[Chrysler300] Statics 101





Angular deflection of a torsion bar is pretty easy to visualize.  A thicker bar or stronger steel will produce less deflection for the same load.  It may surprise some to know that a coil spring acts pretty much like a torsion bar wrapped into a coil.  Torsion bars offer easier fabrication, easier adjustment of ride height and some advantages in packaging.  Otherwise, there’s not much difference.

 

The comments about corrosion problems reminded me that a torsion bar in my ’61 Valiant broke as I was backing out of a parking place—a couple of years after purchasing it new.  The black tar-like protective coating on the bar had been chipped—probably from kicked-up road trash.  Omaha salt did a job on the exposed steel and I got a beautiful classic fatigue failure.  That brought the reality to my courses in strength of materials and statics.  With the Valiant, I was able to remove the broken ends and motor on in to the dealer for a free replacement.  It’s possible that torsion bars may be more exposed to damage than coil springs that are somewhat hidden.  I don’t recall coil springs being coated except by overspray from rustproofing the bottom of the car.

 

Long torsion bar life depends on its metallurgy, original surface finish, coating and protection from road trash damage.  Therefore, it would be a good idea for most of our ’57 to date 300’s (I think the 300M’s had struts) to inspect the torsion bars’ coating for continuity.  Holes in coating are called “holidays” in pipelinese and should be cleaned and the underlying steel carefully inspected for corrosion pits or physical damage like a nick.  These can greatly concentrate stress at that point and lead to premature and unannounced failure.  Tolerance for this kind of damage is zero.

 

Rich Barber

Brentwood, CA (Saw 103 F here a little earlier today but a warming trend is predicted)

 

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of EMills_ATC millserat@xxxxxxxxxxxxx [Chrysler300]
Sent: Tuesday, June 21, 2016 8:53 AM
To: Rich Barber <c300@xxxxxxx>; 'Bob Merritt' <bob@xxxxxxxxxxxxx>; 'John Grady' <jkg@xxxxxxxxxxxxxxxxx>; charlies@xxxxxxxxxxxx; Chrysler300@xxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] Strut / Torsion bars

 

 

OK - so Torsional stiffness Torque/Rotation = KG/L where K = Pi/2 x (Radius)4 ---- (Thats radius to 4th power or squared twice - cant seem to make superscripts work) and G is a constant for steel and Rotation is in radians.

But all you want to know is difference in stiffness, so take G as a constant and just look at difference in R4th/L

And since L is constant here at 40 in, difference in stiffness is simply (.505)4 / (.495)4 or 1.08329 - translated 8.3% difference in stiffness between 300 Sport (or Newport Sedan / Conv, etc.) at 0.99 and H at 1.01

H vs New Yorker 12.8% stiffer

H vs Newport wagon 17.5% stiffer

And by the way, to convert to stiffness you need distance from center of rod to centerline of tire - if you want absolutes, need to go thru more calcs incl dealing with G Shear Modulus and radians.

But unless you are playing with different wheel offsets (going to aftermarket wheels - moving out increases moment arm and increases torsion which effectively "softens" car spring rate - moving in effectively "stiffens" but you get interference) or changing hub dimensions (such as may be if changing to disc brakes, etc).

PS - If you are also playing with Anti-sway bars on front only, it would not be unusual to soften spring rate if increasing sway bar stiffness on that end - otherwise you would need to play with back of car to keep handling balance (oversteer / understeer).

For example, if you add a rear sway bar to a car that did not originally have one, and you do nothing else (no change to rear spring rate or better front bar increase in stiffness to balance handling), be prepared for rear end to come around fast in a hard turn - potentially severe oversteer condition. (Personal experience, lesson learned)

 

Edward Mills Antique Tractors 1930-1960 Antique Cars 1960-1985

On 6/20/2016 1:45 PM, 'Rich Barber' c300@xxxxxxx [Chrysler300] wrote:

 

HD suspension may have been an option on all ’62 Chryslers and included the thicker torsion bars which were standard on the H.

 

Rich Barber

Brentwood, CA

 

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of 'Bob Merritt' bob@xxxxxxxxxxxxx [Chrysler300]
Sent: Monday, June 20, 2016 11:24 AM
To: John Grady <jkg@xxxxxxxxxxxxxxxxx>; charlies@xxxxxxxxxxxx; Chrysler300@xxxxxxxxxxxxxxx
Subject: Re[2]: [Chrysler300] Strut / Torsion bars

 

 

AMA specs for 1962.

 

Newport Sedan, hardtop, convertible: torsion bar 40.0" x .99" diameter

 

Newport station wagon: torsion bar 40.0" x .97" diameter

 

Sport 300: torsion bar 40.0" x .99" diameter

 

300H: torsion bar 40.0" x 1.01" diameter

 

New Yorker: torsion bar 40.0" x .98" diameter

 

 

 

 

------ Original Message ------

From: "'John Grady' jkg@xxxxxxxxxxxxxxxxx [Chrysler300]" <Chrysler300-noreply@xxxxxxxxxxxxxxx>

Sent: 6/20/2016 1:12:32 PM

Subject: RE: [Chrysler300] Strut / Torsion bars

 

 

To my knowledge the strut rods do not flex or bend or twist at all, they just move a bit in the rubber, to allow the suspension to move up and down , while locating suspension  arm / spindle fore and aft. so that thickness is a non issue. (axial loads only); rubber durometer might change that fore and aft stiffness but not much and only of value for that kind of (rare) loads? —in case you hit a very deep pothole.  ; I do not understand the torsion bars at all. It should be the other way around., stock ? The 300 should be thicker, as  that is (factory) stiffer ; maybe 300 were swapped to smaller in the past? Any chance those numbers are inverted? Or 300 sport was really a very soft car compared to 300H ; which may be true. Interesting info, that is for sure.

 

But I do not know the factory 300H specs. Others will…

 

Why would a Newport be sprung stiffer than a sport?

 

 

See listings of aftermarket / MOPAR performance torsion bars for B and E bodies, as a rough reference? Thicker bars = stiffer suspension , mostly, usually related to holding up heavier engines too. . Might or might not like that impact on ride . ( I like stiffer) but------Not like it is a  race car, screaming around corners on a  NASCAR track? IMHO

 

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of charlies@xxxxxxxxxxxx [Chrysler300]
Sent: Monday, June 20, 2016 9:55 AM
To: Chrysler300@xxxxxxxxxxxxxxx
Subject: [Chrysler300] Strut / Torsion bars

 






Hi Group,

Last year I installed a factory sway bar on my 62 Sport. In discussion with Dave Dumais at the MaCunngie meet, he said that it was likely that the strut rods on the doner (Newport) car were likely larger dia. Upon inspection, I found that this was indeed true. My current strut rods measure approx. .015 smaller than the Newport.

Also, a measurement of the torsion bars also reveals a difference. My Sport measures approx. 970 dia. and the Newport at approx 1.010 dia. 

So the question is - Would it be worthwhile to swap out these parts to my Sport. I guess I'm wondering what difference, if any, would I notice in ride quality / handling. 

Thanks, Charlie in Ottawa

 

 






 



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Posted by: "Rich Barber" <c300@xxxxxxx>


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