[Chrysler300] Torsion bars-Deja vu, all over again

In mid-1961, I bought a new Plymouth V-200 Valiant 2DHT. A pretty red car with just a taste of Chrysler 300 styling. In early 1963, while backing out of a parking place with a little curb bump, one of the torsion bars experienced its one-millionth cycle and snapped. As a freshly-graduated mechanical engineer, I had been taught some basics about stress risers, torsional stress and corrosion, and as a shade-tree mechanic I was familiar with my suspension, I reached under the car, pulled out one (or both?) ends and proceeded to drive the car for the weekend until I could get it into the dealer for replacement. The RH side was down on its rubber bumper, but the car was drivable with no rubbing. Almost as if by design. Thank you, Burt. I investigated the failure and observed it had begun at a place where the black coating had been nicked, probably by road trash, and a small corrosion pit started. By then, the car had been driven in two Omaha winters with plenty of road salt. The presence of the defect/pit really concentrated the stress to a point above the fatigue limit. The failure surfaces displayed the typical conchoidal surfaces of a fatigue failure and were somewhat spiraled. A classic failure. The bar was replaced on warranty and I had no more problems with the car. I’ve not heard of many torsion bar or spring failures but do see that the torsion bars are move vulnerable to road trash and corrosion damage—as compared to coil springs that are somewhat protected. The ends of the torsion bars are smoothly increased in diameter before the splined and hexed ends to reduce the stress in those areas. Inspection of the torsion bars when on a rack would be prudent. Damage to coating should be addressed by removing the coating in the area of the damage, crocus-cloth smoothing of any shallow pits and recoating with a flexible material.

Otherwise, see you on the guard rail when that one-millionth cycle rolls over.

Rich Barber

Brentwood, CA

From: Chrysler300@xxxxxxxxxxxxxxx <Chrysler300@xxxxxxxxxxxxxxx> On Behalf Of Ronald Kurtz mark6268@xxxxxxxxxxxxxx [Chrysler300]
Sent: Friday, August 17, 2018 7:48 AM
To: Chrysler300@xxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] Burt’s Comments/ 57 Torsion bars

Hi, John:

My E has boots on the bar that fit into grooves on the torsion bar anchors. No boot at the lower control arm. The bars on my E were slightly rusted and the bar on the passenger's side lower control was rusted fast. I took the lower control arm with the torsion bar "frozen" inside, hung the lower control arm over the side of the bench, wrapped the bar at the other end with cloth, attached a pipe wrench to the bar where it began to flair and hammered the wrench until the bar was free.

Also, there is no flexible coating on the bars as there is on my '64. I used Eastwood's rubberized paint on the bars to handle the twisting of the bar while driving. I will use lots of grease on the bar ends when installing (as recommended in the '64 shop manual).

Best,
Ron Kurtz
E #292

--------------------------------------------
On Fri, 8/17/18, John Grady jkg@xxxxxxxxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Subject: [Chrysler300] Burt’s Comments/ 57 Torsion bars
To: "chrysler300@xxxxxxxxxxxxxxx" <chrysler300@xxxxxxxxxxxxxxx>
Date: Friday, August 17, 2018, 8:58 AM

One of the things Burt spoke of at Keith’s home,
was the suddenly discovered stress corrosion of 57 torsion
bars at the end sockets . I know of this first hand , as
going around a rotary ( Massachusetts bad idea) at very high
speed as a passenger “ up on two wheels type thing “ in
1960 , in a 57 plymouth the highly loaded one snapped ,
putting 4 of us into guardrail .. Totalled the car . Had same
thing happen to me in a 51 ford at same place , ( steering
box tabs broke off box at frame bolts in those ) — maybe
it was just me at 17. Or debugging designs!

Burt described packing them with heavy grease when they
found this out ( a line of corrosion encircles the bar at
the mouth of the hex socket , due to salt rust etc . ) That
raises stress , like a notch leading to failure . Being a
spring in essence , the steel skin is highly stressed
there.

I loved how he calmly described this . Failure in
engineering in new designs happens , somewhat normal , life
testing 3x expected use is the only way to find obscure
things — but spraying it with salt probably not part of it
, that year. Bet it is now. We forget that “ torsion aire
“ ride was a major suspension and engineering innovation ,
a part of the 57 cars .. lots of new parts never used before
.

I am working on a 57 dodge , and I know later years ?58 59
May have rubber boots for this , 60 does . Is it at both
ends of bar ? When did boots start ? Do they fit 57 ?
Because I never saw a failed one , seeking info on this .
Bad surprise awaits if not addressed , and the older the car
more likely to happen . Pack with heavy grease at least .
Bar interchange ??

When it snaps wheel goes way up into fender hits upper stop
, iF in a curve at high speed can lose control .

Good thing to bang around , prompted by the meeting with
Burt .

Thank you Burt !

Sent from my iPhone

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

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