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Re: trust a torsion bar?
[Re: Supercuda]
#565471
12/30/09 01:48 AM
12/30/09 01:48 AM
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Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
1_WILD_RT
Management Trainee
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Management Trainee
Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
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Quote:
parallel to the bar is usually ok, perpendicular is what's bad. If you smooth and dress the nick, and it's not deep, it's usually ok.
However, if you can afford it, replacement is probably teh best bet.
Just think about where the T bar lives and all the road juck that's hit all the T bars over the years. How many have actually failed? Probably not many, I've had the adjuster bolts rip out, but never a T bar fail. FWIW.
Actually a thread came up a couple years ago about a torsion bar that had broken & about a dozen members had experianced failures.. FWIW one broke on my dads Chrysler back in 69 while it was sitting in the driveway...
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Re: trust a torsion bar?
[Re: Supercuda]
#565472
12/30/09 08:55 AM
12/30/09 08:55 AM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
parallel to the bar is usually ok, perpendicular is what's bad. If you smooth and dress the nick, and it's not deep, it's usually ok.
However, if you can afford it, replacement is probably teh best bet.
Just think about where the T bar lives and all the road juck that's hit all the T bars over the years. How many have actually failed? Probably not many, I've had the adjuster bolts rip out, but never a T bar fail. FWIW.
if it's not too deep and you sand the blemish smooth to eliminate the stress concentrator, you'll most likely be fine.
a torsion bar's peak stress is at the surface, so a surface blemish like a gouge will be the failure point.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: trust a torsion bar?
[Re: GTXKen]
#565474
12/30/09 11:07 AM
12/30/09 11:07 AM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
I have to say that the idea of sanding and painting the nicked torsion bar as a repair makes no sense at all. I can't see how simply removing the raised area and masking it is hoing to help. Sanding down the high point will not improve the strength of the bar. If the nick removed material what is sanding going to do?
it removes the stress riser. localized stress in a corner will be higher, to mathmatically infinite as the corner radius decreases to 0. the most graphic illustration I could find in a 2 minute search of the intertubes is page 7 of this:
http://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2004.pdf
note how as the notch gets smoother and more gradual to the underlying material, the stress distribution becomes less concentrated, and the peak stress goes from 16 to 7.
granted, this is an axial pull, torsion is a slightly different beast, but the results are similar, as if you look at a local spot on a torsion bar, the stresses and loading is pretty much an axial pull.
now, the slightly smaller cross section in that area will very slightly reduce the effective spring rate and maximum load carry capacity of the t-bar....
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: trust a torsion bar?
[Re: patrick]
#565475
12/30/09 11:41 AM
12/30/09 11:41 AM
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Joined: Apr 2003
Posts: 3,968
North Riverside IL & Lowell IN
GTXKen
super gas
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super gas
Joined: Apr 2003
Posts: 3,968
North Riverside IL & Lowell IN
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Quote:
Quote:
I have to say that the idea of sanding and painting the nicked torsion bar as a repair makes no sense at all. I can't see how simply removing the raised area and masking it is hoing to help. Sanding down the high point will not improve the strength of the bar. If the nick removed material what is sanding going to do?
it removes the stress riser. localized stress in a corner will be higher, to mathmatically infinite as the corner radius decreases to 0. the most graphic illustration I could find in a 2 minute search of the intertubes is page 7 of this:
http://www.utm.edu/departments/engin/lemaster/Machine%20Design/Lecture%2004.pdf
note how as the notch gets smoother and more gradual to the underlying material, the stress distribution becomes less concentrated, and the peak stress goes from 16 to 7.
granted, this is an axial pull, torsion is a slightly different beast, but the results are similar, as if you look at a local spot on a torsion bar, the stresses and loading is pretty much an axial pull.
now, the slightly smaller cross section in that area will very slightly reduce the effective spring rate and maximum load carry capacity of the t-bar....
Thanks Patrick, your explanation along with the illustration makes it much clearer. The painting is cosmetic but removing the burr reduces the stress. I'll take a look at my bar and reassess its condition.
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Re: trust a torsion bar?
[Re: GTXKen]
#565476
12/30/09 12:10 PM
12/30/09 12:10 PM
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Joined: Oct 2006
Posts: 7,371
Iowa
burdar
Owen's Dad
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Owen's Dad
Joined: Oct 2006
Posts: 7,371
Iowa
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Quote:
FWIW one broke on my dads Chrysler back in 69 while it was sitting in the driveway.
Probably 10 years ago now, when I was working as a mechanic, a newer Ford F-150 came in with one side sagging. It was in the middle of winter so we thought a shock had frozen or something.
We put it on the lift and sure enough, one of the bars had broken. We left it inside over night and when we went to drive it out the next morning, we realized that the whole front end was sagging. We raised it back up and the other bar had broken overnight.
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