Torsion bars shields do what exactly?

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Jeremy
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#1 Torsion bars shields do what exactly?

Post by Jeremy » Sat Oct 27, 2018 4:21 pm

I have far too much respect for the Jag designers to suggest that these pieces of hardware serve no purpose other than provide a source of rattles, simply that I can't work out what they're for. Is it really just to keep mud off the torsion bars, and if so why is that so important? Angus has an interesting theory that they may be an early attempt to improve airflow and reduce turbulence under the car - although I'd have thought they would have a different name if that were so.
Any thoughts? I'm probably missing something very obvious.
Jeremy
1967 S1 4.2 FHC

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abowie
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#2 Re: Torsion bars shields do what exactly?

Post by abowie » Sat Oct 27, 2018 9:05 pm

Rattle and collect oil and mud.
Andrew.
881824, 1E21538. 889457..oops
http://www.projectetype.com/index.php/the-blog.html
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PeterCrespin
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#3 Re: Torsion bars shields do what exactly?

Post by PeterCrespin » Sun Oct 28, 2018 12:07 am

In terms of metallurgy and mechanical force distribution, the outermost 'skin' of a torsion bar is very important. In a related phenomenon, a small change in diameter - often not obvious to the naked eye - can have a significant effect on spring rate. For these reasons the surface of TB is more important than for a static bar or tube. Therefore it might make sense, even just theoretically, to try and protect the surface from nicks and scrapes due to stones or debris thrown up by the front wheels. There should be a strip of rubberized canvass between the shield and the frame rail to prevent rattles even if the brackets get loose

I think Angus is referencing the outcome of previous debates on the subject and airflow management was definitely in their mind. They weren't present for the early cars I believe.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 79 S2 XJ12L; 97 XJ6L

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1954Etype
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#4 Re: Torsion bars shields do what exactly?

Post by 1954Etype » Sun Oct 28, 2018 8:49 am

If protecting them was the objective Pete, there are much simpler ways of achieving it? I cannot believe they fitted such an expensive, hard to fit item just to protect the torsion bars.
Angus 65 OTS 1E11497. 67 FHC 1E33656

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PeterCrespin
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#5 Re: Torsion bars shields do what exactly?

Post by PeterCrespin » Mon Oct 29, 2018 2:43 am

Join the club Angus, it does seem an odd part and they routinely get mashed during jacking, same as the bonnet support frame. Trouble is, every time we rule out an option we increase the pressure to explain the true rationale. They clearly do SOMETHING to justify their existence, so if not A, B or C, what else is there? What do the Service Bulletins say? Were they present on 3.8s or early 4.2s? I know they're shown in J30 (2+2 parts book) with the left side in two pieces IIRC. Air management along the sides of the engine and under the car would have to be a strong possibility.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 79 S2 XJ12L; 97 XJ6L

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Hugo
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#6 Re: Torsion bars shields do what exactly?

Post by Hugo » Mon Oct 29, 2018 1:30 pm

Bristols have a rubber shield in front of the hole in the chassis where the rear torsion bars pass through - it's to stop stones getting trapped which might rub against the torsion bar.
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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Dawnpatrol
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#7 Re: Torsion bars shields do what exactly?

Post by Dawnpatrol » Tue Oct 30, 2018 10:33 pm

They had them fitted on March 65 build cars.
Battered but still attached👍.
Michael
1961 OTS LWE, 1965 OTS, 1966 FHC.

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