In Detail: Sauber Rear Suspension Pull Rod Rocker

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As F1 shifted from push rod rear suspension to pull rod, the packaging of the various compliant elements pivoting on it became more complex too.  Here we can analyse in depth the lower section of a Sauber C30-C31 rear pull rod rocker from 2011-2012.  This part pivots in a subframe mounted inside the gearbox, to operate the side springs\dampers, heave spring\dampers and anti roll bar.

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The installation of the Sauber rear inboard pull rod suspension assembly has already been described on ScarbsTech.com.  Although different in some details, this rocker is from the same sort of installation.  Being some 175mm tall and weighing 640g, this is a substantial object, reflecting the loads the part needs to transfer.  Machined from a solid piece of material (believed to be Titanium) its form is based around a 41mm dia central hollow shaft with four bell cranks formed in two separate physical levers.  These bell cranks will mount the pull rod, side damper, anti roll bar link and heave spring\damper, while the side spring torsion bar mounts to splines inside the hollow shaft.

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To pivot the rocker in its subframe, there are two bearing surfaces top and bottom, each house a 40mm ID bearing, then threaded collars top (Dia 36 x 2.00 thread pitch) and bottom (Dia 39 x 1.00 thread pitch) to secure the rocker between the bearings and subframe.

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The splined connection for the torsion bar is in the bottom of the shaft section, with an internal circlip to prevent the torsion bar slipping out under gravity.

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Numbering the bell cranks from top to bottom, my judgement of the mounting arrangement is as follows; 1) Heave spring\Damper, 2) Pull Rod, 3) Side Damper 4) Anti Roll Bar.

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The lever arm formed for the first (heave spring\damper) bell crank is separate to the others and is more substantial as a result, it houses an M8 fastener to pivot on the bearings on the clevis mounted to the end of the heave spring\damper.  It is radially spaced nearly in line with the second bell crank

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Bell cranks 2, 3 and 4 are formed on the same lever. The second (pull rod) lever arm being radially spaced well away from the third and fourth bell cranks and needing a M8 fastener, this fits through a bush inside the arm and requires a separate nut to secure the fastener.

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The other two only require a smaller M6 fastener by having threads formed inside bosses on the lower flange.  This area also incorporates a small pin mounting for a LVDT sensor for measuring rocker movement.

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The lever arms formed from the shaft centerline are as follows 1) 62mm, 2) 56mm, 3) 87mm, 4) 86m and are radially spaced from the first bell crank by 2) 11 degrees 3) 95 degrees 4) 125 degrees.

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