Section VIII Modified Rear Suspension Mountings

Warning:- Before carrying out any modifications to the standard design seek written approval from the Kit Designer. Use only high quality materials and fasteners and lock all threads. This applies particularly to Safety Critical items such as Brakes, Steering and Suspension Components.

Using the existing Sierra Rubber Suspension points is something of a compromise, as the rubber mounting on the differential is not used, and the rear of the differential is bolted directly to the chassis. Use of the Sierra rubber bushes does not give a positive location as they can be can be squashed depending on how tightly they are bolted up. There is however a second alignment required with the Chassis to Swinging arm pivot and a further 12mm bolt added by Robin Hood.

Ensuring positive location of these three mounting points has resulted in the design and manufacture of a set of Alloy bosses that fit into the tapered holes in the Rear sub-frame once the rubber bushes are removed.

Two smaller bushes are used to locate the added 12mm bolts. The use of a Socket head screw means that a much smaller hole needs to be drilled in the sub frame underside. See Appendix II Link to AutoCAD Drawings whilst the photographs below give a general idea of the finished units.

When using this set up be sure to put a gasket between the alloy/steel junctions and Grease or Waxoyl inside the sub frame. (Where the rubbers came out) An extraction tool made from a piece of 100mm dia tube will pull both rubbers out with ease.

Note the 3mm drain hole in the lower bush. The steel tube needs to be about 15/20 thou less in overall length than the total bolted up assembly, including the floor pan, chassis and gasket. The tube can be retained at the final assy with Loctite Retainer. 

Thickness of the top boss is critical to ensure the vertical flanges on the 2B chassis line up with the swinging arm pivot bolts. Carry out a trial assembly and machine the top face to suit. The result is a very solid rear end. See also the note at the end of the Chassis section regarding rear wheel location errors.

Designers Note. This modification has proved to be very sucessful and has completed over 1,000 miles without any trouble fitted to my own Robin Hood 2B.

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© Colin Usher 2005