Right Hand Bracket                                                             Left Hand Bracket

Notes:

1. The shaped cutout on the LH bracket is the way Lotus manufactured the chassis and is done to ease the LH rubber mounting unit.

2. These designs are copies of the original Lotus pattern

3. The hole sixes and dimension assume that you are using the Lotus Gearbox mounting plate.

4. Each "U" shaped bracket is made by folding sheet steel and welding it into place on the chassis as shown below;

Note that the best way of lining up the brackets for welding is to install the engine and gearbox with all mountings, and then tack the brackets into place.

The bottom of the brackets should line up with the bottom of the vertical side plates of the chassis as shown;

 

Removing the original S1 mounting flange:

The S1 gearbox mounting is a large plate welded across the throat of the chassis, with a rectangular hole in the middle, as shown by the dotted lines.

The bracket is cut down as per the grey shape so that it would be easy to revert to the fitting of the original Lotus gearbox by bolting a new plate across the flange left behind. The other advantage of leaving this flange is that it is a good piece of strengthening across the chassis frame.

 

Upper Chassis re-shaping:

The upper chassis rails which form the "Y" fork are of a square cross-section on the S1 chassis. At the beginning of the "Y" fork these should be cut back for approximately 8 inches and a plate welded over the gap such that the square section becomes triangular in section. This becomes quite an awkward shape, but my chassis was modified by Spyder, who did an excellent job. The modern galvanised replacement chassis accommodates both S1 and S2 gearboxes, and so is already cut back. This photograph shows the changes;

Note the S1 gearbox mounting flange with fixing nuts, and forward of this the S2 flanges as described above. You can also see that the top rails are triangulated for the whole length of their run. As far as I know there are no other changes to the S1 vs S2 chassis.

 

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