Rack & Pinion Assembly
From the Lotus Seven - Master Parts List (1964) I have the following information:
This rack and pinion assembly of Standard/Triumph manufacture, is as fitted to the Triumph Herald with the two following modifications. Two lock limiting spacer tubes are fitted on to the rack to limit its movement, and 3/8" (9.5 mm) and 1/4" (6.4 mm) is cut from the mating ends of the tie rods and ball joint assemblies respectively to allow for toe-in adjustment.
The Herald/Spitfire tie rod is 8.715 inches (ball centre to thread end) but the thread cannot usually be altered because of the rolled threads. This mean the diameter where the Lotus needs the thread is already sized to about the thread minor diameter.
Tie rod ends
It is quoted that the rod ends from the Mini/Metro (GSJ734) has a slightly shorter thread (1/2"x20 UNF) than the Triumph part (GSJ158). So machining of rod ends might not be required if the later Mini part is used.
The joint between the steering column and the rack is known to fail. The rubber quality in the new remanufactured ones is even worse than the original parts. So I was looking for a replacement. Problem is, there is very limited space available - the coupling runs very close to the frame. I finally found one at Rally design, which shares the same splines (36 x 9/16") in each end. I later found out that Caterham is using a similar one in their newer models.
Item number (Rally Design): RD820 Steering coupling, Group 4
The joint is slightly longer than the original so it will move the steering wheel a bit (6 to 10 mm) closer to you - not a problem for me. Weight is approximately the same as the original: 0.250 Kg.
To ensure linearity of response it is recommended that the yoke of the universal joint is positioned with the cross vertical/horizontal when the steering wheel is in
the straight ahead position.
This very long steering column is only "anchored" at the ends with a bush in the frame just behind the steering wheel. This mean that the whole column can flex. To prevent this, some later models introduce an intermidiate bearing just in front of the pedals. Unfortunately this is designed for another column, where the "thicker" part extends longer. I had to design something myself, and came up with a solution used in MG's and others - a felt bush soaked in oil. This gives very good location with a minimum of friction.
to see a dimensional drawing.