russ.turner@...
Date: Thu Nov 2, 2006 7:55 pm
Subject: TCS Steering Rack Overhaual (PRELIMINARY)
I have just completed the overhaul of the steering rack from my 1974
TCS. I used the knowledgebase and the manual, but some information
was missing, some was wrong, and some was hard to find. I thought it
would help the next re-builder if the key information were summarized,
so I present my findings below. I may be in error on some items. If
so, please correct me (like I need to ask!) and I will post a final
version with those edits.
First I'll recap the background information from the knowledgebase:
The Europa steering rack is from the Triumph Spitfire. All of the
internal components are the same as the Spitfire and most of the parts
needed for maintenance/overhaul are available from the usual Lotus
suppliers and from Triumph suppliers. There are also new Spitfire
units available ($200 at the time of this writing).
There were two Lotus versions of this steering unit. The earlier
units had "modified tie-rod adapters" added to the ends of the tie
rods to accommodate the Europa track. These adapters are shown in
Figure 8, Section H of the manual. The later units, which I am going
to cover here, had lengthened Sleeve Nuts instead of the adapters.
The manual only describes the earlier unit and there is no update in
the Twin Cam addendum.
To make a later unit from a Spitfire unit you need four changes:
(1) A steering unit housing extender. This is a three-inch metal
tube that attaches to the passenger end of the steering unit housing,
to extend it. It attaches with a press fit of the end that has
bilateral splits and is retained with a hose clamp. I think the
extender's only purpose is to provide a place to clamp the standard
Spitfire boot, which otherwise would be too short.
(2) A tubular spacer. This is a three-inch metal sleeve, about 1/4"
thick, with an inside diameter that makes it a tight fit to the
steering rack and an outside diameter that prevents it from entering
the main housing, but allows it to clear the housing extension. It is
slipped over the passenger end of the rack. Its purpose is to limit
steering lock for left turns.
(3) Two extended Sleeve Nuts. On the early Europa and Spitfire units
the Sleeve Nuts are less than one inch long. These later Sleeve Nuts
are 2 inches long. The design of the Sleeve Nut recess is also
different, which causes change number 4.
(4) The tension spring is retained inside the Sleeve Nuts. It does
not poke through to the rack end as it did on the earlier units.
The disassembly/assembly is per the Lotus manual with two corrections:
(1) In the pinion assembly section, page 10, the text describes
fitting a new rubber `O' ring on the pinion retaining ring and
references Figure 11. However, Figure 11 does not show the pinion
retaining ring. Regardless, the `O' ring for the retaining ring is
available; just ignore the figure.
(2) When setting the location of the Sleeve Nut locknuts, the text on
page 12, #7, says: "Screw the locknut on to the end of the rack so
that its position corresponds with dimension 3 + 4 + 5 + 3 on Fig. 6,
i.e. 24.42 in. (62.03cm) between inner locknut faces." However,
adding the numbers in the referenced figure gives a result of 24.82
in. Based on the measurements I took before disassembling my unit, I
believe that the 24.42" is correct and that the drawing notation is
wrong. Hopefully, Mike Causer will be able to retrieve the CAD
drawings he has and we can confirm this.
New boots (also called gaiters or bellows) and clamps are readily
available, but are Spitfire units. That means the boot is a bit tight
on the inboard passenger side, because of the larger diameter of the
housing extension. That is no problem for the boot, but make sure the
clamp is big enough; the standard Spitfire wire-type clamp is too
small. On the driver side, the large diameter end of the boot is
meant to be attached with a tie-wire, rather like the safety wire used
on race cars. There are large wire clamps available that will work,
but be careful about using a modern hose clamp. Aesthetics aside, the
tie-wire channel is too narrow for a modern hose clamp, causing the
hose clamp to bear-down only on the ridges.
Russ
'74 TCS 2776R