This is a heads-up on something that isn't generally known about the Spitfire rack. It has a central section, the bit of the rack that comes into action in straight ahead driving where the teeth have been cut fractionally shallower, that is more metal is left on the rack leading to a high point in the teeth. The shims to minimise pinion backlash are adjusted [in the Spitfire] at this point. That's all fine so far because when the car is steering a corner the rack is under load, but has a fraction more backlash where the teeth have been cut deeper.
Lotus took a standard rack and moved the effective centre point, the straight ahead position off-centre. This means that if the rack is adjusted for minimum backlash at the straight ahead position it will jam when it reaches the high point in the rack. This only applies to types 54, 65 and standard TC. The TCS had a different arrangement where the rack is properly centred.
Hi. Also as a newbie, I have been doing some research on a possible replacement for the Herald/Spitfire rack fitted to my 1969 Lotus Seven Series 3. Ages ago I photocopied some pages from a book I found at my local library regarding the Triumph Spitfire. I cannot recall the author or book title to give credit unfortunately, but a full description of the mechanical properties of the complete rack and ball joint assemblies was provided. The book confirmed that the middle teeth (I would have to count them to confirm) were machined 5 thousandths of an inch higher than the rest to provide 'stiction' (hope this is the correct term?) in the straight-ahead position.
Also as noted on the Mcleans Bridge site, the geared rack 'bars' and tie rods were manufactured in various lengths. I have 2 Spitfire racks where the rack bar is 26 inches long, but recently obtained a spare where it is 25.5 inches long (TR4?). The Mcleans Bridge site provides excellent information on the various racks produced by Alford and Alder/Triumph. The measurements are given in metric values, but the U.K. did not begin going partly metric until 1965. Before and probably quite a time after that date, the U.K. was still using Imperial measure, and I am guessing that most of the Stanpart items were still Imperial values until well into the 70s?. I am grateful to the administrator for reproducing the article from the Club Lotus magazine by Brian Buckland, as it provides clarity on the modifications performed/required by Lotus. For the Seven, 2 - 1" long rack stops were provided of 1 inch outside diameter for a sliding fit on the rack bar., and the tie rod thread was shortened along with the outer ball joint (3/8" and 1/4" respectively). One of my racks came with tie rods of exactly 6 inches long, and these are not cut from a longer version. They were produced to this length and have the lathe centres at each end. Unfortunately one of them was probably 'curbed', and is not safe for re-use (on an Elan for instance). I have also investigated the new German manufactured racks produced for Triumph vehicles through the German company 'Bastuck'. I was sent a couple of emails by a sales rep. that shows the tie rods as attached to the geared rack bar. These racks do not use a locking nut to secure the tie rod ball joint to the rack bar. Unfortunately, the sales rep could not advise if the tie rods could be unbolted to allow the fitting of necessary rack stops as fitted by Lotus. It seems no one has had to disassemble a German rack as they are still fairly new. Various Triumph sites proved negative in this respect. Forum members on these sites confirmed that Argentine manufactured racks are sealed for life and cannot be safely disassembled. Although cheaper than the German units, there were some negative comments on these South American racks regarding quality control. I have a page from an old Dave Bean parts catalogue that may have been copied from Lotus if anyone is interested? It shows the various rack parts for the Elan and Plus 2 and shows the rack extension for the Europa. I contacted a sales person at DBE, and was advised that they had sourced a German manufactured rack from British Parts North America to see if it would be suitable for a Lotus. DBE advised that they thought that it 'would not be suitable', although they didn't explain why or how much they had attempted to disassemble the rack assembly. If of any value, and with the administrator's permission, I can post the DBE Lotus rack page, and also the photos of the German rack with the bellows slid aside. Cheers, EW
