Technical


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Extract from March's Octagon Car Club Bulletin

QA Technical Torque

March has come around again which means that much of this column is devoted to the Index for 1997 complied by Bob Snowden, thanks again Bob. In addition to the Questions there is also one of Neil Cairns' engine articles which was originally scheduled to appear in the January issue but has been delayed because of pressure on space. I have also included one Technical Comment from Brian King, a former railway engineer, a potential safety issue which John had to hold back from the February issue. Co-incidentally, Ernie Smith's, piece on axle repair appeared in the March issue last year. The March issue has usually been restricted to the index plus questions; its expansion to fill the available space is a very good sign because it means that both John and I are receiving plenty of material from you. There's still no room for compalcency, however, so keep up the good work and keep sending your technical questions, answers, tips and comments to:
Malcolm Taylor, Whisket Green, 56 Daisy Lea Lane, Huddersfield. HD3 3LL.

Questions

  • We used to get a great deal of advice on SU carbs from the late Don Jackson but we do not appear to have had much information on SU fuel pumps. I am considering fitting an electronic implant to the pump on my 1949 TC. The implant manufacturers suggest that it would be better if fitted to the AUA66 instead of the AUA25 fitted to the TC. Does anyone know why? The only apparent difference between the two types is the outlet union and the fact that the AUA66 has a 4BA earth screw in the coil housing. Presumably there is a technical difference between the two pumps. What is it? There are 5 different pump diaphragms, why? Is any member able to write an article on SU fuel pumps, giving their history and the reason for the changes?
    Don Spurr, Portishead, Bristol.

  • We use our TF most days; for shopping, going to the post etcetera. Recently someone whose parents were presumably unmarried tried to steal it. Fortunately they failed. Does anyone have any advice on how to thief-proof such a car? Our concern is that the thwarted thief may take his frustration out on the vehicle and I want to prevent this.
    Robert Marshall, Bath.

  • Is the starting handle crank chrome plated on a TC?
    John Libbert, Milford, Ohio, USA.

  • The hinges on the bottom seat slides on my TC are in need of repair by welding the two halves back together. Are the hinges straight when attached to the floor or is there an angle to provide clearance for the chrome handle of the adjustment lever?

    It appears that if they are straight the handle would interfere with the hinge. What type of plating do the slides have?
    John Libbert, Milford, Ohio, USA.

  • Why are the T-type brake drums retained by slim 'half nuts' which strip so easily? I have fitted full size nuts to mine with no apparent detriment. Placing "Blue-Tac" on them before fitting the wheel proves that there is sufficient clearance.
    Ian Thomson, Newark, Notts.

  • The windscreen wipers on my J2 miss the screen and are useless. In addition, my regular passenger dislikes the presence of the wiper motor on the screen. Am I legally required to have wipers? I'd like to remove them, but....!
    Bob Snowden, Exeter, Devon.

  • I have recently purchased a 1939 TA which I believe should have a central lubrication system. Apart from the brackets attached to the bulkhead, I have no other clues as to the rest of the system. Can someone please advise me as to the size of the pipes required and/or necessary fixings to the handbrake cable, springs and bulkheads brackets. A guide to the correct route of the pipes would be helpful and as would any advice on where to purchase all the necessary parts. Is it a worthwhile exercise or is it better to leave well alone and grease the nipples directly?
    John Patman - Epsom, Surrey.

  • I have a late TD (Chassis TD24545) which was repatriated from the U.S.A. Someone has converted it to RHD leaving the original pedal box in situ. In the base of the box is what looks like some kind of stop, cylindrical in shape and mounted so that it can be adjusted fore and aft. The new box has a similar slot in the base but nothing fitted. Should the stop be moved to the new RHD box and what is the adjustment? I have searched the Workshop Manual and various Parts Catalogues but cannot trace it.
    Ernie Evans, Derwen, Corwen.

  • Has anyone fitted lap/diagonal seat belts to a TF or TD? The obvious anchorages are the side of the transmission tunnel, the floor and the top of the wheel arch. Who was the supplier, what size backing plates were used and were they welded? Any problems and exact locations would be helpful. I know kits are available for Midgets & MGB etc but these cars have factory fitted anchorages.
    Brian Archer, Bath.

    Tips and Comments

    Stub Axle Repair
    The repair described by Phil Marino in the December Bulletin was of great interest to me - a retired railway engineer - as the principles involved are those used when fitting railway wheels and axles together. Two aspects need caution:-

    (i) Fretting is a risk where the axle exits the yoke at the bearing end of the force fit. Time will tell if the proportions of the design are adequate.

    (ii) The photograph of the axle appeared to show a very sharp radius where the axle exits the yoke on the bearing side. The combination of high bending moments, axial force and a sharp radius may be undesirable. Notches or scratches in this area could raise stresses by factors approaching x10. Is there scope for a much larger radius? A form tool and a 'water' finish would be good practice.
    Brian L. King, Quarndon, Derby.

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