Technical


Click here to add your MG News.


Extract from February's Octagon Car Club Bulletin

QA Technical Torque

There is another article on steering box replacement in this issue. I suspect that some of you will sigh and say "not again" or perhaps something less polite. I justify publication as Rodney Powell's article adds something new to what has already been printed. Furthermore, it demonstrates, yet again, the ingenuity displayed by Octabods in overcoming problems and also the beneficial co-operation between enthusiasts. In the November issue John, our new editor published a list of deadline dates for the Bulletin. Please note that these are dates by which material should reach him. Clearly, material for this section must reach me sometime before these dates and as John uses this column as the basis for the whole magazine he likes my copy before these dates. Effectively, therefore, material should reach me at least 10 days before these published dates. But, whenever it comes I'm always ready to receive your contribution at:
Whisket Green, 56 Daisy lea lane, Huddersfield. HD3 3LL.

Questions

  • I've often thought of fitting wire wheels to my TD. Are they as easy to fit as the suppliers of conversion kits say? What are the pitfalls? Several spares I have brought have been faulty or needed additional work.
    Roy Williamson, Hickling, Norfolk.

  • Comparing the distributor fixing method on the XPAG block in my YB with that in a spare block, an earlier engine number; the earlier fixing is clamp and pinch bolt but the latter one is by cotter pin. The distributor with the cotter pin fix has a flat ground on the body which appears to correspond to the pin location. If the body has to be capable of rotation to adjust the timing, what is the purpose of the flat? Otherwise the two distributor bodies appear to be interchangeable. Is that a correct assumption?
    Finally, the clamped distributor was fitted with an earth lead from clamp to block, but the pinned distributor has no separate earth and runs quite happily without. Does this imply that the later fix provides a better electrical contact between body and block?
    Roger Clements, Stroud, Glos.

  • Further to Neil Cairns interesting article on engine threads, in the September Bulletin, are taps and dies available which correspond to the French metric threads in the XPAG?
    Roger Clements, Stroud, Glos.

  • When I stripped the brake master cylinder on my YB I found that the steel spring shim which sits between the piston and the cup was missing. Presumably this shim has no function when breaking, is it there to aid fluid flow when bleeding? Incidentally, NTG could not supply this shim but recommended me to J.E.M. in Hinckley who were able to supply as a separate item for a few pence, or as part of an original Lockheed repair kit.
    Roger Clements, Stroud, Glos.

    Answers

  • Can any member advise me of a good, long lasting, very high temperature resistant finish for cast iron exhaust manifolds? I understand that powder coat finishes will not stand up to the demands required. (311)

    Advice on what products to use has been going for some time. The product HYCOTE (very high temperature paint - aluminium colour) has worked well for me. The instructions advise the article should be either cleaned with abrasive cloth or grit blasted prior to spraying. I opted for the latter which cost me 4.00. By reading the maker's instructions before I carried out the operation - rather than after (I expect we have all been guilty of that) I still have a finish which is as good as when applied some 1,500 miles ago.
    Colin Mulford, Coulsden, Surrey.

    Can anyone tell me where I can obtain the screws which hold the windscreen frames to the central support of my 1930 M-type. (322)

    I do not have an M-type, but when I was looking fir six replacement screws which do the same job on my TF, I opted for stainless steel. At a motorcycle autojumble I purchased six Philips head counter-sunk screws of 1" in length and 3/16 BSF thread. (They also pass through a 2 BA die). I then machined the heads to a convex profile - as sketch - in my small model makers Unimat SL lathe. The screws were cut to individual lengths to suit their placement in the frames. This was done to avoid the screwing into the glass and splitting the windscreen which is easily done. Finally, the heads were polished to resemble a chrome finish. The supplier I brought mine from was AIDPAC, tel. no. 01902 781120, who stock a vast range of stainless steel fasteners. (Colin included a sample of what can be achieved with little (his description) effort, the end result is certainly very effective - MT).
    The M-type screws of 5/32 BSW are the same thread as used in the famous Hornby product - Meccano. You may be able to pick up some brass ones at a toy fair but these have a cheese head which will need re-profiling. You could also try model engineering suppliers for the screws either in steel or brass. Or alternatively uprate to a 2 BA or 3/16 BSF thread which are more readily available.
    Colin Mulford, Coulsdon, Surrey.

    Why does the speedo needle on my TD fluctuate wildly? (322)

    After having the trip mechanism repaired on the speedometer of my TF I duly lubricated the inner cable with light oil and ensured the outer casing had no sharp bends. But prior to fixing the cable into the speedo head I made and fitted a felt washer between the spigot on the speedo and the ferrule on the outer casing. I seem to recall that in a previous life this was done on Smiths speedos fitted on motorcycles I had in the early '60s. The purpose being to absorb any oil rather than have it pass into the speedo head.
    Colin Mulford, Coulsdon, Surrey.

    Tips & Comments

    SAFETY FAST IN A TC!
    CAN IT BE ACHIEVED?

    Since completing the restoration of my 1946 TC some 6 years ago I have, like many other Octagon contributors, felt unhappy with the standard cam and peg steering box, and have spent some considerable time and money on replacing all the vital components in an effort to achieve a satisfactory level of safety and lightness. Over a period of time I have fitted a new sector shaft, peg and worm and bushed the box itself, and while all this had undoubtedly reduced play, and improved general driveability, I still felt unhappy with the level of heaviness and the inherent mechanical inefficiency of this box.

    My thoughts therefore turned to complete replacement and, prompted by Mike Sherrell's TC's Forever and letters previously published in the Octagon Bulletin, decided to try the Datsun solution. Like, I suspect, others before me, I found the biggest problem is to find the right box, and as someone mentioned previously, I found that I drew a complete blank with scrap yards. I did however by a stroke of good fortune, manage to buy a complete Datsun 1200, 1973 vintage, having the apparently correct short steering box, which in this case was fitted with a collapsible column. A solid column might have been preferable as it could be easier to convert to suit the MG and these I think were fitted to the slightly earlier 1970 - 72 Datsun 1000 and 1200 "Sunny" models.

    Another difference between these boxes, apart from physical height, is that the short box has two mounting holes placed to the rear of the sector shaft and one in front, whereas it is the opposite configuration on the taller box, i.e. 2 to the front, 1 to the rear. As stated, I used a short box and therefore the drawing shows the adapter box drilled accordingly. Use of the taller steering box would obviously require its mounting bolt holes drilled in the appropriate positions.

    I believe the "short" box with collapsible column was only fitted up to '73 and thereafter a slightly "taller" box with similar top casing dimensions was fitted which I think is equally useable.

    The box I thus obtained had done 46000 miles, but I thought it would be sensible to strip it down for inspection. The condition inside was like new with no detectable wear anywhere and I was very impressed with the standard of machining and general design. The box is, of course, a very, mechanically efficient recirculating ball type giving 2 3/4 steering wheel turns lock to lock, compared with the original TC box at 1 3/4, further contributing to lighter steering by lowering the gearing.

    Fitting this box to the MG posed a few problems but nothing insurmountable and I offer my comments on this in the spirit of advice only - you obviously have to decide if you are happy with my solutions and methods before embarking upon such a project.

    The first problem is how to mount the box to the chassis, utilising the existing mounting points as I am retaining the original box and column in case some further owner wishes for complete originality. After giving this much thought I concluded that a simple hollow rectangular section adapter box with open top and bottom measuring approx. 4.5" by 2" by 5" high, fabricated from 1/8" mild steel would be needed to space the Datsun steering box off the chassis and bring it into the correct position. The made-up adapter box bolts to the chassis via the existing three mounting holes and the steering box is then bolted to the other side, with nuts being accessible in both cases from the inside of the adapter box section from beneath the car. My drawing should make the idea clear; although a cut away to clear the bonnet catch and its bolt heads, and a stiffening fillet welded across the top, are not so clearly shown.

    The second major problem is how to modify the steering column to fit the TC and accept the MG steering wheel boss. Not wishing to destroy an original TC column, the solution is to use the inner shaft from a Riley RM series which is the same outside diameter and has the same serrations at the upper end and although these serrations are not quite as long as those on the MG, they will accept the boss and give some fore and aft adjustment. The Riley shaft is also hollow, like the MG. They are reasonably easily available via Riley spares specialists and mine at least was not expensive.

    The Datsun outer column is removed completely and the inner shaft, which at its lower end is solid section, is cut off about 18 inches from the box and about 3 inches of its length is turned down to a tight sliding fit to go inside the hollow Riley shaft. I then welded the two together and for good measure put a roll pin through as well. The outer column is made up from 1.25" outer diameter mild steel exhaust piping welded at the lower end to the steering box flange. Do not buy a Riley outer column as its diameter is too large. One and a quarter inch o.d. tube is of course the same size as the original and will therefore fit through the rubber bulkhead grommet and fit the upper support bracket. I used a standard felt bush at the top end, available from Naylors, and this works very well. The Datsun drop are (Pitman arm) is cranked up in shape and accepts the MG ball joint so connection to the MG steering linkage is no problem.
    Like others before me, I find this conversion is marvellous. The steering is light and precise and the whole car seems to be transformed and a real delight to drive both when travelling fast or for slow manoeuvring. The steering will now "self centre" after bends and I can put the car through gaps that previously made me grey!

    As mentioned, I think the real problem is to find a suitable Datsun box. There is however another possible solution. Consider using a Ford Anglia 105E box! Like Datsun this is a light to use recirculating ball box, compact in size and in some ways appears easier to fit to a TC than the Datsun one in that it only needs an adapter plate of about three eighth inch thick mild steel interspaced between it and the chassis. Again, the original MG chassis mounting holes can be used and a Riley inner shaft adapted to suit. I have done this job but I have seen and driven a TC converted along these lines by a friend, Norman Brock of Street, who did this job many years ago and has been delighted with the results ever since. It works wonders for his MG, just like the Datsun version. I am much indebted to Norman for the information on this Ford conversion and the idea of using a Riley inner shaft, as well as allowing me to crawl about under his car taking notes and measurements. I do not think, however, that the Ford box is quite so well engineered as the Datsun unit and the example I obtained (history unknown) to evaluate for this project had a lot of wear in the lower sector shaft bush and the worm didn't look to cheerful either! These Burman boxes can be reconditioned or exchanged via older Ford spares specialists and while this is not particularly cheap it does offer the possible advantage of being more easily available.

    The Ford outer column is only one and one eighth inch o.d. but this can be corrected by sleeving it over with the aforementioned one and one quarter inch o.d. exhaust tubing, which has, rather conveniently, a one sixteenth inch wall thickness, and therefore fits over perfectly. I would leave about 12" of the old column tube at the lower end, slip over the new one and one quarter inch tube, drill a couple of quarter inch holes near the bottom and plug weld through to the tube within.

    Another small problem to overcome is drop arm length. The Ford is three and a half inches between centres compared to the TC at five and a half inches. Some lengthening will probably be necessary, preferably by someone who knows his welding!

    PS. I have a Datsun box available if anyone is interested! Tel: 01408 813577
    Rodney Powell, Ottery, St Mary, Devon.

    Bonnet Support for TC

    I've used for several years a really simple system that took 10 minutes and no cost to make. It requires two bits of wood, piece of electrical cable and a hook - oh yes and the ability to tie a knot. Could be made much more elegant, but I enclose just the basic idea for all you experts to titivate up into a Concours winning product!
    Oh yes, and a request - does anyone have a spare domed chrome nut to secure original type TC wipers which are retained by the nut on the front of the wiper arm, rather than the common replacements that have the nut behind the arm, which are as common as muck! Spares suppliers don't do this item.
    Les Meer, Worcester.

    "To Solder or Not to Solder, That is The Question"
    Over the past year I have been informed several times that Joseph Lucas issued an admonishment against soldering the ends of wires that were to be squashed down in grub screw connections (T-series switches, voltage regulators, ammeters). This 'don't solder' information appears as a general directive on page 50 in Mr. Norman Nock's book, Tech Talk. Norman served an apprenticeship at Joseph Lucas in the 40s, and I have every reason to believe that this 'don't solder' information has been accurately passed down through the intervening decades. Several expatriated Englishmen who reside in Southern California, and are members of local T-series clubs, relate similar stories. As a group these gentlemen are both knowledgeable and technically astute. Most of them relate similar stories: soldering produces a stiff end that does not squeeze down properly when a grub screw tightens. As a result, the grub screw does not bite into and grab a soldered end as well as it does an unsoldered end. Additionally, when several soldered wires are brought together at a post the height could result in too few threads being engaged on the grub screw thus spreading the slotted post as the screw is tightened. Is anyone in the OCC aware of a Lucas Service Bulletin advising against the soldering of ends? If so, was it directed towards grub screw connections. The electrical connections employed with the horn button utilise a conically tipped screw that is driven down the axis of the stranded horn wires. In this particular case it would understandably halt the spreading of the strands of wire and thus defeat the connection protocol. Other than this horn button connection, I have slightly twisted and soldered every wire end on the harness in my TD.

    Assuming this dictum existed and was applied to T-series, let me now present a contrary view on soldering ends. Soldered ends can be accommodated by these connection posts if the soldering and wire forming is performed properly. Proper soldering means enough solder to flow nicely into the twisted end, but not enough to obscure the stranded nature of the wire. Proper forming is required when several wires are brought together in the same post. I use round nose and flat nose electronics pliers to shape the soldered ends so that they nicely spread out and fill the bottom of the post. I have been soldering the ends of my M.G. wires for 40 years and never knew I had a problem. In fact, I deplore tightening a grub screw on loose strands of wire because the grub screw has propensity to cut off individual strands of wire. Additionally, I find the grub screw more likely to back out from a mat of stranded copper wire than from soldered ends. The solder (an electronic eutectic grade of 63% tin 37% lead) cold flows into surface imperfections on the tip of the grub screw. The solder seizes the grub screw nicely and the screw does not back out. What is Lucas talking about? Copper is the harder material, it does not cold flow well, and it is more prone to breaking. Solder is a more ductile material than copper. Was the soldering alloy used in the UK in the 30s a harder alloy than the tin-lead eutectic? If so, perhaps I am comparing apples to oranges and I don't know it. What is certain, is that I have been soldering the tips of stranded wire together for decades and have never had a hint of a problem.
    As a complicating parameter, I have not been soldering my original Lucas harness. After a year of ground (earth) return problems and grub screws cutting off strands of wire, I removed my Lucas wiring harness. I then made my own harness, in 1956, because: (1) I looked askance at the untinned wire used by all automotive manufacturers, (2) I wanted to add a fuse panel with separate fuses for each circuit, (3) I wanted to add additional lamps and devices, (4) I wanted to add a kill circuit to complicate drive away theft, (5) I wanted a ground return wire from every lamp and device and, (6) I wanted all the ground wires to return to a common Mecca ground that would consist of a 5/16" thick brass plate covered with an orderly grid of 10-32 (~2 BA) tapped holes. That would put the ground return problems to bed 'in perpetuity' - it did.

    The tinned wire nicely accommodates soldering of it ends and eliminates the necessity of scraping off the copper oxide that forms on untinned copper wire. (If you wish to construct your own wiring harness, use vinyl covered stranded wire from the electronics distributors and specify high temperature vinyl. I don't think Alpha or Belden make untinned stranded wire or use a low melting point vinyl. The wire sold in automotive stores here in the States is generally insufferable junk produced by the lowest bidder in Taiwan - you don't want it.) Enclosed is a photograph of the flattened soldered wires as withdrawn from the grub screw connections on my voltage regulator. The soldered wires were squeezed together and flattened in a model manner - is there something I'm not aware of?

    Perhaps the engineers at Lucas were worried that some owners would use an acid flux in soldering. This would be poor practice as the acid would wick down the twisted wires and then proceed to corrode the copper. (Rosin core solder should be used exclusively) They would also have been concerned with the production costs required to solder and shape wire ends. Unsoldered and untinned stranded wire is certainly cheaper. Also, the original rubber insulation doesn't take kindly to the temperature (365°F+) required to melt solder.

    This concludes my contrary view on soldering wire ends on T-series. Does my sky now darken with arrows and darts from cadres of Lucas Aficionados? (Memories of the 'rotor arm debate' leave me waiting expectantly! MT)
    Carl N. Cederstrand, Brea, California.cederstrand@earthlink.net

    I hope that you have enjoyed this issue. Please keep writing to me. Malcolm Tayor, at Whisket Green, 56 Daisy Lea Lane, Huddersfield, HD3 3LL.

    Octagon Club Home Page

    Back to the News content

    [Copyright/Credits] [Home] [Information] [Feedback]
    Made in England