- About Martyn
- Leonard Lord book out NOW!
- LATEST NEWS
- MUST READ!
- NEW! The Martyn Nutland interview on AROnline
- Lord Biography: The Reviews
- Martyn on the BBC
- LATEST ARTICLES
- NEW! Lord biography: What readers are saying...
- Leonard Lord
- Photo Gallery
- MARTYN'S BLOG: I Took the Road Less Travelled...
- Leonard Lord biography extracts
- Austin Times Archive - NEW!
- Cambridge Specials
- The Bentley Years
- Bentley Mark VI Book
- More Austin News
GIVE ME A BRAKE
It’s generally agreed that Austin Seven brakes are inadequate, most noticeably for today’s traffic conditions.
The reasons are two-fold. Shortcomings in the design of the brakes themselves – insufficient surface area, unsound positioning of the front operating levers plus overall design faults, such as lack of rigidity in the early chassis frame and a failure to positively locate either the front or rear axles.
This situation begs the question as to whether the enthusiast can improve the situation within the spirit of the Austin Seven’s eccentric, characterful concept. Such a premis rules out ‘hydraulics’. Increasing the drum area is not feasible and positive location for the front axle is complex and may have detrimental side-effects.
However, one area I thought I might examine was the cross-shaft for the rear brakes on cars with an uncoupled system (pre-1930).
The cross-shaft is often blamed for uneven braking at the back, although it has to be conceded that many experts discount this theory.
'Winds up' axially
Yet, if one does subscribe to the belief – and it seems reasonable, because the driver is able to apply, on the right of the car, disproportionate leverage to the cross-shaft than is available on the left. Thus, to exaggerate wildly, the tubular shaft behaves like a stick of barley-sugar or liquorice, and ‘winds up’ axially.
Why should this be?
Firstly, it’s a tube not a solid shaft. Secondly, it has very inadequate support on either side of the car where it is attached to the chassis side rails; and no support at all in the centre.
The chassis attachment is by circular bracket , crudely shaped from thin steel,
and riveted under each side rail, then fitted with a flimsy, bronze wrapped bush that has no provision for lubrication.
What if we provided the brackets with stouter bushes that could be conveniently lubricated? Then strengthened the cross-shaft ends and gave them solid support over a proportion (albeit small) of their length?
A key issue, of course, is how much wall thickness we can provide in the new bushes to make them worthwhile. I decided to aim for about 3mm and did, in fact, manage 2.6mm.
The first stage is to obtain a cross-shaft about 52 centimetres long (the inside distance between the chassis brackets. It’s best to cut new tube of about 2.5 cm outside diameter rather than shorten the existing shaft. This is preferable as any modifications to an historic vehicle should be easily reversible. (Mallard Metals would be an excellent first port of call for the tube firstname.lastname@example.org).
We now need two spigots, each with three steps of differing lengths and diameters.
The material I used was one inch EN24 bar, readily obtainable from Noggin End Metals where you are assured of excellent and friendly service email@example.com
Pedal and brake rope
The first, and smallest, ‘step’ on the spigots is to enter the shortened cross-shaft/tube; the second, to provide a journal for the new bushes, and the third, to carry the brake levers. These will be clamped to it, whereas before they were fitted directly to the cross-shaft. They connect, at their other ends, to the brake pedal and brake rope on the right, and just the rope on the left.
The length of the spigot that enters the shaft is not critical as long as it does not interfere with a peg on the right side of the car that anchors the return spring. Say around 30/35mm’s penetration.
The journal length is more important. The chassis bracket is 35mm wide and this section of the spigot needs to occupy it completely. The diameter of the journal should be about 22.5mm calculated on the basis that the internal diameter of the bracket is about 27mmm (It varies slightly from car to car). As can be seen, these sums allow for a bush of respectable wall thickness.
Economizing on metal
Once again, the width of the sections that take the brake levers is not critical as some (2-3mm) protrusion of the spigot beyond the lever bosses is acceptable. The diameter needs to be about 27mm for a snug fit in the levers before clamping.
How the spigots are set up for turning is largely a matter of personal preference with a view to economizing on metal.
When it comes to the bushes, I turned the external diameter (about 27mm – see above) over 35mm (width of bracket), then turned the bronze bar (Noggin End again) end for end to operate on its twin. Leave a ‘boss’ between them at least 1cm wide. This is convenient for gripping the work in the later stages of the job.
Cut the Siamesed bushes off the raw bar but do not drill/bore or separate them yet.
Fitting the turned, blank bushes to the brackets to obtain a tight fit calls for some patience and much trial and error because of the crudity of the original design. The brackets are likely to be neither round nor smooth and parallel internally. However, very gradual reduction of the outside diameter of the bushes on the lathe, and plenty of grease, should allow them to be driven in temporarily.
Don't forget the lip
When finished the bushes should have a lip about 3mm wide that bears on the outside of the brackets and abuts on the brake lever bosses. I.e between the two.
Don’t forget the lip width is additional to the length of the bush.
Remove the bushes – still joined in the centre - from the second bracket you tested for fit and return to the lathe. You can now turn down the boss between them to about 35mm. This will be the outside diameter of lip
How you make the hole is, again, a matter of personal preference. I drilled them to 18mm diameter on my lathe over about 40mm (just beyond the finished length) then enlarged the hole with a boring tool until it was just under the internal diameter required to take the journal. I then separated the bushes (i.e. cut through the boss to leave the 3mm wide lips), reversed them in the lathe chuck and enlarge the hole until the journals turned freely in them, without axial ‘play’. An advantage of finishing the bushes from the lip end is that you can accurately clean-up what was formerly a blind hole.
Now use a draw bolt and washers to insert the bushes, well greased, in the brackets.
Really tight fit
I intended to secure the cross-shaft to the spigots with taper pins. But after much wasted effort found I did not have the skill to accurately create either a tapered hole or pin. Instead I resorted to sawn off Austin Twelve big end bolts inserted, to ensure a really tight fit, into reamed holes.
If you are able to produce a taper pin and hole, the pin on the right side can be made with a slightly more pronounced head to accommodate the hook on the cross-shaft return spring. Otherwise you need to drill a hole in the shaft and tap it to take a short peg. Model this on the original and ensure it is correctly positioned i.e. pointing towards the back axle, when the brake levers are clamped in the correct position on the spigots.
To clamp the levers first hold each spigot in the vice and fit its lever at the angle
at which it will stand when the brakes are off. This is, more or less, vertically upwards. A few degrees one way or the other doesn’t matter as there are adjustments in the system that will correct a minor discrepancy.
With each lever in position I inserted a paint brush through the clamp bolt hole and put a dab of paint on the spigot. A sharp scriber will work equally well. You now need to make a groove, at the point of the mark, so the clamp bolt can pass. The ‘posh’ way to do this is with a milling machine but a round or half-round file is just as appropriate.
Now drill right through the chassis brackets and bushes and tap for a grease nipple angled in the direction you are going to find most convenient.
Finally hold the cross-shaft in position with the return spring already fitted over it, pass the spigots through the bushes from the outside of the chassis and into the shaft, line up the holes in shaft and spigots, tap through the bolts (or taper pins) and secure. Place the brake levers on the ends of the spigots and tap through their clamping bolts and fit the nuts. Locate the tail of the return spring on the chassis cross-member just behind the gearbox. Grease the bushes.
Whether any of this will improve the early Austin Seven’s brakes remains to be seen. But in my humble opinion it is an improvement on, and a more elegant version of, the original.
The author takes no responsibility whatsoever for any untoward consequences of following these procedures or adverse effects they may have on vehicles to which they are applied.
ANCIENT CHINESE PROVERB SAY…?
It was one of the great philosophers, who, when alluding to the travails of humankind, suggested the easiest way out of a room is through the door.
To make an analogy; there is no doubt the easiest way to dismantle an Austin side-valve engine is in the way Austin intended. Yet, to revert to the oracle’s philosophy – what if there is no door?
Some years ago I rescued most of a Light Twelve Four New Ascot engine from a breaker’s yard. It was a deal along the lines of: ‘There won’t be any more where that came from “squire”. If you don’t take it now you will always regret it’.
That is not exactly what I have always regretted.
By one of those universal automotive compulsions the cylinder head had been removed and set aside. By a non-compulsive, but nefarious act, so had the sump so the crankshaft could be stolen.
Laid on its side for the latter deed and left indefinitely in an open shed, the elements had excellent access for seizure.
In 40 years, no engine, stuck or seized, has ever defeated me. This one is coming close. After six months standing with diesel filling the bores a sharp (extremely) blow on the piston crowns yielded not one millimetre’s movement. The same procedure, after focusing a blowtorch through the core plug apertures and onto the cylinder walls, likewise.
A dear friend from overseas was quite gung-ho about the situation. He broke my hammer. I followed his example by breaking a larger one and injuring my elbow. The local blacksmith took over. After 30 tonnes on the press he gave up for fear of bursting the block I was trying to save.
In the absence of an Excalibur toting Arthur I resorted to drilling a circle of holes in each piston crown, removing the ‘bridges’ with a chisel, then driving out the sections. Even this requires an inordinate amount of hammer-power. (Ecky Thump’s tip – don’t be tempted by the aluminium being thinner in the middle and bash too hard in this region. You run the risk of distorting the connecting rod’s little end.)
All the foregoing is just ‘easy-peasy’ compared with what comes next. Valve removal.
Remember the philosopher’s words and consider the problem. The valves are, needless to say, seized solid in their guides: some open, some fractionally so, others fully closed. The tappet blocks, thus inaccessible from above or below are seized in their guides. Just to add interest Ecky’s close relative, Bill Bigend, has tightened the tappet lock nuts with a torque that would comfortably anchor the Forth Bridge from a single bolt, and, into the bargain, rounded the flats.
Of the valves that were open, or partially open, I managed to extract three – mile-long stems (thank you Lord Austin!) It is, now, of course, simple to fish out their springs and remove the tappet assembly.
So I have a dream. If I could drive the camshaft forward so the cams were clear of the bottoms of the tappet blocks, could I get a drift onto the blocks and drive them, and thus the valves, via the tappet, upwards and out.
I discover the shaft will already move forward, but only about a centimetre, because the journal for the centre bush then fouls the adjacent tappet block. Fortuitously this controlled one of the valves I removed.
Therefore, for my cunning plan to work, I must remove this block and clear a path for the journal (and thus camshaft) to shift sufficiently forward.
I made a draw bolt type tool to insert through the void valve guide and screw into the tappet block. With a washer covering the valve seat the device successfully lifted the tappet block.
Ladies and gentlemen, you will be distressed to learn that this minor success was of minimal avail. The camshaft will not move further forward. I guess this is because the fully open, and partially open valves that remain, with their Herculean-tight tappet lock nuts, are exerting sufficient pressure on the cams to prevent it doing so.
In our French village we have a charming scrap man called Monsieur Ritz. As yet unbeknown to the gendarmerie, he has attached one of their two-tone sirens to his truck and when it intones as he passes your door, you know he is collecting.
Could I put to you experts: Should I respond to the call of M. Ritz? That would be defeatist and a pity. As my old, car breaker, friend said: ‘There won’t be any more where this came from “ squire” ’. And one day, someone, somewhere, will need an uncracked, recoverable, cylinder block to save one of my favourite Austins – the New Ascot.