Ruby steering arm

[Graham Barker]

After using emery paper on my Ruby arm, I couldn't see any crack. Fortunately I decided to take it to a firm that tests welds. Their phosphorescent dye penetrant soon showed a crack in the curve of the arm. 
Coincidentally I gave them £10 ( NZ$20) for their social fund, as Did Howard Wright, although we are a world apart.
Bought a new arm sold by David Cochrane which was a perfect fit. 
Cheers 
Graham

[Bob Culver]

Arms do not crack just at the radius but also sometimes at the shoulder, although the radius crack is usually bigger. The shoulder cracks are hard to see unaided. if fully seated and tightened would not occur but the seating often uncertain. Keeping greased reduces the considerable accelerating corrosion contribution but makes cracks more difficult to see. 
Fatigue is a slow process so if no detectable cracks OK to use.
Lord Austin should have lost his title for continuing the arms so long. 
Although maybe on low grip  unsealed roads with lightweight occupants,  parking spaces readily accessible, little trouble was evident into the 30s. Older motorists were also taught not to force the steering esp when stationary. (The steering on modern power steer cars must be made of tough stuff!)

Not certain that the pattern in the  very corroded arm is a crack. There is a tendency for emery to burnish metal over cracks and conceal, although the magnetic black fluid method usually reveals.


My father never considered the steer arm failure incident with our car 70 years ago trivial! Got the fright of his life. Total mileage then about 60,000!

[Parazine]

It's probably worth repeating, for those that have them, that the steering box drop arms on hourglass steering boxes ('37 - '39) are also prone to cracks and to breakage. I've seen two of these late drop arms snap in my Austin 7 career, one of them I was the driver. So worth a check when you're underneath.

[Bob Culver]

After the steering failure my father became very crack conscious. So when i took over the car we took all arms and stub axles to a local firm equipped with the then not common detection eqpt. The owner quite enjoyed the hunt. He was located opposite a local car racing track (Levin) which served a vast area and recounted tales of racing cars riddled with cracks! His fee was the "price of a packet of fags". At todays cigarette prices we would not have been impressed. The lh stub axle was half way through its wall thickness. The car had been driven extensively on very corrugated roads and all roads were very rough for years following minimal  mtce during WW2

[Graham Barker]

This is the steering box on my 1937 Ruby. Is this what you mean by an hour glass box?    

[GCD]

I also have a '37 Ruby with this style steering box & arm- Guidance on where to look for cracks in the arm would be on help please

[Parazine]

Yep, that's the "Hour Glass" box, so named because the worm is a complex machined piece that keeps the backlash constant throughout the travel and is shaped like an egg-timer. Fitted from October 1936 at chassis 257866 until the end of production (256501 for export models). 

The ones I've seen break were all cracked and broken at the thinnest part of the arm, immediately behind the boss, carrying the ball joint connection to the draglink. Clean the paint off and have a good look, awkward I know. May be worth investing in a penetrant dye crack detection kit (3 aerosols).

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Here in fact:


  Ruby SBox.jpg (Size: 136.13 KB / Downloads: 145)

[Dennis Nicholas]

I wonder if there will ever be any new worms and 2 tooth sectors made???  I cant be the only one that could realy do with replacements.  The new ones could be made with the thrusts being fully detachable....inner race a push fit onto the worm having a protruding shoulder each end.

[Jeff Taylor]

Dennis,

Clearly someone is still capable of manufacturing steering worms as new ones in a selection of ratios were availble for both early and 'T' Type MG's from Sports & Vintage Motors Ltd of Prees in Shropshire. I think they were selling them for around £250 to £300 each? Of course MG 'T' Type's and Morris 8's use Bishop Cam steering boxes, so somewhat different from Austin 7 boxes.

It's possible Leek Gears of Leek in Staffordshire may be able to manufacture these, but I'd imagine the cost would be extremely high even for a short run.

https://leekgears.co.uk

[Graham Barker]

Thanks, Parazine for the guidance. Looks like it is only half of an egg-timer, but I will run with your recommendation. Not looking forward to checking for the crack or for removing the arm. Does the arm come away from the shaft easily ? Not much space to work in.
Regards 
Graham.