maintenance

[Parazine]

Andy and Jeff make a very valid Point - ‘almost’ everything on a Big Seven is different compared to a Seven.

Ruairidh, I think you've been listening to your father, who I can remember making a pronouncement at a Bristol Club debate in the 'seventies, "that the only thing that is the same on a Big 7 and a Chummy is the wheelnuts!".

After owning a Big 7 for a number of years, I wrote an article, which is yet to be published and one section deals with the parts interchangeabilty thus:

While the Big 7 has the same design philosophy as the Ruby, relatively few components are directly interchangeable. Hubs and many brake parts are the same as a late Ruby and most trim parts are either the same or close enough to be used. Some gearbox parts are the same and smaller pieces inside the back axle, together with the bearings can be swapped. Crown wheel and pinion is the same design but larger (longer pinion) and the half shafts are also similar but longer (wider axle). Front axle is unique and both front and back axle use screwed spring pin and shackle bushes, familiar to those of us who have worked on the suspension of the Austin A30 and its derivatives. These pins and bushes corrode and wear badly. They are currently unobtainable.
Some new spares are sporadically made but there are no new engine parts in production at all. There have been a number of gasket, piston and bearing sets that have appeared on eBay recently, probably due to the sale and resale of the Kirby Whiske parts.
Girling brake linings are the same as the Ruby type and can be obtained from our cherished suppliers while wheel bearings are the same as a Ruby. Some other spares are available, either new or second hand from the Big 7 Registrar.
Second hand or NOS spares appear from time to time, usually at inflated prices (rare car innit mate??) but seldom seem to sell (after all it’s a rare car isn’t it?).

Oh, the wheel nuts. I’m afraid they are a special pattern, unique to the Big 7. They aren’t the same as the Ruby or even a Chummy……….

[Ian Williams]

Good article but in my experience the Hub outers are not interchangeable as; A, there is a register to locate the drum not present on a Ruby Hub, and B, the internal taper on a Big Seven Rear Hub differs from that on a Ruby. As you say there are however lots of similarities in the general design, brake shoes adjusters are same as semi grilling and the actuators and some of the rod system are as you say shared with the very last of the Rubys. Internal design of the steering column is identical to a Ruby, but the length differs as does the mounting, a big Seven front axle assembly will bolt straight onto an austin seven chassis, but the track is slightly wider, the list goes on depending how much we want to drill down into detail. In my opinion the main area where traditional Seven thinking will be wrong is the engine, but that will be far more familiar to the uninitiated than a normal seven unit.

[Ruairidh Dunford]

Thanks Tim.

Tell me more about the wheel nuts please.

[Erich]

Andy and Jeff, what is the barrel shaped thing on the engine top front? If it's the dynamo, it is the wrong way 'round. ;-)
Being relatively new to Sevens and perusing original manuals, I have found some of the older books a bit lacking compared to more modern publications. I'll note that those original manuals were written when the cars were new, and therefore major work was not usually required. For instance, checking the steering arm for cracks would not have been included in periodic maintenance. I have a couple of period Velocette manuals which give good information, but obviously assume a good deal of experience with engines and gearboxes, leaving a newbie "wrench"(mechanic) with a lot of head scratching.

Erich in Seattle

[Ian Williams]

Thank you Ruairidh, I am sure Tim is very well versed in Late Ruby and Big seven matters, his article come across as such. As owner quite a lot of big seven stuff, and of A/RR Ruby chassis number 286999 I am also pretty well versed in such matters so was providing some further insight. I do not however profess to have any real expertise with Big seven engines as they have never really interested me in any way.

[Ruairidh Dunford]

I appear to be caught in the crossfire again. I have removed my extended comment, as it has been misinterpreted, apologies.

[Parazine]

Thanks Tim.

Tell me more about the wheel nuts please.

Well Ruairidh, they're kind of brassy round things 

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Thanks Tim.

Tell me more about the wheel nuts please.

Well Ruairidh, they're kind of brassy round things 

[Bob Culver]

The Big Seven engine is an intriguing contrast with the last 3 bearing Seven. The golden rule for a robust multi main bearing engine is that every main bearing must be rigidly supported.  The last Seven had the centre bearing very vaguely and flexibility dangling from a flimsy crankcase. With  no counterbalancing on the crank bearing loads at revs would have been high. The cars were notorious for broken cranks long before it was recognised as a Seven problem generally. The Big Seven is the other extreme. It has rigid one piece iron block/crankcase with the main bearing caps securely keyed in like a thoroughbred racer. And it has a crank with counterweights (a refinement omitted on the Eight).

[Ruairidh Dunford]

If they are truly round Tim then yes, quite different!