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axles compatibility

Does a full girling (rod brakes) Big 7 axle fit on a a ruby chassis? I am building a racing car (in parralel to the trials car) and want the most efficient brakes possible and have a girling braked front axle.


No, it's several inches wider and the torque tube is longer.

The 1938/39 Baby Seven axle will fit and is essentially identical to the Big Seven item apart from being the right size.
Hi David,

I have a special built on chassis 288551 which, if memory serves me right, is from July 1938. I believe it carries the same back axle as that fitted to the Big Seven.
On the face of it you should be able to fit your B7 axle but others more experienced than me may see problems or modifications necessary.
Out of interest I’ve got 15” wheels which makes my car useful for hill climbs, sprints etc . On roads I get along happily at around 4000 rpm plus which equates to around 55/60 mph. Personally I think this is a good trade off as brisk acceleration is more important to me than top speed and makes the car fun to drive.

Interestigly I believe its quite a common mod. I've seen it on a chassis at Keith Rawsons in the past. It had a torque tube mount made further forward, and revised spring mounts. All simple fabrication.
Having a big 7 and a late ruby special with full Girling brakes and a heavy back axle. The big 7 rear axle is wider with a longer torque tube. The spring pins are different, the shaft and bracketry for the Pedal/hand brake are different lengths and the operation of the front brakes would need Ruby Girling units not big 7 cantilever types. To fit a big 7 back axle to a 7 chassis would require remaking new springs for a start. Pete

If you are only fitting the front axle you would need to fabricate new arms back to the ball and a new track arm. The hubs and bearings are larger. Which you might prefer on a racer but they wont match your rears. Pete

Picture of a chassis I put on ebay last year, it sold and the buyer had to pull out due to bereavement. Still for sale if anyone wants it.

The rear spring spacing is the same, although the axle is around 1 1/2 inches wider.

As head suggests you will have to fit a spacer on the pinion.

I guess you are looking to do something similar with the big 7 front axle.

This complete chassis was done with guidance from don rawson.

Unless there's some articulation I can't see, it does look like that front axle has been turned into an incredibly stiff anti roll bar by mounting the radius arm pivots on the side rails.
hi stuart,

there on ball fitting. simular the the track rod ends.
Stuart is right, but I suspect the radius arms are flexible in torsion. Can't tell if the frame is boxed, but if not it will twist too.

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