Rear Spring Cambers and Leaves

[Graham Beckett]

In the recent PWA7C reprint of the Companion Page 80 has been amended.
It is available from the Club Bookshop at £18 inc P & P.

[Hedd_Jones]

I have two copies at present Graham, I'm not sure I want a third!.

However, I picked fathers copy up, seems to have been annotated.

The camber as noted seems to be pretty close to what I measured on my mystery springs yesterday, and by my lower photo therefore pretty close to what Ian sets them at.

Trouble is still says that they should have 7 leaves (for my 1928 car).

My guess is that the leaf thickness varied with model also, given this is one of the drivers of stiffness.

I will get the calipers out on the chummy, cup RL and RP and take a view, a chummy being considerably lighter than the RP.

Looks like I'm going to have to put my finger in the air, see which way the wind is blowing and take a view on them.

Anyone with anything to contribute please do, I am unlikely to do anything to the car until they start putting salt on the road.

[Steve Jones]

As I understand it, imperial thickness spring steel for use in spring leaves as original is now unobtainable and metric thicknesses are all that's available. Inevitably, this means that the number of leaves in a modern spring can be different to the number originally. It's the dimensions of the finished springs and spring rates that matter, not the number of leaves.

Steve

[Hedd_Jones]

That is certainly true steve, I've just had 2 new springs made for the safety valve for my steam roller. They had to grind some 8mm square spring steel down to 1/4 for them.

They seem to have worked perfectly however. Boiler test on the 26th.

[JonE]

a note from my annotated page 80... not sure form what sources tho
1923..... 5 leaves
SWB max 6", LWB highframe max 6.5"
low frame max 3.5"
sports max 2.5"

[Tony Press]

a note from my annotated page 80... not sure form what sources tho
1923..... 5 leaves
SWB max 6", LWB highframe max 6.5"
low frame max 3.5"
sports max 2.5"

Possibly either from Bill Sheehans "Important Correction" in 1974 or "Important Correction"  in 2010.  

I have a copy of both filed in my Austin Seven Companion  page 80 

[Ian Williams]

I am not sure that anyone can definitely state, x year = x number of leaves, I have found numerous variations in number of leaves, thickness of leaves including a variation of leaf thicknesses in a single spring. It seems to me it would stand to reason that a heavy saloon would have a higher rate spring than say a lighter Chummy even if they are set to the same camber. Therefore a Saloon spring on a Chummy will settle less than a spring with the right rate fitted to said Chummy and consequently affect the ride height.

[squeak]

Bill got those measurements many many years ago from the notebook of an old time spring maker in Melbourne, I believe

[Dennis Nicholas]

The modern disease....one must say what make/model car for a spare part.  If only we could have dimensions (where possible) then things would be simpler.
Did you know Ford made an Austin 7 part in their 4 wheel drive Sierra?
Front drive shaft flange is same as A7 pinion shaft flange, if I remember someone pointing out?

I have seen the formula for flat spring rates (the amount they flex for given dimensions and spring steel types) but when getting a front spring for a big 7 front axle on my Nippy gave up trying to work it all out, even using the dimensions of the new spring I had made (standard?) big 7 spring from what seems to be the only spring commercial manufacturer left.  I have given in and am relying on the "well it all seemed to be ok with the old spring size".  The BMC A+ engine is heavier than the A7 engine but then the big 7 spring is stronger than the 7 spring
I have had no such problems with the coil springs for my Austin's distant relative the Reliant Scimitar.


Here is what Bill sent out...don't know date.

   

Dennis

[Hedd_Jones]

So to bottom this out, there has been considerable assistance given on Facebook, in addition to what's on here

From info here, it looks like the 6inch of camber (measured to pin centreline) on my springs is the maximum quoted by Bill, slightly less than the maximum my father noted in his companion.

From Facebook, Anne Williamson I have this info. From a Remax Catalogue



So whilst I accept fully that is doesn't quote leaf thickness, it seems 6 leaf rear is entirely appropriate for a 1928 chummy.

Looks like its worth the effort of trying them.

Many thanks all who commented.