Two types of Girling rear brakes?

[dchw1975]

Hi,

Whilst overhauling a Girling braked rear axle I have come across a difference that I want to check with others. Firstly the axle itself came with ball end levers and the setup such that the adjuster was at the top of the backplate and the lever at the bottom. The lever at rest sat at about 10 degrees back from the vertical as you would expect. When I checked to make sure that they were round the correct way etc I found on the A7CA digital archive the following picture, http://archive.a7ca.org/collections/tech...tem/TD0010 which show both the backplates rotated by 90degrees and a different type of lever which require a fork on the cable end. So this wouldn't be an issue but I bought some replacement brake cams (originals badly worn) and when they arrived it would appear that the flats for the cotter are in a different position from the originals I removed. Upon investigation, it would appear that they are in possibly the correct position for the fork end levers, not the ball end...? So my question is is it just a case that there was a short period during which ball end levers went on Girling back axles before they switched over to 'fork end' levers and rotated the backplates? Therefore there would actually be two different types of girling brake cam needed???

regards

David

[Howard Wright]

Hi David

Very late cars had rod brakes rather than cables.  What year is your car? I think rod brakes came in around 1938?

Cheers

Howard

[dchw1975]

Hi Howard,
This is definitely an axle from an earlier car than the very late rod braked system. What I did notice though is that the drawing in Woodrow of the rear Girling brake setup in the HUbs and BRakes section does show the levers at the bottom of the backplate, unlike the A7CA drawing...?

David

[Howard Wright]

Hi David

Closer examination of the drawing does seem to show a vertical actuation rather than horizontal action of the cam.  That is the lever needs to be pulled upwards rather than in along the length of the car. Almost indicates some form of Bowden operation.

Very strange.  Could it be possible that the drawing is a prototype drawing that never saw production?  I’ve looked up the operation of rod brakes on the Big 7 (Cornwall site) and they have a completely different actuating mechanism that doesn’t involve a twisting cam.

I’m sure someone with more knowledge will come up with an explanation 

Cheers

Howard

[dchw1975]

Hi Howard,

I think the drawing is just a really strange orientation with the view from the back turned itself through 90deg as it does show the spring mounting pin as horizontal.

The bottom left drawing from directly above has the lever at the back.

David

[John Cornforth]

Hi

From mid 1935 the last iteration of "offset pivot" Austin brakes used fork end levers 1A7196 at the rear which were 2 1/4 inches long.

These were followed in mid 1936 by the semi girling setup with similar length fork end levers 1A7262, having a recess for a felt on the inner face. 

Later, in mid 1938 the rears went to full girling with plungers and rods, the front remaining semi girling.

I'm not aware of any semi girling setup with ball end levers as standard at the rear. I suspect the reason for adopting fork ends was to give enough sideways clearance, unlike the front no ball is needed to accommodate steering motion.

As far as rear backplate orientation is concerened, I believe the original semi girling setup (for the low chassis Ruby etc) has the adjusters above the axle tubes and towards the front of the car, whereas the actuator cams are below the axle line and towards the rear of the car. The levers point downwards, slightly to the rear when off and near vertical with brakes full on. Figure H-13 in Woodrow is misleading, as it implies the adjuster is at the top.

The problem you might have is that the backplates are held on with 4 screws, which gives one correct position and 3 incorrect ones.  Cams etc can also be inadvertently swapped from side to side and front to rear. The absence of good drawings or photos in the past may be the reason for the variety of setups which are encountered "in the field".

As with all these things, I'm ready to be corrected if an expert pops up with better information !

[Nick Lettington]

If you want another example of a strangely drawn detail in the archive, look no further than the Ruby steering column which indicates that the trafficator switch is at the bottom...

[Bob Culver]

As above the actuator for the plain lever is mounted behind the axle and just below the centre line, with the lever down. When fitting to high chassis car the routing of the brake cable is very steep; something approximating the original can be acheived by selecting a cam and fitting lever upward. Possibly other variants have been adopted for low specials. Are there 2 or 4 cam types total? Many dwgs are confusing as dwg convention makes them appear rotated at a glance.

[AustinWood]

If this is a Girling axle the backplate can be rotated by 90 degrees to put the cams in the correct position.

[Bob Culver]

It may be of interest, but the British dwg convention of the time depicted each view projected behind the object. This makes the backplates seem wrong relative to the bottom of page.
A year or few ago there was extensive discussion on the topic of Girlings on non original cars. I found it necessary on my RP to face the levers up but others seems to have succeeded with them down as originally. The keen might redrill the backplates to acheive an optimum.