The following warnings occurred:
Warning [2] Undefined variable $search_thread - Line: 60 - File: showthread.php(1617) : eval()'d code PHP 8.1.27 (Linux)
File Line Function
/inc/class_error.php 153 errorHandler->error
/showthread.php(1617) : eval()'d code 60 errorHandler->error_callback
/showthread.php 1617 eval




Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Girling, Semi-Girling and Brakes
#1
Good afternoon.

I feel like I am asking an obvious question, but: I keep reading about converting the Austin 7 brakes to the semi-Girling type to improve their efficiency. Although I have had a look to find out what the differences are, the articles that I have found only cover making the change: the do not seem to give any explanation of what the differences are.

Could someone either point me to a suitable article or explain how the semi-Girling and Girling brakes differ from other Austin 7 set-up? I assume that my 1935 Ruby will have non-Girling brakes.

Thank you.

Jamie.
Reply
#2
If you hunt thru the online handbooks and parts books and all the club site brake info, and photos, will be able to piece together.
Actually only semi girling; full Girling are rod operated with floating wedge expanders, only fitted to vey late cars and linkages not readily adaptable.
The original brakes are just simple cams, some with very short levers. The only provision for wear is the cam turning further so these are of  large dia with limited leverage. The Girling have cast iron drums, long levers, and the fulcrums are expandable by a square ended adjuster to take up wear, so the cams are smaller with greater leverage. Once set up, the cable lengths do not require adjustment.The thick steel backplates are very different although early hubs/axles can be machined to accept. The line of the cables at the rear differed and substitution may not be straightforward.
As with different levers, mixes are not ideal due the differeing leverages. 

With correct linings and care generally many claim the original brakes OK.....although not my experience! They do condition you for a lifetime of anticipatory driving. On one car when stop lights ahead flashed unexpectedly, I ripped the seat out of the floor!
 
Also various mostly somewhat cruel methods of altering the originals so the shoes “float” with increased bite.
 
In contemporary tests the semi girling achieved about 80% for saloons, which is sufficient although with high pressures and no dive may not seem so to modern drivers.
Reply
#3
Jamie, the much maligned Austin seven brake's need not be as bad as their reputation suggests, the important thing is to remove all wear from the mechanism, all bushes and bearings should be unworn, lubricated and free to move as intended. The shoes should be set so that they are the correct distance from the drums and all cables adjusted equally, most sevens have extensive wear and are not set up particularly well, in this condition they are generally poor. Your car, unless it has been altered, will be fitted with the last of the Austin brakes, the fulcrum is moved out closer to the drum improving contact and they have heavy drums which distort less than the early thin steel drums, in all fairness if you are able to set them up correctly the difference in braking efficiency over semi girling's is negligible. The chief advantage of the semi grilling brakes is that they are more user friendly, they have an adjuster so the shoes can be easily set to compensate for wear, and they have a cam which acts on plungers which open in much the same way as a hydraulic cylinder does thus transmitting an equal force to each shoe. Austin brakes have a direct acting cam, the chief disadvantage is that this causes the two shoes move slightly different amounts and therefor apply one shoe with slightly greater force. To fit semi girling's at the front you would need to replace the whole stub axle assembly complete with the brake set up, at the rear it becomes more complicated as you either have to machine the axle to accept Semi grilling back plates or swap the axle for a later type. One last thing, make sure you fit soft linings, they wear quicker but have greater stopping power.
Black Art Enthusiast
Reply
#4
Bob and Ian.

Thank you both for your detailed replies. I have encountered the types of brakes that you have described, but was unaware what they were called.

The description of what I am likely to find on mine is really helpful.

Thank you.

Jamie.
Reply
#5
While on the topic, those who have driven Morris Minors, A35s, Starlets etc  with 7 inch brakes may wonder why the Seven brakes are so less effective. With hydraulic 200 psi in the pipe applies to all cylinder pistons, whereas say 400 lb in tension is divided  between the cams.  There is also notable friction. A hydraulic or true Girlig leading shoe,  if drawn by braking action into  heavier contact, retains the applied pressure as follow up. With the Seven the cam cannot follow as it is restrained by the other much less effective trailing shoe. The self acting effect with others is normally a source of fade, but this is academic if feeble anyway.  I dunno if anyone has tried with a bare trail shoe!

Most moderns have the shoes free to move endways. You would expect this to cause grab, dragging etc but hundreds of millions cannot be wrong. Some have achieved this with Sevens but most systems are not very workmanlike.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)