master cylinder/pushrod

[George Arber]

Can any fellow inmate assist ? According to the TC Bible (p 114 Michael Sherrel ) , by adjusting the brake master cylinder relative to the brake pedal adjusting screw , via the slot in the master cylinder mounting bracket , it should be possible to align the brake pedal adjusting screw close to master cylinder centre line. Perhaps I am taking the diagram on p 114 to literally , but I am finding that with the fixed centre distance of the pivot to the adjusting screw and the minimal vertical adjustment of the master cylinder, I still have what I consider is an unacceptable angle of attack between the adjusting screw and the master cylinder push rod. Maybe I am missing the obvious , but the brake pedal return spring ensures that the pedal returns to the fixed stop resulting in the pedal and adjusting screw being at a fairly acute angle to start with ! Nothing is twisted or out of line , at least as far as I can tell . There is no doubt that the adjusting screw and push rod should be as close as possible to being in line as the brake pedal swings through it's arc . George ......... TC EXU 7548 in England

[m.jablonski@mei.unimelb.edu.au]

George I recently had the same experience, I just adjusted the thing to provide the best average alignment as the piston travels down the bore, i.e., so that the pushrod isn't bearing on the piston sides or the bore edges and so that the pushrod is as close to alignment with the axis of the bore through its travel as I could get. The angles still don't look too good. I haven't got access to Sherrell here, however I seem to remember that, to achieve this, I had to adjust the master cylinder in the opposite direction to that suggested by Sherrell. I think that, with the threaded end closest to alignment with the bore axis, the pushrod rubbed against the bottom of the cylinder bore. I had to lower the master cyl. to prevent this but in turn made the angle between pushrod and threaded end worse. Mark Jablonski Melbourne Australia PS I'd like to add my thoughts of horror and sadness to those expressed by other list members at the recent tragedies in the US. My sympathies to all touched in any way by the events.

--- In mg-tabc@y..., "George Arber" wrote: > Can any fellow inmate assist ? > According to the TC Bible (p 114 Michael Sherrel ) , by adjusting the brake master cylinder relative to the brake pedal adjusting screw , via the slot in the master cylinder mounting bracket , it should be possible to align the brake pedal adjusting screw close to master cylinder centre line. Perhaps I am taking the diagram on p 114 to literally , but I am finding that with the fixed centre distance of the pivot to the adjusting screw and the minimal vertical adjustment of the master cylinder, I still have what I consider is an unacceptable angle of attack between the adjusting screw and the master cylinder push rod. > Maybe I am missing the obvious , but the brake pedal return spring ensures that the pedal returns to the fixed stop resulting in the pedal and adjusting screw being at a fairly acute angle to start with ! Nothing is twisted or out of line , at least as far as I can tell . There is no doubt that the adjusting screw and push rod should be as close as possible to being in line as the brake pedal swings through it's arc . > > George ......... TC EXU 7548 in England

[Eric Worpe]

Hi George, Faced with the same problem of poor alignment between the master cylinder and the push rod, the only way out seemed to involve bending the bracket that supports the master cylinder. I was taken aback by just how easy it was to bend, however I was using an 18inch pipe with a large nut and bolt welded to the end. The bracket was adjusted to give alignment at the point where maximum force would be applied to the brakes. The large nut welded to the pipe allowed the bracket to be clamped in such a way that distortion of the face that the master cylinder bolts on to, was small. Hope this helps, Eric. PS. I'd like to echo Mike Card's thoughts.

[DAI]

George, There are only two variables to adjust - the height of the MC and the pushrod screw length. That is true today as it was 60 years ago. I think three things need to be achieved - full release of the pedal allowing the MC to fully offload, prevent binding of the pushrod in the entrance of the MC, and optimisation of the mechnical efficiency of the mechanism. MC offloading is the critical task, with binding prevention a close second. Mechnical optimisation ensures that the foot loads are best transmitted to the MC and braking system. From Sherrell's book, I think there is a bit of artistic merit in the figure, as the pedal/pushrod angle is fixed by design (pushrod screw into pedal) whereas I believe the figure shows a change in this angle, but either way, it is trying to demonstrate the improvement of the angle. Remember that the pedal return spring (between the pedal and the brake switch bracket) provides the returning force for the pedal (taking the load fully off the pushrod). This leaves the brake shoe return springs, brake cyclinder piston springs and the MC spring to return the MC and braking system to the fully offloaded position. Also, that with the MC piston fully in the offloaded position (internal bleed hole open) and the brake pedal against its mechanisal stop, there is a little slack still in the ball joint (pushrod not under pressure). One can spent some time changing the height and length of the MC and pushrod to achieve all of the above objectives. Regards, DAI --- George Arber george.arber@virgin.net> wrote: > Can any fellow inmate assist ?

> According to the TC Bible (p 114 Michael Sherrel ) > , by adjusting the brake master cylinder relative to > the brake pedal adjusting screw , via the slot in > the master cylinder mounting bracket , it should be > possible to align the brake pedal adjusting screw > close to master cylinder centre line. Perhaps I am > taking the diagram on p 114 to literally , but I am > finding that with the fixed centre distance of the > pivot to the adjusting screw and the minimal > vertical adjustment of the master cylinder, I still > have what I consider is an unacceptable angle of > attack between the adjusting screw and the master > cylinder push rod. > Maybe I am missing the obvious , but the brake pedal > return spring ensures that the pedal returns to the > fixed stop resulting in the pedal and adjusting > screw being at a fairly acute angle to start with ! > Nothing is twisted or out of line , at least as far > as I can tell . There is no doubt that the adjusting > screw and push rod should be as close as possible to > being in line as the brake pedal swings through it's > arc . > > George ......... TC EXU 7548 in England > > >

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[George Arber]

Many thanks to those who replied to my query. It's good to know that I was not missing the obvious . I guess it is a matter of compromise. It is to late for me to 'bend the mounting bracket' as has been suggested , as yesterday I took the old girl to be re-upholstered and with the tub now finished and floor boards fitted I doubt as to whether I could get at the mounting bracket. If anybody is interested in a photo of the car at 75 % complete let me know. Thanks again ...George TC EXU 7548

[Mark Sellick]

George,

The master cylinder pushrod on my TC is also at an incorrect angle according to the diagram in "TCs Forever", and as you say, there is not much scope for adjusting the pedal or the master cylinder itself. When I first noticed this after seeing said diagram, I started having kittens. After taking a step back and thinking it over, I realised that the car has been like this since Dad returned it to the road in '89. If you consider the thrust line of the pushrod on the master cylinder piston as the pedal is depressed, the "angle of attack" improves to being close to a straight line under full braking. If the pushrod and piston line up when at rest, when the pedal is depressed there will be an upward thrust on the master cylinder piston. You need to achieve a compromise. If its not causing trouble, I think its a case of "if it ain't broke, don't fix it". After all, we all check round our cars regularly, don't we???

Mark

TC1459