How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
#21
Hi Marek,
Because of what has been written up until now (and constantly referred to) about "hydraulic differentials" and "moving liquid" I had been unable to find anything published that related to the true behaviour and function of the 3.8 linkage, where - had the pivot not been bang in the middle of what is indeed a "no-bias" bar - there would be a bias in favour of one or the other.
The use of "two masters connected directly to the brake pedal" is not a prerequisite for getting a bias.
Otherwise referred to on the 3.8 as the Balance Link Assembly C.20341/C.17244, the "no-bias" bar happens to be symmetrical, but it would be perfectly possible to offset the centre attack point and NOT get 50/50.
If a diagram would help to illustrate this point I would be happy to oblige.
Because of what has been written up until now (and constantly referred to) about "hydraulic differentials" and "moving liquid" I had been unable to find anything published that related to the true behaviour and function of the 3.8 linkage, where - had the pivot not been bang in the middle of what is indeed a "no-bias" bar - there would be a bias in favour of one or the other.
The use of "two masters connected directly to the brake pedal" is not a prerequisite for getting a bias.
Otherwise referred to on the 3.8 as the Balance Link Assembly C.20341/C.17244, the "no-bias" bar happens to be symmetrical, but it would be perfectly possible to offset the centre attack point and NOT get 50/50.
If a diagram would help to illustrate this point I would be happy to oblige.
Last edited by rfs1957 on Sat Dec 10, 2016 6:56 pm, edited 1 time in total.
Rory
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962
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#22
Rory,
Thanks a ton for the dissertation on the difference between upper and lower cylinders. I am rebuilding mine right now and, sure enough, the pistons were reversed. The brakes on my car, 876024, had behaved a bit oddly but I wrote it off as a side-effect of the fat, sticky tires I had on the car. Looking forward to experiencing the difference.
Dave
Thanks a ton for the dissertation on the difference between upper and lower cylinders. I am rebuilding mine right now and, sure enough, the pistons were reversed. The brakes on my car, 876024, had behaved a bit oddly but I wrote it off as a side-effect of the fat, sticky tires I had on the car. Looking forward to experiencing the difference.
Dave
Dave Schinbeckler
'61 E-type OTS
'05 X-type Estate
'88 Ferrari Testarossa
'82 Dodge W-150
'61 E-type OTS
'05 X-type Estate
'88 Ferrari Testarossa
'82 Dodge W-150
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#23 Brakes
Well all I can say is....Brilliant Rory. Makes perfect sense.
Maybe this could be put on the knowledge base? All I need to do now is see just what I have in mine...suspect it won't be what it should be!
Maybe this could be put on the knowledge base? All I need to do now is see just what I have in mine...suspect it won't be what it should be!
Julian the E-type man
1962 FHC
1966 MGB....fab little car too
1962 FHC
1966 MGB....fab little car too
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#24 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
I wasn't able to restore every single picture shown in these posts, but the essential gist is there.
Rory
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962
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#25 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
Has this been whittled down and added to the knowledgebase?.... I could not find it
Phil
1964 S1 3.8 OTS
1964 S1 3.8 OTS
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#26 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
Hi Phil.....as far as im aware its not in the Knowledge base section as a seperate artical......but does it really need to be as all the other posts makes it into a great thread...our whole forum is a knowedge base...however it would need to be pulled together and tidied up into an artical....but just needs someone to do that....then contact the Admin (Heuer) to ask if it could be added....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc
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#27 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
Call me old fashioned but can't we just ignore 99% of this thread and say the purpose of the pivot arrangement is to make the hydraulic pressure in both circuits equal to each other. If it isn't, then the pivot simply pivots about a bit until it is.
kind regards
Marek
kind regards
Marek
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#28 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
The way I think of it is there is a certain amount of lost motion in each circuit (until all pads on all calipers on both circuits are hard up against the discs) the balance link allows the system to find its initial position (and compensates for any differences).
Barrie
Barrie
1968 E-type roadster, 1964 E-type fixed head 1995 Ferrari 355 1980 Ferrari 308 1987 V8 90 Landrover 1988 Bedford rascal van 1943 Ford GPW
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#29 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
Not having a 3.8 my comments may have the same value as a. n. other in a similar position.
But what I can say from reading this thread and from other postings by Rory (rfs1957) in other areas is that he obviously has very high automotive engineering knowledge and experience that he puts to exemplary use by helping to explain to those less knowledgeable how systems work.
I've certainly gained a lot from reading his posts in other areas and benefitted from his generosity to fellow E-Type owners.
Geoff
But what I can say from reading this thread and from other postings by Rory (rfs1957) in other areas is that he obviously has very high automotive engineering knowledge and experience that he puts to exemplary use by helping to explain to those less knowledgeable how systems work.
I've certainly gained a lot from reading his posts in other areas and benefitted from his generosity to fellow E-Type owners.
Geoff
S2 FHC Light Blue
S2 OTS LHD - RHD full restoration
S2 OTS LHD - RHD full restoration
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#30 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
You’re old-fashioned.MarekH wrote: ↑Wed Mar 11, 2020 10:12 amCall me old fashioned but can't we just ignore 99% of this thread and say the purpose of the pivot arrangement is to make the hydraulic pressure in both circuits equal to each other. If it isn't, then the pivot simply pivots about a bit until it is.
kind regards
Marek
HTH
Pete
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas
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#31 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
HTH? - I had to look that up. It sort of proves your point.
I also agree with Barrie - the see-saw is sure to move if the free play is uneven as the pedal is first pressed, then it ought to just float to try keep the line pressure the same, were it to become different for any reason.
kind regards
Marek
I also agree with Barrie - the see-saw is sure to move if the free play is uneven as the pedal is first pressed, then it ought to just float to try keep the line pressure the same, were it to become different for any reason.
kind regards
Marek
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#32 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
Alas that would mean skipping past all the lovely pictures, diagrams, jigs, write up and comments straight to Peter calling you old fashioned.
I can't help thinking the substance of the original thread would be somewhat lost.
Simon
Simon
1969 S2 OTS
1969 S2 OTS
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#33 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
To me the most important part of this thread is the first post which, to me at least, seems well researched and correct. I can't fault Rorys excellent post.
My own view is the Kelsey Hayes system, while maybe not the best, is unfairly maligned by at least some people in the wider jaguar fraternity. Looked after it works perfectly well. The Lockheed system can provide more boost to the pedal making it feel better but that's about it.
My system works well. Although I have fitted coopercraft front callers the rears are standard. As said, and this applies to any servo system, the servo just adds effort to supplement the drivers foot. It means you need less foot pressure but does not intrinsically improve the brake efficiency. That is a product of pad size, pad material, disc material, hydraulic pressure and brake temperature. If the servo fails the brakes "feel" less efficient simply because your foot now has to supply all the brake pressure and also has to overcome the now dead servo....which is entirely possible if you can push hard enough!
Just my thoughts and I do not claim to be an expert...
My own view is the Kelsey Hayes system, while maybe not the best, is unfairly maligned by at least some people in the wider jaguar fraternity. Looked after it works perfectly well. The Lockheed system can provide more boost to the pedal making it feel better but that's about it.
My system works well. Although I have fitted coopercraft front callers the rears are standard. As said, and this applies to any servo system, the servo just adds effort to supplement the drivers foot. It means you need less foot pressure but does not intrinsically improve the brake efficiency. That is a product of pad size, pad material, disc material, hydraulic pressure and brake temperature. If the servo fails the brakes "feel" less efficient simply because your foot now has to supply all the brake pressure and also has to overcome the now dead servo....which is entirely possible if you can push hard enough!
Just my thoughts and I do not claim to be an expert...
Julian the E-type man
1962 FHC
1966 MGB....fab little car too
1962 FHC
1966 MGB....fab little car too
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#34 Re: How 3.8 Brake Master Cylinders Work (Without the Smoke and Mirrors)
Some of the links to the drawings and photographs for this article had evaporated over the years, as someone has just kindly pointed out.
I have re-established them, and if anyone else had been frustrated by this, it's worth taking another look.
I have re-established them, and if anyone else had been frustrated by this, it's worth taking another look.
Rory
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962
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