Clutch lightening Servo - BEWARE
Discussion
I followed this prior topic with interest and having a competition clutch and being an "old codger", decided the remote clutch servo was a good idea. Bought the MGB 1.65 servo and carefully installed where the the screen washer sits (It is a Griff 500 and too big for where the carbon canister fits)
I replaced the master cylinder seals, replaced the slave (pitted), new flrxible hoses, etc. Bled the system, very soft pedal and squishy so pumped the master to feel some pressure. Now, I was aware that there is no "stop limit" with this installation, but managed to completely crack open the clutch fork!! (Only replaced in 2013 due to fulcrum pivot punch hole.) Sh** and Bu**** was all I could say !!
|http://thumbsnap.com/VaE5boPv[/url]
I was all set for a spin this wk-end. Now having split the engine from the bell housing, managed to remove the fork. Next question "Do I limit the movement?" It should not be necessary as nothing physical has changed in the movement ratio's.
The master is 0.7" bore, the slave is 1" bore, so from what I see (A= pi x r squared) that gives a 1:0.5 movement ratio, ie. 1' at master and 1/2 inch at the slave.
Introducing the Servo at 1:65 - not yet sure how to translate that ratio? Being single line remote should be straight through?
The maximum movement at the slave - full-in to full-out appears to be 2" (Hence the damage.)
Any hydraulic experts on here?
Do I put a limiter on the clutch pedal?
Do I have to change bores?
Did I damage during bleeding?
I also note the original pipe was 1/4". The new flexible hose is less. Will this affect the pedal return speed?
Any suggestions welcome.
I replaced the master cylinder seals, replaced the slave (pitted), new flrxible hoses, etc. Bled the system, very soft pedal and squishy so pumped the master to feel some pressure. Now, I was aware that there is no "stop limit" with this installation, but managed to completely crack open the clutch fork!! (Only replaced in 2013 due to fulcrum pivot punch hole.) Sh** and Bu**** was all I could say !!
|http://thumbsnap.com/VaE5boPv[/url]I was all set for a spin this wk-end. Now having split the engine from the bell housing, managed to remove the fork. Next question "Do I limit the movement?" It should not be necessary as nothing physical has changed in the movement ratio's.
The master is 0.7" bore, the slave is 1" bore, so from what I see (A= pi x r squared) that gives a 1:0.5 movement ratio, ie. 1' at master and 1/2 inch at the slave.
Introducing the Servo at 1:65 - not yet sure how to translate that ratio? Being single line remote should be straight through?
The maximum movement at the slave - full-in to full-out appears to be 2" (Hence the damage.)
Any hydraulic experts on here?
Do I put a limiter on the clutch pedal?
Do I have to change bores?
Did I damage during bleeding?
I also note the original pipe was 1/4". The new flexible hose is less. Will this affect the pedal return speed?
Any suggestions welcome.
Edited by DaveG on Sunday 22 January 19:25
Edited by DaveG on Sunday 22 January 19:50
Hi Jazzdude. The competition clutch makes no difference, maybe a bit heavier under pedal. You will not fit the servo where the canister is under the wing - it is too large at least on the Griffith. I removed the canister a few yrs back ( I have MS / ECU etc.) I made up a custom cover plate to replace the one supporting the washer bottle and on which to mount the servo. Yours being a Chimaera, may fit under the wing??
Hi Jazzdude, yes, servo now working. Regards the pipe sizes, the original master-to-slave is 1/4 ins. I have replaced the original pipe with flexible brake hoses, which is what the servo requires. These are 3/16 ins. The consequence of this is probably that the pedal return is 'slowed' a little, otherwise the clutch is smooth and sensitive.
The other changes I had to make were to re-orientate the servo to exactly match the installation instructions (problems with bleeding.) I also found that the return spring in the new slave was much weaker than the original, so I used the original and to better position the slave piston in its cylinder I also added a couple of shims (1/8 ins) to the slave mounts.
Also a note concerning the 'smashed' release fork, I managed to remove and replace this without dropping the gearbox. It would not come out of the inspection hole due to bending of the fork, however by separating the gearbox from the engine (ie release g/b from bell housing) you can slide the gearbox back about 1"ins on the prop shaft. This gives enough room to manouver the fork through the inspection hole. Note also that it is a real pig getting the fork back and aligned and onto the release bearing and correctly sited onto the pivot. (I have done it twice now in 3 years - more than enough!!).
The other changes I had to make were to re-orientate the servo to exactly match the installation instructions (problems with bleeding.) I also found that the return spring in the new slave was much weaker than the original, so I used the original and to better position the slave piston in its cylinder I also added a couple of shims (1/8 ins) to the slave mounts.
Also a note concerning the 'smashed' release fork, I managed to remove and replace this without dropping the gearbox. It would not come out of the inspection hole due to bending of the fork, however by separating the gearbox from the engine (ie release g/b from bell housing) you can slide the gearbox back about 1"ins on the prop shaft. This gives enough room to manouver the fork through the inspection hole. Note also that it is a real pig getting the fork back and aligned and onto the release bearing and correctly sited onto the pivot. (I have done it twice now in 3 years - more than enough!!).
Hi Jazzdude, I do not think you have read the whole thread. I had to split the engine to replace the release fork, previously damaged. You are correctly stating that the brake servo sits inline between the master and the slave. The original pipe (1/4ins) runs between the master and the slave. The servo uses standard brake fittings and 3/16 ins pipe and so I used banjo connectors at the 'block' for the master and also for the slave connection.
I still do not quite understand how I managed to break the release fork, but I did. The clutch movement is determined by the ratio of the bores in the master and the slave and so this should not change. The servo should not change this (1:1) only the force required.
(Note there seems to be quite a few variation of slave in use if you intend changing the slave.)
I still do not quite understand how I managed to break the release fork, but I did. The clutch movement is determined by the ratio of the bores in the master and the slave and so this should not change. The servo should not change this (1:1) only the force required.
(Note there seems to be quite a few variation of slave in use if you intend changing the slave.)
No it was not straightforward. As stated I had to re-orientate the servo as per installation instructions. I initially inclined the servo as per instructions, but had the air inlet facing up. I had trouble bleeding and so re-modified my bracket and mounted servo so the air filter inlet was facing down, as per instructions (ie. less chance of capturing air in fluid).
The original post on here showed an installation with the air up and so I did not worry too much initially. Suggest you abide by instructions.
The original post on here showed an installation with the air up and so I did not worry too much initially. Suggest you abide by instructions.
The installation instructions are here:-
http://tr4a.weebly.com/uploads/2/1/9/8/21980360/re...
Here is a picture of the placement in my Griff.
http://tr4a.weebly.com/uploads/2/1/9/8/21980360/re...
Here is a picture of the placement in my Griff.
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