sdh2903
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| posted on 3/9/16 at 12:50 PM |
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Tandem master cylinder issue
So, I'm currently building a westfield and using their tandem brake master cylinder. After connecting it up and trying the pedal it
didn't feel right, it felt as though it was binding and the pedal didn't return. I checked the clevis wasn't catching on the pedal
all was free and clear.
So I disassembled the cylinder this morning. I have a couple of queries which I'll get to.
Circlip removed and I was expecting the plunger to reveal itself under spring pressure but no it needed a tap then pulling out.
The first seal has a small nick out of it, no sign of the missing bit in the cylinder. Other seal was fine.
Now heres where I am a little confused. According to pictures and other info I've read there should be a second spring at the end of the
plunger? Ie furthest away from pedal end. The part you can see in the pics below, ive pressed in and it's smooth but there's no spring
return? It just stays depressed? Surely this would never work? Or am I being a bit thick?
Due to the nicked seal I will be getting in touch with the factory anyway but I'd like to be sure and not make myself sound like a pleb so any
input gratefully received regarding the non return issue.
Steve
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Dick Axtell
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| posted on 3/9/16 at 07:55 PM |
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quote:
Originally posted by sdh2903
Now heres where I am a little confused. According to pictures and other info I've read there should be a second spring at the end of the
plunger? Ie furthest away from pedal end. The part you can see in the pics below, ive pressed in and it's smooth but there's no spring
return? It just stays depressed? Surely this would never work? Or am I being a bit thick? Steve
A dual-circuit master cyl usally has 2 pistons (or plungers). The example shown in your 3rd pic, is a primary piston, which sits closest to the brake
pedal's input rod.. There should be a secondary piston, which sits at the end of the mcyl bore furthest away from the input rod end.
There should be (has to be) another spring fitted to the end of the secondary piston, in order to return the whole piston train to its
unoperated position.
Was there definitely no such return spring?
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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sdh2903
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| posted on 3/9/16 at 08:07 PM |
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I haven't been able to remove the second plunger. In the pics showing the hollow cylinder you can see the end of the second plunger. I pressed
it with the end of an artist brush and it moved to the end of the cylinder and stopped. No return at all. After tapping it on the bench it moved back
a little. No spring pressure at all.
Every build diagram of a tandem cylinder I've found has a second spring. I will be giving westfield a call Monday.
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