Reverse gearbox grinder: 2500M

[prideaux]

griff 200 said:

. That's £1500 is that expensive I'll have to keep my ebay £50 one.

Wow that much you must have had a good week that sad Vixen ?????? is being spoiled
A

[Grantura MKI]

phillpot said:

Grantura MKI said:

Many people tend to forget that the fluid in the brake and clutch needs changing out after a few years,due to the build up of moisture.

True but, in theory at least, moisture just like brake fluid can not be compressed and shouldn't boil in a clutch system.
May just be a "mechanics tale" but when I was a young mechanic was told of a guy had a slave cylinder leak and pee'd in the reservior to get him home!


Reverse in older gearbox's doesn't have synchro and gears are straight cut, hence the whine if you reverse at any speed.

Master cylinders main function to to compress fluids...this is how they work. Moisture in the fluid does not compress and will give you a spongy pedal, may cause pitting to the bores, and will lower the boiling point of the fluid.
Second tale is a myth, unless he was peeing straight Castrol LMA!!!
Regards,
D.

[Renaldo]

Tried "rebuilding" (new seals primarily) a clutch master cylinder in an MG Midget -- I had assumed the cylinder itself was ok.

The rebuild lasted about a month. Turns out the master cylinder was pitted inside from moisture and corrosion.

A lesson learned.

Ron

[Cerberus90]

If it compresses then how do pads get pushed onto the discs?


Isn't the problem with water in lines that when heat builds up, the water boils and leaves air which then gives you the spongy pedal?

Wikipedia said:

[url=http://en.wikipedia.org/wiki/Brake_fluid[source[/url]
It works because liquids are not appreciably compressible

[Grantura MKI]

Cerberus90 said:

If it compresses then how do pads get pushed onto the discs?


Isn't the problem with water in lines that when heat builds up, the water boils and leaves air which then gives you the spongy pedal?

Wikipedia said:

[url=http://en.wikipedia.org/wiki/Brake_fluid[source[/url]
It works because liquids are not appreciably compressible

Pressurized fluid through pedal pressure moves the cups in the calipers on to the pads, then the discs.

Yes, but moisture sits mostly in the cylinder bores, or at the highest point in the system when the vehicle is standing.

Best,
D.

[Grantura MKI]

Renaldo said:

Tried "rebuilding" (new seals primarily) a clutch master cylinder in an MG Midget -- I had assumed the cylinder itself was ok.

The rebuild lasted about a month. Turns out the master cylinder was pitted inside from moisture and corrosion.

A lesson learned.

Ron

Sorry to hear that, Ron. Are you going to sleeve the cylinder?
Best,
D.

[Adrian@]

BUT, this the clutch and as a get you home 'water' would be a basic fluid that would work as long as the seals hold ..there is no heat involved here, no boiling point etc.
Back on topic, what you need to do stall the motion within the drive train, IF you understand that the clutch plate is part of the gear box and fly wheel and cover is part of the engine, two thing have to happen to a noise free change into reverse...the clutch cover should open enough to allow the plate to stop (any drag and it will crunch) and the wheels/differential/prop shaft have to be stopped selecting another gear does the job as other people described.
Adrian@

[Renaldo]

D, ended up installing a new master.

A friend of mine who is much more mechanical than I am, told me he never uses a rebuild kit on its own.

According to him, the cylinder is typically in a bad way, and a rebuild kit by itself is often just a waste.

I imagine he's probably right.

Ron

[prideaux]

Renaldo said:

D, ended up installing a new master.

A friend of mine who is much more mechanical than I am, told me he never uses a rebuild kit on its own.

According to him, the cylinder is typically in a bad way, and a rebuild kit by itself is often just a waste.

I imagine he's probably right.

Ron

You could have that one sleeved in stainless I am told which may be a better long term fix with your weather over there
A

[Renaldo]

Andrew, and what weather might than be? (he asked from behind a 6 foot snow drift)

I'm lying. I actually have a garden -- snow peas. Better eat 'em quick.

Ron

[Grantura MKI]

Adrian@ said:

BUT, this the clutch and as a get you home 'water' would be a basic fluid that would work as long as the seals hold ..there is no heat involved here, no boiling point etc.
Back on topic, what you need to do stall the motion within the drive train, IF you understand that the clutch plate is part of the gear box and fly wheel and cover is part of the engine, two thing have to happen to a noise free change into reverse...the clutch cover should open enough to allow the plate to stop (any drag and it will crunch) and the wheels/differential/prop shaft have to be stopped selecting another gear does the job as other people described.
Adrian@

This is why heavy trucks have a brake fitted to the clutch.
Clutch systems can also fail due to heat...in racing conditions, etc. better safe than sorry.
Best,
D.

[phillpot]

Grantura MKI said:

Master cylinders main function to to compress fluids...this is how they work.

Looks like you've just re-written one of the basic laws of science!

[Grantura MKI]

phillpot said:

Grantura MKI said:

Master cylinders main function to to compress fluids...this is how they work.

Looks like you've just re-written one of the basic laws of science!

Many thanks for sorting me out! I will still to google from now on.

[prideaux]

Grantura MKI said:

phillpot said:

Grantura MKI said:

Master cylinders main function to to compress fluids...this is how they work.

Looks like you've just re-written one of the basic laws of science!

Many thanks for sorting me out! I will still to google from now on.

I think Philpot you will find its not David that re-written basic laws of science even steel compresses as you will read pressure is created from the compression of either liquid or air
A
http://www.physlink.com/education/askexperts/ae15....

Edited by prideaux on Tuesday 19th August 09:40

[phillpot]

prideaux said:

I think Phil Mike you will find......

Of course you can compress steel, it's not a fluid.

Obviously the water at the bottom of the ocean is at greater pressure, the fluid in your brake pipes is at far greater pressure when braking, but it is no more dense, he's wrong

[prideaux]

phillpot said:

Of course you can compress steel, it's not a fluid.

Obviously the water at the bottom of the ocean is at greater pressure, the fluid in your brake pipes is at far greater pressure when braking, but it is no more dense, he's wrong

I give up as Well David he should try Diving down to 40 meters
A

Edited by prideaux on Monday 18th August 22:24

[Cerberus90]

From the AA Book of the Car (1979).

Brakes - Hydraulic brake fluid.

With age and use brake fluid absorbs moisture, mostly through the flexible hoses. A 2-3 percent water content lowers the brake fluids boiling point from 200-220 C to about 140C, thereby causing very spongy brake-pedal response (for the fluid becomes compressible).

Brakes - How the cylinders work togethor.

Pressure to work the hydraulic brakes is generated in the master cylinder. A push-rod, moved by the brake pedal, forces the piston forward. Fluid then flows through the check valve along the pipeline to the brakes. There the pressure moves the pistons of the wheel cylinders. Because pressure from the master cylinder is transmitted equally throughout the hydraulic system, braking pressure on all wheels is equal and simultaneous as long as the fluid remains incompressible.



So two bits there that state the brake fluid is incompressible. Yes, it is under high pressure, but not compressed (not appreciably anyway).

Yes fluids can be compressed, but it requires extremely high pressure to do so.


According to Here.

At a depth of 10 km the pressure would be about 100 million pascals, 1000 bar, and the water would be compressed about 5%. The density would thus be about 5% higher.

[Adrian@]

Oh how jolly..NEXT time I have a chim/griff in with 'clutch' master cylinder failure, I WILL try adding water as a 'get me home' solution...anyone want to take odds on it working.
Adrian@

[Cerberus90]

If the cylinders failed, then no matter what you put in it, it won't work, .

[TVRdaydah]

The step you are missing is the formation of water vapour within the brake fluid. Water vapour is very compressible hence the sponginess. When the fluid heats any water present turns to vapour and the condition worsens. Hence poor or no braking.