Women

[Gareth's was W7 now W10 Downstairs Computer]

The same is true for compressed air brakes, with the Triple Valve.

[Steve Walker]

They have a vacuum pump fitted so a standard brake servo can still be fitted - admittedly that will still generate vacuum no matter what the engine is doing ... assuming that it is running!

SteveW

[Steve Walker]

Your car handbook tells you about disabling the airbag.

SteveW

[The Natural Philosopher]

aren't air brakes the same? the pressure keeps the brakes OFF?

[The Natural Philosopher]

cars designed for power steering are almost impossible to drive if it fails.

[Steve Walker]

I don't think so. Air from a reservoir on each vehicle applies the brakes, while changes in the pressure in the brake pipe control them. Using the brakes on and off and on again too rapidly can actually deplete the air and lose braking - two pipe systems are less prone to this.

The hose breaking does cause the valves on each vehicle to apply braking though.

SteveW

[Dave Liquorice]

down.

Flatlander:

https://www.google.com/maps/@54.9302642,-2.3056601,3a,75y,216.5h,84.35t/data=!3m6!1e1!3m4!1spEKxtUv2eVdnH926J9plLw!2e0!7i13312!8i6656

And a bit further on:

https://www.google.com/maps/@54.9288659,-2.3114255,3a,75y,223.76h,79.06t/data=!3m6!1e1!3m4!1sFZvxd_exsJMjMGL-DjCV4Q!2e0!7i13312!8i6656

Or:

https://www.google.com/maps/@54.7834987,-2.313728,3a,75y,271.51h,84.61t/data=!3m6!1e1!3m4!1sTSbI1L_zwwHm4cAadLqa5g!2e0!7i13312!8i6656

You'll be saying there are no escape lanes next:

https://www.google.com/maps/@54.9302481,-2.7416036,3a,75y,294.31h,87.89t/data=!3m6!1e1!3m4!1sRYzR-OZa9tBpA4SlknEsmQ!2e0!7i13312!8i6656

Assuming the car isn't wrapped around a tree because the brakes faded. Just another ploy to slow people down, you can approach bends much faster using the brakes and gears to dump the kinetic energy of the vehicle.

[Dave Liquorice]

+1

Could well be for all I know, just seen the term mentioned in car brochures. B-)

[Graeme]

In message <qgl2su$g6p$ [e-mail]>, Andrew [e-mail] writes

'Low Gear for 2 Miles' on the A93, leaving Glenshee.

[dennis]

No, some designer didn't think of holding the brakes off with pressure so they have loads of reservoirs to store energy as compressed air to apply the brakes.

The old westinghouse system uses two pipe one to provide pressure and one to release it.

The UK started using an electrically controlled system in the 50s' IIRC and an improved version in the 70s'.

Why they go to such complications to make them "fail safe" is a mystery to me. Lkie I said just use the pressure to hold the brakes off and if the pressure goes the brakes apply.

I wonder what stops them rolling downhill when they are left overnight without the compressor running? They must have another mechanical brake.

[Gareth's was W7 now W10 Downstairs Computer]

That very scenario was illustrated in a TV programme, possibly Destroyed In Seconds.

ISTR USA train stopped overnight on a slight gradient, pressure slowly disappeared, train rolled into urban area with a large conflagration resulting.

[Andrew]

Naa.Standing up on the middle of the leather front bench seat of a vauxhall victor FA.

[dennis]

That's the trouble with fail safe systems that aren't fail safe.

If it needs energy to be applied continuously to work it is not fail safe.

[Max Demian]

That would need a *very* strong spring, probably impracticable. Compressed air can apply a very large force, only limited by the strength of the pipes.

[dennis]

They can be very strong.

[Steve Walker]

It was a 101 Super when I was a young child. FVM945D IIRC - 1966, same year as me - but it was the '70s when we had it.

Originally with 3-speed column shift, but changed to 4-speed stick shift for better towing ability.

SteveW

[Steve Walker]

I'm not sure of that either. Although I suppose that air applied brakes mean that by releasing the air, a vehicle can be shunted by a loco with a non-compatible braking system if necessary. Air-release brakes would leak on while parked up.

Also passenger and freight vehicles apparently require different pressure in the brake pipe, but presumably can still have the same (higher than brake pipe) pressure in the reservoir pipe for fast replenishing.

Freight vehicles, locos, DMUs and EMUs certainly have handbrakes - I presume that coaches do too ... certainly the coach in a rake with a brake compartment will.

SteveW

[dennis]

So the difference would be that they have to release the mechanical brake and shunt and apply the mechanical brake for one operated by air pressure and they would have to release the brake, shunt and reapply the brake on the other. Sounds the same to me.

Poor design specs then.

They do have manually applied brakes, you can see the hand wheel used to do it. They have to remember to do it and on enough trucks/coaches for it to work. The alternative is to have all the brakes apply themselves when you release the air pressure and go along and wind the brakes off if you want it to roll without the engine or if its faulty with the engine.

I think I know which is better.

[tabbypurr]

The above doesn't say a single thing about how I drive. You really should get a brain.

NT

[tabbypurr]

they can be designed to, though I've never seen it.