11 replies to this topic

[Bob Riebe]

https://macsmotorcit...-1949-chrysler/

 

 

 

Another logical system that came and went.

It reminds me of the stock-car racing DRISK brake developed fifty years ago that came and went and the Campagnola V disk from GP motorcycle racing around the same time.

[Greg Locock]

Grabbiness is an inherent risk in any positive feedback (self energising) braking system. Decent surface area for cooling, all the guts are protected from dust and gravel. Part count is high.

[gruntguru]

Possibly the greatest attribute of the disc brake is the actual friction surface is exposed to the cooling medium.

[Magoo]

The same company still makes a similar sort of brake for off-road, extreme-duty stuff. Here's one special application, an oil-cooled multiplate brake for the Toyota Land Cruiser in underground mining. 

 

 

Edited by Magoo, 05 April 2023 - 16:20.

[desmo]

The first time I changed pads in a disc brake system after having replaced shoes inside a drum, I wondered why drum brakes ever existed.

[Greg Locock]

I think they were initially popular because they are self energizing so they don't need a booster. There may also have been an issue with designing leakproof hydraulics back in the day.

[10kDA]

The first time I changed pads in a disc brake system after having replaced shoes inside a drum, I wondered why drum brakes ever existed.

They started as cable- and/or lever-operated designs which started off as pretty easy to be made to work effectively with low energy to dissipate, until they couldn't.

[10kDA]

WWII-era aircraft brakes had a similar feature in that the friction pads are arranged around the circumference to bear on the entire disk surface instead of a small caliper-pad configuration such as on ground vehicle and light aircraft disk brakes. Often they are stacked up like multiple disk motorcycle clutches, with the wheels themselves acting as the clutch basket. This design is still in almost universal use on airliners and other heavy, fast aircraft. Old-timer aircraft mechanics who work on both heavy and light aircraft call light aircraft brakes "spot brakes" to differentiate them from the "disk brakes" which have full disk contact areas.

[desmo]

It's a great design if you have plenty of time for the heat to dissipate before they are needed again.

[gruntguru]

The design has absolutely lousy heat dissipation. Most of the braking energy is stored in the rotor/stator pack which needs to have sufficient thermal mass to store all of the energy for a single landing event without loss of mu due to exceeding the temperature limit of the friction material. I suppose (hope) they are designed for worst case - fully loaded, fully fueled aircraft landing with no flaps and no thrust reversers. (Unlikely when you think a about it. Probably requires several times the usual braking energy.)

Edited by gruntguru, 27 April 2023 - 21:58.

[gruntguru]

Found this. https://www.highskyf...on_Requirements

Aircraft Brakes Certification Requirements

Many certification requirements govern the approval, replacement, and modification of aircraft brakes. In general, it is required that the braking system of an aircraft must have the ability to stop the aircraft at maximum certified takeoff weight with the rejected takeoff initiated at decision speed. 

The certification process must be done with all brakes worn to near their service limit (nominally 10% left on the lifespan). Also, the brake and wheel heat sink must be robust enough that no intervention in terms of fire fighting or artificial cooling is required for 5 minutes after the aircraft has been stopped.

Other certification requirements demand that the components of the wheels, brakes, and braking systems should be designed to:

• Withstand all pressures and loads, applied separately and in conjunction, to which they may be subjected in all operating conditions for which the airplane is certificated.
• Accommodate simultaneous applications of normal and emergency braking functions, except other appropriate design measures have been taken to prevent such a contingency.
• Satisfy all the requirements pertaining to energy absorption requirements without making use of secondary cooling devices (e.g. cooling fans, etc).

[cbo]

https://macsmotorcit...-1949-chrysler/

Another logical system that came and went.

A similar system was used on German Panther and Tiger tanks 1942-1945.