| Re: Drum brakes [message #329050 is a reply to message #329003] |
Sun, 11 February 2018 09:20   |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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80,000 pound GVW Tractor trailer rigs seem to still be using those " horrible" drum brake things just fine.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Drum brakes [message #329051 is a reply to message #329050] |
Sun, 11 February 2018 10:31 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Yes but they don't have weenie-a$$ ways to apply the stopping forces. They
use air pressure, a lot of it. And what do you think those runaway sand
traps on steep downgrades are there for? As well as the brake check areas
at the summits?
Brake linings are a consumable product. They need constant
maintenance. That is another advantage of disc brakes. Ease of inspection
and maintenence.
PACCAR, a European company that owns Kenworth trucks, among other
brands, has a technology and development center in LaConner, Washington.
They develop products for the trucking industry, including brakes. We (the
GMC CASCADERS) had the rare opportunity to visit the center last year. Lots
of stuff coming down the pike on brakes. Including automatic application
via computer controls when weary drivers approach corners too fast, and
breach summits with too much speed, etc. They have a shaker table there big
enough to hold a fully loaded Semi truck and 55 foot trailer for testing.
High tech stuff for sure.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Feb 11, 2018 7:21 AM, "John R. Lebetski" wrote:
> 80,000 pound GVW Tractor trailer rigs seem to still be using those "
> horrible" drum brake things just fine.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
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| Re: Drum brakes [message #329619 is a reply to message #329003] |
Sat, 03 March 2018 21:45 |
rickmike
Messages: 252
Registered: September 2011
Location: United States
Karma: 0
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Senior Member |
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To answer the question as to whether wider brake shoes are an improvement, let's give a real engineering answer.
As JimK stated, The braking force is proportional to the applied force supplied by the wheel cylinder. (We won't go into the self energizing feature of the brake shoe arrangement.)
F(braking) = u(coefficient of friction) F(hydraulic)
Contrary to the stiletto heels vs large heels idea, the force per surface area of the shoe has nothing to do with the actual braking force. (check any Physics book on friction)
The wider shoes do improve braking in the respect that the braking heat is distributed over a larger area thus reducing the temperature rise of the surfaces. Coefficient of friction falls as temperature rises, we call it brake fade. Wear is also reduced due to the reduced temperature.
So there IS a benefit to the wider shoes. Granted, the difference may not be significant to total shoe life nor noticeable to driver as less brake heat fade. Thus GM engineers chose the smaller(cheaper) shoes.
Let's not perpetuate the false idea of force per area as a factor in the braking force. This is true on the hydraulic side of the braking system but not the friction shoes/pads side.
Rick M.
1974 26' Canyonlands
aka "The General"
Clinton, TN
[Updated on: Sat, 03 March 2018 23:24] Report message to a moderator |
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