Prev: How to Convert a Car to Run on Electricity
Next: 2001 RAv4 cylinder head removal
From: Heron McKeister on 17 Nov 2009 16:25
"hls" <hls(a)nospam.nix> wrote in message
news:DMGdnVZK6rC8KJ_WnZ2dnUVZ_vGdnZ2d(a)giganews.com...
>
> "dsi1" <dsi1(a)spamnet.com> wrote in message news:5eqMm.20048
> > I doubt there's much validity that vacuum assisted brakes were required
> > because of the advent of disk brakes. My first car, a 67 Barracuda had
> > drums and vac boost, as did most cars of the time. That one had a tiny
> > V8 - a 273! Of course, today that would be a large engine - 4.5L. :-)
>
> Power assist brakes, as I said, became luxury items. They were not
> absolutely necessary on drum brake cars, but certainly made braking
> effortless. Finally they found their way onto almost every car.
>
> Disc brakes on large American cars, without power assist, can be monsters.
>
> It is just the way things evolved.

Ah for the days of non integrated proportioning and
metering valves ;^)


From: clare on 17 Nov 2009 18:51
On Mon, 16 Nov 2009 19:09:19 -1000, dsi1 <dsi1(a)spamnet.com> wrote:

>someone(a)some.domain wrote:
>> In article <sJWdnfF9FOHXI5zWnZ2dnUVZ_oKdnZ2d(a)giganews.com>, "hls" <hls(a)nospam.nix> wrote:
>>> "Ray O" <rokigawa(a)NOSPAMtristarassociates.com> wrote in message Before
>>> power assisted brakes were introduced, people
>>>> routinely stopped vehicles by stepping hard on the brake pedal.
>>> That is true, Ray, but also in those days we had front and rear drums, for
>>> the most part.
>>> Discs required a lot more pressure than drums, hence the power assist brakes
>>> became
>>> a necessity rather than just a luxury convenience.
>>>
>>>
>> i wonder about that. i don't think bikes are much different. it tales a lot
>> more pressure to stop my 650 triumph with a doubling leading shoe front than
>> a xt 750 jamaha, which had one disc front and weighs more.
>
>I doubt there's much validity that vacuum assisted brakes were required
>because of the advent of disk brakes. My first car, a 67 Barracuda had
>drums and vac boost, as did most cars of the time. That one had a tiny
>V8 - a 273! Of course, today that would be a large engine - 4.5L. :-)

Disk brake calipers contain more fluid than drum brake cyls, and
require more fluid movement at higher pressure to provide the same
braking force, generally speaking. Therefore, disk brakes derive a
much grater advantage from power assist than servo type (like Bendix)
drum brakes. It allows you to get good braking pressure without
extreme pedal travel.

Non Servo drum brakes like the old Chrysler Center Plane, girling
twinleading shoe, and GM Huck brake systems would have benefited
highly from power assist as well -and GENERALLY required either more
pedal pressure or longer pedal travel than the more common, recently,
Bendix style "self energizing" or "servo" brakes.
From: clare on 17 Nov 2009 18:53
On Tue, 17 Nov 2009 15:25:40 -0600, "Heron McKeister" <not(a)home.com>
wrote:

>"hls" <hls(a)nospam.nix> wrote in message
>news:DMGdnVZK6rC8KJ_WnZ2dnUVZ_vGdnZ2d(a)giganews.com...
>>
>> "dsi1" <dsi1(a)spamnet.com> wrote in message news:5eqMm.20048
>> > I doubt there's much validity that vacuum assisted brakes were required
>> > because of the advent of disk brakes. My first car, a 67 Barracuda had
>> > drums and vac boost, as did most cars of the time. That one had a tiny
>> > V8 - a 273! Of course, today that would be a large engine - 4.5L. :-)
>>
>> Power assist brakes, as I said, became luxury items. They were not
>> absolutely necessary on drum brake cars, but certainly made braking
>> effortless. Finally they found their way onto almost every car.
>>
>> Disc brakes on large American cars, without power assist, can be monsters.
>>
>> It is just the way things evolved.
>
>Ah for the days of non integrated proportioning and
>metering valves ;^)
>
Oh for the days of cable and rod actuated brakes, with mechanical
brake force distribution -via different length bellcranks.
From: dsi1 on 17 Nov 2009 20:14
clare(a)snyder.on.ca wrote:
>>
> Disk brake calipers contain more fluid than drum brake cyls, and
> require more fluid movement at higher pressure to provide the same
> braking force, generally speaking. Therefore, disk brakes derive a
> much grater advantage from power assist than servo type (like Bendix)
> drum brakes. It allows you to get good braking pressure without
> extreme pedal travel.

I'm familiar with basic hydraulics but the fact remains that brakes used
the same system of vacuum assist before disks became popular. It doesn't
matter which system gets more benefit from power assist because the
truth is that both drums and disks pretty much suck without it.

>
> Non Servo drum brakes like the old Chrysler Center Plane, girling
> twinleading shoe, and GM Huck brake systems would have benefited
> highly from power assist as well -and GENERALLY required either more
> pedal pressure or longer pedal travel than the more common, recently,
> Bendix style "self energizing" or "servo" brakes.
From: Anyolmouse on 17 Nov 2009 18:13

"Heron McKeister" <not(a)home.com> wrote in message
news:QwEMm.17416$ET3.8075(a)newsfe17.iad...
> "hls" <hls(a)nospam.nix> wrote in message
> news:DMGdnVZK6rC8KJ_WnZ2dnUVZ_vGdnZ2d(a)giganews.com...
> >
> > "dsi1" <dsi1(a)spamnet.com> wrote in message news:5eqMm.20048
> > > I doubt there's much validity that vacuum assisted brakes were
required
> > > because of the advent of disk brakes. My first car, a 67 Barracuda
had
> > > drums and vac boost, as did most cars of the time. That one had a
tiny
> > > V8 - a 273! Of course, today that would be a large engine - 4.5L.
:-)
> >
> > Power assist brakes, as I said, became luxury items. They were not
> > absolutely necessary on drum brake cars, but certainly made braking
> > effortless. Finally they found their way onto almost every car.
> >
> > Disc brakes on large American cars, without power assist, can be
monsters.
> >
> > It is just the way things evolved.
>
> Ah for the days of non integrated proportioning and
> metering valves ;^)
>
>

I kind of miss my 1937 Tudor Ford Fastback with mechanical brakes. It
took about as long to go from 60 to 0 as it did from 0 to 60 with the
V-60 engine. <Grin>

--
A man is known by the company he keeps- Unknown

Anyolmouse

First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4
Prev: How to Convert a Car to Run on Electricity
Next: 2001 RAv4 cylinder head removal