Simultaneous Application of Gas and Brake Pedals

Matt Whiting wrote:

> Bill Putney wrote:
>
>> wrote:
>>
>>> On Fri, 28 Jan 2005 09:34:09 -0500, MoPar Man > wrote:
>>>
>>>
>>>> Bill Putney wrote:
>>>>
>>>>
>>>>> The downside of power brakes, which is a necessity with disk brakes
>>>>> because they do not have the designed-in mechanical amplification,
>>>>> is that after one or two pumps of the pedal while under throttle,
>>
>>
>>
>>> Just for kicks, I tried on my 94 TransSport 3.8 today. At 40kph, I hit
>>> the brake and the throttle at the same time. Any reduction in speed
>>> would be very hard to measure.On the second application without
>>> lifting the throttle foot the vehicle sped up as I had less boost...
>>
>>
>>
>> Bingo! An experiment that the naysayers refuse to try or don't want
>> to admit the results when they did. Under those conditions, by the
>> second or third pump, most boosted disc brakes are less effective than
>> the typical parking brake at slowing the vehicle down.
>
>
> Why would you pump the brakes if you were trying to stop a car with the
> throttle stuck open?
>
> Matt
>
> P.S. To the owner of the TransSport, better get those brakes fixed.

You can't always explain what a person does in a panic situation - it's
not always a logical though process that stands up to critical analysis
after the fact. Forensics specialists can probably give you lots of
examples of that. I can very easily picture the non-verbal panic
thought process going something like "Damn! I'm pushing as hard as I
can, and it's still moving - maybe I'm pushing on the wrong thing, or my
foots at an angle - I'll take my foot off and jam it as hard as I can
squarely on what I'm pretty sure is the brake pedal!!!" Followed by "Oh
S***!! It's even worse now."

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

"Daniel J. Stern" > wrote in message
>> The reason that they don't have power boost is that (1) there is not
>> adequate vacuum to guarantee boost under all critical conditions
>
> Hydroboost
>
>> (2) The weight penalty of a separate electrically powered vacuum pump is
>> too high
>
> Hydroboost
>

I've done significant driving time in a 1985 Chevy 1-ton pickup equipped
with hydraulic brake boost. If I'm not mistaken, the same pump that
provided power steering also boosted the brakes. It worked -- the pedal
feel was different from that of a typical vacuum-boosted brake system, but
it worked well. If you depressed the pedal down to the floor while at a
stop, you got strange "force feedback" (for the lack of a better term)
through the pedal at the end of the travel.

So yeah, 'hydroboost' is a viable alternative to vacuum-boosted power
brakes.

--Geoff

> I used to drive an International Travelall (similar in size to a Chevy
> Suburban). Unfortunately the mfgr. figured it didn't need power
> steering - but, man, you should have tried to parallel park that thing -
> quit4e a feat even for a teenager. I think there would be similar
> problems selling a modern vehicle with unpowered disk brakes as selling
> ones without power steering just due to human factors.

I'd have paid extra to get my car without power steering, but that wasn't
even an available option. Power steering is great until your engine
stalls in the middle of an intersection; then even a wrestler will have
trouble avoiding a wreck.

Daniel J. Stern wrote:

> On Fri, 28 Jan 2005, Bill Putney wrote:
>
>
>>The reality of modern consumer vehicles that will be driven by
>>quite a range of ages, mental quickness, and physical strength.
>
>
> Right, 'cause women and little old men *never* drove before what you
> arbitrarily consider the "modern" age. Pfft.

Oh - I'm sorry - I thought we were living in the present. How silly of
me to exclude cars from 20 and 30 years ago from the here and now.

>>I used to drive an International Travelall (similar in size to a Chevy
>>Suburban). Unfortunately the mfgr. figured it didn't need power
>>steering
>
>
> No, the original owner decided it didn't need power steering. In any
> event, that's irrelevant to the topic at hand, which deals with *brakes*.

No - it was a poorly designed standard package that also included an AMC
automatic transmission with no external cooling - fluid needed changing
every 20,000 miles - you knew it needed it when the tranny started
slipping. They quit making them for a reason.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

Geoff wrote:

> "Daniel J. Stern" > wrote in message
>
>>>The reason that they don't have power boost is that (1) there is not
>>>adequate vacuum to guarantee boost under all critical conditions
>>
>>Hydroboost
>>
>>
>>>(2) The weight penalty of a separate electrically powered vacuum pump is
>>>too high
>>
>>Hydroboost
>>
>
>
> I've done significant driving time in a 1985 Chevy 1-ton pickup equipped
> with hydraulic brake boost. If I'm not mistaken, the same pump that
> provided power steering also boosted the brakes. It worked -- the pedal
> feel was different from that of a typical vacuum-boosted brake system, but
> it worked well. If you depressed the pedal down to the floor while at a
> stop, you got strange "force feedback" (for the lack of a better term)
> through the pedal at the end of the travel.
>
> So yeah, 'hydroboost' is a viable alternative to vacuum-boosted power
> brakes.
>
> --Geoff

Especially in situations where you have inadequate vacuum to power the
brakes.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

John David Galt wrote:

>> I used to drive an International Travelall (similar in size to a Chevy
>> Suburban). Unfortunately the mfgr. figured it didn't need power
>> steering - but, man, you should have tried to parallel park that thing
>> - quit4e a feat even for a teenager. I think there would be similar
>> problems selling a modern vehicle with unpowered disk brakes as
>> selling ones without power steering just due to human factors.
>
>
> I'd have paid extra to get my car without power steering, but that wasn't
> even an available option. Power steering is great until your engine
> stalls in the middle of an intersection; then even a wrestler will have
> trouble avoiding a wreck.

Heh heh! You wouldn't say that if you drove the vehicle I'm talking
about. Again - picture the size and weight of a Suburban with no power
steering. Perhaps the steering gear could have been geared a little
lower, but parallel parking that thing was a chore and a half (due to
size and lack of power assist both)

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

Bill Putney wrote:

> Daniel J. Stern wrote:
>
>> On Fri, 28 Jan 2005, Bill Putney wrote:
>>
>>
>>> The reality of modern consumer vehicles that will be driven by
>>> quite a range of ages, mental quickness, and physical strength.
>>
>>
>>
>> Right, 'cause women and little old men *never* drove before what you
>> arbitrarily consider the "modern" age. Pfft.
>
>
> Oh - I'm sorry - I thought we were living in the present. How silly of
> me to exclude cars from 20 and 30 years ago from the here and now.
>
>>> I used to drive an International Travelall (similar in size to a Chevy
>>> Suburban). Unfortunately the mfgr. figured it didn't need power
>>> steering
>>
>>
>>
>> No, the original owner decided it didn't need power steering. In any
>> event, that's irrelevant to the topic at hand, which deals with *brakes*.
>
>
> No - it was a poorly designed standard package that also included an AMC
> automatic transmission with no external cooling - fluid needed changing
> every 20,000 miles - you knew it needed it when the tranny started
> slipping. They quit making them for a reason.
>
> Bill Putney
> (To reply by e-mail, replace the last letter of the alphabet in my
> adddress with the letter 'x')

I thought that they used TF727s? or was this an earlier model than the
ones I'm familiar with? (early 70's)

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

On Sat, 29 Jan 2005, Bill Putney wrote:

> >>The reality of modern consumer vehicles that will be driven by quite a
> >>range of ages, mental quickness, and physical strength.

> > Right, 'cause women and little old men *never* drove before what you
> > arbitrarily consider the "modern" age. Pfft.
>
> Oh - I'm sorry - I thought we were living in the present.

Feeling slow again, Putney? Your claim that "modern" consumer vehicles
"...will be driven by quite a range of ages, mental quickness and physical
strength" implies that such was not the case before the "modern" age, and
you're wrong.

> >>I used to drive an International Travelall (similar in size to a Chevy
> >>Suburban). Unfortunately the mfgr. figured it didn't need power
> >>steering

> > No, the original owner decided it didn't need power steering. In any
> > event, that's irrelevant to the topic at hand, which deals with
> > *brakes*.

> No - it was a poorly designed standard package

....which means the original owner didn't order power steering. QED.

On Sat, 29 Jan 2005, Nate Nagel wrote:

> Bill Putney wrote:

>> I used to drive an International Travelall [...] that also included an
>> AMC automatic transmission with no external cooling

> I thought that they used TF727s? or was this an earlier model than the
> ones I'm familiar with? (early 70's)

Putney's remembering things that never existed. AMC bought their
automatics from other makers (GM Hydramatics from the early mid '60s
through '71, Chrysler Torqueflites starting in '72).

"Scott Ehardt" > wrote in message
om...
> > wrote in message
> ...
>> And if it had been front wheel drive?
>
> Isn't more braking power put to the front wheels of a car due to the
> weight distribution properties during stoping? I don't know the ratios,
> though.
>
>> That's the rub with many of todays high powered vehicles. You have
>> antilock brakes that are made as small as they can get away with to
>> keep the weight down (and since they have antilock, it is hard to
>> overwork them anyway)
>
> How do you figure? Antilock does not help with heat tolerance or
> dissipation.

I agree. If anything it would make it worse (assuming locked brakes vs. ABS
stop). If the wheels aren't locked while stopping, all the energy is going
into frictional heat between pads and the rotors. If the wheels are locked,
there is no energy being released as heat in the brakes, they aren't moving,
so it all goes to the tires and the pavement.