Simultaneous Application of Gas and Brake Pedals

On Wed, 2 Feb 2005, N8N wrote:

> > I don't like hydroboosts, for the simple reason that it's a doglick,
> > failure-prone, needlessly-complex system that gives rotten pedal feel.

> So how do you feel about Hydrovacs?

No opinion *yet*, haven't driven one.

Daniel J. Stern wrote:
> On Wed, 2 Feb 2005, N8N wrote:
>
> > > I don't like hydroboosts, for the simple reason that it's a
doglick,
> > > failure-prone, needlessly-complex system that gives rotten pedal
feel.
>
> > So how do you feel about Hydrovacs?
>
> No opinion *yet*, haven't driven one.
c'mon down, you can drive my old '56 (bring lots of ATF)

nate

Steve wrote:

> N8N wrote:
>
>>
>>> several (incorrect) assertions made in this thread about "why" disk
>>> brakes "need" power assist does not make it true. Disk brakes do not
>>> "need" power assist any more than drum brakes, whether or not the
>>
>>
>> drum
>>
>>> brakes are of the self-energizing variety.
>>
>>
>>
>> So you're saying that all those years of engineering school and
>> experience actually working as an engineer with automotive braking
>> systems were for naught. The fact that you don't like my explanation
>> doesn't mean it's not true. Discs *do* require more line pressure for
>> a given brake torque than self-energizing drums, assuming similar
>> diameters and normal piston sizes. Simple, indisputable fact.
>>
>> nate
>>
>> (damn, I really hate it when I have to play the "credentials" card, but
>> willfully ignorant people just **** me the f**k off!)
>>
>
> I'll agree to an extent on disks needing more LINE PRESSURE. But there
> are ways to get line pressure without "needing" power assist.
>
> And as for the amount of extra line pressure needed, I think that is
> minimized by the fact that disk calipers typically have a much larger
> piston area than do similar capacity drum brakes, which is part of the
> reason that the drums need to be self-energizing.

I'd say it the other way around. Disk brakes need larger piston area
because they don't have the self-energizing capability. :-)


Matt

On Tue, 01 Feb 2005 20:00:04 -0500, Bill Putney >
wrote:

>Steve wrote:
>
>> Bernard farquart wrote:
>>
>>>
>>> Anyone who thinks International Harvester products were
>>> *under* engineered has no concept of what they are talking about.

I worked for a "corn binder" dealer in the early seventies, and my
impression then and now, was "under engineered and over built". They
were dirt simple, rock solid, butt ugly, almost indestructible, crude,
purpose built machinery.
They were elegent in their simplicity, and if the ultimate test of
engineering is not that nothing more can be added, but rather that
nothing more can be removed, then you could say they were well
engineered.
>>>
>>
>> 100% agreed on that one. The IH 345 is one of the most amazingly tough
>> engines I've ever seen. Pretty comparable overall to the
>> truck/industrial versions of the Mopar big-blocks of the 60s and 70s
>> (the 413 and 361 in particular).
>
>My dad had a whole fleet of their trucks in his mechanical contracting
>business. One small pickup truck had a four cylinder engine. It was
>obvious that they had taken the mold for casting a 304 CI V-8 and
>blocked off one whole side of the mold to create the 4-banger. We used
>to laugh at that.
>
>Bill Putney
>(To reply by e-mail, replace the last letter of the alphabet in my
>adddress with the letter 'x')

Steve wrote:

> N8N wrote:
>
>>
>>> several (incorrect) assertions made in this thread about "why" disk
>>> brakes "need" power assist does not make it true. Disk brakes do not
>>> "need" power assist any more than drum brakes, whether or not the
>>
>>
>> drum
>>
>>> brakes are of the self-energizing variety.
>>
>>
>>
>> So you're saying that all those years of engineering school and
>> experience actually working as an engineer with automotive braking
>> systems were for naught. The fact that you don't like my explanation
>> doesn't mean it's not true. Discs *do* require more line pressure for
>> a given brake torque than self-energizing drums, assuming similar
>> diameters and normal piston sizes. Simple, indisputable fact.
>>
>> nate
>>
>> (damn, I really hate it when I have to play the "credentials" card, but
>> willfully ignorant people just **** me the f**k off!)
>>
>
> I'll agree to an extent on disks needing more LINE PRESSURE. But there
> are ways to get line pressure without "needing" power assist.

But in so doing, as Nate has pointed out, other things are traded off
and design safety margins (for pedal travel, pedal hi point, pedal low
point, etc.) are more compromised.

> And as for the amount of extra line pressure needed, I think that is
> minimized by the fact that disk calipers typically have a much larger
> piston area than do similar capacity drum brakes, which is part of the
> reason that the drums need to be self-energizing.

And the larger caliper piston area multiplies the required pedal travel,
but what saves the disc brakes from that effect is that the
caliper/piston/pads relax (away from the rotor) a lot less than the
shoes relax away from the drum when brakes are off, so that part turns
out to be about a wash.

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

Steve wrote:

> Bill Putney wrote:
>
>> Steve wrote:
>>
>>> Bill Putney wrote:
>>>
>>>> Daniel J. Stern wrote:
>>>>
>>>>> On Fri, 28 Jan 2005, Steve 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,
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Why do people keep saying this?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> The parrot effect, I'm guessing.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> No. The reality of modern consumer vehicles that will be driven by
>>>> quite a range of ages, mental quickness, and physical strength.
>>>
>>>
>>>
>>>
>>> And the pedal effort in a 4400-lb 1969 vehicle with manual disk
>>> brakes is NOT significantly higher than the pedal effort in a Honda
>>> Accord of today. And disk vs. drum makes no difference at all. I just
>>> don't see whay the staement that power boost "is a necessity with
>>> disk brakes" keeps popping into discussions.
>>
>>
>>
>> That's an honest question. So you are telling me that, in the
>> otherwise same vehicle, a non-vacuum assisted disc brake will take no
>> more pedal pressure and at the same time no more pedal travel than a
>> non-vacuum assisted self-energizing drum brake?
>
>
> Not at all- I'm saying that it will take MORE pedal travel, but that
> more pedal travel is a GOOD thing because it allows finer modulation of
> braking pressure. The pedal effort will depend on the amount of increase
> in the pedal stroke, and will typically be a little higher than a
> non-boosted system. But I think its quite safe to say that there are
> non-boosted cars out there that have less pedal effort than some boosted
> cars. There's a lot of overlap. I'll say again that people equate "power
> brakes with a failed booster" to "non-power brakes" and that's just flat
> WRONG. A failed booster makes pedal effort FAR higher than non-power
> brakes.

Because the non-boosted system is designed for the differences.

Fair enough.

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

> wrote in message
...
> On Tue, 01 Feb 2005 20:00:04 -0500, Bill Putney >
> wrote:
>
>>Steve wrote:
>>
>>> Bernard farquart wrote:
>>>
>>>>
>>>> Anyone who thinks International Harvester products were
>>>> *under* engineered has no concept of what they are talking about.
>
> I worked for a "corn binder" dealer in the early seventies, and my
> impression then and now, was "under engineered and over built". They
> were dirt simple, rock solid, butt ugly, almost indestructible, crude,
> purpose built machinery.
> They were elegent in their simplicity, and if the ultimate test of
> engineering is not that nothing more can be added, but rather that
> nothing more can be removed, then you could say they were well
> engineered.

For a sports car, that would be *under* engineered, for
a truck expected to stand up to poor treatment, poor
maintinence, poor fuel, etc.. and keep running and running
I think that is a pretty good definition of what the target
should be, IMHO.

Bernard

On Wed, 02 Feb 2005 19:47:27 GMT, "Bernard farquart"
> wrote:

>
>> So is it because wheels are round and transmissions and alternators are
>> irregularly shaped that there's a difference in how they are referred to?
>> Just trying to figure out the rules. 8^)
>>
>
>Nope, the difference is in how they are sourced and installed
>and how parts are cataloged for them. If you need an alternator
>for your BMW you may be asked if it is a Bosch unit or a Marshal
>because the alternator was purchased seperately and installed by BMW,
>not manufatured by them.
>
>If you have a honda, and you need a cap and rotor, you will need to know
>who made your distributor, TEC or Hitachi, or perhaps Mitsuba.
>just calling it a "Honda distributor" will make the parts counter guy
>laugh, but will not get you the part
>

No, you will ask for an alternator to fit a sept 1994 production (or a
an "N" code) Honda Civic SE, or whatever, and IF more than one
manufacturer was used on that model and production date, the
counterman will ask which one it is, as the alternator, or
distributor, or starter or whatever is built by these several
different companies SPECIFICALLY to HONDA specs. The mounting ear
location may fit ONLY a certain Honda engine, and nothing else.

And for wheels, it is just as correct to refer to say, a 4 boltX 98mm
13X5" J3 rim with negative offset as to say it is a Fiat 128L rim.
(numbets may be off a bit, but 4X98 it is. Or Chrysler 5X100mm, or GM
5X115, or Ford/AMC/Mopar 5X4.5?

DOes not matter what the original application was if it has the right
bolt pattern, size, and offset.


>> Truth is Daniel, knowledgeable people all the time refer to such devices
>> by application even though technically it's not up to your standards,
>
>Not always, and specifically not in automotive applications
>
>> and people all the time understand the information that is being conveyed
>
>Nope, not always
>
>(which is the goal most of the time. No different I guess in
>> correcting someone when they refer to a "lash adjuster" as a lifter, or
>> talking about torque in pounds, both of which I joke about all the time.
>> Just depends on how anal we all want to be.
>
>You must be an engineer, lots of theory, no practical
>application as applies to automotive.
>
>I know that some of the people who plst are engineers,
>but I have seen to much of this "really informed mis-information"
>from that particular class in my sixteen years of selling
>auto parts in Seattle (Boeing country) to miss making the
>observation.
>
>Bernard
>

On Tue, 01 Feb 2005 19:22:46 -0500, Nate Nagel >
wrote:

>Nate Nagel wrote:
>
>> Daniel J. Stern wrote:
>>
>>> On Tue, 1 Feb 2005, Nate Nagel wrote:
>>>
>>>
>>>>> There are *many* ways of varying the mechanical advantage of the
>>>>> driver's foot over the disc caliper pistons.
>>>
>>>
>>>
>>>> True, but a lot of them involve tradeoffs, usually in the "stroke" of
>>>> the master cylinder.
>>>
There is ONE reason why disk brakes generally are more likely to
require a booster, and it relates directly to increased pedal motion.
Put simply, a disk brake caliper has a much larger piston than a wheel
cyl, and therefore it takes more fluid to move the pads. To move that
volume of fluid and produce the required pressure without excessive
pedal travel on an undeslung pedal design is not impossible - but
using a booster makes it significantly easier.

> wrote in message
...
> On Wed, 02 Feb 2005 19:47:27 GMT, "Bernard farquart"
> > wrote:
>
>>
>>> So is it because wheels are round and transmissions and alternators are
>>> irregularly shaped that there's a difference in how they are referred
>>> to?
>>> Just trying to figure out the rules. 8^)
>>>
>>
>>Nope, the difference is in how they are sourced and installed
>>and how parts are cataloged for them. If you need an alternator
>>for your BMW you may be asked if it is a Bosch unit or a Marshal
>>because the alternator was purchased seperately and installed by BMW,
>>not manufatured by them.
>>
>>If you have a honda, and you need a cap and rotor, you will need to know
>>who made your distributor, TEC or Hitachi, or perhaps Mitsuba.
>>just calling it a "Honda distributor" will make the parts counter guy
>>laugh, but will not get you the part
>>
>
> No, you will ask for an alternator to fit a sept 1994 production (or a
> an "N" code) Honda Civic SE, or whatever, and IF more than one
> manufacturer was used on that model and production date, the
> counterman will ask which one it is, as the alternator, or
> distributor, or starter or whatever is built by these several
> different companies SPECIFICALLY to HONDA specs. The mounting ear
> location may fit ONLY a certain Honda engine, and nothing else.

Not true, alternators may be used on BMW, or Volvo, or Volkswagon
that are the same part number.

Distributor caps that fit a Subaru may also be found on a Toyota.

Don't take my word for it (since I have only been ASE certified P2
for ten freekin' years) open up a buyers guide for Standard,Niehoff,
any tune up parts manufacterer. Then look in the back of a buyers guide for
rotating electrical (alternators & starters) and see what the application
listings are by part number.

A little knowledge.....


Bernard