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Simultaneous Application of Gas and Brake Pedals



 
 
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  #51  
Old February 2nd 05, 01:56 AM
Bill Putney
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Daniel J. Stern wrote:

> On Tue, 1 Feb 2005, Bernard farquart wrote:
>
>
>>Anyone who thinks International Harvester products were *under*
>>engineered has no concept of what they are talking about.

>
>
> There is that, but I didn't pick on Putney for it 'cause his claim that
> "AMC automatic transmissions" was crying out louder for attention.


Ignoring the fact that I never said they were under-engineered, though I
did point out that they put an automotive tranny in a tank with no
cooler on it that needed fluid replacement every 20k miles. Yeah - I
would call that particular feature under-engineered, though I had not
called it that. Grossly under-engineered here, grossly over-engineered
everywhere else - maybe the correct term for them would be "very
unbalanced" (which is by definition "not competitive" as time proved).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')
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  #52  
Old February 2nd 05, 02:00 AM
Bill Putney
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Steve wrote:

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

>
> 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')
  #53  
Old February 2nd 05, 02:32 AM
Bill Putney
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Nate Nagel wrote:

> Yeah... really, it boils down to how much room do you have between the
> top of the pedal stroke and the floor of the car (don't want to have the
> pedal too high, that would be bad ergonomically - you should be able to
> get your foot on it without taking your heel off the floor) and can you
> juggle your bore sizes and/or linkage to get a reasonable (or Federally
> mandated) pedal effort within those parameters while not having the
> pedal go to the floor either with one circuit failed or during a full
> ABS stop from whatever your maximum design speed is. If you can't, then
> you go to a power booster. I'm sure that someone could probably give a
> rough, hand-waving estimate (like I have above, but a more informed one)
> as to appx. what vehicle weight that starts to happen at... but the
> point is, that weight would be significantly higher for a drum brake car
> because a) they require less fluid movement (or should, if the shoes are
> properly adjusted - since they have positive return springs you really
> can't count on that though unless self adjusters are included) and b)
> they require less line pressure.


There you are. Throw in your intial tolerance
stackups/vehicle-to-vehicle variations on all that stuff, and then add
the variations as things age, and you have no more design safety margins
left, and you're eaten up with recalls and bad publicity.

So can anyone say how many models of mass-produced passenger vehicles
sold in the U.S. in the last 10 years have disc brakes without boost of
some sort? Is it more than zero?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')
  #54  
Old February 2nd 05, 03:23 AM
Daniel J. Stern
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On Tue, 1 Feb 2005, Nate Nagel wrote:

> damn, I really hate it when I have to play the "credentials" card


Yeah, eh? I try to avoid it, and I figure I'm about 80% successful.
Nowtimes, I usually just killfile jokers who spoil for a credentials
****ing match. "KaWALLski" doesn't really need to know why it's so
laughable for him to try and argue headlamps with me, and "Loathesome
Pawn" doesn't really need to know that I'm an appointed member of the
National Academy of Sciences Transportation Research Board (Oops! Oh well,
add that to the 20%!)

-DS (...he also doesn't need to know he misspelled "loathsome"...)
  #55  
Old February 2nd 05, 04:52 AM
Daniel J. Stern
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On Tue, 1 Feb 2005, Bill Putney wrote:

>>> Any reasonable person would accept referring to a transmission that
>>> was used in AMC vehicles as an AMC transmission.


> > Only if they had no clue how parts are sourced and put together, or
> > what the difference between a part made by a company & just installed.


> So you would *never* refer to certain wheels in a junk yard as
> "Chevrolet wheels" or "Ford wheels".


Sure you would. But you wouldn't refer to an "AMC starter" (it's a Delco)
or an "AMC alternator" (it's a Motorola) or an "AMC carburetor" (it's a
Carter or a Holley) or an "AMC transmission" (it's a Hydramatic or a
Torqueflite).

You *would*, however, refer to an "AMC engine".

I'm sure you can understand the difference. The question is whether you'll
choose to admit it.
  #56  
Old February 2nd 05, 12:26 PM
Bill Putney
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Daniel J. Stern wrote:
> On Tue, 1 Feb 2005, Bill Putney wrote:
>
>
>>>>Any reasonable person would accept referring to a transmission that
>>>>was used in AMC vehicles as an AMC transmission.

>
>
>>>Only if they had no clue how parts are sourced and put together, or
>>>what the difference between a part made by a company & just installed.

>
>
>>So you would *never* refer to certain wheels in a junk yard as
>>"Chevrolet wheels" or "Ford wheels".

>
>
> Sure you would. But you wouldn't refer to an "AMC starter" (it's a Delco)
> or an "AMC alternator" (it's a Motorola) or an "AMC carburetor" (it's a
> Carter or a Holley) or an "AMC transmission" (it's a Hydramatic or a
> Torqueflite).
>
> You *would*, however, refer to an "AMC engine".
>
> I'm sure you can understand the difference. The question is whether you'll
> choose to admit it.


Well, you'll have to tell the guy who was knowledgeable enough to know
the different applications and conveyed that to me - except he's been
dead probably 15 or 20 years. anbd which I understood what he meant -
just as people here understood what was meant even though it was not
quite up to the Stern standard for truth and excellence.

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^)

Truth is Daniel, knowledgeable people all the time refer to such devices
by application even though technically it's not up to your standards,
and people all the time understand the information that is being
conveyed (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.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')
  #57  
Old February 2nd 05, 12:32 PM
Bill Putney
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Bill Putney wrote:
>
> Well, you'll have to tell the guy who was knowledgeable enough to know
> the different applications and conveyed that to me - except he's been
> dead probably 15 or 20 years. anbd which I understood what he meant -
> just as people here understood what was meant even though it was not
> quite up to the Stern standard for truth and excellence.
>
> 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^)
>
> Truth is Daniel, knowledgeable people all the time refer to such devices
> by application even though technically it's not up to your standards,
> and people all the time understand the information that is being
> conveyed (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.


Hmmm - speaking of being anal - looking back at what I just posted - was
a time I would have been mortified at the typos I made in that
masterpiece. Oh well. In too much of a hurry. (and look at that - two
incomplete sentences in a row! Wuff!

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')
  #58  
Old February 2nd 05, 05:16 PM
Steve
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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.
  #59  
Old February 2nd 05, 05:22 PM
Steve
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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.
>>>
>>>
>>>
>>>
>>> Yes...
>>>
>>>
>>>> A smaller bore in the MC will provide good pedal feel and acceptable
>>>> pedal effort, BUT is not often workable in modern braking systems as
>>>> the
>>>> pedal will eventually "bottom out" on a full-effort, high-speed,
>>>> ABS-active stop - definitely something you don't want to happen.
>>>> Likewise, there may not be enough room to leave enough pedal left in a
>>>> one-circuit-failed condition.
>>>
>>>
>>>
>>>
>>> You've engineered more brake systems than I have, to be sure, but I'm
>>> not
>>> sure I believe that either of these must necessarily be the case. You
>>> might be able to convince me.

>>
>>
>>
>> Actually, not really. I never engineered a brake system from scratch,
>> unless you count mixing amd matching parts on my own personal
>> vehicles. But I have seen what happens when you get something a
>> little off, like the MC bore size and your 70 MPH panic stop turns out
>> to be a little more interesting than you planned on when the ABS'
>> hydraulic accumulators suck all the fluid out of the MC. Whoopsie!
>>
>> Keep in mind, however, that most of the stuff I worked on
>> professionally was light trucks - these issues may not actually
>> surface for passenger cars. The point that I was trying to make is,
>> simply, that there really are good engineering reasons to use a power
>> booster, and that they become more compelling when using disc brakes
>> as opposed to drums.
>>
>>>
>>>
>>>> Additionally, a litigation-sensitive corporation isn't going to release
>>>> a vehicle for production requiring *any* higher-than-normal pedal
>>>> effort
>>>
>>>
>>>
>>>
>>> Sued for installing airbags
>>> Sued for NOT installing airbags
>>>
>>> =
>>>
>>> Sued 'cause the booster fails
>>> Sued 'cause the pedal effort was "too high"
>>>
>>> Remember, there are Federal standards for pedal effort.
>>>

>>
>> Yeah... really, it boils down to how much room do you have between
>> the top of the pedal stroke and the floor of the car (don't want to
>> have the pedal too high, that would be bad ergonomically - you should
>> be able to get your foot on it without taking your heel off the floor)
>> and can you juggle your bore sizes and/or linkage to get a reasonable
>> (or Federally mandated) pedal effort within those parameters while not
>> having the pedal go to the floor either with one circuit failed or
>> during a full ABS stop from whatever your maximum design speed is. If
>> you can't, then you go to a power booster. I'm sure that someone
>> could probably give a rough, hand-waving estimate (like I have above,
>> but a more informed one) as to appx. what vehicle weight that starts
>> to happen at... but the point is, that weight would be significantly
>> higher for a drum brake car because a) they require less fluid
>> movement (or should, if the shoes are properly adjusted - since they
>> have positive return springs you really can't count on that though
>> unless self adjusters are included) and b) they require less line
>> pressure.
>>
>> nate
>>

>
> One more thing I meant to add...
>
> yet another reason why the "my '67 whatever had manual brakes and
> stopped just fine" does not translate over to a similar weight modern
> car *not* requiring a power booster... I've been told, although I have
> no hard numbers to back this up, that old asbestos brake linings
> actually have a higher coefficient of friction than most modern linings.
>


My comment was in reference to a '69 (so it does have a split braking
system just like a modern car- which I can also see making quite a
difference). I should also point out that it performs just fine with
*modern* lining materials- I'm not anal enough about it to dig up NOS
brake linings from 1969! And besides, I like to DRIVE it not just have a
trailer queen, which is what happens if you insist on NOS service items
like brake linings, belts, and hoses.
  #60  
Old February 2nd 05, 05:26 PM
Steve
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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.

 




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