Miatapower List Archive

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Mail From: (email redacted)

Stiction = Sticky Friction :-)

This read-only message was archived from a public mail list.
Mail From: (email redacted)


Ok, so how does sticky friction work in the case of pressure on a diaphram
inside a pressure sender?

Wallyman




(email redacted)
To: (email redacted), (email redacted)
02/10/2003 11:24 cc: (email redacted)
AM Subject: Re: Stiction?






Stiction = Sticky Friction :-)

This read-only message was archived from a public mail list.
Mail From: (email redacted)


I've never heard of that before, guess you learn something new everyday
around here! Makes me think of tapping the ole Super Slurpee cup on the
counter to keep the contents settling...or I'm just thirsty and that has
nothing to do with Stiction. :)

Which part of the process is affected by the Stiction, the place where the
oil touches the sender pressure point? Also, the stiction causes what..
slower response/lack of change in indication when there should be?

Wallyman




"Chris Messmer"
<(email redacted) To: (email redacted)
m> cc: (email redacted), (email redacted), (email redacted)
Subject: Re: Stiction? was Re: Dual oil pressure gauges ... engine mounting .....
02/10/2003 11:33 requiredr
AM







Walt , Stiction is a word used to describe the situation where friction
causes dampening or stickiness .... Stiction. Used mainly (in my
experience) to describe stickiness in suspension components that are
located by bearings (as apposed to rubber bushings), the resistance to
rotation within a balljoint would be an extreme example .... the effect
that say a dust seal on a shock has on it's function would be an example at
the other end of the spectrum.

In my race car I have both digital gauges that data log (driven by Stewart
Warner senders) and liquid filled, top of the line Mechanical gauges .....
they don't agree all of the time. While my experience is mainly with
Stewart Warner senders I have found this same problem in other senders.

Here is an excerpt from Stewart Warners "engineering specifications" for
#411 series pressure senders:

..... 5) ACCURACY CHECK
The sender shall meet the following resistance versus pressure
specification with light physical tapping of the sender.

according to the good folks at Stewart Warner this should get better as the
unit "seasons" (my word not theirs) ...... and they do improve a little,
but not enough to mount them where they wont vibrate (IMO).

Chris






Walt_Helsel@URSCo

rp.com To: "Chris Messmer"
<(email redacted)>
cc:
(email redacted), (email redacted),
02/10/03 08:11 AM (email redacted)

Subject: Stiction? was Re:
Dual oil pressure gauges ... engine
mounting ..... required







????

Never heard that before. What about those wonderful Mechanical gauges that
have a hose running to the cabin (You know, those reaaaaaaaaally high
quality ones at PepBoys/Autozone)?

This is a new requirement to me.. can you elaborate? Also, would this
apply to a Fuel pressure sender as well? Mine's on the firewall without a
single issue.

Wallyman




"Chris Messmer"

<(email redacted) To: Mark Cookson
<(email redacted)>
m> cc: Marc Kulak
<(email redacted)>, (email redacted)
Subject: Re: Dual oil
pressure gauges ... engine mounting ..... required
02/10/2003 10:51

AM








be aware that some (most) senders rely on vibration to overcome the
"stiction" inherent in their design ..... so I would be inclined to remote
mount the senders (by way of flexible line) on the motor somewhere.... or
mount the sender where you can tap it while you are driving.

Chris

This read-only message was archived from a public mail list.
Mail From: "Chris Messmer" <(email redacted)>


it seems that mostly they read low until you tap them (which would support
SW's plan of "get's better with age") , but they do tend to hang high a
little as well.

(slowness) speed of response vs actual pressure change is not so much an
issue, however, I think that when the actual change is faster (more
violent) the resulting reading tends to be more accurate than from a
gradual change.

Chris




Walt_Helsel@URSCo
rp.com To: "Chris Messmer" <(email redacted)>
cc: (email redacted)
02/10/03 08:51 AM Subject: Re: Stiction?







I've never heard of that before, guess you learn something new everyday
around here! Makes me think of tapping the ole Super Slurpee cup on the
counter to keep the contents settling...or I'm just thirsty and that has
nothing to do with Stiction. :)

Which part of the process is affected by the Stiction, the place where the
oil touches the sender pressure point? Also, the stiction causes what..
slower response/lack of change in indication when there should be?

Wallyman




"Chris Messmer"

<(email redacted) To:
(email redacted)

m> cc:
(email redacted), (email redacted), (email redacted)

Subject: Re: Stiction? was
Re: Dual oil pressure gauges ... engine mounting .....
02/10/2003 11:33 requiredr

AM








Walt , Stiction is a word used to describe the situation where friction
causes dampening or stickiness .... Stiction. Used mainly (in my
experience) to describe stickiness in suspension components that are
located by bearings (as apposed to rubber bushings), the resistance to
rotation within a balljoint would be an extreme example .... the effect
that say a dust seal on a shock has on it's function would be an example at
the other end of the spectrum.

In my race car I have both digital gauges that data log (driven by Stewart
Warner senders) and liquid filled, top of the line Mechanical gauges .....
they don't agree all of the time. While my experience is mainly with
Stewart Warner senders I have found this same problem in other senders.

Here is an excerpt from Stewart Warners "engineering specifications" for
#411 series pressure senders:

..... 5) ACCURACY CHECK
The sender shall meet the following resistance versus pressure
specification with light physical tapping of the sender.

according to the good folks at Stewart Warner this should get better as the
unit "seasons" (my word not theirs) ...... and they do improve a little,
but not enough to mount them where they wont vibrate (IMO).

Chris






Walt_Helsel@URSCo

rp.com To: "Chris Messmer"
<(email redacted)>
cc:
(email redacted), (email redacted),
02/10/03 08:11 AM (email redacted)

Subject: Stiction? was Re:
Dual oil pressure gauges ... engine
mounting ..... required







????

Never heard that before. What about those wonderful Mechanical gauges that
have a hose running to the cabin (You know, those reaaaaaaaaally high
quality ones at PepBoys/Autozone)?

This is a new requirement to me.. can you elaborate? Also, would this
apply to a Fuel pressure sender as well? Mine's on the firewall without a
single issue.

Wallyman




"Chris Messmer"

<(email redacted) To: Mark Cookson
<(email redacted)>
m> cc: Marc Kulak
<(email redacted)>, (email redacted)
Subject: Re: Dual oil
pressure gauges ... engine mounting ..... required
02/10/2003 10:51

AM








be aware that some (most) senders rely on vibration to overcome the
"stiction" inherent in their design ..... so I would be inclined to remote
mount the senders (by way of flexible line) on the motor somewhere.... or
mount the sender where you can tap it while you are driving.

Chris

This read-only message was archived from a public mail list.
Mail From: "Maniacal Engineer" <(email redacted)>

Actually.. "stiction" is not sticky friction, it's
*static* friction.

Static friction is usually much higher than sliding
friction which is what makes it stick. That's why ABS
brakes work so well. The tire is not moving relative
to the ground normally... but when it does move
relative to the ground, you lose traction.

Try an example yourself... take something heavy and try
to push it from a dead stop. It's hard to move but
once it's moving it's not so hard to move anymore.

Matt


- - -
Matt Yates - Oakland, CA
y8s.com

This read-only message was archived from a public mail list.
Mail From: "Chris Messmer" <(email redacted)>


static .... that's the word I was looking for .....



"Maniacal
Engineer" To: (email redacted)
<(email redacted)> cc: (email redacted), (email redacted)
Subject: Re: Stiction?
02/10/03 09:38 AM






Actually.. "stiction" is not sticky friction, it's
*static* friction.

Static friction is usually much higher than sliding
friction which is what makes it stick. That's why ABS
brakes work so well. The tire is not moving relative
to the ground normally... but when it does move
relative to the ground, you lose traction.

Try an example yourself... take something heavy and try
to push it from a dead stop. It's hard to move but
once it's moving it's not so hard to move anymore.

Matt


- - -
Matt Yates - Oakland, CA
y8s.com