air bags again(War and Peace Topic)

[hdavis]

>
>Henry, Henry,---Henry,
>
>Gee thanks? Henry- were you trying to destroy our neurons--or were you
>trying to destroy yours? My mistake was, I tried to read it before I had my
>first cup of coffee this morning. I think I will read it again just before I
>go to bed tonight.
>
>Kidding aside, thank you for the post!
>

What??? read it before you go to bed? Why such exciting reading will definately keep you up all night.

It's a bit of a hack analysis since I haven't calculated all of the geometry, but it errs on the side of being conservative (I
think).

Actually, I took the opportunity to start my "here's the rational reason for my spending another grand on the GMC" for the 4-
bag system. I've been on-again off-again about the 4-bag. I'm now reasonably convinced that this is one suspension mod that
has very little downside, but apparantly a lot of upside. I guess I ought to do the engineering calculations completely to see
just how much weight transfer occurs for different size obstacles.

Henry

Henry Davis Consulting, Inc / new product consulting
PO Box 1270 / product readiness reviews
Soquel, Ca 95073 / IP reviews
ph: (408) 462-5199 / full service marketing
fax: (408) 462-5198
http://www.henry-davis.com

 

[thomas g. warner]

Just a note. the 4 bag system does not work the same way the original
system did. With the 4 bag system the middle tower restricts any force on
the front bogie to only that wheel, in other words the 4 bogie wheels are
entirely independent. in the original sytem, hit a bump with the front
bogie and a force is immediately transferred to the rear one on the same
side. Much much different mechanics and an entirely different dynamic model.

Try taking the front bogie wheels off a 23' coach and driving it and see the
difference?

>>
>>Henry, Henry,---Henry,
>>
>>Gee thanks? Henry- were you trying to destroy our neurons--or were you
>>trying to destroy yours? My mistake was, I tried to read it before I had my
>>first cup of coffee this morning. I think I will read it again just before I
>>go to bed tonight.
>>
>>Kidding aside, thank you for the post!
>>
>
>What??? read it before you go to bed? Why such exciting reading will
definately keep you up all night.
>
>It's a bit of a hack analysis since I haven't calculated all of the
geometry, but it errs on the side of being conservative (I
>think).
>
>Actually, I took the opportunity to start my "here's the rational reason
for my spending another grand on the GMC" for the 4-
>bag system. I've been on-again off-again about the 4-bag. I'm now
reasonably convinced that this is one suspension mod that
>has very little downside, but apparantly a lot of upside. I guess I ought
to do the engineering calculations completely to see
>just how much weight transfer occurs for different size obstacles.
>
>Henry
>
>
>Henry Davis Consulting, Inc / new product consulting
>PO Box 1270 / product readiness reviews
>Soquel, Ca 95073 / IP reviews
>ph: (408) 462-5199 / full service marketing
>fax: (408) 462-5198
>http://www.henry-davis.com
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach

 

[balcom robin s]

Tom:

I've never seen a 4 bag system in person, but from the pictures I've seen,
it appears that the front and rear bags are "connected" through the air
tubing. It appears that they can be made independent by closing the two
valves, but with the valves open, air can be transferred from one bag to the
other. This, in effect, duplicates the original system.

- - On the original system, the force is transferred instantly, as you
describe.
- - On the 4 bag system, if you have the valves open, the force is still
transferred, but by the force on the air going through the tubing.
- - On the 4 bag system, if you have the valves closed, each bag is
independent, and no force is transferred.

As I think about "transferred instantly" (on the original system), I can see
that not all of the force is transferred (some is absorbed by the action of
the bag expanding) and it's not necessarily instantaneous (it's slowed to an
extent by the same expansion of the bag). If there were such a thing as a
"stiffer" bag (thicker sidewall construction), more of the force would be
transferred, and it would be transferred quicker. Plus, a "stiffer" bag
would be more resistant to allowing the GMC to roll as it turns. I wonder if
the bags used in the 4 bag system are of a thicker construction? If so, that
would explain (to me at least) the improvement in ride that some have
reported.

Well, that's all, that's what I think. If we were talking face to face, I'd
say I was just thinking off the top of my head. Instead, though, I'll have
to say I was thinking off the ends of my fingers (two, actually).

Robin
'73 Sequoia
Corning, NY

 

[bartz paul]

Robin:

I'm told the spring rate of the original air bags is a little over 400 psi
and the four-air bag spring rate is one-third greater, over 600 psi.

Paul Bartz

From: Balcom, Robin S [mailto:BalcomRS]
Sent: Tuesday, December 29, 1998 12:29 PM
Subject: Re: GMC: air bags again(War and Peace Topic)

Just a note. the 4 bag system does not work the same way the original
system did. With the 4 bag system the middle tower restricts any force on
the front bogie to only that wheel, in other words the 4 bogie wheels are
entirely independent. in the original sytem, hit a bump with the front
bogie and a force is immediately transferred to the rear one on the same
side. Much much different mechanics and an entirely different dynamic model.

Tom:
I've never seen a 4 bag system in person, but from the pictures I've seen,
it appears that the front and rear bags are "connected" through the air
tubing. It appears that they can be made independent by closing the two
valves, but with the valves open, air can be transferred from one bag to the
other. This, in effect, duplicates the original system.
* On the original system, the force is transferred instantly, as you
describe.
* On the 4 bag system, if you have the valves open, the force is still
transferred, but by the force on the air going through the tubing.
* On the 4 bag system, if you have the valves closed, each bag is
independent, and no force is transferred.

As I think about "transferred instantly" (on the original system), I can see
that not all of the force is transferred (some is absorbed by the action of
the bag expanding) and it's not necessarily instantaneous (it's slowed to an
extent by the same expansion of the bag). If there were such a thing as a
"stiffer" bag (thicker sidewall construction), more of the force would be
transferred, and it would be transferred quicker. Plus, a "stiffer" bag
would be more resistant to allowing the GMC to roll as it turns. I wonder
if the bags used in the 4 bag system are of a thicker construction? If so,
that would explain (to me at least) the improvement in ride that some have
reported.
Well, that's all, that's what I think. If we were talking face to face, I'd
say I was just thinking off the top of my head. Instead, though, I'll have
to say I was thinking off the ends of my fingers (two, actually).
Robin
'73 Sequoia
Corning, NY