Home » Public Forums » GMCnet » Re: [GMCnet] Airbag loading question
| Re: [GMCnet] Airbag loading question [message #127759] |
Sat, 28 May 2011 11:59  |
Oldrvguybcg
Messages: 100
Registered: September 2008
Karma: 0
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Senior Member |
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Essentially the bogie arm is a variant of a 2nd Class lever. The reason the
Airbag doesn't see the full load of the entire side is because the lever
offers a mechanical advantage. Because of the laws of physics, the amount of
work required is the same because ultimately you are lifting a 4,000 lb.
load. The actually force on the airbag will vary depending on where you are
in the wheel's travel path. The ratio of the distance from the hub to the
pivot and the distance from the hub to the Airbag end is what gives toy the
mechanical advantage. The longer you make the distance from the hub to the
Airbag, the lower the force required to move the hub that has 2,000 lbs. of
weight on it. However, the lower the force required, the larger the
distance the arm will have to move to achieve the same vertical height.
Brian Gleissner
74 Sequoia
Woodbury, CT 06798
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| Re: [GMCnet] Airbag loading question [message #127760 is a reply to message #127759] |
Sat, 28 May 2011 12:15  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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That is why our Q Bags has the bags mounted about 1 1/4 " higher than
the normal height.
Ken Rose figured that out as he did not like the harsh ride of the
original 4 bag of Harrison.
Rick Flanagan, our designer also discovered that the original 4 bag
design did not line up straight. We had to put a bend on the back
support to get it to line up straight.
I fought that design change due to cost, but ended up doing it .
On Sat, May 28, 2011 at 9:59 AM, <Oldrvguybcg@aol.com> wrote:
> Essentially the bogie arm is a variant of a 2nd Class lever. The reason the
> Airbag doesn't see the full load of the entire side is because the lever
> offers a mechanical advantage. Because of the laws of physics, the amount of
> work required is the same because ultimately you are lifting a 4,000 lb.
> load. The actually force on the airbag will vary depending on where you are
> in the wheel's travel path. The ratio of the distance from the hub to the
> pivot and the distance from the hub to the Airbag end is what gives toy the
> mechanical advantage. The longer you make the distance from the hub to the
> Airbag, the lower the force required to move the hub that has 2,000 lbs. of
> weight on it. However, the lower the force required, the larger the
> distance the arm will have to move to achieve the same vertical height.
>
> Brian Gleissner
> 74 Sequoia
> Woodbury, CT 06798
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Airbag loading question [message #127766 is a reply to message #127759] |
Sat, 28 May 2011 12:42 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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However, the length of the arms on the GMC are nearly equal in length each
direction from the bogie pin or pivot point. 1" of upward travel on the tire
& wheel equates to the same movement on the air bag end of the lever. Forces
are equal also. Displacement changes in the airbag account for the increase
in air pressure in the bag. Formula for that is Dia x dia x.7854 x stroke
length in inches = CID. Figure the resting displacement in the bag, subtract
the volume of the loaded bag, multiply by internal pressure of the resting
bag, solve for the unknown and you should be able to approximate within 4
places the load increase on the other bogie arm in the time frame that the
suspension travel takes to move. Simple algebra should suffice, but what
will you understand when you know? <grin>
Jim Hupy
Salem, OR
78 GMc Royale 403
On Sat, May 28, 2011 at 9:59 AM, <Oldrvguybcg@aol.com> wrote:
> Essentially the bogie arm is a variant of a 2nd Class lever. The reason the
> Airbag doesn't see the full load of the entire side is because the lever
> offers a mechanical advantage. Because of the laws of physics, the amount
> of
> work required is the same because ultimately you are lifting a 4,000 lb.
> load. The actually force on the airbag will vary depending on where you
> are
> in the wheel's travel path. The ratio of the distance from the hub to the
> pivot and the distance from the hub to the Airbag end is what gives toy
> the
> mechanical advantage. The longer you make the distance from the hub to the
> Airbag, the lower the force required to move the hub that has 2,000 lbs.
> of
> weight on it. However, the lower the force required, the larger the
> distance the arm will have to move to achieve the same vertical height.
>
> Brian Gleissner
> 74 Sequoia
> Woodbury, CT 06798
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] Airbag loading question [message #127769 is a reply to message #127766] |
Sat, 28 May 2011 12:54 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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I'm glad you guys are applying yourselves to this. Just trying to understand it as I read it is taxing my remaining brain cells. I like the simple design of the stock system which gives my 77 royale awesome ground clearance. Withe the exception of the crazy looking pump covered in valves, the orig set up looks clean and simple. Too bad the bags are no longer made. I think I read on this forum that our original bags were designed for some out of country commercial application. If so, what are the odds of a pile of them sitting in little boxes on some dusty shelf in a warehouse somewhere?
I can almost picture it.........
Sully
77 royale
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: James Hupy <jamesh1296@gmail.com>
Sender: gmclist-bounces@temp.gmcnet.org
Date: Sat, 28 May 2011 10:42:13
To: <gmclist@temp.gmcnet.org>
Reply-To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Airbag loading question
However, the length of the arms on the GMC are nearly equal in length each
direction from the bogie pin or pivot point. 1" of upward travel on the tire
& wheel equates to the same movement on the air bag end of the lever. Forces
are equal also. Displacement changes in the airbag account for the increase
in air pressure in the bag. Formula for that is Dia x dia x.7854 x stroke
length in inches = CID. Figure the resting displacement in the bag, subtract
the volume of the loaded bag, multiply by internal pressure of the resting
bag, solve for the unknown and you should be able to approximate within 4
places the load increase on the other bogie arm in the time frame that the
suspension travel takes to move. Simple algebra should suffice, but what
will you understand when you know? <grin>
Jim Hupy
Salem, OR
78 GMc Royale 403
On Sat, May 28, 2011 at 9:59 AM, <Oldrvguybcg@aol.com> wrote:
> Essentially the bogie arm is a variant of a 2nd Class lever. The reason the
> Airbag doesn't see the full load of the entire side is because the lever
> offers a mechanical advantage. Because of the laws of physics, the amount
> of
> work required is the same because ultimately you are lifting a 4,000 lb.
> load. The actually force on the airbag will vary depending on where you
> are
> in the wheel's travel path. The ratio of the distance from the hub to the
> pivot and the distance from the hub to the Airbag end is what gives toy
> the
> mechanical advantage. The longer you make the distance from the hub to the
> Airbag, the lower the force required to move the hub that has 2,000 lbs.
> of
> weight on it. However, the lower the force required, the larger the
> distance the arm will have to move to achieve the same vertical height.
>
> Brian Gleissner
> 74 Sequoia
> Woodbury, CT 06798
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Airbag loading question [message #127774 is a reply to message #127769] |
Sat, 28 May 2011 13:23 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Sully, where the length of the arms are equal, motion is 1:1 and so is the
forces. Where the arms are of unequal length, the force applied at input is
either increased or decreased depending on the comparitive length of the
levers. However if the travel is increased on one end and the arm on the bag
end is shorter, the force on the bag will be greater, but the distance that
it travels is reduced by the ratio differential. Clear as mud, right. I
think I hear a tri power setup in my shop calling to me to change throttle
shafts for progressive linkages to be installed. My customer is waiting for
it with money in his hands. That at least has some direct effect on my
wallet.<grin>
Jim Hupy
Salem, OR
78 GMc Royale 403
On Sat, May 28, 2011 at 10:54 AM, <sgltrac@gmail.com> wrote:
> I'm glad you guys are applying yourselves to this. Just trying to
> understand it as I read it is taxing my remaining brain cells. I like the
> simple design of the stock system which gives my 77 royale awesome ground
> clearance. Withe the exception of the crazy looking pump covered in valves,
> the orig set up looks clean and simple. Too bad the bags are no longer made.
> I think I read on this forum that our original bags were designed for some
> out of country commercial application. If so, what are the odds of a pile of
> them sitting in little boxes on some dusty shelf in a warehouse somewhere?
> I can almost picture it.........
>
> Sully
> 77 royale
> Sent from my Verizon Wireless BlackBerry
>
> -----Original Message-----
> From: James Hupy <jamesh1296@gmail.com>
> Sender: gmclist-bounces@temp.gmcnet.org
> Date: Sat, 28 May 2011 10:42:13
> To: <gmclist@temp.gmcnet.org>
> Reply-To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Airbag loading question
>
> However, the length of the arms on the GMC are nearly equal in length each
> direction from the bogie pin or pivot point. 1" of upward travel on the
> tire
> & wheel equates to the same movement on the air bag end of the lever.
> Forces
> are equal also. Displacement changes in the airbag account for the increase
> in air pressure in the bag. Formula for that is Dia x dia x.7854 x stroke
> length in inches = CID. Figure the resting displacement in the bag,
> subtract
> the volume of the loaded bag, multiply by internal pressure of the resting
> bag, solve for the unknown and you should be able to approximate within 4
> places the load increase on the other bogie arm in the time frame that the
> suspension travel takes to move. Simple algebra should suffice, but what
> will you understand when you know? <grin>
> Jim Hupy
> Salem, OR
> 78 GMc Royale 403
>
> On Sat, May 28, 2011 at 9:59 AM, <Oldrvguybcg@aol.com> wrote:
>
> > Essentially the bogie arm is a variant of a 2nd Class lever. The reason
> the
> > Airbag doesn't see the full load of the entire side is because the lever
> > offers a mechanical advantage. Because of the laws of physics, the
> amount
> > of
> > work required is the same because ultimately you are lifting a 4,000 lb.
> > load. The actually force on the airbag will vary depending on where you
> > are
> > in the wheel's travel path. The ratio of the distance from the hub to
> the
> > pivot and the distance from the hub to the Airbag end is what gives toy
> > the
> > mechanical advantage. The longer you make the distance from the hub to
> the
> > Airbag, the lower the force required to move the hub that has 2,000 lbs.
> > of
> > weight on it. However, the lower the force required, the larger the
> > distance the arm will have to move to achieve the same vertical height.
> >
> > Brian Gleissner
> > 74 Sequoia
> > Woodbury, CT 06798
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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