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| What Is Bag Pressure at max height. [message #279343] |
Mon, 08 June 2015 09:25  |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Hi All. I know that some of you have air pressure gauges conected to each air bag on your coach. I know it will be dependent on coach gross weight, but what pressure are you noting as being needed to raise the coach to the shock limits. (Max height During camping).
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: What Is Bag Pressure at max height. [message #279346 is a reply to message #279343] |
Mon, 08 June 2015 09:53  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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John, This question is further complicated by type of air bag system. OEM,Sully, 4 bag (Leigh Harrison), quad bag (JmK),etc.
My 4 bag system rides at recommended ride height level at 90 pounds of pressure.
Would make an interesting spread sheet.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: What Is Bag Pressure at max height. [message #279349 is a reply to message #279343] |
Mon, 08 June 2015 10:41 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Your Right on all accounts Tom. I was Not very clear. And a spreadsheet would be interesting
I was thinking the OEM Bag.
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: What Is Bag Pressure at max height. [message #279351 is a reply to message #279343] |
Mon, 08 June 2015 10:50 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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My "Sully" type runs at around 40PSI depending on fuel level in the auto position. Usually a little more always on the left for the 600lb ballast in the left rear corner. I ran mine all the way up yesterday and didn't even pay attention to the pressure. If you really would like to know full heighth pressure I can get it tonite.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: What Is Bag Pressure at max height. [message #279353 is a reply to message #279343] |
Mon, 08 June 2015 11:00 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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I'll further clarify what I'm after. Once the OEM bag has raised the coach as far as it can go. It's no use adding more pressure because that will only strain everything (especially the bag) mine are not new. When the suspension is at it's limit,the bag has nowhere to go anymore and the extra pressure is only going to stress the bags more than needed.
thanks.
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: What Is Bag Pressure at max height. [message #279357 is a reply to message #279343] |
Mon, 08 June 2015 11:40 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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John Heslinga wrote on Mon, 08 June 2015 08:25Hi All. I know that some of you have air pressure gauges conected to each air bag on your coach. I know it will be dependent on coach gross weight, but what pressure are you noting as being needed to raise the coach to the shock limits. (Max height During camping).
My 78 Eleganza runs around 85 at level and 120 full up. Stock bag configuration.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] What Is Bag Pressure at max height. [message #279375 is a reply to message #279353] |
Mon, 08 June 2015 16:01 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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John,
I agree that what you want to know is good information and that having a pressure reading would be interesting, however, that number
is going to be all over the place even if one only considers the OEM bag.
To demonstrate an acute grasp on the obvious - the pressure required will be directly proportional to the amount of weight on the
rear suspension. It will vary side to side as well. It will also vary depending on the type of shock installed.
I vaguely remember seeing a document that provided the extended and compressed lengths of Bilstein, Caspro, and KYB shocks and IIRC
they all had different fully compressed lengths.
To determine this pressure I would run the pressure up 10 psi at a time on each side. If you run one side up fully and not the other
the number you get will not be accurate for that side.
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of John Heslinga
Sent: Tuesday, June 09, 2015 2:00 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] What Is Bag Pressure at max height.
I'll further clarify what I'm after. Once the OEM bag has raised the coach as far as it can go. It's no use adding more pressure
because that will only strain everything (especially the bag) mine are not new. When the suspension is at it's limit,the bag has
nowhere to go anymore and the extra pressure is only going to stress the bags more than needed.
thanks.
--
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: What Is Bag Pressure at max height. [message #279378 is a reply to message #279343] |
Mon, 08 June 2015 16:23 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Rob, I missed something. In what way does the shock absorber affect pressure in the air bag?
thanks,
Johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: What Is Bag Pressure at max height. [message #279379 is a reply to message #279378] |
Mon, 08 June 2015 17:00 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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The compressed length of the shock would only affect the maximum ride height on the GMC, but in the case of a gas-charged shock there could be more gas pressure pushing against the air bag as the shock is compressed more and more toward its final compressed length. Probably a negligible difference in air bag pressure, maybe not even measurable without a precision gauge. If you somehow had air or hydraulically adjustable shocks on the rear of the GMC, there would be a very measurable difference, but I'm not sure this is even possible, given the space allowed for the shocks.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: What Is Bag Pressure at max height. [message #279382 is a reply to message #279378] |
Mon, 08 June 2015 17:14 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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The shock absorber is the downward stop on the wheels. At it's most compressed position is the place where you have maximum height. So the compressed length of the various shock brands determines the maximum heights the the coach can go.
Clear as mud right?
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: What Is Bag Pressure at max height. [message #279389 is a reply to message #279343] |
Mon, 08 June 2015 18:55 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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OK, makes sense. Thanx. (I would of figured, for no good reason, they'd all be the same length compressed.)
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: What Is Bag Pressure at max height. [message #279409 is a reply to message #279343] |
Tue, 09 June 2015 00:41 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Hi All:
Thank you for your input!
Yes There are a lot of variables that will make differences in the pressure needed to make raise the coach to its limits (fully compressed Shocks) So too, there is some differences in the actual amount range of motion between coaches. I was not looking for a lot of accuracy but having a range of pressures that other owners were experiencing (If they were paying attention to installed Gauges during different states) The small amount of pressure that are in gas filled shocks really do not make any lift difference in any vehicle. I have never had any difficulty compressing a brand new shock (Im not very strong anymore) so that will not do very much in lifting the coach. The pressure and nitrogen is to stop aeration and cavitation, not lift. The Gas is usually in a bag to separate the oil from the gas too.
Thanks Gene for the link on Air Systems. I had not seen it before, I am in the middle of doing many of the upgrades now and that is the biggest reason I need the information.
I've installed a new Viair compressor with fresh electrical support, Tank, and outlets. The Viaire comes with a pressure switch that is set for 200 PSI. (non settable) That's too much for an OEM Bag. (Certainly put it at risk) Miguel and Jim B Stated that they seldom use air tanks and just use the compressor. (are they using the Viaire Pressure Switch? HMMM) Putting all of this together, Im trying to make some decisions on the kinds of pressures I should run in my system. (I'm using an adjustable pressure switch) I imagine that pumping the bags with 200 PSI while not paying full attention to what's going on would set up a bad situation
I'll Take this information and make some decisions.
Thanks again everyone!!
Link
http://www.gmcmhphotos.com/photos/discussion-photos/p58151-air-control.html
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
[Updated on: Tue, 09 June 2015 00:44] Report message to a moderator |
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| Re: [GMCnet] What Is Bag Pressure at max height. [message #279416 is a reply to message #279409] |
Tue, 09 June 2015 07:27 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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John,
I note that your GMC is a 1974 Canyonlands and IIRC they have a PowerLevel system. My GMC is a 1975 Avion which also has the
PowerLevel system with OEM bags.
A couple of years ago I installed a Viair 480C which I believe is the largest capacity single pump they make. JimB installed a small
solid state pressure switch in the system that turns the pump off when there is 140 psi in the tank and on when it drops to 90 psi.
Frankly I wish it would turn the pump on at a higher pressure.
IIRC the pump will take the PowerLevel system from 0 psi in the tank and bags to ride height (about 90 psi both sides) in around two
and a half minutes. However, as the pressure goes above 70 psi in the tank and bags the rate of inflation slows down quickly. Even
when the height control valves shut off the bags it takes awhile to reach 140 psi in the tank and the pump shuts down. I can't say
how long it would take to bring the bags from 90 to 140 as I've never done it. Since the pressure switch shuts the pump off at 140
psi I can't say how long it would take to go from 140 to 200 either.
Here's a link to that pumps performance stats, note how the flow slows down as the pressure goes up.
http://www.viaircorp.com/480C.html#tabs-2
Here's links to the two series of Viair Pressure switches available:
http://www.viaircorp.com/pswitches.html
Pressure Switches
P/N 90100 - 90 PSI On / 120 PSI Off
P/N 90101 - 85 PSI On / 105 PSI Off
P/N 90102 - 110 PSI On / 145 PSI Off - I believe this switch would be OK for a GMC
P/N 90103 - 165 PSI On / 200 PSI Off
For 12-Volt and 24-Volt systems up to 20 amps.
Tolerance is +/- 5% of specified pressures.
Included Parts: - 1/8" (M) NPT Port Fitting
http://www.viaircorp.com/sealedpswitches.html
Sealed Pressure Switches
P/N 90212 - 85 PSI On / 105 PSI Off (30-Amp)
P/N 90217 - 110 PSI On / 145 PSI Off (30-Amp) - I believe this switch would be OK for a GMC
P/N 90218 - 140 PSI On / 175 PSI Off (20-Amp)
P/N 90219 - 140 PSI On / 175 PSI Off (30-Amp)
P/N 90220 - 165 PSI On / 200 PSI Off (20-Amp)
P/N 90221 - 165 PSI On / 200 PSI Off (30-Amp)
P/N 90223 - 90 PSI On / 120 PSI Off (30-Amp)
P/N 90227 - 110 PSI On / 145 PSI Off (30-Amp)*
For 12-Volt and 24-Volt systems. Sealed for moisture resistance.
Tolerance is +/- 5% of specified pressures.
Included Parts: - 1/8" (M) NPT Port Fitting
- 1/4" (M) NPT Port Fitting* (P/N 90227 only)
Which pump did you install and which switch did it come with?
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: John Heslinga
Hi All:
Thank you for your input!
Yes There are a lot of variables that will make differences in the pressure needed to make raise the coach to its limits (fully
compressed Shocks) So too, there is some differences in the actual amount range of mothin between coaches. I was not looking for a
lot of accuracy but having a range of pressures that other owners were experiencing (If they were paying attention to installed
Gauges during different states) The small amount of pressure that are in gas filled shocks really do not make any lift difference in
any vehicle. I have never had any difficulty compressing a brand new shock (Im not very strong anymore) so that will not do very
much in lifting the coach. The pressure and nitrogen is to stop aeration and cavitation, not lift. The Gas is usually in a bag to
separate the oil from the gas too.
Thanks Gene for the link on Air Systems. I had not seen it before, I am in the middle of doing many of the upgrades now and that is
the biggest reason I need the information.
I've installed a new Viair compressor with fresh electrical support, Tank, and outlets. The Viaire comes with a pressure switch
that is set for 200 PSI. (non settable) That's too much for an OEM Bag. (Certainly put it at risk) Miguel and JimB Stated that
they seldom use air tanks and just use the compressor. (are they using the Viaire Pressure Switch? HMMM) Putting all of this
together, Im trying to make some decisions on the kinds of pressures I should run in my system. (I'm using an adjustable pressure
switch) I imagine that pumping the bags with 200 PSI while not paying full attention to what's going on would set up a bad
situation
I'll Take this information and make some decisions.
Thanks again everyone!!
Link
http://www.gmcmhphotos.com/photos/discussion-photos/p58151-air-control.html
John and Cathie Heslinga
1974 Canyonlands 260
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: What Is Bag Pressure at max height. [message #279425 is a reply to message #279343] |
Tue, 09 June 2015 10:07 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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ob
RE.Pressure switches and Compressor:
I have a Viair 480C as well (C just means chrome) I was able to purchase it in a package of two for a very reasonable price while it was on sale. (I installed the other in another coach because we bought the kit together) the Viair comes with the 165 psi on / 200 psi off pressure switch. (Im not using) The 480 is also 100% duty cycle at 200 psi.
I've put a new stainless tank in with a 175 psi safety blow off valve. (Yup the compressor will blow it off if allowed to continue running.)
Jim Bounds Made a convincing case that using the 480 is not necessarily an ideal choice and the smaller model is better suited to the coach needs. However: I had already had the 480 when I heard his case and it was quite a bit cheaper in the two pack kit on sale. (I think they were clearing them out) I also have a healthy electrical system and can maintain and repair it as needed.
One of the things I noticed before hand was that the old compressor and tank, while working fine, (getting slow and rusty) was always doing what I think you are having problems with. The kick in pressure being lower was not enough to lift the coach sometimes. I had to drop it some first to drop pressure in the tank to the kick in pressure so the compressor would come on and lift. (I had no pressure guages) But now rather than filling 2 large "Balloons", the third (tank) needed filling too in order to lift the coach. This increased the fill time significantly. (I'm sure this is why Jim B and Miguel were taking the tank out of the equation )
Because the tank supply pressure is so close to the operational pressures, it really is doing very little in the system when lifting the coach. During travel, the bag operational pressures are much lower and the higher pressure tank can now take a roll in supplying the volume of air needed for the cycling height valves.
The OEM pressure switch was still in good shape and adjustable. I can now increase the tank pressure to make it provide better operational supply. (A new tank to keep things safe) However: higher pressures in the bag side of the system are not ideal because they create stresses on the bags.
So far: I've set the switch to 150 with an on of 125. Thanks to Bob D. Who states his is 120 full up and 90. I think this will give me the muscle to lift whenever I need. I still need to pay attention because I really do not want much more than 120 in the bags. (Or about that much depending on the variables stated)
I'm thinking of increasing the tank pressure (now that I have the compressor to do it) and putting in a regulated supply to the Bag system. This way I can have the tank become a more useful source of air for the bags. I have not thought that out too much, but needed this info as part of that thought process.
One of the things Ive noticed, is that the compressor is not as fast as I had imagined. You allude to that in the 0 to 90 statement. Its not a lot faster than the OEM was. But way higher pressure capabilities
Im pretty happy with the wsy it works though. In both applications it improved performance of the system significantly.
When I installed the system I put in a 40 amp breaker, relay, and 8 ga wires to the compressor. The control side of the relsy has a disable switch and is connected to the ignition system so it will only turn on when the ignition is On.
Im going to be building an electronic 15 to 30 sec delay, so that the compressor will not come on while the engine is starting. Here is the electrical supply and support for the compressor and others.
http://www.gmcmhphotos.com/photos/discussion-photos/p58154-electrical-supply.html
Thanks so much for the information Rob!
Best Regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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