Home » Public Forums » GMCnet » Replacing air bag system
| Re: [GMCnet] Replacing air bag system [message #248129 is a reply to message #248093] |
Mon, 21 April 2014 22:59   |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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| Bob de Kruyff wrote on Mon, 21 April 2014 17:04 |
One system (remote) is open loop in that there is no feedback to re-adjust to where you thought it was, while the OEM system is a closed loop. However, neither is that precise that it probably isn't worth arguing about. I think the remote system is a good alternative for a lot of people, but since I have a working system, I'll try to keep it that way.
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Dang, did I say I wouldn't post again?
Actually the pressure only system does the wrong thing when the load changes.
This means the more things change the worse they get.
For example...
In the pressure controlled system:
Set the pressure, say 80 lbs
Then load the coach with fuel and water, groceries, luggage and 6 people.
The extra weight makes the rear end sag.
It also increases the pressure in the bags due to the greater weight.
This tells the pressure controller to dump air, causing the rear to sag even more.
In a height controlled system the saggy rear would tell the controller to increase air pressure which would bring the height back at least closer to tolerance.
I know it works, if I stand on MY rear bumper I see it readjust.
It goes back up. Yes you have to stand there for more than 20 seconds.
Is it a perfect system? well it was designed in the 70s but it does better than no controller.
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Replacing air bag system [message #248130 is a reply to message #248129] |
Mon, 21 April 2014 23:08 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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| Keith V wrote on Mon, 21 April 2014 21:59 |
| Bob de Kruyff wrote on Mon, 21 April 2014 17:04 |
One system (remote) is open loop in that there is no feedback to re-adjust to where you thought it was, while the OEM system is a closed loop. However, neither is that precise that it probably isn't worth arguing about. I think the remote system is a good alternative for a lot of people, but since I have a working system, I'll try to keep it that way.
|
Dang, did I say I wouldn't post again?
Actually the pressure only system does the wrong thing when the load changes.
This means the more things change the worse they get.
For example...
In the pressure controlled system:
Set the pressure, say 80 lbs
Then load the coach with fuel and water, groceries, luggage and 6 people.
The extra weight makes the rear end sag.
It also increases the pressure in the bags due to the greater weight.
This tells the pressure controller to dump air, causing the rear to sag even more.
In a height controlled system the saggy rear would tell the controller to increase air pressure which would bring the height back at least closer to tolerance.
I know it works, if I stand on MY rear bumper I see it readjust.
It goes back up. Yes you have to stand there for more than 20 seconds.
Is it a perfect system? well it was designed in the 70s but it does better than no controller.
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I agree Keith. My system adjusts if I walk from the front to the rear so it is quite sensitive. When I go camping lot's of supplies and gear comes and goes during the week--and the thinking that weight is insignificant is not true--at least in my case. However, I liken this argument to whether you want to set the temperature in your house or car or just open and close the window once in a while. I've always felt that you control the issue that is important to you directly--not through some other influencing factor. I suppose some of us like a thermostat in our vehicles, while others would be happy with a manual valve that gets it close part of the year.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Replacing air bag system [message #248149 is a reply to message #248130] |
Tue, 22 April 2014 02:35 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Years ago at rally I visited Arch in his coach. I walked inside and stood in the doorway while he was finishing something sitting at this PC. Suddenly something made a running noise and I said "What's that?" He sad it was the leveling system readjusting because of my added weight (200 pounds) to the coach. He said he was going to fix that some day by turning off power to the system when the coach was parked.
I tried the same thing one mine by leaving the key on and sure enough it changes (re-levels the coach after a 15-30 second delay. I also notice mine changes the leveling when I leave an Interstate for a county 2 lane highway that has more taper.
I do not monitor the pressure. That is unimportant to me, but I do hear when the compressor kicks in. It seldom turns on if I am cruising a 4 lane interstate highway. I like the built in delay that keeps it from readjusting on short term highway differences like crosswinds, bridges, tunnels, and curves.
I do have my rear ride height set correctly. It took several iterations of driving and adjusting to get it to settle at the correct height. I feel this is due to the dead band area of the leveling switches.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Replacing air bag system [message #248159 is a reply to message #248149] |
Tue, 22 April 2014 08:26 |
Chris Grant
Messages: 22
Registered: February 2014
Karma: 0
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Junior Member |
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Has anyone looked at putting a pair of infrared distance sensors in the rear of the coach to either provide an electrical input in lieu of the height control valve or with a cockpit display to optimize the pressure control method (ie set your static pressure to get close to desired ride height, but then adjust the pressure as the sensor reading changes). Sharp makes an infrared distance sensor that reads from 4" to 30" although the output is most linear in the mid band from 12" to 20". These things cost about $20 a pop. I'm thinking about setting up a couple on my birchaven with a cockpit readout, but with the existing height control valves still doing the work for the time being to assess reliability and accuracy before considering a conversion to an optical height control system. There are more expensive laser based sensors that are 1200 psi wash down rated, but I can buy 15 of these for the price of one of those.
Chris
All typos, misspellings, grammatical and/or factual errors are property of Apple, inc. and the iPhone virtual QWERTY keyboard.
> On Apr 22, 2014, at 3:35 AM, Ken Burton <n9cv@comcast.net> wrote:
>
>
>
> Years ago at rally I visited Arch in his coach. I walked inside and stood in the doorway while he was finishing something sitting at this PC. Suddenly something made a running noise and I said "What's that?" He sad it was the leveling system readjusting because of my added weight (200 pounds) to the coach. He said he was going to fix that some day by turning off power to the system when the coach was parked.
>
> I tried the same thing one mine by leaving the key on and sure enough it changes (re-levels the coach after a 15-30 second delay. I also notice mine changes the leveling when I leave an Interstate for a county 2 lane highway that has more taper.
>
> I do not monitor the pressure. That is unimportant to me, but I do hear when the compressor kicks in. It seldom turns on if I am cruising a 4 lane interstate highway. I like the built in delay that keeps it from readjusting on short term highway differences like crosswinds, bridges, tunnels, and curves.
>
> I do have my rear ride height set correctly. It took several iterations of driving and adjusting to get it to settle at the correct height. I feel this is due to the dead band area of the leveling switches.
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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| Re: [GMCnet] Replacing air bag system [message #248166 is a reply to message #248159] |
Tue, 22 April 2014 09:55 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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| Chris Grant wrote on Tue, 22 April 2014 08:26 |
Has anyone looked at putting a pair of infrared distance sensors in the rear of the coach to either provide an electrical input in lieu of the height control valve or with a cockpit display to optimize the pressure control method (ie set your static pressure to get close to desired ride height, but then adjust the pressure as the sensor reading changes). Sharp makes an infrared distance sensor that reads from 4" to 30" although the output is most linear in the mid band from 12" to 20". These things cost about $20 a pop. ...
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Chris, if you can set up the measurements between the upper arms (below the air bag), you can easily correlate that to ride height. If you have a readout that shows ride height, having the wireless system makes it easy to manually control ride height from the drivers seat (or elsewhere). I guess you could use ball valves to do much the same thing. Knowing the correct ride height is the hard part. Raising and lowering the coach is just air.
Interesting thread. I'm not trying to take away from the wireless system. I can see how it can work effectively. I still prefer the auto system but if mine didn't work, I'd probably feel differently.
It is kind of interesting that with all the talk over the years about making sure the ride height is RIGHT ON for alignment and proper handling, some say it apparently doesn't really matter that much. Can't say that I understand that although I have utmost respect for some of those saying just that. I'm too new at this to have anything more than an opinion. 
I will say this....operator head space is important. On the way home from Montgomery Tx one night, I was in a hurry to get on the road. I noticed the coach didn't drive that well but attributed it to some pretty serious side winds. Several hours later, we stopped for gas and I realized I had not turned on my compressor when we pulled out. The ride height was what I had set on the campground slab the previous night. Drove much better after the compressor was on and the system did it's thing. Even a good working Electro Level 1 can't fix stupid I guess.  
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Replacing air bag system [message #248167 is a reply to message #248166] |
Tue, 22 April 2014 10:03 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
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Kerry - I wasn't aware that you could turn the compressor off, at least without pulling a wire or fuse. Is that something you added or did your coach come like that?
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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| Re: [GMCnet] Replacing air bag system [message #248171 is a reply to message #248167] |
Tue, 22 April 2014 11:31 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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| Otterwan wrote on Tue, 22 April 2014 10:03 |
Kerry - I wasn't aware that you could turn the compressor off, at least without pulling a wire or fuse. Is that something you added or did your coach come like that?
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A PO added it. I have a little rocker switch right beside the EL1 switches. It has a blue light in it that indicates it 'on'. Dang light is so bright that at night, I have to put a piece of opaque tape over it.
Mine leaks down over a few weeks and I don't want the compressor running at night so if it had not been already done, I'd have done it. I almost always set the rear suspension on wooden blocks at night so it doesn't move around when we're sleeping.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Replacing air bag system [message #248179 is a reply to message #248171] |
Tue, 22 April 2014 11:55 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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normally runs off of the acc switch
so cannot run with the engine off
erf
On Tue, Apr 22, 2014 at 9:31 AM, Kerry Pinkerton <Pinkertonk@mchsi.com>wrote:
>
>
> Otterwan wrote on Tue, 22 April 2014 10:03
> > Kerry - I wasn't aware that you could turn the compressor off, at least
> without pulling a wire or fuse. Is that something you added or did your
> coach come like that?
>
>
> A PO added it. I have a little rocker switch right beside the EL1
> switches. It has a blue light in it that indicates it 'on'. Dang light is
> so bright that at night, I have to put a piece of opaque tape over it.
>
> Mine leaks down over a few weeks and I don't want the compressor running
> at night so if it had not been already done, I'd have done it. I almost
> always set the rear suspension on wooden blocks at night so it doesn't move
> around when we're sleeping.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
> _______________________________________________
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--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
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Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Replacing air bag system [message #248190 is a reply to message #248181] |
Tue, 22 April 2014 14:01 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| hal kading wrote on Tue, 22 April 2014 11:04 |
What am I missing? With EL-1 the compressor won't run with the ignition off, nor will it run with the center switch in hold and the raise/lower switches in the neutral center position, IIRC.
Hal Kading 78 Buskirk Las Cruces NM
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Nor will the EL ii
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Replacing air bag system [message #248192 is a reply to message #247891] |
Tue, 22 April 2014 14:12 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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That is just the way the PO wired it up...or rather had it wired up. There was a soldered connection and since he only owned a hacksaw, duct tape, and a crescent wrench, I'm sure it wasn't him doing the actual work.
I've since wired it to the ACCY but it was hot anytime it was 'ON'.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Replacing air bag system [message #248194 is a reply to message #248181] |
Tue, 22 April 2014 14:12 |
Chris Grant
Messages: 22
Registered: February 2014
Karma: 0
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Junior Member |
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For EL-1, the center switch in hold will not allow the compressor to turn on regardless of leveling valve position (coach height). You can still run the compressor in this configuration by toggling the right or left raise/lower switch for campsite leveling or too bump the back end up when driving around town to get less positive caster (more reactive steering).
I've changed from a Dana compressor to a Viair 450c in my Birchaven (rear mounted compressor) so I'd really like to get a cockpit indicator light to see when the compressor is running; it's too quiet in the back to hear over engine and road noise.
Chris Grant
76 Birchaven
Jupiter, FL
All typos, misspellings, grammatical and/or factual errors are property of Apple, inc. and the iPhone virtual QWERTY keyboard.
> On Apr 22, 2014, at 1:04 PM, Hal Kading <halkading@fastwave.biz> wrote:
>
>
>
> What am I missing? With EL-1 the compressor won't run with the ignition off, nor will it run with the center switch in hold and the raise/lower switches in the neutral center position, IIRC.
>
> Hal Kading 78 Buskirk Las Cruces NM
>
>
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| Re: [GMCnet] Replacing air bag system [message #248208 is a reply to message #248192] |
Tue, 22 April 2014 17:26 |
sgltrac
Messages: 2797
Registered: April 2011
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Shut off valves to throw after you level and u won't need to screw with it til your driving home Kerry. Sometimes I get part way there before I remember to open them again. 😁
Todd Sullivan
Sully
77 royale
Seattle
> On Apr 22, 2014, at 12:12 PM, Kerry Pinkerton <Pinkertonk@MCHSI.com> wrote:
>
>
>
> That is just the way the PO wired it up...or rather had it wired up. There was a soldered connection and since he only owned a hacksaw, duct tape, and a crescent wrench, I'm sure it wasn't him doing the actual work.
>
> I've since wired it to the ACCY but it was hot anytime it was 'ON'.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as an Art Deco car hauler
> _______________________________________________
> 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] Replacing air bag system [message #248793 is a reply to message #248443] |
Tue, 29 April 2014 11:58 |
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Tangerine
Messages: 192
Registered: February 2004
Location: Livonia, MI
Karma: 0
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Senior Member |
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On 4/25/2014 9:41 AM, Todd Sullivan wrote:
> Thinner steel. Zero offset. No plating. Same price.
>
> Todd Sullivan
>
> Sully
> 77 royale
> Seattle
>
>> On Apr 25, 2014, at 3:48 AM, Rick Drummond<randts.gmc@gmail.com> wrote:
>>
>> How does this one compare physically with the Sully system? They look similar.
>>
>> Rick
>>
>> Rick&Tammy Drummond
>> Prior Lake MN
>> '74 (re)Painted Desert
>>
>>> On Apr 24, 2014, at 10:37 PM, Randy<Acrosport2@hotmail.com> wrote:
>>>
>>>
>>>
>>> I like this from JimK
>>>
>>> http://www.appliedgmc.com/prod.itml/icOid/1037
>>>
>>> Holds air for months
>>> --
>>> Randy
>>> 1973 26' Painted Desert
>>> Ahwatukee (Phoenix) AZ
Where can I see the Sully air bag? The Mono bag from JimK worked great.
At first it was squirrely to drive. Then I realized that the new bag
only needed 70# on the right side of the coach and the old original bag
on the left side, took 90# to achieve the ride height I wanted. So I
let some air out of the old bad and it made a world of difference. Even
with that side a little low to the ground. I should receive the other
bag today and will be installed this weekend.
Gary W. Mills (Livonia MI)
. ___________
./_][__][] []| 1974 GMC M/H
.*O-------OO-* Painted Desert
"Tangerine Dream" W/New Frame
./___\.
(o\_!_/o) '74 Love Bug
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1974 GMC 260
Tangerine Dream
Livonia Michigan
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