Home » Public Forums » GMCnet » [GMCnet] Got Double Trouble weighed at a CAT Scale
| [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181757] |
Sat, 25 August 2012 19:26  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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G'day,
Got Double Trouble weighed at a CAT Scale yesterday:
Weight # 1 - Pulled up with the front wheels on the front scale pad (Steer Axle) and the rear wheels were on the second scale pad
(Drive Axle)
Steer Axle = 4400
Drive Axle = 8140
Total = 12540
I was sitting in the drivers seat and weigh 250 (+/-); Helen was NOT in the pax seat (she weighs 135 (+/-).
Weight # 2 - Pulled up so that the driver side wheels were off the scales completely. The passenger side front wheel was on the
second scale pad (Drive Axle) and the rear wheels were on the third scale pad (Trailer Axle)
Drive Axle = 2320
Trailer Axle = 3900
Total = 6220
I was not in the coach.
Weight #3 - Pulled up so that the passenger side wheels were off the scales completely. The driver side front wheel was on the
second scale pad (Drive Axle) and the rear wheels were on the third scale pad (Trailer Axle)
Drive Axle = 1740
Trailer Axle = 4260
Total = 6000
I was not in the coach.
Compared to the late GMC specs (I chose these cause the data looked better) it looks like this:
Specifications Double Trouble
Front curb = 3750
Front cargo = 750
& Pax Load
Total = 4500 4400
Rear curb = 6820
Rear cargo = 1180
& Pax Load
Total = 12,500 12540
Right / left imbalance spec:
Front: 250
Rear: 600
Double Trouble
Front: 2320 - 1740 = 580
Rear: 4260 - 3900 = 360
This makes sense because:
I have the five draw tool box and a lot of other heavy crap under the dinette.
The water tank was full.
Furthermore I had to order an extended length pork chop adjustment bolt from JimK. When John and I set the front ride height the one
on the passenger side was almost out of threads whereas the one on the drivers side was WAY further out!
I think he slight difference in numbers is due to the fact that did not center the wheels to be weighed in the middle of the scales
when I weighed each side.
They charged me $9.50 for the first weight and $1.00 for each additional weight.
Questions for the GMC Brain Trust:
1) Did GMC actually do anything to the suspension system to up the GAWR and GVWR or just "pencil whip it?"
2) Does my supposition about not having the wheels centered on the scales hold water?
3) Does anyone think there is anything to be gained by weighing the individual axles one by one?
4) Since this is cheap to do I think I'll try it again with both Helen and I in the coach and the wheels as close to the center of
the scales as I can get them when I do the side weights. I don't like the 580 front differential; that delta would drop with both of
us in the seats and it would be what it REALLY is.
Regards,
Rob M.
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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: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181780 is a reply to message #181778] |
Sat, 25 August 2012 22:27  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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| Robert Mueller wrote on Sat, 25 August 2012 22:06 |
G'day,
I thought of something else while I was in the shower before dinner.
Would it be better to position the coach so that it was 1/2 off and 1/2 on the scales? I'll say that another way as it is confusing.
Should the center of the coach be positioned directly over the edge of the scale platform?
Regards,
Rob M.
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Theoretically it should make no difference. The scale should accurately record weight no matter where that weight is applied on the scale. Where the GMC is positioned makes no difference either. Think of Statics class and do the diagram. Now as a practical matter I would want to get the wheels as close as possible to the center of the scale.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181789 is a reply to message #181786] |
Sun, 26 August 2012 00:17 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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You have the high weight on the opposite corners of the coach. This is what happens when you try to adjust the ride height without checking the weight on each wheel.
You have the passenger side torsion bar cranked up too much. That is raising the weight on the right front and left rear. If you crank out some of that tension the right front, some of the weight will transfer to the left front. Do not worry about the rears as the automatic height adjustment will follow and some of that left rear weight will also transfer to the right rear.
I like to see them adjusted so the side to side weight difference is the same side. (meaning if the left front is heavy, then the left rear should also be heavy.)
When Colonel Ken gets in here and tries to argue with my conclusions or methods do not pay any attention to him. We have had this discussion many times in the past.
It OK to just say "Yes sir, Colonel Sir" (his last name is Sir)
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181803 is a reply to message #181778] |
Sun, 26 August 2012 02:57 |
Adrien G.
Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624
Karma: 1
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Senior Member |
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Rob,
Questions for the GMC Brain Trust:
1) Did GMC actually do anything to the suspension system to up the GAWR and GVWR or just "pencil whip it?"
2) Does my supposition about not having the wheels centered on the scales hold water?
3) Does anyone think there is anything to be gained by weighing the individual axles one by one?
4) Since this is cheap to do I think I'll try it again with both Helen and I in the coach and the wheels as close to the center of
the scales as I can get them when I do the side weights. I don't like the 580 front differential; that delta would drop with both of
us in the seats and it would be what it REALLY is.
On question #3.
The Load-Cell scales in use are calibrated and certified to read the load with negligible percent variation, (in another word, I wouldn't worry about it) at any point (location) on that platform.
Where I work, I have watched the process of scale calibration many times.
FWIW
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
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| Re: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181814 is a reply to message #181789] |
Sun, 26 August 2012 06:43 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Sir don't disagree none with yo' conclusions, just, sometimes, the methods.
Ken H.
On Sun, Aug 26, 2012 at 1:17 AM, Ken Burton wrote:
>
> ...
> When Colonel Ken gets in here and tries to argue with my conclusions or
> methods do not pay any attention to him. We have had this discussion many
> times in the past.
>
> It OK to just say "Yes sir, Colonel Sir" (his last name is Sir)
> --
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181815 is a reply to message #181757] |
Sun, 26 August 2012 06:47 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Rob,
In the midst of my front end problem I found somewhere that there were 4000
ft-lb and 4200 ft-lb torsion bars for the GMC. That change might have
corresponded with the increase in GVW. Don't bother to ask me where I saw
that.
Ken H.
On Sat, Aug 25, 2012 at 8:26 PM, Rob Mueller wrote:
> ...
> 1) Did GMC actually do anything to the suspension system to up the GAWR
> and GVWR or just "pencil whip it?"
> ...
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181829 is a reply to message #181827] |
Sun, 26 August 2012 10:18 |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
Karma: -41
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Rob:
Water tank status?
Fuel status?
Just curious. Those two could account for a lot of the 12,540.
Dolph
On Aug 26, 2012, at 11:07 AM, Rob Mueller wrote:
> Armand,
>
> Thanks for the link, I'll print it out and look it over.
>
> Regards,
> Rob M.
>
> -----Original Message-----
> From: Armand Minnie
>
> Rob, did you look at the data from our weigh-in at the Casa de Fruta rally? There were lots of cases of left-right imbalance at the
> front. It is at http://gmcws.org/blog/?p=781
> --
> Armand
>
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| Re: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181830 is a reply to message #181786] |
Sun, 26 August 2012 10:24 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Hal,
Yes, I do have air pressure gauges on the OEM airbags; I'll take a look at them and post what they read. They are made in China so
their accuracy probably isn't that great. I bought a pair to replace them from McMaster Carr, they were Ashcroft and I figger'd they
were made in the USA - NOT - made in Brazil! I have yet to install them.
I should have mentioned that just before I left Houston John Sharpe and I reset the ride height to meet the manual specs. When I got
to Billy Young's place I checked it and it was a bit high on the driver side so I lowered it and both the front sides were in spec.
I have my torsion bar unloading tool with me and if time permits I can play with this at Amana. Is anyone bringing any scales?
I should have noted the following in my original message:
Under the front dinette seat I have three torque wrenches, the wheel bearing tool, another tool box with timing light, compression
gage, vacuum gage, drill set, tap and die set, and other misc tools. Then there's the six plastic divider boxes full of nuts, bolts,
screws, electrical stuff, and lots of miscellaneous bits and pieces. There's a soldering iron and a HF Dremel tool. I reckon
carrying all this crap is why the passenger side pork chop bolt is screwed in so far.
Under the rear dinette seat I have:
http://www.gmcmhphotos.com/photos/g5795-tool-box-installation.html
What's not in the picture above is the 1/2" electric impact wrench, the 1/2" battery powered drill (with three batteries), the 4"
grinder, Mapp gas bottle and small electric screwdriver.
One more thing - Double Trouble drives perfectly; if I am in the left lane of a three lane highway it will slowly creep off to the
left slowly, if I am in the middle lane it will go straight ahead, and if I am in the right lane it will creep off to the right
slowly.
Regards,
Rob
-----Original Message-----
From: Hal Kading
Rob,
Looks to me like you have diagonal unbalance. Passenger front and driver rear total 6560# and driver front and passenger rear total
5640# for an difference of 920#. Do you have air bag pressure gauges? It would be interesting to back off the passenger side torsion
adjusting bolt some and tighten the driver side an equal number of turns to see what that does to the bag pressures and weight
imbalance.
Hal
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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: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181832 is a reply to message #181803] |
Sun, 26 August 2012 10:29 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Adrien,
Thanks for this info.
Regards,
Rob M.
-----Original Message-----
From: Adrien Genesoto
Rob,
On question #3.
The Load-Cell scales in use are calibrated and certified to read the load with negligible percent variation, (in another word, I
wouldn't worry about it) at any point (location) on that platform.
Where I work, I have watched the process of scale calibration many times.
FWIW
Adrien
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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: [GMCnet] Got Double Trouble weighed at a CAT Scale [message #181833 is a reply to message #181812] |
Sun, 26 August 2012 10:33 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Steve,
You're right about the diet and loosing weight but I think 4,000 lbs is a bit too much, I need to shed about 50 or so.
Quite frankly I was surprised that Double Trouble came in at 12,540 total with me in the driver seat. If Helen had been on board
that would have gone up to 12,675.
Regards,
Rob M.
-----Original Message-----
From: Steven Ferguson
Looks like you need to go on a diet Rob and lose about 4,000 lbs:>)
Steve
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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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