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Weighty New Years Resolutions


Dollytrolley

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Well I had intended to make much earlier thread about the methods I use to keep my weight and balance in check and since 2016 is about to end I guess I better get in gear.....

 

Here is a method that I use to compute truck and trailer weight and balance......other methods exist but this method is pretty simple so..... beings simple I use it.

 

Before I compute weight and balance I need a basic layout of the truck and trailer consisting of :

 

TRUCK:

1. Zero Datum Line

2. Steer axle datum

3. Front drive axle datum

4. Rear drive axle datum

5. Fifth hitch pin datum

6. Ball hitch datum

7. Fuel tank(s) datum and capacity in gallons

8. Each cargo bay datum

9. Each seat datum

10, Datum for other mass variables such as water tanks etc.

 

Now before I start the basic truck weight and process I like to prepare the truck as the BASE TRUCK without any tools or cargo of any kind, EXCEPT I do fill all fuel tanks FULL and all other gear boxes and coolants full.

 

As Trey and Susan will suggest it is best to weigh each wheel position if feasible, if not feasible weigh each axle position, or steer and then tandem.

 

Once you have scaled the BASE TRUCK you are then able to calculate the BASELINE truck weight and balance.

 

Here is a example BASELINE truck weight and balance calculation:

 

ITEM STATION (inches) WEIGHT (Lbs) MOMENT Center Gravity

 

1. Steer axle 0" 12160 0

2. Front Driver 283 7800 2207400

3. Rear Driver N/A 0 0

________________________________________________________________________________________

19960 2207400 110.59 "

 

So IF my basic weights AND Datum measurements are correct we should be able to set the above truck down on a knife-edge sawhorse 110.59 inches aft of the front axle and the truck should in still air set level in balance with the wheels off the ground.

 

60.92% of the truck weight is on the steer axle

39.08% of the truck weight is on the drive axle

 

Ok now what happens to our BASELINE truck IF we hitch up a trailer with 7860 pounds of pin load at our hitch datum of 335 inches aft of the steer axle (52 inches aft of rear axle)?

 

ANSWER:

ITEM STATION (inches) WEIGHT (Lbs) MOMENT Center Gravity

 

1. Steer axle 0" 12160 0

2. Front Driver 283" 7800 2207400

3. Rear Driver N/A 0 0

4. Hitch Pin 335" 7860 2633100

_______________________________________________________________________________________

27820 4840500 173.99 "

 

At a Center of Gravity 173.99 inches aft of the steer axle at a gross weight of 27,820 Lbs we have 61.48% of the gross weight on the drive axle (17,104 Lbs), and 38.52% of the gross weight is on the steer axle (10,716 Lbs).

 

To Calculate Moment multiply weight by datum

 

To Calculate Center of Gravity add up all item weights and then add up all moments and then divide the sum of the moments by the total gross weight.

 

Simple math.....

 

Ok children..... check my math....

 

Next post lets do the trailer weight and balance......

 

Drive on.......( where did I put the calculator??)

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yeah looks simple (I glossed over at step 3) heheheh ;-)

Shucks Jeff are you related to....."Ms. Sunshine"....she was chief dispatch for a lowlife outfit I would do a gig for when legal work was scarce......"Ms. Sunshine" liked girls and disliked male pilots and seemed to hate me with no seniority in particular.....

 

I would slink into dispatch....."Ms Sunshine " would look up......her Eyes would GLAZE over and she would take a looong drag on a foul cigarette and mutter loudly......"you again.....sooo....today are you going to be the answer to a problem...or....are YOU just going to be a PROBLEM"......gulp

 

Ya know Jeff you do bring up a good point .......truck a trailer weight and balance calculations can be as exciting as discussing the finer points of 20 year tax depreciation of storage unit buildings.......glaze time

 

Hang in there Jeff the exciting time is calculating the trailer weight and balance.....so many more opportunities to mess with more math.....strap in tight and hang on......it will be like "Ms Sunshine" finding me a load of venomous snakes to haul.....

 

Drive on......(glaze on.....)

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What about CG height? I wanna know your CG height! Get to work buddy! :wacko:

Hush yo mouth child....yawll due ya homework an don't SAS me none....u bee da vertically challenged child hear...here...so when ya get the very CG then I wone the first six orders of the cross-coupling on my desk by first coffee brakee tomorrow.....get honkn ...

 

Drive on.. .(Due I have to dew all the ciphering around here....hear)?

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I got you datum right here :huh:

 

Steve

Shucks Mr. S. Ya ain't seen one datum-thing till we attack the datum-5ther-trailer.....

 

Of course we gotta sit on our thumbs till that datum-other-steve cranks out the cross-coupling ciphering on da truck.... overpriced and underworked....

 

Drive on....(datum trailer looks like a lotta mass)

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Steve was pulling my chain about the vertical CG....I sold him some "heavy water" some months back and he called me in the carpet like grumpy Sr. Engineers are prone to do......if he had any clue how uncredentialed I am he would cry himself to sleep for picking on my mangy hide.

 

Steve may have a suffered some engineering abuse at a early stage in his career in that he seemed to hang around the Indy car crowd and those geeks seem to think that any C G higher than a snakes belly in a wagon rut is a C G too high.

 

Now here this.....while I may be sorely uncredentialed this does not keep me from being a EXPERT in Vertical C G Extreameee Operations.......As a young copilot in Grump's 54 needle nose KW I had the thrilling Dynamic experience of having the Vertical C G change places with one of the various other C G'$ and of course having dirt coming through the wing window and then me head butting out the passenger side windshield and cutting my chin on the radiator cap was a nice conclusion on my Vertical C G lesson for the day.....so you see after mastering the Vertical C G cause and effect thingy I have moved on to the more mainstream longitudinal C G thingy and let the Sr Engineers tackle the easy vertical stuff.....

 

Next someone might mention the advanced RV trailer suspensions and tires and brakes so I am sure with these advanced advantages a bit too high V C G can be nothing more than a minor problem at speeds under 10 mph....

 

So while Steve is getting the V C G under control, I'll get ready to do the plane-Jane longwise C G thingy on the trailer.....

 

Drive on....(my vertical C G is so high it has snow on it)

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Steve may have a suffered some engineering abuse at a early stage in his career in that he seemed to hang around the Indy car crowd and those geeks seem to think that any C G higher than a snakes belly in a wagon rut is a C G too high.

 

 

Well, In my world, any CG above the water line meant you're gonna die by rolling over in a turn.....

Boats only go fast in a straight line....

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Well, In my world, any CG above the water line meant you're gonna die by rolling over in a turn.....

Boats only go fast in a straight line....

Boy Jim you sure got that right about boats in general......

 

Shucks we had a several thousand HP boat that would become unstable at high speed if the vertical C G got too high above the waterline so the Grumpy OLD N Architect on staff fixed the darn boat.....he had a brass placard engraved and riveted at the wheel house that said "VESSEL IS LIMITED TO 5.6 KNOTS WHEN FUEL BUNKER IS BELOW THIRTY TONS"......fixed the "High-speed dutch roll".

 

We had a gig to stand up and transport a C G load of 139,000 lbs at 120 ft above the waterline and we had to ballast the sectional barge 5 ft and limit turns to FOUR knots or less....We did blow past 4 Knots a couple of time and no one died but we did burn through a fair amount money calculating that the high C G would not kill too many folks.

 

I agree turns are bad juju.....when I rode the old KW that turned over I never imagined anything could hit the ground that hard....

 

Float on.......(Don't stand up in a canoe ....)

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For all you folks with a Vertical C G fetish......get out your REALLY BIG truck jack and wheel scales and then go to the online Vertical C G calculator page at : Robrobinette.com

 

Don't let the truck fall on you while you do the testing......Vert C G testing is about the most fun you can have with your clothes on.....

 

Drive on......(How far can you jack your truck up before it falls)

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Before I compute weight and balance of the trailer I need a basic layout of the trailer consisting of :

 

TRAILER:

1. Zero Datum Line (Hitch Pin or Ball

2. Forward axle datum and capacity

3. Second axle datum and capacity

4. Third drive axle datum and capacity

5. Each cargo bay datum

6. Main fresh water tank & gallons capacity

7. Aux fresh water tank & gallons capacity

8. Grey water tank datum & gallons capacity

9. Black water tank datum & gallons capacity

10, Propane tanks datum and gallons capacity

11. Fuel tank(s) datum and capacity in gallons (Toy Haulers)

12 Bike or motorcycle rack(s) datum

13 Copy of the trailer DOT spec sheet

14 Installed trailer tire size and load rating in pounds

15 Wheel position weights if known AND configuration of trailer when wheel position weighing occurred.

16 Hitch pin or ball weight when wheel position weighing occurred.

 

Next post we will prep to calculate the trailer BASELINE Weight and Balance.

 

(I was sorta expecting someone to call me out for using the term "datum" to define the position of a item on the layout of a vehicle when I really should reference THE datum as the arbitrary point from which "stations" are measured from....)

 

Drive on......(where is that darn trailer?)

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For those of us who fell asleep in geometry class and went directly to work after school pumping gas, this exercise cries out for some illustrations or a graphic based demonstration. Since this website isn't great for that, maybe a link to a picture website might do the trick.

Some basic definitions of the terms would also be a help to the great unwashed.

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For those of us who fell asleep in geometry class and went directly to work after school pumping gas, this exercise cries out for some illustrations or a graphic based demonstration. Since this website isn't great for that, maybe a link to a picture website might do the trick.

Some basic definitions of the terms would also be a help to the great unwashed.

 

Jeff you are as always pretty much spot on on your comments and you were a true gentleman to not bring up the well proven fact of history that I AM the worst teacher to ever mutter a word or cobble up some text and my graphics suck on my best day.

 

Maybe I am also maybe the worlds worst web searcher because the only thing that I seem to find on truck weight and balance seems to be some academic over-detailed and way over the top math infused SAE white papers that would leave Einstein scratching his head in confusion....

 

To make matters worse is that as a birdman I had to do too many weight and balance calculations daily and sometimes that can lead to complacency.....not good.....

 

Me teaching weight and balance calculations might be like asking Lance Armstrong how to ride a bicycle.....except I was never good at bike riding or taking "supplements"......

 

Maybe my next post could start at the beginning of the weight and balance curriculum instead of where I started some wher in the middle.

 

Henry mentioned recently that he was going to draw up some SolidWorks graphics for illustrating some weight and balance issues so I will defer to Henry as the master of graphics.

 

At the end of the day the thing that makes me wince is that many folks on the forum desire to know their truck and trailer weight and balance but are unable to calculate it.....

 

What really makes me wince is that it is easy to calculate weight and balance, however ......it is not easy for me to explain the methods for computing it.....

 

Ok maybe my next post I might try starting at the ......first page of the lesson.

 

Good call Jeff....thanks.

 

Drive on.......(maybe start reading on page....one)

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Sekay, that was a great video in helping understand, but I think on that last part they forgot to consider the weight of the plank on the left side. They only looked at the 500 lb amount. Obviously the plank plays into the calculation there as well.

 

On edit: Ok, caught my error. Had to watch it a second time.

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I think this is where many get confused. The CG or center of gravity is where the entire mass (weight on earth) can be considered to be applied. Imagine the board being vertical instead of horizontal. Same force (200) at same position as illustrated.

So no, they did consider the entire board on both sides of the fulcrum.

 

As Dolly said, not so easy to teach this, especially when you type with two fingers and as slowly as I do. Much easier verbally. So much for the saying, "those that can't... teach".

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I think this is where many get confused. The CG or center of gravity is where the entire mass (weight on earth) can be considered to be applied. Imagine the board being vertical instead of horizontal. Same force (200) at same position as illustrated.

So no, they did consider the entire board on both sides of the fulcrum.

 

As Dolly said, not so easy to teach this, especially when you type with two fingers and as slowly as I do. Much easier verbally. So much for the saying, "those that can't... teach".

 

So now that my disabilities in teaching have been outed and I freely admit holding down rung of the teaching ladder I will cement my legacy at the bottom......

 

Through various over-funded projects in low tech stealth methodology......I found myself with a very rare and odd FAA rating of.....Lighter Than Air-Free Balloon.....Commercial Pilot.....

 

So the FAA being the FAA REQUIRES every Instructor that teaches other pilots must obtain a.....Instructors rating by passing various classes and testing in the art of....teaching....EXCEPT Balloons.....any Commercial Pilot can just go teach without any idea or training in teaching at all....

 

So a friend of a friend introduces me to a delightful couple and both are Phd's and she is French and her father is in charge of a Paris tourist trap called the Eiffel Tower and since I have to man a booth at the Paris Air Show she has her father let me follow some of the maintenance crew into the upper reaches of the Tower that mere tourist never hope to set foot....

 

So...a few months after the Tower tour I get a call from the Phd wife telling me that she has bought her hubby something he always wanted..... a Hot Air Balloon.......AND.....would I teach him to fly it? ? ?

 

Gulp.....what do I say?

 

She was sooo French and sooo nice I said.......well maybe....sorta.

 

So they invite me over to dinner and his wall papered with degrees from Oxford, Harvard, Yale ....you name it he has lectured about.....Teaching!!

 

Well shucks this guy will only take ten minutes to teach to fly a balloon right he has been passing tests all of his life......

 

So we start flying the his balloon......sorta.....I fly and he just gazes out of the basket with a grin from ear to ear and pays almost no attention to flying the balloon and worse yet he loves to stand in the basket with his back to our direction of travel and gaze at where we came from.

 

OK flyin a balloon may not be rocket science, BUT you do need to pay attention to where you might be wondering because every so often a balloon wonders into power lines and that often kills everyone in the basket.....very bad juju.

 

About or fifth flight I was getting a bit grumpy with the lack of progress of the professor in looking where we were going so I decided to "Teach" the Teacher a "hard lesson".....

 

East of Bend we were flying along at maybe 3 mph about 50 ft above the ground and the professor was looking backwards as usual and as usual I was having to fly the darn balloon so......about a half mile ahead was a fairy wide irrigation canal and so I started a gradual descent over a large pasture and timed it right so we splashed down fairly hard into the canal much to the surprise and just a bit of anger of getting his leather trimmed basket drenched.......I burned hard and powered out of the canal and then pulled the top panel vent of the balloon and planted the bask briskly on the other side of the canal.

 

Well the professor was soaking wet and pretty miffed and I was NOT happy......

 

Professor gets out the basket and walks around in a circle for a minute looking at his wet basket.....then he said,"Well what was that stunt about?

 

I was busy gathering the balloon into a pile so that if the wind were to pick up several hundred yards would not drag HIS balloon to Boise Idaho.....

 

After I gathered the envelope into a pile it was my turn to be miffed......I put my hands on my hips and said, " That STUNT was a effort to save your life because you need to sell this damn balloon and just hire someone to give you balloon rides".

 

The Professor sat down on the ground and got a odd look on his face and then said " well you know, your right....I have no desire to learn to fly this thing .....I just love the ride so much"

 

Professor sold the balloon and then crewed and bought rides for many balloon folks and has prospered very well.

 

I "retired" from teaching and for that the world has been likely a safer place.

 

A real "teacher" would have likely kicked the professor out of class by the end of the second "lesson".

 

Ok back to ........weight & Balance....

 

Fly on......(where did all that water come from?)

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Jeff you are as always pretty much spot on on your comments and you were a true gentleman to not bring up the well proven fact of history that I AM the worst teacher to ever mutter a word or cobble up some text and my graphics suck on my best day.

 

Maybe I am also maybe the worlds worst web searcher because the only thing that I seem to find on truck weight and balance seems to be some academic over-detailed and way over the top math infused SAE white papers that would leave Einstein scratching his head in confusion....

 

To make matters worse is that as a birdman I had to do too many weight and balance calculations daily and sometimes that can lead to complacency.....not good.....

 

Me teaching weight and balance calculations might be like asking Lance Armstrong how to ride a bicycle.....except I was never good at bike riding or taking "supplements"......

 

Maybe my next post could start at the beginning of the weight and balance curriculum instead of where I started some wher in the middle.

 

Henry mentioned recently that he was going to draw up some SolidWorks graphics for illustrating some weight and balance issues so I will defer to Henry as the master of graphics.

 

At the end of the day the thing that makes me wince is that many folks on the forum desire to know their truck and trailer weight and balance but are unable to calculate it.....

 

What really makes me wince is that it is easy to calculate weight and balance, however ......it is not easy for me to explain the methods for computing it.....

 

Ok maybe my next post I might try starting at the ......first page of the lesson.

 

Good call Jeff....thanks.

 

Drive on.......(maybe start reading on page....one)

 

Maybe this sketch for the trailer will help:

 

TRAILER%20SPECS_zpsnrfdk5me.jpg

 

For additional items like more cargo bays, just measure from pin and provide the same info as noted for similar items.

 

Dave

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Maybe this sketch for the trailer will help:

 

TRAILER%20SPECS_zpsnrfdk5me.jpg

 

For additional items like more cargo bays, just measure from pin and provide the same info as noted for similar items.

 

Dave

 

Dave,

 

Very nice sketch .

 

This would be a nice way for folks to easily get a handle on defining the stations for their trailer layout.

 

Please email this to me and I could use it in my example trailer posting on the thread.....email me at: mmcdan3189@aol.com

I will email you back the spreadsheet with the truck example listing.

 

Thanks Dave

 

Drive on.......(Nice sketch)

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For most of us, a general idea of weight will work. If your fresh H2O tank holds 100gl, and you usually travel with half tanks, then for this exercise 400lb would work. Motorcycles weigh 800-1000, most fulltimers carry 2500-3000lbs of stuff in the basement, and cabinets.

We used the same idea to balance the yachts we built..... kinda hard to explain to a new yacht owner that his new pride and joy is supposed to list 5* to port...... because his wife added a Sub Zero freezer to the galley.... at the end of the build....

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