WEIGHT/BALANCE, MH AND ADDED WEIGHT ON REAR

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fredethomas

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To:  Jim Dick and Jim Johnson;

On a paper - draw a straight line rep. motorhome chassis.
Draw a wheel and axle near each end of the line = wheelbase.
Label the front as "A", the rear axle as "B."
A distance behind the rear axle draw a box to rep. the weight you are adding.  Lable it "W".

Measure the distance in inches between A and B.  Use the axle point - it is the wheel base.  For example make it 200".
Measure from the rear alxe to the center of your new load.  Call it BW distance and for example make it 100."

Now - divide BW [100"] by AB [200"]  The ratio is 50%.

Multiply you new weight by 100% +50%.  Say the new weight is 500 lbs.  It times 150% = 750 lbs.  That is the new added weight to the rear axle.
The weight on the front axle will deminish by the 250 lbs that was transferred to the rear.

Just my note : Remember you must shift some weight to the front to hold it on the road. 

Just another note which is my opinion:  Use H rated tires at max pressure on the rear and put rollers or skids on the motorcycle bracket. 

 

Jim Dick

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Fred,

I just found a website that showed the formula for measuring the effect on the rear axle. Simply stated it said:

weight of load X (wheel base +distance from rear axle to load)
--------------------------------------------------------------------------------
              wheel base

I think that's the same as what you said. Unfortunately for me the load is way too much for the rear axle.



 

Gary RV_Wizard

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I'm struggling to comprehend these formulas - it appears that the further forward the load is placed, the more weight is applied to the rear axle!  In the example, a 500 lb weight added midway between the front and rear axles (100 inches in Fred's example) adds 750 lbs to the rear axle and unloads 250 lbs from the front?  I'm obviously misunderstanding something.    The formulas seem to work for weight added behind the rear axle, but not between the axles.

Using this formula it also appears that weight added forward of the front axle would be worst of all - the distance from the rear axle is greater than the wheelbase and more than double the weight on the rear axle! 

Are these formulas only for weight added behind the rear axle?  If that was stated, I missed it.
 

Bob Buchanan

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Hi Gary:

RV Roamer said:
The formulas seem to work for weight added behind the rear axle, but not between the axles.
As you move forward of the rear axle, the distance from the load to the rear axle becomes a negative number. If you continue forward of the front axle, the load on the rear would approach zero -- and eventually lift if off the ground. If the load is a negative 300", or 100" in front of the front axle, the load on the rear will be a negative 250.
 

fredethomas

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Gary;  The "formula" I posted is for putting loads behind the rear axle -  All different story for loading between the front and rear.  As I remember [from reading a maintenance manuel for a Chev. motorhome - C. J. Allens] that would be a direct ratio.  Put a load half way between the two axles and half the load is applied to the front and half to the rear.

What some formulas seem to neglect is the effect on the front axle when adding weight behind the rear.  Not compensating could lift the front right off the road.

 

Jim Dick

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fredethomas said:
Gary;  The "formula" I posted is for putting loads behind the rear axle -  All different story for loading between the front and rear.  As I remember [from reading a maintenance manuel for a Chev. motorhome - C. J. Allens] that would be a direct ratio.  Put a load half way between the two axles and half the load is applied to the front and half to the rear.

What some formulas seem to neglect is the effect on the front axle when adding weight behind the rear.  Not compensating could lift the front right off the road.

Fred,

If memory serves me correctly, the 32' Country Coach had 500 lbs of pig iron added to the front axle due to the effect of the diesel engine behind the rear axle. A waste of payload but necessary.

 

Bob Buchanan

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RV Roamer said:
I know that, Bob, but the formulas (or at least the examples) don't make that apparent.? And the average person does not readily understand the concept of adding a negative number.

>> I'm struggling to comprehend these formulas.
>> Are these formulas only for weight added behind the rear axle?
====
Sorry about that, Gary -- as I read your post , it didn't appear that you understood the formulas.

I guess I'm in double trouble now -- as my wrong assumption there would make you just an "Average Person"  :(. I do think that the average person would know how to add a negative number to another number. Knowing the difference between a debit and a credit is another matter :).  Actually, I was thinking in terms of just changing the sign - not keeping the plus and adding a negative.

Oh well -- was only trying to be helpful. I do apologize -- and will drop off this thread now.
 

Gary RV_Wizard

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Gary;  The "formula" I posted is for putting loads behind the rear axle -  All different story for loading between the front and rear.

That's what I deduced, since it gives incorrect results otherwise.  I was afraid a casual reader might try to follow the example for loads placed elsewhere, e.g. between the axles, and come to an erroneous conclusion.


Sorry about that, Gary -- as I read your post , it didn't appear that you understood the formulas.

No apology needed, Bob.  My "struggle" was/is that the user of the formula must know that the distances used are relative to the rear axle, with "forward"  a negative distance and rearward a positive one.  And you have a much higher opinion of the average person's algebraic skills than I do!  :D
 
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