HOW TO CALCULATE WEIGHT DISTRIBUTION? 2

[kevwoogs]

Hi all.

I am in the early stages of designing a specialist chassis/trailer and am concerned with the weight distribution. Inside the trailer body there is a lot of hardware to package and movable equipment. I need a way quick and dirty way to calculate the reaction forces at each wheel (single axle) and at the nose/hitch. In excel maybe??? Any help will do!!!

Thanks – Kevin

 

[GregLocock]

Locate the centre of gravity of each part, and its mass.

Then the position of the overall CG in x is sum (x*mass for each part)/total mass

same for y and z

the hitch and wheel loads are then found by moments about a suitable axis.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

I just observe the compression in the springs of the trailer and the tow car.

Basically if something is heavy or should I say has high weight for its volume, I put it over the trailer axle or just a little in front of it on the floor, and if it is light or fluffy, I put it at either end or up high.

You could just build a prototype platform the size of the trailer and place scales under it at the wheel and towing hitch points and just place the components on it and read the weights, or even build a prototype "empty" trailer and do the same if you need more accuracy. That also gives you a real world feel for loading, unloading and using the trailer.

Also things that change weight like a water tank that might be full, empty or something in between should be over the axle so their load variation does not impact on balance.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[kevwoogs]

Thanks Guys,

I have now created a spredsheet with all component COG`s relative to x,y and z and equated the overall COG.

In the zx plane (side view) I am able to determin the hitch weight by a simple lever moment with a pivotpoint (cl of wheel), cog position, and a hitch position. This assumes that all 3 points are level, which isnt the case - My COG is higher by about 1000mm!

I have created a vector diagram in xy plane but cant for the life of me figure out what to do :-(

Can anybody give me the equation???

In zx plane My co-ordiates are:-

Pivot (wheel c/l) - X0,Z0
COG (of trailer/body) - X+100(towards hitch), Z+1000 (up)
Hitch - X+3570, Z0


Thanks - Kevin

 

[HDS]

http://www.sae.org/technical/books/R-114

 

[GregLocock]

cg height won't affect hitch weight significantly, at rest

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.