axle weight calculation

[Mvander]

I have recently weight my tt tounge and got 650lbs using the bathroom scale method.

I think i recall seeing an equation using the ball distance from the axle and wheelbase to determine the weight applied to the axle without using wd.

If anyone knows the equation and would post it that would be much appreciated

Thanks

[Mvander]

Ron Gratz wrote:
Sorry for the confusion -- I had an incorrect entry in my first post.

I typed "distance from ball to rear axle" which should have been "distance from ball to front axle".
I've edited the first post to change "rear" to "front".

Using your numbers, the corrected formula would give:

Load added to rear axle = 650*(157+58)/157 = 890#.

My incorrect formula gave the amount of load removed from the front axle -- 240#.
The load added to the rear axle then is 650+240 = 890#.
Ron

Thanks for clearing that up. It makes much more sense now.

[RCMAN46]

Mvander wrote:

Mvander wrote:

RCMAN46 wrote:

Mvander wrote:
650÷58×157=1759

This seems more correct. I think i confused myself.

That will give you about a 27% tongue weight?

The tounge wt is known. I was trying to figure what weight would be applied to the axle due to the lever effect independant of weight distribution.

Im afraid i didnt explain properly. The trailer is 5200# and the tonge is 650. I was tryig to figure the wt applied to the trucks rear axle when the trailer was on the ball without the wd hitch.

Ok makes sense now.
Mostly my mistake for not reading more carefully.

Now we get a little over 12% for tongue weight percentage.

[Mvander]

Mvander wrote:

RCMAN46 wrote:

Mvander wrote:
650÷58×157=1759

This seems more correct. I think i confused myself.

That will give you about a 27% tongue weight?

The tounge wt is known. I was trying to figure what weight would be applied to the axle due to the lever effect independant of weight distribution.

Im afraid i didnt explain properly. The trailer is 5200# and the tonge is 650. I was tryig to figure the wt applied to the trucks rear axle when the trailer was on the ball without the wd hitch.

[Mvander]

RCMAN46 wrote:

Mvander wrote:
650÷58×157=1759

This seems more correct. I think i confused myself.

That will give you about a 27% tongue weight?

The tounge wt is known. I was trying to figure what weight would be applied to the axle due to the lever effect independant of weight distribution.

[RCMAN46]

Do not think we can get trailer weight this way.

Assume I have a single axle trailer that weighs 2000 lbs.

I can distribute that weight to give any tongue weight I want.

I can load it so I only have 20 lbs or even a negative tongue weight if I put most of the weight behind the axle.

[Ron_Gratz]

Sorry for the confusion -- I had an incorrect entry in my first post.

I typed "distance from ball to rear axle" which should have been "distance from ball to front axle".
I've edited the first post to change "rear" to "front".

Using your numbers, the corrected formula would give:

Load added to rear axle = 650*(157+58)/157 = 890#.

My incorrect formula gave the amount of load removed from the front axle -- 240#.
The load added to the rear axle then is 650+240 = 890#.

Ron

[RCMAN46]

Mvander wrote:
650÷58×157=1759

This seems more correct. I think i confused myself.

That will give you about a 27% tongue weight?

[Mvander]

650÷58×157=1759

This seems more correct. I think i confused myself.

[Mvander]

Thanks Ron. Somehow I thought you would know this.

Im just trying to guesstimate the amount of sag with a fifth wheel and short of shoveling a lot of "known weight" into the truck this will give me a base line.

Tounge 650# x 58" axle to ball = 37700 ÷ 157" wb = 240.13 ???

I think i have this wrong.

[Ron_Gratz]

bguy wrote:
Units of measure? lb for weight? inches for axle to ball? and inches for wheelbase?

The units for load added to rear axle will be the same as the units one chooses to use for the tongue weight.
If tongue weight is in pounds -- load added will be in pounds.
If tongue weight is in kilograms -- load added will be in kilograms.

It doesn't make any difference which units you use for the distances -- as long as they are the same.
When you divide one distance by the other -- you end up with a ratio which has no units.
Since wheelbase usually is specified in inches, it would be convenient to use inches for both distances.

Ron

[bguy]

Ron Gratz wrote:
With no WD applied --
load added to rear axle equals tongue weight times distance from ball to rear axle divided by wheelbase.

Ron

Units of measure? lb for weight? inches for axle to ball? and inches for wheelbase?

[Ron3rd]

I knew somebody smarter than me would come along :S

[Ron_Gratz]

With no WD applied --
load added to rear axle equals tongue weight times distance from ball to front axle divided by wheelbase.

Ron

[Ron3rd]

I don't know the equation, but I would assume you would first need to know the overall weight of the trailer from a scale to plug into the equation.