Finally hit the scales
Have had various truck / trailer combinations, for 15 years, and finally weighed one. Trailer numbers from manufacturers sticker UVW 7021 lbs hitch weight 841 lbs (12%) It's a front kitchen...
Forum Discussion
RETURNING TO THE ORIGINAL POST ---
In the first post of this thread, the focus was on axle loads and we provided comments on your analysis of them.
Now the focus has turned to fender heights. Due to the very unusual sequence of height changes which were reported, I think it would be good to comment on what was measured versus what normally would be expected.
The 2008 F-250 4x4 is available with seven different front spring coefficients ranging from 349-499 lb/inch per spring. Not knowing which pertains to your TV (and not knowing if you have modified the front springs), I will use an average of 423.3 lb/inch, which gives a combined front-axle coefficient of 847 lb/inch.
The analysis of the your measured loads and heights plus the theoretical height changes is given below.
column 1: measured front axle load change
column 2: theoretical front height change assuming spring coefficient = 847 lb/inch
column 3: measured front end height change
______from "TV only" to "hitched with no WD": -440# +0.52" +1/4"
____from "hitched w/ no WD" to "WD applied": +200# -0.24" +1/4"
NET CHANGE from "TV only" to "WD applied": -240# +0.28" +1/2"
The first unexpected result is the measured height increase of 1/4" which is only about 50% of the theoretical value of 0.52".
The measured height change is in the correct direction, but corresponds to a front axle combined spring coefficient of 1760 versus a more likely value in the range of 700-1000#.
The second unexpected result is the height increase of 1/4" in response to a load increase of 200# -- the height should decrease when the load increases.
The third unexpected result (related to the second unexpected result) is the net height increase of 1/2" in response to a net load decrease of 240#. That corresponds to a front axle combined spring coefficient of 480 lb/inch.
I've analyzed a lot of load data, a lot of height data, and some combined load and height data.
My advice would be to re-do the height measurements to see if you can reproduce the reported values.
Before each measurement, you should bounce the front end up and down to see if you can get it to return to some repeatable height.
Or, if you don't want to do that, you might want to consider that the "theoretical" values above are closer to reality than the measured heights.
That would mean the actual front end rise, after application of WD is closer to 1/4" than 1/2" -- which would mean you are not at the extreme limit of the "acceptable" range.
Ron
In the first post of this thread, the focus was on axle loads and we provided comments on your analysis of them.
Now the focus has turned to fender heights. Due to the very unusual sequence of height changes which were reported, I think it would be good to comment on what was measured versus what normally would be expected.
The 2008 F-250 4x4 is available with seven different front spring coefficients ranging from 349-499 lb/inch per spring. Not knowing which pertains to your TV (and not knowing if you have modified the front springs), I will use an average of 423.3 lb/inch, which gives a combined front-axle coefficient of 847 lb/inch.
The analysis of the your measured loads and heights plus the theoretical height changes is given below.
column 1: measured front axle load change
column 2: theoretical front height change assuming spring coefficient = 847 lb/inch
column 3: measured front end height change
______from "TV only" to "hitched with no WD": -440# +0.52" +1/4"
____from "hitched w/ no WD" to "WD applied": +200# -0.24" +1/4"
NET CHANGE from "TV only" to "WD applied": -240# +0.28" +1/2"
The first unexpected result is the measured height increase of 1/4" which is only about 50% of the theoretical value of 0.52".
The measured height change is in the correct direction, but corresponds to a front axle combined spring coefficient of 1760 versus a more likely value in the range of 700-1000#.
The second unexpected result is the height increase of 1/4" in response to a load increase of 200# -- the height should decrease when the load increases.
The third unexpected result (related to the second unexpected result) is the net height increase of 1/2" in response to a net load decrease of 240#. That corresponds to a front axle combined spring coefficient of 480 lb/inch.
I've analyzed a lot of load data, a lot of height data, and some combined load and height data.
My advice would be to re-do the height measurements to see if you can reproduce the reported values.
Before each measurement, you should bounce the front end up and down to see if you can get it to return to some repeatable height.
Or, if you don't want to do that, you might want to consider that the "theoretical" values above are closer to reality than the measured heights.
That would mean the actual front end rise, after application of WD is closer to 1/4" than 1/2" -- which would mean you are not at the extreme limit of the "acceptable" range.
Ron
