[VAC] Re: new participant and axles

[Warren Little <wlittle@xxxxxxxxx>]

I was asked how I made the measurements on my axles.

I duck taped a yard stick, vertically oriented, on the side of my
trailer so that it extended down past the wheel hubs. 

I took a straight piece of wire about 6" long and pushed it into a hole
I drilled in the center of a 2" piece of 1" X 2" wood. I then duck taped
this assembly to the center of a wheel hub so the wire stuck straight
out and was in close proximity to the scale on the yardstick.

With the wheel jacked off the ground the wire pointed to 28 3/8".
With the wheel supporting a normal load the wire pointed to 27 5/16".
With the wheel sitting on a 6" board and supporting all the weight on
one side the wire pointed to 26 1/2".

I eyeballed the torsion arm to be horizontal with the wheel off the
ground.
I also eyeballed the torsion arm to be 12" long.

Under normal load the wheel went up 28 3/8 - 27 5/16 =1 1/16".
Under double load the wheel went up 28 3/8 - 26 1/2 = 1 7/8"

The normal load angle is therefore invsin of 1 1/16/12 = +5 deg.

The double load angle is therefore invsin of 1 7/8/12 = +9.25 deg.

I was surprised at how stiff the axles were. Doubling the weight only
caused them to go up 4.25 deg or 13/16" over their position at normal
weight.

I believe my trailer weighs about 7000 lbs so 1750 lbs. caused my wheel
to go up 4.25 deg. Hence the spring constant is 1750/4.25 = 411 lbs/deg.

I would be very interested in similar measurements and calculations
using a new axle.

Warren Little #9302
76 Sovereign