John,
I am not a math/trailer/geometry geek, but you really have two problems
that you need to solve. The first one is: Does the nose/tail of the vehicle
drag going up the ramp? The second one is: Does the area between the wheels
drag when the vehicle is on both the ramp and the trailer bed.
You add to the difficulty factor if the ramps are shorter than the wheelbase
of the vehicle. Based on your drawing if distance B is greater than distance
D then you can consider the two problems independent.
To get on the ramp you need to make sure that you approach/departure angles
are
greater than the angle made with the ramp on the ground...
Angle of ramp = arc tan(A/B)
Approach angle = arc tan(E/C) except that most cars you have "stuff" that
hangs down so you need to figure out an effective E. This can be measured
using something straight placed under the axle and calculating the angle that
way.
To get on the ramp you will need both the approach and departure (same thing
measured on the back of the vehicle) to be greater than the angle of the
ramp.
To get from the ramp to the trailer you are concerned about something called
break over angle. To calculate this you need to know the angle between the
ramp
and the deck of the trailer (this will be different than the angle of the ramp
to the ground if the deck of the trailer is not parallel with the ground. But
for simplicity sake I will assume (big mistake) that you have a level trailer
level ground... If that is the case then I can draw a triangle with a base
that is the length of the wheelbase (D) and the angle opposite of the base is
the supplement of the ramp angle (180-Ra). The height of the triangle is then
given by:
D
----------------
2 tan((180-Ra)/2)
If this number is less than the minimum height of the vehicle between the
wheels then you can roll from the ramp to the bed of the trailers.
If the ramp is shorter than the wheelbase it makes it easier in terms of
departure angle. The break over calculation is more difficult but I think
that if the ramp is longer than 1/2 the wheelbase using the above check will
be a bit conservative, but for ramps less than 1/2 the wheelbase you will
need to redo the math for the case with the rear wheel at the bottom of the
ramp.
Disclaimer: I have not had enough coffee yet today to be sure that the
above is 100% correct.
Stuart.
-----Original Message-----
From: shop-talk-bounces@autox.team.net
[mailto:shop-talk-bounces@autox.team.net] On Behalf Of john niolon
Sent: Wednesday, November 30, 2011 6:29 AM
To: shop-talk
Subject: [Shop-talk] MATH GURUS AND TRAILER BUILDERS
math and geometry have never been my strong suite... I need some help with a
formula
Here's the math problem for all you geometry/trig/calculus/trailer building
car people.(that have to haul the ride sitting in the shop... shop content)
I need to calculate the ramp length for a car hauler trailer so the vehicle
won't drag on loading. given
a. the height of the trailer bed
c. the distance from the front edge of the vehicle to the front tire contact
point
d. the wheel base of the vehicle
e. the height of the vehicle at it's lowest point
I think I've included all the variables... I know dovetailing the trailer
helps a lot... but we might have to work with what's available...
a "plug in" formula would be sweet so you could just put in the variables and
it would calculate the ramp length
I've got a sketch of what I'm trying to solve if you want to look at
http://jniolon.classicpickup.com/RAMP.HTML
I know this group can come up with something... heck, if I had the material
you could build it be quitting time
thanks
John
_______________________________________________
Shop-talk@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation $12.96
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe/Manage:
http://autox.team.net/mailman/options/shop-talk/stuart.a.galt@boeing.com
_______________________________________________
Shop-talk@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation $12.96
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
|