Calculating ramp angles?

Per another topic where we were discussing box trucks, I saw some examples of people using them to haul race cars. These were your standard 48" high loading dock height type trucks also.

The ramps they were using are 14ft Melcher style ramps, each one is 3 ft wide and they come in many lengths up to about 16ft, they are rated at 5k per ramp or 6k per ramp if you get aluminum ones and run about 1300 bucks. These are designed for the moving industry that is shipping cars inside tractor trailers. how would you go about figuring out the approach angle and breakover angles to know if a race car would fit (or would fit it you also used race ramps at the end of those 14' ramps

For approach angle:  Park vehicle on level ground, put one end of yardstick against  front of front tire, raise other end of yardstick to touch front "bumper" of car, measure angle between yardstick and ground.

If you know the height of the truck and the length of the ramp you can use some geometry to measure the angle and compare it to approach angle.  The ramp angle needs to be less than the approach angle.

For a 14 ft ramp and 48 in load height it's a ramp angle of 18°

Don't forget about deparure angle too. Same process as approach angle to figure out. 

I suspect that breakover angle is the more important one here. I guess that's figured out by creating a right triangle, with one leg equal to the lowest point in the center of the car, and the other leg equal to half the wheelbase. Double the included angle on the lowest point leg should be your breakover, right?

I haven't used it, but this may be the easy button for breakover angle:

Calculator

I found some geometric calculators but the issue was they didnt let me calculate any of the "sides" or angles IE I know the ramp length and the deck height. It would let me put in "deck height" and "floor length" but not the ramp length

Ok if I am doing this right, its 24inches from wheel to bumper, the bumper is 5.5" high, measuring from the wheel to the bumper diagonally is about 25.5 which works out to 12degrees here

http://www.mathwarehouse.com/triangle-calculator/online.php

this is a 4.5" pinch weld ride height miata without an R lip

I calculate departure angle as being around 16 degrees

Race ramps has lots of smaller options so I guess the question is how much does "reducing" the load deck height by 6-7" impact that 18 degrees

I think, for a race car, you are pretty much limited to making the nose of the car removable.  To get into a box van with anything too low, you will need ramps a hundred feet long.

Make sure you buy something with air suspension.  Leave the front up, dump the air to the rear, and gain six inches or so.

Whatever your calcs work out to add 2-4 ft rarely is the ground level and flat and don't forget your buddys car may not be the same as yours.. Use the longest that will store.

I made this bus hauler at 18 or 19.  I do miss those days.

ramps are 2x12x20 with 2x2 angle iron bolted to the wood and welded stock across the two i used jack stands at mid point setting the stand 1-2 inchs below the wood so the ramp flexed to the stand that way the ramps staied put.  

In reply to Jaynen :

going to the 16 foot ramps makes the angle 15 degrees you would need the ramp to be 19 or 20 ft to get it under 12 degrees.

dropping the deck height to 36" makes the angle for the 14 ft ramps about 12.6 degrees

As 44 dwarf said, make note of the angle of the ground.  If its sloped in the direction of the ramps, it'll make your approach easier, but your breakover worse.  If it is sloped perpendicular to the ramps, it will do the opposite.  In both cases, longer ramps will help.

Also, if you question your trig, this is a great use for a basic free cad program.

I think what is fairly obvious to me at this point is a lot of other people have thought about this, and if this was a great solution it would be WAY more common lol, even the landscaping trucks with dovetails the dove tail looks like it might be too harsh a breakover

I have and still do this when loading my F350 with motorcycles, Put the front end on oil change ramps this lifts the front so it drops the tailgate angle.