Car ramps - under construction

[Frank S]

Here is a method that I used to use for determining the maximum distance apart for the ladder rungs
I took the weight of the smallest vehicle that would be driven up the ramps divided by 4 then divided by the tire width then divided by the proper tire pressure then again the weight by 4 then by the rolling radius ( distance from the ground to the center of the axle) then by the width of the tire then added the 2 results and divided by 2 the answer is the distance
For instance if say a vehicle weighs 3600 lbs and has 6" wide tires 32 PSI and a 14" rolling radius it would go like this
3600/4=900/6= 150/32=4.6875 3600/4=900/6=150/14=10.714+4.6875= 15.401/2=7.7"
This would mean that 7.7" would the the distance between the rungs
Other factors come into play as well such as the inclination of slope extra wide tires will change the distance by making it less tires less than 6 inches would make the distance longer this causes a problem in smaller diameter tires so I used 6" as a moderate constant dimension
Placing the rungs at half the max distance makes for a much easier climb for the non powered end of the vehicle.
I hope this helps