[daless2]

Originally Posted by SuperHatch

I misused the word "All", but there is still a great deal of load on the tailgate that would otherwise not be there.



You have the force of the weight of the ATV. For arguments sake, we'll say the ATV weighs 800lbs with you on it (600lb ATV, 200lb rider) and the CG is such that the weight is evenly split on the F/R axles (400lb each). The force B is 400lb, loaded approximately 2/3 the way up the ramp. We can also assume the ramp angle C is 30 degrees. The rear axle load B then is distributed between the resultant force D ("mother earth") and force E (the tailgate or that product). We can break force B into it's components, and when doing so we find out that the force perpendicular to the ramp is ~350lb. [ 400*cos(30) ]. Since that force is 2/3 the way up the ramp, we need to force balance the loaded member. There is a component of force D and E supporting this weight. According to Newton, the sum of the moments on any loaded member equals zero around any given point. If we analyze the moments around the point where the ramp touches the ground we have a moment of 400lb x 2L/3 and another equal and opposite moment of xlb x 3L/3. 267L = xL, the L's cancel, and we have a force of 267lb on the gate perpendicular to the ramp. The component of this force acting downwards is 308lb ( 267/cos(30) ).

Considering the rear axle load assumption of 400lb on the ATV, I would say that 308lb on the gate is a very good deal of additional stress that could cause cracking.

I made a lot of assumtions in this calculation, but the gist is there...

Hi SuperHatch,

Thanks for your post. I can get into this stuff!!!!

You’re right, the jest of it is there in your explanation, yet the weight sitting on the edge of the tailgate will change, as the ATV is rolled up the ramp because the angle, relative to the wheelbase will vary logarithmically with distance of the ATV into the bed.

One might also want to be concerned with the length of the wheelbase of the ATV and the length of the ramps as well. As both are major factors in these calculations.

A few years back I wrote an article to help folks understand the physics of this.

The effort was to help folks determine exactly where the Center of Gravity and Roll Over Angles for their Off Road Vehicles is located.

If you have an interest in reading it here’s the link.

http://www.jeepaholics.com/tech/cog/

There is a downloadable spreadsheet to go with the article. Don’t miss it if you want to do this.

If anyone cares to determine the Center of Gravity, and what the Roll Over Angles would be for your Tundra, you can use this write-up, take a few measurements and plug them into the spreadsheet. All the math is automagically done for you.

It also may help you understand the loads put on your tailgates using ramps, and why one ATV of a given weight might cause a problem (The shorter the wheelbase, the higher the percentage of weight on the tailgate), and another ATV of the same weight does not cause a tailgate issue (Longer wheelbase puts less weight, on the tailgate edge at any moment in time.)


Maybe someone will find it helpful.

Frank