Overturning Moment

[JSTRUT]

I need to check overturning for a knuckleboom loader mounted on a 16 ft. tall steel substructure. The boom of the loader is 36' long and will lift a 1000lb load. The steel substructure is weighs 7500lbs and is welded to inbeds in a concrete foundation. The foundation measure 12'x12'x4'. How do I go about finding the overturning moment?

 

[msquared48]

Draw a diagram, or several diagrams, of the loading conditions and calculate it using statics...?

Mike McCann
MMC Engineering

 

[JStephen]

Also check if the manufacturer publishes required load information. It looks like you could get some horizontal forces exerted as well as the lift.

 

[ztengguy]

What msquared48 said. VERY simple statics problem.

 

[theonlynamenottaken]

It is very simple to determine the overturning load based on the rated load of the hoist, and the weight of the unit if you know the C.G. HOWEVER, I contend that you shouldn't use that as your overturning moment... atleast not as an ultimate moment. Anytime you have a determinate system like this cantilever you should ensure that it is fail-safe, and that something like a hydraulic cylinder or an electric hoist motor stalls out before your supporting structure gives way. As JStephen suggested, look to the manufacturer for information. Without manufacturer's data be prudent in using a safety factor to ensure fail-safety.

 

[jmen68]

Overturning moment depends on track arrangement. For instance if the tracks are perpendicular to the cab, overturning moment is about the center line of the (load side) track. As everyone unclearly stated, you set up a diagram with where ever your tipping point being your datum line and sum your moments about that point. Probably stating the obvious here but if you don't know, you have to make sure your "ass-end" has more moment, otherwise you will overturn.
hope this helped.