Posted By Ron Hunter
Step gently onto the weighing scales at your local branch of Boots = Static Weight. Jump on them = Dynamic Weight.

Posted By Ali
After studying Physics and applied Maths at a level I still don't understand your terminology. "Weight" is the force of gravity exerted on a load = mg (Newtons) where g=9.81 m/s/s. Apart from slight variations in g over the earth's surface, the weight should remain constant. However, the force exerted by the load can vary with its momentum and angle of travel. Maybe you can be a little bit more specific ?
Ali

Posted By Glen Coe
The previous analogy's are pretty good.

The one I use for offshore is when a crane picks up a 10 te container its static weight is 10 te.

If it were to pick up the same container from a supply boat in a moderate sea swell it would be a snatch load and that is typically times 2.4 (this was averaged on the data from the recording safe load indicator lifts)ie 24te would be shown as a spike momentarily on the safe load indicator and yes you would see the crane boom bounce a bit.

Hope that helps, but as stated before it is all about inertia and speed.

Cheers
GC

Posted By Adrian Watson
What is being confused is static and dynamic loading.

Regards Adrian

Posted By Derek Williams
Hi All,

Many thanks for your input, you have all confirmed what I thought would be the solution, that is something placed gently or something dropped with force.

Regards,

Derek.

Posted By Robert K Lewis
I think it is easier to think of weight in motion (WIM) rather than considering dynamic weight. Using algorithms one can evaluate the weight of an unstable object standing on the load plate, eg an animal, or an object moving across the load plate at a constant speed eg a wagon. Yes if the object is capable of standing still on the load plate one can then gain a static weight.

Do not confuse this with a force exerted when a load hits the load plate which is proportional to mass x velocity. This is not a dynamic weight.

Bob

Posted By Robert K Lewis
Its good for sweets as well:-)

Bob

Posted By Steven John Bateson
Static and dynamic loads often get confused in association with crane lifting plans. The calculations are produced as if the loading was static, when a more accurate analysis would treat it as dynamic because the load is, in fact, in motion. The difference is insignificant in most cases because site controls require the crane to move slowly. Unfortunately sometimes lifting operations may become 'rushed' to the point where too much momentum is built up then decelerated too rapidly. At this point the difference between the approximate calculation (based on statics) and the reality may become sufficiently great to tip the crane over i.e. the crane is moving too fast, the operator hits the brakes for some reason, the load carries on moving and begins to decelerate in the horizontal plane whilst accelerating in the vertical plane (because it's held at a fixed radius by the lifting cable)and generates forces in accordence with Newton's 2nd law of motion

Posted By Tabs
Martin wrote: "On this subject can anybody tell me if the load should be the same weight if it is weighed statically or dynamically? "

That depends entirely on the algorithms used by the machine.

It is possible to take the information produced as the item passes over the platform and calculate the mass, and therefore the static weight (mass x force) or therefore (mass x 9.81 m/s/s).

I would suggest though that the normal use of the term "dynamic weight" is not appropriate for the situation you describe.

I would use the fish analogy ...

A 3lb carp dead on the scales will 'weigh' 3 lbs.

A 3lb carp wriggling like heck on a line will 'weigh' considerably more - and I would use a 10lb breaking strain line.

A dynamic load exerts considerably more force than a static load.

Your scales should be able to tell you when a 3lb carp passes over. Your calibration problems might be down to what else is passing over them at the same time (i.e. the belt) - it might not have a consistent thickness ...

Posted By Martin Griffith
Mitch sorry, i am aware of the meanings of static and dynamic. The words are used to describe a movement or situation in relation to a specific issue.
If my case is moving over a weigher is considered to be dynamic.
If the case however is stationary on the weigher it is considered static.

Going back to TABS fish analogy, surely the fish moving will exert a different force every time it moves therefore cannot be a constant force.
In my situation the case will have a constant momentum and weight. The belt is of uniform thickness.

My question still remains. If all forces are equal apart from the case moving over the weigher or being static on the weigher, should the resulting weight be the same for both situations?

Posted By Martin Griffith
Thanks Mitch.