Extractor load calculation

[JeanMicheling]

Hello Folks,

My question is about a silo extractor. I'm designing the bearing and I was interested on the loads on the extrator worm screw that ''extract'' the silo's stuff. When the extractor is static the worm screw carry the silo's stuff weigth but when the worm srew is running, there is an axial load caused by the stuff restriction but what about the radial load caused by the weigth of the silo's stuff since the worm screw take off the silo stuff constantly. Can we still consider the weight of the stuff in the silo in a dynamic operation.

Thanks for your help,

 

[berkshire]

JeanMicheling (Mechanical)
I need more information, is this a solid screw or a ribbon screw.
B.E.

 

[JeanMicheling]

I'm not sure to completly understand what you mean by ribbon gear but anyway I think you will be able to tell which one it is with this drawing

http://server2.uploadit.org/files/Jeanmicheling-wormgear.jpg

 

[zekeman]

The two main forces on the bearings are the lateral static force due to the weight of the material bbetween the bearings and the thrust force which comes from the momentum equation, namely
F=mass rate of flow *velocity. For example, if the annular area is A,and the density is d lb/ft^3 and the axial flow velocity is V, then
F=d*A*V^2/g

 

[berkshire]

JeanMicheling (Mechanical)
What you are using is a stepped solid screw.
The ribbon screw is a round bar coiled in a helical spiral around the main shaft and attached to the shaft at points with brackets.
It tends to have a lower radial load because the material is free to flow around the shaft because of the lower annular area. Zekeman has already given you the formula you need.
B.E.