Backhoe 3/Pivot Range of Motion Calculations

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Using an 8" Single Acting Cylinder

Assume we use a configuration with 2 single-acting hydraulic cylinders. To achieve a 180 degree range of pivoting with an 8 inch cylinder - the 8 inches of travel must travel through a 180 degree arc at the radius of cylinder attachment. This is impossible. The picture shows this. If the cylinder moves beyond the green line, it will not be able to return. The cylinder would have to travel past the green line to attain 180 degrees, denoted by the red semicircle arc.

Moreover, a hard stop must be enacted via the cylinders. The cylinders must either top out or bottom out. If we assume that we use 2 cylinders, one cylinder bottoming out limits the motion of the other cylinder, even if the other cylinder didn't top out. Alternately, if one cylinder tops out, that limits the retraction motion of the other cylinder.

Either single or double acting cylinders can be used. Since return to tank is required in a single acting cylinder (for closing off from dirt and collecting seepage), it is recommended here that double acting cylinders are used since these are already used in other parts of the GVCS. If a single acting cylinder were used, that would add yet another part to the GVCS total part count.

We can use an 8" cylinder that we already have in house. This means that the radius r in the picture must be calculated to determine the specific position of the cylinder.


LibreCAD Motion Analysis Source File

Here's a 2d range of motino analysis using LibreCAD: File:Backhoe Main Pivot Side to Side Geometry.dxf

The DXF file from 10/8/13 shows this cylinder mounting, shown in red - 19.6" away from the 3" pivot of backhoe. It is a 1/2" plate with a 1" DOM welded to hold the bottom end of the 8" cylinder:


This shows an overhead view of where we'd want to mount the right cylinder so that its full 8" motion corresponds to a 170 degree range of motion without the cylinder axis ever getting in line with the center of the pivot which could cause it to lock up.

Sketchup Motion Analysis Source File

By Dorkmo -




The pivot will use the 8" Cylinder for side to side rotation.

Scale Model

Video of Design Progress

Dan Benamy - File:Danbackhoe.skp

Build Preparation