Soil Mixer - Rotor Module - Build Instructions

March 12 2013

The latest version of the soil mixer/pulverizer unit is past the high level design stage. The instructions below are the *plan* for how to build the unit, not documentation of a fabrication procedure. The actual fabrication procedure will also be documented, and deviations from the plan illuminating.

Overview: The tine modules are pieces of pipe cut into sections 3 inches long, the tines made from 1/4 inch steel plate welded on to said pipe sections.

They have a hole cut with a torch in the wall of the pipe, and a nut welded on such that the end of the bolt passing through the hole and nut tightens against the main steel shaft, which passes through the pipe. Detailed measurements are found in the design files. This is not a positive lock mechanism, and hopefully this will allow slipping of the tine module relative to the shaft and other tines, in the event the tines become jammed, e.g. against a large rock.

The coupler to the 6 spline motor shaft consists of a standard 6 spline coupler attached to the main shaft by drilling a hole path along the diameter of the shaft, and there is already a hole provided through the collar of a standard coupler. A bolt rather than a pin passes through the holes, preventing relative rotation.

Fabrication of the Tine modules:

Cut pieces of pipe into 3 inch sections with a cold cut saw. Cut the holes for the bolt to pass through using a plasma or oxy-acetylene torch.

The tines can be manufactured with the metalworking machine and/or a torch easily, or with a CNC torch table.

With a metalworking machine and hand torch:

Use 2" wide, 1/4 thick steel strips, cut into sections 5" long with the metal worker, then cut a roughly 1.5 inch slit cut in the end of the tine with the torch, to allow the splitting of the ends seen in the photos.  The tips can then be bent by hand with a monkey wrench.  The use of the iron worker to both split and bend the ends of the tines may be an option.

The rotor turns at 600 rpm, but the shaft and bearings are sturdy enough that vibration caused by poor symmetry of the tine modules is not a problem. The tines are currently attached individually by welding them to the pipe sections (the collar).

If we have access to a cnc torch table, cutting a cross, like a plus sign, from 1/4 steel sheet, which includes all 4 tines and slits, and a hole in the center for the pipe section to pass through, may be used. The crosses can be tessellated, or packed together, to waste less metal when cutting them out of the sheet of 1/4 in steel, as well as cutting time, as some of the cut lines overlap.

Shaft fabrication:

Modify the circular main shaft by grinding down one side flat, about 1/4 inches, to provide positive locking of the bolt against the otherwise circular shaft.

Drill the hole in the shaft for the coupler pin.

Final assembly with the bucket:

The main shaft then goes through the bearing on the side of the bucket which does not have the motor mount, and through all 14 tine modules. With the end with the hole for the motor coupler bolt/shear pin on the right end, don't forget :). Unlike in prior versions of the pulverizer, do not weld the tine modules to one another.

Secure the shaft to the bearings by tightening the bolts integral to the bearings. Now secure all the tine modules to the shaft by tightening the bolts.

Attach the motor coupler and motor, with the hydraulic connections pointed towards the tractor. Go back over and ensure that all bolts are suitably tight, and you are done.

images: Neither the dozuki nor the wiki's file upload features are functional right now, so the images will have to come along later.