Technical
Cutting unit checked to ensure it is cylindrical Bottom blade sharpening
any imbalance, the reel is washed, dried and stacked in bins ready to go to the next part of the production process, or boxed to go into the spares inventory in our Customer Care department.
Bottom Blade production
There is another component that is essential in the construction of a cutting cylinder and that is the bottom blade (sometimes referred to as a bedknife). The bottom blade is the stationary blade, attached to a rigid backing plate, which works together with the rotating cutting blades to provide the shearing action necessary to cut grass.
As you would expect by now, we fashion our own bottom blades here on site.
They arrive here as flat bars in various thicknesses, cut to lengths relevant to the type of cutting cylinder they will be used with.
The bottom blade is heated in a furnace and, once pliable, is then put into a press to form the lip, the leading edge that will work with the cylinder blade to cut grass. A second section on the press flattens the blade to remove any distortions from the heating process. Once cooled, the lip is then ground to give a sharp edge.
The blade is then shot-blasted to ensure a smooth interface with the backing plate and the lip is induction hardened. Following a further heat treatment, the holes for the backing plate fixing screws are drilled, countersunk and the lip is ground again to give it its final edge.
If it is being used on a production mower, it will go to the Machine Shop to be fixed to its backing plate or coated with a preservative, packaged and sent to
our Customer Care department for later sale as a spare part.
Cutting unit assembly
If the cutting cylinder is to be used on a production mower, then it has to be assembled into a cutting unit frame. This frame will eventually carry the cutting cylinder, the rigid backing plate and rollers.
The ‘box construction’ of the frame means that that the cutting cylinder, frame cross members, bottom blade and rollers are straight and parallel to each other and the vertical components - spiders, frame side plates - are parallel to each other and perpendicular to the horizontal components. Slightly complicated, but it means that the unit is true in both planes.
The frame assembly comprises the two side plates and relevant cross members, which are robot welded to form a rigid structure. The first process is to attach the bottom block and bottom blade assembly, insert the rear roller, fit bottom blade adjuster mechanism, insert the cutting cylinder into the frame and attach the bearings to the shaft ends.
Next, we attach the housing for the hydraulic motor and backlap to put an edge on the bottom blade. If required, we fit the front roller at this stage. The entire unit is then set for parallel, grease is pumped into the bearings before being placed into a wash unit to remove the backlap paste.
Decals are applied to the outer casing, and the concaves, which help disperse the grass clippings, are bolted to the unit and the job is finished. The completed
Bottom blade being stamped to show it’s a genuine Ransomes part
unit is then moved to the end station on one of the dedicated production lines for fitting to the relevant mower.
So, that’s an overview of the processes that go into preparing the majority of components used to produce a modern day mower. A significant section of this article has been devoted to cutting, bending, shaping, welding and machining components. These are standard operations that you would expect in any manufacturing facility across the UK.
What, I believe, sets Ransomes Jacobsen apart is the ability to produce precision cutting units that provide you with tools to do your job as turf professionals. We’re extremely proud of our ‘Made in Britain’ heritage, and long may it continue.
In the previous feature we looked at the concept and design process, in this article we looked at the production of the various components and, in the next feature, we will focus on the physical building of a mower as it progresses along one of our production lines.
Cylinder unit fabrication
Front roller attachment to municipal cutting unit
Lee Kristensen and Richard Comely APRIL/MAY 2013 PC 129
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