Technical
The bottom blade, together with the cutting cylinder, takes considerable abuse in the municipal sector
Why Genuine Parts?
There’s nothing new about this statement. It has been a contentious issue for years, in many industries, as well as our own turf care sector. We all know the arguments for and against; price, warranty, correct fit first time or not, longer lasting or not etc. etc.
Products within the Ransomes portfolio are, more often than not, used in the harsh commercial mowing sector and are being used on roadside verges, housing areas, parks and open spaces. These sometimes hostile environments create high wear on cylinders, bottom blades, lift arms, pivot shafts and other associated components.
So, what of the issue of price over quality?
Let’s look at the bottom blade; the main component that, together with the cutting cylinder, takes considerable abuse in the municipal sector, coping not only with grass, weeds and stones but drinks cans and other sometimes hidden debris. For all that, it is a relatively inexpensive, but high volume item and hence price sensitive.
The usual discussion of genuine versus non genuine goes along the lines of; “the non genuine costs less”; reply, “does it last as long?” The response; “no, but it costs less”.
What is not taken into account at the time of purchase is that the user will almost certainly face a bottom blade change part way into the season with the non genuine blade, requiring the machine to be off road, grass not being cut and incurring additional workshop costs. There are many experienced machinery operators and drivers out there who can tell the difference between the blades used.
It is a relatively inexpensive, but high volume item and, hence, price sensitive
Of course, the cutting cylinder is the other crucial part to the cutting unit and also becomes part of this debate. What is often overlooked is that the manufacture of these two items, and the materials used, has been developed and refined over 182 years of manufacturing cylinders and blades here in Ipswich. This ensures that they function together for maximum cutting efficiency, durability and longevity.
What makes a genuine bottom blade?
Let’s look at the 30” bottom blade and its manufacture at Ipswich. Flat steel plate is loaded into an oven and brought to the relevant temperature. One at a time, the flat plates are removed, placed in a 250 tonne press and the lip is formed that will become the cutting edge of the blade.
The newly formed blade is returned to the oven in order to relieve stress, and allowed to cool naturally before being shot blasted. Excess material is then machined from the top of the blade lip.
Next, an induction heating operation, combined with the application of a special cooling process, causes a structural reaction to the metal content of the blade. This gives the blade its characteristics of cutting performance and durability.
The remaining processes are blade straightening, jig drilling (on a multi spindle drill to ensure hole positioning accuracy), grinding of the cutting edge surface, stamping with the Genuine Parts ‘R’ and then coating with oil before sending to parts inventory.
That’s only the bottom blade, so what of the cutting cylinder?
The induction heat treatment to the cutting edge of the blade ensures its durability
Cylinder manufacture
A cutting cylinder is made up of a number of parts, the spiral blades, collars (or web), spindle (or shaft) and bearing housing cups. The spiral blade material is supplied flat and straight, so it is fed through a rolling mill to create the necessary curvature required. A 10” diameter cylinder may have 4, 6 or 8 blades, so there would be differences in the finished curved shape.
The next operation is to build up a cylinder on a dummy spindle. The relevant collars are positioned on the spindle with removable spacers in between. Spiral blades are the fitted into the slots in the collars and held tightly in place by steel banding wrapped around the cylinder assembly. Skilled welders spot weld at every point where the spiral blades fit into the collars.
The welded assembly now has the steel banding removed, the dummy spindle and spacers are withdrawn, leaving a cylinder ‘cage’ assembly, which is then cut to length. The cage is heated until red hot and quenched in oil to give the hardness and wear characteristics to the spiral blades, before another heat treatment process relieves stress created during the welding phase. It is then shot blasted to clean it.
Next, the relevant spindle and bearing cups are welded in place, weld spatter removed and the cylinder assembly checked for concentricity. Powder paint is electro- statically applied to the cylinder following a chemical wash and drying process to remove all contamination. The powder melts when passing through the paint oven and, once cool, the cylinders are spun ground to provide their cutting edge.
Bottom blades are stamped with the Genuine Parts ‘R’ and then coated with oil before being sent to the parts inventory
The spiral blade material is supplied flat and straight, so the first process is feed it through a rolling mill to create the necessary curvature required for the cylinders being produced
The process for cylinder manufacture uses laser cutting for the collars, lathe turning and grinding of the bearing surfaces for the spindles and pressing of the bearing housing cups
PC AUGUST/SEPTEMBER 2014 I 137
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