Toro 09167SL User Manual

Rotary Mower

Basics

PART NO. 09167SL

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Rotary Mowers 1

Table of Contents

Historical Background......................................................................................................2

Theory of Operation.........................................................................................................4

Cutting Action..................................................................................................................6

Equipment Application.....................................................................................................8

Importance of the Operator ...........................................................................................10

Productive Equipment Operation...................................................................................11

Cutting Unit Adjustments...............................................................................................15

Inspection Maintenance and Repairs ............................................................................16

Rotary Blade Inspection and Sharpening ......................................................................20

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2 Rotary Mowers

Historical Background

The first practical concept of a rotary type mower
goes back to the 1930's. The concept evolved from
the need for a grass maintenance tool that could cut
long grass acceptably without the cost and
sophistication of a reel mower.

During the 1940's improvements in engines and
material brought about increased use of rotaries but
it wasn't until after World War II that their use
became a common sight.

During the 1960's the bagging concept evolved and
rotary designs incorporated multi- blade
configurations useful for cutting large commercial
type areas.

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Rotary Mowers 3

Improvements in engines and drive systems have
resulted in the very effective commercial type rotary
mowers that are presently available.

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4 Rotary Mowers

Theory of Operation

Blade mounting
and drive system

Blade

Deck h ous in g

There are three basic structural members to a rotary cutting unit.
Cutter Deck Housing

The deck housing supports the blade hubs with their drive mechanism and is shaped to carry the cut grass
clippings away from the deck in an effective manner.

Blade mounting and drive system
The blade is normally driven directly by the engine crankshaft, a hydraulic motor or through a belt pulley
system to each blade hub.

The blade
The blade has a sharpened cutting edge at each end with a curved up sail area to create an air flow. This air
flow will whip the grass blades exposing them to the blade cutting edge. The air flow also assists in carrying
the cut grass blades out the discharge.

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Rotary Mowers 5

Power transfer from the engine to the blades is
typically done by way of belts and transfer shafts.
Belt drives typically transfer a high percentage of
the available horsepower to the blade and generally
produce much less noise than hydraulic drive
systems.

Blade spindle assembly

Large Di a met er
Ductile Cast Iron
Spindle Support

Ductile cast iron,
stronger than
aluminum or
regular cast iron

®

Timken
Roller Bearings

Support spindle
shaft better than
ball bearings

50% mor e load
carryi ng capacity
than b all b eari ngs

Tapered

Solid Cold Finished
Steel Spindle Shaft

Large diameter shaft is
resist ant t o tors i on and
bending failure

Blade Retainer &
Anti-Scalp Cup

Eliminates blade
slippage an d protects
turf from damage

The deck spindles usually run at approximately 2000 to 2500 RPM. They feature tapered roller bearing for
impact resistance and durability. The bearings can be greased, and if done properly can ensure long life
while also purging contaminates from the assembly.

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6 Rotary Mowers

Cutting Action

A rotary mower cuts grass by impacting the blade
cutting edge against the grass blades at a very high
velocity. This cutting action requires that the blade
cutting edge is sharp and rotating at an adequate
speed.

Cutting action

Cutting Blade Design

Three types of cutting decks are shown here; a
recycler deck, side discharge and contour deck.

From left to right. Low sail, high sail, medium sail,
recycler sail, and atomic mulching blade. Higher
sails, generate higher lift within the cutting chamber.
The type of blade utilized, depends on cutting deck
design and turf conditions.

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Rotary Mowers 7

To understand rotary cutting theory you must

Rotary mower clip

Requirements for

acceptable performance

understand the concept of clip.
Clip can be defined as the forward distance traveled

by the cutting unit during one revolution of the blade.
This distance is divided by the number of blade tips
to arrive at the clip dimension. The dotted lines
represent the cut path by the previous blade tip.

Although the blade cutting edge may be 3" - 4" long
the very tip is the primary contact point with the grass
blades on each pass.

The remaining portion of the cutting edge will tend to
cut off the stragglers from the previous blade pass.
The blade tips are normally lower than the rest of the
blade to avoid any drag on the turf absorbing rotating
horsepower and damaging the grass.

Factors which affect clip:

• Blade speed

• Ground speed

Three basic requirements for acceptable
performance:

The blade must be straight with sharp cutting edges.
The blade must have the proper attitude in relation to
the ground surface.
The blade must rotate at the proper speed with an
accommodating ground speed to get an acceptable
clip.

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