Light Weight Fairway Mower FAB's

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Reel Theory
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Reels Slide Index
(Left Click Selection Box)
Four Principle Angle
Backlapping
Clearance Necessary
Total Cost of Mowing
Relief Angle
HOC
Milled Relief Blades
Bench Setting
Rake Angle
Effective Height of Cut
Bedknife Angles
Prism Gauge
Parallel Edges
FOC
Coned Shaped Reel
Bedknife Attitude
Dulling Curve
Reel/Bed Relationship
Dull Edges
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A reel cutting unit has two working parts the
bedknife and the reel blade leading edge. The
bedknife has two functions 1. It pushes against
the blade of grass and stands the grass up in a
vertical position. 2. The leading sharp edge acts
as half of a scissors. The reel blade rotates
across the bedknife performing the cutting
action, as the second half of the scissors.
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Reel Cutting Unit
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There should be NO contact between reel and
bedknife. None is needed (suggest a .002
clearance). Grass blades are .006-.007 inches
thick. Several reasons why this clearance is
necessary 1. When the reel is allowed to contact
the bedknife, the square (sharp) edges of the
reel and bedknife will rollover, becoming
dull. 2. Contact between the reel and bedknife
will generate heat. Heat generated through this
contact will distort the shape of the bedknife.
Distortion causes the bedknife to draw closer to
the reel, resulting in more rollover of the
cutting surfaces and more heat generated in the
bedknife. 3. Drag produced by an improperly
adjusted cutting unit may result in an
unacceptable clip ratio, undue strain on drive
mechanism and premature wear of the cutting unit.
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Clearance Necessary

• .002 or .001 Clearance

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Four Principle Angles
1. Relief Angle
4. Top Angle
2. Rake Angle
3. Front Angle
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The reel back relief angle is ground to remove
the cross section of the blade leaving
approximately 1 mm (.040). This 1 mm of cross
section provides some strength in the cutting
tip. When this blade cross section wears to 1/3
to the blade thickness, it is time to regrind the
reel. This angle is set at 20 degrees. Deere
recommends relief grinding the reels for these
reasons 1. Relief grinding removes metal from
the trailing edge of the blade forming an angle
(relief angle) to reduce the contact area of the
cutting edges. This reduces blade contact area
resulting in less friction. 2. Ensures longer
wear life. 3. Less time is required to
backlap. 4. Reduces squeezing and tearing of the
grass as the unit gets dull by use. 5. Provides
an area for backlapping compound to be trapped to
more effectively backlap reels. 6. Because of the
relief grind it is possible, with backlapping, to
true a reel (make it round) if a blade is .001
to .002 too high. 7. Requires less horsepower
to drive the reel.
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Reel Blade Relief Angle
20 Degree Relief Angle
.040 (1 mm)
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On smaller diameter reels with numerous blades
(i.e. greensmowers) often the reel blade has a
milled relief. This increases the open area
between the blades which1. Allows more room for
grinding2. More area for the grass to get into
the reel.3. The reduced cross section at the end
of the blades reduces the flywheel effect of
the reel making starts and stops (which are very
common on greens triplexes) easier on the
machines hydraulic system.
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Different Types of Relief
Milled Relief
Ground Relief
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Reel Load Comparison
Reel-Bedknife Clearance
.002 .005 Touch .75 .74
.88.87 .87 2.5916 17.5
2940.6 hp 0.65 hp 8.55 hp

• Relief Ground / Sharp Bedknife (HP per unit)
• No Relief / Sharp Bedknife (HP per unit)
• Increase in HP Consumed ( per unit )
• Increase in HP Consumed per 3235 (5 units)

Tests Conducted While Mowing 1.5 Bermuda to
1.0 HOC
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The reel rake angle is created by the slot in the
spider which locates the blade on an angle This
ensures that the front cutting edge is always
forward of the blade body, which in turn cuts,
not pushes, the grass. The rake angle is fixed
by the manufacturer and cannot be revised.
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Rake Angle
Rake Angle
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The bedknife has two angles the top and front
angle. The top angle, set at 5 degrees ,except
on greens mowers which have a Top angle of 6.5
degrees, is there to reduce metal contact, and it
allows cut grass to be ejected from the cutting
unit. This angle must be present for the
bedknife to work properly. The industry range
for this angle is 3-10 degrees. The front angle
is set at 5 degrees also. It assures that the
front will stand the blade of grass up
perpendicular. Without a relief angle the blade
of grass will contact the lower edge of the
bedknife and be bent over at too much of an angle
prior to being cut. In the case of mowing
greens, where very small cuts are being taken,
the reel may not capture the grass at all, and no
grass will be cut. The industry range for this
angle is 3-17 degrees.
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Bedknife Angles
Top Angle 5 Degrees (6.5 Greens Mower) Front
Angle 5 Degrees
Top Angle
Front Angle
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Reasons for grinding 1. To restore the
cylindrical shape of a reel that has become
cone-shaped due to improper adjustment of the
reel-to-bedknife clearance or worn reel
bearings. 2. To restore the edge when the grass
is not being cut across the entire length of the
bedknife, evidenced by streaks of grass left
after the mower has passed. Usually the result
of nicked blades caused by hitting foreign
objects in the grass. 3. To restore the edge when
the lack of frequent backlapping allowed the edge
to be rounded beyond the capability of the
backlapping procedure to restore the edge. 4. To
restore the edge when the reel-to-bedknife
clearance has been improperly adjusted (reel
contacting bedknife).
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Cutting Edges Must Be Parallel

• The Reel Must Be Perfectly Straight and the
  Bedknife Must be Straight and Flat in Order for
  Them to Work Properly

Reel
Bedknife
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Cone Shaped Reel

• Reels Can Become Cone- Shaped. This Causes a
  Great Deal of Strain on the Supporting Bearings
  When Adjusted Parallel to the Bedknife

Reel
Bedknife
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Backlapping is used to maintain a sharp cutting
edge between grindings. It removes a very small
amount of metal, requires less time and will
effect a smooth clean cut. It should be done on
a regular basis. Backlapping does NOT replace
grinding and should never be used to sharpen
extremely dull or out of shape reels. Backlapping
is accomplished by spinning the reel backwards
while applying special abrasive compounds to the
reel (The most metal that should be removed is
approximately .005). Usually course compounds
are used initially followed by a fine abrasive
tournament grade for final honing. Recommended
Grits 1. Greens Tees 120, 180 and 220
grit 2. Fairways, Utility 60, 80 and 100
grit Reel sharpening compounds should NOT be
toxic, oily or greasy. Although some
spingrinding machine manufacturers say
backlapping is not necessary, John Deere
recommends backlapping after spingrinding to
remove burrs and rough edges left from the
spingrinding procedure. Backlapping produces a
honed edge that will cut the grass evenly and
leave the tops of the grass with clean, straight
edges.
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Backlapping VS Grinding
Backlapping does not replace grinding, but it can
reduce how often you have to grind. Backlapping
maintains the cutting edges it is not for
establishing the cutting edges. When a reel is
being ground it is a 5 step process. This can be
a time/labor consuming process. 1) Removing
the cone shape of the reel 2) Re establish the
20 degree relief on reel blade 3) Re establish
sharp edge on reel blade (spin) 4) Top angle on
bedknife 5) Front angle on bedknife. John
Deere machines have on board backlapping. This
allows the technician to regularly backlap the
cutting units to maintain the cutting edges.
This process should not take more than 15
minutes. If edges have not been maintained, then
cutting units will need to be ground. To
maintain reels with backlapping the reel blade
MUST HAVE RELIEF.
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Dull Edges
Edges Have Become Rounded No Longer a Sharp
Edge
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When reels become dull, the leading sharp edge of
the reel and bedknife become rounded. This is
normal wear. The approximately 90 degree edges
must be restored to once again deliver a good
quality of cut.
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Backlapping
Backlapping Compound with Reel Turning in Reverse
Direction
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By regular backlapping, the sharpness of reels
stays in the optimum cutting quality range.
Note how backlapping restores cut quality.
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Cutting Unit Dulling Curve
Sharp
Optimum Cutting Quality
Usable Cutting Quality
Dull
Elapse Time in Hours
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This graph shows how the quality of cut
deteriorates over time IF NO corrective action is
taken. Note that the reel sharpness has fallen
below the optimum cutting quality. The reel
may still be cutting to some degree, but the
quality of cut is poor. When having a Grind
only program with no relief, more likely then
not, the cutting unit is in the dull area longer
before the edge is restored. This is because the
only way to maintain this edge is to grind.
Thus limiting a technicians options. Also
effecting the quality of cut.
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Backlapping Retains Optimum Cutting Quality
Sharp
Optimum Cutting Quality
Usable Cutting Quality
Dull
Elapse Time in Hours
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Note that 50 of the Total Cost of Mowing is in
Labor. 15 is maintenance and only 10 is the
purchase price. 10 of the total is for fuel,
note that although many manufacturers produce
products that have ample horsepower, that fuel
costs go up when reels get dull or when there is
no relief grind because it does take more engine
horsepower to spin the reels.
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Height of Cut (HOC)

• Two Methods of Measuring HOC
• Bench Setting
• The Height at Which the Bedknife is Set Above a
  Firm Level Surface
• Effective Cutting Height
• The Actual Height at Which Grasses Are Cut

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Bench setting is done with a gauge bar (typically
aluminum) or a straight bar with a dial indicator
in place of the screw shown above. The Bench
Setting simply measures the distance between the
top of the bedknife (cutting surface) and the
bottom of the rollers (the supposed ground
level).
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Bench Setting

• Distance Between Top of Bedknife and Bottom of
  Rollers

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The most widely accepted method of establishing
height of cut is the bench setting. This is
done statically in the shop and typically does
NOT take into account the conditions in which the
reels will be cutting.
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The effective height of cut or true height of
cut is the actual height of the grass plant
after it has been cut. This method takes into
account the many factors that affect height of
cut (HOC), such as 1. Soil conditions -Wet
or soft, resulting in the rollers sinking in to
some degree -Dry or hard, rollers do NOT sink
into the ground. 2. Grass and Environment
Conditions - Thick or Lush, rollers will ride
up on the grass raising the HOC. - Weak, limp
grass in early spring or late fall (or poor
sunshine). - Thatch causing rollers to ride
up raising the HOC. 3. Surface contact of the
rollers - Smooth rollers have more surface
area and will ride higher in the grass raising
the HOC. - Grooved rollers have less surface
(support) area and will sink lower in the grass
lowering the HOC. 4. Weight of the reel AND
ATTACHMENTS - The heavier the reel, the more
the rollers will sink into the grass effectively
lowering the HOC. A general rule is for every 10
additional pounds, the reel will sink into the
ground .005.
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Effective Height of Cut

• Weight of the Cutting Unit and Attachments
• Every 10 lbs results in .005 height difference
• Soil Conditions
• Roller Shape andSurface Area
• Grass Type

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Evaluating Cut Quality With a Prism Gauge

• Uses Right Angle Prism to Observe at Horizontal
  Plane to the Ground Line
• Measures Effective Height of Cut
• Allows to Measure Rate of Growth
• Quality of Cut Comparisons

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Frequency Of Cut (FOC)

• Distance Traveled Between Consecutive Cuts

Direction of Travel
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Frequency of Cut (clip ratio) The forward
distance traveled between successive cutting
contacts at any one shear point.
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FOC Factors

• Number of Blades on Reel
• Reel Speed (RPM)
• Travel Speed

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FOC Negative Effects

• FOC Too Slow (Higher Number)
• Marcelling (Wash Boarding)(Rippled Effect)
• FOC Too Fast (Lower Number)
• Over Stressed Grass
• Stripes and/or Brown Tips
• Accelerated Component Wear

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Marcelling

• Wash-boarding
• Rippling

ObjectionableCut Quality
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FOC Guideline

• The Lower the Height of Cut (HOC)The More Blades
  That Are Required
• The Higher the HOCThe Less Blades That Are
  Required

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Bedknife Attitude

• Down
• Level
• Better Cut Quality
• Better Stripe
• Reduces Scuffing
• Accurate Height of Cut Adjustment

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The aggressiveness of a cutting unit is
determined by the distance between the front
edge of the bedknife (cut point) and the center
line of the reel. Commonly referred to as
Attitude for the bedknife. As the reel turns
in the cutting unit the reel blades actually go
below the front edge of the bedknife (cut point).
This is how the reel gathers the grass to be cut.
If the bedknife edge was directly under the
center point of the reel the reel blades would
not gather the grass and the cutting unit would
have a poor quality of cut. The further back the
bedknife is moved from the center of the reel the
more aggressive the cut. Meaning the reel blades
are going further below the cut point. The
closer the bedknife is to the center of the reel
the less aggressive the cut. Meaning the reel
blades are not going as far below the cut point.

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Aggressive VS Less Aggressive
What determines the cut quality of a cutting
unit? The aggressiveness or non aggressiveness
of the cutting unit. The more aggressive the
cutting unit the better job the reel is doing in
gathering the grass to be cut. This provides a
good cut quality with less uncut
grass(stragglers). The down side or the fine
line, is the more aggressive the cut the more
risk you run of over stressing the grass.
Especially at lower heights of cut. This usually
shows up first on the overlap stripe. So moving
the bedknife further from the center of the reel
does have a down side. It can be moved to
far. The opposite is also true. Moving the
bedknife closer to the center of the reel the
uncut grass(stragglers) are increased because the
reel is not gathering the grass as well.
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What adjustments and maintenance practices can
change this relation ship? Facing of the
bedknife is a common practice for maintaining cut
quality. But each time a bedknife is faced
material is being removed from the front edge of
the bedknife. This moves the cut point further
from the center of the reel making it more
aggressive. Caution needs to be used when facing
a bedknife. A hand file is recommended. Roller
set up on the cutting unit can also change this
relationship. Having a cutting unit with the rear
roller set lower then the front gives the cutting
unit a pitched forward appearance thus moving the
bedknife away from the reel center. Making it
more aggressive. When the the front roller is
lower then the cutting unit is pitched backwards
moving the bedknife closer to the center of the
reel. Making the cutting unit less
aggressive. ESP cutting units it is recommended
for the roller to be parallel to the bedknife and
the notches on the roller to be no more then 1
notch off front to back.
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Continued. What adjustments and maintenance
practices can change this relation ship?
The NON-ESP cutting units use roller bracket
location in the frame to determine the HOC range
of the cutting unit. It is possible with these
cutting units to obtain the same HOC in different
height ranges. The difference is, in this case,
is the location of the front and rear roller
heights. One range will make the cut more
aggressive When stressing of the grass is seen
there are points that need to be checked. 1) Make
sure reel and bedknife are sharp. 2) Bedknife
relationship to reel. Roller settingsare we too
aggressive 3) Replace bedknife to reestablish the
proper bedknife to center of the reel
relationship.
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Reel / Bedknife Relationship

• ESP Cutting Unit(Parallel Bedknife)

.78 MM
11.76 MM
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On ESP cutting units, with the bedknife
adjusted parallel with the ground, the reel
actually reaches .78 mm below the top surface
of the bedknife. The front edge of the bedknife
is nearly 12 mm behind the center line of the
reel.
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On ESP cutting units, with the bedknife
adjusted with the front edge slightly down, the
reel actually reaches 1.02 mm below the top
surface of the bedknife. The front edge of the
bedknife is 13.43 mm behind the center line of
the reel.
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Reel / Bedknife Relationship

• ESP Cutting Unit(Bedknife Angled Down 6MM)

1.02 MM
13.43 MM
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Grease Recommendations
It is essential that you use the proper grease
when performing the scheduled maintenance. Below
is John Deere recommendations for grease used on
Golf and Turf products. For CUTTING UNITS Use
John Deere CORNHEAD grease (AH80490/AN102562) per
Operators Manual. Other greases may be used if
above John Deere greases are not available,
provided they meet the following compatibility
specifications only Polyurea Grease - NLGI
Grade 0 Calcium Complex Grease - NLGI Grade
0. For TRACTION UNITS Use John Deere Moly High
Temperature EP 2 grease (TY6333) on pivots,
bushing and lift arms where there is low speed,
high load applications. IMPORTANT DO NOT mix
any other greases (including calcium, lithium,
and lithium 12-hydroxy based greases) with above
recommended greases, they are NOT COMPATIBLE. For
best results, completely remove all
non-compatible grease from housing and fill with
above preferred grease or one of the other
greases, which are compatible with each other. DO
NOT use any BIO-GREASE. Additional
Information Due to the demands of the
manufacturing process, a very high
water/corrosion resistant calcium based 2 grease
is used at the factory. The products listed above
ARE COMPATIBLE with the factory installed grease.
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All Greases Are NOT Created Equal
Bushing and Shaft

• Different Applications Require Greases with
  Characteristics that Meet Their Requirements