Drawworks: The Rest of the Story
By John L’Espoir
Drawworks: The Rest of the Story
What are catheads and catworks? How do we choose from bevel gears, spiral bevel gears,
or hypoid gears? Are chains dry, brush-lubed, or oil bath?
drawworks receives horsepower from a mechanical
drive or a hydraulic or hydrostatic drive. We will talk
about these more in a future article.
Generally speaking, most rigs in the
water well industry will incorporate a
bevel gear box also known as a right
angle gear drive. Plain bevel gears, like
spur gears, will be very noisy and are
the least desired. Spiral bevel gears, like
helix gears, run a lot more smoothly and
quietly, and engage more than one tooth
at a time. Bearings must be kept tight
in these boxes to avoid chipping of the
hardened gear teeth.
The GEFCO drawworks for the models 2500 and 3000 uses a hypoid gear
set. A hypoid gear set has offset centerlines to allow the passage of two shafts
whereas spiral bevel sets intersect the
centerlines. Having a through drive allows the engineer to design a disconnect
feature to keep power to the rotary and
stop power to the drawworks. The jaw
clutch is air-operated and may only be
engaged with the transmission clutch
disengaged. A very simple interlock can
be installed to avoid kicking this jaw
clutch in while the input power is live.
When more space is available, a
drawworks skid with its own power can
be used. This is for larger rigs. On this
design, we find that the engine center-
John L’Espoir has enjoyed a 40-year career in
portable drilling equipment design. He holds
a bachelor of science degree in mechanical
engineering and was formerly the director of
engineering for the George E. Failing Co. in
Enid, Oklahoma. John was born in the Netherlands and moved to Enid in 1969. He is the
founder, owner, and president of Enid Drill
Systems Inc. He received the 2003 NGWA
44/ December 2009 Water Well Journal
Figure 1. Bearing patterns. Courtesy of Arrow Gear Co.
line is parallel to the drum shaft centerline, which eliminates the need for a
right angle drive.
guard.” Yes, catheads are dangerous.
They have killed and dismembered
operators before and will again in the
Whenever we even think of the word
cathead, we must immediately be “on
TRANSFER OF TECHNOLOGY/continues on page 46
Figure 2. Spiral bevel gear pinion assembly during inspection Figure 4. Failing 2500 drawworks with Failing air clutch style
of the bevel gear box on a Failing model LP-12 owned by the cathead. Photo by Gary Daly, courtesy of Daly Bros. in Australia.
U.S. Army. Failing is a registered U.S. trademark of GEFCO.
Failing is a registered U.S. trademark of GEFCO.
Figure 3. Bevel gear box cross section. Courtesy of GEFCO.
crowder pins. Activation could be
mechanical or by an air cylinder. Please
refer to the cathead cross section in Figure 8. The very same design has been
applied by Tillery and Parks (Figure 7).
Associated equipment with catheads
Rope splitter to keep rope from
Spinning chains. These are special
alloys and usually have a tail.
Guide rollers or pulleys to get to the
tongs, pipe, or casing.
Chain trays to keep the chain from
falling into rotating equipment such
as drivelines or chain drives.
TRANSFER OF TECHNOLOGY/from page 44
Catheads are used in many types of
industries successfully when operators
are properly trained. Some of their uses
Manila rope: used to drag in and
hoist light loads.
Used to operate sampling equipment
on auger drills.
Chains: used to spin pipe connections
together or to pull on tongs. Also
used to screw threaded casing
Wire line: used to pull on heavy
break-out or back-up tongs.
46/ December 2009 Water Well Journal
Caution: Never leave a manila rope
on a cathead that is rotating and look up
and down. Keep your feet out of rope
loops. Do not stumble and grab this
Catheads may be mounted on a dedicated shaft with or without a de-clutch
mechanism, or they may be added to a
drum shaft. Solid mounting can be used
for rope spools only. The chain and wire
line catheads must have an individual
The line of Foster catheads (in part
now owned by VARCO, Houston) has a
very interesting clutch. It consists of a
flat friction ring against which the bearing mounted drum is forced by three
In the catworks design, we find no
catheads! Pulling power is provided by
one or two double acting hydraulic
cylinders that pull on the chain. Speed
can be doubled up by using a pulley on
the end of the piston rod.
Caution: These cylinders are very
powerful. Remember 1000 psi means
1000 pounds of pull for just one square
inch. Pressures can be limited by a relief
valve, protecting the spinning chains
and/or tongs. The cylinders are usually
mounted in the back of the mast and
loads must be transferred into the main
joints of the mast legs. The driller has
full control of the cylinder/chain motion
and can stop this instantly from his
driller’s station. There is no clutch
release time or throttle down time
Figure 5. A Ewbank model M-450 drawworks powered by a Figure 6. EDSI chain cathead with internal air clutch. Barrel
Detroit Diesel 6-71 built for the Dowell-Schlumberger train- diameter is 6 inches and has a capacity of 5000 pounds single
ing center in Dubai, U.A.E. Note the KELCO series M12 cat- line pull. External brake package is optional.
heads. Courtesy of EDSI.
Figure 7. Courtesy of Tillery & Parks Co.
Catworks have appeared in our business since the late 1970s. They are
much safer than catheads and they are
more powerful; however, some drillers
today still prefer the catheads.
Figure 8. Breakout cathead assembly. Courtesy of GEFCO.
Unitized mounting must be provided
to install the bevel gear box, cross-over
shafts, and drum shafts. In addition, the
brake linkage and brake anchor pins
must be properly connected. When dual
brake bands are installed on a single
drum, the two anchor pins must be connected to an equalizer arm to provide
equal braking on each band. This arm
must be designed to allow some pivot
action; however, the stroke must be limited so that if one band gets away, the
other one still works.
Also, brake band and linkage adjustment points must be looked at. For dual
bands, a single point adjustment is preferred. Drillers tend to adjust only one
band (the one they can get to the easiest)
to get a brake and then forget the other
one. Larger drawworks install a link in
the brake system to act as a toggle. Care
must be taken to design a stop to keep
this toggle from going over-center and
lock the brake solid.
The drawworks frame must provide
operating space for “sloppy” drive
chains. Chains will cut through load
bearing cross members when they get
loose and are able to reach the steel.
Chain tightening procedures must be
designed into the frame. Keep in mind
that moving a drum shaft will disturb
TRANSFER OF TECHNOLOGY/continues on page 48
Water Well Journal December 2009 47/
Figure 9. Catworks installed on a Ewbank model M-100 at work in Michigan. The
two cylinders are 4-inch bore⳯6-foot stroke rated at 2500 psi. Photo courtesy of
Gerry Neubecker III at Raymer Drilling.
Figure 10. Dual hydraulic catworks on Lee Engineering Mast. The pulley (1) is
guided in the track (2) and will provide twice the speed and chain travel as compared to the cylinder (3) with a single line. Note: (4) shows catline rollers and (5)
shows heavy braces. The machine is on location in northeast Colorado and belongs
to Excell Drilling.
TRANSFER OF TECHNOLOGY/from page 47
the brake actuation or adjustment. A
chain idler adjustment assembly may be
Chain lubrication must be considered. Oil bath is preferred, although it’s
difficult to do because of all the centerline motion during adjustments. Brush
lube from a small reservoir is often
used. The oil path is just one way. After
leaving the chain, it is free to get into
clutches and onto brakes. Once these
areas are saturated, it can then fully coat
the drawworks frame, truck or trailer
frame, and turn the soil a rich looking
black. This is not good! The author
prefers a dry spray-on “MOLY” lubricant on sprockets and chains. It stays
where you put it, sand will not stick to
it, and it is friendly to the environment.
The drawworks frame style and design can be dictated by the other components of the rig. The author designed a
low-profile rig, designed to be air transportable in a C-130 by the U.S. Army,
while employed as the chief R & D
engineer at GEFCO. The key to this
design was to squeeze the drawworks
flat, having three drums and an external
bevel gear box (Figure 12). The rig is
mounted on a 6 ⳯ 6 truck, rated for
1500 feet, and yet it is only 8 feet high
with the mast down.
The two basic designs for a drawworks frame are:
48/ December 2009 Water Well Journal
Heavy side plates
Structural steel fabrication.
The army rig and our Ewbank model
M-100 use the heavy side plate design.
Note the cutouts to allow the lifting out
of shaft assemblies. The large drawworks with the 38 ⳯ 10 brakes is a
structural steel fabrication.
The drawworks frame must be bolted
or welded to the drill frame. Apply the
full single line load to one side only to
calculate the size and number of mounting bolts. Yes, a drawworks would pull
itself up on the wire line until clutch
power disappears. Then it comes down
with a bang! This is not good.
Figure 11. Dual 38⳯10 brake bands on structural steel type Figure 12. No. 1 is the bevel gear box. No. 2 is the drawworks
drawworks frame under construction at EDSI. Note the triple plate style frame. This is a special design rig for the U.S. Army.
pin equalizer connecting link.
Figure 13. Courtesy of EDSI. Ewbank Model M-100.
Heavy guards to cover drives,
clutches, drums, and brakes must be installed when operating the drill. It protects the operators, muffles the noise,
and keeps the friction materials dry.
Only remove these guards to perform
repairs or maintenance. Never climb inside the guard while the engine is running. Does this sound stupid? Well, yes.
However, the first lawsuit I was ever
involved in was because a man
crawled inside and got his foot cut by
a chain and sprocket. What happened
to common sense? As you can guess,
the lawyers got away with a truckload
of money. Who pays? The drilling
Figure 14. Location of operating controls on a rotary drilling machine (1943).
Courtesy of U.S. Army Manual.
Now just what is this? Tech manual
TM-5-297 from the U.S. Army war department, issued November 29, 1943,
explains it best:
Drill Head. The drill head consists
of a rotating mechanism, a hoisting
drum, a sand reel, hydraulic cylinders
for applying added pressure or
weight to the drill bit, and a hydraulic cylinder for moving the drill head
to and from the drilling position. All
these items, with their respective
controls and driving mechanisms, are
mounted on and within a cast-steel
fabricated frame. All gears are in
oiltight cases cast with the frame. All
other moving parts are well guarded
and are lubricated by pressure gun or
oil reservoirs. Power is transmitted
TRANSFER OF TECHNOLOGY/continues on page 50
Water Well Journal December 2009 49/
Figure 15. Rotary drill in operation, with a new drill rod being added (1943).
Courtesy of U.S. Army Manual.
Clutch throw-out collars and yokes
Clutch linkage and pivot pins
Wire line rollers
Spray-on “MOLY” type lubricant:
Service and operation suggestions:
Lube the entire drawworks.
Adjust and inspect sprockets and
Inspect drawworks frame for damage
caused by loose chains. Repair this
Check all nuts and bolts of drawworks and frame mounting.
Check auxiliary items such as rollers
Check bevel gear sets for proper
backlash, check bearings and seals
and fix oil leaks.
Check chains and sprockets for alignment, wear, and adjustment.
Replace your spinning chains.
Check relief valve settings on hydraulic catworks.
Check guards and frame for cracks in
welds. Repair immediately.
Install a centralized lube panel to
grease as many as possible lube
points from one location.
Resolutions to Make Today
TRANSFER OF TECHNOLOGY/from page 49
from the engine to the drill head by
universal joints on each end of a
splined telescoping shaft which connects the transmission to the drill
head power-input shaft.
To the best of my knowledge, Sullivan Drill Co. developed the drill head
concept. Other manufacturers improved
or expanded that design and it is still an
excellent component on today’s rigs for
the portable water well drilling market.
The drawworks may require both
oil and grease for lubrication. Please
inspect the following items.
Gear lube 85/140:
50/ December 2009 Water Well Journal
Bevel gear boxes (right angle drive)
Oilcan on all hinged doors on guards
All pillow block bearings and seals
All drum bearings unless they are
All brake linkage and pivot pins
1. Write an inspection schedule for the
following items and stick to it:
a. Chain drives—open and enclosed
b. Bevel gear boxes
c. Bearings and seals
d. Guard assembly
e. Mounting to frame
2. Determine what maintenance tools
should be on the rig.
3. Record any applicable numbers or
items such as catheads, gear boxes,
5. Obtain parts and service manuals for
these from the manufacturer who
built the rig.
5. Establish a personal contact with
engineering and parts supply staff.
6. Last but most important, hold a
safety meeting with regard to proper
operation of a cathead. Keep records
in the personnel files.
Coming Next Month
Hydraulic winches: Can they be used as
a drawworks? What is the advantage?
Why do some rigs use a hydraulic cylinder to replace the drawworks? WWJ
Waiver: The views expressed in this
article are the author’s opinion and are
based on the engineering education,
skills, and experience gained in a lifelong industry commitment. No part of
this article is intended to replace or
supersede any information supplied by
others. The contents of this article may
not be used in any type of legal action.
This series is dedicated to the education of John L’Espoir’s two grandsons,
Ethan Daniel Atwood and Elliott John
Atwood (right), who are each destined
to become a drilling rig engineer.
Opposing points of view or questions?
Contact us at Enid Drill Systems
(580) 234-5971, fax (580) 234-5980,
Interested in the book Transfer of Technology? It is available in the NGWA
Bookstore. The member rate is $75; the
nonmember rate is $87.50. Call NGWA
at (800) 551-7379 to order your copy
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Water Well Journal December 2009 51/