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Frequently Asked Questions
Off-Road Driving Info Sheet and FAQ (ORDFAQ)
Version 1.2
Full release |
Print date: Sunday March 31, 1997
First begun Friday July 26, 1996 |
Compiled by Mike Graham <mike@headwaters.com> |
1 Why an ORDFAQ?
At the time that I purchased my
LandCruiser, My off-road experience had
been limited to dirtbikes. I knew that there were significant
differences
between off-roading on a dirtbike, and off-roading on four wheels,
but I
couldn't find a source for hints on how to get up that gravel wash
without
spinning back down again, or how to cross a slope of tuff without holing
a
tire. This FAQ is an attempt to rectify that situation.
Why not just have this information in the standard Off-road FAQ?
Well,
it's just not there, now, and besides, I felt that compiling this FAQ would
help me learn about off-roading on four wheels. It has.
Note, please, that this FAQ is not intended to be the be-all and end-all of
Off-road information. Many aspects of off-road driving simply
cannot be
learned from the printed page, but rather must be learned from the untrodden
path itself.
2 Where to get it
The ORDFAQ is available for download
through the world wide web by
connecting to:
<http://www.off-road.com/~mike/index.html>
The above mentioned web page also
has an on-line version of the ORDFAQ
which allows you to scroll through it on-line.
3 Lawyer Drivel
Here we go.
There is no guarantee, expressed or implied, that
this information is
either useful, or accurate, or both. It is merely the personal
opinion of
the applicable author. Use it at your own risk. I could be
a psychotic
delusional who delights in the thought that other people are going to wreck
their trucks trying to follow my advice. Use your own discretion, and go
slow until you know what you're doing, then you can assess the
risks for
yourself.
This collection of information is copyrighted by myself, Mike Graham.
You
can look at it, share it, collect it and trade it with your friends, but you
can't try to sell it, or make money off
of it without my expressed
permission.
4 Sharing the blame
The following have contributed (officially, or
unofficially):
- Chris Siano <csiano@banyan.com>
- Jim Hassi <jhassi@foothill.net>
- Dean Waters <dwaters@off-road.com>
- John Donovan <jdonovan@newbridge.com>
- Timothy W. Welden <tim@ai.com>
- Guy Hammer <guyh@teleport.com>
- Dave Dannenberg <suedave@pond.com>
- Chase Gregory <cgregory@surfsouth.com>
- Greg Spangler <spangler@noclant.navy.mil>
- Kendra Cook <kendra07@4x44u.com>
- Mark Whatley <cruiser@akcache.com>
- Dmitry Struve <dmitry@uask4it-101.eng.sun.com>
- Christian Falzon <christian@mail.waldonet.net.mt>
- Runar Sigurjonsson <runars@isbank.is>
5 Future Plans
I didn't deal with anything mechanical, really,
but I'd like to see hints
on common trail-side repairs and jury-rigs.
Ultimately I'd like to see a section of the ORDFAQ
dedicated to trail
problems. For instance, if you were planning on running a popular trail, you
would check the listing in the ORDFAQ and find out whether
it would be a
really good idea to take an extra spare tire, or iron rods to use
as a
winch anchor. It's a way to share knowledge. Also, I'd like information
on
whether full-size vehicles can make it through, or only 'Zukis and
chopped
Broncos.
6 What can you do
to help?
Point-form trail reports would be
nice. If you know a trail that isn't
listed in the FAQ yet (or if you know
information missing from the
description in the FAQ) then let me know! Here's
a list of headings to
choose from to fill in for trail info:
Trail Name: Whatever the standard name is (or
names are)
Location: City/area/country other
info to help (like 5 miles north
on the I-5 from Hampton, Conn or something). If you know
the coordinates of the trailhead (for the guys with GPS
equipment) then please add it.
Difficulty Rating:
Specify also, what the rating base is (Rubicon? Alaska?)
and preferably also give a general description.
Scenery Rating:
Just a number from 1 to 10 describing how scenic you feel
the trail is. Some highly technical forest trails have
nearly zero scenery, and that's fine if you're just after
a challenge, but if a person is looking for a nice view,
they should be able to find one.
Restrictions: Short wheel base only? Skinny trucks
only? Summer only?
Lockers only? Winch a must-have?
General Terrain:
Just a vague bit of info to let people know what they
might be getting themselves into. Like 'Desert and scrub,
some rocks, but nothing serious.'
Special Problems:
Real easy to hole a tire? Deep water crossing?
Overall Impression:
Did you enjoy the trail? Was it too relentless, too much
easy driving between hideous obstacles?
In addition I really need info on taking automatic transmissions
off-road
(is the compression braking sufficient to take you down a hill?) and info on
obstacles that I'm not familiar with (sand, cane, tricks for bog/muskeg etc.)
I need suggestions for the 'Trail Etiquette' section.
That's a section
that I never even thought of, yet it is very important. I just
tossed it
together prior to posting 0.00b (turns out 0.00a only went to list
members
who are set up as 'realtime'). Any input is appreciated.
7 History
- 0.00a 8/26/96
First Pre-release to the Off-Road list.
- 0.00b 8/29/96
Second Pre-release. This
release added the 'Trail Etiquette'
section, and the 'Getting
Unstuck' section. Many other little
upgrades, as evidenced by the number of additions to
the 'Sharing the
Blame' section.
- 0.00c 9/05/96
Third Pre-release. I'm not getting
as much feedback as I'd like,
so I'm sticking with pre-releases for now.
No one has mentioned a
desire to write an article on driving in specific
conditions (snow/mud
whatever) and I'd like to have those articles done
before I release
1.00. This version has had
the section on winches added, and the
'Etiquette' section increased.
Several valuable additions to the
'obstacles' section, as well.
- 1.00 9/19/96
First official release. It doesn't have all
that I want in it, but
it's time to put it in long pants.
I've added the section on
slingshot extractions, and expanded the Mud
section (thanks to the
Great Lake Extraction of '96) as well as some
info on using a Hi-Lift
jack for extractions (which I am now an expert at
8-/)
- 1.01 10/21/96
A slew of new info has come in in the form of
an excellent article
on water crossings by Runar
Sigurjonsson. Additional information
dealing with automatic transmissions and CB antennas
crept in when I
wasn't looking.
- 1.2
03/31/97
Lots of slippery-conditions info. Now
that winter is here, I am
doing a lot of testing
regarding driving on slick surfaces. The
underlying format of the
FAQ has been changed. Instead of
using a word processor as has been
the case in the past, I am now
editing it directly in the text version.
A bit simpler in the long
run.
8 Vehicle
Familiarization
Before you can safely point your wheels at the great
beyond you need to be
familiar with your vehicle, and take some precautions.
What is your ground clearance? How big a rock can you drive over
without
worrying about it hitting something tender, like a gas tank?
Is everything strapped down? If you roll, you don't want to get smoked
in
the head by your toolbox. Is the battery restrained? If the battery
jumps
out of its housing it can short against the
hood, or another engine
component, causing big grief.
What is your approach angle? If your bumper hits the
slope before your
wheels do you'll have to come at it from an angle.
Similarly, what is your departure angle? If you exceed
your departure
angle then your rear bumper will hang up on the hill and your rear
wheels
will leave the ground.
Where are your differentials? Drivers side? In the
middle? This is
important to consider when you're going over obstacles.
Can your engine run at an angle? If it's carbuerated, a steep
grade can
drown it post haste. Fuel injected vehicles generally handle steep
grades
better. Diesels and cylinder-injected gas trucks can pretty much run upside
down without dying.
Does your vehicle have a high center of gravity, making it more susceptible
to tipping and rolling? Most jeep-like vehicles share this fault to various
degrees.
Do you have full wheel travel without hitting the fenders?
If you have
monster meats on your truck, it's quite possible that before the axle
hits
the bump-stop the tire hits the fender. Jack up one front wheel high enough
for the axle to hit the bump-stop and run your hand around the tire to see if
it's hitting anything. Now turn the wheel full to the left and check.
Now
turn it to the right. If it hits anything then you have to decide
whether
you want to tear up your tires or not by doing serious off-roading. Check a
rear wheel, too.
Does your vehicle have a big, long 6' whip antenna that's going to injure a
bystander or spotter? Long whip antennas aren't
even allowed on some
trails due to the damage to the environment that they can inflict.
9 Safety Check
Now is the time to consider whether any of your fluids are
low. Got enough
power steering fluid? Enough oil? Enough coolant? How
about windshield
washer fluid? Have your brakes been checked fairly recently, or
might you
need to replace the pads/shoes? If you're traveling in a
group at night,
it's worth checking your taillights. Even alone at night you want headlights
and reversing lights that work.
10 Safety Gear
The amount of safety gear that you need will
depend on several factors.
The first is how hard-core the off-roading is that you're doing, the second
is how remote an area you're going to, and the third is based on the climate
of the area you're going to.
When I'm just booting around in my back field I don't bother taking
much.
If I get stuck or broke, I just walk back home and get the
tractor. If,
however, I was doing a four-day solo enduro through Death Valley, I would be
taking significant precautions.
If you're traveling as one vehicle in a party, then the danger is obviously
not so acute. You can get a lift back home with someone else and come
back
with spare parts later (hoping against hope that no unscrupulous type finds
your truck in the meantime).
10.1 Minimum Gear
This is the stuff that should be kept in the truck at all
times. Add to it
when you're doing more serious off-roading.
- Spare tire
- Jack and handle (stock jack is fine)
- Lug wrench that FITS. (been there, done that, didn't like
it.)
- Blanket
- Fire extinguisher (1A/5BC or other approved for auto)
10.2 Remote Gear
If you're going back of beyond
(especially by yourself) then you really
should take precautions. Any mechanical breakdown that you can't
fix or
jury-rig could leave you stranded. Don't
scrimp on the navigational
equipment if it's unfamiliar turf; you can't
always count on your St.
Christopher medallion to get you home on time. 8-)
- First Aid kit AND THE KNOWLEDGE TO USE IT!
- Do yourself a favor and take
along some food and water for
emergencies, and waterproof lifeboat matches.
- Tire irons and an inner tube or an extra spare.
- Compressor or manual tire pump
- 2 Gallons of water for the rad (or a filter to
strain groundwater if
it's available)
- 1 Gallon of engine oil
- 5 Gallons of spare gas/diesel in a jerry can
- Appropriate manuals for the vehicle to aid in trail-side
repairs
- A CLEAR understanding of where you're going,
or at least how to get
back.
- Navigation gear (map&compass, GPS, local guide, whatever)
- Replace regular jack with a Hi-Lift jack (or Jack-all) 48"
min.
- Jack pad sufficient for the vehicle's size and terrain traveled
- If using a Hi-Lift as a winch, you need blocks to keep
the truck from
rolling backwards during the 'taking in the slack'
phases.
- A tow-rope is still a good idea, even alone.
11 Trail Ettiquette
In this day of trail closures and EPA
pressures, it is more crucial than
ever to tread lightly. To this end, I have assembled some guidelines divided
by terrain type.
11.1
General tips on Treading Lightly
None of us want to see our trails closed down.
Few of us want to see our
environment destroyed, either. It is the duty of all off-roaders to consider
the ramifications of leaving a beer can, or shredded spare tire lying on the
trail. Would you want a news crew with their cameras catching your garbage
and suggesting that all off-roaders are
insensitive to environmental
issues? It has happened before, and it will happen again. Don't
let it be
your mess.
To contact the groups dedicated to keeping our
trails open, see these
websites:
Tread Lightly:
<http://www.treadlightly.org/>
United Four Wheel Drive Association:
<http://www.ufwda.org/>
BlueRibbon Coalition:
Site is under construction. You can get information at
<http://www.4x44u.com/pub/k2/am4x44u/events/clubs/blue_rib.htm>
- Don't spin your tires.
- Don't run more aggressive tires than you need
(lugs chew up the
ground)
- Don't litter (cigarette packs, drink cans, oil containers,
etc.)
- Don't play obnoxiously loud music when others are around.
- Don't blaze a new trail; stay on the established path.
- Always use a tree strap when using a tree as an anchor.
11.2 Rocks
- If you need to pile stones up to get over an
obstacle, then put the
stones back where you found them afterwards.
- Don't leave oil spills, shredded tires, or other
materials on the
trail. Clean it up and pack it out.
- Try not to scrape up the rocks.
11.3 Forest
- Don't cut down trees, and try not to tear branches
off while driving.
- Your vision is limited by the trees; don't go
flying around a bend
only to smash into a disabled vehicle, or run over a
hiker.
- Keep to the trail. If the mud is too
deep to get through, then you
shouldn't be on the trail in the first place.
If everyone cuts a new
set of ruts, the trail starts to look like a
battlefield. Use a winch
to get through.
11.4 Right Of Way
The right of way on a
trail is basically like that on the ocean.
Generally, everyone just stays out of everyone else's way.
Pass on the
right, veer right in head-to-head situations, etc. If there's only room for
one vehicle at a time, then channel rules take over and the more maneuverable
vehicle should make way. If it's a situation where only one vehicle can pass
at a time, then the drivers must decide amongst themselves who goes
first.
Usually this amounts to just a 'waving through', but sometimes it requires a
bit of discussion on foot.
In the event that you find yourself head-to-head with someone on a
single
line, so that one person has to back up or move aside to let the other pass,
the more capable vehicle should get out of the way, as the
less capable
vehicle might not be able to make it back on the trail.
Sometimes these rules don't work so well; if the guy driving a stock Sammy
knows his stuff he can easily outmaneuver a modified Jeep driven by someone
who isn't really familiar with off-road situations. The
primary thing to
remember is that bad things happen when people don't know what's going
on;
make sure there is clear communication, and the other driver knows
that
it's your turn to go.
When two vehicles meet on a grade, the vehicle traveling uphill should
have the right of way, as it is much more difficult to get going again when
you're pointing uphill as opposed to downhill, and backing up uphill is safer
than backing up downhill (as long as it's done smoothly so as not to stress
the front axle).
When two vehicle meet head to head, they may need to pass
on the left.
When there is a sharp shoulder dropping to a deep ditch, for
instance, you
need to drive with the drop at the driver's side so that you can
see more
clearly where the edge is.
Again, these 'right of way' rules are general at best! Unless both parties
know what's going on, and accident can happen.
Make sure there is
communication. If needed, get out of the truck and chat for a while.
Maybe
the rules have to be bent to avoid a truck being bent. You can't just chug on
assuming that the other truck will move just because you are supposed to have
the right of way.
12 General OR
Driving Hints
Friction is your friend. With friction, you can
move. Without it, you are
stuck.
There are two kinds of friction; static, and dynamic. Static
friction is
the kind you have when your wheel surface is not moving
relative to the
surface you are driving on (i.e. when you are
not skidding). Dynamic
friction is what you have when you are skidding. Static friction
is much
more powerful than dynamic friction. It is for this reason that
threshold
braking will stop you quicker than just stomping on the brake
pedal and
skidding to a stop. So the key in the vast majority of situations is to try
very hard not to spin your wheels.
Don't drive with your thumbs wrapped around the steering wheel.
Even if
you have power steering it's possible for the wheels to fall into a rut
or
something that will crank the steering wheel to one side, and possibly break
a thumb. Nasty.
Driving off-road isn't like driving on-road; you can't just choose a
line
and insist upon it; the truck will let you know what it wants to do. Keep it
more or less where you want to be and just
'suggest' directions to it.
Anyone who rides a horse knows what I'm talking about.
"Drive as slowly as possible, and as fast as necessary." Andy Philpot
Don't straddle rocks or they'll smoke your diffs; ride the wheels over them
to raise everything out of harm's way.
Ditches and ridges should be crossed at an angle (like railroad tracks) to
keep you from getting bogged down when both front or back wheels drop
into
the ditch.
Be wary of water crossings. What you don't know can hurt
you. See the
section on water crossings below.
Airing down your tires to 15psi or so will increase your contact patch and
increase friction. Don't do it unless you have some way to re-inflate
your
tires, though. In some technical rock-crawling situations people
will air
down to next to nothing (2 pounds or so), but I wouldn't advise this for the
uninitiated as you could blow a bead.
Maintaining speed on bumpy terrain can be very
difficult because the
pitching of the truck throws your foot (via momentum) into the gas
pedal,
causing the truck to surge, causing more momentum, causing your foot to get
thrown harder into the gas pedal... It's ugly. There
are two regular
solutions: the good way, and the sort-of-works-most-of-the-time way.
The
good way is to have a hand throttle. A hand throttle will keep your vehicle
moving as smoothly as possible. The other way is to keep the side
of your
foot planted against the transmission mound, operating the gas
pedal only
with the ball of the foot. This keeps your foot planted, so it
can't go
flailing into the gas pedal. At least, not as much.
If you drive a late-model truck with air conditioning, it might
be worth
shutting the AC off when you're in a tight crawling situation, as
the AC
compressor will kick in at odd moments and cause the idle speed to
jump,
which is at best a pain, and at worst could pitch you off of your line
and
drop you on a rock.
Some hints from Chris Siano:
[BEGIN]
Driving posture is something I've
never seen printed fully
anywhere.
Things like, seat up, sit a little closer to the
steering wheel,
thumbs out of the wheel, foot resting on the
transmission hump to
keep vehicle from surging as it bounces over the trail.
Seat belt!
Prepare for getting stuck. If you and
your buddy are going out,
and you have an old CJ and he has a Cummins Dodge, there is
no way
you are going to pull his truck out of bumper deep mud.
Therefore,
don't get into bumper deep mud. If the strap is 30'
long and the
mud is 200', there is no way you can pull anyone out of the
middle.
I guess, the best way to sum it up is to be sure to look before
you
leap. It only takes one big stuck
and a 4x4 wrecker or tractor
extraction to realize how important this is.
Lastly, a new driver really needs to know the size of his
vehicle.
If you don't know where the tires are, you
can't put them on the
rocks. Only takes an hour in an empty parking lot
with some cones
to learn how wide your rig is, and how tight you can turn it.
This
is especially useful in full size trucks as you can't see
anything
on the passenger front any closer than about 10
feet away. This
time spent can easily save lots of time and $$ in damages
to a new
truck.
[END]
This point about knowing where your tires are is very important.
Most
people use points on their hood to estimate where their
tires are. This
works fine as long as your head is always in more or less the same
place.
This means you should have a standard off-road seat location and
seat-back
angle and stick to it. With your head in the same
place all the time,
you'll be able to judge your tire location much more effectively.
13 Getting Unstuck
Everyone gets stuck. You ever seen a tank winch?
Well I have. Even they
get stuck. So how do you get unstuck? Lots of ways.
13.1 Winches
The easiest, fastest way most of the time is to use
a winch. See the
section in the FAQ on "Which Winch Is Winchiest?" for info on the
pros and
cons on the different types.
With a winch, a snatch block (a pulley with a hook on it), a tree strap (to
keep from maiming the local flora), and SOME LEATHER GLOVES,
you can get
yourself out pretty quick from just about anything.
Normally you just need to single-line your way out. Just switch the
winch
to freewheel, pull out the line to the nearest big tree, throw the tree strap
around it, hook up, and pull yourself out. If the winch stalls, then hook in
the snatch block (when using a snatch block, hook the end of the winch line
to your tow hook, not to the winch mounting itself, or you might
tear the
winch right off your truck).
If you're winching someone else out of the mud, and
your truck keeps
skidding towards the vehicle you're winching, then you need to
either put
good-sized blocks under the wheels (like SureClaws) or attach your truck to
an anchor (like a tree) but connect the line from the anchor to the end
of
your vehicle that has the winch on it, otherwise you might end up physically
stretching or twisting your truck frame. Bad stuff.
If you keep stalling the winch, even with a snatch block, then you have to
reduce the workload. Try putting chunks of wood in front of the
wheels to
act like ramps to keep the wheels from plowing deep furrows in the mud.
If
you're winching over rocks, then try piling up smaller rocks to make ramps.
Hopefully you won't have to unload your truck.
If you've had trouble with your winch not being powerful enough (i.e. your
wife gave you a 3000pound winch for Christmas and it's the first
official
acknowledgment of off-roading she's ever made and you just know that
you
can't take it back) then a last-resort possibility is to have extra
snatch
blocks. With three snatch blocks you can set up a block and tackle that will
give your winch 4X its normal power. This is good, unless
the tow hook
to which you attached the block and tackle
can't handle it and tears
itself off the truck. Then it's bad. In addition, you won't have more
than
about 20 feet of pulling capability, because the wire will
be doubled up
around the pulleys so many times. Whenever you are
using a winch of
any variety it pays to lay a coat, sleeping bag, or other largish,
soft
object over the line, so that if the line snaps it will be less likely to be
really dangerous.
13.2 Winch Alternatives
There are several things out there that aren't winches,
but are supposed to
do the same job. One is a Hi-Lift jack (HLJ) or similar jack, and another is
a come-along ratchet hoist. An HLJ is meant to be able to pull 7000
pounds
or so (says the weight rating on the box) and the mechanical advantage is so
high that it doesn't feel too scary to use it. If you're using an HLJ as a
winch then lay the jack right on the ground with the handle pointing upwards,
that way you can put a foot or something on the end of the i-beam to keep it
from lifting when you're trying to lever the jack handle.
A come-along is a different animal, indeed. It has a short
handle (less
than a foot long) and gives you significantly less mechanical
advantage.
They are usually rated only a few thousand pounds when
double-lined (i.e
while using a snatch block). They way they creak and groan
while you're
using them, standing 10 inches away from the thinnest cable ever seen on
a
winch-like object scares me to death. I don't like them, but they can
save
you if you have nothing else. Definitely use the coat trick
when dealing
with these. Due to the short length of them, they don't stay parallel to the
line of force very well, so it's very frustrating to use them (they
wobble
and pitch when you're trying to work the lever). I don't like
them, but I
must admit that I have one in my pickup truck. Just in case. I keep an
HLJ
in my 'cruiser, so I don't need one in that. The one benefit of a come-along
over an HLJ is that the come-along will pull for 20 feet or so, whereas the
HLJ will pull for less than 4' at a time (limited by bar length; could also
be 3' or 5' depending on jack model). To use an HLJ as a
winch requires
blocks, or some other way to keep the truck from losing ground while you're
resetting the jack. To be fair, there are some come-along models out
there
that are pretty tough. If you get one that's rated to 4000
pounds or so,
then it should be able to actually pull you out of a bad situation. If
you
plan to use an HLJ as a winch alternative, then make sure you have hardware
on hand to do it; you can't thread a
3" wide tow strap through the
little hole in the jack. Get a clevis that fits.
13.3 Traction Pads
Those ladder-like things for ice and snow can be a
blessing, or a curse. A
couple of those beneath your wheels will usually get you going again. For a
couple of feet. Then you have to stop and pick them up. If
you're using
these, put it in granny low, let the engine just idle, and feather
in the
clutch. You don't want to spin the wheels on these
things because it is
possible to send them flying into whatever is in their path (other vehicle,
the underside of your vehicle, you...)
Regular ladder-type pads don't work in mud (they just sink)
but they're
great on ice and slicked snow. For mud you need something with a semi-solid
surface that will stay on top of the mud. You might think that an old
ski-
doo track would be great. They almost are.
In shallow stuff they work
great, but in really deep stuff they let the tire push them down, and
your
truck just ends up having to drive 'uphill' against the mud. They still work,
but not as well.
The ultimate traction aid is a pair of 15' 2x10s. Jack
up each side of
the vehicle and put the boards under both wheels on each side and you
can
get out of just about anything. Tough to transport, though. 8-)
13.4 Jack Tricks
With a jack that will lift at least a corner of your
vehicle 6" or so (even
a stock jack will do it) you can lift the wheel and stuff traction material
under it. Floor mats. Rocks. Sand.
Dead branches. Kitty Litter.
Irritating relatives. Anything. Lower the wheel again, and
do the other
side (or all four corners) and you should be able to get going.
13.5 Slingshot
Extraction
I wasn't sure whether to include this because
the potential for tragic
results are great, indeed. Still, as long
as you understand that you
really have to be careful doing this, and understand the risks
involved,
then it might get you out when nothing else will.
[Christian Falzon writes:]
First a disclaimer:
This technique may be EXTREMELY dangerous if
not done properly (
maybe that's why no one mentions it ) - so make sure you
know what
you're doing. My description here is only a rough guide,
the exact
technique, rope type, etc. are up to your judgement -
though I'm
sure that many others will contribute such
information. It also
needs considerable skill to be done safely.
The technique is snatch pulling and is (in principle) very
simple.
You need:
1. A very stretchy
rope. This should be about 2 inches in
diameter and made of
nylon.
2. A bogged down or
stuck vehicle (you wouldn't be trying to
pull it out if you
didn't have that :)
3. A vehicle which is NOT bogged down and
has at least 25 feet
of clear ground on
which to accelerate.
4. VERY ROBUST tow points on both
vehicles.
When to use it:
This technique should only be used as a last resort - it is
to my
knowledge the most powerful way of pulling a vehicle loose -
except
for using an Abrahams tank or a Sikorski Sky Crane.
Unfortunately
it is probably also the most
dangerous and I have seen some
incidents which could have had a very nasty ending if
it weren't
for tons of luck. The pulling force that you can generate
(if done
properly) far exceeds that of any winch or conventional
pulling -
even if the towing vehicle is on very slippery ground.
Basically all you do is
1. Fasten the rope between the
two vehicles, just as if you
were going to tow.
2. Back up the mobile
vehicle as close as possible to the
bogged one. Make sure
that the rope is laid out neatly on
the ground and cannot
get tangled or caught in anything
3. Make every bystander get the heck out
of the way - AT LEAST
twice as far as the
length of the rope
4. The bogged/disabled/stuck
vehicle should be started if
possible (and should
contain a driver :-)
5. The towing vehicle accelerates forward
- do not overdo it.
6. The slack in the rope will be
taken up, but the vehicle
should continue
accelerating. At the same time as the rope
comes under tension,
the bogged vehicle should do its best
to move as well.
7. As the vehicle keeps moving forward,
the tension on the rope
increases more and
more, in the process slowing it down.
This deceleration can
be very rapid and a driver not wearing
a seatbelt will almost
certainly smash into the windscreen.
8. Hopefully the tension in the rope will
be enough to pull the
other vehicle loose.
In any event, once the towing vehicle
stops moving forward,
the tension in the rope will start
accelerating it
backwards with great force. The driver
should be prepared for
this and immediately press the clutch
and use the brakes. The
vehicle should then be eased back on
the brakes until there
is no longer tension.
9. If this doesn't work
just back up again and repeat the
snatch pull
with a heavier right foot until you are
successful.
IMPORTANT tips that may keep you and others alive:
1. The drivers in the two
vehicles MUST MUST MUST MUST wear
seat belts and
certified crash helmets.
2. The towing points on both
vehicles must be VERY robust. The
force generated by
snatch pulling can be of the order of
several tons - up
to about four times the weight of the
towing vehicle (even if
only for a few seconds). If you are
not sure about
the strength of the tow points you are
inviting disaster.
3. The rope should be tied directly to
the towing point - NO
metal fittings such as
eyes or shackles may be used.
4. The vehicles must both have roll cages
(real ones not chrome
decorations)
5. Everybody else (spectators
photographers and whoever) MUST
stay at a distance of
at least twice the length of the rope
being used. If
anybody insists on staying (perhaps to take
photos or something) DO
NOT PROCEED until he gets out of the
way or you are sure
that he's Bill Gates.
6. Use decent knots to tie the
rope. The knot should be as
small as
possible - consult some good seaman or rock
climbing junkie
for the best knot to use. It is important
that the knot be as
small as possible.
7. If at all possible avoid snatch towing
a small light vehicle
(eg. a Sammy) with a
much heavier vehicle (i.e. anything :-)
8. Make sure that the towing point
does not have any sharp
edges that may cut the
rope
9. DO NOT use a rope which does not
stretch - AVOID AVOID AVOID
chains, steel ropes,
Kevlar, Carbon fibre, 'pre-tensioned'
or non-synthetic
ropes. The rope should be Nylon or a
similar material
which can stretch to almost twice its
length without breaking
and must have a breaking strength in
excess of 25 tons.
So what exactly is so dangerous about it?
What we are doing here is changing
the momentum of the towing
vehicle into energy stored in the tow rope. Its like
we are using
the towing trucks engine to 'wind-up' the rope. What this
means is
that all the energy that your fire-breathing
V8 has produced in
those seconds of acceleration is now STORED IN THE ROPE ready to
be
released at an instant if something goes wrong. What we want is
for
that energy to pull the bogged vehicle out of its mud-hole but
what
if it doesn't do it?
The main dangers in order of magnitude are:
1. The worst that can
happen is that the towing point (or
indeed a chunk of
chassis) of one of the vehicles gets torn
off. If this
happens, the piece torn off will shoot off
(accelerated by tons of
tension in the rope) and can easily
reach speeds of almost
500mph (yes five hundred miles per
hour) depending
on the size of the chunk extracted. I can
leave it to your
imagination what happens if said chunk hits
someone.
2. If too much force is used at once, the
bogged vehicle may
come loose with the
rope still having lots of stored energy
to spare. This stored
energy then makes your newly de-bogged
vehicle accelerate
faster than an F-15 on steroids and
literally go airborne
and come crashing down (most likely
onto the
towing vehicle - been there done that). The
important thing
is that you always start gently and
GRADUALLY use more
force at each attempt.
3. The rope may break. This usually
happens where it is in
contact with the tow
point. This results in a missile launch
similar to when the tow
point breaks except that this time
only the rope is
flying. That is why the knot should be as
small as possible.
A messy multiple knot will easily smash
through a
steel body panel at that speed. The smaller the
knot, the less the
damage it will cause. Having said that,
even the rope itself
can be lethal but you have made sure
that everybody is far
away. The drivers of the vehicles are
not normally
in danger since the rope will get tangled in
the vehicle and also
lose most of its energy before reaching
the driver. One
may still get injured if extremely unlucky
however.
Horror stories:
I have seen two near accidents caused by
improper snatch towing
which could have had a very nasty ending.
The first instance involved two Land-Rovers about six years ago.
No
amount of winching would make the bogged landy budge. Also
digging
was impossible as the mud was too fluid and Hi-Lifting
impossible.
So they went for snatch pulling. Even the most violent
acceleration
brought no results. They then decided to use two
ropes (to double
the length) with the result that the towing Landy reached speeds
in
excess of 40mph!! before the rope slack was taken up.
Just as the
Landy started to loose the battle against the increasing tension
of
the rope an appalling impact and what sounded like a rifle shot
was
heard. The tow rope seemed to have vanished. What had
happened was
that the towing point of the stricken Landy was pulled right out
of
the chassis and catapulted at awesome speed
towards the towing
landy. It went right through the rear
door, the bulkhead and
through the front windscreen, scattering bits of glass and
aluminum
all over the place. The towing point had actually
passed within a
few inches of the drivers head!! He
was wearing a helmet but I
doubt what protection that can afford against
a 6 lb supersonic
towhook!
So what did they do wrong? The worst thing was to
use too much
force without thought about the consequences. One
must stop and
think about an alternative before just applying more and more
brute
force.
The other incident involved a Land-rover de-bogging a
Sammy. What
happened this time was simply that maximum
brute force was used
right away. The Landrover accelerated about 20 feet to approx
20Mph
before the rope started tensioning.
All of a sudden the Sammy
catapulted out of the ground flew a distance of about
25 feet and
came crashing into the roof of the Landy just
above the level of
the tailgate. The only thing that prevented the driver of the
Landy
from getting killed was the substantial rollcage.
What went wrong
here was very simply that maximum brute
force was applied first
time. There was probably four times as much energy in
the rope as
was needed to debog the 'Zuki.
The moral of it all: snatch towing is a great
way of recovering
otherwise unrecoverable vehicles. I have
seen many otherwise
unrecoverable vehicles (even my mog) recovered by
snatch pulling.
If done with care, it is safe but if not can be lethal.
Always try
winching, HiLifting and digging before snatch pulling.
[ How's that for an explanation? ]
So we've heard what the process can do, and we've heard a whole lot
about
what can go wrong. Bottom line? If nothing else works, this might,
but be
darn careful if you try it. It's really not that scary at low speeds (10mph
max). Here is a table supplied by Guy Hammer that tells you how much
force
can be exerted by various weights of vehicles at various speeds:
Vehicle/Snatch-strap load impact (in ft./lbs. energy)
Speed
Vehicle Weight (lbs)
(mph) 3,000 4,000 5,000
6,000 7,000
===================================================
5 2,506 3,341
4,177 5,012 5,847
10 10,024 13,365
16,707 20,048 23,389
15 22,554 30,072
37,590 45,108 52,626
20 40,096 53,462
66,827 80,192 93,558
30 90,216 120,289
150,361 180,435 210,505
50 250,604 334,135 417,669
501,207 584,736
Strap capacities:
2" - 18,000
4" - 36,000
6" - 54,000
12"- 108,000
Note: The tow hooks I have seen for sale are
only rated for
10,000 lbs. As best have I have been able to
determine, the
two 1/2" bolts that hold them to
your frame could break at
14,000-15000 lbs. Having a tow hook imbedded in
the back of
your truck (or skull) could ruin your entire day!
(And no, I
don't know anyone crazy enough to hit the end of a
12" strap
at 50 MPH!)
From this we can see that a 3,000 pound vehicle at only 10 miles per
hour
can apply more power than most of the electric winches on the market. A very
powerful tug, indeed. High speeds make for a tremendous amount
of power.
Always always always start with small tugs at low speeds. There's no
sense
in tearing the towing points right off of the vehicles.
The previously
mentioned tug by the 3,000 pound vehicle at 10mph will apply as much force as
the stock towing points in many new vehicles are designed to take (the wire
loop tow points found on many newer vehicles are an example).
The reality of the situation is that many people use
snatch pulling as
their primary method of extraction, and think nothing of it.
It can be
safe if done properly at reasonable speeds. I use snatch pulling
to pull
people out of ditches. When you're using it, don't be in a hurry to use more
power; use a whole bunch of small pulls rather than a huge brute
tug. I
pulled a minivan from the bottom of a 6' ditch while I was on glare ice
by
using small tugs, and lots of them. I gained maybe an inch each
tug. It
adds up, and eventually he came out. Try to get a rhythm going so that
you
aren't in gear when you hit the end of the strap; rather start going and let
the inertia of the vehicle pull you forward, then you will
recoil on the
strap and you can just stay in a forward gear and use the clutch to 'bounce'
on the end of the strap. If I had to shift into reverse for every
tug I'd
still be tugging away at the guy I pulled out of the ditch last night.
14
To Spot, or Not To Spot? The battle rages
Every pastime has to have a major bone of contention or
two, and this is
one of the biggest in the off-road arena. Some people love
spotters, some
people hate spotters, some people don't know what a spotter is.
A spotter is someone who is outside of the vehicle, and is supposed to
be
seeing things that you can't see from your vantage point behind the
wheel,
and passing the information on to you, so that you can make more intelligent
decisions during intense rock-crawling.
In my dirtbike background, there is no such thing as spotters.
When you
can see all of your tires, why the heck would you want someone telling
you
how to drive?
With big vehicles, it's a bit different, as evidenced by the following:
Chris wrote:
Don't forget about using a spotter. Only ONE spotter,
any more, and
you might as well not use any. Trust the spotter, he
or she can see
things you can't. In many cases, a good spotter is better than a great
driver.
Dean wrote:
Am I the only one out there that doesn't like to use a spotter?
It is
very rare that I will watch or would like a spotter. I much prefer
to
use my own judgement as I know my vehicle better than most spotters. If
I need help or an extra eye on the other side then I will ask for it at
that point.
Otherwise I would rather they just shutup and let me
do my thing.
Maybe I have just seen too many BAD spotters. :-)
Jim wrote:
Learning how to wheel I always found spotters helpful. Now that I have
experience, here are my two basic rules on spotters:
1. Use spotters you know, preferably people who drive
a rig like
yours, and set up as much the same as possible. I pretty much trust the
other drivers in my Cruiser club.
2. Someone said yesterday that they walk the
trail twice (terrain
then placement). I like to walk it up (its almost
always uphill -
harder obstacles, and I can't see over my hood), then walk it back down
with my spotter saying 'I want to put the tire here, or I want to
end
up here'. That way we have a game plan.
This is, of course, a nice, mannered discussion of the relative merits
of
spotters. You usually see a flaming row about
issues like this (and
clutches, and auto trannies, etc. etc.) but this still gets the point across
that there are different opinions out there.
So what do I think? I've gotten myself into some scrapes that
a spotter
could have helped me avoid. I have not yet gotten into a scrape because of
bad advice from a spotter, so on the whole
they seem like a useful
institution. That being said, however, I would still rather do without them.
I tend to be a solitary in my hobbies; I drive off in a random direction for
a couple weeks of rough camping, and my rig is really intended to get me to
and from potential camping/climbing spots, more so than it is just an outlet
for a rock-crawling addiction. I also feel that using spotters
frequently
might be habit-forming; and in a situation where there
is no spotter
available you might do a worse job of it because of your anxiety due to not
having your crutch. Still, when you're doing highly technical rock-crawling,
you don't have much choice but to use a spotter. I put it in the 'necessary
evil' category.
If I pull a bonehead move because of my poor judgement, and wreck my rig, I
have only myself to blame. I'm not sure I'd trust myself to be rational
if
someone else was responsible for the
destruction of the $300 water
separator on my 'Cruiser.
From my point of view, my rig is my transportation. If I have to walk
the
trail twice to be able to run my rig over it, then it isn't transportation
at all, rather it is a chore; it's costing me more work than it's saving.
Your mileage may differ.
Pardon me while I install the Halon cylinder next to my e-mail basket...
15 Obstacles
15.1 A note
regarding obstacles
If you take nothing else away with you from this FAQ, take
this:
"There is no more dangerous obstacle than the obstacle
unseen."
Driving through long grass should be done slowly. Driving
through very
long grass should be done very slowly.
Any time you can't see what you're driving on is a good time to drive slow.
Through water, mud, grass, willow, reeds, etc.
Water could hide a rock, a sharp stick, a broken bottle, anything.
I know a person who once grazed a fire hydrant in long grass. It
turned
out a company had started building a subdivision, but lost their funding, so
there were fire hydrants and curbs, but nothing else, and it had all
grown
over. There could be an old lean-to, or a junked VW sitting in
that long
grass. You could hit a young deer, or other animal. Until you've
explored
the territory, go slow.
15.2 Steep Climbs
The natural reaction of the inexperienced faced with
a steep hill, or a
not-so-steep, but slippery hill to climb is to put the truck in granny
low
and stomp on the gas. This, is not the way to do it.
There are two forces that can get you over a hill: momentum, and friction.
For small hills and bumps, you can safely rely on momentum to get you over,
but for anything steep and bigger than 10 or 15 feet, you have to rely
at
least partially on friction.
You need to have the truck in as high a gear as possible in order to reduce
the chances of the wheels spinning. In granny-low, you'll just spin out and
slide down (unless you can idle up the hill). Try the hill first
in your
middle gear (2nd for 3-speeds, 3 for 5-speeds) and see what happens.
If you do start to spin out, ease off the throttle,
and hopefully the
wheels will grab again. If the wheels don't grab
again, then hit the
brakes and clutch to hold yourself steady, shift into reverse, and let go of
all pedals. Let the engine do the braking. DON'T
use the brakes going
down a hill, or you will likely lose static friction and you might
start
sliding down, turn sideways, and roll. That is a very-bad-case scenario, but
it has happened. If you didn't make it up, try again in a higher gear.
Do not try to change gears on a steep hill.
Short steep hills can be mentally unsettling, because you lose track of the
ground. All you can see over your hood is sky. You must
pick your line
before you start the climb, and hope you stay on it.
You should start climbs head-on, so that both wheels start
climbing at
once. This dramatically reduces the chance of a roll. Sometimes,
however,
you just can't start head on, because your
approach angle isn't great
enough. In these cases you should approach the hill at a 45 degree angle or
so (more if necessary) and as soon as the tire closer to the hill
has a
bite on it, crank the wheels into the hill so that you will turn up the hill.
You want to avoid having one side of the vehicle higher than the other.
You should avoid backing up a steep hill. It puts a lot of stress
on the
front axle, and specifically the birfield joints (found in Land
Cruisers,
etc.). It's not too hard to break a birfield backing up a steep hill if you
goose the throttle, especially if you have a front locker, and then
you're
stuck. If you must back up a steep hill, do it smoothly.
15.3 Steep Decents
These can be easy or hard.
The rule against using brakes on a decent
applies here. Use compression braking only. If the surface
is firm, just
steep, then select granny low, and go down. Don't touch those
brakes if
you can help it. If you must, then keep the clutch engaged,
that way you
can't lock the wheels. If the surface isn't firm, then the selection
of a
gear becomes more tricky. Too low a gear might not let the wheels turn fast
enough to maintain static friction, but too
high a gear will have you
careening down the hill faster than you want to go. Your best bet
usually
(experience will teach) is to go with granny low, and keep your mitt on the
hand throttle. If you start to skid forward, yard on the hand
throttle to
increase wheel speed and regain traction. If you don't have a hand throttle
then be very careful with the gas pedal, as you don't want
your foot to
bounce into the gas and get you going faster than prudence dictates.
Don't
try to change gears going down a hill. If the situation
starts looking
grim half way down a hill, and you just can't keep the
wheels spinning
fast enough to maintain static friction, then
you may have to use the
clutch. If there is open space at the bottom of the hill (so
you're not
going to smack a tree or something) then pushing the clutch
won't cause
you much grief if the surface is relatively smooth.
Remember, though,
that high speeds on rough surfaces are dangerous, and the vibration
will
cause the whole world to blur at the edges, and you won't be able to
tell
where you're going. If you lose your line down the hill, you
might hit a
bump, the wheels might bounce to one side, the truck could end up
turning
sharply, and you could roll down the hill. Slow is
better. The general
rule with hills is "Straight up, and straight down." Turning
on a hill is
to be avoided where possible.
15.4 Stalling on a
Steep Grade
This is a definite hassle. It never occurred to me
to put this section in,
being blessed with an injected diesel that will run upside down if I want it
do, but some carburetors don't like steep grades, and may very well stall on
longer ones. Here's what to do.
[From the nimble fingers of Guy Hammer comes:]
Allright, I have a manual transmission, power brakes, and
my carb
likes to flood out on steep angles. I'm perched way up on
the side
of this hill with both feet occupied with clutch and brake, and
the
engine is dead. NOW WHAT??!
Number one priority is not to lose the power assist
in the brakes
at this point. Do NOT pump or release the
brakes. If you do, and
exhaust the reserve capacity of the power booster you won't be
able
to hold your rig from rolling back even if you use
both feet! The
parking brake won't hold it either!
[Ed. note: Guy is about to get into a
discussion about how to
coerce a sticky gearbox into shifting into reverse. Most
gearboxes
aren't going to need this kind of
treatment, but you should try
shutting off your truck on a SMALL hill to simulate
this stalled-
climb situation and see if yours is the sticky kind (like a
T18).]
Number two priority is to get the trans in reverse. If it
won't go
just keep stirring the stick between various
forward gears and
reverse until you get it to drop in. If that doesn't work,
release
the clutch (NOT the brake) and bump the starter while
pulling it
into reverse. Once in reverse NOW you can
release the brake. If
your rig doesn't have low enough gears to hold you on the
hill, at
least the engine turning will help rebuild vacuum
in the brake
booster. If the gears DO hold you, hit the starter and back on
down
the hill. At this point if the engine restarts, fine,
just let it
idle you down.
If you get crossed up backing down the hill you may have no
choice
but to try and re-start the engine and try to pull
forward a bit.
Stop the rig by releasing the starter (or with
the brakes if the
gears won't hold it. BE CAREFUL with the brakes!)
With the clutch
and brakes applied, shift into whatever forward gear works best
for
climbing in your rig. At this point it's useful to know the
"racers
three-step". Left foot on clutch, right
toe on brake, right heel
mashing gas. (on my rig anyway.) If you can get
the engine to
catch, that's half the battle. Rev it
a few times to clear the
flooding as much as possible, and then simultaneously
release the
brake and clutch, mash the gas, cross your fingers and
hold your
breath. (might want to practice this before you get caught on
Lions
Back ;) With luck this might buy you a few feet or even get
you on
up and over the hill.
[Here endeth the lesson.]
Basically what you're doing is letting the compression of
your stalled
engine act as a brake to slow your journey down the hill. Because the engine
is physically being turned over (though it isn't actually running) you will
get some power back in your brakes (because the pump is running).
You can
now use your brakes to slow your descent.
The second-to-last-ditch attempt thing to try is to leave
your truck in
first gear, ignore the brakes, and use the clutch as a brake. There
is a
built-in psychological aspect to this, because you're used to pushing in the
clutch to stop, and in this case you need to let go of the
clutch to
stop. Irritating little problem. As long as you are in 4WD
you will have
four wheel braking using this method, so it will hold you on the
hill, as
long as there is traction. Hard on the clutch, though.
If you are 10 feet away from the crest of the hill then you might want
to
try the absolute-last-ditch thing, and that is to put the truck in first gear
and let the starter drive you up the hill. This isn't inordinately hard
on
the starter as long as you don't run it for longer than 10 or 15 seconds at a
time. When the 10-15 seconds is up, just shut off the key and the
engine
will hold the truck steady (because you're not touching the clutch
or the
brakes). After you give the starter a good 5 minutes to cool, then
do it
again. Sooner or later either your battery will be dead, or you'll be at the
top of the hill. This only works on an oldish truck that doesn't
have an
interlock that keeps you from working the starter with the truck in gear.
It has been suggested to me that you shouldn't get out of your truck on a
steep grade unless your seatbelts are of the type that can be
pulled out
again on a grade (many lock on a grade, and once it retracts you can't pull
it out again until the truck is on level ground). Land
Cruisers of my
vintage suffer this 'feature', and it's a pain. The best you can
do is to
try to use something like the vise grips from the toolbox (if you can reach
it with your belt on) to keep the belt from retracting when you take it off.
15.5 Water Crossings
This section has been replaced
by an article by Runar Sigurjonsson
(apologies for the lack of punctuation). The article was written by him, but
it was heavily edited by myself as English is not Runar's first
language.
Anything in square brackets is an addition by myself.
This is the way we cross the glacial rivers [in Iceland]
and maybe
this does not fit into what you were thinking about. Those
glacial
rivers change regularly, they can be passable
in the morning but
not in the afternoon [due to meltwater,
caused by the sun], but
then maybe in a different place.....:-(
Crossing rivers.
Rivers and your truck:
Water is one of your truck's biggest enemies.
If water gets into
a gasoline engine, it will be greatly damaged. If water
gets into
a Diesel engine it will be destroyed. The two most
important parts
to protect are the air-intake and the electronic
ignition system.
The ignition system in newer vehicles is
usually very tight and
need not be worried about. In older vehicles it can
help to spray
some water-repelling sprays, but they often make the
ignition very
dirty.
The air-intake is the route water can get
into your engine. If
that happens, you are in deep [trouble]. If you are lucky
you only
need to dry your engine, if not, start looking
for a new engine.
In newer vehicles the air is usually fed in from two places,
inside
the front fender and from around the exhaust-pipes.
The fender is
well protected from splashes but if you drive to fast
the vehicle
will make a wave in front and raise the water level inside
the
fender.
The best place for a air-intake is on the roof or feeding
the air
through the firewall from inside the truck.
The weight of your truck has big
effect on its river crossing
abilities and the height up under the body also.
As soon as the
body goes into the water the weight that is sitting on the tires
is
greatly reduced, making it easier
for the current to push the
vehicle its way. For example if your vehicle
weighs 3300 pounds
and the body-tub is 7x5 feet and it sinks one foot into
water the
weight on the tires is reduced to only
1220 pounds [assuming no
leakage of water into the tub].
No precautions need to be taken for the exhaust
system, there is
no way water can get past the exhaust [as
long as the engine is
running].
Where to cross:
In general it is best to cross where
the river is wide and has
adequate current. Adequate current means that it is not as
deep as
where there is less current, and it also means that
the bottom is
more solid. [ If the river is a consistent 13 feet across,
and one
area has a faster current than another area, then that
area with
the faster current is shallower.]
The current carries with it mud and sand that it puts
down where
the current drops and that makes the bottom soft and dangerous.
Never cross in a place that
cannot be waded. If the place is
unknown to the driver he should examine it by wading over
himself.
He needs to check how deep it is, how fast the current is,
and how
[firm] the bottom is. To wade in a safe manner
the person should
have a stick (the heavier the better) and
face up the river,
leaning on the stick, with slightly bent knees |
Onboard
Air
