INDEX
1. Aims & Objectives ...... Page 1
2. Course Title ...... Page 2
3. Vehicle Knowledge ...... Pages 3 - 5
4. Preparation of Vehicle For Off Road Use ... Page 6
5. Basic Off Road Rules ...... Page 7
6. Assessing Off Road Conditions ...... Page 8
7. Traversing ...... Page 9
8. V Shaped Gullies ...... Page 10
9. Rough Tracks ...... Page 11
10. Rutted Tracks ...... Page 12
11. Ruts & Ditches, Small Obstacles ...... Page 13
12. Ridges & Large Ditches ...... Page 14
13. The Hill ...... Page 15
14. The Aborted Climb (Failed Hill Climb) ...... Pages 16 - 17
15. Sand & Mud (Soft Under Surface ) ...... Page 18
16. Water ...... Page 19
17. Ice & Snow ...... Page 20
OCHILS MOUNTAIN RESCUE TEAM OFF ROAD AWARENESS COURSE
AIM:
To prepare Members for the safe operation and competent driving of vehicles fitted with all wheel drive both on and off road.
COURSE TRAINING OBJECTIVE
At the end of the Assessment the candidate will be able to:
1. Demonstrate safe and competent driving of a vehicle fitted with all wheel drive on the road.
2. Demonstrate safe and competent driving of a vehicle fitted with all wheel drive in off road conditions.
3. Demonstrate full control of the vehicle under varied traffic and terrain conditions.
4. Demonstrate the correct method of application and use of diff-locks, high and low ranges and all wheel drive over various conditions.
5. Demonstrate an understanding of changing road and terrain conditions and the anticipation of changes requiring action.
6. Explain the duties of an all wheel drive vehicle driver and the responsibilities to colleagues and the public.
DURATION
TARGET POPULATION / MRT members who may be required to drive vehicles fitted with all wheel drive.
AIM / To prepare Members for the safe operation and competent driving of vehicles fitted with all wheel drive both on and off road.
OBJECTIVES / 1. Demonstrate safe and competent driving of a vehicle
fitted with all wheel drive on the road.
2. Demonstrate safe and competent driving of a vehicle
fitted with all wheel drive in off road conditions.
3. Demonstrate full control of the vehicle under varied
traffic and terrain conditions.
4. Demonstrate the correct method of application and use of
diff-locks, high and low ranges and all wheel drive over
various conditions.
5. Demonstrate a understanding of changing road and
terrain conditions and the anticipation of changes
requiring action.
6. Explain the duties of an all wheel drive vehicle driver and
the responsibilities to colleagues and the public.
CONTENT / Theoretical & practical operation of vehicle both on & off road.
METHOD / Lectures & practical driving.
INSTRUCTOR QUALIFICATIONS
VENUE / .
TIMES
EQUIPMENT REQUIRED
METHOD OF EVALUATION / Continual Assessment.
VEHICLE KNOWLEDGE
A BASIC TWO WHEEL DRIVE LAYOUT
TWO WHEEL DRIVE
With 2-wheel drive if one wheel starts spinning, drive will be lost because the differential allows the engines power to find the easy way out through the wheel with the least traction. The diff also allows one wheel to turn faster than the other when cornering.
A BASIC FOUR WHEEL DRIVE LAYOUT
PART TIME 4 WHEEL DRIVE
These vehicles are usually 2-wheel rear driven with a transfer gearbox, which transmits the drive to the front wheels. On some vehicles there may be a need to lock the free wheeling hubs to ensure drive to all wheels (i.e. the ford transit county).
PERMANENT 4 WHEEL DRIVE
With permanent 4-wheel drive, power is fed through the gearbox to the centre differential. This differential divides the power between the front and rear wheels in such a way it allows the front and rear wheels to rotate at a slightly different speeds when necessary i.e. manoeuvring at low speeds. If this did not happen the difference in rotational speeds between the front and rear wheels would impose sever strains on the transmission a condition known as WIND UP.
TRANSMISSION WIND UP
If a part time 4 wheel drive vehicle is left in 4-wheel drive on hard surfaces then when cornering the front wheels will travel at a different speed than the rear wheels. Since both front and rear wheels are interconnected through the transmission all drive shaft will wind up with torque, which cannot be released with the possibility of serious transmission damage occurring. Similarly when a front or rear diff is locked the axle becomes a solid bar and if any attempt is made to steer there is a possibility of damage occurring due to axle wind up i.e. the outside wheel wanting to travel further than the inner wheel, resulting in torque winding up within the axle which can not be released unless the surface allows the wheels to slip
DIFFERENTIAL LOCKS
Two additional differentials are required to make a four-wheel drive system work properly, one between the front wheels and one between the rear wheels. As on a 2 wheel drive system these differentials allow the wheels to turn faster than the others as happens when a car turns a corner.
With a permanent 4-wheel drive system the maximum number of wheels being driven would be 4 and the minimum 1, again the power would find the easiest way out through the wheel with the least traction. With this system there would need to be some means of locking the differentials, especially the centre and or all the drive would be lost with one wheel loosing traction.
On operation of the front or rear diff locks the rear or front axles would basically become a solid bar and any steering will cause one wheel to requiring to turn faster than the other. On soft ground steering would be lost and a bulldoze effect would be induced, on a hard surface with good traction then axle wind up would occur.
PREPARATION OF VEHICLE FOR OFF ROAD USE
When you take a vehicle off road it is recommended that the following checks be carried out:
· Fluid levels: Check they are at maximum because of slope angles (oils engine, transmission brake/clutch, water/radiator, and screen wash.
· Tyres: Correct pressures and in good condition.
· Spare Tyre: Correct pressure and located out of line of sight.
· Battery: Battery securely fixed and secure connections.
· Loose Equipment: All loose items securely fastened as they could become a flying object.
· Wing Mirrors Useful for all round visibility but fold back if likely to be pulled off by branches etc.
· Towing Bracket: Remove unless required (it decreases ground clearance).
· Vehicle Steps : Fold up (could be pulled off by ground contact).
· Aerials: Remove /retract if not required (they could be pulled off by branches).
· Clean Windows: You need to be able to see clearly all around.
BASIC OFF ROAD RULES
Before driving unknown ground - reconnoitre on foot.
Where necessary use one assistant / marshaller is in any doubt about wheel placement or ground clearance.
Centre differential lock normally engaged whenever you leave a hard road - consult the vehicle operator’s manual.
SPEED As slow as possible, as fast as necessary.
Generally the higher the gear the better (except when descending).
Hold the steering wheel with both hands and your thumbs outside (or you may bruise / break them even with power steering). Do not cross your hands.
Once committed either descending or ascending a hill DO NOT change gear.
Use the engine to brake vehicle.
Conserve yourself, your vehicle, your passengers and contents.
Know the gears for your vehicle - use the correct one and DO NOT use the clutch as a means of slowing too high a gear.
Stop for all transfer box changes unless you have learned to do it on the move without any clunks.
You have twice the traction of a two-wheel drive to get you going but you have the same braking as a two-wheel drive to stop you.
JACKING
The procedure to ensure safety when jacking a vehicle to remove a wheel:
remove all passengers.
remove spare wheel before jacking.
Ensure safety by restricting vehicle movement:
chock wheels
understand the limitations of handbrakes / parking brakes and differential locks/viscous coupling combinations.
ASSESSING OFF ROAD CONDITIONS
TRAVERSING
This is the most dangerous and difficult manoeuvre to execute.
IF at all possible AVOID especially in the wet.
If there is absolutely no choice - take your time:
1. RECONNOITRE
Check slope
look for ruts, sheep tracks, etc.
note potholes and rocks, etc.
2. Remove passengers
3. Check vehicle loading
4. Proceed very slowly
If vehicle starts to roll or becomes unstable, STEER DOWNHILL and gets as square as possible.
EVERY TIME, THINK! THINK! THINK!
type of surface
load in vehicle
Gradient of slope
weather conditions
These will all have an effect on the stability and performance of the vehicle.
IF IN DOUBT BOTTLE OUT
‘V’ SHAPED GULLIES
Execute extreme caution; it is very easy to tip the vehicle on its side, very expensive to repair.
Drive so as to keep vehicle level at all costs. Do not steer up or down slope and correct the vehicle from doing so on its own.
If necessary, cut ‘steps’ or wheel tracks in side of gully with a shovel to prevent wheels sliding down the slope.
ROUGH TRACKS
It is advisable to select four-wheel drive and differential lock. this is because if there is excessive suspension movement it may induce wheel spin.
· Be aware of your passenger’s comfort.
· Use low range if necessary to preserve vehicle, comfort and load.
It is often best to approach rocks, etc. by running a pair of wheels (front and back) directly over them rather than straddling them, thus avoiding contact with the underside of the vehicle.
RUTTED TRACKS
If possible, straddle ruts to maintain ground clearance. If this is not possible or practicable, then walk route and clear debris.
Use highest gear possible: 2nd or 3rd low and avoid gear changing. Maintain a steady speed.
Keep steering to a minimum and allow the vehicle a little freedom and permit some self-centring but keep a visual check. There is a tendency to over steer, which should be avoided, or the vehicle could be thrown out of the ruts once traction is gained.
You need to be aware of your wheel alignment (the vehicle will go straight even on full lock if the ruts are deep or slippery, until it climbs out!). To check alignment, either look out of the window and check or move the steering full left lock, then full right lock counting the number of turns taken, then back half the number of turns (the centre point to the two) and the wheels should be correctly aligned.
Remember the importance of maintaining ground clearance, do not ground the axles, they are very expensive .
RUTS AND DITCHES, SMALL OBSTACLES
1. Vehicles without axle differential locks or Limited Slip
Differentials (L.S.D.s)
· One wheel only to enter rut or ditch. The other three provide the traction to succeed in the manoeuvre.
· Normally first low (depending upon conditions).
· Watch front bumper on opposite site of the rut.
· Steady throttle to prevent wheel spin.
· Anticipate vehicle sliding side wards and be ready to counter.
Note : Reconnoitre the ditch first: if it is too large you may end up with two wheels in at once (e.g. front near side and rear offside). When diagonally opposite wheels lift off the ground, traction is normally lost, this is called cross-axle. The result is you are stuck!, Get the spade out!
2. Vehicles with axle differential locks and / or L.S.D.s
· Engage all differential locks in the correct order (vehicle manual).
· Proceed as above, but cross-axle situations will not be a problem.
Obstacles such as tree stumps and rocks are often best approached by running a pair of wheels (e.g. N/S front and N/S back) directly over them rather than straddling them to avoid contact with the underside of the vehicle .
RIDGES AND LARGER DITCHES
Providing no parts of the vehicle contact the ground, these can often be treated as a small hill.
Always approach at right angles (square on) so that both front wheels and then both rear wheels cross together to ensure maximum traction / braking.
If any part of the vehicle will contact the ground, then treat these obstacles the same as the smaller obstacles as in the previous section and be aware of cross-axle situations, where applicable (unless the vehicle is fitted with axle differential locks, LSDs).
THE HILL
Climbing
· As square as possible to the hill.
· Climb in highest gear possible.
· Lose momentum on the crest - then STOP.
Descending
· As square as possible to the slope.
· First low (normally). NO brake or clutch - let the engine do the braking.
· ON a long slope you may need to accelerate if the wheels lock.
· DO NOT turn while descending.