190302 B

Question 1

What are the 5 functions of Off Road suspension systems?

Answer 1

Load Carrying Capacity
Absorb and Transmit Torque Loads
Provide operator comfort
Centre the driveline
Maintain ground contact

Question 2

What was the hitch connection point on older scrapers called?

Answer 2

Stiffneck, due to no cushion hitch

Question 3

What positions are available to an operator of a push pull type scraper for cushion hitch?

Answer 3

Bail Down with No Cushion
Bail Up with No Cushion
Cushion Ride

Question 4

An operator complains that his machine has been shut off for some time, but the cushion hitch has not drained down. Why?

Answer 4

The valve stem on the accumulator is broken

Question 5

What type of unit would use a rubber block suspension, and where would it be mounted?

Answer 5

Articulated haul trucks, located on the top of the drive axle

Question 6

What 2 things do A Frames provide on an articulated haul truck suspension system?

Answer 6

Vertical Dampening and Longitudinal support

Question 7

What occurs on rubber block suspension when it is being used loaded and unloaded?

Answer 7

The rubber block will get stiffer during high loads and softer during light loads

Question 8

How does Hydrair Suspension control the rebound rate?

Answer 8

There is a metered orifice and a checkball that allow fluid in during compression, then the fluid returns only through the orifice

Question 9

What can happen over time on chromed rods inside the suspension cylinders?

Answer 9

The wiper seal will slowly destroy the chromed finish

Question 10

What are 5 reasons to perform service on a suspension cylinder?

Answer 10

1. Electronic Fault Code
2. Poor Chromed Rod Condition
3. Leaking cylinder or nitrogen charge
4. Hard ride conditions
5. Rod fully extended when unit unloaded

Question 11

When measuring front suspension cylinders, what size shims are used for what temperature difference? Celsius and Fahrenheit

Answer 11

4mm shim for every 5.5 Degrees Celsius difference
0. 25” Shim for every 10 Degree Fahrenheit difference

Question 12

On a large haul truck, if the pan hard rod bushings are wearing, where would the wear also show up? Why?

Answer 12

In the wheel bearings due to the full floating axle.

Question 13

How do servo valves control the pressure within the hydraulic pump?

Answer 13

Spring pressure is overcome when pressure is past limits, allowing the pressure within the system to go through the spool valve and act on the swash plate, until the angle is equaled to the spring pressure.

Question 14

What is a good way to test for problems within the hydraulic system?

Answer 14

Pull the in tank filter out, and use a magnet to check for ferrous particles.

Question 15

What test is performed to determine pump condition?

Answer 15

A flow loss test.

Question 16

What is the formula for a flow loss test?

Answer 16

Gpm @ 100 PSI - Gpm @ 1000PSI DIVIDED BY Gpm @ 100 PSI
X 100 = Percent of Flow Lost

Question 17

When refilling accumulators, what type of gas cylinder and fittings should be used?

Answer 17

Dry nitrogen gas in a certified Gas Association cylinder, with 580 fittings

Question 18

What size gauge would typically be used to measure the pressure within a nitrogen filled suspension cylinder?

Answer 18

2000 PSI

Question 19

On a cushion hitch, what is the rod end, and the cylinder end attached to?

Answer 19

The rod end is attached to the Scraper Hitch Assembly

The cylinder end is attached to the Tractor Bracket

Question 20

What distance of hauling is a motor scraper intended for?

Answer 20

100-1000 Metres

Question 21

How is a load cylinder for a cushion hitch attached to a motor scraper?

Answer 21

The lower end of the cylinder is pinned to the tractor bracket portion and the Rod end is pinned to the scraper hitch bracket.

Question 22

What distance are articulated haul trucks intended for?

Answer 22

300-2000 Metre distances

Question 23

What is a pan hard rod used for?

Answer 23

This is used for keeping the drive axle centered accurately