Crawler Tractors And Dozers

Question 1

Where in bc are dozers most efficient?

Answer 1

In the interior. Excavators replaced them on the coast due to steepness and unfavourable terrain.

Question 2

What are some features of tractors?

Answer 2

• rubber-tired dozers and crawler (tracks) dozers are available but don’t get used in the woods (high ground pressure and poor traction)
• Crawlers have excellent traction and low ground pressure (6 to 9 psi)
• Well suited for use in rough terrain (forestry work)
• Low-ground-pressure models with extra-wide tracks are available (3 psi )

Question 3

What attachments are available for tractors?

Answer 3

– Brush rakes

– plows, rippers

– Scarifiers for site preparation

– Winches and arches for logs

– Grade Control Systems

• used to tow compactors, scrapers

Question 4

Why are grade control systems so efficient?

Answer 4

Removes operator error by linking vertical blade position to site plan wirelessly. Blade automatically adjusts to proper position as tractor moves through space.

Question 5

What factors effect productivity?

Answer 5

1. Size and power of machine
2. Blade type and capacity
3. Distance to move material
4. Gradient to move material
5. Type of material
6. Ground conditions (moisture)
7. GPS Blade Controls (not used in forestry – yet!)

Question 6

How are tractors classified?

Answer 6

Grouped by engine horsepower and operating weight

• D6 Class: 165 hp, 39,000 lbs
• D8 Class: 285 hp, 81,300 lbs

Question 7

How does size and power effect machine function

Answer 7

Light machines effective on soft ground where floatation is more important than power

• Heavy machines for major earthmoving projects on dry soils
• Power to ground ~function of: weight, power, traction (bearing area)
• Track bearing area ~ function of: track length and width

Question 8

What are grousers ?

Answer 8

Blades on tracks that increase traction. Bigger for machines that require more traction.

Question 9

What is the most common forestry blade?

Answer 9

Angle Blade

• Left or right of center up to 25°
• Works well cutting side slopes and side casting
• Doesn’t carry materials as well as other blades because it is flat

Question 10

Best application for dozers?

Answer 10

• Build subgrade on dry ground with slopes

Question 11

How is production quantified?

Answer 11

• Production = Volume per cycle x Cycles per hour
• “volume per cycle” = average volume of material moved per equipment cycle
• nominal capacity of the dozer is modified by an appropriate fill factor based on the type of material

Question 12

How do you measure blade load assuming the machine has created a nice even full load pile?

Answer 12

Blade load (LCM)=0.375 x H (m) x W (m) x L (m)

Question 13

What is a dozer?

Answer 13

• A dozer is a tractor equipped with a front- mounted earthmoving blade
• It moves earth by lowering the blade and cutting until the blade is full
• pushes the material across the ground surface to the required location
• unloaded by: pushing it over a bank, into a hopper or raising the blade to form a pile