A ripper is a heavy rear attachment on a bulldozer that tears hard ground before the dozer blade pushes it away. It is used when rock, frozen soil, or compacted layers are too strong to cut efficiently with the front blade alone. By breaking the ground into smaller fractured pieces, a ripper reduces the work needed for excavation, grading, and site preparation.
This makes construction faster, safer, and less dependent on blasting in many jobs.
Key Facts
- Drawbar power is approximately P = Fv, where F is pulling force and v is dozer speed.
- Stress at the ripper tip can be estimated by stress = F/A, where A is the contact area of the tooth.
- A smaller tooth contact area creates greater pressure on rock because pressure = F/A.
- Ripping is most effective at low speed because high traction force matters more than travel speed.
- Ripping depth depends on shank length, hydraulic force, ground strength, and traction.
- Several shallow passes can be more effective than one deep pass in very hard or layered ground.
Vocabulary
- Ripper shank
- A strong curved steel tooth mounted behind a dozer that penetrates and breaks hard ground.
- Ripper tip
- The replaceable pointed end of the shank that concentrates force into a small area.
- Drawbar pull
- The horizontal pulling force a tracked machine can apply to move or drag equipment through the ground.
- Traction
- The grip between the dozer tracks and the ground that lets engine power become pulling force.
- Fracture
- A crack or break that forms when stress in rock or soil exceeds its strength.
Common Mistakes to Avoid
- Treating the ripper like a rear plow is wrong because its main job is to fracture hard material, not to scoop or carry soil.
- Using too much speed is wrong because ripping depends on high force and traction, while speed can reduce control and increase wear.
- Setting the shank too deep on the first pass is wrong because the dozer may lose traction or stall before fractures can spread.
- Ignoring the tooth contact area is wrong because a sharp small tip creates much higher pressure than a worn broad tip for the same force.
Practice Questions
- 1 A dozer pulls a ripper with a force of 180,000 N at a speed of 0.80 m/s. Estimate the drawbar power using P = Fv.
- 2 A ripper tip presses on rock with a force of 120,000 N over a contact area of 0.006 m2. Calculate the pressure at the tip using pressure = F/A.
- 3 A crew can choose one deep ripping pass or three shallower passes through layered rock. Explain which choice is often better and why, using ideas of traction, fracture, and machine load.