The Impact Hammer

1
The Impact Hammer

• Brian Shih
• 9.24.03

2
Overview

• Purpose
• History
• Design
• Calculations
• Initial Attempt
• Revision
• Other
• Error
• The Impact

3
Purpose

• Takes a steady flow of air and drives a piston
  forward and backwards, hitting an attached chisel
  or hammer which then strikes a desired material
  very rapidly.
• Advantages
• Speed
• Force
• Efficiency

4
History

• Charles B. King
• Patent No. 513,941
• Patented Jan. 30, 1894
• Pneumatic Tools Reciprocating Motors

5
Design Overview

• Air enters valve
• Pressure difference causes air to push piston
• Piston accelerates until it covers side exhaust
  holes
• Piston moves until air coming through front hole
  forces it back

6
Calculations - Assumptions

• The tube is frictionless
• The air accelerating the piston backwards does
  not cause the piston to decelerate before hitting
  the chisel
• The exhaust holes are exactly half the distance
  of the tube

7
Calculations Initial Attempt

• Target 3800 blows/min
• Air Intake 90 pounds/sq. inch
• Assumed constant acceleration through entire tube
• a 3083.23 m/s2
• Time for one stroke .01418 s
• BPM 4231.42

8
Calculations - Revision

• Assumed exhaust holes are half the length of
  tube, causing acceleration to stop.
• Time _at_ exhaust .005013 s
• v _at_ exhaust hole 15.457 m/s
• Time from exhaust to end .002507 s
• Total stroke time .015039 s
• BPM 3989.56

9
Calculations - Other

• Force output 169.578 N
• mm3/s air 1.827 x 106
• Actual air consumption 1.510 x 106 mm3/s
• Assumptions
• Tube is perfectly round cylinder with no
  indentation
• Piston is perfectly round cylinder with no
  chamfer or cuts

10
Error

• error for BPM 4.988
• error for airflow 20.993
• Causes
• BPM
• Force lost due to friction
• Air reaching far exhaust hole before piston,
  causing deceleration
• Airflow
• Overestimated volume caused by cylindrical
  assumption

11
The Impact (of this assignment)

• Airflow concepts
• Efficient part design
• Solidworks usage
• Acknowledgements
• Dan Rice BPM calculations
• www.uspto.gov patent search