Broomwade WR175 Air Compressor Design Legacy and Parts Restoration Strategy

[MikePhua]

The WR175 and Broomwade’s Industrial Air Heritage
The Broomwade WR175 air compressor represents a chapter in British industrial engineering that dates back to the early 20th century. Broomwade, founded in 1898, became a prominent manufacturer of reciprocating and rotary air compressors, serving sectors from mining to manufacturing. By 1919, the company had launched its first production compressor, and by the 1960s, it had merged with Holman to form International Air Corporation—later known as CompAir.
The WR series, including the WR160 and WR175, was designed for robust stationary use, often found in workshops, quarries, and municipal service yards. These machines were known for their cast-iron construction, oil-lubricated cylinders, and mechanical simplicity. Though production ceased decades ago, many WR175 units remain in service today, a testament to their durability and rebuildability.
Core Specifications and Mechanical Layout
While exact specifications vary slightly by production year, the WR175 typically features:

• Type: Two-stage reciprocating compressor
  
• Drive: Belt-driven via electric motor or diesel engine
  
• Cooling: Air-cooled with finned cylinders and inter-stage coolers
  
• Lubrication: Splash or pressure-fed oil system
  
• Operating pressure: ~175 psi (12 bar)
  
• Output capacity: ~17–20 cfm depending on RPM
  
• Flywheel diameter: ~18–22 inches
  
• Cylinder bore: ~3.5 inches (low stage), ~2.25 inches (high stage)
  

The compressor uses a crankshaft-driven piston arrangement with inter-stage cooling to reduce thermal stress and improve volumetric efficiency. The WR175’s cast iron crankcase and cylinder heads were machined to tight tolerances, allowing long service intervals when properly maintained.
In one restoration project in Alberta, a WR175 was pulled from a decommissioned rail yard and rebuilt using salvaged WR160 parts. The technician noted that the cylinder heads and valve plates were interchangeable, with minor gasket modifications.
Parts Availability and Cross-Model Compatibility
Due to the age of the WR175, original parts manuals are rare. However, many components are shared with the WR160 and WR200 models, allowing for cross-compatibility in rebuilds. Common interchangeable parts include:

• Valve plates and reed valves
  
• Piston rings and wrist pins
  
• Connecting rods and crankshaft bearings
  
• Oil seals and gaskets
  
• Air filters and intake silencers
  
• Pressure relief valves and drain cocks
  

Recommended sourcing strategy:

• Identify casting numbers on heads and crankcase
  
• Compare dimensions with WR160 parts catalog
  
• Use digital calipers to verify bore and stroke
  
• Contact legacy suppliers or CompAir distributors for cross-reference
  

A technician in France used a WR160 manual to rebuild a WR175, noting that the valve plate bolt pattern and head gasket dimensions matched perfectly. He fabricated a new oil sight glass using acrylic and a brass bezel, restoring full function.
Restoration Techniques and Workshop Tips
Restoring a WR175 requires attention to mechanical integrity and air sealing. Key steps include:

• Disassemble and inspect all moving parts
  
• Clean carbon deposits from valve plates and heads
  
• Hone cylinders to remove glazing and restore oil retention
  
• Replace all gaskets with high-temperature fiber or copper
  
• Check crankshaft end play and bearing clearance
  
• Rewire motor or replace with modern equivalent if needed
  

Recommended tools:

• Torque wrench (for head bolts and valve plate screws)
  
• Cylinder hone (flex-hone or ball hone)
  
• Feeler gauges (for valve clearance)
  
• Thread chaser (for restoring bolt holes)
  
• Oil pressure tester (if pressure-fed system)
  

In one rebuild in Maine, a technician used a vintage lathe to machine new piston rings from cast iron stock. The compressor ran smoothly after break-in and was used to power a sandblasting cabinet for antique tractor restoration.
Lubrication and Cooling Considerations
The WR175 relies on consistent lubrication to prevent piston seizure and bearing wear. Depending on configuration, it may use:

• Splash lubrication via crankcase oil
  
• Pressure-fed system with external pump
  
• SAE 30 or SAE 40 non-detergent compressor oil
  

Cooling is achieved through:

• Finned cylinder heads and barrels
  
• Inter-stage cooler pipe with heat-dissipating fins
  
• Ambient airflow or optional fan shroud
  

Maintenance tips:

• Change oil every 500 hours or annually
  
• Clean fins with compressed air monthly
  
• Inspect drain valves for moisture and rust
  
• Use synthetic oil in high-humidity environments
  

In one workshop in Queensland, a WR175 was retrofitted with a thermostatic fan and digital temperature sensor. This reduced head temperature by 15°C during summer operation and extended valve life.
Historical Significance and Collector Interest
The WR175 is increasingly sought after by collectors and restoration enthusiasts. Its mechanical simplicity, cast iron construction, and distinctive flywheel design make it a centerpiece in vintage tool collections. Some units are displayed in museums or used in demonstrations at agricultural fairs.
In 2022, a restored WR175 sold at auction in the UK for £2,800, complete with brass fittings and a polished flywheel. The buyer planned to use it in a heritage blacksmith shop alongside a belt-driven drill press and forge blower.
Conclusion
The Broomwade WR175 air compressor remains a symbol of industrial craftsmanship and mechanical resilience. Though parts manuals are scarce, its legacy lives on through shared components, restoration ingenuity, and a global network of enthusiasts. Whether powering tools or standing as a historical artifact, the WR175 continues to compress air—and admiration—with every stroke.