Udor RNK 122 Reduction Gearbox — 40 HP Industrial Duty

The Udor RNK 122 is an industrial-duty reduction gearbox designed to couple petrol or diesel engines to Udor NK, NKS and NH series high-pressure plunger pumps. Rated to 40 HP (30 kW), it provides a fixed 2.176:1 reduction ratio that allows the pump to run at optimal crankshaft speed while the engine operates at full RPM. Four variants cover two engine shaft diameters (1″ 1/8 and 1″ 7/16) in both solid-shaft and KH (hollow-shaft) configurations, giving specifiers full flexibility when matching engine output to pump input. As New Zealand’s sole authorised Udor distributor, AES Waterblasters supplies all RNK 122 variants and genuine Udor spare parts.

Specifications

Series	RNK (Industrial Duty Reduction)
Max Power	40 HP / 30 kW
Reduction Ratio	2.176 : 1
Pump Shaft	24 mm
Oil Type	SAE 85/140
Oil Quantity	0.45 L
Flange	SAE J609B
Compatible Pumps	Udor NK, NKS, NH Series

Model Variants

Model	Code	Engine Shaft	Type
RNK 122 1″ 1/8	5121G8	28.6 mm (1″ 1/8)	Solid Shaft
RNK 122 1″ 1/8 KH	5122G8	28.6 mm (1″ 1/8)	Hollow Shaft
RNK 122 1″ 7/16	5121G9	36.5 mm (1″ 7/16)	Solid Shaft
RNK 122 1″ 7/16 KH	5122G9	36.5 mm (1″ 7/16)	Hollow Shaft

Applications

• Engine-driven commercial and industrial pressure washing
• Truck-mounted and trailer-mounted water blasting systems
• Agricultural spray and wash-down equipment
• Drain and sewer jetting units
• Mining and construction wash-down
• Multi-gun fleet and vehicle cleaning rigs

Key Features

• 40 HP (30 kW) rated — suits mid-to-large petrol and diesel engines
• 2.176 : 1 fixed reduction ratio matches NK-class pump RPM requirements
• SAE J609B flange for standardised engine bell-housing mounting
• KH (hollow shaft) variants available for applications requiring pass-through drive
• Two engine shaft options (1″ 1/8 and 1″ 7/16) for broad engine compatibility
• Compact, oil-bath design with 0.45 L capacity using SAE 85/140 gear oil
• Hardened gear train for long service life under continuous industrial loads

Technical Documents

• Udor RNK 122 Gearbox Brochure (PDF)
• Udor RNK 122 Parts Schematic (PDF)
• All Udor Gearbox Documents

Parts & Service

AES Waterblasters is the sole New Zealand distributor for Udor products and carries genuine spare parts for all RNK 122 gearbox variants. Our workshop can service, rebuild, and supply replacement components including gears, bearings, seals, and housings. Contact us on 09 271 4782 for parts enquiries, pricing, or technical advice.

Related Models

Other Udor gearbox and pump ranges:

• Udor RH Series — Extra Heavy-Duty Reduction Gearbox (110 HP)
• Udor E127 — Electric Motor Reduction Gearbox
• Udor MTP 125 — PTO Multiplier Gearbox
• Udor NKD 7.0/75 R — Compatible NK Series Pump
• Udor NH-D 8.0/75 R — Compatible NH Series Pump