Duff Norton CMJ Series Air Motor Jacks
20 to 100 Tons of Air-Powered, Fail-Safe Lifting
Duff Norton CMJ air motor jacks are the industry standard for railroad car lifting, steel mill maintenance, and heavy industrial jacking operations where safety and reliability are non-negotiable. Built on the time-tested screw principle with an integral rotary air motor and gear train, these jacks raise and lower loads under full pneumatic control — the load speed is always governed by the motor, not gravity. If the air supply is interrupted, the load stays exactly where it is. No drop. No drift. No compromise.
Seven models span capacities from 20 tons to 100 tons, with stroke lengths ranging from 13-3/4 inches to 30 inches. Every model is manufactured in compliance with ASME B30.1 and rolls on 10-inch solid rubber-tire roller-bearing wheels for easy positioning around the shop floor or service yard. A fold-down transport handle and collapsible spotting handles make moving even the 530-pound 144CMJ manageable for a single operator.
Air-Fail-Safe by Design
The defining feature of every Duff Norton CMJ jack is its inherent safety under air loss. The screw mechanism is self-locking — if the air hose disconnects or the compressor shuts down, the jack holds the load in position without any operator intervention. The 50-ton and 100-ton models add a mechanical brake for an additional layer of security. Up/down directional control is through a simple hand throttle with a clear indicator, and automatic shut-off stops the motor at the safe limit of travel in either direction.
For multi-point lifts, CMJ jacks can be synchronized through a simple Y-valve connection — enabling level lifting of entire railcars, locomotive frames, or heavy assemblies with two, four, or more jacks operating simultaneously.
Model Specifications
| Model | Lifting Capacity | Sustaining Capacity | Closed Height | Stroke | Weight | CFM Required |
|---|---|---|---|---|---|---|
| 228R | 20 tons | 20 tons | 28″ | 18″ | 240 lbs | ~90 CFM |
| 326R | 35 tons | 35 tons | 26″ | 14-3/8″ | 275 lbs | ~100 CFM |
| 528CMJ | 50 tons | 50 tons | 28″ | 17″ | 394 lbs | 120–170 CFM |
| 536CMJ | 50 tons | 50 tons | 36″ | 25″ | 425 lbs | 120–170 CFM |
| 126CMJ | 75 tons lift / 100 tons sustain | 100 tons | 26″ | 13-3/4″ | 448 lbs | 155–200 CFM |
| 132CMJ | 75 tons lift / 100 tons sustain | 100 tons | 32″ | 18″ | 480 lbs | 155–200 CFM |
| 144CMJ | 75 tons lift / 100 tons sustain | 100 tons | 44″ | 30″ | 530 lbs | 155–200 CFM |
All models require 100 PSI dynamic air pressure at the valve entrance. Portable on wheels (all models).
Design Features
- ASME B30.1 compliant
- Rotary air motor with integral gear train
- Up/down hand throttle with directional indicator
- Automatic shut-off at safe travel limits
- Broad base with serrated forged steel top
- 10″ solid rubber-tire roller-bearing wheels
- Fold-down transport handle and collapsible spotting handles
- Built-in muffler and cleanable air screen
- Ball bearing thrust and radial mountings
- Easy lubrication through two plugs in jack plus one in air motor
New, Refurbished, and Trade-In
Calumet Chicago has been an authorized Duff Norton distributor and service center for over 30 years. We sell new CMJ jacks, offer certified refurbished units restored to OEM specifications, and accept trade-ins on existing jacks. Our factory-trained technicians perform complete rebuilds using certified parts, with multi-point load and sustained capacity testing before any jack leaves our shop. Every repair is backed by a 6-month warranty.
If you have a Duff Norton jack that needs service — or if you are looking at new or refurbished units — call us at (708) 474-2343 to discuss your needs.