Dynamometer Details

Description of the Milwaukee Road Dynamometer X-5000 Car

By W.R. Newhauser, Test Dept., Milwaukee Shops, 7/4/72

I. Introduction

Dynamometer Car X-5000 was built to provide monitoring and recording facilities for road testing of rolling stock and track. Living facilities were provided to permit field operations for extended periods of time.

II. History

The Dynamometer Car was built in 1930 at Milwaukee and it’s original use was for evaluating performance of steam locomotives. The monitoring apparatus was limited to recording drawbar effort, train speed, and time-location events. Average drawbar could be determined by means of a mechanical integrator.

Many major car improvements have been made in recent years including a new electrical system, high-speed trucks, and improved car facilities.

In 1969 the existing instrumentation was replaced by a solid state data acquisition system. The monitoring and recording facilities were designed for maximum operational versatility.

III. Description of Dynamometer Car

The car has an inside length of 60 feet and weighs 77.6 tons. Electrical power is furnished by a 32 volt generator and a 115 vac alternator. Complete living facilities are provided for eight. The interior is divided into four principal areas:

  1. Kitchen – dining
  2. Sleeping
  3. Office
  4. Instrumentation

Central aisle arrangement provides easy access to any area. An FM train radio permits communication with train crews and local railroad operators.

IV. On-Board Instrumentation

Overview: The new data system is comprised principally of data sensors, signal conditioners, strip chart recorders (2), and data display devices. Input signals can be programmed for display and/or recording on permanent type chart rolls. All instrument components except remote sensors and train lines are located at one end of the car.

Operation: Sensors and transducers convert various phenomena such as speed, pressure, acceleration and drawbar effort into proportionate electrical signals which when conditioned are displayed by the recorders.

Recorders: Two (2) brush MK260 strip chart recorders are mounted side by side. Each has six (6) analog and four (4) event channels. Pressurized inking on all pens yields permanent recordings which are insensitive to light.

The chart drive of either or both recorders can operate in fixed (pre-selected) or variable (incremental) mode. A “chopper” drive was developed to provide chart drive as a function of train speed.

Data Display: Analog and digital display is provided by various indicators and readout devices mounted on a central panel. Gages, pilot lamps, time meters and counters provide continuous indication of signal status.

A small auxiliary meter panel provides analog display of high-potential voltage and current signals.

Scope of Application: The operational versatility of the data system permits field evaluation of a wide variety of railroad equipment and components. A partial listing of test applications includes:

Track Condition Evaluating mainline track
Freight Car Test Optimum spring arrangement
Stress in truck and car-body components
Truck stabilizing devices
Special Equipment Lading tie-downs
Truck anti-swivel device
Locomotive Tests Slug consists
Step-less throttle
Remote control
Electrical characteristics
Train Performance Speed
Grade performance
Fuel consumption
Drawbar & electrical horsepower
Dynamic & air brake application & effectiveness


Physical Configuration:
Data system basic components include the hydraulic drawbar apparatus, analog recorders (2), data display panel, signal conditioners, and data sensors. The system occupies 17 square feet of floor space.

Supporting subsystems such as high potential input are mounted on adjacent walls. The recorders and all electronic modules are shock-mounted to a tubular steel frame. The recorders are retracted downward and two hinged leaves form a desk top when recorders are not in operation.

Monitoring Capabilities: A partial listing of parameters which can be displayed an/or recorded includes train speed, drawbar effort, locomotive operational functions, input from remote sensors and transducers, and time-location event data. (See detailed listing.)

Data System Programming: An appropriate combination of performance parameters is selected according to the type of test-data required. One or both recorders can be used operating at similar or different chart speeds.

Typical operational functions monitored during road testing of locomotives include the following:

  1. Train speed
  2. Train location
  3. Drawbar pull/buff
  4. Throttle position
  5. Main gen. voltage
  6. Wheel slip
  7. Traction motor current
  8. Brake pipe pressure
  9. Brake cylinder pressure
  10. Dynamic brake
  11. Sanding
  12. Time base

Field evaluation of rolling stock or track components involves use of remote sensors and transducers such as strain gages and accelerometers. Typical dynamic functions recorded include stress, acceleration, and/or displacement of truck and car-body components as well as speed, location,
time, and event data.

Documentation: Chart recordings and supplementary field data are analyzed by test department personnel and published as managerial information for diagnosis, control, and planning.

IV. Advantages of Data System

The data system on the Dynamometer car offers distinct advantages resulting from its relatively simple and straight forward design:

Economic Benefits: Low initial and maintenance costs with minimum operating personnel requirements.

Operational Advantages: Simplified programming and ease of operation.

Technical Merits: High sensitivity, accuracy, and repeatability. Simultaneous data display and recording is optional. The combination of analog recording and incremental chart drive provides data signals traceable to any point in time or location. The permanent type chart recordings are instantly available and can be analyzed without computer processing.

V. Dynamometer Car Operational Policy

Responsibility for the on-board data system has been placed with the test department. Day to day activities involving field operations, maintenance, test preparations and data reduction are supervised by the Dynamometer car engineer.

A policy of continuing improvement of the X-5000 has these primary objectives:

  1. Providing more complete managerial information
  2. Upgrading the data system and
  3. Improving car facilities and equipment